OXIDATIVE ADDITION OF DISULFIDES TO THE COMPLEX W(CO)3(PHEN)(ETCN) - SYNTHESIS, STRUCTURE, AND REACTIVITY OF W(CO)2(PHEN)(SR)2 (R=PH, ME, CH2PH, TBU PHEN = 1,10-PHENANTHROLINE) COORDINATIVELY UNSATURATED COMPLEXES OF TUNGSTEN(II) THAT REVERSIBLY BIND CO AND OTHER LIGANDS

The complex W(CO)3(phen)(EtCN) undergoes oxidative addition with disul fides forming the formally 16-electron complexes W(CO)2(phen)(SR)2(R = Ph, (t)Bu, Me, benzyl). The reactions proceed through intermediates i dentified spectroscopically as the coordinated disulfide complexes. Th e rate of oxidative addition of coordinated disulfides is in the order (t)BuSSBu(t) << MeSSMe < PhCH2SSCH2Ph < PhSSPh. The complexes W(CO)2( phen)(SR)2 undergo ligand addition, ligand substitution, and thiol/thi olate exchange reactions. Variable-temperature equilibrium studies yie lded thermodynamic parameters for binding of CO to W(CO)2(phen)(SR)2: R = Ph, DELTAH = -7.2 +/- 0.5 kcal/mol, DELTAS = -29 +/- 3.5 cal/(mol deg); R = (t)Bu, DELTAH = -9.5 +/- 0.5 kcal/mol, DELTAS = -41 +/- 3.5 cal/(mol deg). Reaction with trimethylphosphine yields an equilibrium mixture of the 18-electron adduct W(CO)2(phen)(PMe3)(SPh)2 as well as the 16-electron monocarbonyl complex W(CO)(phen)(PMe3)(SPh)2. Addition of trimethyl phosphite yields only W(CO)(phen)(P(OMe)3)(SPh)2. Pyridi ne, propionitrile, hydrogen, and THF do not bind to the W(II) complexe s. Reaction of W(CO)2(phen)(S(t)Bu)2 with 1 equiv of thiophenol yields W(CO)2(phen)(S(t)Bu)(SPh), which reacts with additional thiophenol to yield W(CO)2(phen)(SPh)2. Reaction with excess hydrogen sulfide yield s W(CO)2(phen)(SH)2, which reacts further with thiophenol to yield W(C O)2(phen)(SPh)2. Crystal structures are reported for W(CO)2(phen)(SPh) 2 and W(CO)(Phen)(P(OMe)3(SPh)2.