Electrophilic As-functionalisation of σ-arsolido complexes.

The σ-arsolido complex [Mo(AsC4Me4)(CO)3(η5-C5H5)] is alkylated at arsenic by MeOTf to afford the pentamethylarsole complex [Mo(MeAsC4Me4)(CO)3(η5-C5H5)](OTf) while iodomethane affords a mixture of [Me2AsC4Me4]I, [MoMe(CO)3(η5-C5H5)], [MoI(CO)3(η5-C5H5)] and the arsole complexes cisoid- and transoid-[MoI(MeAsC4Me4)(CO)2(η5-C5H5)] and transoid-[Mo{C(O)Me}(MeAsC4Me4)(CO)2(η5-C5H5)], The arsole ligand in [Mo(MeAsC4Me4)(CO)3(η5-C5H5)](OTf) is readily liberated by NaI in acetone to afford free MeAsC4Me4 and [MoI(CO)3(η5-C5H5)]. In a similar manner, the reaction of [Mo(AsC4Ph4)(CO)3(η5-C5H5)] with MeI affords MeAsC4Ph4 and [MoI(CO)3(η5-C5H5)], while [Mo{AsC4(SiMe3)-2-Me2-3,4}(CO)3(η5-C5H5)] with MeOTf affords [Mo{MeAsC4(SiMe3)-2-Me2-3,4}(CO)3(η5-C5H5)](OTf). The reaction of [Mo(AsC4Me4)(CO)3(η5-C5H5)] with activated alkynes (RCCR: R = CF3, CO2Me) does not proceed via [4 + 2] cyclo-addition but rather electrophilic attack at arsenic followed by metallacyclisation with incorporation of a carbonyl ligand in the spirocyclic complexes [Mo{As(C4Me4)CRCRCO}(CO)2(η5-C5H5)].

σ-Arsolido complexes.

The σ-stannyl complexes [M(SnnBu3)(CO)n(η5-C5H5)] (n = 3, M = Mo, W; n = 2, M = Fe) serve as mild reagents for the installation of σ-arsolyl ligands in transmetallation reactions with As-chloro-arsoles ClAsC4R4 (R = Me, Ph) to afford [M(σ-AsC4R4)(CO)n(η5-C5H5)]. The reaction of [Cr(SnnBu3)(CO)3(η5-C5H5)] with ClAsC4Ph4 most likely proceeds in a similar manner but is immediately followed by rapid formation of (AsC4Ph4)2 and [Cr2(CO)6(η5-C5H5)2]. The reaction of [Mo(SnnBu3)(CO)3(η5-C5H5)] with ClAsC4(SiMe3)-2,5-Me2-3,4 is accompanied by monodesilylation to afford [Mo{σ-AsC4(SiMe3)-2-Me2-3,4}(CO)3(η5-C5H5)]. The slow reaction of [Fe(SnnBu3)(CO)2(η5-C5H5)] with ClAsC4Me4 produced only traces of [Fe(σ-AsC4Me4)(CO)2(η5-C5H5)] due to competition with the Diels-Alder type dimerisation of the haloarsole. Although attempts to decarbonylate the σ-arsolyl complexes were unsuccessful, computational analysis suggests that the trigonal 'XL' arsolenium coordination mode is viable.

Carbon-chalcogen wires: alkynyltellurolatocarbynes.

The reactions of [W(CBr)(CO)2(Tp*)] (Tp* = tris(dimethylpyrazolyl)borate) with LiTeCCR (R = SiMe3, SiiPr3, iPr, nBu, tBu, Ph, C6H4Me-4, methylimidazol-2-yl) afford the first alkynyltellurolatocarbynes [W(CTeCCR)(CO)2(Tp*)]. Both the WC and CC multiple bonds are prone to metal addition as exemplified by treatment with [MCl(SMe2)] (M = Cu, Au) to afford the hexametallic complex [W2Cu4(µ-CTeCCSiiPr3)2Cl4(CO)4(Tp*)2] and [WAu(µ-CTeCCSiMe3)Cl(CO)2-(Tp*)] which evolves to the unusual hypervalent [WAu(µ-CTeCl4)(SMe2)(CO)2(Tp*)].

Spodium bonding in bis(alkynyl)mecurials.

The new bis(alkynyl)mercurial Hg{CCSeCW(CO)2(Tp*)}2 (Tp* = tris(dimethylpyrazolyl)borate) forms adducts with fluoride and phenathroline, the structures of which are interpreted in the context of two-coordinate mercury presenting a σ-torroid for spodium bonding.

Stable cyclopropenylvinyl ligands via insertion into a transient cyclopropenyl metal bond.

Treatment of the rhodium pincer complexes [RhCl(RPm)] (RPm = N,N'-bis(di-R-phosphinomethyl)perimidinylidene, R = Ph, Cy) with triphenylcyclopropenium hexafluorophosphate affords rhodacyclobutadiene complexes. These in turn react with activated alkynes (RCCCO2Me, R = H, CO2Me) to afford unusually stable cyclopropenylvinyls, implicating the intermediacy of σ-cyclopropenyl isomers. In contrast, treatment of [RhCl{py(NHPtBu2)2-2,6}] with the same reagent instead results in double functionalisation (SEAr) at the pincer backbone.

Poly(imidazolyliden-yl)borato Complexes of Tungsten: Mapping Steric vs. Electronic Features of Facially Coordinating Ligands.

A convenient synthesis of [HB(HImMe)3](PF6)2 (ImMe = N-methylimidazolyl) is decribed. This salt serves in situ as a precursor to the tris(imidazolylidenyl)borate Li[HB(ImMe)3] pro-ligand upon deprotonation with nBuLi. Reaction with [W(≡CC6H4Me-4)(CO)2(pic)2(Br)] (pic = 4-picoline) affords the carbyne complex [W(≡CC6H4Me-4)(CO)2{HB(ImMe)3}]. Interrogation of experimental and computational data for this compound allow a ranking of familiar tripodal and facially coordinating ligands according to steric (percentage buried volume) and electronic (νCO) properties. The reaction of [W(≡CC6H4Me-4)(CO)2{HB(ImMe)3}] with [AuCl(SMe2)] affords the heterobimetallic semi-bridging carbyne complex [WAu(µ-CC6H4Me-4)(CO)2(Cl){HB(ImMe)3}].

Free and coordinated biarsolyls.

A trace side product from the reaction of [Mo(AsC4Me4)(CO)3(η-C5H5)] with [Mn(THF)(CO)2(η5-C5H4Me)] was identified as the biarsolyl complex [Mn2{µ-(AsC4Me4)2}(CO)4(C5H4Me)2] on the basis of a strategic synthesis from [Mn(THF)(CO)2(η5-C5H4Me)] and the pre-formed and structurally characterised biarsolyl (AsC4Me4)2. Crystallographic and computational data for this first example of a biarsolyl complex and free biarsolyls are discussed in the context of those for free biarsolyls.

Isonitrile µ2-carbido complexes.

The µ-carbido complex [WPt(µ-C)Br(CO)2(PPh3)2(Tp*)] (Tp = hydrotris(dimethylpyrazolyl)borate) undergoes substitution of one phosphine ligand with isonitriles to afford complexes [WPt(µ-C)Br(CNR)(CO)2(PPh3)(Tp*)] (R = tBu, C6H3Me2-2,6, C6H2Me3-2,4,6). For aryl but not alkyl isocyanides disubstitution follows to afford [WPt(µ-C)Br(CNR)2(CO)2(Tp*)] (R = C6H2Me2-2,6, C6H2Me3-2,4,6). The bis(isonitrile) derivatives, including [WPt(µ-C)Br(CNtBu)2(CO)2(Tp*)], may also be prepared from the reactions of triangulo-[Pt3(CNR)6] with [W(CBr)(CO)2(Tp*)]. Bis- and tris(dimethylpyrazolyl)borate pro-ligand salts replace the bromide and one phosphine in [WPt(µ-C)Br(CNC6H2Me3)(CO)2(PPh3)(Tp*)] or the bromide and one isonitrile in [WPt(µ-C)Br(CNC6H2Me3)2(CO)2(Tp*)] to afford [WPt(µ-C)(CNC6H2Me3)(CO)2(Tp*)(L)] (L = κ2-Tp*, dihydrobis(pyrazolyl)borate). Structural, spectroscopic and computational data for the complexes are discussed to interrogate the nature of the WC-Pt carbido bridge by analogy with a range of other sp-C1 and sp-B1 ligands (CN, CCH, CP, CAs, CSb, CNO, BO, BNH and BCH2).

Bridging arsolido complexes.

The σ-arsolyl complex [Mo(AsC4Me4)(CO)3(η-C5H5)] serves as a metallo-ligand for the strategic construction of µ-arsolido bridged heterobimetallic complexes [MoCr(µ-AsC4Me4)(CO)8(η5-C5H5)], [MoMn(µ-AsC4Me4)(CO)5(η5-C5H5)(η5-C5H4Me)], [MoAu(µ-AsC4Me4)(C6F5)(CO)3(η5-C5H5)] and [MoFe(µ-AsC4Me4)(CO)5(η5-C5H5)2]PF6via reactions with [Cr(THF)(CO)5], [Au(C6F5)(THT)], [Mn(THF)(CO)2(η5-C5H4Me)] and [Fe(THF)(CO)2(η5-C5H5)]PF6, respectively. The reaction of [Mo(AsC4Me4)(CO)3(η-C5H5)] with [Co3(µ3-CH)(CO)9] affords the tetrametallic species [MoCo3(AsC4Me4)(µ3-CH)(CO)11(η-C5H5)]. Crystallographic and computational data for all products are discussed.

A Metallabicycle From Thiocarbonyl-Cyclopropenium Coupling.

Addition of triphenylcyclopropenium bromide to the thiocarbonyl complex [RhCl(CS)(PPh3 )2 ] affords novel bicyclic metalla-3-mercapto-thiapyrylliums [Rh(κ2 -C,S-C5 S2 Ph3 )(PPh3 )2 X2 ] (X=Cl, Br) - heterocycles with no metal-free isolobal precedent. Halide abstraction with silver triflate (AgOTf) in acetonitrile affords the salt [Rh(κ2 -C,S-C5 S2 Ph3 )(NCMe)2 (PPh3 )2 {Ag(OH2 )2 }{Ag(OTf)3 }]-OTf which in turn reacts with sodium chloride to return [Rh(κ2 -C,S-C5 S2 Ph3 )(PPh3 )2 Cl2 ].

Fluorocarbyne complexes via electrophilic fluorination of carbido ligands.

The new fluorocarbynes [M([triple bond, length as m-dash]CF)(CO)2(Tp*)] (M = Mo, W; Tp* = tris(dimethylpyrazolyl)borate) arise from electrophilic fluorination of the lithiocarbynes [M([triple bond, length as m-dash]CLi)(CO)2(Tp*)] with FN(SO2Ph)2. The reactions of [W([triple bond, length as m-dash]CF)(CO)2(Tp*)] with [AuCl(SMe2)] and PhICl2 afford the first µ2-fluorocarbyne complex [WAu(µ-CF)Cl(CO)2(Tp*)] and the first high oxidation state fluorocarbyne [W([triple bond, length as m-dash]CF)Cl2(Tp*)], respectively.

Synthesis and reactivity of 9,10-bis(4-trimethylsilylethynylbuta-1,3-diynyl)anthracene derived chromophores.

9,10-Bis(4-trimethylsilylethynylbutadiynyl)anthracene is readily availabe from the reaction of anthraquinone and LiCCCCSiMe3 followed by reduction with Sn(II) and serves as a convenient building block via desilylation and palladium-mediated C-C coupling processes for the construction of further butadiynylanthracenes terminated by metal complexes, arenes, haloarenes and alkynyl functionalities.

C-H activation in bimetallic rhodium complexes to afford N-heterocyclic carbene pincer complexes.

The pro-ligands 1,8-bis(di-R-phosphinomethyl)-2,3-dihydroperimidine (RH2Pm, R = phenyl, cyclohexyl) react with [RhCl(CE)(PPh3)2] (E = O, S) to afford the bimetallic complexes [RhCl(CE)(µ-RH2Pm)]2 (E = O, S). Upon heating, these species undergo double C-H activation to afford the N-heterocyclic carbene (NHC) pincer complexes [RhCl(RPm)]. Reduction of [RhCl(CO)(µ-PhH2Pm)]2 with KC8 results in the bimetallic rhodium(0) complex, [Rh(µ-CO)(PhH2Pm)]2, with a formal Rh-Rh bond and a hydrogen-bonding interaction between rhodium and the central methylene group (C-H⋯Rh = 2.802 Å). Upon treatment with tritylium, ferrocenium or triphenylcyclopropenium tetrafluoroborates this species undergoes double C-H activation to afford a mononuclear NHC pincer complex salt, [Rh(CO)(PhPm)]BF4. Treatment of [RhCl(CO)(PhH2Pm)]2 with lithium (trimethylsilyl)acetylide provides another bimetallic species, [Rh(CCSiMe3)(CO)(PhH2Pm)]2, however heating this species does not proceed cleanly to the monomeric NHC complex, [Rh(CCSiMe3)(CO)(PhPm)] which may however be obtained from [RhCl(RPm)] and LiCCSiMe3.

Organometallic flow chemistry: solvento complexes.

Photolysis under optimised flow conditions of metal carbonyls [{Ln}M(CO)x] [{Ln}M(CO)x = Cr(CO)6, Mo(CO)6, W(CO)6, Mn(CO)3(η-C5H4Me), Re(CO)3(η-C5H5)] in tetrahydrofuran (THF) conveniently affords the synthetically versatile and labile solvento complexes [{Ln}M(CO)x-1(THF)], thereby obviating many of the caveats associated with photochemical syntheses using either 'batch' or falling film techniques. Conversions were optimised and yields assayed by a combination of in situ infrared spectroscopy and derivatisation as the corresponding triphenylphosphine complexes [{Ln}M(CO)x-1(PPh3)].

Thiocarbonylphosphorane and arsorane ligands.

Independently unstable thiocarbonylphosphorane or arsorane ligands SCAR3 (A = P, As) are observed in the salts [W(η2-C,S-SCAR3)(CO)2(Tp*)]PF6 [AR3 = PCy3, PMenPh3-n: n = 0, 1, 2, AsMePh2; Tp* = tris(dimethylpyrazolyl)borate] which arise from the reactions of phosphonio- or arsoniocarbynes [W(≡CAR3)(CO)2(Tp*)]+ with sulfur.

Heterobimetallic µ2-halocarbyne complexes.

The halocarbyne complexes [M(CX)(CO)2(Tp*)] (M = Mo, W; X = Cl, Br; Tp* = hydrotris(dimethylpyrazolyl)borate) react with [AuCl(SMe2)], [Pt(η2-H2CCH2)(PPh3)2] or [Pt(η2-nbe)3] (nbe = norbornene) to furnish rare examples of µ2-halocarbyne complexes [MAu(µ2-CX)Cl(CO)2(Tp*)], [MPt(µ2-CCl)(CO)2(PPh3)2(Tp*)] and [W2Pt(µ2-CCl)2(CO)4(Tp*)2]. The complex [WPt(µ2-CCl)(CO)2(PPh3)2(Tp*)] spontaneously rearranges to the µ2-carbido complex [WPt(µ2-C)Cl(CO)2(PPh3)2(Tp*)] during silica-gel chromatography. One phosphine ligand of [WPt(µ2-CCl)(CO)2(PPh3)2(Tp*)] is readily substituted by CO to afford [WPt(µ2-CCl)(CO)3(PPh3)(Tp*)]. These µ2-halocarbyne complexes have been interrogated by spectroscopic, crystallographic and computational methods, the latter by reference to data for terminal halocarbyne precursors [M(CX)(CO)2(Tp*)].

Arsolyl-supported intermetallic dative bonding.

The first examples of late transition metal η5-arsolyls (L = CO, P(OMe)3; R = Ph, Me, Et, SiMe3; R' = Ph, H, Me, Et, Me) serve as ditopic donors to extraneous metal centres (M = PtII, AuI, HgII) through both conventional As → M and polar-covalent (dative) Co → M interactions.

Arsinocarbyne reactivity.

The reactivity of the tungsten diphenylarsinocarbyne [W(CAsPh2)(CO)2(Tp*)] (1; Tp* = hydrotris(dimethylpyrazolyl)borato) is described. The pyramidal arsenic coordinates to a selection of 5d metal centres, forming heterobi- or trimetallic complexes with osmium(II), iridium(III), platinum(II) and gold(I). In the latter case, the WC bond provides a competitive site for gold(I) coordination. Treatment with MeOSO2CF3 results in methylation at arsenic to give the first example of an arsoniocarbyne, [W(CAsPh2CH3)(CO)2(Tp*)]O3SCF3, for which only the WC bond remains available for gold(I) coordination.

Bimetallic ethynylanthracenyl functionalised carbynes.

Mono- and bimetallic anthracenes functionalised by alkynyl and alkylidynyl substituents are obtained via sequential cross-coupling reactions of the 9-bromoanthracenyl carbyne [W{CC(C6H4)2CBr}(CO)2(Tp*)].

Symmetric and non-symmetric anthracen-diyl bis(alkylidynes).

Three examples of 9-bromo-10-(alkylidynyl)anthracenes, [W{CC(C6H4)2CBr}(CO)2(L)] (L = hydrotris(dimethylpyrazol-1-yl)borate Tp*, hydrotris(pyrazol-1-yl)borate Tp, hydrotris(2-mercapto-N-methylimidazol-1-yl)borate Tm) were prepared via modified Fischer-Mayr acyl oxide-abstraction protocols. With a sufficiently bulky ancillary ligand (L = Tp*) the aryl bromide is ammenable to cross-coupling reactions that enable more elaborate derivatives to be prepared. These including symmetric bis(alkylidynyl)anthracenes as well as non-palindromic examples bearing disparate metals and/or co-ligands. In contrast, these couplings fail for smaller ligands (L = Tp, Tm) where it was found that Pd0 or Pt0 were instead able to coordinate across two WC bonds to give trimetallic bow-tie complexes, [W2M{µ-CC(C6H4)2CBr}2(CO)4(L)2] (M = Pd, Pt; L = Tp, Tm).