Activation and Reactions of Chalcogen Ligands at Early Transition Metal Centers

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( 1 ) We have synthesized a series of S-bridged W-Ru and W-Rh dinuclear complexes from the reactions of the half-sandwich tungsten trisuffido complex (PPh_4)[Cp*WS_3] and various ruthenium and rhodium complexes. And reactivity of the hetero-dimetallic has been examined. For instance, we have found that the dinuclear hydride complex Cp*W(m-S)_3RuH(PPh_3)_2 reacts with 1 equiv of MeOCOC≡CH to give Cp*W(μ-S)_3Ru(C(=CH_2)COOMe)(PPh_3)_2. On the other hand, the reaction between Cp*W(S)(μ-S)_2-Rh(PPh_3)_2 and 1 equiv of MeOCOC≡CH in THFgave rise to Cp*W(μ-S_2C_2HCOOMe)(μ-S)Rh(PPh_3)_2, where the alkyne was added to the terminal S atom and the bridging S atom.( 2 ) We carried out a series of alkylation reactions at a terminal sulfide of (PPh_4)[Cp*WS_3]. For instance, the reaction with allychloride or methallychloride produced Cp* W(S)_2(SCH_2CR=CH_2) (R = H, Me). which was found to show intresting fluxional behavior of the allylthiolate group. In order to elucidate the mechanism of the fluxionality, we have newly synthesized (PPh_4)[(EtMe_4C_5)W(O)(S)-(SCH_2CR=CH2)] and (PPh_4)[(Me_5C_5)W(O)(S) (SeCH_2CR=CH_2)], and have analyzed variable-temperature ^1H NMR spectra of these complexes. The allyl group of (PPh_4)[(EtMe_4C_5)W(O)(S)- (SCH_2CR=CH_2)] was found to migrate between the two S sites, while the 1,3-allyl shift occured at Se in the case of (PPh_4) (Me_5C_5)W(O)(S)(SeCH_2CR=CH_2)].( 3 ) We have successfully synthesized the halfsandwich tungsten complex which carries three different chalcoge atoms, (PPh_4)[Cp*W(O)(S)(Se)]. Furthermore, we were able to separate the diastereomers of (PPh_4)[Cp*W(O)(S)(SR*)] (R* = chiral alkyl group), and the subsequent reaction with Li_2Se_2 gave enatio-excess (PPh_4)[Cp*W(O)(S)(Se)].