LAUSR

New zwitterionic dirhenium carbonyl complexes containing ammonioethenyl and phosphonioethenyl ligands have been synthesized and studied. The reaction of Re2(CO)10 with C2H2 and Me3NO yielded the dirhenium complex Re2(CO)9(NMe3) (6) and the new zwitterionic complex Re2(CO)9[η1-E-2-CH═CH(NMe3)] (7). Compound 6 was characterized structurally and was found to have a NMe3 ligand in an equatorial coordination site cis to a long Re-Re single bond, Re-Re = 3.0938(2) Å. Compound 7 can be obtained from the reaction of 6 with ethyne (C2H2) formally by the insertion of ethyne into the Re-N bond to the NMe3 ligand. Compound 7 contains a 2-trimethylammonioethenyl ligand, -CH═CH(+NMe3), 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(+NMe3) carbon atom is formally transferred to the rhenium atom. The reaction of Re2(CO)10 with C2H2 and NEt3 in the presence of Me3NO yielded the new dirhenium complex Re2(CO)9[η1-E-2-CH═CH(NEt3)] (8) together with some 6 and 7. Compound 8 is structurally similar to 7, but it contains a NEt3 group in the ammonioethenyl ligand in the place of the NMe3 group in 7. Reactions of 7 with PMePh2 and PPh3 yielded the zwitterionic 2-arylphosphonioethenyl-coordinated dirhenium carbonyl complexes, Re2(CO)9[η1-E-2-CH═CH(PPh2Me)] (9a) and Re2(CO)9[η1-E-2-CH═CH(PPh3)] (9b), and the zwitterionic 1-phosphonioethenyl ligand in the dirhenium carbonyl complexes, Re2(CO)9[η1-1-C(PPh2Me)(═CH2)] (10a), Re2(CO)8[μ-η2-1-C(PPh2Me)(═CH2)] (11a), and Re2(CO)8[[μ-η2-1-C(PPh3)(CH2)] (11b). Compound 10a was converted to 11a and the new compound Re2(CO)7(μ-H)[μ-η2-1-(CH2C)P(Ph)(Me)(o-C6H4)], (12) by decarbonylation using Me3NO. Compound 12 contains an ortho-metalated phenyl ring. The new products 6,7, 8, 9b, 10a, 11a, 11b and 12 were characterized structurally by single-crystal X-ray diffraction analyses.