Heteropolytopic phosphanylarylthiolato ligands: formation of cis isomers of nickel(ii), palladium(ii) and platinum(ii) complexes with 1-P(Biph)-2-SHC6H4 (Biph = 1,1′-biphenyl-2,2′-diyl)

Abstract

Reaction of the ditopic phosphanylarylthiol 1-P(Biph)-2-SHC₆H₄ (BiphPSH, Biph = 1,1′-biphenyl-2,2′-diyl), prepared by lithiation–electrophilic substitution, with NiCl₂·6H₂O, Na₂[PdCl₄] and [PtI₂(cod)] (cod = 1,5-cyclooctadiene) in a 2 : 1 ratio and in the presence of NEt₃ led to formation of exclusively cis isomers of the square-planar complexes cis-[M{(1-P(Biph)-2-S-C₆H₄)-κ²S,P}₂] ([M{(BiphPS)-κ²S,P}₂]; M = Ni (1), Pd (2), Pt (3)). Density functional calculations support the assumption that this is probably due to intramolecular π–π interaction of the biphenyl groups, which results in enhanced stability of the cis isomers. Compound 1 is the first example of a structurally characterised mononuclear cis-bis(phosphanylthiolato)nickel(II) complex. Small amounts of the trinuclear complex [{PtI(1-P(Biph)-μ-2-S-C₆H₄-κ²S,P)}₃] (4) are also formed besides the mononuclear platinum bis-chelate complex 3.