Coordination geometries for palladium and platinum: theoretical studies and the synthesis and structure of tris(indazol-1-yl)borate complexes MMe3{(ind)3BH}

Abstract

The tris(indazol-1-yl)borate complexes PdMe3{(ind)3BH} (2a) and PtMe3{(ind)3BH}.0.5CH2Cl2 (2b) are obtained on reaction of PdMe2(tmeda) (tmeda = N,N,N',N'-tetramethylethylenediamine) or [PtMe2(SEt2)]2 with Tl[(ind)3BH], respectively, followed by addition of iodomethane. X-ray structural studies of these complexes, together with theoretical calculation at the SCF level of geometries for these complexes and [MMe3{(pz)3CH}]+ using [(H2C=N–NH)3BH]-as a model for [(ind)3BH]- and (H2C=N–NH)3CH as a model for tris(pyrazol-1-yl)methane, respectively, are reported. The theoretical studies model the trends in coordination geometry determined crystallographically on going from Pd to Pt and from [(ind)3BH]- to (pz)3CH as ligands, in particular M–N is longer and the 'N···N' ‘bite’ is larger for palladium than platinum complexes, and the 'N···N' ‘bite’ is larger for the borate complexes. Calculations at the SCF level indicate that [(pz)3BH]- has a larger intrinsic ‘bite’ than isoelectronic (pz)3CH.