Synthesis, molecular structures, and chemistry of some new palladium(ii) and platinum(ii) complexes with pentafluorophenylligands

Abstract

A series of palladium(II) and platinum(II) complexes possessing pentafluorophenyl ligands of the general formula [M(L–L)(C₆F₅)Cl] (M = Pd 3; L–L = tmeda (N,N,N′,N′,-tetramethylethylenediamine) a; 1,2-bis(2,6-dimethylphenylimino)ethane) b; dmpe (1,2-bis(dimethylphosphino)ethane) c; dcpe (1,2-bis(dicyclohexylphosphino)ethane) d; Pt 4; L–L = tmeda a; 1,2-bis[3,5-bis(trifluoromethyl)phenylimino]-1,2-dimethylethane b; dmpe c; dcpe d) were readily synthesized from the dimer [M(C₆F₅)(tht)(μ-Cl)₂] (M = Pd 1b, Pt 2b; tht = tetrahydrothiophene) and the corresponding bidentate ligand. In the case of palladium, the corresponding iodo analogues (6a–c) were readily synthesized in a one-pot reaction from [Pd₂(dba)₃], iodopentafluorobenzene, and the appropriate ligand. The platinum complexes 4c–d were then converted to the water complexes [Pt(L–L)(C₆F₅)(OH₂)]OTf (L–L = dmpe 7a; dcpe 7b) via reaction with AgOTf in the presence of water. Attempts to convert the palladium complexes 3c–d to the corresponding water complexes resulted in the disproportionation of the intermediate water complex to form [Pd(L–L)(C₆F₅)₂] (L–L = dmpe 8) or [Pd(L–L)₂][OTf]₂ (L–L = dcpe 9). Upon standing in solution for prolonged periods, complex 7a undergoes an identical disproportionation reaction to the Pd analogues to form [Pt(L–L)(C₆F₅)₂] (L–L = dmpe 10). Complexes 4c and 4d were converted to the corresponding hydrides (11b–c, respectively) using two different hydride sources: 11a was formed by the reaction of 4c with NaBH₄ in refluxing THF, while 11b was synthesized in near quantitative yield using [Cp₂ZrH₂] in refluxing THF. Attempts to synthesize η²-tetrafluorobenzyne complexes [Pt(L–L)(C₆F₄)] (L–L = dmpe, dcpe) from reaction of 11a–b with butyllithium were unsuccessful. The molecular structures of 3a, 4a, 4c, 4d, 6b, 7a, 8, and 11b have been determined by X-ray crystallographic studies, and are discussed.