Formation of Heterobimetallic Complexes by Addition of d10-Metal Ions to [(Me3P)xM(2-C6F4PPh2)2] (x = 1, 2; M = Ni and Pt): A Synthetic and Computational Study of Metallophilic Interactions.

Treatment of the bis(chelate) complexes trans-[M(κ2-2-C6F4PPh2)2] (trans-1M; M = Ni, Pt) and cis-[Pt(κ2-2-C6F4PPh2)2] (cis-1Pt) with equimolar amounts or excess of PMe3 solution gave complexes of the type [(Me3P)xM(2-C6F4PPh2)2] (x = 2: 2Ma, 2Mb x = 1: 3Ma, 3Mb; M = Ni, Pt). The reactivity of complexes of the type 2M and 3M toward monovalent coinage metal ions (M' = Cu, Ag, Au) was investigated next to the reaction of 1M toward [AuCl(PMe3)]. Four different complex types [(Me3P)2M(µ-2-C6F4PPh2)2M'Cl] (5MM'; M = Ni, Pt; M' = Cu, Ag, Au), [(Me3P)M(κ2-2-C6F4PPh2)(µ-2-C6F4PPh2)M'Cl]x (x = 1: 6MM'; M = Pt; M' = Cu, Au; x = 2: 6PtAg), head-to-tail-[(Me3P)ClM(µ-2-C6F4PPh2)2M'] (7MM'; M = Ni, Pt; M' = Au), and head-to-head-[(Me3P)ClM(µ-2-C6F4PPh2)2M'] (8MM'; M = Ni, Pt; M' = Cu, Ag, Au) were observed. Single-crystal X-ray analyses of complexes 5-8 revealed short metal-metal separations (2.7124(3)-3.3287(7) Å), suggestive of attractive metal-metal interactions. Quantum chemical calculations (atoms in molecules (AIM), electron localization function (ELF), non-covalent interaction (NCI), and natural bond orbital (NBO)) gave theoretical support that the interaction characteristics reach from a pure attractive non-covalent to an electron-shared (covalent) character.

Tin(IV) Compounds with 2-C6F4PPh2 Substituents and Their Reactivity toward Palladium(0): Formation of Tin-Palladium Complexes via Oxidative Addition.

The tin(IV) compounds MexSn(2-C6F4PPh2)4-x (1, x = 1; 2, x = 2) and ClSn(2-C6F4PPh2)3 (3) were obtained from the reactions of 2-LiC6F4PPh2 with MeSnCl3 (3:1), Me2SnCl2 (2:1), or SnCl4 (3:1), respectively. The reactions of 2-LiC6F4PPh2 with SnCl4 in different stoichiometric ratios (4:1-1:1) gave 3 as the main product. Compound Cl2Sn(2-C6F4PPh2)2 (4) was formed in the transmetalation reaction of 3 and [AuCl(tht)] but could not be isolated. 1 and 2 react with palladium(0) sources {[Pd(PPh3)4] and [Pd(allyl)Cp]} by the oxidative addition of one of their Sn-CAryl bonds to palladium(0) with formation of the heterobimetallic complexes [MeSn(µ-2-C6F4PPh2)2Pd(κC-2-C6F4PPh2)] (5) and [Me2Sn(µ-2-C6F4PPh2)Pd(κ2-2-C6F4PPh2)] (6) featuring Sn-Pd bonds. The reaction of 3 with palladium(0) proceeds via the oxidative addition of the Sn-Cl bond to palladium(0), thus furnishing the complex [Sn(µ-2-C6F4PPh2)3PdCl] (7) featuring a Sn-Pd bond and a pentacoordinate Pd atom. Transmetalation of MexSn(2-C6F4PPh2)4-x (x = 1-3) with [Pd(allyl)Cl]2 gave MexClSn(2-C6F4PPh2)3-x and [Pd(allyl)(µ-2-C6F4PPh2)]2. For x = 1, the compound MeClSn(2-C6F4PPh2)2 (generated in situ) reacted with another 1 equiv of [Pd(allyl)Cl]2 by the oxidative addition of the Sn-Cl bond to palladium(0) and the reductive elimination of allyl chloride, thus leading to [MeSn(µ-2-C6F4PPh2)2PdCl] (8). The reductive elimination of allyl chloride was also observed in the reaction of 3 with [Pd(allyl)Cl]2, giving [Sn(µ-2-C6F4PPh2)3PdCl] (7). All compounds have been characterized by means of multinuclear NMR spectroscopy, elemental analysis, single-crystal X-ray diffraction, and selected compounds by 119Sn Mössbauer spectroscopy. Computational analyses (natural localized molecular orbital calculations) have provided insight into the Sn-Pd bonding of 5-8.

Metallophilic Contacts in 2-C6F4PPh2 Bridged Heterobinuclear Complexes: A Crystallographic and Computational Study.

Treatment of the bis(chelate) complex trans-[Pd(κ(2)-2-C6F4PPh2)2] (7) with PMe3 gave trans-[Pd(κC-2-C6F4PPh2)2(PMe3)2] (13) as a mixture of syn- and anti-isomers. Reaction of 13 with CuCl, AgCl, or [AuCl(tht)] (tht = tetrahydrothiophene) gave the heterobinuclear complexes [(Me3P)2Pd(µ-2-C6F4PPh2)2MCl] [M = Cu (14), Ag (15), Au (16)], from which the corresponding salts [(Me3P)2Pd(µ-2-C6F4PPh2)2M]PF6 [M = Cu (17), Ag (18), Au (19)] could be prepared by abstraction of the chloro ligand with TlPF6; 18, as well as its triflato (20) and trifluoroacetato (21) analogues, were also prepared directly from 13 and the appropriate silver salt. Reaction of 13 with [AuCl(PMe3)] gave the zwitterionic complex [(Me3P)PdCl(µ-2-C6F4PPh2)2Au] (24) in which the 2-C6F4PPh2 ligands are in a head-to-head arrangement. In contrast, the analogous reaction with [AuCl(PPh3)] gave [(Ph3P)PdCl(µ-2-C6F4PPh2)2Au] (25) with a head-to-tail ligand arrangement. Single crystal X-ray diffraction studies of complexes 14-21 show short metal-metal separations [2.7707(11)-2.9423(3) Å] suggestive of attractive noncovalent (dispersion) interactions, a conclusion that is supported by theoretical calculations of the electron localization function and the noncovalent interactions descriptor.

Unprecedented near-infrared (NIR) emission in diplatinum(III) (d7-d7) complexes at room temperature.

The synthesis and single-crystal X-ray structures of the first family of efficient NIR emitters with tunable emission energy based on dihalodiplatinum(III) (5d(7)-5d(7)) complexes of general formulae [Pt(2)(mu-C(6)H(3)-5-R-2-AsPh(2))(4)X(2)] (R = Me or CHMe(2); X = Cl, Br or I), together with that of their diplatinum(II) (5d(8)-5d(8)) precursors ([Pt(2)(mu-C(6)H(3)-5-R-2-AsPh(2))(4)]) and cyano counterparts (X = CN), are reported. The diplatinum(II) complexes with isopropyl groups are isolated initially as a mixture of two species, one being a half-lantern structure containing two bridging and two chelate C(6)H(3)-5-CHMe(2)-2-AsPh(2) ligands (1b) that exists in two crystalline modifications [d(Pt...Pt) = 3.4298(2) A and 4.3843(2) A]; the other is a full-lantern or paddle-wheel structure having four bridging C(6)H(3)-5-CHMe(2)-2-AsPh(2) ligands (2b) [d(Pt...Pt) = 2.94795(12) A]. Complete conversion of the isomers into 2b occurs in hot toluene. The Pt-Pt bond distances in the diplatinum(III) complexes are less than that in 2b and increase in the order X = Cl (3b) [2.6896(2) A] < Br (4b) [2.7526(3) A] < I (5b) [2.7927(7) A] approximately CN (6b) [2.7823(2), 2.7924(2) A for two independent molecules]. Comparison with the corresponding data for our previously reported series of complexes 3a-6a (R = Me) indicates that the Pt-Pt bond lengths obtained from single-crystal X-ray analysis are influenced both by the axial ligand and by intermolecular lattice effects. Like [Pt(2)(mu-pop)(4)](4-) [pop = pyrophosphite, (P(2)O(5)H(2))(2-)], the diplatinum(II) complexes [Pt(2)(mu-C(6)H(3)-5-R-2-AsPh(2))(4)] [R = Me (2a), CHMe(2) (2b)] display intense green phosphorescence, both as solids and in solution, and at room temperature and 77 K, with the emission maxima in the range 501-532 nm. In contrast to the reported dihalodiplatinum(III) complexes [Pt(2)(mu-pop)(4)X(2)](4-) that exhibit red luminescence only at 77 K in a glass or as a solid, complexes 3a-6a and 3b-6b are phosphorescent in the visible to near-infrared region at both room and low temperatures. The electronic spectra and photoemissive behavior are discussed on the basis of time-dependent density functional theory (TDDFT) calculations at the B3YLP level. The photoemissive states for the halide analogues 3a,b-5a,b involve a moderate to extensive mixing of XMMCT character and MC [d sigma-d sigma*] character, whereas the cyano complexes 6a and 6b are thought to involve relatively less mixing of the XMMCT character into the MC [d sigma-d sigma*] state.

Electrochemical and chemical oxidation of [Pt2(mu-pyrophosphite)4]4- revisited: characterization of a nitrosyl derivative, [Pt2(mu-pyrophosphite)4(NO)]3-.

Electrochemical studies of the salts [cat](4)[Pt(2)(mu-pop)(4)] (cat(+) = Bu(4)N(+) or PPN(+) [Ph(3)P=N=PPh(3)](+); pop = pyrophosphite, [P(2)O(5)H(2)](2-)) have been carried out in dichloromethane. In agreement with published studies of K(4)[Pt(2)(mu-pop)(4)] in water and [Ph(4)As](4)[Pt(2)(mu-pop)(4)] in acetonitrile, the [Pt(2)(mu-pop)(4)](4-) anion is found to undergo an initial one-electron oxidation under conditions of cyclic voltammetry to a short-lived trianion, [Pt(2)(mu-pop)(4)](3-). However, in the more weakly coordinating solvent dichloromethane, [Pt(2)(mu-pop)(4)](3-) appears to undergo oligomerization instead of solvent-induced disproportionation; thus the overall process remains a one-electron reaction rather than an overall two-electron oxidative addition process, even under long time-scale, bulk electrolysis conditions. Chemical oxidation of [cat](4)[Pt(2)(mu-pop)(4)] with [NO][BF(4)] or AgBF(4) gives mainly a dark, insoluble, ill-defined solid that appears to contain Pt(III) according to X-ray photoelectron spectroscopy (XPS). In the case of [NO][BF(4)], a second reaction product, an orange solid, has been identified as a nitrosyl complex, [cat](3)[Pt(2)(mu-pop)(4)(NO)]. The X-ray structure of the PPN(+) salt shows the anion to consist of the usual lantern-shaped Pt(2)(mu-pop)(4) framework with an unusually large Pt-Pt separation [2.8375(6) A]; one of the platinum atoms carries a bent nitrosyl group [r(N-O) = 1.111(15) A; angle(Pt-N-O) = 118.1(12) degrees] occupying an axial position. The nitrosyl group migrates rapidly on the (31)P NMR time-scale between the metal atoms at room temperature but the motion is slow enough at 183 K that the expected two pairs of inequivalent phosphorus nuclei can be observed. The X-ray photoelectron (XP) spectrum of the nitrosyl-containing anion confirms the presence of two inequivalent platinum atoms whose 4f(7/2) binding energies are in the ranges expected for Pt(II) and Pt(III); an alternative interpretation is that the second platinum atom has a formal oxidation number of +4 and that its binding energy is modified by the strongly sigma-donating NO(-) ligand. Reduction of [Pt(2)(mu-pop)(4)X(2)](4-) (X = Cl, Br, I) in dichloromethane corresponds to a chemically reversible, electrochemically irreversible two-electron process involving loss of halide and formation of [Pt(2)(mu-pop)(4)](4-), as is the case in more strongly coordinating solvents.

Cyclopalladated complexes containing 2-C6R4PPh2 ligands (R = H, F): one-electron electrochemical reduction leading to metal-carbon σ-bond cleavage via palladium(I).

Three new ortho-metallated palladium complexes, [Pd(O,O'-hfacac)(κ(2)-2-C6F4PPh2)] (), [Pd2(O,O'-hfacac)2(µ-2-C6F4PPh2)2] () and [Pd(O,O'-hfacac)(κC-2-C6F4PPh2)(PPh3)] () (hfacac = hexafluoroacetylacetonate), have been prepared and fully characterised. The electrochemical reductions of complexes , together with those of other cyclopalladated complexes containing 2-C6R4PPh2 ligands (R = H, F) were studied by cyclic, rotating disk and microelectrode voltammetry. Evidence for the one-electron reduction of [PdI(κ(2)-2-C6F4PPh2)(PPh2Fc)] () was obtained from coulometric analysis, although the product is unstable and undergoes further chemical processes. Preparative electro-reduction of [Pd2(µ-Br)2(κ(2)-2-C6F4PPh2)2] () in CH2Cl2 causes reductive cleavage of its Pd-C σ-bonds and formation of the complex [PdBr2{PPh2(2-C6F4H)}2] (); possible mechanisms are discussed.

ortho-Metallated triphenylphosphine chalcogenide complexes of platinum and palladium: synthesis and catalytic activity.

Treatment of [PtI2(COD)] (COD = 1,5-cyclooctadiene) with 2-LiC6H4P(S)Ph2 gives the complex cis-[Pt{κ(2)-2-C6H4P(S)Ph2}2] () containing a pair of ortho-metallated triphenylphosphine sulfide rings. The selenium counterpart, [Pt{κ(2)-2-C6H4P(Se)Ph2}2] (), which exists as cis- and trans-isomers in solution, and the palladium analogues, cis-[Pd{κ(2)-2-C6H4P(X)Ph2}2] [X = S (), Se ()], are obtained by transmetallation of [MCl2(COD)] with the organotin reagent 2-Me3SnC6H4P(X)Ph2 in a 1 : 2 mol ratio. The reaction of [PdCl2(COD)] with 2-Me3SnC6H4P(X)Ph2 in a 1 : 1 mol ratio, and the reaction of with palladium(ii) acetate, give dinuclear, anion-bridged complexes [Pd2(µ-Cl)2{κ(2)-2-C6H4P(X)Ph2}2] [X = S (), Se ()] and [Pd2(µ-OAc)2{κ(2)-2-C6H4P(S)Ph2}2] (), respectively. Complexes and could not be made directly from triphenylphosphine sulfide by standard ortho-palladation procedures. The bridging framework in complexes and is cleaved by tertiary phosphines to give mononuclear derivatives [PdCl{κ(2)-2-C6H4P(X)Ph2}(PR3)] [X = S, R = Ph (); X = Se, R = Ph (); X = Se, R = 4-tolyl ()]. The selenium-containing compounds and decompose slowly in solution giving dinuclear complexes [PdCl(µ2-Se-κ(2)-P,Se-2-SeC6H4PPh2)PdCl(µ-2-C6H4PPh2)(PR3)] [R = Ph (), 4-tolyl ()]. The structure of complex establishes that the bridging 2-C6H4PPh2 group is generated by reduction of the phosphine selenide unit, not by ortho-metallation of the coordinated triphenylphosphine. The chloro-bridges of and are also cleaved by acetylacetonate (acac) and deprotonated Schiff bases forming mononuclear species [Pd{κ(2)-2-C6H4P(X)Ph2}L2] [L2 = acac, X = S (), Se (); L2 = 2-OC6H4CH[double bond, length as m-dash]NC6H4-4-R, X = S, R = OMe (), NO2 (); X = Se, R = OMe (), NO2 ()]. The ability of complexes , and the Schiff base-derivatives to catalyse Heck-Mizoroki and Suzuki-Miyaura C-C bond-forming reactions has also been investigated.

Synthesis, X-ray structure and electrochemical oxidation of palladium(II) complexes of ferrocenyldiphenylphosphine.

Four new complexes, [PdX(κ(2)-2-C(6)R(4)PPh(2))(PPh(2)Fc)] [X = Br, R = H (1), R = F (2); X = I, R = H (3), R = F (4)], containing ferrocenyldiphenylphosphine (PPh(2)Fc) have been prepared and fully characterised. The X-ray structures of complexes trans-1, cis-2 and cis-4, and that of a decomposition product of 4, [Pd(κ(2)-2-C(6)F(4)PPh(2))(µ-I)(µ-2-C(6)F(4)PPh(2))PdI(PPh(2)Fc)] (5), have been determined. These complexes show a distorted square planar geometry about the metal atom, the bite angles of the chelate ligands being about 69°, as expected. The cis/trans ratio of 1-4 in solution is strongly dependent on solvent. The new complexes and the uncoordinated PPh(2)Fc ligand were electrochemically characterised by cyclic and rotating disk voltammetry, UV-visible spectroelectrochemistry, and bulk electrolysis in dichloromethane and acetonitrile. In both cases, oxidation occurs at both the ferrocene and phosphine centres, but the complexes oxidise at more positive potentials than uncoordinated PPh(2)Fc; subsequently, the metal-phosphorus bond is cleaved, leading to free PPh(2)Fc(+), which undergoes further chemical and electrochemical reactions.

Synthesis and interconversions of digold(I), tetragold(I), digold(II), gold(I)-gold(III) and digold(III) complexes of fluorine-substituted aryl carbanions.

Treatment of [AuXL] (X = Br, L = AsPh(3); X = Cl, L = tht) with the lithium or trimethyltin derivatives of the carbanions [2-C6F4PPh2]- and [C6H3-n-F-2-PPh2]- (n = 5, 6) gives digold(I) complexes [Au2(mu-carbanion)2] (carbanion = 2-C6F4PPh2 2, C6H3-5-F-2-PPh2 3, C6H3-6-F-2-PPh2 4) which, like their 2-C6H4PPh2 counterpart, undergo oxidative addition with halogens X2 (X = Cl, Br, I) to give the corresponding, metal-metal bonded digold(II) complexes [Au2X2(mu-carbanion)2] (carbanion = 2-C6F4PPh2, X = Cl 5, Br 8, I 11; carbanion = C6H3-5-F-2-PPh2, X = Cl 6, Br 9, I 12; carbanion = C6H3-6-F-2-PPh2, X = Cl 7, Br 10, I 13). In the case of 2-C6F4PPh2 and C6H3-6-F-2-PPh2, the dihalodigold(II) complexes rearrange on heating to isomeric gold(I)-gold(III) complexes [XAu(I)(mu-P,C-carbanion)(kappa2-P,C-carbanion)Au(III)X] (carbanion = 2-C6F4PPh2, X = Cl 25, Br 26, I 27; carbanion = C6H3-6-F-2-PPh2, X = Cl 28, Br 29, I 30), in which one of the carbanions chelates to the gold(III) atom. This isomerisation is similar to, but occurs more slowly than, that in the corresponding C6H3-6-Me-2-PPh2 system. The Au2X2 complexes 6, 9 and 12, on the other hand, rearrange on heating via C-C coupling to give digold(I) complexes of the corresponding 2,2'-biphenyldiylbis(diphenylphosphine), [Au2X2(2,2'-Ph2P-5-F-C6H3C6H3-5-F-PPh2)] (X = Cl 32, Br 33, I 34), this behaviour resembling that of the 2-C6H4PPh2 and C6H3-5-Me-2-PPh2 systems. Since the C-C coupling probably occurs via undetected gold(I)-gold(III) intermediates, the presence of a 6-fluoro substituent is evidently sufficient to suppress the reductive eliminations, possibly because of an electronic effect that strengthens the gold(III)-aryl bond. Anation of 5 or 8 gives the bis(oxyanion)digold(II) complexes [Au2Y2(mu-2-C6F4PPh2)2] (Y = OAc 14, ONO2 15, OBz 16, O2CCF3 17 and OTf 20), which do not isomerise to the corresponding gold(I)-gold(III) complexes [YAu(mu-2-C6F4PPh2)(kappa2-2-C6F4PPh2)AuY] on heating, though the latter [Y = OAc 35, ONO2 36, OBz 37, O2CCF3 38] can be made by anation of 25-27. Reaction of the bis(benzoato)digold(II) complex 16 with dimethylzinc gives a dimethyl gold(I)-gold(III) complex, [Au(I)(mu-2-C6F4PPh2)2Au(III)(CH3)2] 19, in which both 2-C6F4PPh2 groups are bridging. In contrast, the corresponding reaction of 16 with C6F5Li gives a digold(II) complex [Au(II)2(C6F5)2(mu-2-C6F4PPh2)2] 18, which on heating isomerises to a gold(I)-gold(III) complex, [(C6F5)Au(I)(mu-2-C6F4PPh2)(kappa2-2-C6F4PPh2)Au(III)(C6F5)] 31, analogous to 25-27. The bis(triflato)digold(II) complex 20 is reduced by methanol or cyclohexanol in CH2Cl2 to a tetranuclear gold(I) complex [Au4(mu-2-C6F4PPh2)4] 21 in which the four carbanions bridge a square array of metal atoms, as shown by a single-crystal X-ray diffraction study. The corresponding tetramers [Au4(mu-C6H3-n-F-2-PPh2)4] (n = 5 22, 6 23) are formed as minor by-products in the preparation of dimers 3 and 4; the tetramers do not interconvert readily with, and are not in equilibrium with, the corresponding dimers 2-4. Addition of an excess of chlorine or bromine (X2) to the digold(II) complexes 5 and 8, and to their gold(I)-gold(III) isomers 25 and 26, gives isomeric digold(III) complexes [Au2X4(mu-2-C6F4PPh2)2] (X = Cl 39, Br 40) and [X3Au(mu-2-C6F4PPh2)AuX(kappa2-2-C6F4PPh2)] (X = Cl 41, Br 42), respectively. The structures of the digold(I) complexes 2, 4 and 32, the digold(II) complexes 5-11 and 14-18, the gold(I)-gold(III) complexes 19, 25, 35 and 38, the tetragold(I) complexes 21 and 22, and the digold(III) complexes 41 and 42, have been determined by single-crystal X-ray diffraction. In the digold(II) (5d9-5d9) series, there is a systematic lengthening, and presumably weakening, of the Au-Au distance in the range 2.5012(4)-2.5885(2) A with increasing trans-influence of the axial ligand, in the order X = ONO2 < O2CCF3 < OBz < Cl < Br < I < C6F5. The strength of the Au-Au interaction is probably the main factor that determines whether the digold(II) compounds isomerise to gold(I)-gold(III). The gold-gold separations in the digold(I) and gold(I)-gold(III) complexes are in the range 2.8-3.6 A suggestive of aurophilic interactions, but these are probably absent in the digold(III) compounds (Au...Au separation ca. 5.8 A). Attempted recrystallisation of complex 10 gave a trinuclear gold(II)-gold(II)-gold(I) complex, [Au3Br2(mu-C6H3-6-F-2-PPh2)3] 24, which consists of the expected digold(II) framework in which one of the axial bromide ligands has been replaced by a sigma-carbon bonded (C6H3-6-F-2-PPh2)Au(I)Br fragment.

Bis(acetylacetonato)ruthenium(II) complexes containing alkynyldiphenylphosphines. Formation and redox behaviour of [Ru(acac)2(Ph2PC triple bond CR)2] (R=H, Me, Ph) complexes and the binuclear complex cis-[{Ru(acac)2}2(micro-Ph2PC triple bond CPPh2)}2].

Two equivalents of Ph(2)PC triple bond CR (R=H, Me, Ph) react with thf solutions of cis-[Ru(acac)(2)(eta(2)-alkene)(2)] (acac=acetylacetonato; alkene=C(2)H(4), 1; C(8)H(14), 2) at room temperature to yield the orange, air-stable compounds trans-[Ru(acac)(2)(Ph(2)PC triple bond CR)(2)] (R=H, trans-3; Me=trans-4; Ph, trans-5) in isolated yields of 60-98%. In refluxing chlorobenzene, trans-4 and trans-5 are converted into the yellow, air-stable compounds cis-[Ru(acac)(2)(Ph(2)PC triple bond CR)(2)] (R=Me, cis-4; Ph, cis-5), isolated in yields of ca. 65%. From the reaction of two equivalents of Ph(2)PC triple bond CPPh(2) with a thf solution of 2 an almost insoluble orange solid is formed, which is believed to be trans-[Ru(acac)(2)(micro-Ph(2)PC triple bond CPPh(2))](n) (trans-6). In refluxing chlorobenzene, the latter forms the air-stable, yellow, binuclear compound cis-[{Ru(acac)(2)(micro-Ph(2)PC triple bond CPPh(2))}(2)] (cis-6). Electrochemical studies indicate that cis-4 and cis-5 are harder to oxidise by ca. 300 mV than the corresponding trans-isomers and harder to oxidise by 80-120 mV than cis-[Ru(acac)(2)L(2)] (L=PPh(3), PPh(2)Me). Electrochemical studies of cis-6 show two reversible Ru(II/III) oxidation processes separated by 300 mV, the estimated comproportionation constant (K(c)) for the equilibrium cis-6(2+) + cis6 <=> 2(cis-6(+)) being ca. 10(5). However, UV-Vis spectra of cis-6(+) and cis-6(2+), generated electrochemically at -50 degrees C, indicate that cis-6(+) is a Robin-Day Class II mixed-valence system. Addition of one equivalent of AgPF(6) to trans-3 and trans-4 forms the green air-stable complexes trans-3 x PF(6) and trans-4 x PF(6), respectively, almost quantitatively. The structures of trans-4, cis-4, trans-4 x PF(6) and cis-6 have been confirmed by X-ray crystallography.

ortho-Metallated complexes of platinum(II) and diplatinum(I) containing the carbanions (2-diphenylphosphino)phenyl and (2-diphenylphosphino)-n-tolyl (n = 5, 6).

When the ortho-metallated complexes cis-[Pt(kappa(2)-C6H3-5-R-2-PPh2)2] (R = H 1, Me 2) are either heated in toluene or treated with CO at room temperature, one of the four-membered chelate rings is opened irreversibly to give dinuclear isomers [Pt2(kappa(2)-C6H3-5-R-2-PPh2)2(mu-C6H3-5-R-2-PPh2)2] (R = H 10, Me 11). A single-crystal X-ray diffraction study shows the Pt...Pt separation in 10 to be 3.3875(4) A. By-products of the reactions of 1 and 2 with CO are polymeric isomers (R = H 13, Me 14) in which one of the P-C ligands is believed to bridge adjacent platinum atoms intermolecularly. In contrast to the behaviour of 1 and 2, when cis-[Pt(kappa(2)-C6H3-6-Me-2-PPh2)2] (cis-3) is heated in toluene, the main product is trans-3, and reaction of cis-3 with CO gives a carbonyl complex [Pt(CO)(kappa(1)-C-C6H3-6-Me-2-PPh2)(2-C6H3-6-Me-2-PPh2)] 15, in which one of the carbanions is coordinated only through the carbon. Formation of a dimer analogous to 10 or 11 is sterically hindered by the 6-methyl substituent. Comproportionation of 1 or 2 with [Pt(PPh3)2L] (L = PPh3, C2H4) gives diplatinum(I) complexes [Pt2(mu-C6H3-5-R-2-PPh2)2(PPh3)2] (R = H 16, Me 17). An X-ray diffraction study shows that 17 contains a pair of planar-coordinated metal atoms separated by 2.61762(16) A. There is no evidence for the formation of an analogue containing mu-C6H3-6-Me-2-PPh2. The axial PPh3 ligands of 16 are readily replaced by ButNC giving [Pt2(mu-2-C6H4PPh2)2(CNBut)2] 18, which is protonated by HBF4 to form a mu-hydridodiplatinum(II) salt [Pt2(mu-H)(mu-2-C6H4PPh2)2(CNBut)2]BF4 [21]BF4. The J(PtPt) values in [21]BF4 and 18, 2700 Hz and 4421 Hz, respectively, reflect the weakening of the Pt-Pt interaction caused by protonation. Similarly, 16 and 17 react with the electrophiles iodine and strong acids to give salts of general formula [Pt2(mu-Z)(mu-C6H3-5-R-2-PPh2)2(PPh3)2]Y (Y = Z = I, R = H 19+, Me 20+; Z = H, Y = BF4, PF6, OTf, R = H 22+; Z = H, Y = PF6, R = Me 23+). A single-crystal X-ray diffraction study of [23]PF6 shows that the cation has an approximately A-frame geometry, with a Pt-Pt separation of 2.7888(3) A and a Pt-H bond length of 1.62(1) A, and that the 5-methyl substituents have undergone partial exchange with the 4-hydrogen atoms of the PPh2 groups of the bridging carbanion. The latter observation indicates that the added proton of [23]+ undergoes a reversible reductive elimination-oxidative addition sequence with the Pt-C(aryl) bonds.

Synthesis, structures and reactions of cyclometallated gold complexes containing (2-diphenylarsino-n-methyl)phenyl (n = 5, 6).

Reaction of (C6H3-2-AsPh2-n-Me)Li (n = 5 or 6) with [AuBr(AsPh3)] at -78 degrees C gives the corresponding cyclometallated gold(I) complexes [Au2[(mu-C6H3-n-Me)AsPh2]2] [n = 5, (1); n = 6, (9)]. 1 undergoes oxidative addition with halogens and with dibenzoyl peroxide to give digold(II) complexes [Au2X2[(mu-C6H3-5-Me)AsPh2]2] [X = Cl (2a), Br (2b), I (2c) and O2CPh (3)] containing a metal-metal bond between the 5d9 metal centres. Reaction of 2a with AgO2CMe or of 3 with C6F5Li gives the corresponding digold(II) complexes in which X = O2CMe (4) and C6F5 (6), respectively. The Au-Au distances increase in the order 4 < 2a < 2b < 2c < 6, following the covalent binding tendency of the axial ligand. Like the analogous phosphine complexes, 2a-2c and 6 in solution rearrange to form C-C coupled digold(I) complexes [Au2X2[mu-2,2-Ph2As(5,5-Me2C6H3C6H3)AsPh2]] [X = Cl (5a), X = Br (5b), X = I (5c) and C6F5 (7)] in which the gold atoms are linearly coordinated by As and X. In contrast, the products of oxidative additions to 9 depend markedly on the halogens. Reaction of 9 with chlorine gives the gold(I)-gold(III) complex, [ClAu[mu-2-Ph2As(C6H3-6-Me)]AuCl[(6-MeC6H3)-2-AsPh2]-kappa2As,C] (10), which contains a four-membered chelate ring, Ph2As(C6H3-6-Me), in the coordination sphere of the gold(III) atom. When 10 is heated, the ring is cleaved, the product being the digold(I) complex [ClAu[mu-2-Ph2As(C6H3-6-Me)]Au[AsPh2(2-Cl-3-Me-C6H3)]] (11). Reaction of 9 with bromine at 50 degrees C gives a monobromo digold(I) complex (12), which is similar to 11 except that the 2-position of the substituted aromatic ring bears hydrogen instead halogen. Reaction of 9 with iodine gives a mixture of a free tertiary arsine, (2-I-3-MeC6H3)AsPh2 (13), a digold diiodo compound (14) analogous to 11, and a gold(I)-gold(III) zwitterionic complex [I2Au(III)[(mu-C6H3-2-AsPh2-6-Me)]2Au(I)] (15) in which the bridging units are arranged head-to-head between the metal atoms. The structures of 2a-2c and 4-15 have been determined by single-crystal X-ray diffraction analysis. The different behaviour of 1 and 9 toward halogens mirrors that of their phosphine analogues; the 6-methyl substituent blocks C-C coupling of the aryl residues in the initially formed oxidative addition product. In the case of 9, the greater lability of the Au-As bond in the initial oxidative addition product may account for the more complex behaviour of this system compared with that of its phosphine analogue.

Electrochemically informed synthesis and characterization of salts of the [Pt2(mu-kappaAs,kappaC-C6H3-5-Me-2-AsPh2)4]+ lantern complex containing a Pt-Pt bond of order 1/2.

Detailed electrochemical studies in dichloromethane (0.1 M Bu4NPF6) on the oxidation of the half-lantern [Pt2(kappa2As,C-C6H3-5-Me-2-AsPh2)2(mu-kappaAs,kappaC-C6H3-5-Me-2-AsPh2)2] (1) and full-lantern [Pt2(mu-kappaAs,kappaC-C6H3-5-Me-2-AsPh2)4] (2) complexes reveal the presence of an exceptionally stable dinuclear Pt cation 2+. Thus, oxidation of 1 occurs on the voltammetric time scale via a ladder-square scheme to give 2+, whereas 2 is directly converted to 2+. Electrochemically informed chemical synthesis enabled the isolation of solid [2+][BF4-] to be achieved. Single-crystal X-ray structural analysis showed that 2+ also has a lantern structure but with a shorter separation between the Pt centers [2.7069(3) A (2+), 2.8955(4) A (2)]. EPR spectra of 2+ provide unequivocal evidence for axial symmetry of the complex and are noteworthy because of an exceptionally large, nearly isotropic hyperfine coupling constant of about 0.1 cm(-1). Spectroscopic data support the conclusion that the unpaired electron in the 2+ cation is distributed equally between the two Pt nuclei and imply that oxidation of 2 to 2+ leads to the establishment of the metal-to-metal hemibond. Results of extended Huckel molecular orbital and density functional calculations on 2 and 2+ lead to the conclusions that s, p, dz2 mixing of orbitals contributes to the large EPR Pt hyperfine coupling and also that the structural adjustments that occur upon removal of an electron from 2 are driven by the metal-metal bonding character present in 2+.

Is it homogeneous or heterogeneous catalysis? Identification of bulk ruthenium metal as the true catalyst in benzene hydrogenations starting with the monometallic precursor, Ru(II)(eta 6-C6Me6)(OAc)2, plus kinetic characterization of the heterogeneous nucleation, then autocatalytic surface-growth mechanism of metal film formation.

A reinvestigation of the true catalyst in a benzene hydrogenation system beginning with Ru(II)(eta(6)-C(6)Me(6))(OAc)(2) as the precatalyst is reported. The key observations leading to the conclusion that the true catalyst is bulk ruthenium metal particles, and not a homogeneous metal complex or a soluble nanocluster, are as follows: (i) the catalytic benzene hydrogenation reaction follows the nucleation (A --> B) and then autocatalytic surface-growth (A + B --> 2B) sigmoidal kinetics and mechanism recently elucidated for metal(0) formation from homogeneous precatalysts; (ii) bulk ruthenium metal forms during the hydrogenation; (iii) the bulk ruthenium metal is shown to have sufficient activity to account for all the observed activity; (iv) the filtrate from the product solution is inactive until further bulk metal is formed; (v) the addition of Hg(0), a known heterogeneous catalyst poison, completely inhibits further catalysis; and (vi) transmission electron microscopy fails to detect nanoclusters under conditions where they are otherwise routinely detected. Overall, the studies presented herein call into question any claim of homogeneous benzene hydrogenation with a Ru(arene) precatalyst. An additional, important finding is that the A --> B, then A + B --> 2B kinetic scheme previously elucidated for soluble nanocluster homogeneous nucleation and autocatalytic surface growth (Widegren, J. A.; Aiken, J. D., III; Ozkar, S.; Finke, R. G. Chem. Mater. 2001, 13, 312-324, and ref 8 therein) also quantitatively accounts for the formation of bulk metal via heterogeneous nucleation then autocatalytic surface growth. This is significant for three reasons: (i) quantitative kinetic studies of metal film formation from soluble precursors or chemical vapor deposition are rare; (ii) a clear demonstration of such A --> B, then A + B --> 2B kinetics, in which both the induction period and the autocatalysis are continuously monitored and then quantitatively accounted for, has not been previously demonstrated for metal thin-film formation; yet (iii) all the mechanistic insights from the soluble nanocluster system (op. cit.) should be applicable to metal thin-film formations which exhibit sigmoidal kinetics and, hence, the A --> B, then A + B --> 2B mechanism.

Bis[(2-diphenylphosphino)phenyl]mercury: a P-donor ligand and precursor to mixed metal-mercury (d(8)-d(10)) cyclometalated complexes containing 2-C(6)H(4)PPh(2).

Treatment of HgCl(2) with 2-LiC(6)H(4)PPh(2) gives [Hg(2-C(6)H(4)PPh(2))(2)] (1), whose phosphorus atoms take up oxygen, sulfur, and borane to give the compounds [Hg[2-C(6)H(4)P(X)Ph(2)](2)] [ X = O (3), S (4), and BH(3) (5)], respectively. Compound 1 functions as a bidentate ligand of wide, variable bite angle that can span either cis or trans coordination sites in a planar complex. Representative complexes include [HgX(2) x 1] [X = Cl (6a), Br (6b)], cis-[PtX(2) x 1] [X = Cl (cis-7), Me (9), Ph (10)], and trans-[MX(2) x 1] [X = Cl, M = Pt (trans-7), Pd (8), Ni (11); X = NCS, M = Ni (13)] in which the central metal ions are in either tetrahedral (6a,b) or planar (7-11, 13) coordination. The trans disposition of 1 in complexes trans-7, 8, and 11 imposes close metal-mercury contacts [2.8339(7), 2.8797(8), and 2.756(8) A, respectively] that are suggestive of a donor-acceptor interaction, M --> Hg. Prolonged heating of 1 with [PtCl(2)(cod)] gives the binuclear cyclometalated complex [(eta(2)-2-C(6)H(4)PPh(2))Pt(mu-2-C(6)H(4)PPh(2))(2)HgCl] (14) from which the salt [(eta(2)-2-C(6)H(4)PPh(2))Pt(mu-2-C(6)H(4)PPh(2))(2)Hg]PF(6) (15) is derived by treatment with AgPF(6). In 14 and 15, the mu-C(6)H(4)PPh(2) groups adopt a head-to-tail arrangement, and the Pt-Hg separation in 14, 3.1335(5) A, is in the range expected for a weak metallophilic interaction. A similar arrangement of bridging groups is found in [Cl((n)Bu(3)P)Pd(mu-C(6)H(4)PPh(2))(2)HgCl] (16), which is formed by heating 1 with [PdCl(2)(P(n)()Bu(3))(2)]. Reaction of 1 with [Pd(dba)(2)] [dba = dibenzylideneacetone] at room temperature gives [Pd(1)(2)] (19) which, in air, forms a trigonal planar palladium(0) complex 20 containing bidentate 1 and the monodentate phosphine-phosphine oxide ligand [Hg(2-C(6)H(4)PPh(2))[2-C(6)H(4)P(O)Ph(2)]]. On heating, 19 eliminates Pd and Hg, and the C-C coupled product 2-Ph(2)PC(6)H(4)C(6)H(4)PPh(2)-2 (18) is formed by reductive elimination. In contrast, 1 reacts with platinum(0) complexes to give a bis(aryl)platinum(II) species formulated as [Pt(eta(1)-C-2-C(6)H(4)PPh(2))(eta(2)-2-C(6)H(4)PPh(2))(eta(1)-P-1)]. Crystal data are as follows. Compound 3: monoclinic, P2(1)/n, with a = 11.331(3) A, b = 9.381(2) A, c = 14.516 A, beta = 98.30(2) degrees, and Z = 2. Compound 6b x 2CH(2)Cl(2): triclinic, P macro 1, with a = 12.720(3) A, b = 13.154(3) A, c = 12.724(2) A, alpha = 92.01(2) degrees, beta = 109.19(2) degrees, gamma = 90.82(2) degrees, and Z = 2. Compound trans-7 x 2CH(2)Cl(2): orthorhombic, Pbca, with a = 19.805(3) A, b = 8.532(4) A, c = 23.076(2) A, and Z = 4. Compound 11 x 2CH(2)Cl(2): orthorhombic, Pbca, with a = 19.455(3) A, b = 8.496(5) A, c = 22.858(3) A, and Z = 4. Compound 14: monoclinic, P2(1)/c, with a = 13.150(3) A, b = 12.912(6) A, c = 26.724(2) A, beta = 94.09(1) degrees, and Z = 4. Compound 20 x C(6)H(5)CH(3).0.5CH(2)Cl(2): triclinic, P macro 1, with a = 13.199(1) A, b = 15.273(2) A, c = 17.850(1) A, alpha = 93.830(7), beta = 93.664(6), gamma = 104.378(7) degrees, and Z = 2.

Preparation of benzyne complexes of group 10 metals by intramolecular suzuki coupling of ortho-metalated phenylboronic esters: molecular structure of the first benzyne-palladium(0) complex.

A series of nickel(II) and palladium(II) aryl complexes substituted in the ortho position of the aromatic ring by a (pinacolato)boronic ester group, [MBr[o-C(6)H(4)B(pin)]L(2)] (M = Ni, L(2) = 2PPh(3) (2a), 2PCy(3) (2b), 2PEt(3) (2c), dcpe (2d), dppe (2e), and dppb (2f); M = Pd, L(2) = 2PPh(3) (3a), 2PCy(3) (3b), and dcpe (3d)), has been prepared. Many of these complexes react readily with KO(t)Bu to form the corresponding benzyne complexes [M(eta(2)-C(6)H(4))L(2)] (M = Ni, L(2) = 2PPh(3) (4a), 2PCy(3) (4b), 2PEt(3) (4c), dcpe (4d); M = Pd, L(2) = 2PCy(3) (5b)). This reaction can be regarded as an intramolecular version of a Suzuki cross-coupling reaction, the driving force for which may be the steric interaction between the boronic ester group and the phosphine ligands present in the precursors 2 and 3. Complex 3d also reacts with KO(t)Bu, but in this case disproportionation of the initially formed eta(2)-C(6)H(4) complex (5d) leads to a 1:1 mixture of a novel dinuclear palladium(I) complex, [(dcpe)Pd(mu(2)-C(6)H(4))Pd(dcpe)] (6), and a 2,2'-biphenyldiyl complex, [Pd(2,2'-C(6)H(4)C(6)H(4))(dcpe)] (7d). Complexes 2a, 3b, 3d, 4b, 5b, 6, and 7d have been structurally characterized by X-ray diffraction; complex 5b is the first example of an isolated benzyne-palladium(0) species.

Synthesis, characterization, and electrochemical relationships of dinuclear complexes of platinum(II) and platinum(III) containing ortho-metalated tertiary arsine ligands.

Reaction of 2-Li-4-MeC6H3AsPh2 with [PtCl2(SEt2)2] gives two isomeric dinuclear platinum(II) complexes, one containing a half-lantern structure with two chelating and two bridging C6H3-5-Me-2-AsPh2 ligands, [Pt2(kappa2As,C-C6H3-5-Me-2-AsPh2)2(mu-kappaAs,kappaC-C6H3-5-Me-2-AsPh2)2], and the other, a full-lantern with four bridging C6H3-5-Me-2-AsPh2 ligands, [Pt2(mu-kappaAs,kappaC-C6H3-5-Me-2-AsPh2)4]. The lantern structure of the latter is retained in the dihalodiplatinum(III) complexes that are formed by oxidative addition of chlorine, bromine, or iodine to the isomeric mixture. The dichloro derivative undergoes metathesis reactions with silver or sodium salts, yielding the corresponding cyano, thiocyanato, cyanato, and fluoro species. The structures of all complexes have been determined by single-crystal X-ray analysis. The oxidative addition products have Pt-Pt distances in the range 2.65-2.79 A (cf. 2.89 A in the lantern diplatinum(II) structure), consistent with the presence of a Pt-Pt bond. Electrochemical data lead to the conclusion that an initial rapid one-electron process and subsequent chemical reactions produce the dihalodiplatinum(III) lantern structure when mixtures of the lantern and half-lantern complexes are oxidized by halogens. The electrochemical data also explain why chemical reduction of the dihalodiplatinum(III) complex produces only the lantern diplatinum(II) complex.

Arene-ruthenium complexes of an acyclic thiolate-thioether and tridentate thioether derivatives resulting from ring-closure reactions.

The reaction of [(eta(6)-arene)RuCl(2)](2) (arene = C(6)Me(6), 1,4-MeC(6)H(4)CHMe(2)) with a large excess of the dianion of bis(2-mercaptoethyl) sulfide, (HSCH(2)CH(2))(2)S, obtained from deprotonation of the dithiol with freshly prepared NaOMe, gives the deep red, monomeric complexes [(eta(6)-arene)Ru(eta(3)-C(4)H(8)S(3))] (arene = C(6)Me(6) (5), 1,4-MeC(6)H(4)CHMe(2) (6)) in which the dianion is bound to the metal atom through one thioether and two thiolate sulfur atoms. Complex 5 reacts with [(eta(6)-C(6)Me(6))RuCl(2)](2) (4) in a 2:1 mole ratio to give a quantitative yield of the chloride salt of a binuclear cation [((eta(6)-C(6)Me(6))Ru)(2)Cl(mu(2)-eta(2):eta(3)-C(4)H(8)S(3))](+) (7) in which the thiolate sulfur atoms of the [(eta(6)-C(6)Me(6))Ru(eta(3)-C(4)H(8)S(3))] group bridge to a (eta(6)-C(6)Me(6))RuCl unit. This compound is also obtained directly from the reaction of 4 with the dithiolate, if the Ru dimer is used in large excess. The binuclear complex [((eta(6)-C(6)Me(6))Ru)(2)(MeCN)(mu(2)-eta(2):eta(3)-C(4)H(8)S(3))](PF(6))(2).MeCN, (9)(PF(6))(2).MeCN, is obtained by treatment of (7)Cl with NH(4)PF(6) in acetonitrile. Protonation of 5 with HCl gave the mono- and diprotonated derivatives viz. [(eta(6)-C(6)Me(6))Ru(eta(3)-C(4)H(9)S(3))]Cl, (8)Cl, and [(eta(6)-C(6)Me(6))Ru(eta(3)-C(4)H(10)S(3))]Cl(2), (10)Cl(2), respectively. The reaction of 5 with methyl iodide gives both the mono- and di-S-methylated derivatives. Treatment of 5 with dibromoalkanes, Br(CH(2))(n)Br (n = 1-5), effects ring closure to give the (eta(6)-C(6)Me(6))Ru dications containing the trithia mesocyclic zS3 (z = 8-12) ligands, isolated as their PF(6) salts. The X-ray crystal structures of 5, 6, the solvates of (7)Cl and (9)(PF(6))(2), and the trithia mesocyclic Ru complexes (eta(6)-C(6)Me(6))Ru(zS3)(PF(6))(2) (z = 8-11) are reported.