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.