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RESEARCH PRODUCT

PREPARATION AND REACTIONS OF 2-PYRIDYLPLATINUM(II) COMPLEXES [PTCL(C5H4N-C2)(TERTIARY PHOSPHINE)2] - COMPOUNDS WITH A MARKEDLY NUCLEOPHILIC PYRIDINE NITROGEN ATOM

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Abstract The 2-pyridyl complex trans -[PtCl(C 5 H 4 N- C 2 )(PPh 3 ) 2 ] (I) can be prepared in high yield by oxidative addition of 2-chloropyridine to [Pt(PPh 3 ) 4 ]. The reaction of I with 1,2-bis(diphenylphosphino)ethane yields the cis derivative [PtCl(C 4 5 H 4 N- C 2 )(dppe)] (II). In polar solvents, the latter rearranges to the binuclear cationic complex [Pt(μ-C 5 H 4 N- C 2 , N )(dppe)] 2 Cl 2 . The reaction of I with [PdCl(η 3 -2-MeC 3 H 4 )] 2 (1/0.5 molar ratio) gives the products [PtCl(μ-C 5 H 4 N- C 2 , N )(PPh 3 )] 2 (IV) and [PdCl(η 3 -2-MeC 3 H 4 )(PPh 3 )]. 31 P NMR monitoring of the reaction suggests that PPh 3 transfer occurs in a binuclear platinum/palladium intermediate with a bridging 2-pyridyl ligand, and leads initially to a chloride-bridged species [Pt(μ-Cl)(C 5 H 4 -N- C 2 )(PPh 3 )] 2 , which then rearranges to the more stable compound IV. Complexes I and II are readly N -protonated by HCl or HClO 4 to give the cationic derivatives [PtCl(C 5 H 5 N- C 2 )(PPh 3 ) 2 ] + and [PtCl(C 5 H 5 N- C 2 )(dppe)] + . In dichloromethane or 1,2-dichloroethane, the terminal 2-pyridyl group of I and II is slowly N -alkylated by the solvent to give [PtCl{l-R)C 5 H 4 n- C 2 }(PPh 3 ) 2 ]Cl and [PtCl(l-R)C 5 H 4 N- C 2 (dppe)]Cl (R  CH 2 Cl or CH 2 CH 2 Cl).