Synthesis, Structure, and Reactivity of a Mononuclear Organozinc Hydride Complex: Facile Insertion of CO2 into a Zn–H Bond and CO2-Promoted Displacement of Siloxide Ligands

Tris(2-pyridylthio)methane, [Tptm]H, has been employed to synthesize the mononuclear alkyl zinc hydride complex, [κ3-Tptm]ZnH, which has been structurally characterized by X-ray diffraction. [κ3-Tptm]ZnH provides access to a variety of other [Tptm]ZnX derivatives. For example, [κ3-Tptm]ZnH reacts with (i) R3SiOH (R = Me, Ph) to give [κ4-Tptm]ZnOSiR3, (ii) Me3SiX (X = Cl, Br, I) to give [κ4-Tptm]ZnX, and (iii) CO2 to give the formate complex, [κ4-Tptm]ZnO2CH. The bis(trimethylsilyl)amide complex [κ3-Tptm]ZnN(SiMe3)2 also reacts with CO2, but the product obtained is the isocyanate complex, [κ4-Tptm]ZnNCO. The formation of [κ4-Tptm]ZnNCO is proposed to involve initial insertion of CO2 into the Zn–N(SiMe3)2 bond, followed by migration of a trimethylsilyl group from nitrogen to oxygen to generate [κ4-Tptm]ZnOSiMe3 and Me3SiNCO, which subsequently undergo CO2-promoted metathesis to give [κ4-Tptm]ZnNCO and (Me3SiO)2CO.