VANADIUM-OLEFIN AND VANADIUM-ACETYLENE COMPLEXES - STRUCTURAL STUDIES ON (ETA-2-DIETHYL FUMARATO-C,C) AND (ETA-2-DIMETHYL ACETYLENEDICARBOXYLATO-C,C)BIS(ETA-CYCLOPENTADIENYL)VANADIUM

Vanadocene, (cp)2v (cp = η5-C5H5), adds as a carbene-like species to the C̿C bond of diethyl fumarate or diethyl maleate, producing the same monomeric olefinic complex (IV) in which the coordinated olefin assumes the trans configuration. Diethyl maleate isomerizes upon coordination to the metal. Vanadium is η5bonded to the two Cp rings, which are in a bent arrangement making a cavity in the equatorial plane for the y2-C, C bonded olefinic ligand [cp(l)-V-cp(2) = 135.9°]. The C̿C bond distance is significantly lengthened by interaction with the metal to the value [1.468 (11) Å] expected for a single bond. Vanadocene reacts with CH302C—C̿C—C02CH3giving complex V with an overall geometry very similar to that found for the olefinic complex. The coordinated C-C bond length [1.287 (4) Å] is nearly close to that of a double bond. Both complexes have rigorous C2symmetry. They represent rare examples of vanadocene with an additional V-C bond for which structural data are available [V-C = 2.186 (12) and 2.213 (12) A for (cp)2V(C2H502CCH-CHC02C2Hs) and 2.097 (3) and 2.084 (3) A for (cp)2V(CH302CC=CC02CH3)]. Crystallographic details for (cp)2V(C2H502C-CH-CH-C02C2H5): space group P2,/c (monoclinic); a = 7.871 (1), b = 18.604 (3), c = 13.712 (3) Å β = 121.32 (2)°; U = 1715.3 A3; Z = 4; Dc= 1.368 g cm-3. The final R factor was 6.5% for 2321 observed reflections. Crystallographic details for (cp)2V(CH302C—C̿C—C02CH3): space group C2/c (monoclinic); a = 25.089 (2), b = 7.948 (1), c = 15.979 (2) Å γ = 112.14 (1)° U = 2951.4 A3; Z = 8; Dc= 1.455 g cm-3. The final R factor was 4.4% for 2408 observed reflections. © 1979, American Chemical Society. All rights reserved.