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.