The reactivity of the unsaturated dimeric rhenium complexes [Re2H2(CO)6{(EtO)2POP(OEt)2}] and [Re2H2(CO)6(Ph2PCH2PPh2)]: X-ray crystal structure of [Re2H(CO)6(Ph2PCH2PPh2){µ-NC(H)Me}]

Abstract

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 HCCH, H₂CCH₂, or MeO₂CCCCO₂Me.