12125-72-3Relevant articles and documents
Heterobimetallic indenyl complexes. Kinetics and mechanism of substitution and exchange reactions of trans-[Cr(CO)3-indenyl-Rh(CO)2] with olefins
Bonifaci, Chiara,Carta, Giovanni,Ceccon, Alberto,Gambaro, Alessandro,Santi, Saverio,Venzo, Alfonso
, p. 1630 - 1636 (1996)
The trans coordination of the benzene ring of the indenyl-Rh(CO)2 complex with tricarbonylchromium strongly enhances the rate of substitution of CO's with bidentate olefins, 1,5-cyclooctadiene (COD) and norbornadiene (NBD) ( extra-indenyl effect ). The activation parameters suggest an associative reaction pathway assumed to proceed via the intermediacy of a nonisolable low-hapticity species, η1-indenyl-Rh(CO)2(L2). In addition, the rate of exchange of the Cr(CO)3 group of the complexes trans-[Cr(CO)3-indenyl-Rh(CO)2], 3, and trans-[Cr(CO)3-indenyl-Rh(COD)], 3a, and suitable acceptors (hexamethylbenzene and cycloheptatriene) is markedly increased with respect to that measured for the same reaction in the monometallic complex η-naphthalene-Cr(CO)3 ( extra-naphthalene effect ). These mutual effects of the Cr(CO)3 and RhL2 units are transmitted through the 10 π electron indenyl framework, and the results obtained are in agreement with the existence of an haptomeric ground-state equilibrium between the two isomers trans-[Cr(CO)3μ,η6:η 3-indenyl-RhL2], I, and trans-[Cr(CO)3-μ,η4:η 5-indenyl-RhL2], II.
Ground-state versus transition-state effects in arene displacement reactions of the complexes (η6-arene)Cr(CO)s: Linear dependence of transition-state energies and resonance energies of the arene ligands
Zhang, Songshen,Shen, Jian Kun,Basolo, Fred,Ju, Telvin D.,Lang, Russell F.,Kiss, Gabor,Hoff, Carl D.
, p. 3692 - 3702 (2008/10/08)
The rates of displacement of arene and thiophene ligands by P(n-Bu)3 in decalin and PPh3 in toluene have been studied. The reactions are first order in complex and incoming ligand. Rates of reaction increase in the order benzene dimethylthiophene > triphenylene > phenanthrene > thiophene > naphthalene > anthracene > pyrene and spans about 7 kcal/mol. The combination of kinetic and thermodynamic data is used to construct reaction profiles for these reactions. On the basis of the assumption that the transition state occurs on the way to formation of (η4-arene)Cr(CO)3(L) a linear correlation exists between the enthalpy of formation of the transition-state complex and changes in resonance energy of the fused arene ligands attributable to localization of the π bonds of the proposed η4 intermediate. The rate of binding of C6H6 to (THF)3Cr(CO)3 is 10% slower than for C6D6, implicating the importance of (η1-C6H6)Cr(CO)3(THF) 2 as an intermediate on the pathway to formation of (η6-C6H6)-Cr(CO)3.
Substitution and addition reactions of the (CO)3(η7-tropylium)M cations (M = Cr, Mo, W) with tertiary diphosphines
Brown, David A.,Burns, John,Glass, William K.,Cunningham, Desmond,Higgins, Tim,McArdle, Patrick,Salama, Mabrouk M.
, p. 2662 - 2667 (2008/10/08)
The reactions of the title compounds I-III, [(η7-C7H7)M(CO)3]BF4 (M = Cr, Mo, and W, respectively), with the diphosphines PPh2(CH2)nPPh2 (n = 1-4) at low temperatures (-40 to -60°C) form two new series of complexes which are quite different from previous carbonyl substitution products. The first series (IV-VI) formed by the diphosphines (n = 1-3) comprise 7-exo ring adducts involving the bonding of only one phosphorus atom of the diphosphine to ring carbon atom 7 of I. The second series (VII and VIII) are diphosphine ring linked dimers, e.g. [(7,7′-exo-dppb){η6-C7H7)Cr(CO) 3}2] [BF4]2, for which X-ray crystallography confirms a diphosphine linked ring-ring structure with the Cr(CO)3 moieties situated on opposite sides of the ring systems. The ring C-phosphorus bond length of 1.852 A? indicates a relatively weak bond, consistent with facile cleavage of these adducts on reaction with nucleophiles such as hydride.
The arene-exchange reaction in naphthalene- and pyrene-Cr(CO)3
Howell, James A. S.,Ashford, Neil F.,Dixon, Denis T.,Kola, John C.,Albright, Thomas A.,Kang, Sung Kwon
, p. 1852 - 1864 (2008/10/08)
The arene-exchange reaction has been studied for a number of labile (arene)Cr(CO)3 substrates in hydrocarbon solvents. A two-term rate law was established of the form -d[S]/dt = kA[S] + kB[S][arene′], where S is the (arene)Cr(CO)3 substrate and toluene was used as the external, arene', ligand. The lability of S follows the ordering (2,6-dimethylpyridine)- > (pyrene)- > (naphthalene)- > (2,5-dimethyl-thiophene)Cr(CO)3. Activation parameters for (naphthalene)Cr(CO)3 were ΔH?A = 28 (1) kcal mol-1, ΔS?A = -14 (2) cal K-1 mol-1, ΔH?B = 26 (1) kcal mol-1, and ΔS?B = -23 (3) cal K-1 mol-1. For (pyrene)Cr(CO)3 they were determined to be ΔH?A = 25 (1) kcal mol-1, ΔS?A = -19 (3) cal K-1 mol-1, ΔH?B = 24 (1)kcal mol-1, and ΔS?B = -22 (2) cal K-1 mol-1. The substitutional affinity of (pyrene)Cr(CO)3 for arene' was found to be C6H5CF3 6H5Me 6H4Me2 ≈ C6H5But 6M6 y-arene)Cr(CO)3 intermediate and the other path through an (ηx-arene)Cr(CO)3(η6-x-arene') intermediate with y 3 derivatives. An η6 → η2 path was found to be most favorable for the naphthalene system, whereas an η6 → η1 path required the least energy for pyrene. In (benzene)Cr(CO)3 both paths were found to be comparable in energy. The calculations correctly predict arene lability to be in the order benzene ? naphthalene a discrete η4 intermediate was found for the arene'-independent route.
THE HEATS OF IODINATION OF CHROMIUM TRICARBONYL COMPLEXES OF ARENES AND CYCLOHEPTATRIENE
Hoff, Carl D.
, p. C53 - C56 (2007/10/02)
The heats of iodination of chromium tricarbonyl complexes of benzene, toluene, mesitylene, and cycloheptatriene have been measured by solution calorimetry in tetrahydrofuran at 25 deg C.The order of the Cr-ligand strength is: mesitylene > cycloheptatriene
