Reactivities of organic isothiocyanates and thiocyanates toward dialkyl bis(phosphine) complexes of palladium(II) and platinum(II)

Abstract

Room-temperature reactions of trans-[PdEt2L2] (L=PMe3, PEt3, PMe2Ph) with organic isothiocyanates [R–NCS; R=benzyl; CH(CH3)Ph, R-(−) and S-(+); indanyl, S-(+)] afforded the S,S-coordinated Pd(II) complexes [Pd(S2CN–R)L2] containing a dithiocarbonimidato (S2CN–R) group. Similar reactions involving allyl isothiocyanates produced the cationic η3-allyl Pd complex [Pd(η3-allyl)(PMe3)2]+(NCS)−. When [Pd(S2CN–R)(PMe3)2] was treated with 1equiv of a chelating phosphine [L–L=depe (1,2-bis(diethylphosphino)ethane) and dmpe (1,2-bis(dimethylphosphino)ethane)], the corresponding complexes [Pd(S2CN–R)(L–L)] were produced. Reactions of trans-[PdEt2L2] (L=PMe3, PMe2Ph) with organic thiocyanates (R–SCN; R=benzyl, Et) resulted in the formation of [Pd(CN)2L2] and an organic disulfide by S–C bond cleavage of R–SCN. However, similar reactions of the dimethyl analogs, trans-[PdMe2L2] (L=PMe3, PEt3), with benzyl thiocyanate afforded different products, [Pd(NCS)2L2] or [PdMe(NCS)L2]. Treating [Pt(styrene)(PMe3)2] with benzyl isothiocyanate gave the S-coordinated dithiocarbonimidato Pt(II) complex, [Pt(S2CN–R)(Me3P)2] (R=benzyl). In contrast, cis-[PtEt2(PMe3)2] reacted with the isothiocyanate to afford the trialkyl Pt(IV) complex [PtEt2(SCN)(CH2Ph)(PMe3)2].