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).

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*)].

Construction of an iminoketenylidene.

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

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 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 significance of phosphoniocarbynes in halocarbyne cross-coupling reactions.

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.

Tricarbonyl rhenium(i) tetrazolato and N-heterocyclic carbene complexes: versatile visible-light-mediated photoredox catalysts.

We have investigated the capacity of a range of structurally-diverse, photoactive rhenium(i) tricarbonyl complexes featuring either tetrazolato or N-heterocyclic carbene (NHC) ligands to facilitate fundamental classes of visible-light-mediated photoredox-catalysed reactions. In this study, we demonstrate that these systems mediate representative atom-transfer radical addition, hydrodehalogenation, and α-amino C-H functionalisation reactions. These rhenium(i) complexes provide greater or at least comparable reactivity to the prototypical photoredox catalyst [Ru(bpy)3]2+ in many cases.

Simple generation of a dirhodium µ-carbido complex via thiocarbonyl reduction.

The reaction of [RhCl(CS)(PPh3)2] with excess catecholborane affords the cumulenic carbido complex [Rh2(µ-C)Cl2(PPh3)4] which undergoes phosphine and halide substitution to afford a range of complexes in which the Rh[double bond, length as m-dash]C[double bond, length as m-dash]Rh spine remains intact. Amongst these, the reactions with K[L] (L = H2B(pz)2, H2B(pzMe2)2, HB(pz)3; pz = pyrazol-1-yl) afford [Rh2(µ-C)(PPh3)2(L)2] whilst with K[HB(pzMe2)3] the unsymmetrical complex [Rh2H(µ-C)(µ-C6H4PPh2-2){HB(pzMe2)3}2] is obtained in which the carbido ligand spans d6-Rh(iii) and d8-Rh(i) centres.