Synthesis and coordination chemistry of a 14-membered macrocyclic ligand containing one phosphorus, two sulfur and one ambidentate sulfoxide donor sets

The macrocyclic ligand PhP(CH2CH2SCH2CH2CH2)(2)SO (L) was obtained from the reaction between bis(3-chloropropyl) sulfoxide and bis(2-mercaptoethyl)phe nylphosphine in the presence of caesium carbonate. The ligand is stable in the solid state but rearranges slowly into the isomeric phosphine oxide S(C H2CH2CH2SCH2CH2)(2)P(O)Ph in solution. In the presence of molecular iodine, the oxygen migration process occurred spontaneously and the phosphine oxid e was obtained quantitatively within several minutes. When treated with [MC l2(CH3CN)(2)] (where M = Pd, Pt), the sulfinyl-substituted macrocycle funct ions as a bidentate ligand via its phosphorus and one of the thioether sulf ur donor atoms giving the corresponding neutral square-planar complexes cis -[M(L-P,S)Cl-2]. In both complexes, the sulfoxide group is not involved in metal complexation. However, when the dichloro complexes were treated with silver perchlorate, the corresponding tetradentate complexes [M{L-P,S,S,S}] [ClO4](2) were formed. In both the perchlorate salts, the ambidentate sulfo xide functions are coordinated to the metal centre via their sulfur donor. In contrast to the previously reported acyclic analogues, the sulfoxide-met al bonds are kinetically stable.