Kinetic study on the reaction of cis-dioxo-(N-(5-X-salicylidene)-2-aminobenzenethiolato) molybdenum(VI) with ethyldiphenylphosphine

The reactions of ethyldiphenylphosphine with a number of cis-dioxomolybdenum(VI) Schiff base coordination complexes are described. These molybdenum complexes incorporate tridentate Schiff base ligands obtained from the condensation of 5-X-salicylaldehyde (X = Cl, Br, H, CH₃O) with o-aminobenzenethiol. Oxomolybdenum(IV) Schiff base complexes were observed as products of the reaction of these Mo(VI) complexes with PEtPh₂. The kinetics for these reactions were followed spectrophotometrically and the applicable rate law is ? dMoO₂L]/dt = k₁MoO₂L]PEtPh₂]. The k₁'s were shown to vary systematically as the X-substituent on the ligand was changed. For MoO₂(5-X-SSP), the specific rate constants at 30°C span the range from 19.6 × 10^?4 M^?1 sec^?1 (X = Br) to 8.4 × 10^?4 M^?1 sec^?1 (X = CH₃O). It was also observed that a correlation exists between the cathodic reduction potentials (E_pc) and the k₁'s within the series. The rate of reaction of MoO₂(5-X-SSP) with PEtPh₂ was altered and systematically controlled through ligand design.