Novel structures of cyclometallated complexes of palladium(II) derived from terdentate ligands.: Crystal and molecular structure of [Pd{C6H4C(H)=NCH2CH2CH2NMe2}(X)] (X = Cl, Br, I)

Treatment of N-(2-chlorobenzylidene)-N,N-dimethyl-1,3-propanediamine (1) and N-(2-bromo-3,4-(MeO)(2)-benzylidene)-N,N-dimethyl-1,3-propanediamine (20) with tris(dibenzylideneacetone)dipalladium(0) in toluene gave the mononuclear cyclometallated complexes [Pd{C6H4C(H)=NCH2CH2CH2NMe2}(Cl)] (2) and [Pd{3,4-(MeO)(2)C6H2C(H)=NCH2CH2CH2NMe2}(Br)] (21), respectively, via oxidative addition reaction with the ligand as a C,N,N terdentate ligand. Reaction of 2 with sodium bromide or iodide in an acetone-water mixture gave the cyclometallated analogues of 2, [Pd{C6H4C(H)=NCH2CH2CH2NMe2}(Br)] (3) and [Pd{C6H4C(H)=NCH2CH2CH2NMe2}(I)] (4), by halogen exchange. The X-ray crystal structures of 2, 3 and 4 were determined and discussed. Treatment of 2, 3, 4 and 21 with tertiary monophosphines in acetone gave the mononuclear cyclometallated complexes [Pd{C6H4C(H)=NCH2CH2CH2NMe2}(L)(X)] (6: L = PPh3, X = Cl; 7: L = PPh3, X = Br; 8: L = PPh3, X = I; 9: L = PMePh2, X = Cl; 10: L = PMe2Ph, X = Cl) and [Pd{3,4-(MeO)(2)C6H2C(H)=NCH2CH2CH2NMe2}(L)(Br)] (22: L = PPh3; 23: L = PMePh2; 24: L = PMe2Ph). A fluxional behaviour due to an uncoordinated CH2CH2CH2NMe2 could be determined by variable temperature NMR spectroscopy. Treatment of 2, 3 and 4 with silver trifluoromethanesulfonate followed by reaction with triphenylphosphine gave the mononuclear complex [Pd{C6H4C(H)=NCH2CH2CH2NMe2}(PPh3)][F3CSO3] (11) where the PdNMe2 bond was retained. Reaction of 2, 3 and 4 with ditertiary diphosphines in a cyclometallated complex-diphosphine 2:1 molar ratio gave the binuclear complexes [(Pd[C6H4C(H)=NCH2CH2CH2NMe2](X)}(2)(mu -L-L)][L-L = PPh2(CH2)(4)PPh2(dppb) (13, X = Cl; 14, X = Br; 15, X = I; L-L = PPh2(CH2)(5)PPh2(dpppe): 16, X = Cl; 17, X = Br; 18, X = I) with palladium-NMe2 bond cleavage. Treatment of 2, 3 and 4 with ditertiary diphosphines, in a cyclometallated complex-diphosphine 2:1, molar ratio and AgSO3CF3 gave the binuclear cyclometallated complexes [{Pd[C6H4C(H)=NCH2CH2CH2NMe2]}(2)(mu -L-L)][F3CSO3](2) (11: L-L = PPh2(CH2)(4)PPh2(dppb), X = Cl; 12: L-L = PPh2(CH2)(5)PPh2 (dpppe), X = Cl). Reaction of 2 with the ditertiary diphosphine cis-dppe in a cyclometallated complex-diphosphine 1:1 molar ratio followed by treatment with sodium perchlorate gave the mononuclear cyclometallated complex [Pd{C6H4C(H)-NCH2CH2CH2NMe2}(cis-PPh2CH=CHPPh2-P,P)][ClO4] (19). (C) 2001 Elsevier Science B.V. All rights reserved.