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9,10-Bis(4-trimethylsilylethynyl-butadiynyl)anthracene serves as a convenient building block for the construction of new butadiynyl and hexatriynyl anthracenes terminated by metal complexes, arenes, haloarenes and alkynyl functionalities.

Electrophilic fluorination of lithiocarbynes affords convenient access to fluorocarbyne complexes that are prone to oxidative chlorination and coordination to gold, providing the first μ2-fluorocarbyne.

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).

In-flow photochemical methods allow the convenient synthesis ‘on-demand’ of ubiquitous tetrahydrofuran organometallic solvento complexes, e.g., [M(THF)(CO)5] (M = Cr, Mo, W) and [M(THF)(CO)2(η-L)] (M = Mn, Re; L = C5H5, C5H4Me, C5Me5).

A range of heterobimetallic μ2-halocarbyne complexes arise from the reactions of terminal halocarbyne complexes with gold(i) and platinum(0) reagents.

Photolysis under optimised flow conditions of metal carbonyls [{L

Independently unstable thiocabonylphosphorane ligands SCPR3 are observed in the complexes [W(η2-SCPR3)(CO)2(Tp*)]+ (PR3 = PCy3, PMenPh3−n: n = 0, 1, 2) arising from the reactions of phosphoniocarbynes [W(CPR3)(CO)2(Tp*)]PF6 with sulfur.

The halocarbyne complexes [M(CX)(CO)

The chemistry of transition metal carbynes, Ln M≡CR, has historically been dominated by species bearing hydrocarbyl or amino 'R' substituents, with other elements appearing only sporadically. In recent years, carbynes and related 'C1 ' species bearing other main-group substituents, particularly heavier elements of the p-block, have begun to emerge. This review details the chemistry of heavier pnictogen-functionalised C1 ligands, MCARn (A=P, As, Sb, Bi; n=0-3), including their syntheses, properties and reactivities, and how these are distinguished from more traditional carbyne complexes. Recent developments in the closely related phospha-isonitrile Ln M(CPR), cya-phosphide and cya-arside ligands, Ln M(C≡A) (A=P, As), are also discussed.

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

Gold(I)-catalysed tandem transmetallation (Sn→Au→As) of the stannylcarbyne [W(≡CSnnBu3)(CO)2(Tp*)] (Tp* = hydrotris-(dimethylpyrazolyl)borate) with haloarsines gives direct access to a range of novel arsinocarbyne complexes, LnM≡CAsR2, including unusual heterocyclic phenarsazininyl and arsolyl examples.

The isonitrile-μ-carbido complexes [WPt(μ-C)Br(CNR)(PPh3)(CO)2(Tp*)] (R = C6H2Me3-2,4,6, C6H3Me2-2,6) rearrange irreversibly to provide the first examples of iminoketenylidene (CCNR) complexes.

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.

In contrast to the ubiquity of transition-metal carbonyl, and (to a lesser extent) thiocarbonyl complexes, transition-metal complexes of carbon monoselenide Ln MCSe and monotelluride Ln MCTe remain scarce. The last few years, however, have seen notable steps towards expanding this chemistry, specifically with regards to new systematic studies on homologous sets of chalcocarbonyl complexes Ln MCE (E=O, S, Se, Te), the first reports of new bi- and polynuclear CSe and CTe bridging complexes and a confluence with metal carbido chemistry. Herein the properties, syntheses and reactions of these rare but fundamentally intriguing compounds are discussed.

Cobalt carbonyl reacts with arsoles to provide the first late transition metal η5-arsolyls. These serve as ditopic donors to extraneous metal centres (M = PtII, AuI, HgII) through both conventional AsM and polar-covalent (dative) CoM interactions.

The reactivity of the tungsten diphenylarsinocarbyne [W(CAsPh2)(CO)2(Tp*)] (1; Tp* = hydrotris(dimethylpyrazolyl)borato) is described leading to the first examples of bridging arsino- and arsoniocarbyne complexes.

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 WC bonds to give trimetallic bow-tie complexes, [W2M{μ-CC(C6H4)2CBr}2(CO)4(L)2] (M = Pd, Pt; L = Tp, Tm).

Competent intermediates in palladium(0)-copper(i) mediated catalytic cross coupling reactions of the bromocarbyne complex [W([triple bond, length as m-dash]CBr)(CO)2(Tp*)] (Tp* = hydrotris(dimethylpyrazolyl)borate) have been isolated however heterobimetallic phosphoniocarbyne complexes [WPd(μ-CPPh3)Br(CO)2(PPh3)x(Tp*)] are identified as productive (x = 1) or non-productive (x = 0) tangents to the catalytic cycle.

The reaction of [W(CCCSiMe3)(CO)2(Tp*)] (Tp* = tris(dimethylpyrazolyl)borate) with AgNO3 affords {[W(CCCAg)-(CO)2(Tp*)][AgNO3]}n while [Hg{CCCW(CO)2(Tp*)}2] with nBuLi affords [W(CCCLi)(CO)2(Tp*)]. These anhydrous reagents allow the installation of main group elements (e.g., Si, Sn, Pb, P, As) as propargylidyne termini.

The tungsten-platinum μ-carbido complex [WPt(μ-C)Br(CO)2(PPh3)2(Tp*)] (Tp* = hydrotris(dimethylpyrazol-1-yl)borate) undergoes facile substitution of both bromide and phosphine ligands to afford a diverse library of μ-carbido complexes that includes [WPt(μ-C)Br(CO)2(dppe)(Tp*)], [WPt(μ-C)(NCMe)(CO)2(PPh3)2(Tp*)]OTf, [WPt(μ-C)(S2CNEt2)(CO)2(PPh3)(Tp*)], [WPt(μ-C)(bipy)(CO)2(PPh3)(Tp*)]PF6, [WPt(μ-C)(phen)(CO)2(PPh3)(Tp*)]PF6, [WPt(μ-C)(terpy)(CO)2(Tp*)]PF6, [WPt(μ-C)(CO)2(PPh3)(Bp*)(Tp*)], [WPt(μ-C)(CO)2(PPh3)(Tp*)2] and [WPt(μ-C)(bipy)(CO)2(PPh3)(Bm)(Tp*)], most of which have been structurally charcaterised.

The μ-carbido complexes [Rh2(μ-C)Cl2(PPh3)4] and [Rh2(μ-C)Cl2(dppm)2] cleave CS2 to afford the monothiocarbonyl complexes [RhCl(CS)(PPh3)2] and [Rh2(μ-CS)Cl2(dppm)2]. The latter reacts with dimethyl acetylenedicarboxylate (DMAD) to afford [Rh(μ-CS)(μ-DMAD)Cl2(dppm)2]. This complex is also formed from [Rh(μ-C)(μ-DMAD)Cl2(dppm)2] and sulfur. These strategies also afford the first rhodium selenocarbonyl complexes [Rh(μ-CSe)Cl2(dppm)2] and [Rh(μ-CSe)(μ-DMAD)Cl2(dppm)2].

The reactions of [M(η3-C3H5)Br(CO)2(NCMe)2] (M = Mo, W) or [Mo(η3-C3H5)Br(CO)2(PMe2Ph)2] with Na[H2B(mt)2] (mt = methimazolyl) affords the complexes [M(η3-C3H5)(CO)2{κ3-H,S,S′-H2B(mt)2}], the 3-centre, 2-electron B–H–M interaction of which was found to be inert with respect to opening under mild conditions, while more forcing conditions (heating with PMe2Ph) resulted in cleavage of the entire allyl and borate ligands to form [Mo(CO)3(PMe2Ph)3]. In contrast, the reaction of [Mo(η3-C3H5)Br(CO)2(NCMe)2] with Na[H2B(pz)2] affords either [Mo(η3-C3H5)(CO)2{κ3-H,N,N′-H2B(pz)2}] or (more likely) [Mo(η3-C3H5)(CO)2(NCMe){κ2-N,N′-H2B(pz)2}] which in turn reacts with phosphines to provide [[Mo(η3-C3H5)(CO)2(PPhR2){κ2-N,N′-H2B(pz)2}] (R = Me, Ph). The reactions discussed indicate the propensity for 3-centre, 2-electron B–H–Mo interactions increases in the order H2B(pz)2 < H2B(pz*)2 < H2B(mt)2 (pz* = 3,5-dimethypyrazolyl).

The reaction [W(CSe)(CO)2(Tp*)]NEt4 (Tp* = hydrotris(dimethylpyrazolyl)borate) with N-methyl-N-nitroso-4-toluenesulfonamide affords the nitrosyl complex [W(CSe)(CO)(NO)(Tp*)] which on treatment with excess [Re(THF)(CO)2(η-C5H5)] affords the cumuenic μ-carbido complex [WRe(μ-C)(CO)3(NO)(Tp*)(η-C5H5)] in addition to the μ-selenido complex [Re2(μ-Se)(CO)4(η-C5H5)2].

The first examples of bi- and polynuclear tellurocarbonyl complexes were obtained from the reactions of [W(≡CTe)(CO)2 (Tp*)]NEt4 (Tp*=hydrotris(dimethylpyrazolyl)borate) with [MCl(PCy3 )]/TlPF6 (M=Cu, Au) or [Au2 Cl2 (μ-dppm)], which afford [WM(μ-CTe)(PCy3 )(CO)2 (Tp*)] (M=Cu, Au) and [WAu2 (μ-CTe)(μ-dppm)(CO)2 (Tp*)]3 (PF6 )3 . In all cases it is specifically the tellurocarbonyl that assumes a bridging, but in each case distinct, role including examples of isotellurocarbonyl, semi-bridging and σ-π coordination and combinations thereof. Tetrametallic complexes bridged by C2 Te and C2 Te2 ligands are also described.

The reaction of the halocarbyne [W(≡CBr)(CO)2 (Tp*)] (Tp*=hydrotris(3,5-dimethylpyrazol-1-yl)borate) with trimethylsilyl-butadiyne, mediated by [Pd(PPh3 )4 ] and CuI, affords the first pentadiynylidyne complex [W(≡CC≡CC≡CSiMe3 )(CO)2 (Tp*)]. Desilylation provides a general route to heterobimetallic pentacarbido complexes, including [(Tp*)(CO)2 W(μ-C5 )(PPh3 )2 Ru(η-C5 H5 )] and [(Ph3 P)2 (CO)HIr{(μ-C5 )W(CO)2 (Tp*)}2 ].

We report the first examples of the carbide ligand in (Cy3P)2Cl2Ru≡C (RuC) developing into a μ3 ligand toward metal centers. Conventionally, sterics exclude this coordination mode, but Fe2(CO)9 and Co2(CO)8 expel bridging CO ligands upon reaction with RuC to form trimetallic (Cy3P)2Cl2Ru═CFe2(CO)8 (RuCFe2) and (Cy3P)2Cl2Ru═CCo2(CO)7 (RuCCo2) complexes. Thus, the proximity offered by metal–metal associations in bimetallic carbonyl complexes allows the formation of trinuclear carbide complexes as verified by NMR, Mossbauer, and X-ray spectroscopic techniques.

An expedient procedure is reported for the preparation of the synthetically valuable Au(I) complex [Au(MeCN)(PtBu2C6H4Ph-2)][BF4] (Echavarren's catalyst) directly from gold powder using [NO][BF4] in acetonitrile. The synthetic method obviates the potential presence of silver or halide impurities that follow from the tedious conventional synthesis, and have otherwise been shown to moderate catalyst performance.

The chemistry of transition metal carbynes, L

Heterobi- and tetrametallic phosphoniocarbyne bridged complexes [WAu(μ-CPMe2Ph)Cl(CO)2(Tp*)]+ (Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate), [W2Cu2(μ-CPMe2Ph)2(μ-Cl)2(CO)4(Tp*)2]2+ and [WPt(μ-CPMe2Ph)(COD)(CO)2(Tp*)]+ (COD = 1,5-cyclo-octadiene) arise from the reactions of the mononuclear terminal phosphoniocarbyne [W([triple bond, length as m-dash]CPMe2Ph)(CO)2(Tp*)]PF6 with [AuCl(THT)] (THT = tetrahydrothiophene), [CuCl(SMe2)] and [Pt(nbe)3] (nbe = norbornene) in the presence of COD. The COD ligand in [WPt(μ-CPMe2Ph)(COD)(CO)2(Tp*)]+ is labile and readily replaced by isonitriles to provide [WPt(μ-CPMe2Ph)(CNR)2(CO)2(Tp*)]+ (R = tBu, C6H2Me3-2,4,6) with retention of the tungstaplatinacyclopropene core, the bonding within which was computationally interrogated.

The Pd0/AuI-mediated coupling between stannylcarbyne [W([triple bond, length as m-dash]CSnnBu3)(CO)2(Tp*)] (1) and meso-5,10,15,20-tetrakis(3' or 4'-bromophenyl)porphyrins gives tetrametallic derivatives where a central porphyrin unit is formally substituted at the four meso positions by tungsten benzylidyne moieties. These new 'metallo-porphyrins' undergo metallation at the porphyrin centres with Zn(OAc)2·2H2O to give a pentametallic W4Zn complex or at the tungsten-carbon triple bonds with [AuCl(SMe2)] to give an octametallic W4Au4 complex. The Zn(ii)-metalloporphyrin derivatives are capable of reversibly coordinating further axial ligands such as 4-dimethylaminopyridine or meta-pyridylcarbynes, which themselves are prepared via a coupling between 1 and the appropriate (di)bromopyridine.

Chlorination of the new μ-carbido [Rh2(μ-C)Cl2(μ-dppf)2] (dppf = 1,1′-bis(diphenylphosphino)ferrocene) affords the dirhodium(ii) complex [Rh2(μ-C)Cl4(μ-dppf)2] the carbido bridge of which can only be adequately described by delocalised bonding.

The tungsten-platinum μ-carbido complex [WPt(μ-C)Br(CO)2(PPh3)2(Tp*)] (Tp* = hydrotris(dimethylpyrazol-1-yl)borate) undergoes facile substitution of both bromide and phosphine ligands to afford a diverse library of μ-carbido complexes that includes [WPt(μ-C)Br(CO)2(dppe)(Tp*)], [WPt(μ-C)(NCMe)(CO)2(PPh3)2(Tp*)]OTf, [WPt(μ-C)(S2CNEt2)(CO)2(PPh3)(Tp*)], [WPt(μ-C)(bipy)(CO)2(PPh3)(Tp*)]PF6, [WPt(μ-C)(phen)(CO)2(PPh3)(Tp*)]PF6, [WPt(μ-C)(terpy)(CO)2(Tp*)]PF6, [WPt(μ-C)(CO)2(PPh3)(Bp*)(Tp*)], [WPt(μ-C)(CO)2(PPh3)(Tp*)2] and [WPt(μ-C)(bipy)(CO)2(PPh3)(Bm)(Tp*)], most of which have been structurally charcaterised.

Carbon dioxide can play a vital role as a sustainable feedstock for chemical synthesis. To be viable, the employed protocol should be as mild as possible. Herein we report a methodology to incorporate CO2 into primary, secondary, aromatic or alkyl amines catalysed by a Rh(I) complex bearing a perimidine-based NHC/phosphine pincer ligand. The periminide-based ligand belongs to a class of 6-membered NHC ligand accessed through chelate-assisted double C–H activation. N-Formylation and -methylation of amines were performed using a balloon of CO2, and phenylsilane as the reducing agent. Product selectivity between formylated and methylated products was tuned by changing the solvent, reaction temperature and the quantity of phenylsilane used. Medium to excellent conversions, as well as tolerance to a range of functional groups, were achieved. Stoichiometric reactions with reactants employed in catalysis and time course studies suggested that formylation and methylation reactions of interest begin with hydrosilylation of CO2 followed by reaction with amine substrates.

The sequential reaction of [Ru(C[triple bond, length as m-dash]CC[triple bond, length as m-dash]CH)Cl(CO)2(PPh3)2] with [Ru(CO)2(PPh3)3], and N-chlorosuccinimide affords the binuclear tetracarbido complex [Ru2(μ-C[triple bond, length as m-dash]CC[triple bond, length as m-dash]C)Cl2(CO)4(PPh3)4]. This may be compared with the first example of a butenyndiyl bridged bimetallic complex [Ru2(μ-CH[double bond, length as m-dash]CHC[triple bond, length as m-dash]C)Cl2(CO)4(PPh3)4] which is obtained from the reaction of [Ru(C[triple bond, length as m-dash]CC[triple bond, length as m-dash]CH)Cl(CO)2(PPh3)2] with [RuHCl(CO)(PPh3)3] followed by carbonylation. Characterisational data are discussed with reference to constituent model complexes [Ru(C[triple bond, length as m-dash]CH)Cl(CO)2(PPh3)2] and [Ru(CH[double bond, length as m-dash]CH2)Cl(CO)2(PPh3)2] in addition to DFT analysis of the bonding in the complexes [Ru2(μ-L)Cl2(CO)4(PMe3)4] (L = C[triple bond, length as m-dash]C-C[triple bond, length as m-dash]C, CH[double bond, length as m-dash]CHC[triple bond, length as m-dash]C, CH[double bond, length as m-dash]CH-CH[double bond, length as m-dash]CH). A range of other tetracarbido complexes which may be prepared from [RuCl(C[triple bond, length as m-dash]CC[triple bond, length as m-dash]CH)(CO)2(PPh3)2] is also described and includes [RuAu(μ-C4)Cl(CO)3(PPh3)3], [RuIr(μ-C4)Cl(CO)3(PPh3)4], [RuIr(μ-C4)H(NCMe)(CO)3(PPh3)4]BF4, [RuIr(μ-C4)Cl(η2-O2)(CO)3(PPh3)4], [Ru2Hg(μ-C4)2Cl2(CO)4(PPh3)4], [Ru2Pt(μ-C4)2Cl2(CO)4(PPh3)6] and [Ru2(μ-C4)HCl(CO)4(PPh3)4].

The reactions of [W(CBr)(CO)2(Tp*)] (Tp* = hydrotris(dimethylpyrazolyl)borate) with a range of terminal alkynes (RCCH), mediated by [Pd(PPh3)4] and CuI, afford new proparylidynes [W(C–CCR)(CO)2(Tp*)] [R = tBu, C6H4X (X = H, NH2, NO2), ferrocenyl, APh3 (A = C, Si, Ge), B(O2CCH2)2NMe]. Similar treatment of [W(CBr)(CO)2(Tp*)] with Ph2Si(CCH)2 affords the ditungstaoctatetrayne [W2(μ-C6)(CO)4(Tp*)2] while the bimetallic complex [W2{μ-(CCC)2SiPh2}(CO)4(Tp*)2], which is obtained from [W(CBr)(CO)2(Tp*)] and Ph2Si(CCSnPh3)2, reacts with [AuCl(THT)] (THT = tetrahydrothiophene) to provide the tetrametallic complex [W2Au2{μ-(CCC)2SiPh2}Cl2(CO)4(Tp*)2].

The new A-frame μ2-carbido complexes [Rh2(μ2-C)X2(μ2-dppm)2] (X = Cl, Br; dppm = Ph2PCH2PPh2) react with PhICl2 or [pyH][Br3] to provide rare examples of μ2-halocarbyne complexes [Rh2(μ-CX)(μ-X)X4(μ-dppm)2] (X = Cl, Br).

The reactions of [W(CBr)(CO)2(Tp*)] (Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate) with lithium alkynylselenolates LiSeCCR (R = SiMe3, SiiPr3, nBu, tBu, Ph, p-tolyl) afford the alkynylselenolatoalkylidyne complexes [W(CSeCCR)(CO)2(Tp*)]. Desilylation of the SiMe3 complex furnishes the parent [W(CSeCCH)(CO)2(Tp*)], which may be further derivatised by deprotonation and treatment with triphenylcarbenium or triphenylmetal chlorides to give mixed-heteroatom products [W(CSeCCEPh3)(CO)2(Tp*)] (E = C, Si, Ge, Sn, Pb). This procedure extends to dichlorosilanes, whereby the unusual bimetallic complexes [(Tp*)(CO)2WCSeCCSiRR′CCSeCW(CO)2(Tp*)] (R, R′ = Ph, CH3) are obtained, bridged by unsaturated units interrupted by two different main-group heteroatoms. Finally, the trimetallic analogues, [{(Tp*)(CO)2W(CSeCC)}3SiR] (R = Ph, Et), may be prepared in the same manner from appropriate organotrichlorosilanes.

Ruthenaboratranes of the form [Ru(CO)L{κ4-B(mt)3}] (mt = N-methimazolyl) arise via substitution of the PPh3 ligand in [Ru(CO)(PPh3){κ4-B(mt)3}] by L (L = PMe2Ph, PMe3, P(OMe)3, P(OEt)3, P(OPh)3) or reactions of [RuCl(R)(CO)Ln] (R = Ph, CHCHPh; n = 2, L = PCy3; n = 3, L = P(OMe)3, PMe2Ph) with Na[HB(mt)3].

Sequential treatment of [W([triple bond, length as m-dash]CBr)(CO)2(Tp*)] (Tp* = hydrotris(dimethylpyrazolyl)borate) with nBuLi and Cl2PNiPr2 provides the aminochlorophosphinocarbyne [W([triple bond, length as m-dash]CPClNiPr2)(CO)2(Tp*)]. The chloro substituent undergoes subsitution with RLi (R = Me, Et, Ph) to afford [W([triple bond, length as m-dash]CPRNiPr2)(CO)2(Tp*)] and with [W([triple bond, length as m-dash]CLi)(CO)2(Tp*)] to give the aminobis(alkylidynyl)phosphine [iPr2NP{C[triple bond, length as m-dash]W(CO)2(Tp*)}2]. Treatment with Li[BHEt3] gives the primary aminophosphine [W([triple bond, length as m-dash]CPHNiPr2)(CO)2(Tp*)], formed in a mixture with the ethyl derivative [W([triple bond, length as m-dash]CPEtNiPr2)(CO)2(Tp*)]. Although they could not be isolated, spectroscopic data indicated that halide abstraction with Al2Cl6 forms the phosphaisonitrile salt [W(CPNiPr2)(CO)2(Tp*)][AlCl4], which displays electrophilic character at phosphorus, e.g., in the reaction with diphenylacetylene to furnish the phosphirenium salt [W{CP(C2Ph2)NiPr2}(CO)2(Tp*)][AlCl4]. Finally, the reaction with LiNPh2 gives the mixed diaminophosphinocarbyne, [W{[triple bond, length as m-dash]CP(NiPr2)(NPh2)}(CO)2(Tp*)].

The salt elimination reactions of [NEt4][Mo(CSe)(CO)2(Tp*)] ([NEt4][2], Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate) with a range of metal halide complexes (ClMLn) have been investigated as a possible route to isoselenocarbonyl complexes [Mo(CSeMLn)(CO)2(Tp*)]. Thus the reactions of [NEt4][2] with [RuCl(L)2(η-C5R5)] provide molybdenum-ruthenium derivatives [Mo{CSeRu(L)2(η-C5R5)}(CO)2(Tp*)] (L = PPh3, R = H 4, L = CO, R = Me 5), both of which were structurally characterised. The molybdenum-iron derivative [Mo{CSeFe(CO)2(η-C5H5)}(CO)2(Tp*)] (6) was obtained from [NEt4][2] and [FeCl(CO)2(η-C5H5)] however its formulation currently rests on spectroscopic and microanalytical data. The reaction of [NEt4][2] with [RuH(NCMe)(CO)2(PPh3)2]PF6 affords the structurally characterised hydrido-isoselenocarbonyl complex [Mo{CSeRuH(CO)2(PPh3)2}(CO)2(Tp*)] (7) with no indication of coupling of the hydride and selenocarbonyl ligand.

The reactions of [RuCl(R)(CO)(PPh3)2] (R = CH[double bond, length as m-dash]CHPh, Ph) with Na[H2B(mt)2] (mt = N-methyl-2-mercaptoimidazolyl) transiently provide [Ru(R)(CO)(PPh3){κ3-H,S,S'-H2B(mt)2}] which each evolve to the ruthenaboratrane [Ru(CO)(PPh3)2{κ3-B,S,S'-BH(mt)2}](Ru→B)8. The phosphine ligands may be selectively replaced to provide the complexes [Ru(CO)(L)(PPh3){κ3-B,S,S'-BH(mt)2}] (L = CO, PMe2Ph) and [Ru(CO)L2{κ3-B,S,S'-BH(mt)2}] (L = PMe2Ph, P(OMe)3, L2 = Z-Ph2PCH[double bond, length as m-dash]CHPPh2) with, in each case, retention of the ruthenium-boron dative bond.

A new synthetic approach to hetero-aryl substituted carbyne complexes has allowed the synthesis of pyridyl functionalised carbynes and bis(carbynes), alkylation of which affords the first N-heterocyclic vinylidene complexes.

The Pd0 /AuI mediated [C1 +C2 ] cross-coupling reactions of [W(≡CBr)(CO)2 (Tp*)] (Tp*=hydrotris(dimethylpyrazolyl)borate) and trimethylsilylethynyl-substituted arenes afford new polycyclic aromatic hydrocarbon propargylidynes [W(≡CC≡CR)(CO)2 (Tp*)] (R=9-anthracenyl, 1-pyrenyl). The strategy extends to the first bis(propargylidyne) and bis(pentadiynylidyne) complexes bridged by phenyl or anthracenyl spacers, and to a tetrakis(propargylidyne) connected through a pyrene core.

This work was supported by the National University of Singapore, the Singapore Ministry of Education (WBS R-143-000-586- 112), and the Australian Research Council (DP110101611).

The sterically accessible carbide complex, (Cy3P)Cl3Ru[triple bond, length as m-dash]C-PtCl(py)2, acts as a synthon for terminal and bridging carbide fragments that relocate to pincer and A-frame scaffolds upon ligand addition. This concept, benefitting from coordination sphere selection as the concluding step, confronts traditional synthetic strategies and broadens the scope for carbide complexes.

The first two complete series of pnictogen functionalised carbyne complexes, [M([triple bond, length as m-dash]CAPh2)(CO)2(Tp*)] (M = Mo, W; A = N, P, As, Sb, Bi; Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate), have been prepared. The heavier analogues (A ≠ N) result from successive treatment of [M([triple bond, length as m-dash]CBr)(CO)2(Tp*)] with nBuLi and ClAPPh2 (A = P, Sb, Bi) or BrAsPh2 and include the first examples of arsino, stibino or bismuthino carbyne complexes.

The reactions of the trimethylsilylpropargylidyne [W([triple bond, length as m-dash]CC[triple bond, length as m-dash]CSiMe3)(CO)2(Tp*)] (1: Tp* = hydrotris(dimethylpyrazolyl)borate) towards selenium centred reagents when treated with tetrabutylammonium fluoride (TBAF) were explored in order to prepare alkynylselenolato propargylidynes, e.g., [W([triple bond, length as m-dash]CC[triple bond, length as m-dash]CSePh)(CO)2(Tp*)]. Treating 1 with TBAF and PhSeSePh resulted in E and Z isomers of the vinylcarbyne (allylidyne) complex [W{[triple bond, length as m-dash]CC(SePh)[double bond, length as m-dash]CHSePh}(CO)2(Tp*)] in addition to traces of the trisubstituted derivative [W{[triple bond, length as m-dash]CC(SePh)[double bond, length as m-dash]C(SePh)2}(CO)2(Tp*)]. Reactions with PhSeCl resulted in the isolation of bimetallic bis-substituted allylidyne complex [(Tp*)(CO)2W[triple bond, length as m-dash]CC(SePh)[double bond, length as m-dash]C(SePh)C[triple bond, length as m-dash]CC[triple bond, length as m-dash]W(CO)2(CO)2(Tp*)] as well as the desired selenolatopropargylidyne [W([triple bond, length as m-dash]CC[triple bond, length as m-dash]CSePh)(CO)2(Tp*)].