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 = 3.0938(2) Å. Compound can be obtained from the reaction of with ethyne (CH) formally by the insertion of ethyne into the Re-N bond to the NMe ligand. Compound contains a 2-trimethylammonioethenyl ligand, CH═CH(NMe), that is formally a zwitterion having a positive charge on the nitrogen atom and a negative charge on the terminal carbon atom. When coordinated to rhenium by the terminal ethenyl carbon atom, the negative charge on the CH═CH(NMe) carbon atom is formally transferred to the rhenium atom. The reaction of Re(CO) with CH and NEt in the presence of MeNO yielded the new dirhenium complex Re(CO)[η--2-CH═CH(NEt)] () together with some and . Compound is structurally similar to , but it contains a NEt group in the ammonioethenyl ligand in the place of the NMe group in . Reactions of with PMePh and PPh yielded the zwitterionic 2-arylphosphonioethenyl-coordinated dirhenium carbonyl complexes, Re(CO)[η--2-CH═CH(PPhMe)] () and Re(CO)[η--2-CH═CH(PPh)] (), and the zwitterionic 1-phosphonioethenyl ligand in the dirhenium carbonyl complexes, Re(CO)[η-1-C(PPhMe)(═CH)] (), Re(CO)[μ-η-1-C(PPhMe)(═CH)] (), and Re(CO)[[μ-η-1-C(PPh)(CH)] (). Compound was converted to and the new compound Re(CO)(μ-H)[μ-η-1-(CHC)P(Ph)(Me)(-CH)], () by decarbonylation using MeNO. Compound contains an -metalated phenyl ring. The new products , , , , , and were characterized structurally by single-crystal X-ray diffraction analyses.