REACTIONS OF COMPLEX LIGANDS .51. SYNTHESIS AND REACTIONS OF STABLE (CARBENE)TETRACARBONYL CHELATE COMPLEXES OF MOLYBDENUM

The stable (carbene-C,O, -C,N, and -C,S)tetracarbonyl chelate complexes of molybdenum 2b-2c have,been obtained by mild decarbonylation of their corresponding pentacarbonyl precursors 1b - 1c. The chelate complexes have been characterized by elemental analyses and spectroscopic data. In addition, the structure of C,N chelate 2c has been confirmed by X-ray analysis. In contrast to its C,N and C,S analogues, the C,O chelate complex 2a undergoes ring opening at temperatures as low as -40-degrees-C upon addition of triphenylphosphane. At 20-degrees-C the phosphane-substituted chelate complex 4a is obtained. C,N and C,S chelate complexes require higher temperatures for the reaction to give similar fac-tricarbonyl complexes 4b - 4c.