Cyclometallation of phenylhydrazones: Synthesis, reactivity, crystal structure analysis and novel trinuclear palladium(II) cyclometallated compounds with [C,N,N '] terdentate ligands

摘要

Reaction of the ligand C6H5N(H)N=CMe(C5H4N) (a) with palladium(II) acetate in toluene gave the mononuclear cyclometallated complex [Pd{C6H4N(H)N=CMe(C5H4N)}(AcO)] (1a). Reaction of la with sodium chloride gave the analogous chlorine compound [Pd{C6H4N(H)N=CMe(C5H4N)}(Cl)] (3a) which could also be prepared by reaction of a with lithium tetrachloropalladate and sodium acetate in methanol for 48 h; whereas shorter reaction times afforded the non-cyclometallated complex [Pd{C6H5N(H)N=CMe(C5H4N)} (Cl)(2)] (2a). Reaction of the ligand 2-ClC6H4N(H)N=CMC(C5H4N) (.) HCl (b), with palladium(II) acetate, or with lithium tetrachloropalladate and sodium acetate, yielded the cyclometallated complex [Pd2-ClC6H3N(H)N=CMe(C5H4N)(Cl)] (1b). Treatment of 3a and 1b with silver trifluoromethanesulphonate (triflate) and triphenylphosphine in acetone gave the mononuclear complexes [Pd{2-RC6HnN(H)N=CMe(C5H4N)}(PPh3)][CF3SO3], (R = H, n = 4, 4a; R = Cl, n = 3, 2b) with the ligand as C,N,N' terdentate and substitution of chlorine by triphenylphosphine. Reaction of 3a and 1b with silver triflate and the tertiary diphosphine Ph2P(CH2)(4)PPh2 (dppb) in a 2:1 molar ratio gave the dinuclear cyclometallated complexes [{Pd[2-RC6H3N(H)N=CMe(C5H4N)]} (2)(mu-Ph2P(CH2)(4)PPh2)][CF3SO3](2) (R = H, 5a; R = Cl, 3b) with a mu(2)-diphosphine bridging ligand. Similarly, treatment of 3a and 1b with silver triflate and the tertiary triphosphines MeC(CH2PPh2)(3) (tripod) and (Ph2PCH2CH2)(2)PPh (triphos), in 3:1 molar ratio gave the novel trinuclear complexes [{Pd[C6H4N(H)N=CMe(C5H4N)}(3){PPh2CH2CH2Ph2)(3)}][CF3SO3](3) (6a) and [{Pd[2-ClC6H3N(H)N=CMe(C5H4N)]}(3){[mu(3)-(Pph(2)cH(2)CH(2))(2)PPh][CF3SO3](3) (4b) regioseklectively, with the phosphine as a mu(3)-bridging ligand. When the reaction between 3a and triphos was carried out in 1:1 molar ratio the mononuclear complex [Pd{C6H4N(H)N=CMe(C5H4N)}{(PPh2CH2CH2)(2)PPh-P,P,P}][ClO4] (7a) was obtained. The crystal structures of 2b, 3a and 4a have been determined by X-ray crystallography. (c) 2005 Elsevier B.V. All rights reserved.