Synthesis and Structural Characterization of Bis(2-pyridylthio)methyl Cadmium Compounds: Access to a Six-Coordinate Cadmium Dialkyl Complex.

Cd[N(SiMe3)2]2 and Me2Cd react with bis(2-pyridylthio)methane ([Bptm]H) to afford [Bptm]CdN(SiMe3)2 and [Bptm]CdMe, in which the L2X [Bptm] ligand coordinates in a k3-mode with a direct Cd-C bond that is distinct from {k2-[Bptm]H}CdX2 complexes, in which the ligand is bidentate and serves as an L2 donor. The Cd-N(SiMe3)2 bond of [Bptm]CdN(SiMe3)2 is reactive, and [Bptm]CdN(SiMe3)2 undergoes metathesis with R3SiOH (R = Me, Ph) to form dimeric cadmium siloxides, {[Bptm]Cd(μ-OSiMe3)}2 and {[Bptm]Cd(μ-OSiPh3)}2. In addition to the formation of {[Bptm]Cd(μ-OSiMe3)}2 via this approach, {[Bptm]Cd(μ-OSiMe3)}2 is also obtained by the reaction of [Bptm]CdN(SiMe3)2 with CO2, presumably via a sequence in which CO2 inserts into the Cd-N(SiMe3)2 bond followed by elimination of Me3SiNCO. The dimeric nature of {[Bptm]Cd(μ-OSiMe3)}2 and {[Bptm]Cd(μ-OSiPh3)}2 contrasts with the monomeric nature of the zinc counterpart, [Bptm]ZnOSiPh3, an observation that is in accord with DFT calculations on {[Bptm]M(μ-OSiPh3)}2 and [Bptm]MOSiPh3 (M = Zn, Cd). In addition to [Bptm]CdX compounds, [Bptm]2Cd, a rare example of a six-coordinate dialkyl cadmium compound, which also features two [Bptm] ligands, has been obtained.