Cyclometallated imine complexes with oxygen-functionalised side-chains: Effect of the nature of the functional group, chain length and charge on coordination of the oxygen

Imines 1a-e derived from benzaldehyde or 3,4-dimethoxy benzaldehyde and ether- or alcohol-functionalised amines H₂NR (R = C₂H₄OMe, C₃H₆OMe, C₂H₄OH, C₃H₆OH,) all undergo cyclometallation with [Pd(OAc)₂]₃ (in some cases the dimeric products 2 were isolated) and subsequently react with lithium chloride to give chloride complexes, which are dimeric 3a-c, or monomeric for the C₃H₆OH-functionalised complexes 4d,e which have a C,N,O tridentate imine. The chloride complexes subsequently react with triphenylphosphine, and in some cases pyridine, to give mononuclear complexes 5 and 6, respectively with bidentate C,N imines. Treatment of 5 with silver salts leads to cations, the length of the tether (C2 or C3) and nature of the donor (ether or alcohol) and the counterion all effect whether or not the oxygen is coordinated.