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 2 (CO) 10 with C 2 H 2 and Me 3 NO yielded the dirhenium complex Re 2 (CO) 9 (NMe 3 ) ( 6 ) and the new zwitterionic complex Re 2 (CO) 9 [η 1 - E -2-CH═CH(NMe 3 )] ( 7 ). Compound 6 was characterized structurally and was found to have a NMe 3 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 (C 2 H 2 ) formally by the insertion of ethyne into the Re-N bond to the NMe 3 ligand. Compound 7 contains a 2-trimethylammonioethenyl ligand, - CH═CH( + NMe 3 ), 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 3 ) carbon atom is formally transferred to the rhenium atom. The reaction of Re 2 (CO) 10 with C 2 H 2 and NEt 3 in the presence of Me 3 NO yielded the new dirhenium complex Re 2 (CO) 9 [η 1 - E -2-CH═CH(NEt 3 )] ( 8 ) together with some 6 and 7 . Compound 8 is structurally similar to 7 , but it contains a NEt 3 group in the ammonioethenyl ligand in the place of the NMe 3 group in 7 . Reactions of 7 with PMePh 2 and PPh 3 yielded the zwitterionic 2-arylphosphonioethenyl-coordinated dirhenium carbonyl complexes, Re 2 (CO) 9 [η 1 - E -2-CH═CH(PPh 2 Me)] ( 9a ) and Re 2 (CO) 9 [η 1 - E -2-CH═CH(PPh 3 )] ( 9b ), and the zwitterionic 1-phosphonioethenyl ligand in the dirhenium carbonyl complexes, Re 2 (CO) 9 [η 1 -1-C(PPh 2 Me)(═CH 2 )] ( 10a ), Re 2 (CO) 8 [μ-η 2 -1-C(PPh 2 Me)(═CH 2 )] ( 11a ), and Re 2 (CO) 8 [[μ-η 2 -1-C(PPh 3 )(CH 2 )] ( 11b ). Compound 10a was converted to 11a and the new compound Re 2 (CO) 7 (μ-H)[μ-η 2 -1-(CH 2 C)P(Ph)(Me)( o -C 6 H 4 )], ( 12 ) by decarbonylation using Me 3 NO. 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.