Synthesis, Structure, and Reactivity of a Mononuciear Organozinc Hydride Complex: Facile Insertion of CO_2 into a Zn-H Bond and CO_2-Promoted Displacement of Siloxide Ligands

摘要

Tris(2-pyridylthio)methane, [Tptm]H, has been employed to synthesize the mononuciear alkyl zinc hydride complex, [κ~3 -Tptm]ZnH, which has been structurally characterized by X-ray diffraction. [kκ~3-Tptm]ZnH provides access to a variety of other [Tptm]ZnX derivatives. For example, [κ~3-Tptm]ZnH reacts with (i) R_3SiOH (R = Me, Ph) to give [κ~4-Tptm]ZnOSiR_3, (ii) Me_3SiX (X = Cl, Br, I) to give [κ~4-Tptm]ZnX, and (iii) CO_2 to give the formate complex, [κ~4-Tptm]ZnO_2CH. The bis(trimethylsilvl)-amide complex [κ~3-Tptm]ZnN(SiMe_3)_2 also reacts with CO_2, but the product obtained is the isocyanate complex, [κ~4-Tptm]ZnNCO. The formation of [κ~4-Tptm]ZnNCO is proposed to involve initial insertion of CO_2 into the Zn—N(SiMe_3)_2 bond, followed by migration of a tri-methylsilyl group from nitrogen to oxygen to generate [κ~4-Tptm]ZnOSiMe_3 and Me_3SiNCO, which subsequently undergo CO_2-promoted metathesis to give [κ~4-Tptm]-ZnNCO and (Me_3SiO)_2CO.