Crystal structure of dicarbonyl(1,4-difluoro-2,3,5,6-tetramethyl-1,4-diboracyclohexa-1,5-dienyl)nickel(0): a complex with a ligand analogous to duroquinone

Abstract

Crystals of the title compound were found to contain two crystallographically distinct molecules of free ligand for every two molecules of the nickel dicarbonyl complex. These crystals were monoclinic, space group A2/m, with Z= 4, in a unit cell of dimensions a= 11.904(7), b= 15.505(8), c= 12.584(4)Å, β= 110.07(4)°. The structure has been elucidated by conventional heavy-atom methods from 950 independent diffracted intensities measured on a diffractometer and refined to R 0.069 (R′ 0.067). The nickel atom is in a tetrahedral environment if the main bonding directions are considered to be to the two carbonyl groups and to the ethylenic bonds of the dibora-hexadiene ring, although all six atoms of the ring are within bonding distance of the metal atom. As in the sandwich analogue, [Ni(C₄Me₄B₂F₂)₂], the ligand ring is significantly non-planar, the B atoms bending away from the metal. Differences in bond lengths between the free ligand, the carbonyl complex, and the sandwich compound are discussed.