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)

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 center dot 6H(2)O, Na-2[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)-kappa S-2,P}(2)] ([M{(BiphPS)-kappa S-2,P}(2)]; M = Ni (1), Pd (2), Pt (3)). Density functional calculations support the assumption that this is probably due to intramolecular pi-pi 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)-mu-2-S-C6H4-kappa S-2,P)}(3)] (4) are also formed besides the mononuclear platinum bis-chelate complex 3.