Metal complexes of 1,4-difluoro-2,3,5,6-tetramethyl-2,5-diboracyc1ohexa-1,4-diene, an analogue of duroquinone. Crystal structure of bis(1,4-difluoro-2,3,5,6-tetramethyl-1,4-diboracyclohexa-2,5-diene)nickel(0)

Abstract

1,4-Difluoro-2,3,5,6-tetramethyl-1,4-diboracyclohexa-2,5-diene, (I), displaces carbon monoxide from metal carbonyls directly or on photolysis to form complexes including [(C₄Me₄B₂F₂)Ni(CO)₂](II), [(C₄Me₄B₂F₂)₂Ni](III), [(C₄Me₄B₂F₂)(C₅H₅)Co], and [(C₄Me₄B₂F₂)Fe(CO)₃]. A single-crystal X-ray study of (III) shows it to have a sandwich structure with idealised D_2d symmetry, the nearly planar rings being conversely orientated. All six atoms of each ring are bonded to the metal. Both the molecular structure and spectroscopic properties of the complexes are remarkably like those of the isoelectronic complexes of duroquinone. Crystals of (III) are monoclinic, space group C2/c, a= 17·569(3), b= 6·671(1), c= 17·270(3)Å, β= 116·06(1)°, Z= 4. The structure was solved by the heavy-atom method and refined by least-squares techniques R 0·057 for 2165 independent reflections measured by diffractometer.