ACETAMIDE COORDINATION IN A NICKEL(I) MACROCYCLIC COMPLEX - SYNTHESIS, PROPERTIES, AND X-RAY CRYSTAL-STRUCTURE OF A 5-COORDINATE NICKEL(I) IMINOL COMPLEX OF 3,6,8,12,15-HEXAAZATRICYCLO[13.3.1.1(8,12)]ICOSANE

A five-coordinate Ni(I) macrocyclic complex, (R,S,R,S)-[Ni(L)(NHC(OH)C H3)]ClO4, where L is 1,3,6,8, 12,15-hexaazatricyclo[13.3.1.1(8,12)]ico sane has been prepared by the reduction of Ni(II) complex (R,R,S,S)-[N i(L)]-(ClO4)(2) . 1/2H(2)O With Na(Hg) in MeCN under a nitrogen atmosp here. In the formation of the complex, the solvent MeCN was hydrated t o acetamide and coordinated to the Ni(I) ion. The complex shows rhombi c EPR spectra with the powder sample or in the frozen MeCN solution. I t equilibrates with four-coordinate (R,R,S,S)-[Ni(L)](+) in MeCN. [Ni( L)(NHC(OH)CH3)]ClO4 (NiC16H35N7O5Cl) crystallizes in the orthorhombic space group Pbca with a = 10.053(5) Angstrom, b = 14.120(3) Angstrom, c = 31.005(3) Angstrom, and Z = 8. The structure was solved by the dir ect method and refined to R values of R(1) = 0.0500 and omega R(2) = 0 .0983 for 2153 unique reflections measured with Mo Ka radiation on a C AD-4 diffractometer. The Ni(I) ion of the complex has square-pyramidal geometry with an acetamide coordinating in the iminol form at the api cal position. The complex shows two sets of Ni-N(macrocycle) bond dist ances: 2.092(3) Angstrom (av) for Ni-N(sec) and 2.135(3) Angstrom (av) for Ni-N(tert), which are significantly longer than those of the squa re-planar Ni(I) complex (R,R,S,S)-[Ni(L)]ClO4. The Ni-N(iminol) bond d istance is 1.969(5) Angstrom. The three bonds of Ni-N-C-O involving an iminol group have multiple bonding character.