Synthesis, Structure, and Electronic Properties of Monomeric and Dimeric Trispyrazolylborate Platinum(II) Hydride Complexes

Tp‘PtMe(H)2 (2) [Tp‘ = hydridotris(3,5-dimethylpyrazolyl)borate] has been prepared from Tp‘PtMe(CO) (1) via
reaction with water in a basic acetone/water mixture. Protonation of 2 at one of the pyrazole nitrogen atoms
induces methane elimination, and the resulting platinum(II) monohydride solvent intermediate (3) can be trapped
by added ligand. Two chiral cationic platinum(II) monohydride complexes of the type [κ2-((Hpz*)BHpz*2)Pt(H)(L)][BAr‘4] [L = MeCN (4), CH2CH2 (5); pz* = 3,5-dimethylpyrazolyl, BAr‘4 = tetrakis(3,5-trifluoromethylphenyl)borate] have been isolated. If 2 is protonated in the absence of trapping ligand, a deep red hydride-bridged dinuclear complex, [κ2-((Hpz*)BHpz*2)Pt(μ-H)]2[BAr‘4]2 (6), forms. DFT calculations supplement intuitive
expectations regarding 3-center-2-electron bridging orbital descriptions for the electronic structure of this complex.
X-ray structure determinations for the monomeric acetonitrile adduct 4 and the dicationic dimer 6 are reported.