Effects of trifluoromethyl substituents in a tris(pyrazolyl)borate ligand: A structural and spectroscopic study of analogous platinum(IV) trimethyl complexes

To gain insight into how fluorination of the popular hydridotris(pyrazolyl)borate (Tp) ligands modifies the properties of organometallic compounds containing metal-bound alkyls, the novel Pt(IV) complex Tp((CF3)2)PtMe(3) (1; TP(CF3)2 = hydridotris(3,5 -bis(trifluoromethyl)pyrazolyl)borate) was synthesized and fully characterized. X-ray crystallographic studies were carried out on 1 and on the nonfluorinated analogue Tp(Me2)PtMe(3) (2; Tp(Me2) = hydridotris(3,5 -dimethylpyrazolyl)borate). The structural and NMR spectral data for the complexes are compared and provide strong evidence for substantially weaker coordination of the fluorinated Tp ligand. The Pt-N bonds are significantly longer and the Pt-CH3 bonds are slightly shorter in the fluorinated complex. These structural features are echoed in the relative magnitudes of the J(Pt-H) and J(Pt-C) coupling constants for the two complexes. The close spatial contact between the protons of the Pt-IV-CH3 group and fluorines of the 3-CF3 group of the cis-pyrazole ring results in a formal (6)J(H-F) = 1.8 HZ. The nature of this coupling with the possible contribution of intramolecular hydrogen bonding is discussed.