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New hexafluoroacetylacetonate (hfacac) and trifluoroacetato olefin complexes of copper(I) of the general formulas Cu(hfacac)(olefin) and Cu(CF3COO)(olefin) have been prepared from Cu2O/hfacacH/olefin or Cu(CF3COO)(toluene)0.5/olefin systems. The structures of [Cu(hfacac)(coe)], [Cu(hfacac)(van)], [Cu(μ-CF3COO)(tbve)]n, and [Cu(μ-CF3COO)(van)]2·C7H8 have been determined by X-ray diffraction methods, where coe = cyclooctene, van = 4-vinylanisole, and tbve = tert-butyl vinyl ether. In the solid state, the 4-vinylanisole/trifluoroacetate complex [Cu(CF3COO)(van)]2 is dimeric with two carboxylato groups symmetrically bridging two copper atoms, while the tert-butyl vinyl ether derivative [Cu(μ-CF3COO)(tbve)]n is polymeric with single [CF3COO]^- bridges between adjacent copper atoms. Olefin hfacac complexes are monomeric, and considering the two oxygen atoms and the midpoint of the double bond of the coordinated olefin, the copper atom lies in a nearly trigonal-planar environment. The carbonylation reactions of Cu(CF3COO)(olefin), (olefin = tbve, van; 2Cu(CF3COO)(olefin) + 2CO &lrarr2; [Cu(CF3COO)(CO)]2 + 2(olefin)) and of Cu(hfacac)(olefin) (olefin = coe, 1,5-cyclooctadiene (cod), norbornene (nbe), van; Cu(hfacac)(olefin) + CO &lrarr2; Cu(hfacac)(CO) + olefin) have been studied gas volumetrically, and the equilibrium constants for the displacement of the coordinated olefin by carbon monoxide have been determined at different temperatures. Some hypotheses on the copper−olefin bond have been formulated on the basis of structural, thermodynamic and spectroscopic (¹³C NMR) data.

Compounds of the general formula Cu(CF3COO)(olefin) (olefin = cyclooctene (coe), 1,5-cyclooctadiene (cod), diethylfumarate (defu), methylcinnamate (meci)) have been prepared, and the molecular structures have been solved by X-ray diffraction for olefin = coe, defu, meci. The complexes feature a dimeric [Cu2(μ-CF3COO)2(olefin)2] core with bridging trifluoroacetates and a η²-bonded olefin. In the case of the defu and meci complexes, [Cu2(μ-CF3COO)2(olefin)2] dimeric units are linked by the oxygen atom of a carbonyl group of the ester to give polymeric chains. The compound [Cu2(μ-CF3COO)2(meci)2]n is the first structurally characterized example of a metal-bonded methylcinnamate. By recrystallization of [Cu2(CF3COO)2(cod)2], a derivative featuring a cod/Cu molar ratio of 0.5 has been isolated and structurally characterized as [Cu2(μ-CF3COO)2(μ-cod)]n, which represents the first example of a polymeric metal complex containing a bridging cod ligand. The carbonylation reaction of [Cu(CF3COO)(olefin)]2 (olefin = coe, cod, defu; 2Cu(CF3COO)(olefin) + 2CO &rlarr2; [Cu(CF3COO)(CO)]2 + 2(olefin)) has been studied gas volumetrically, and the equilibrium constants are 12.6 ± 2.4 M^-1 (298.3 K, cod), (6.3 ± 3.2) × 10² M^-1 (293.2 K, coe), and (1.1 ± 0.7) × 10⁷ M^-1 (293.2 K, defu). The enthalpy changes, obtained from variable-temperature experiments, are −46 ± 4 (olefin = cod), −71 ± 17 (coe), and −112 ± 20 kJ mol^-1 (defu). These data for copper(I) are compared with those obtained for the 3d³ V(II) and 5d¹⁰ Au(I) systems VCp2(CO) and AuCl(CO).

The substitution reactions of VCp2(CO) with some selected olefins have been studied. Tetracyanoethylene (tcne) and fumaronitrile (fn), containing electron-withdrawing substituents, promptly react with VCp2(CO) with quantitative formation of VCp2(tcne) and VCp2(fn), respectively, while acrylonitrile and diethyl fumarate (defu) gave partial displacement of coordinated carbon monoxide under a CO atmosphere. No CO displacement from VCp2(CO) was observed with cyclooctene and norbornene. The carbonylation of VCp2(defu) (VCp2(defu) + CO &rlarr2; VCp2(CO) + defu) has been studied gas volumetrically from both sides, and the equilibrium constant for the displacement of coordinated defu by carbon monoxide was estimated to be 55 ± 8 at 298.5 K. Variable-temperature experiments between 298.5 and 327.7 K have shown the enthalpy change to be −2.4 kcal mol^-1. The equilibrium constant for the addition of defu to VCp2 (VCp2 + defu &rlarr2; Cp2(defu)) has been evaluated spectroscopically to be 150 ± 11 at 298.5 K. From the available data, the equilibrium constant for the addition of carbon monoxide to VCp2 (VCp2 + CO &rlarr2; VCp2(CO)) has been calculated to be Ka = (8.2 ± 0.4) × 10³:  i.e., about 2 orders of magnitude higher than that for the complexation of defu. The present data for the 3d³ system of vanadium(II) (&nutilde;CO in toluene 1881 cm^-1) are compared with those exhibited by the 5d¹⁰ system of AuCl(CO) (&nutilde;CO in toluene 2153 cm^-1), whose behavior consistently shows an opposite dependence, as far as the olefin/CO competition is concerned, on the nature of the olefin.

The one-electron oxidation of vanadocene, VCp2, by [FeCp2]⁺ in toluene affords the 14-electron [VCp2]⁺ cation, which has been isolated as an unsolvated species for the first time. Vanadium hexacarbonyl reacts with VCp2 to give the μ-isocarbonyl derivative Cp2V(μ-OC)V(CO)5 as a transient species, which has been characterized in solution by IR analysis. By reaction of VCp2 with V(¹³CO)6 followed by treatment with ¹²CO, the ionic dicarbonyl derivative [VCp2(¹²CO)2][V(¹³CO)6] is formed, thus showing that during the formation of the ionic compound no redistribution of the carbonyl ligands between the two metal centers occurs. Bis(cyclopentadienyl)vanadium(II) and Co2(CO)8 give Cp2VCo(CO)4, which slowly decomposes in solution even at low temperature to give [VCp2(CO)2][Co(CO)4], which was identified by conventional methods, including single-crystal X-ray diffraction. The reactivity of the unsolvated [VCp2]⁺ cation as well as that of the heterobimetallic compound containing vanadium and cobalt with several Lewis bases is reported.