Amidinatotetrylenes Donor Functionalized on Both N Atoms: Structures and Coordination Chemistry.

E(hmds)(bqfam) (E = Ge (1a), Sn (1b); hmds = N(SiMe3)2, bqfam = N,N'-bis(quinol-8-yl)formamidinate), which are amidinatotetrylenes equipped with quinol-8-yl fragments on the amidinate N atoms, have been synthesized from the formamidine Hbqfam and Ge(hmds)2 or SnCl(hmds). Both 1a and 1b are fluxional in solution at room temperature, as the E atom oscillates from being attached to the two amidinate N atoms to being chelated by an amidinate N atom and its closest quinolyl N atom (both situations are similarly stable according to density functional theory calculations). The hmds group of 1a and 1b is still reactive and the deprotonation of another equivalent of Hbqfam can be achieved, allowing the formation of the homoleptic derivatives E(bqfam)2 (E = Ge, Sn). The reactions of 1a and 1b with [AuCl(tht)] (tht = tetrahydrothiophene), [PdCl2(MeCN)2], [PtCl2(cod)] (cod = cycloocta-1,5-diene), [Ru3(CO)12] and [Co2(CO)8] have been investigated. The gold(I) complexes [AuCl{κE-E(hmds)(bqfam)}] (E = Ge, Sn) have a monodentate κE-tetrylene ligand and display fluxional behavior in solution the same as that of 1a and 1b. However, the palladium(II) and platinum(II) complexes [MCl{κ3E,N,N'-ECl(hmds)(bqfam)}] (M = Pd, Pt; E = Ge, Sn) contain a κ3E,N,N'-chloridotetryl ligand that arises from the insertion of the tetrylene E atom into an M-Cl bond and the coordination of an amidinate N atom and its closest quinolyl N atom to the metal center. Finally, the binuclear ruthenium(0) and cobalt(0) complexes [Ru2{µE-κ3E,N,N'-E(hmds)(bqfam)}(CO)6] and [Co2{µE-κ3E,N,N'-E(hmds)(bqfam)}(µ-CO)(CO)4] (E = Ge, Sn) have a related κ3E,N,N'-tetrylene ligand that bridges two metal atoms through the E atom. For the κ3E,N,N'-metal complexes, the quinolyl fragment not attached to the metal is pendant in all the germanium compounds but, for the tin derivatives, is attached to (in the Pd and Pt complexes) or may interact with (in the Ru2 and Co2 complexes) the tin atom.

Synthesis and Some Coordination Chemistry of Phosphane-Difunctionalized Bis(amidinato)-Heavier Tetrylenes: A Previously Unknown Class of PEP Tetrylenes (E = Ge and Sn).

The bis(amidinato)-heavier tetrylenes E(bzamP)2 (E = Ge (2a) and Sn (2b); bzamP = N-isopropyl-N'-(diphenylphosphanylethyl)benzamidinate), which are equipped with one heavier tetrylene (germylene or stannylene) and two phosphane fragments (one on each amidinate moiety) as coordinable groups, have been synthesized from the benzamidinum salt [H2bzamP]Cl and GeCl2(dioxane) or SnCl2 in 2:1 mol ratio. A preliminary inspection of their coordination chemistry has shown that their amidinate group can also be involved in the bonding with the metal atoms as tridentate ENP and tetradentate PENP' coordination modes have been observed for the ECl(bzamP)2 ligand of [Ir{κ3E,N,P-ECl(bzamP)2}(cod)] (E = Ge (3a) and Sn (3b); cod = η4-1,5-cyclooctadiene) and the E(bzamP)2 ligand of [Ni{κ4E,N,P,P'-E(bzamP)2}] (E = Ge (4a) and Sn (4b)), which are products of reactions of 2a and 2b with [IrCl(cod)]2 (1:0.5 mol ratio) and [Ni(cod)2] (1:1 mol ratio), respectively. These products contain a 5-membered NCNEM ring that results from the insertion of the metal M atom into an E-N bond of 2a and 2b. Additionally, while iridium(I) complexes 3a and 3b are chloridotetryl derivatives (insertion of the tetrylene E atom into the Ir-Cl bond has also occurred) that have an uncoordinated phosphane group, nickel(0) complexes 4a and 4b contain a tetrylene fragment that, maintaining the lone pair, behaves as a σ-acceptor (Z-type) ligand.

From a Diphosphanegermylene to Nickel, Palladium, and Platinum Complexes Containing Germyl PGeP Pincer Ligands.

The PGeP pincer-type germylene Ge(NCH2 PtBu2 )C6 H4 (1) has been used to prepare a family of group 10 metal complexes, namely, [MCl{κ3 P,Ge,P-GeCl(NCH2 PtBu2 )2 C6 H4 }] (M=Ni (2Ni ), Pd (2Pd ), Pt (2Pt )), featuring a chloridogermyl PGeP pincer ligand and a Cl-Ge-M-Cl bond sequence. Their reactivity is not initially centered on the metal atom but on their Ge atom. Complexes 2Ni and 2Pd easily led to the hydrolyzed products [Ni2 Cl2 {µ-(κ3 P,Ge,P-Ge(NCH2 PtBu2 )2 C6 H4 )2 O}], which features a Cl-Ni-Ge-O-Ge-Ni-Cl bond sequence, and [PdCl{κ3 P,Ge,P-Ge(OH)(NCH2 PtBu2 )2 C6 H4 }], which contains a hydroxidogermyl PGeP pincer ligand (2Pt is reluctant to undergo hydrolysis). Simple chloride exchange reactions led to the methoxidogermyl, methylgermyl, and phenylgermyl derivatives [MCl{κ3 P,Ge,P-GeR(NCH2 PtBu2 )2 C6 H4 }] (M=Pd, Pt; R=OMe, Me, Ph). Whereas the palladium complexes [PdCl{κ3 P,Ge,P-GeR(NCH2 PtBu2 )2 C6 H4 }] (R=Me, Ph) reacted with more MeLi or PhLi to give palladium black and GeR2 (NCH2 PtBu2 )2 C6 H4 (R=Me, Ph), similar reactions with the analogous platinum complexes afforded the transmetalation derivatives [PtR{κ3 P,Ge,P-GeR(NCH2 PtBu2 )2 C6 H4 }] (R=Me, Ph). The short length of the CH2 PtBu2 arms of the PGeP pincer ligands forces the metal atoms of all these complexes to be in a very distorted square-planar ligand environment. The reactivity results have been rationalized with theoretical calculations.

2-(Methylamido)pyridine-Borane: A Tripod κ(3)-N,H,H Ligand in Trigonal Bipyramidal Rhodium(I) and Iridium(I) Complexes with an Asymmetric Coordination of Its BH3 Group.

The complexes [M(κ(3)-N,H,H-mapyBH3)(cod)] (M = Rh, Ir; HmapyBH3 = 2-(methylamino)pyridine-borane; cod = 1,5-cyclooctadiene), which contain a novel anionic tripod ligand coordinated to the metal atom through the amido N atom and through two H atoms of the BH3 group, were prepared by treating the corresponding [M2(µ-Cl)2(cod)2] (M = Rh, Ir) precursor with K[mapyBH3]. X-ray diffraction studies and a theoretical Quantum Theory of Atoms in Molecules analysis of their electron density confirmed that the metal atoms of both complexes are in a very distorted trigonal bipyramidal coordination environment, in which two equatorial sites are asymmetrically spanned by the H-B-H fragment. While both 3c-2e BH-M interactions are more κ(1)-H (terminal σ coordination of the B-H bond) than κ(2)-H,B (agostic-type coordination of the B-H bond), one BH-M interaction is more agostic than the other, and this difference is more marked in the iridium complex than in the rhodium one. This asymmetry is not evident in solution, where the cod ligand and the BH3 group of these molecules participate in two concurrent dynamic processes of low activation energies (variable-temperature NMR and density functional theory studies), namely, a rotation of the cod ligand that interchanges its two alkene fragments (through a square pyramidal transition state) and a rotation of the BH3 group about the B-N bond that equilibrates the three B-H bonds (through a square planar transition state). While the cod rotation has similar activation energy in 2 and 3, the barrier to the BH3 group rotation is higher in the iridium complex than in the rhodium one.

Reactivity Studies on a Binuclear Ruthenium(0) Complex Equipped with a Bridging κ(2)N,Ge-Amidinatogermylene Ligand.

The amidinatogermylene-bridged diruthenium(0) complex [Ru2{µ-κ(2)Ge,N-Ge((i)Pr2bzam)(HMDS)}(CO)7] (2; (i)Pr2bzam = N,N'-bis(iso-propyl)benzamidinate; HMDS = N(SiMe3)2) reacted at room temperature with (t)BuNC and PMe3 to give [Ru2{µ-κ(2)Ge,N-Ge((i)Pr2bzam)(HMDS)}(L)(CO)6] (L = (t)BuNC, 3; PMe3, 4), which contain the new ligand in an axial position on the Ru atom that is not attached to the amidinato fragment. At 70 °C, 2 reacted with PPh3, PMe3, dppm, and dppe to give the equatorially substituted derivatives [Ru2{µ-κ(2)Ge,N-Ge((i)Pr2bzam)(HMDS)}(L)(CO)6] (L = PPh3, 5; PMe3, 6) and [Ru2{µ-κ(2)Ge,N-Ge((i)Pr2bzam)(HMDS)}(µ-κ(2)P,P'-L2)(CO)5] (L2 = dppm, 7; dppe, 8). HSiEt3 and HSnPh3 were oxidatively added to complex 2 at 70 °C, leading to the coordinatively unsaturated products [Ru2(ER3)(µ-H){µ-κ(2)Ge,N-Ge((i)Pr2bzam)(HMDS)}(CO)5] (ER3 = SiEt3, 9; SnPh3, 10), which easily reacted with (t)BuNC and CO to give the saturated derivatives [Ru2(ER3)(µ-H){µ-κ(2)Ge,N-Ge((i)Pr2bzam)(HMDS)}((t)BuNC)(CO)5] (ER3 = SiEt3, 11; SnPh3, 12) and [Ru2(ER3)(µ-H){µ-κ(2)Ge,N-Ge((i)Pr2bzam)(HMDS)}(CO)6] (ER3 = SiEt3, 13; SnPh3, 14), respectively. Compounds 9-14 have their ER3 group on the Ru atom that is not attached to the amidinato fragment. In contrast, the reaction of 2 with H2 at 70 °C led to the unsaturated tetranuclear complex [Ru4(µ-H)2{µ-κ(2)Ge,N-Ge((i)Pr2bzam)(HMDS)}2(CO)10] (15), which also reacted with (t)BuNC and CO to give the saturated derivatives [Ru4(µ-H)2{µ-κ(2)Ge,N-Ge((i)Pr2bzam)(HMDS)}2(L)2(CO)10] (L = (t)BuNC, 16; CO, 17). All tetraruthenium complexes contain an unbridged metal-metal connecting two germylene-bridged diruthenium units. Under CO atmosphere, complex 17 reverted to compound 2. All of the coordinatively unsaturated products (9, 10, and 15) have their unsaturation(s) located on the Ru atom(s) that is(are) attached to the amidinato fragment(s). In the absence of added reagents, the thermolysis of 2 in refluxing toluene led to [Ru4{µ-κ(2)Ge,N-Ge((i)Pr2bzam)(HMDS)}{µ3-κGe-Ge(HMDS)}(µ-κ(3)N,C,N'-(i)Pr2bzam)(µ-CO)(CO)8] (18), which contains two new ligands, a triply bridging germylidyne and a bridging benzamidinate, and that results from the condensation of two molecules of 2 and the activation of the Ge-N bond of the benzamidinatogermylene ligand of 2.

Amidinatogermylene derivatives of ruthenium carbonyl: new insights into the reactivity of [Ru3(CO)12] with two-electron-donor reagents of high basicity.

The reactivity of ruthenium carbonyl with amidinatogermylenes of the type Ge(R2bzam)(t)Bu (R2bzam = N,N'-disubstituted benzamidinate) was studied for R = (t)Bu (1tBu) and (i)Pr (1iPr). The mono-, bi-, and/or trinuclear derivatives [Ru(1R)(CO)4], [Ru(1R)2(CO)3], [Ru2(1iPr)(CO)7], [Ru3(1tBu)(CO)11], [Ru3(1tBu)2(CO)10], and [Ru3(1R)3(CO)9] (R = (t)Bu, (i)Pr) were isolated in yields that depend upon the reactant ratio and the reaction temperature. The experimental data are consistent with the proposal that, at room temperature, the trinuclear complexes [Ru3(CO)12], [Ru3(1R)(CO)11], and [Ru3(1R)2(CO)10] form an adduct with the germylene 1R that may evolve through two different reaction pathways, (a) releasing a CO ligand (thus leading to the corresponding trinuclear CO-substituted product) and/or (b) cleaving the cluster framework (thus leading to mononuclear germylene-containing products). At 90 °C, additional processes are also possible, such as the reactions of 1R with [Ru(1R)(CO)4] or [Ru3(1R)3(CO)9], which both give [Ru(1R)2(CO)3], or the reactions of [Ru(1tBu)(CO)4] and [Ru(1iPr)(CO)4] with [Ru3(CO)12], which give [Ru3(1tBu)(CO)11] and [Ru2(1iPr)(CO)7], respectively. This wide reaction panorama helps rationalize previously reported outcomes of reactions of [Ru3(CO)12] with other reagents of high basicity, such as trialkylphosphines or N-heterocyclic carbenes, including results for which no satisfactory explanation has been hitherto provided.

Ring opening and bidentate coordination of amidinate germylenes and silylenes on carbonyl dicobalt complexes: the importance of a slight difference in ligand volume.

The reactions of [Co2 (CO)8 ] with one equiv of the benzamidinate (R2 bzam) group-14 tetrylenes [M(R2 bzam)(HMDS)] (HMDS=N(SiMe3 )2 ; 1: M=Ge, R=iPr; 2: M=Si, R=tBu; 3: M=Ge, R=tBu) at 20 °C led to the monosubstituted complexes [Co2 {κ(1) MM(R2 bzam)(HMDS)}(CO)7 ] (4: M=Ge, R=iPr; 5: M=Si, R=tBu; 6: M=Ge, R=tBu), which contain a terminal κ(1) M-tetrylene ligand. Whereas the Co2 Si and Co2 Ge tert-butyl derivatives 5 and 6 are stable at 20 °C, the Co2 Ge isopropyl derivative 4 evolved to the ligand-bridged derivative [Co2 {µ-κ(2) Ge,N-Ge(iPr2 bzam)(HMDS)}(µ-CO)(CO)5 ] (7), in which the Ge atom spans the CoCo bond and one arm of the amidinate fragment is attached to a Co atom. The mechanism of this reaction has been modeled with the help of DFT calculations, which have also demonstrated that the transformation of amidinate-tetrylene ligands on the dicobalt framework is negligibly influenced by the nature of the group-14 metal atom (Si or Ge) but is strongly dependent upon the volume of the amidinate NR groups. The disubstituted derivatives [Co2 {κ(1) MM(R2 bzam)(HMDS)}2 (CO)6 ] (8: M=Ge, R=iPr; 9: M=Si, R=tBu; 10: M=Ge, R=tBu), which contain two terminal κ(1) M-tetrylene ligands, have been prepared by treating [Co2 (CO)8 ] with two equiv of 1-3 at 20 °C. The IR spectra of 8-10 have shown that the basicity of germylenes 1 and 3 is very high (comparable to that of trialkylphosphanes and 1,3-diarylimidazol-2-ylidenes), whereas that of silylene 2 is even higher.

Conversion of a monodentate amidinate-germylene ligand into chelating imine-germanate ligands (on mononuclear manganese complexes).

The unprecedented transformation of a terminal two-electron-donor amidinate-germylene ligand into a chelating three-electron-donor κ(2)-N,Ge-imine-germanate ligand has been achieved by treating the manganese amidinate-germylene complex [MnBr{Ge((i)Pr2bzam)(t)Bu}(CO)4] (1; (i)Pr2bzam = N,N'-bis(isopropyl)benzamidinate) with LiMe or Ag[BF4]. In these reactions, which afford [Mn{κ(2)Ge,N-GeMe((i)Pr2bzam)(t)Bu}(CO)4] (2) and [Mn{κ(2)Ge,N-GeF((i)Pr2bzam)(t)Bu}(CO)4] (3), respectively, the anionic nucleophile, Me(-) or F(-), ends on the Ge atom while an arm of the amidinate fragment migrates from the Ge atom to the Mn atom. In contrast, the reaction of 1 with AgOTf (OTf = triflate) leads to [Mn(OTf){Ge((i)Pr2bzam)(t)Bu}(CO)4] (4), which maintains intact the amidinate-germylene ligand. Complex 4 is very moisture-sensitive, leading to [Mn2{µ-κ(4)Ge2,O2-Ge2(t)Bu2(OH)2O}(CO)8] (5) and [(i)Pr2bzamH2]OTf (6) in wet solvents. In 5, a novel digermanate(II) ligand, [(t)Bu(OH)GeOGe(OH)(t)Bu](2-), doubly bridges two Mn(CO)4 units. The structures of 1-6 have been characterized by spectroscopic (IR, NMR) and single-crystal X-ray diffraction methods.

Synthesis and reactivity of cationic triruthenium clusters derived from 2-methyl- and 4-methylpyrimidines: from conventional cyclometalated ligands to novel types of N-heterocyclic carbenes.

The methylation of the uncoordinated nitrogen atom of the cyclometalated triruthenium cluster complexes [Ru(3)(µ-H)(µ-κ(2)N(1),C(6)-2-Mepyr)(CO)(10)] (1; 2-MepyrH = 2-methylpyrimidine) and [Ru(3)(µ-H)(µ-κ(2)N(1),C(6)-4-Mepyr)(CO)(10)] (9; 4-MepyrH = 4-methylpyrimidine) gives two similar cationic complexes, [Ru(3)(µ-H)(µ-κ(2)N(1),C(6)-2,3-Me(2)pyr)(CO)(10)](+) (2(+)) and [Ru(3)(µ-H)(µ-κ(2)N(1),C(6)-3,4-Me(2) pyr)(CO)(10)](+) (9(+)), respectively, whose heterocyclic ligands belong to a novel type of N-heterocyclic carbenes (NHCs) that have the C(carbene) atom in 6-position of a pyrimidine framework. The position of the C-methyl group in the ligands of complexes 2(+) (on C(2)) and 9(+) (on C(4)) is of key importance for the outcome of their reactions with K[N(SiMe(3))(2)], K-selectride, and cobaltocene. Although these reagents react with 2(+) to give [Ru(3)(µ-H)(µ-κ(2)N(1),C(6)-2-CH(2)-3-Mepyr)(CO)(10)] (3; deprotonation of the C(2)-Me group), [Ru(3)(µ-H)(µ(3)-κ(3)N(1),C(5),C(6)-4-H-2,3-Me(2)pyr)(CO)(9)] (4; hydride addition at C(4)), and [Ru(6)(µ-H)(2){µ(6)-κ(6) N(1),N(1'),C(5),C(5'),C(6),C(6')-4,4'-bis(2,3-Me(2)pyr)}(CO)(18)] (5; reductive dimerization at C(4)), respectively, similar reactions with 9(+) have only allowed the isolation of [Ru(3)(µ-H)(µ(3)-κ(2)N(1),C(6)-2-H-3,4-Me(2)pyr)(CO)(9)] (11; hydride addition at C(2)). Compounds 3 and 11 also contain novel six-membered ring NHC ligands. Theoretical studies have established that the deprotonation of 2(+) and 9(+) (that have ligand-based LUMOs) are charge-controlled processes and that both the composition of the LUMOs of these cationic complexes and the steric protection of their ligand ring atoms govern the regioselectivity of their nucleophilic addition and reduction reactions.

Deprotonation of C-alkyl groups of cationic triruthenium clusters containing cyclometalated C-alkylpyrazinium ligands: experimental and computational studies.

The C-alkyl groups of cationic triruthenium cluster complexes of the type [Ru3(µ-H)(µ-κ(2)N(1),C(2)-L)(CO)10](+) (HL represents a generic C-alkyl-N-methylpyrazium species) have been deprotonated to give kinetic products that contain unprecedented C-alkylidene derivatives and maintain the original edge-bridged decacarbonyl structure. When the starting complexes contain various C-alkyl groups, the selectivity of these deprotonation reactions is related to the atomic charges of the alkyl H atoms, as suggested by DFT/natural-bond orbital (NBO) calculations. Three additional electronic properties of the C-alkyl C-H bonds have also been found to correlate with the experimental regioselectivity because, in all cases, the deprotonated C-H bond has the smallest electron density at the bond critical point, the greatest Laplacian of the electron density at the bond critical point, and the greatest total energy density ratio at the bond critical point (computed by using the quantum theory of atoms in molecules, QTAIM). The kinetic decacarbonyl products evolve, under appropriate reaction conditions that depend upon the position of the C-alkylidene group in the heterocyclic ring, toward face-capped nonacarbonyl derivatives (thermodynamic products). The position of the C-alkylidene group in the heterocyclic ring determines the distribution of single and double bonds within the ligand ring, which strongly affects the stability of the neutral decacarbonyl complexes and the way these ligands coordinate to the metal atoms in the nonacarbonyl products. The mechanisms of these decacarbonylation processes have been investigated by DFT methods, which have rationalized the structures observed for the final products and have shed light on the different kinetic and thermodynamic stabilities of the reaction intermediates, thus explaining the reaction conditions experimentally required by each transformation.

Reductive dimerization of triruthenium clusters containing cationic aromatic N-heterocyclic ligands.

The cationic cluster complexes [Ru(3)(mu-H)(mu-kappa(2)N,C-L(1) Me)(CO)(10)](+) (1(+); HL(1) Me=N-methylpyrazinium), [Ru(3)(mu-H)(mu-kappa(2)N,C-L(2) Me)(CO)(10)](+) (2(+); HL(2) Me=N-methylquinoxalinium), and [Ru(3)(mu-H)(mu-kappa(2)-N,C-L(3) Me)(CO)(10)](+) (3(+); HL(3) Me=N-methyl-1,5-naphthyridinium), which contain cationic N-heterocyclic ligands, undergo one-electron reduction processes to become short lived, ligand-centered, trinuclear, radical species (1-3) that end in the formation of an intermolecular C--C bond between the ligands of two such radicals, thus leading to neutral hexanuclear derivatives. These dimerization processes are selective, in the sense that they only occur through the exo face of the bridging ligands of trinuclear enantiomers of the same configuration, as they only afford hexanuclear dimers with rac structures (C(2) symmetry). The following are the dimeric products that have been isolated by using cobaltocene as reducing agent: [Ru(6)(mu-H)(2){mu(6)-kappa(4)N(2),C(2)-(L(1) Me)(2)}(CO)(18)] (5; from 1(+)), [Ru(6)(mu-H)(2){mu(6)-kappa(4)N(2),C(2)-(L(2) Me)(2)}(CO)(18)] (6; from 2(+)), and [Ru(6)(mu-H)(2){mu(4)-kappa(8)N(2),C(6)-(L(3) Me)(2)}(CO)(18)] (7; from 3(+)). The structures of the final hexanuclear products depend on the N-heterocyclic ligand attached to the starting materials. Thus, although both trinuclear subunits of 5 and 6 are face-capped by their bridging ligands, the coordination mode of the ligand of 5 is different from that of the ligand of 6. The trinuclear subunits of 7 are edge-bridged by its bridging ligand. In the presence of moisture, the reduction of 3(+) with cobaltocene also affords a trinuclear derivative, [Ru(3)(mu-H)(mu-kappa(2)N,C-L(3') Me)(CO)(10)] (8), whose bridging ligand (L(3') Me) results from the formal substitution of an oxygen atom for the hydrogen atom (as a proton) that in 3(+) is attached to the C(6) carbon atom of its heterocyclic ligand. The results have been rationalized with the help of electrochemical measurements and DFT calculations, which have also shed light on the nature of the odd-electron species, 1-3, and on the regioselectivity of their dimerization processes. It seems that the sort of coupling reactions described herein requires cationic complexes with ligand-based LUMOs.

A Z-type PGeP pincer germylene ligand in a T-shaped palladium(0) complex.

A dipyrromethane-based germylene decorated with two phosphane groups has been used to prepare an unusual T-shaped palladium(0) containing a PGeP pincer germylene that acts as a Z-type ligand. This compound is a strong reducing reagent, as it has been easily oxidized to germyl-palladium(ii) derivatives with a gold(i) complex, HCl and Ph2S2 through processes that involve formal addition of a bond of the oxidant across the Ge-Pd bond.

Phosphane-functionalized heavier tetrylenes: synthesis of silylene- and germylene-decorated phosphanes and their reactions with Group 10 metal complexes.

The stable phosphane-functionalized heavier tetrylenes E(tBu2bzam)pyrmPtBu2 (E = Si (1Si), Ge (1Ge); tBu2bzam = N,N'-ditertbutylbenzamidinate; HpyrmPtBu2 = ditertbutyl(2-pyrrolylmethyl)phosphane) have been prepared by reacting the amidinatotetrylenes E(tBu2bzam)Cl (E = Si, Ge) with LipyrmPtBu2. The reactions of 1Si and 1Ge with selected M0 and MII (M = Ni, Pd, Pt) metal precursors have allowed the synthesis of square-planar [MCl2{κ2E,P-E(tBu2bzam)pyrmPtBu2}] (M = Ni, Pd, Pt; E = Si, Ge), tetrahedral [Ni{κ2E,P-E(tBu2bzam)pyrmPtBu2}(cod)] (E = Si, Ge; cod = 1,5-cyclooctadiene) and triangular [M{κ2E,P-E(tBu2bzam)pyrmPtBu2}(PPh3)] (M = Pd, Pt; E = Si, Ge) complexes, showing that 1Si and 1Ge are excellent Si,P- and Ge,P-chelating ligands that, due to their large steric bulk, are able to stabilize three-coordinate Pd0 and Pt0 complexes.

Cationic heterocycles as ligands: synthesis and reactivity with anionic nucleophiles of cationic triruthenium clusters containing C-metalated N-methylquinoxalinium or N-methylpyrazinium ligands.

The cationic cluster complexes [Ru3(CO)10(mu-H)(mu-kappa2N,C-L1Me)]+ (3+; HL1=quinoxaline) and [Ru3(CO)10(mu-H)(mu-kappa2N,C-L2Me)]+ (5+; HL2=pyrazine) have been prepared as triflate salts by treatment of their neutral precursors [Ru3(CO)10(mu-H)(mu-kappa2N,C-Ln)] with methyl triflate. The cationic character of their heterocyclic ligands is responsible for their enhanced tendency to react with anionic nucleophiles relative to that of hydrido triruthenium carbonyl clusters that have neutral N-heterocyclic ligands. These clusters react instantaneously with methyl lithium and potassium tris-sec-butylborohydride (K-selectride) to give neutral products that contain novel nonaromatic N-heterocyclic ligands. The following are the products that have been isolated: [Ru3(CO)9(mu-H)(mu3-kappa2N,C-L1Me2)] (6; from 3+ and methyl lithium), [Ru3(CO)9(mu-H)(mu3-kappa2N,C-L1HMe)] (7; from 3+ and K-selectride), [Ru3(CO)9(mu-H)(mu3-kappa2N,C-L2Me2)] (8; from 5+ and methyl lithium), and [Ru3(CO)9(mu-H)(mu3-kappa2N,C-L2HMe)] (11; from 5+ and K-selectride). Whereas the reactions of 3+ lead to products that arise from the attack of the corresponding nucleophile at the C atom of the only CH group adjacent to the N-methyl group, the reactions of 5+ give mixtures of two products that arise from the attack of the nucleophile at one of the C atoms located on either side of the N-methyl group. The LUMOs and the atomic charges of 3+ and 5+ confirm that the reactions of these clusters with anionic nucleophiles are orbital-controlled rather than charge-controlled processes. The N-heterocyclic ligands of all of these neutral products are attached to the metal atoms in nonconventional face-capping modes. Those of compounds 6-8 have the atoms of a ligand C=N fragment sigma-bonded to two Ru atoms and pi-bonded to the other Ru atom, whereas the ligand of compound 11 has a C-N fragment attached to a Ru atom through the N atom and to the remaining two Ru atoms through the C atom. A variable-temperature 1H NMR spectroscopic study showed that the ligand of compound 7 is involved in a fluxional process at temperatures above -93 degrees C, the mechanism of which has been satisfactorily modeled with the help of DFT calculations and involves the interconversion of the two enantiomers of this cluster through a conformational change of the ligand CH(2) group, which moves from one side of the plane of the heterocyclic ligand to the other, and a 180 degrees rotation of the entire organic ligand over a face of the metal triangle.

Mesityl(amidinato)tetrylenes as ligands in iridium(i) and iridium(iii) complexes: silicon versus germanium and simple κ1-coordination versus cyclometallation.

Reactions of the mesityl(amidinato)tetrylenes E(tBu2bzam)Mes (tBu2bzam = N,N'-bis(tert-butyl)benzamidinate; Mes = mesityl; E = Ge (1Ge), Si (1Si)) with the iridium precursors [Ir2(µ-Cl)2(η4-cod)2] (cod = 1,5-cyclooctadiene) and [Ir2Cl2(µ-Cl)2(η5-Cp*)2] (Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl) at room temperature led to simple coordination of the tetrylene in the case of the germylenes ([IrCl(η4-cod){κ1Ge-Ge(tBu2bzam)Mes}] (2Ge) and [IrCl2(η5-Cp*){κ1Ge-Ge(tBu2bzam)Mes}] (3Ge), respectively, but to cyclometallated products in the case of the silylenes ([IrHCl(η4-cod){κ2C,Si-Si(tBu2bzam)CH2C6H2Me2}] (4Si) and [IrCl(η5-Cp*){κ2C,Si-Si(tBu2bzam)CH2C6H2Me2}] (5Si), respectively. While the cyclometallation of the germylene ligand of the iridium(i) complex 2Ge could not be achieved by heating this complex in toluene at 90 °C, a similar treatment of the iridium(iii) complex 3Ge led to [IrCl(η5-Cp*){κ2C,Ge-Ge(tBu2bzam)CH2C6H2Me2}] (5Ge), which is the germanium analogue of 5Si. DFT calculations have shown that the mononuclear κ1E-tetrylene iridium(i) complexes [IrCl(η4-cod){κ1E-E(tBu2bzam)Mes}] (E = Si, Ge; isolated only for E = Ge, 2Ge) should not participate as intermediates in the synthesis of the cyclometallated iridium(iii) derivatives [IrHCl(η4-cod){κ2C,E-E(tBu2bzam)(CH2C6H2Me2)}] (E = Ge, Si; isolated only for E = Si, 4Si).

Synthesis and some coordination chemistry of the PSnP pincer-type stannylene Sn(NCH2PtBu2)2C6H4, attempts to prepare the PSiP analogue, and the effect of the E atom on the molecular structures of E(NCH2PtBu2)2C6H4 (E = C, Si, Ge, Sn).

The non-donor-stabilized PSnP pincer-type stannylene Sn(NCH2PtBu2)2C6H4 (1) has been prepared by treating SnCl2 with Li2(NCH2PtBu2)2C6H4. All attempts to synthesize the analogous PSiP silylene by reduction of the (previously unknown) silanes SiCl2(NCH2PtBu2)2C6H4 (2), SiHCl(NCH2PtBu2)2C6H4 (3) and SiH(HMDS)(NCH2PtBu2)2C6H4 (4; HMDS = N(SiMe3)2) have been unsuccessful. The almost planar (excluding the tert-butyl groups) molecular structure of stannylene 1 (determined by X-ray crystallography) has been rationalized with the help of DFT calculations, which have shown that, in the series of diphosphanetetrylenes E(NCH2PtBu2)2C6H4 (E = C, Si, Ge, Sn), the most stable conformation of the compounds with E = Ge and Sn has both P atoms very close to the EN2C6H4 plane, near (interacting with) the E atom, whereas for the compounds with E = C and Si, both phosphane groups are located at one side of the EN2C6H4 plane and far away from the E atom. The size of the E atom and the strength of stabilizing donor-acceptor PE interactions (both increase on going down in group 14) are key factors in determining the molecular structures of these diphosphanetetrylenes. The syntheses of the chloridostannyl complexes [Rh{κ2Sn,P-SnCl(NCH2PtBu2)2C6H4}(η4-cod)] (5), [RuCl{κ2Sn,P-SnCl(NCH2PtBu2)2C6H4}(η6-cym)] (6) and [IrCl{κ2Sn,P-SnCl(NCH2PtBu2)2C6H4}(η5-C5Me5)] (7) have demonstrated the tendency of stannylene 1 to insert its Sn atom into M-Cl bonds of transition metal complexes and the preference of the resulting PSnP chloridostannyl group to act as a κ2Sn,P-chelating ligand, maintaining an uncoordinated phosphane fragment. X-ray diffraction data (of 6), 31P{1H} NMR data (of 5-7) and DFT calculations (on 6) are consistent with the existence of a weak PSn interaction involving the non-coordinated P atom of complexes 5-7, similar to that found in stannylene 1.

Octahedral manganese(i) and ruthenium(ii) complexes containing 2-(methylamido)pyridine-borane as a tripod κ3N,H,H-ligand.

The borane adduct of the 2-(methylamido)pyridine anion, [mapyBH3]-, has been incorporated into octahedral metal complexes. In fac-[Mn(κ3N,H,H-mapyBH3)(CO)3] (1) and fac-[RuH(κ3N,H,H-mapyBH3)(CO)(PiPr3)] (2), which have been prepared by treating K[mapyBH3] with fac-[MnBr(MeCN)2(CO)3] and [RuHCl(CO)(PiPr3)2], respectively, it behaves as a tripod ligand, attached to the metal atom through the amido N atom and through two H atoms of the BH3 moiety. X-ray diffraction analyses and theoretical studies (DFT, QTAIM) have shown that the MH2B atom grouping of 1 and 2 comprises two 3c-2e M-H-B interactions that are between those of the Shimoi type (κ1H coordination of the B-H bond) and those of the agostic type (κ2B,H coordination of the B-H bond). However, while both M-H-B interactions are almost identical in complex 1, this is not the case in complex 2, in which one M-H-B interaction is more agostic than the other due to the different trans influence of the hydride and phosphane ligands.

Synthesis and initial transition metal chemistry of the first PGeP pincer-type germylene.

A PGeP pincer-type germylene, Ge(NCH2PtBu2)2C6H4, which contains two phosphane groups hanging from the N atoms of an N-heterocyclic germylene fragment, has been isolated for the first time. This compound has already furnished a rich transition metal derivative chemistry (Co, Rh, and Pd) that includes complexes containing bridging P,Ge,P-, chelating P,Ge- and pincer P,Ge,P-ligands.

Easy abstraction of a hydride anion from an alkyl C-H bond of a coordinated bis(N-heterocyclic carbene).

The high basicity of a trimethylene-linked bis(NHC), acting as a chelating ligand in a ruthenium(0) complex, is responsible for its involvement in a room-temperature reaction in which the metal atom to which this bis(NHC) ligand is coordinated replaces a hydride anion of the ligand trimethylene linker, which can be taken by a hydride abstractor as unusual, in that role, as [Ru3(CO)12].