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*)].

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(-H2C=CH2)(PPh3)2] or [Pt(nbe)3] (nbe = norbornene) to furnish rare examples of μ2-halocarbyne...

Transition Metal Carbide Complexes

Carbide complexes remain a rare class of molecules. Their paucity does not reflect exceptional instability but is rather due to the generally narrow scope of synthetic procedures for constructing carbide complexes. The preparation of carbide complexes typically revolves around generating L_nM-CE_x fragments, followed by cleavage of the C-E bonds of the coordinated carbon-based ligands (the alternative being direct C atom transfer). Prime examples involve deoxygenation of carbonyl ligands and deprotonation of methyl ligands, but several other p-block fragments can be cleaved off to afford carbide ligands. This Review outlines synthetic strategies toward terminal carbide complexes, bridging carbide complexes, as well as carbide-carbonyl cluster complexes. It then surveys the reactivity of carbide complexes, covering stoichiometric reactions where the carbide ligands act as C₁ reagents, engage in cross-coupling reactions, and enact Fischer-Tropsch-like chemistry; in addition, we discuss carbide complexes in the context of catalysis. Finally, we examine spectroscopic features of carbide complexes, which helps to establish the presence of the carbide functionality and address its electronic structure.

Synthesis and Systematic Structural Analysis of Cationic Half-Sandwich Ruthenium Chalcogenocarbonyl Complexes

Although the chemistry of transition-metal complexes with carbonyl (CO) and thiocarbonyl (CS) ligands has been well developed, their heavier analogues, namely selenocarbonyl (CSe) and tellurocarbonyl (CTe) complexes remain scarce. The limited availability of such CSe and CTe complexes has so far hampered our understanding of the differences between such chalcogenocarbonyl (CE: E=O, S, Se, Te) ligands. Herein, we report the synthesis and properties of a series of cationic half-sandwich ruthenium CE complexes of the type [CpRu(CE)(H₂ IMes)(CNCH₂ Ts)][BAr^F ₄ ] (Cp=η⁵ -C₅ H₅ ^- ; H₂ IMes=1,3-dimesitylimidazolin-2-ylidene; Ar^F =3,5-(CF₃ )₂ C₆ H₃ ). A combination of X-ray diffraction analyses, NMR spectroscopic analyses, and DFT calculations revealed an increasing π-accepting ability of the CE ligands in the order O<S<Se<Te. A variable-temperature NMR analysis of the thus obtained chiral-at-metal CE complexes indicated high stereochemical stability.

Metal coordination to bipyridyl carbynes

A new synthetic approach to hetero-aryl substituted carbyne complexes has allowed the synthesis of bipyridyl functionalised carbynes and bis(carbynes) with three potential sites for metal coordination to either the two pyridyl donors or the WC bond.

Heterobimetallic μ2-carbido complexes of platinum and tungsten

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.

A heterobimetallic cumulenic μ-carbido complex

Cleavage of a selenocarbonyl ligand in [W(CSe)(NO)(CO)(Tp*)] by [Re(THF)(CO)₂(Cp)] provides heterobimetallic cumulenic μ-carbido and μ-selenido complexes.

Dimetalla-heterocyclic carbenes: the interconversion of chalcocarbonyl and carbido ligands

Different classes of dirhodium μ-carbido complexes cleave CS₂ to afford mono- and bi-nuclear CS complexes, the CSe analogues of which are also described.

The significance of phosphoniocarbynes in halocarbyne cross-coupling reactions

Competent intermediates as well as productive and non-productive tangents have been identified in the catalytic cycle for palladium(0)–copper(i) mediated synthesis of propargylidynes via cross coupling reactions of bromocarbyne complexes with alkynes.

Auriferous alkynylselenolatoalkylidynes

Gold plating carbynes – The incorporation of gold(i) centres, either terminal or bridging, into alkynylselenolatocarbynes provides models for how such metallated carbon-wires might bind to metal surfaces.

Alkynylselenolatoalkylidynes (LnMC–Se–CCR) as building blocks for mixed metal/main-group extended frameworks

The reactions of [W(CBr)(CO)₂(Tp*)] (Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate) with lithium alkynylselenolates LiSeCCR (R = SiMe₃, SiⁱPr₃, ⁿBu, ^tBu, Ph, p-tolyl) afford the alkynylselenolatoalkylidyne complexes [W(CSeCCR)(CO)₂(Tp*)].

Synthesis of pyridyl carbyne complexes and their conversion to N-heterocyclic vinylidenes

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.

Phosphaisonitrile umpolung – synthesis and reactivity of chloro aminophosphino carbynes

The synthesis of the first P-halo-aminophosphinocarbyne complex is described in addition to exploration of its ligand-based reactivity towards nucleophilic substitution and P-halide abstraction processes as a possible route to cationic aminophosphaisonitrile derivatives.

Isoselenocarbonyl complexes

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 (ClML_n) have been investigated as a possible route to isoselenocarbonyl complexes [Mo(CSeML_n)(CO)₂(Tp*)].

Synthesis and reactivity of an anionic allenylidene complex

The reaction of [W([triple bond, length as m-dash]CC[triple bond, length as m-dash]CSiMe₃)(CO)₂(Tp*)] (Tp* = hydrotris(dimethylpyrazolyl)borate) with MeLi generates the first example of an anionic allenylidene complex Li[W([double bond, length as m-dash]C[double bond, length as m-dash]C[double bond, length as m-dash]CMeSiMe₃)(CO)₂(Tp*)] which reacts with electrophiles (H⁺, Me⁺) at the β-carbon to afford vinylcarbyne (allylidyne) complexes [W([triple bond, length as m-dash]CCE[double bond, length as m-dash]CMeSiMe₃)(CO)₂(Tp*)] (E = H, Me), and with bromine provides the unprecedented binuclear bis(carbyne) complex {C([double bond, length as m-dash]CMeSiMe₃)C[triple bond, length as m-dash]W(CO)₂(Tp*)}₂via oxidative C-C coupling at the β-carbon.

Bis(alkylidynyl)arsines

The synthesis and characterization of the first examples of bimetallic bis(alkylidynyl)arsines are described. For the tungsten complexes, these may be prepared by a potentially generalizable route: successive treatment of [W(CBr)(CO)₂(Tp*)] with ⁿBuLi, ACl₃ (A = P, As) and a nucleophilic source of R⁻via the inferred intermediacy of [ClA{CW(CO)₂(Tp*)}₂].