Oxidative addition of iodo-acetonitrile and of elemental halogens to [Pt3(μ-CO)3(PCy3)3]

The reaction of [Pt-3(mu-CO)(3)(PCy3)(3)] (1) with one mole-equivalent of iodo-acetonitrile was quantitative at -70degreesC giving the oxidative addition product [Pt-3(mu-CO)(3)(PCy3)(3)(I)(CH2CN)] (2). Fragmentation of 2 was observed in solution giving [Pt2I(CH2CN)( CO)(2)(PCy3)(2)] (3) which is the major product at room temperature if the starting cluster/reactant ratio is equal to or less than 1 to 1.5. Dimer 3 decomposes slowly in solution giving [Pt2I2(CO)(2)(PCy3)(2)] (4a) and succinonitrile. Monomer [PtI(CH2CN)(CO)(PCy3)] was the final product of the reaction when using excess of iodo-acetonitrile. The reactions of 1 with one mole-equivalent of halogens X-2 gave the new 44-electron clusters [Pt3X(mu-CO)(2)(mu-X)(PCy3)(3)] (X = I-2 (7a) or Br-2 (7b)) by oxidative addition followed by substitution of CO by X-. Fragmentation of 7a and 7b took place in solution when using one and a half mole-equivalents of X-2 giving dimers 4a and [Pt2Br2(CO)(2)(PCy3)(2)] (4b) as well as [Pt2X2(mu-X)(2)(CO)(2)(PCy3)(2)]. Monomers cis-[PtX2(CO)(PCy3)] were the final products of the reaction of 1 with excess of halogens. Insertion of SnCl2 was observed into the Pt-Pt bond but not into the Pt-X bond, when equimolar amounts of SnCl2.2H(2)O were added to a solution of 4a or its chloro-analogue giving [Pt2X2(mu-SnCl2)(CO)(2)(PCy3)(2)]. The Pt(I) dimers have unusually small J(Pt-Pt) values as observed by Pt-195 NMR and calculated by DFT. These values showed periodic changes comparing 4a and its analogues with other halides and mixed halide dimers.