The coordination chemistry of the neutral tris-2-pyridyl silicon ligand [PhSi(6-Me-2-py)3]

Abstract

Difficulties in the preparation of neutral ligands of the type [RSi(2-py)₃] (where 2-py is an unfunctionalised 2-pyridyl ring unit) have thwarted efforts to expand the coordination chemistry of ligands of this type. However, simply switching the pyridyl substituents to 6-methyl-pyridyl groups (6-Me-2-py) in the current paper has allowed smooth, high-yielding access to the [PhSi(6-Me-2-py)₃] ligand (1), and the first exploration of its coordination chemistry with transition metals. The synthesis, single-crystal X-ray structures and solution dynamics of the new complexes [{PhSi(6-Me-2-py)₃}CuCH₃CN][PF₆], [{PhSi(6-Me-2-py)₃}CuCH₃CN][CuCl₂], [{PhSi(6-Me-2-py)₃}FeCl₂], [{PhSi(6-Me-2-py)₃}Mo(CO)₃] and [{PhSi(6-Me-2-py)₃}CoCl₂] are reported. The paramagnetic Fe²⁺ and Co²⁺ complexes show strongly shifted NMR resonances for the coordinated pyridyl units due to large Fermi-contact shifts. However, magnetic anisotropy also leads to considerable pseudo-contact shifts so that both contributions have to be included in the paramagnetic NMR analysis.