Reactivity of cyclopalladated compounds: VIII. Synthesis of cyclometallated compounds with an oxygen as the donor atom. Crystal and molecular structure of (8-methylquinoline- C,N)-(1-methoxynaphthalene-8- C,O)palladium(II)

Abstract

Treatment of 1-methoxynaphthalene (MXNH) with n-butyllithium in a diethyl ether/n-hexane solution gives 1-methoxynaphthalene-8-lithium (MXNLi) in 30% yield as an insoluble material. This compound reacts with PdCl 2(SEt 2) 2 to give bis(1-methoxynaphthalene-8- C,O)palladium(II) (I)_and with PtCl 2(SEt 2) 2 to give cis- and trans-(1-methoxynaphthalene-8- C,O)(1-methoxynaphthalene-8- C)(diethylsulfide)platinum(II) (II), which are non-rigid molecules in solution. With the cyclopalladated dimers [{ Pd(CN )Cl 2} 2], MXNLi gives the palladobicyclic compounds: ( N∩C)P d(C∩O ) (III). An X-ray diffraction study of compound IIIa where N∩N = 8-methylquinoline- C,N reveals the planarity of the molecule, shows that it has a cis configuration with respect to the PdC bonds, and confirms that the oxygen atom of MXN is bonded to palladium: PdO 2.236(4) Å. The geometry of IIIa is maintained in solution, whereas the corresponding compounds IIIb and IIIc in which N∩C is benzo[ h]quinoline-9- C,N and N,N-dimethyl-1-naphthylamine-8- C,N, respectively, appear to be mixtures of cis and trans isomers in solution. With PMe 2Ph I and II give trans-Pd(MXN) 2(PMe 2Ph) 2 and cis-Pt(MNX) 2(PMe 2Ph) 2, respectively, in which the methoxynaphthalene is bound to the metals via the 8-carbon of the naphthalene ring. Only one phosphine ligand adds to compounds IIIb and IIIc with displacement of the O → Pd bond. One carbon monoxide ligand can be added to the platinum compound II to give Pt(MXN) 2(SEt 2)CO which in solution exists as two isomers in equilibrium.