Structural Preferences in Phosphanylthiolato Platinum(II) Complexes

The transition‐metal complexes of heterotopic phosphanylthiolato ligands are useful in various reactions which depend on the stereochemistry of the complexes. Bis‐chelate complex [Pt(SCH₂CH₂PPh₂‐κ²P,S)₂] (1) was obtained in good yields by direct base‐free substitution reaction of the corresponding phosphanylthiol (HSCH₂CH₂PPh₂) with K₂PtCl₄ or by oxidative addition of the same phosphanylthiol to Pt(PPh₃)₄. In agreement with the antisymbiosis rule, complex 1 shows a cis‐P,P arrangement in solid state crystallizing in the monoclinic system (C2/c). Density functional theory (DFT) calculations on 1 reveal the right characteristics for the preferred cis‐P,P arrangement, rationalizing its formation. Direct base‐free reaction of [PtCl₂(1,5‐cyclooctadiene)] with one equivalent of the same phosphanylthiol produce the trinuclear complex [PtCl(μ‐SCH₂CH₂PPh₂‐κ²P,S)]₃ (2) instead of the binuclear structure common in palladium and nickel derivatives. Crystals of 2 are triclinic (P1‾ ) showing a sulfur‐bridging edge‐sharing cyclic trinuclear complex with square‐planar coordination geometry around the platinum atoms and a Pt₃S₃ cycle in skew‐boat conformation. This preference for the trinuclear structure was rationalized mechanistically and through conceptual DFT.

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

Reaction of the ditopic phosphanylarylthiol 1-P(Biph)-2-SHC(6)H(4) (BiphPSH, Biph = 1,1'-biphenyl-2,2'-diyl), prepared by lithiation-electrophilic substitution, with NiCl(2)·6H(2)O, Na(2)[PdCl(4)] and [PtI(2)(cod)] (cod = 1,5-cyclooctadiene) in a 2:1 ratio and in the presence of NEt(3) led to formation of exclusively cis isomers of the square-planar complexes cis-[M{(1-P(Biph)-2-S-C(6)H(4))-κ(2)S,P}(2)] ([M{(BiphPS)-κ(2)S,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(III) complex. Small amounts of the trinuclear complex [{PtI(1-P(Biph)-μ-2-S-C(6)H(4)-κ(2)S,P)}(3)] (4) are also formed besides the mononuclear platinum bis-chelate complex 3.