Cyclometallated compounds of Pd(II): CN to CO conversion through acid hydrolysis. Crystal and molecular structures of [Pd{4-(CHO)C6H3C(H)NCy}(Cl)(PPh3)2] and [Pd{2,4-(CHO)2C6H3}(Cl)(PPh3)2]

Treatment of the chloro-bridged complex [Pd{4-(CHO)C6H3C(H)NCy}(Cl)]2 (1) with tertiary monophosphines in a 1:4 molar ratio gave the non-cyclometallated monomer complexes [Pd{4-(CHO)C6H3C(H)NCy}(Cl)(PR3)2] (PR3: (2) PPh3, (3) PEtPh2, (4) PEt2Ph, (5) PMePh2). The crystal structure of 2 is described. Reaction of complexes 2–5 with a mixture of glacial acetic acid–water gave the monomeric complexes [Pd{2,4-(CHO)2C6H3}(Cl)(PR3)2] (PR3 (6), PPh3 (7), PEtPh2 (8), PEt2Ph (9), PMePh2) after cleavage of the CN group. Complex 6 was characterized crystallographically. Treatment of 1 with the triphosphine bis(2-diphenylphosphinoethyl)phenylphosphine in 1:2 molar ratio gave the mononuclear complex [Pd{4-(CHO)C6H3C(H)NCy}{Ph2P(CH2)2PPh(CH2)2PPh2-P,P,P}][Cl] (10) in which the phosphine is coordinated through the three phosphorus atoms. Treatment of 10 with a mixture of acetic acid–water also caused cleavage of the CN bond giving the complex [Pd{2,4-(CHO)2C6H3}{Ph2P(CH2)2PPh(CH2)2PPh2-P,P,P}][Cl] (11).