Kinetics, mechanism, and computational studies of sulfur and oxygen atom transfer reactions catalyzed by rhenium(V) dithiolate complexes

Abstract

<p>A notable feature of rhenium(V) dithiolate complexes is their five coordinated square pyramidal geometry, which allows a vacant coordination site trans to the oxo or thio group for the substrate to access to rhenium(V) center. The oxothenium(V) dimer MeReVO(edt)2 catalyzes sulfur atom transfer (SAT) from Thiirane to Ph3E ( E=P, As). The rate law of triphenylarsine reaction, v = k[Thiirane][Re][Ph3As] 0. The value of k/L mol-1 s-1 at 25.0°C in CDCl3 are 5.58 +/- 0.08 for cyclohexene sulfide. No uncatalyzed reaction has been observed even though the reaction is thermodynamically favored; values of DeltaHo are -21 and -7 kcal mol -1 for PPh3 and AsPh3, respectively, from theoretical calculations. Catalytic amount of oxothenium(V) dimer MeReVO(edt) 2 is enough to proceed the reaction to completion. Mechanism of catalytic cycle has been proposed to interpret the kinetic results. Kinetics and theoretical study have been done on Me(mtp)ReS(PPh3) catalysis ( mtpH 2 = 2-(mercaptomethyl)thiophenol). Interestingly, It is adopt two mechanistic pathways. First, chain mechanism pathways. Second, nucleophilic mechanism pathway. The balance between these two pathways is controlled by phosphine and pyridine N-oxide concentrations;The electronic structure of Re=E ( E=0, S) in Re(V) and Re(VII) have examined theoretically. The Re=E bonds consist of one sigma and two partial pi bond, which agree with bond order analysis 2. Bond strength of ReV=O and ReV=S are from DFT calculation estimated to be approximately 163.7+/- 1.8 kcal mol-1 and 123 +/- 3 kcal mol -1, respectively. Also, bond strength of ReVII=O and ReVII=S are also estimated to be 118.7+/- 1.2 kcal mol -1 and 80.5 +/- 3.5 kcal mol-1 respectively. Stronger ReV=E bond than ReVII=E bond agree with Re VIIO2 and ReVIIOS are the key intermediate in OAT and SAT reaction.</p>