76173-82-5Relevant articles and documents
Dichromium(II) compounds containing 2-phenylbenzoic acid (biphCO2H): [Cr2(O2Cbiph)4]2 and Cr2(O2Cbiph)4(THF)2
Albert Cotton,Lon Thompson
, p. 1292 - 1296 (2008/10/08)
The reaction of dichromium tetraacetate with 2-phenylbenzoic acid, biphCO2H, in presence of n-butyllithium in THF, gives red, crystalline Cr2(O2Cbiph)4(THF)2 (1). The reaction also occurs in toluene, and from the deep red solution red crystalline [Cr2(O2Cbiph)4]2·4C 7H8 (2) is precipitated upon cooling. Both of these compounds have been fully characterized by X-ray crystallography; 1 crystallizes in space group P21/n with cell dimensions a = 10.955 (2) A?, b = 17.771 (3) A?, c = 13.450 (3) A?, β = 103.58 (2)°, V = 2545 (2) A?3, and Z = 2. Crystallographically centrosymmetric molecules with axially coordinated THF molecules are present in which the Cr-Cr and Cr-O(THF) distances are 2.316 (3) and 2.275 (6) A?, respectively. For compound 2 the space group is C2/c with cell dimensions of a = 25.335 (2) A?, b = 19.233 (4) A?, c = 22.138 (3) A?, β = 103.28 (1)°, V = 10499 (5) A?3, and Z = 4 for the tetranuclear formula unit. Aside from interstitial toluene molecules, the asymmetric unit is the dinuclear Cr2(O2Cbiph)4 moiety. Pairs of these are linked by O→Cr bonds across a crystallographic inversion center. Thus, each Cr2(O2Cbiph)4 moiety has one axial bond (Cr-Cr-O = 164.5 (1)°; Cr-O = 2.309 (5) A?) and one vacant axial position. The Cr-Cr quadruple bond distance is 2.348 (2) A?.
