Chemistry of [Et4N][MoIV(SPh)(PPh3)(mnt)2] as an analogue of dissimilatory nitrate reductase with its inactivation on substitution of thiolate by chloride.
Structural-functional analogue of the reduced site of dissimilatory nitrate reductase is synthesized as [Et4N][MoIV(SPh)(PPh3)(mnt)2].CH2Cl2 (1). PPh3 in 1 is readily dissociated in solution to generate the active site of the reduced site of dissimilatory nitrate reductase. This readily reacts with nitrate. The nitrate reducing system is characterized by substrate saturation kinetics. Oxotransfer to and from substrate has been coupled to produce a catalytic system, NO3- + PPh3 --> NO2- + OPPh3, where NO3- is the substrate for dissimilatory nitrate reductase. The corresponding chloro complex, [Et4N][MoIV(Cl)(PPh3)(mnt)2].CH2Cl2 (2), responds to similar PPh3 dissociation but is unable to react with nitrate, showing the indispensable role of thiolate coordination for such oxotransfer reaction. This investigation provides the initial demonstration of the ligand specificity in a model system similar to single point mutation involving site directed mutagenesis in this class of molybdoenzymes.
Department of Chemistry, IIT Kanpur, India.
Amit
A
Majumdar
Kuntal
K
Pal
Sabyasachi
S
Sarkar