Reactions of (η6-diphenylacetylene) chromiumtricarbonyl complexes with polynuclear carbonyls I. Synthesis of Cr(CO)3(η6-diphenylacetylene) complex and its reaction with Co2(CO)8. Crystal and molecular structure of Cr(CO)3(η6:η2-diphenylacetylene)Co2(CO)6

Article abstract of DOI:10.1016/0022-328X(94)87011-X

The reaction of Cr(CO)3(NH3)3 with diphenylacetyleneaffords as a main product the complex with Cr(CO)3 moiety bound to a phenyl ring of diphenylacetylene; Cr(CO)3(η⁶-PhC2Ph) (I).Complex I readily reacts with Co2(CO)8 yielding the mixed metal complex Cr(CO)3(η⁶:η²-PhC2Ph)Co2(CO)6 (II).The reaction proceeds with retention of the Cr(CO)3(η⁶-arene) structural unit, the Co2(CO)6 fragment being bound to the triple bond of diphenylacetylene in μ₂,η²-mode.The structure of II was determined by single crystal X-ray analysis.The complex crystallizes in spacegroup P2₁/c with unit cell parameters a 8.666(3) Angstroem, b 18.046(3) Angstroem, c 15.155(6) Angstroem, β 97.57(3) deg, V 2349(2) Angstroem³, Z = 4, D_x = 1.70 g/cm³.The structure was solved by direct methods and refined by full-matrix least-squares technique to R and R_w values of 0.032 and 0.034, respectively, for 3655 observed reflections.The data obtained show that two structural units in II, Cr(CO)3(η⁶-Ph-) and Co2(CO)6(μ₂,η²-C<*>C), are distorted due to steric repulsion between these metal carbonyl moieties.The Cr(CO)3 fragment is shifted from the centre of the phenyl ring and slightly tilted with respect to the phenyl ring plane.The Co2C2 tetrahedron in the Co2(CO)6(μ₂,η²-C<*>) moiety is distorted in such a way that two of the four Co_i-C_j bonds are elongated.Key words: Chromium; Carbonyl; Cobalt; Acetylene; Crystal structure