REACTIVITY OF TETRANUCLEAR CYCLOMETALATED PALLADIUM(II) HALIDE-BRIDGED COMPLEXES OF BIS(N-BENZYLIDENE)-1,4-PHENYLENEDIAMINES

Treatment of the cyclometallated halide-bridged complexes [{1,4-(Pd[2,3,4-(MeO)3C6HC(H)=N](X)}2C6H4}2] (Ia, IIa) and [{1,4-{Pd[2,4-(MeO)2C6H2C(H)=N(X)}2C6H4}2] (Ib, IIb) (X = Cl or Br) with ditertiary diphosphines in a complex/ diphosphine 1:2 molar ratio gave the 26- and 28-membered ring tetranuclear cyclometallated complexes [1,4-{{Pd[2,3,4-(MeO)3C6-HC(H)=N](X)}2C6H4}2{mu-Ph2P(CH2)nPPh2}2] (1a: X = Cl, n = 3; 2a: X = Br, n = 3; 3a: X = Cl, n = 4; 4a: X = Br, n = 4) and [1,4-{{Pd[2,4-(MeO)2C6H2C(H)=N](X)}2C6H4}2{mu-Ph2P(CH2)nPPh2}2] (1b: X = Cl, n = 3; 2b: X = Br, n = 3; 3b: X = Cl, n = 4; 4b: X = Br, n = 4) and in a complex/ diphosphine 1:4 molar ratio gave the dinuclear cyclometallated complexes [1,4-{Pd[2,3,4-(MeO)3C6HC(H)=N]}2C6H4{Ph2P(CH2)nPPh2-P,P}2][PF6]2 (5a: n = 3; 6a: n = 4) and [1,4-{Pd[2,4-(MeO)2C6-HC(H)=N]}2C6H4}{Ph2P(CH2)nPPh2-P,P)2][PF6]2 (5b: n = 3; 6b: n = 4). Treatment of the cyclometallated halide-bridged complexes [{1,4-{Pd[2,3,4-(MeO)3C6HC(H)=N](X)}2C6H4}2] (Ia, IIa) and [{1,4-{Pd[4,5-(OCH2O)C6H2C(H)=N](X)}2C6H4}2] (Ic, IIc) (X = Cl, Br) with tertiary monophosphines in a complex/phosphine 1:4 or 1:8 molar ratio gave the new dinuclear cyclometallated complexes [1,4-{Pd[2,3,4-(MeO)3C6HC(H)=N](X)(L)}2C6H4] [L = PPh3: 7a (X = Cl), Sa (X = Br); L = PPhEt 2: 9a (X = Cl), 10a (X = Br); L = PPh(C=CPh)2: 11a (X = Cl), 12a (X = Br)] and [1,4-{Pd[4,5-(OCH2O)C6H2C(H)=N](X)(L)}2C6H4] [L = PPh3: 7C (X = Cl), 2c (X = Br); L = PPhEt2: 3c (X = Cl), 4c (X = Br); L = PPh(CPh)2: 5c (X = Cl), 6c (X = Br)] and non-cyclometallated complexes [1,4-{Pd[2,3,4-(MeO)3C6HC(H)=N(X)(L)2)2C6H4] [L = PPh3: 13a (X = Cl), 14a (X = Br); L = PPhEt2: 15a (X = Cl), 16a (X = Br); L = PPh(C=CPh)2: 17a (X = Cl), 18a (X = Br)] and [1,4-(Pd[4,5-(OCH2O)C6H2C(H)=N](X)(L)2}2C6H4] [L = PPh3: 7c (X = Cl), 8c (X = Br); L = PPhEt2: 9c (X = CI), 10c (X = Br); L = PPh(C=Ph)2: 11C (X = Cl), 12c (X = Br)], respectively. Reaction of the halide-bridged complexes with thallium acetylacetonate gave the dinuclear cyclometallated complexes [1,4-{Pd[2,3,4-(MeO)3C6HC(H)=N]H3CCOCHCOCH3)}2C6H4] (19a) and [1,4-(Pd[4,5-(OCH2O)C6H2C(H)=N]H3CCOCHCOCH3)}2C6H4] (13c). The compounds were characterized by microanalysis (C, H, N), IR and P-31(H-1) and H-1 spectroscopy.