Thiopyridazine-Based Palladium and Platinum Boratrane Complexes.

Palladium and platinum boratrane complexes of the type [M{B(Pn)}(PPh)] (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 KTn 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(Pn)}(PPh)H]Cl (2a), which after reaction with a base gave 2b. Subsequent oxidation with Br and I, respectively, led to the dihalide compounds of the molecular formula [M{B(Pn)}X] (3a,b-4a,b). Halide abstraction with Ag(SbF) further gave interesting cationic compounds of either dimeric Pd{B(Pn)}X (5a,b) or monomeric Pd{B(Pn)}(NCMe) (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.