xylene CpV(CO), + bpy -V(bpy), + unidentified products (3 1 presence of bpy leads to the formation of unidentifiable products.The structure of 2 consists of discrete cis-(~&H~)V(CO)~.bpy molecules possessing an imposed crystallographic Cm symmetry ( Figure 2). The vanadium lies on the mirror plane bisecting the C 3 4 3 ' and C16-Cl6' bonds. The coordination geometry around the metal center is square pyramidal with the two nitrogen atoms from bpy and two carbon atoms from the carbonyls on the basal plane and the centroid of $-bonded Cp ring on the apex. The vanadium lies at 0.898 (1) A from the basal plane, which is perfectly planar for symmetry requirements. Bond distances and angles in the vanadium coordination sphere are in agreement with the correspondin ones observed in complex 1, the V-N distance ring and bpy are as expected. Complex 2 does not display any special spectroscopic features. Two intense absorptions are present in the IR spectrum (v(CO),,,,,, 1843 cm-'; u(CO),,, 1780 cm-'), as expected for a cis-dicarbonyl transition-metal derivative. The Cp resonances are present as singlets in the 'H N M R (4.80 ppm) and 13C N M R (96.55 ppm) spectra, and the resonances of the coordinated bpy are as expected for an ABCD spin system. No resonances attributable to carbonyl being 2.138 (4) x . All bond distances and angles within the Cp (13) Herzog, S. Z. Anorg. Allg. Chem. 1958, 294, 155.groups have been observed in the 13C N M R spectrum.Attempts to utilize 1 for oxidative-addition reactions with a diverse range of substrates such as COz, C02-like molecules, azobenzene, diazoalkanes, and organic azides have led to the formation of CPV(CO)~ as the main product. We believe that the low affinity for CO of the mono(cyclopentadieny1vanadium-(111)) derivatives formed during the oxidative-addition reactions is responsible for such a failure. In other words, for each molecule of 1 that undergoes oxidative addition, three molecules of CO are released. Fast reaction of 1 with CO leads to the unreactive CpV(CO), in 75% yield. Efforts to isolate other species from the reaction mixtures have been unsuccessful so far.
