The Interplay of Methylidyne and Carbido Species: Modeling a Fundamental Step in the Fischer-Tropsch Synthesis.

Heterobimetallic μ-methylidyne complexes [WPt(μ2-CH)(CO)2L2(Tp*)], where L2 = (PPh3)2, (PPh3)(CO), (dppe), (PPh3)(CNC6H2Me3), have been obtained via the intermediacy of transient hydrido-μ-carbido complexes that undergo carbido-hydrido coupling to model a fundamental step in the proposed mechanism for Fischer-Tropsch synthesis.

Electrophilic As-functionalisation of σ-arsolido complexes.

The σ-arsolido complex [Mo(AsCMe)(CO)(η-CH)] is alkylated at arsenic by MeOTf to afford the pentamethylarsole complex [Mo(MeAsCMe)(CO)(η-CH)](OTf) while iodomethane affords a mixture of [MeAsCMe]I, [MoMe(CO)(η-CH)], [MoI(CO)(η-CH)] and the arsole complexes - and -[MoI(MeAsCMe)(CO)(η-CH)] and -[Mo{C(O)Me}(MeAsCMe)(CO)(η-CH)], The arsole ligand in [Mo(MeAsCMe)(CO)(η-CH)](OTf) is readily liberated by NaI in acetone to afford free MeAsCMe and [MoI(CO)(η-CH)]. In a similar manner, the reaction of [Mo(AsCPh)(CO)(η-CH)] with MeI affords MeAsCPh and [MoI(CO)(η-CH)], while [Mo{AsC(SiMe)-2-Me-3,4}(CO)(η-CH)] with MeOTf affords [Mo{MeAsC(SiMe)-2-Me-3,4}(CO)(η-CH)](OTf). The reaction of [Mo(AsCMe)(CO)(η-CH)] with activated alkynes (RCCR: R = CF, COMe) does not proceed [4 + 2] -addition but rather electrophilic attack at arsenic followed by metallacyclisation with incorporation of a carbonyl ligand in the spirocyclic complexes [Mo{As(CMe)CRCRCO}(CO)(η-CH)].

σ-Arsolido complexes.

The σ-stannyl complexes [M(SnBu)(CO)(η-CH)] ( = 3, M = Mo, W; = 2, M = Fe) serve as mild reagents for the installation of σ-arsolyl ligands in transmetallation reactions with As-chloro-arsoles ClAsCR (R = Me, Ph) to afford [M(σ-AsCR)(CO)(η-CH)]. The reaction of [Cr(SnBu)(CO)(η-CH)] with ClAsCPh most likely proceeds in a similar manner but is immediately followed by rapid formation of (AsCPh) and [Cr(CO)(η-CH)]. The reaction of [Mo(SnBu)(CO)(η-CH)] with ClAsC(SiMe)-2,5-Me-3,4 is accompanied by monodesilylation to afford [Mo{σ-AsC(SiMe)-2-Me-3,4}(CO)(η-CH)].

Carbon-chalcogen wires: alkynyltellurolatocarbynes.

The reactions of [W(CBr)(CO)(Tp*)] (Tp* = tris(dimethylpyrazolyl)borate) with LiTeCCR (R = SiMe, SiPr, Pr, Bu, Bu, Ph, CHMe-4, methylimidazol-2-yl) afford the first alkynyltellurolatocarbynes [W(CTeCCR)(CO)(Tp*)]. Both the WC and CC multiple bonds are prone to metal addition as exemplified by treatment with [MCl(SMe)] (M = Cu, Au) to afford the hexametallic complex [WCu(μ-CTeCCSiPr)Cl(CO)(Tp*)] and [WAu(μ-CTeCCSiMe)Cl(CO)-(Tp*)] which evolves to the unusual hypervalent [WAu(μ-CTeCl)(SMe)(CO)(Tp*)].

Spodium bonding in bis(alkynyl)mecurials.

The new bis(alkynyl)mercurial Hg{CCSeCW(CO)(Tp*)} (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 insertion into a transient cyclopropenyl metal bond.

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

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

A convenient synthesis of [HB(HImMe)](PF) (ImMe = -methylimidazolyl) is decribed. This salt serves in situ as a precursor to the tris(imidazolylidenyl)borate Li[HB(ImMe)] pro-ligand upon deprotonation with BuLi. Reaction with [W(≡CCHMe-4)(CO)(pic)(Br)] (pic = 4-picoline) affords the carbyne complex [W(≡CCHMe-4)(CO){HB(ImMe)}].

Isonitrile μ-carbido complexes.

The μ-carbido complex [WPt(μ-C)Br(CO)(PPh)(Tp*)] (Tp = hydrotris(dimethylpyrazolyl)borate) undergoes substitution of one phosphine ligand with isonitriles to afford complexes [WPt(μ-C)Br(CNR)(CO)(PPh)(Tp*)] (R = Bu, CHMe-2,6, CHMe-2,4,6). For aryl but not alkyl isocyanides disubstitution follows to afford [WPt(μ-C)Br(CNR)(CO)(Tp*)] (R = CHMe-2,6, CHMe-2,4,6). The bis(isonitrile) derivatives, including [WPt(μ-C)Br(CNBu)(CO)(Tp*)], may also be prepared from the reactions of -[Pt(CNR)] with [W(CBr)(CO)(Tp*)].

Free and coordinated biarsolyls.

A trace side product from the reaction of [Mo(AsCMe)(CO)(η-CH)] with [Mn(THF)(CO)(η-CHMe)] was identified as the biarsolyl complex [Mn{μ-(AsCMe)}(CO)(CHMe)] on the basis of a strategic synthesis from [Mn(THF)(CO)(η-CHMe)] and the pre-formed and structurally characterised biarsolyl (AsCMe). 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.

Bridging arsolido complexes.

The σ-arsolyl complex [Mo(AsCMe)(CO)(η-CH)] serves as a metallo-ligand for the strategic construction of μ-arsolido bridged heterobimetallic complexes [MoCr(μ-AsCMe)(CO)(η-CH)], [MoMn(μ-AsCMe)(CO)(η-CH)(η-CHMe)], [MoAu(μ-AsCMe)(CF)(CO)(η-CH)] and [MoFe(μ-AsCMe)(CO)(η-CH)]PF reactions with [Cr(THF)(CO)], [Au(CF)(THT)], [Mn(THF)(CO)(η-CHMe)] and [Fe(THF)(CO)(η-CH)]PF, respectively. The reaction of [Mo(AsCMe)(CO)(η-CH)] with [Co(μ-CH)(CO)] affords the tetrametallic species [MoCo(AsCMe)(μ-CH)(CO)(η-CH)]. 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)(PPh ) ] affords novel bicyclic metalla-3-mercapto-thiapyrylliums [Rh(κ -C,S-C S Ph )(PPh ) X ] (X=Cl, Br) - heterocycles with no metal-free isolobal precedent. Halide abstraction with silver triflate (AgOTf) in acetonitrile affords the salt [Rh(κ -C,S-C S Ph )(NCMe) (PPh ) {Ag(OH ) }{Ag(OTf) }]-OTf which in turn reacts with sodium chloride to return [Rh(κ -C,S-C S Ph )(PPh ) Cl ].

Fluorocarbyne complexes electrophilic fluorination of carbido ligands.

The new fluorocarbynes [M([triple bond, length as m-dash]CF)(CO)(Tp*)] (M = Mo, W; Tp* = tris(dimethylpyrazolyl)borate) arise from electrophilic fluorination of the lithiocarbynes [M([triple bond, length as m-dash]CLi)(CO)(Tp*)] with FN(SOPh). The reactions of [W([triple bond, length as m-dash]CF)(CO)(Tp*)] with [AuCl(SMe)] and PhICl afford the first μ-fluorocarbyne complex [WAu(μ-CF)Cl(CO)(Tp*)] and the first high oxidation state fluorocarbyne [W([triple bond, length as m-dash]CF)Cl(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CSiMe followed by reduction with Sn(II) and serves as a convenient building block 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 (RHPm, R = phenyl, cyclohexyl) react with [RhCl(CE)(PPh)] (E = O, S) to afford the bimetallic complexes [RhCl(CE)(μ-RHPm)] (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-PhHPm)] with KC results in the bimetallic rhodium(0) complex, [Rh(μ-CO)(PhHPm)], with a formal Rh-Rh bond and a hydrogen-bonding interaction between rhodium and the central methylene group (C-H⋯Rh = 2.

Organometallic flow chemistry: complexes.

Photolysis under optimised flow conditions of metal carbonyls [{L}M(CO)] [{L}M(CO) = Cr(CO), Mo(CO), W(CO), Mn(CO)(η-CHMe), Re(CO)(η-CH)] in tetrahydrofuran (THF) conveniently affords the synthetically versatile and labile complexes [{L}M(CO)(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 infrared spectroscopy and derivatisation as the corresponding triphenylphosphine complexes [{L}M(CO)(PPh)].

Thiocarbonylphosphorane and arsorane ligands.

Independently unstable thiocarbonylphosphorane or arsorane ligands SCAR (A = P, As) are observed in the salts [W(η-,-SCAR)(CO)(Tp*)]PF [AR = PCy, PMePh: = 0, 1, 2, AsMePh; Tp* = tris(dimethylpyrazolyl)borate] which arise from the reactions of phosphonio- or arsoniocarbynes [W(≡CAR)(CO)(Tp*)] with sulfur.

Heterobimetallic μ-halocarbyne complexes.

The halocarbyne complexes [M(CX)(CO)(Tp*)] (M = Mo, W; X = Cl, Br; Tp* = hydrotris(dimethylpyrazolyl)borate) react with [AuCl(SMe)], [Pt(η-HCCH)(PPh)] or [Pt(η-nbe)] (nbe = norbornene) to furnish rare examples of μ-halocarbyne complexes [MAu(μ-CX)Cl(CO)(Tp*)], [MPt(μ-CCl)(CO)(PPh)(Tp*)] and [WPt(μ-CCl)(CO)(Tp*)]. The complex [WPt(μ-CCl)(CO)(PPh)(Tp*)] spontaneously rearranges to the μ-carbido complex [WPt(μ-C)Cl(CO)(PPh)(Tp*)] during silica-gel chromatography. One phosphine ligand of [WPt(μ-CCl)(CO)(PPh)(Tp*)] is readily substituted by CO to afford [WPt(μ-CCl)(CO)(PPh)(Tp*)].

Arsolyl-supported intermetallic dative bonding.

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

Arsinocarbyne reactivity.

The reactivity of the tungsten diphenylarsinocarbyne [W(CAsPh)(CO)(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.

Bimetallic ethynylanthracenyl functionalised carbynes.

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

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

Three examples of 9-bromo-10-(alkylidynyl)anthracenes, [W{CC(CH)CBr}(CO)(L)] (L = hydrotris(dimethylpyrazol-1-yl)borate Tp*, hydrotris(pyrazol-1-yl)borate Tp, hydrotris(2-mercapto--methylimidazol-1-yl)borate Tm) were prepared 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.

Heterocyclic arsinocarbynes via tandem transmetallation.

Gold(i)-catalysed tandem transmetallation (Sn→Au→As) of the stannylcarbyne [W(≡CSnBu)(CO)(Tp*)] (Tp* = hydrotris-(dimethylpyrazolyl)borate) with haloarsines gives direct access to a range of novel arsinocarbyne complexes, LM≡CAsR, including unusual heterocyclic phenarsazininyl and arsolyl examples.

Construction of an iminoketenylidene.

The new isonitrile-μ-carbido complexes [WPt(μ-C)Br(CNR)(PPh)(CO)(Tp*)] (R = CHMe-2,4,6, CHMe-2,6; Tp* = hydrotris(dimethylpyrazolyl)borate) rearrange irreversibly in polar solvents to provide the first examples of iminoketenylidene (CCNR) complexes.

Benzyne addition to a metal-carbon multiple bond.

The linear μ-carbido complex [Rh2(μ-C)Cl2(dppm)2] (dppm = bis(diphenylphosphino)methane) reacts with a benzyne equivalent (Me3SiC6H4OTf-2/F-) to afford [Rh2(μ-CC6H4)(μ-Cl)(C6H5)Cl2(μ-dppm)2], in which the benzyne moiety adds across one of the two metal-carbon double bonds.

Tetrel and pnictogen functionalised propargylidynes.

The reaction of [W([triple bond, length as m-dash]CC[triple bond, length as m-dash]CSiMe)(CO)(Tp*)] (Tp* = tris(dimethylpyrazolyl)borate) with AgNO affords {[W([triple bond, length as m-dash]CC[triple bond, length as m-dash]CAg)-(CO)(Tp*)][AgNO]} while [Hg{C[triple bond, length as m-dash]CC[triple bond, length as m-dash]W(CO)(Tp*)}] with BuLi affords [W([triple bond, length as m-dash]CC[triple bond, length as m-dash]CLi)(CO)(Tp*)]. These anhydrous reagents allow the installation of main group elements (e.g.