Complexes of palladium(II) and platinum(II) thiocyanates with some bidentate amine, phosphine, arsine, sulphide, and selenide ligands

Abstract

The bidentate ligands CH2(PPh2S)2, CH2(PPh2Se)2, and CH2(AsPh2S)2 all form thiocyanato-S complexes [M(L–L)(SCN)2](L–L = bidentate ligand, M = Pd or Pt) with palladium(II) and platinum(II) thiocyanates. Reactions of 1,2-bis(diphenylphosphino)ethane with K2[Pd(SCN)4] yield, in addition to the previously reported [Pd(Ph2PC2H4PPh2)2][Pd(SCN)4] and [Pd(Ph2PC2H4PPh2)(NCS)(SCN)], a salt [Pd(Ph2PC2H4PPh2)2][CNS]2 and probably also a thiocyanato-N complex [Pd(Ph2PC2H4PPh2)(NCS)2]; corresponding reactions with K2[Pt(SCN)4] yield only the salts [Pt(Ph2PC2H4PPh2)2][Pt(SCN)4] and [Pt(Ph2PC2H4PPh2)2][CNS]2, with no evidence for the formation of neutral mixed-ligand complexes [Pt(Ph2PC2H2PPh2)(CNS)2]. Bis(diphenylarsino)methane forms a neutral 1 : 2 palladium complex [Pd{CH2(AsPh2)2}2(SCN)2] which appears to have a monomeric octahedral structure in the solid; with platinum(II) thiocyanate the products are four-co-ordinate [Pt{CH2(AsPh2)2}(NCS)(SCN)] and [Pt{CH2(AsPh2)2}2][CNS]2. Unlike 2,2′-bipyridyl, which forms thiocyanato-N complexes, di-2-pyridylamine and di-2-pyridyl ketone form thiocyanato-S complexes with both palladium(II) and platinum(II) thiocyanates at room temperature: this behaviour is consistent with the less complete conjugation and greater steric requirements of the amine and ketone ligands.