82621-44-1Relevant articles and documents
1,2-eq,eq-[Re2(CO)8(THF)2]: A reactive Re2(CO)8 fragment that easily activates H-H and C-H bonds
Carlucci, Lucia,Proserpio, Davide M.,D'Alfonso, Giuseppe
, p. 2091 - 2098 (1999)
The reaction of [Re2(μ-H)2(CO)8] (1) with diazomethane at 193 K in THF-d8 gives the unstable [Re2(μ-H)(μ-CH3)(CO)8] derivative (2) containing a methyl group arising from the insertion of CH2 into a Re-H-Re bond. Isotopic perturbation of the equilibria by partial deuteration demonstrated that the methyl bridges the Re-Re bond in an unsymmetrical way, with a fast exchange between one agostic and two terminal C-H bonds. At temperatures higher than 253 K, 2 decomposes, in THF solution, with CH4 elimination to give the novel red complex 1,2-eq,eq-[Re2(CO)8(THF)2] (3), which was characterized by NMR spectroscopy and X-ray analysis. In the solid form a staggered conformer of C2 symmetry was found. 13C NMR analysis revealed the presence, in wet THF, of the aquo complexes [Re2(CO)8(THF)-(H2O)] (4) and [Re2(CO)8(H2O)2] (5), whose formation is favored at low temperature (ΔH° for the formation of 5 from 4: -14.4(2) kJ mol-1). In solution, due to the lability of the THF ligands, 3 behaves as a lightly stabilized Re2(CO)8 fragment, capable of activating different E-H bonds. Reaction with HCl in THF leads to [Re2(μ-H)(μ-Cl)(CO)8], while with H2 the unsaturated starting material [Re2(μ-H)2(CO)8] is obtained. In THF solution, at room temperature, reactions with phenylacetylene, styrene, and acetaldehyde give the derivatives of C-H activation [Re2(μ-H)(μ-C≡CPh)(CO)8], [Re2(μ-H)(μ-CH=C(H)Ph)(CO)8], and [Re2(μ-H)(μ-η2-C(Me)O)(CO)8]. Moreover, the activation of an sp3 C-H bond in ethyl acetate occurs slowly when 3 is dissolved in the reactant itself, the resultant product being [Re2(μ-H)(μ-η2-CH2C(O)OEt)(CO) 8].
Reactions of Re2(CO)8 (L-L=dppm, dmpm) and Re2(CO)7(NCMe) with Alkynes
Lee, Kang-Wook,Pennington, William T.,Cordes, A. Wallace,Brown, Theodore L.
, p. 631 - 641 (2007/10/02)
The photochemical reaction of Re2(CO)8 (L-L=dppm, dmpm) with terminal alkynes, RCCH (R=H, Ph), results in formation of (μ-H)Re2(CO)7(η1-CCRe2) (I), (μ-H)Re2(CO)6(μ-η1,η2-CCR) (II), Re2(CO)5(L-L)(μ-η1,η2-C(R)=CH2(μ-η1,η2-CCR) (III), and Re2(CO)6(μ-η1,η2-C(R)=CH2)(μ-η1,η2-CCR) (IV).The yield for each product depends on the reaction time and the bridging ligand.I is the first isolated example of bridging hydrido, ?-bonded alkynyl di- or polynuclear compounds directly formed from alkyne.In the reaction of II with acetylenes, coordination of dppm has been rearranged to form a chelate in III.The kinetic studies for the photochemical reactions of Re2(CO)8 and the isolated compounds I and II (L-L=dppm; R=Ph) with phenylacetylene indicate that the consecutive reactions occur with loss of one carbonyl ligand in each step: Re2(CO)8(μ-dppm)->I->II->III.The reaction of Re2(CO)8 with Me3NO in acetonitrile yields the acetonitrile-substituted complex Re2(CO)7(NCMe) (VI) wherein the acetonitrile ligand is located trans to phosphorus.The thermal reaction of VI with phenylacetylene at low temperature (40 deg C) yields I, in which the ?-bonded alkynyl ligand is cis to phosphorus.In the case of the reaction of Re2(CO)7(μ-dppm)(NCMe) with phenylacetylene, the isomer of I wherein ?-bonded alkynyl ligand is located trans to phosphorus is isolated as a minor product.I is transformed to II in a high-temperature thermal reaction reaction (110 deg C).The bridging alkynyl ligand of II undergoes a rapid fluxional process.The ΔGc value estimated from the coalescence temperature temperature in the 13C NMR spectra is 10.5 kcal/mol.The structures of (μ-H)Re2(CO)7(μ-dmpm)(η1-CCPh) (Id) and Re2(CO)5(dppm)(μ-η1,η2-CH=CH2)(μ-η1,η2-CCPh) (IIIc) were determined by conventional crystallographic techniques with Mo Kα X-rays.The crystals of Id belong to the monoclinic space group P21/c with a=12.594(1) Angstroem, b=11.075(1) Angstroem, c=18.461(3) Angstroem, β=105.88(1) deg, V=2476.8(9) Angstroem3, and z=4.The crystals of IIIc belong to the orthorhombic space group Pbca with a=12.743(2) Angstroem, b=15.974(2) Angstroem, c=35.174(4) Angstroem, V=7160(2) Angstroem3, and Z=8.
