Ultraviolet irradiation of the cobaltacyclopentadiene complex (η5-C5H5)Co[C4(C6H5)4][P(C6H5)3], 1, in oxygenated CH2Cl2 or C6H6 solvents yields (η5-C5H5)Co[η4-OC(C6H5)C(C6H5)C(C6H5)C(C6H5)O], 2, and (η5-C5H5)Co[η4-C4(C6H5)4], 3. In the absence of O2 only 3 forms. Complexes 2 and 3 are formed by independent photochemical pathways with low quantum efficiencies (<5 × 10−4 at 366 and 313 nm). The crystal structure of complex 2 at −150 °C was determined. Unusual η4-OCCC bonding of the enedione π system of coordinated 1,2,3,4-tetraphenyl-cis-2-butene-1,4-dione (or (Z)-dibenzoylstilbene) is observed with a Co-O bond length of 1.936 (3) Åand Co-C bond lengths of 2.004 (5), 2.012 (5), and 2.066 (5) Å. There is a dihedral angle of only 10.2° between the cyclopentadiene and η4-OCCC planes. Crystals of 2 are monoclinic, space group C2h5—P21/n with four C33H25CoO2 formula units in a cell of dimensions, at −150 °C, of a = 17.128 (6) Å, b = 15.893 (3) Å, c = 9.097 (2) Å, and β = 101.92 (2)°. Least-squares refinement on 177 variables led to a final value of the R index on F2 of 0.106 for 4980 unique observations; the conventional R index on F is 0.062 for 2748 observations having Fo2 > 3σ(Fo2).
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Organic Chemistry
- Inorganic Chemistry