Observations on the steric impact of N- and S- donor scorpionate ligands

A comparison is made between the steric influences of a range of zinc hydrotris(pyrazolyl)borates and zinc hydrotris(thio-imidazolyl)borates ([Zn(TpR)Cl], [Zn(TmR)Cl],: R = Me, iPr, Ph tBu)) using inverse cone angle analysis. The study combines the crystallographic analysis of [Zn(TmiPr)Cl] and [Zn(TmPh)Cl] with the data previously deposited with the Cambridge Crystallographic Data Centre. The study suggests that despite efforts to manipulate the reactive pocket around the metal centre in M(TmR) complexes, the incorporation of sterically confining substituents onto the framework has a minimal effect at the metal centre unless the group attached is very large.