Activation and functionalisation of carbon dioxide by bis-tris(pyrazolyl)borate-supported divalent samarium and trivalent lanthanide silylamide complexes.

Synthesis and reactivity with carbon dioxide (CO) of divalent samarium in the bis-tris(pyrazolyl)borate ligand environment has been reported. In addition, CO activation and functionalisation by lanthanide silylamides in the bis-tris(pyrazolyl)borate ligand environment was demonstrated. Reduction of the Sm(III) precursor [Sm(Tp)(OTf)] (Tp = hydrotris(1-pyrazolyl)borate; OTf = triflate) with KC yielded the insoluble Sm(II) multi-metallic coordination polymer [{Sm(Tp)}] 1-Sm. Addition of 1,2-dimethoxyethane (DME) to 1-Sm enabled isolation of the monomeric complex [Sm(Tp)(DME)] 1-Sm(DME). Complex 1-Sm(DME) reduced CO to yield the oxalate-bridged dimeric Sm(III) complex [{Sm(Tp)}(μ-η:η-OCCO)] 2-Sm. The reactions of heteroleptic Ln(III) silylamide complexes [Ln(Tp)(N'')] (Ln = Y, Sm; N'' = N(SiMe)) with CO yielded monomeric Ln(III) silyloxides [Ln(Tp)(OSiMe)] 3-Ln and trimethylsilyl isocyanate (OCNSiMe). Complexes 3-Ln are the first crystallographically characterised examples of Ln(III)-OSiMe bonds accessed CO activation and functionalisation. Full characterisation data are presented for all complexes, including solid-state molecular structure determination by single-crystal X-ray diffraction.