Takahito Watanabe

Reductive Coupling of Six Carbon Monoxides by a Ditantalum Hydride Complex

A ditantalum hydride complex undergoes head-to-head C-C coupling of six CO molecules under mild conditions to produce an octaanionic C(6)O(6) unit. During the reaction, eight-electron reduction of six CO molecules takes place. In the product, the C(6)O(6) unit is coordinated to four tantalum metals through six oxygen and two carbon atoms. The geometrical parameters within the Ta(4)C(6)O(6) core indicate significant contribution from a hexatriene-hexaolate form.

Insertion of a Cationic Metallogermylene into E–H Bonds (E = H, B, Si)

A cationic germylene containing tungsten and N-heterocyclic carbene units reacted with H2 in fluorobenzene at 60 °C, resulting in its insertion into the H-H bond. It also activated the Si-H bond of ethyldimethylsilane and the B-H bond of pinacolborane at ambient temperature to give the insertion products. The latter insertion reactions against hydrosilane and hydroborane were found to be reversible.

Cationic Metallogermylene and Dicationic Dimetallodigermenes: Synthesis by Chloride Abstraction from N-Heterocyclic Carbene-Stabilized Chlorometallogermylenes.

Reaction of NHC-stabilized dichlorogermylenes (NHC = N-heterocyclic carbene) with an anionic tungsten complex produced NHC-stabilized chlorometallogermylenes. Subsequent chloride abstraction from the products with NaBAr4 (Ar = 3,5-(CF3)2C6H3) gave a cationic metallogermylene or dicationic dimetallodigermenes.

Hydrido(hydrosilylene)tungsten Complexes: Dynamic Behavior and Reactivity Toward Acetone

Reaction of a labile tungsten nitrile complex, [(Cp*)W(CO)(2)(NCMe)Me] (Cp*=η(5)-C(5)Me(5)), with H(3)SiC(SiMe(3))(3) gave the hydrido(hydrosilylene) complex [(Cp*)(CO)(2)(H)W=Si(H){C(SiMe(3))(3)}] (1a). The hydrido(silylene) complex [(η(5)-C(5)Me(4)Et)(CO)(2)(H)W=SiMes(2)] (2) (Mes=2,4,6-Me-C(6)H(2)) was synthesized by a similar reaction with H(2)SiMes(2). There is a strong interligand interaction between the hydrido and silylene ligands of these complexes; this was confirmed by a neutron diffraction study of [D(2)]1b, that is, the deuterido and η(5)-C(5)Me(4)Et derivative of 1a. The exchange between the W-H and the Si-D groups was observed in the deuterido complex [D]1a. This H/D exchange proceeded slowly at room temperature, but very rapidly under UV irradiation. Variable-temperature NMR spectroscopy measurements show the dynamic behavior of carbonyl ligands in 1a. Complex 1a reacted with acetone at room temperature to give mainly a hydrosilylation product, [(Cp*)(CO)(2)(H)W=Si(OiPr){C(SiMe(3))(3)}] (3a), along with a siloxy complex, [(Cp*)(CO)(2)WO(Si(H)iPr{C(SiMe(3))(3)})] (4a). At low temperature, a different reaction, namely, α-H abstraction, proceeded to give an equilibrium mixture of 1a and a dihydrido(silyl) complex, [(Cp*)(CO)(2)(H)(2)W(Si(H){OC(=CH(2))Me}{C(SiMe(3))(3)})] (5).