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 2 ) of divalent samarium in the bis-tris(pyrazolyl)borate ligand environment has been reported. In addition, CO 2 activation and functionalisation by lanthanide silylamides in the bis-tris(pyrazolyl)borate ligand environment was demonstrated. Reduction of the Sm(III) precursor [Sm(Tp) 2 (OTf)] (Tp = hydrotris(1-pyrazolyl)borate; OTf = triflate) with KC 8 yielded the insoluble Sm(II) multi-metallic coordination polymer [{Sm(Tp) 2 } n ] 1-Sm. Addition of 1,2-dimethoxyethane (DME) to 1-Sm enabled isolation of the monomeric complex [Sm(Tp) 2 (DME)] 1-Sm(DME). Complex 1-Sm(DME) reduced CO 2 to yield the oxalate-bridged dimeric Sm(III) complex [{Sm(Tp) 2 } 2 (μ-η 2 :η 2 -O 2 CCO 2 )] 2-Sm. The reactions of heteroleptic Ln(III) silylamide complexes [Ln(Tp) 2 (N'')] (Ln = Y, Sm; N'' = N(SiMe 3 ) 2 ) with CO 2 yielded monomeric Ln(III) silyloxides [Ln(Tp) 2 (OSiMe 3 )] 3-Ln and trimethylsilyl isocyanate (OCNSiMe 3 ). Complexes 3-Ln are the first crystallographically characterised examples of Ln(III)-OSiMe 3 bonds accessed via CO 2 activation and functionalisation. Full characterisation data are presented for all complexes, including solid-state molecular structure determination by single-crystal X-ray diffraction.