The reactivity of the unsaturated dimeric rhenium complexes [Re₂H₂(CO)₆{(EtO)₂POP(OEt) ₂}] and [Re₂H₂(CO)₆(Ph₂PCH ₂PPh₂)]: X-ray crystal structure of [Re₂H(CO)₆(Ph₂PCH₂PPh ₂){μ-NC(H)Me}]

The complexes [Re₂H₂(CO)₆(L-L)] [L-L = (EtO)₂POP(OEt)₂ (tedip)(1) or Ph₂PCH₂PPh₂ (dppm)(2)] react with P(OMe)₃ giving 1: 1 adducts which exist in solution in two isomeric forms, both containing a terminal H and a (μ-H) ligand. Both (1) and (2) react with RNC (R = Bu^t, Buⁿ, p-MeOC₆H₄, or p-MeC₆H₄SO₂CH₂) to give the complexes [Re₂H(CO)₆(L-L)(μ-HCNR)] (5) containing an NC-bonded formimidoyl ligand. With CH₃CN (1) and (2) react to give a major product formulated as [Re₂H(CO)₆(L-L){μ-NC(H)Me}] [(6), L-L = tedip; (7a), L-L = dppm] and containing an N-bonded ethylideneimino group; for the product with L-L = dppm this formulation has been confirmed by an X-ray diffraction study. The complex crystallises in the monoclinic space group P2₁/n with a = 9.765(3), b = 29.940(8), c = 11.813(4) Å, β = 104.69(2)°, and Z = 4. The structure was solved by a combination of direct methods and Fourier difference techniques, and refined by full-matrix least squares to R = 0.071 for 2 614 unique, observed diffractometer data. The minor product obtained in the reaction of (2) with CH₃CN is suggested on the basis of spectroscopic evidence to be [Re₂H(CO)₆(dppm)(μ-HNCMe)] (7b) containing an NC-bonded acetimidoyl ligand. Both (1) and (2) form an unstable adduct with CO but do not react with HC≡CH, H₂C=CH₂, or MeO₂CC≡CCO₂Me.