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

The 2-pyridyl complex trans-[PtCl(C5H4N-C2)(PPh3)2] (I) can be prepared in high yield by oxidative addition of 2-chloropyridine to [Pt(PPh3)4]. The reaction of I with 1,2-bis(diphenylphosphino)ethane yields the cis derivative [PtCl(C45H4N-C2)(dppe)] (II). In polar solvents, the latter rearranges to the binuclear cationic complex [Pt(μ-C5H4N-C2, N)(dppe)]2Cl2. The reaction of I with [PdCl(η3-2-MeC3H4)]2 (1/0.5 molar ratio) gives the products [PtCl(μ-C5H4N-C2, N)(PPh3)]2 (IV) and [PdCl(η3-2-MeC3H4)(PPh3)]. 31P NMR monitoring of the reaction suggests that PPh3 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)(C5H4-N-C2)(PPh3)]2, which then rearranges to the more stable compound IV. Complexes I and II are readly N-protonated by HCl or HClO4 to give the cationic derivatives [PtCl(C5H5N-C2)(PPh3)2]+ and [PtCl(C5H5N-C2)(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)C5H4n-C2}(PPh3)2]Cl and [PtCl(l-R)C5H4N-C2(dppe)]Cl (R CH2Cl or CH2CH2Cl). © 1989.