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

The tris(indazol-1-yl)borate complexes PdMe3{(ind)(3)BH} (2a') and PtMe3{(i nd)(3)BH} . 0.5CH(2)Cl(2) (2b') are obtained on reaction of PdMe2(tmeda) (t meda = N,N,N',N'-tetramethylethylenediamine) or [PtMe2(SEt2)](2) with Tl[(i nd)(3)BH], respectively, followed by addition of iodomethane. X-ray structu ral studies of these complexes, together with theoretical calculation at th e SCF level of geometries for these complexes and [MMe3{(pz)(3)CH}](+) usin g [(H2C=N-NH)(3)BH](-) as a model for [(ind)(3)BH](-) and (H2C=N-NH)(3)CH a s a model for tris(pyrazol-1-yl)methane, respectively, are reported. The th eoretical studies model the trends in coordination geometry determined crys tallographically on going from]Pd to Pt and from [(ind)(3)BH](-) to (pz)(3) CH as ligands, in particular M-N is longer and the 'N ... N' 'bite' is larg er for palladium than platinum complexes, and the N ... N' 'bite' is larger for the berate complexes. Calculations at the SCF level indicate that [(pz )(3)BH](-) has a larger intrinsic 'bite' than isoelectronic (pz)(3)CH. (C) 1999 Elsevier Science S.A. All rights reserved.