The cyclotetramerisation of dimethyl acetylenedicarboxylate and the x-ray structure of [pd{h(c8(co2me)8)}cl(pyridine)2], an unusual five-co-ordinate palladium(ii) complex

Reaction of dimethyl acetylenedicarboxylate with PdCl2 in methanol yields [Pd{HC8(CO2Me)8}Cl]2, which gives monomeric and non-conducting adducts [Pd{HC8(CO2Me)8}ClL2]; an X-ray structure determination of the adduct (L = pyridine) shows it to contain five-co-ordinate PdII.