MONONUCLEAR AND DINUCLEAR CARBONYL-COMPLEXES OF 1,4,7-TRIMETHYL-1,4,7-TRIAZACYCLONONANE)RHODIUM(I) - FACILE MIGRATION OF A C(O)OME LIGAND AT A DINUCLEAR RH(MU-CO)(2)RH CORE

The reaction of 1,4,7-trimethyl-1,4,7-triazacyclononane (Cn) with [{( CO)(2)Rh(mu-Cl)}(2)] in methanol at 0 degrees C, followed by the addit ion of NH4PF6, results in the formation of the mononuclear carbonyl co mplex [CnRh(mu-CO)(2)]PF6 ([1]PF6), the dinuclear carbonyl complex [C nRh(mu-CO)(3)RhCn*] (PF6)(2) I[2](PF6)(2)) and the dinuclear methoxyc arbonyl complex [Cn Rh(C(O)OMe) (mu-CO)(2)RhCn*]PF6 ([3]PF6). The rea ction of[2](PF6)(2) with NaOMe results in formation of [3]PF6 by the a ttack of the methoxide at a bridging carbonyl. Treatment of [3]PF6 wit h NH4PF6 regenerates [2](PF6)(2), thus showing that the methoxylation of [2](PF6)(2) is reversible. The structures of [1]PF6, [2](PF6)(2) an d [3]PF6 have been determined by single-crystal X-ray diffraction. For [3]PF6 an unprecendented facile, reversible, migration of the C(O)OMe ligand between the two rhodium centres of the Rh(mu-CO)(2)Rh core is observed.