Synthesis, Structures, and Transformations of Bridging and Terminally-Coordinated Trimethylammonioalkenyl Ligands in Zwitterionic Pentaruthenium Carbido Carbonyl Complexes.

Reactions of the pentaruthenium cluster complexes Ru(μ-C)(CO) (), Ru(μ-C)(CO)[μ-η-O═C(NMe)](μ-H) (), and Ru(μ-C)(CO)Cl(μ-H) () with ethyne (CH) in the presence of MeNO yielded the zwitterionic complexes Ru(μ-C)(CO)[μ-η-CHCH(NMe)] (), Ru(μ-C)(CO)[μ-η-O═C(NMe)](η--CH═CH(NMe)(μ-H) (), and Ru(μ-C)(CO)Cl[η--CH═CH(NMe)](μ-H) (). Each product contains a positively charged trimethylammonioethenyl ligand, CH═CH(NMe), that is derived from a 2-trimethylammonioethenide, CH═CH(NMe), zwitterion that formally has a positive charge on the nitrogen atom and a negative charge on the terminal enyl carbon atom. The trimethylammonioethenyl ligand, CH═CH(NMe) in is a η-ligand that bridges a Ru-Ru bond on a basal edge of the square-pyramidal Ru cluster by a combination of σ + π cooordination of the ethenyl group.