Thiopyridazine-Based Palladium and Platinum Boratrane Complexes

Abstract

Palladium and platinum boratrane complexes of the type [M{B(PnMe,tBu)3}(PPh3)] (M = Pd 1, Pt 2b) have been prepared via the reaction of the soft scorpionate ligand potassium tris(4-methyl-6-tert-butyl-3-thiopyridazinyl)borate KTnMe,tBu with bis(triphenylphosphine)metal(II) dichloride. While reaction with the Pd precursor allowed direct isolation of a symmetric boratrane complex, the Pt analogue led to the hydrido compound [Pt{B(PnMe,tBu)3}(PPh3)H]Cl (2a), which after reaction with a base gave 2b. Subsequent oxidation with Br2 and I2, respectively, led to the dihalide compounds of the molecular formula [M{B(PnMe,tBu)3}X2] (3a,b–4a,b). Halide abstraction with Ag(SbF6) further gave interesting cationic compounds of either dimeric [Pd{B(PnMe,tBu)3}X]2(SbF6)2 (5a,b) or monomeric [Pd{B(PnMe,tBu)3}(NCMe)2](SbF6) (6) nature. All compounds were spectroscopically and X-ray crystallographically characterized revealing strong metal to boron interactions. DFT calculations of 1, 2a, and 2b confirm the strong M–B interaction and a high positive charge on the metal centers.