Synthesis, structure, and reactivity of O-donor Ir(III) complexes: C-H activation studies with benzene

被引:66
作者
Bhalla, G
Liu, XY
Oxgaard, J
Goddard, WA
Periana, RA [1 ]
机构
[1] Univ So Calif, Donald P & Katherine B Loker Hydrocarbon Res Inst, Los Angeles, CA 90089 USA
[2] Univ So Calif, Dept Chem, Los Angeles, CA 90089 USA
[3] CALTECH, Beckman Inst, Mat & Proc Simulat Ctr, Div Chem & Chem Engn, Pasadena, CA 91125 USA
关键词
D O I
10.1021/ja051532o
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
Various new thermally air- and water-stable alkyl and aryl analogues of (acac-O,O)(2)Ir(R)(L), R-Ir-L (acac-O,O = kappa(2)-O,O-acetylacetonate, -Ir- is the trans-(acac-O,O)(2)Ir(III) motif, R = CH3, C2H5, Ph, PhCH2CH2, L = Py) have been synthesized using the dinuclear complex [Ir(mu-acac-O,O,C-3)-(acac-O,O)(acac-C-3)](2), [acac-C-Ir](2), or acac-C-Ir-H2O. The dinuclear Ir (III) complexes, [Ir(mu-acac-O,O,C-3)-(acac-O,O)(R)](2) (R = alkyl), show fluxional behavior with a five-coordinate, 16 electron complex by a dissociative pathway. The pyridine adducts, R-Ir-Py, undergo degenerate Py exchange via a dissociative mechanism with activation parameters for Ph-Ir-Py (Delta H double dagger = 22.8 +/- 0.5 kcal/mol; AS double dagger = 8.4 +/- 1.6 eu; Delta G double dagger(298K) = 20.3 +/- 1.0 kcal/mol) and CH3-Ir-Py (Delta H double dagger = 19.9 +/- 1.4 kcal/mol; Delta S double dagger = 4.4 +/- 5.5 eu; Delta G double dagger(298K) = 18.6 +/- 0.5 kcal/mol). The trans complex, Ph-Ir-Py, undergoes quantitatively trans-cis isomerization to generate cis-Ph-Ir-Py on heating. All the R-Ir-Py complexes undergo quantitative, intermolecular CH activation reactions with benzene to generate Ph-Ir-Py and RH. The activation parameters (Delta S double dagger = 11.5 +/- 3.0 eu; Delta H double dagger = 41.1 +/- 1.1 kcal/mol; Delta G double dagger(298k) = 37.7 +/- 1.0 kcal/mol) for CH activation were obtained using CH3-Ir-Py as starting material at a constant ratio of [Py]/[C6D6] = 0.045. Overall the CH activation reaction with R-Ir-Py has been shown to proceed via four key steps: (A) pre-equilibrium loss of pyridine that generates a trans-five-coordinate, square pyramidal intermediate; (B) unimolecular, isomerization of the trans-five-coordinate to generate a cis-five-coordinate intermediate, cis-R-Ir-square; (C) rate-determining coordination of this species to benzene to generate a discrete benzene complex, cis-R-Ir-PhH; and (D) rapid C-H cleavage. Kinetic isotope effects on the CH activation with mixtures of C6H6/C6D6 (KIE = 1) and with 1,3,5-C6H3D3 (KIE similar to 3.2 at 110 degrees C) are consistent with this reaction mechanism.
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页码:11372 / 11389
页数:18
相关论文
共 129 条
[41]   NEW FOUNDATION FOR USE OF PSEUDOPOTENTIALS IN METALS [J].
GODDARD, WA .
PHYSICAL REVIEW, 1968, 174 (03) :659-&
[42]  
Griffith WP., 1970, COORDIN CHEM REV, V5, P459, DOI DOI 10.1016/S0010-8545(00)80101-0
[43]   POLYDENTATE LIGANDS CONTAINING PHOSPHORUS .11. SYNTHESIS OF 3 NEW ANIONIC TRIPOD LIGANDS, THEIR NEUTRAL PRECURSORS, AND RELATED-COMPOUNDS [J].
GRIM, SO ;
SANGOKOYA, SA ;
COLQUHOUN, IJ ;
MCFARLANE, W ;
KHANNA, RK .
INORGANIC CHEMISTRY, 1986, 25 (16) :2699-2704
[44]  
Gunther H, 1995, NMR SPECTROSCOPY, P335
[45]  
Gutierrez-Puebla E, 1998, CHEM-EUR J, V4, P2225, DOI 10.1002/(SICI)1521-3765(19981102)4:11<2225::AID-CHEM2225>3.3.CO
[46]  
2-9
[47]   EFFECT OF D-FUNCTIONS ON MOLECULAR-ORBITAL ENERGIES FOR HYDROCARBONS [J].
HARIHARAN, PC ;
POPLE, JA .
CHEMICAL PHYSICS LETTERS, 1972, 16 (02) :217-+
[48]  
HAY PJ, 1985, J CHEM PHYS, V82, P299, DOI [10.1063/1.448800, 10.1063/1.448799]
[50]   METAL-CENTERED OXYGEN ATOM TRANSFER-REACTIONS [J].
HOLM, RH .
CHEMICAL REVIEWS, 1987, 87 (06) :1401-1449