SPECTROSCOPIC EVIDENCE FOR HEMILABILE BEHAVIOR IN A BETA-KETOPHOSPHONATE COMPLEX OF MOLYBDENUM(VI)

The beta-ketophosphonate complexes hyl(2-phenyl-2-oxoethyl)phosphonate )molybdenum(VI) (5a) and dichlorodioxo(triethylphosphonoacetate)molybd enum (VI) (5b) have been synthesized in 61-80% yield and characterized by NMR and IR spectroscopies. The crystal structure of(5a) (orthorhom bic, 2(1)2(1)2(1), a= 8.0909 (5) Angstrom, b = 14.1432 (5) Angstrom, c = 14.9749 (8) Angstrom, Z = 4) shows that the beta-ketophosphonate li gand is coordinated to the molybdenum atom in a bidentate binding mode . In solution, compound (5a) displays hemilabile behavior as revealed by an IR spectrum recorded in CH3CN. Reaction of (5a) with diphenylsul foxide (DPSO) in CH2Cl2 results in complete displacement of the beta-k etophosphonate Ligand and formation of dichlorodioxobis(diphenylsulfox ide)-molybdenum(VI) (8) in 96% yield.