A NOVEL TRIDENTATE COORDINATION MODE FOR THE CARBONATONICKEL SYSTEM

The trinuclear compound Co-3)(dmpd)(4)(H2O)][Ni(dmpd)(2)(H2O)(2)][ClO4 ](4) . H2O was obtained from the reaction of basic solutions of nickel (II) perchlorate and 2,2-dimethylpropane-1,3-diamine (dmpd) with atmos pheric CO2 It crystallises in the orthorhombic system, space group Pca b, with a = 18.634(10), b = 25.447(8), c = 25.598(4) Angstrom, Z = 8, R = 0.0437. The three nickel atoms show octahedral co-ordination with three different environments; Ni(CO3-O,O')(dmpd)(2), Ni(CO3-O '')(dmpd )(2)(H2O) and Ni(dmpd)(2)(H2O)(2). The carbonate anion acts as a bridg e between two nickel ions whereas the [Ni(dmpd)(2)(H2O)(2)](2+) subuni t is linked by hydrogen bonds to the dinuclear group. The dinuclear [N i-2(mu-CO3)(dmpd)(4)(H2O)](2+) subunit shows a moderately weak antifer romagnetic coupling with a J value of -7.8 cm(-1). The tridentate co-o rdination mode found in the carbonate ligand has not previously been r eported for nickel. Its magnetic behaviour is discussed.