Chemistry of Highly Electrophilic Binuclear Cations. 3. Reactivity of [W2(η5-C5H5)2(μ-CO)(CO)2(μ-Ph2PCH2PPh2)][B{3,5-C6H3(CF3)2}4]2toward Small Donor Molecules

Abstract

Reaction of the unsaturated tricarbonyl complex [W2Cp2(μ-CO)(CO)2(μ-dppm)](BAr‘4)2 with HSPh leads to the thiolate-bridged complex [W2Cp2(μ-SPh)(μ-CO)(CO)2(μ-dppm)](BAr‘4), which is obtained as a mixture of two isomers. This reaction proceeds faster in the presence of a base (1,8-diazabicyclo[5.4.0]undec-7-ene, DBU), as expected. The title compound also reacts at room temperature with stoichiometric amounts of phosphines HPR1R2 (R1 = R2 = Ph; R1 = H, R2 = Cy) to give the corresponding phosphide hydride derivatives [W2Cp2(μ-H)(μ-PR1R2)(CO)2(μ-dppm)](BAr‘4)2, which display a trans relative geometry of their phosphide and diphosphine ligands. Deprotonation of these hydride complexes with DBU gives the cis phosphide compounds [W2Cp2(μ-PR1R2)(CO)2(μ-dppm)](BAr‘4), through an unexpected reduction and dehydrogenation/isomerization pathway. This overall deprotonation process is not reversible, and treatment of the latter compound with HBF4·OEt2 gives the hydride isomer cis-[W2Cp2(μ-H)(μ-PR1R2)(CO)2(μ-dppm)](BAr‘4)(BF4), which displays a strong hydrogen bond interaction between the bridging hydride ligand and the external BF4- anion. Treatment of the title compound with N2CHSiMe3 or HC⋮C(p-tol) leads to dicarbonyls [W2Cp2{μ-κ1-N2CH(SiMe3)}(CO)2(μ-dppm)](BAr‘4)2 or [W2Cp2{μ-η2:η2-HCC(p-tol)}(CO)2(μ-dppm)](BAr‘4)2 (two isomers), displaying four-electron-donor diazoalkane or alkyne bridging ligands.