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

The tris(indazol-1-yl)borate complexes PdMe 3{(ind) 3BH} (2a′) and PtMe 3{(ind) 3BH} · 0.5CH 2Cl 2 (2b′) are obtained on reaction of PdMe 2(tmeda) (tmeda=N,N,N′,N′-tetramethylethylenediamine) or [PtMe 2(SEt 2)] 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 [MMe 3{(pz) 3CH}] + using [(H 2C=N-NH) 3BH] - as a model for [(ind) 3BH] - and (H 2C=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 ′NN′ 'bite' is larger for palladium than platinum complexes, and the NN′ '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. © 1999 Elsevier Science S.A.