ADDITION OF CARBANIONS TO RIS(TRIMETHYLPHOSPHINE)(CYCLOOCTADIENE)-IRIDIUM(I) CHLORIDE - 3 DIFFERENT MODES OF REACTION DEPENDING ON THE NATURE OF THE CARBANION

Reaction between carbanions and the cationic cyclooctadiene iridium co mplex, [Ir(COD)(PMe3)3]Cl, gives rise to one of three different produc ts depending on the nature of the carbanion. For resonance stabilized carbanions (indenyl, allyl, benzyl), the products are (2-substituted c yclooct-5-en-1-yl)tris(trimethylphosphine)iridium complexes derived fr om nucleophilic attack of the carbanion on one of the double bonds of the coordinated cyclooctadiene. One such complex, cyclooct-5-en-1-yl)t ris(trimethylphosphine)iridium was characterized by single crystal X-r ay diffraction and crystallizes in the orthorhombic space group P2(1)2 (1)2(1) with a = 9.179(2), b = 15.210(3), c = 19.474(4) angstrom, V = 2718.8 angstrom 3 and Z = 4. For non-stabilized anions such as methyl, ethyl and vinyl, the products are bis(trimethylphosphine)(cyclooctadi ene)iridium alkyl (or vinyl) complexes derived from the displacement o f PMe3 from iridium by the carbanion. For non-stabilized secondary or tertiary carbanions, the product is an unsubstituted (cyclooct-5-en-1- yl)tris(methylphosphine)iridium complex derived from the addition of h ydride to coordinated cyclooctadiene. Some information and discussion concerning the mechanisms of these reactions are provided.