Synthesis, characterization and crystal structures of cyclometallated palladium (II) compounds containing difunctional ligands with [P,P], [As,As], [N,N], [P,As], [P,N] and [P,O] donor atoms

Treatment of the chloro-bridged dinuclear complex [Pd{3,4-(MeO)2C6H2C(H)N(Cy)-C6,N}(μ-Cl)]2 (1) with homobidentate [P,P], [As,As], [N,N], and heterobidentate [P,As], [P,N] ligands in a 1:1 molar ratio gave the dinuclear complexes [{Pd[3,4-(MeO)2C6H2C(H)N(Cy)-C6,N](Cl)}2{μ-L}] (L = Ph2PC4H6(NH)CH2PPh2 (2); Ph2As(CH2)2AsPh2 (3); 1,3-(NH2CH2)2C6H4 (4); Ph2P(CH2)2AsPh2 (5); Ph2P(CH2)2NH2 (6)), with the bidentate ligands bridging the two cyclometallated fragments.The reaction with the homobidentate ligands in a 1:2 molar ratio in the presence of NaClO4 afforded the mononuclear compounds [[Pd{3,4-(MeO)2C6H2C(H)N(Cy)-C6,N}{L-P,P}][ClO4] (L = Ph2PC4H6(NH)CH2PPh2 (7); (o-Tol)2P(CH2)2P(o-Tol)2 (8)), [Pd{3,4-(MeO)2C6H2C(H)N(Cy)-C6,N}{Ph2As(CH2)2AsPh2-As,As}][ClO4] (9) and [Pd{3,4-(MeO)2C6H2C(H)N(Cy)-C6,N}{L-N,N}][ClO4] (L = NH2(CH2)3NH2 (10); NH2(C6H8)CH2(C6H8)NH2 (11); 1,3-(NH2CH2)2C6H4 (12); 1,3-(NH2)2C5H3N (13); NH2(C6H4)O(C6H4)NH2 (14); NMe2(CH2)2NMe2 (15)), in which the chloro ligands are absent and the bidentate ligands are chelated to the palladium atom.Reaction of 1 with Ph2P(CH2)2AsPh2 in 1:2 molar ratio in acetone in the presence of NH4PF6 afforded the analogous mononuclear compound [Pd{3,4-(MeO)2C6H2C(H)N(Cy)-C6,N}{Ph2P(CH2)2AsPh2-P,As}][PF6] (16); whereas reaction with Ph2P(CH2)3NH2 gave [Pd{3,4-(MeO)2C6H2C(H)N(Cy)-C6,N}{Ph2P(CH2)3N(CMe2)-P,N}][PF6] (17), derived from intermolecular condensation between the aminophosphine and acetone. Condensation of the NH2 group was precluded by change of solvent, using dichloromethane.Iminophoshines also reacted with 1 in 1:2 molar ratio in acetone to give a new series of mononuclear cyclometallated complexes: [Pd{3,4-(MeO)2C6H2C(H)N(Cy)-C6,N}{L-P,N}][ClO4] (L = Ph2PC6H4C(H)NCy (20); Ph2PC6H4C(H)NC(CH3)3 (21); Ph2PC6H4C(H)NNMe2 (22); Ph2PC6H4C(H)NNHMe (23); Ph2PC6H4C(H)NNHPh (24)). Analogous complexes with a stable P,O-chelate were obtained using bidentate [P,O] donor ligands: [Pd{3,4-(MeO)2C6H2C(H)N(Cy)-C6,N}{L-P,O}][Cl] (L = 2-(Ph2P)C6H4CHO (25); Ph2PN(Me)C(O)Me (26)).The crystal structures of compounds 1, 5, 15, 16, 18, 20 have been determined by X-ray crystallography.

Graphical abstractThe synthesis and characterization of the new cyclometallated palladium(II) complexes bearing ligands with [P,P], [As,As], [N,N], [P,As], [P,N] and [P,O] donor atoms is described. Ligands bearing amino groups may give condensation reactions with the solvent The crystal and molecular structure of 3 has been determined and shows the palladium atom is bonded to four different donor atoms: C, N, S and Cl. Treatment of 3 with tertiary phosphines generates a series of mono-and dinuclear complexes and the reaction conditions may be regulated to give compounds where the Pd–S bond either remains or is cleaved. The reactivity of compound 3 is described.Figure optionsDownload full-size imageDownload as PowerPoint slide