Synthesis and Chemistry of Ammonioethenyl and Phosphonioethenyl Ligands in Zwitterionic Dirhenium Carbonyl Complexes.

New zwitterionic dirhenium carbonyl complexes containing ammonioethenyl and phosphonioethenyl ligands have been synthesized and studied. The reaction of Re(CO) with CH and MeNO yielded the dirhenium complex Re(CO)(NMe) () and the new zwitterionic complex Re(CO)[η--2-CH═CH(NMe)] (). Compound was characterized structurally and was found to have a NMe ligand in an equatorial coordination site to a long Re-Re single bond, Re-Re = 3.

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.

Activation of Heteroaromatic C-H Bonds in Furan and 2,5-Dimethylfuran.

The reaction of Re(CO)(μ-CH)(μ-H) (1) with furan in CHCl at 40 °C yielded two new isomeric dirhenium compounds, Re(CO)(μ-η-2,3-CHO)(μ-H) (2) and Re(CO)(μ-η-3,2-CHO)(μ-H) (3), which contain a bridging (σ + π)-coordinated furyl ligand formed by activation of the C-H bond at the 2 and 3 positions of furan, respectively. Compound 3 is the first example of a compound formed by C-H bond activation at the 3 position of a furan ring. Compound 3 was isomerized to 2 by heating to 80 °C for 7 days.