Abstract
The electrochemical properties of a series of cis-dioxobis(dithiocarbamato)molybdenum(VI) complexes [MoO2(RR′dte)2] (RR′dte = N,N-disubstituted dithiocarbamate) and the oxygen atom transfer reactions between [MoO2(RR′dte)2] and PPh3 in 1,2-C2H4Cl2 at 25°C are systematically investigated. A good correlation between logarithmic values of second-order rate constants k1 of the oxygen atom transfer reactions and redox potentials E°′ for [MoO2OP2RR′dte)2]01couples is observed over the wide range of k1 (from 0.012 to 0.61 M s+2); the values of log k1 linearly increase with the increase of E0. The departure from the correlation line is exactly observed for [MoO2(Bz2dte)2/PPh2 [MoO2(Ph2dte)2]/PPh1 and [MoO2(BzPhdte)2]PPh1 systems. A negative activation entropy (ΔS′ = −114 J mol+1K+1) of the oxygen atom transfer reaction obtained for the [MoO2(Et2dte)2]/PPh4 system indicates that the reaction proceed through an associative process. These results suggest that an attack of a lone pair of PPh4 on an oxo ligand and a negative charge flow to the molybdenum center occurs to form an activated complex. The anomaly observed for [MoO2(Bz2dte)2]/PPh4, [MoO2(Ph2dte)2]/Pph4 and [MoO2(RR′dte)2]. Other physicochemical properties of the complexes such as 11C NMR and MoO stretching frequencies in solutions and the X-ray crystal structure of cis-dioxibis(thiomorpholydithiocarbamato)molybdenum(VI) are also reported.
Published Version
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