Cationic olefin complexes of platinum(II): Aspects of availability and reactivity

The series of complexes of formula [PtCl(h2-olefin)(N^N)]+, previously investigated for N^N = N,N,N0 ,N0-tetramethyl-ethylenediamine (Me4en), has been extended to the case of aromatic diimines 1,10-phenanthroline (phen) and 3,4,7,8-tetramethyl-1,10-phenanthroline (Me4phen) and to a variety of olefins (ethene, propene and styrene). The complexes have been prepared by reaction of the [PtCl3(h2-olefin)]-anions (K[PtCl3(h2-styrene)] reported here for the first time) with N^N in basic methanol. The initial [PtCl{h1-CH2-CH(R')-OMe}(N^N)] (R' = Me, Ph) complexes are formed in quantitative yield and as pure Markovnikov isomer. The reaction of the alkoxylic species with non coordinating acids, results in the quantitative formation of the desired cationic p-olefin complexes [PtCl(h2-olefin)(N^N)]+. The phenanthroline ligand confers peculiar properties to the new compounds. In particular, by reaction with triethylamine, [PtCl{h2-CH2=CH(Me)}(N^N)]+ species, undergo deprotonation of the olefin and formation of the dimeric species [{PtCl(N^N)}2(m-h1:h2-CH2CH=CH2)]+ which could be isolated and characterized. Interestingly such product in acetonitrile gives a disproportionation with precipitation of [PtCl2(phen)] and formation in solution of the new h3-allyl complex [Pt(h3-C3H5)(phen)]ClO4.