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}].

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 ].

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)].

Advances in Transition Metal Seleno- and Tellurocarbonyl Chemistry.

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.

A heterobimetallic cumulenic µ-carbido complex.

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].

Bridging selenocarbonyl ligands: an open and shut case.

Novel bis(isoselenocarbonyl) complexes [W2Pt(µ-CSe)2(CO)4(L2)(Tp*)2] (L2 = cyclooctadiene, norbornadiene) eliminate the diene upon heating to provide [W2Pt(µ-CSe)2(CO)4(Tp*)2], in which the CSe ligands close to bridge W-Pt bonds in a σ-π mode that may be re-opened by addition of new ligands (CNR: R = tBu, C6H2Me3) to re-establish the isoselenocarbonyl coordination in [W2Pt(µ-CSe)2(CO)4(CNR)2(Tp*)2].

Bi- and Polynuclear Transition-Metal Carbon Tellurides.

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.

New binding modes for CSe: coinage metal coordination to a tungsten selenocarbonyl complex.

The new tungsten selenocarbonylate [NEt4][W([triple bond, length as m-dash]CSe)(CO)2(Tp*)] (Tp* = hydrotris(dimethylpyrazolyl)borate) reacts with group 11 reagents to provide σ-π or isoselenocarbonyl complexes of the form [WM(µ-CSe)(CO)2(PR3)n(Tp*)] (M = Cu, Ag, Au; R = Ph, Cy; n = 1,3) depending on the phosphine stoichiometry or steric bulk. With [Cu(NCMe)4]PF6 and 1,4,7-trithiacyclononane ([9]aneS3) however, the tetrametallic species [WCu3(µ-CSe)(CO)2([9]aneS3)3(Tp*)](PF6)2 is obtained in which one Cu coordinates to the W[triple bond, length as m-dash]C triple bond and two coordinate to the Se atom.