Coinage metal complexes of tris(pyrazolyl)methanide [C(3,5-Me2pz)3]−: κ3-coordination vs. backbone functionalisation

Abstract

Tris(pyrazolyl)methanides, [C(3,5-R₂pz)₃]⁻, contain an unassociated tetrahedral carbanionic centre in the bridgehead position. In addition to nitrogen donor centres for transition metal coordination, an accessible reactive site for further manipulations is available in the backbone of the ligand. The coordination variability of the ambidental C⁻/N ligand [C(3,5-Me₂pz)₃]⁻ was elucidated by investigating its coinage metal complexes. Two principle coordination modes were found for complexes of general formula [LMPR₃] (with M = Cu^I, Ag^I, Au^I; L = [C(3,5-Me₂pz)₃]⁻; R = Ph, OMe). While for Cu(I) (2, 3) and Ag(I) (4) complexes the anionic ligand acts as a face-capping, six electron N₃-donor, gold(I) (5) is coordinated by the bridging carbanion yielding a two coordinate Au(I) complex comprising a covalent Au–C bond. The complexes featuring the κ³-coordinated N₃-donor ligand were investigated by ³¹P CP (MAS) NMR in the solid state.