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.

Munro, J. D.,Pauson, P. L.

, (1961)

7?-acetoxy-(1H?, 6H?)-bicyclo[4.4.1]undeca-2,4,8-triene via chromium-mediated higher order cycloaddition: [ bicyclo[4.4.1]undeca-3,7,9-triene-2-ol, acetate, endo- (±)- ]

Rigby, James H.,Fales, Kevin R.,Lee Trout, Robert E.,Smith, Amos B.

, p. 121 - 121 (2017/09/28)

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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.