Synthesis of mu-Picolyl Platinum-Group Clusters Directed toward an Appearance of Catalytic Ability

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The research results of this project on oxidative-addition reactions of 2-(chloro-methyl)- and 2,6-bis(chloromethyl) pyridines (MPY and DMPY) are summarized as follows.1 Oxidative-addition reactions of DMPY to Pd(PPh_3)_4 in toluene at 100ﾟC afforded the dinuclear Pd(II) complex 1, in which the 2,6-dimenthylpyridine-alpha, alpha'-diyl groups are C,N,C'-bridging.2 Complex 2 could be also prepared by the reaction of 1 with Pd(PPh_3)_4. Application of this synthetic method was successful in obtaining the Pd-Pt heterometal tetranuclear complex 3. This complex consists of a mixture of three kinds of isomers arising from combinations of the heterometal atoms and their separation is not still attained.3 Each two Pd-centers inside and outside of 2 have the different coodination-circumstances, and hence the ligand substitution reactions dicriminated their reaction cites.4 On the other hand, the reactions of MPY and DMPY with RhCl(PPh_3)_3 in toluene at room temperature afforded the mononulear cis(PP)-Rh(III) complexes 4-cis and 5-cis, in which the 2-pyridylmethyl and 2-(6-chloromethyl)pyridylmethyl groups are C,N-chelated respectively. The reactions in reflexing toluene gave 4-trans and 5-trans.5 Novel dinuclear Rh(III) complex, in which the 2,6-dimethylpyridine-alpha, alpha'-diyl group is C,N-chelated to the first Rh-center and bound to the second one in an eta^3-1-azaallylic fashion, has been obtained by the reaction of 5-cis with RhCl(PPh_3)_3 or reaction of DMPY with 2 equiv. of RhCl(PPh_3)_3.