CATIONIC METHALLYLNICKEL COMPLEXES WITH CHELATING LIGANDS - A NEW DYNAMIC COMPLEX ISOMERIZATION EQUILIBRIUM

The synthesis of the cationic complexes [methyl )benzoate-kappa(2)P,O] (eta(3)-methallyl)nickel(II) tetrafluoroborate (1), [methyl icotinate- kappa(2)P,N](eta(3)-methallyl)nickel(II) tetrafluoroborate (2), and bi s[mu-2-(diphenylphosphino)pyridine kappa(2)P,N]bis(eta(3)-methallyl)ni ckel(II) bis(tetrafluoroborate). CH2Cl2 (3) are reported. The crystal structures of 1 and 2 have been disclosed in a preliminary previous pa per. The molecular structure of the cation of 2 in the crystal shows t hat the ligand forms a strained 4-membered ring with a kappa(2)P,N coo rdination. In solution a new dynamic complex isomerization was found, indicating an equilibrium between 2 and 4, the latter with a 6-membere d ring and a kappa(2)P,O coordination of the ligand methyl 2-(diphenyl phosphino)nicotinate (5).