The migratory insertion of carbon monoxide in pentamethylcyclopentadienyliridium(III) complexes. Structural effects on reactivity and mechanism for rhodium and iridium systems

被引:11
作者
Monti, D
Frachey, G
Bassetti, M
Haynes, A
Sunley, GJ
Maitlis, PM
Cantoni, A
Bocelli, G
机构
[1] UNIV ROMA LA SAPIENZA, DIPARTIMENTO CHIM, CNR, CTR STUDIO MECCANISMI REAZ, I-00185 ROME, ITALY
[2] UNIV SHEFFIELD, DEPT CHEM, SHEFFIELD S3 7HF, S YORKSHIRE, ENGLAND
[3] CNR, CTR STUDIO STRUTTURIST DIFFRATTOMETR, I-43100 PARMA, ITALY
关键词
crystal structures; migratory insertion; iridium complexes; pentamethylcyclopentadienyl complexes; carbon monoxide complexes; alkyl complexes;
D O I
10.1016/0020-1693(95)04573-2
中图分类号
O61 [无机化学];
学科分类号
070301 ; 081704 ;
摘要
The reactions of complex (C(5)Me(5))Ir(Cl)(CO)(Me) (1a) with cyclohexylisocyanide and phosphines (L = CyNC, PHPh(2), PMePh(2), PMe(2)Ph) give the products of alkyl migratory insertion (C(5)Me(5))Ir(Cl)(COMe)(L), in toluene or tetrahydrofuran at 323 K or higher temperature. The phenyl analogue (C(5)Me(5))Ir(Cl)(CO)(Ph) or the iodide complexes (C(5)Me(5))Ir(I)(CO)(R)(R = Me, Ph) are not reactive under the same conditions. The reaction of (C(5)Me(5))Ir(Cl)(CO)(Me) with PMePh(2) and PMe(2)Ph in acetonitrile yields the chloride substitution product [(C(5)Me(5))Ir(CO)(L)(Me)]Cl-+(-). Kinetic measurements for the reactions of (C(5)Me(5))Ir(Cl)(CO)(Me) in toluene are first order in the iridium complex and exhibit a saturation dependence on the incoming donors L. Analysis of the data suggests a two-step process involving (i) rapid formation of a molecular complex [(C(5)Me(5))Ir(Cl)(CO)(Me),(L)], in which the structure of 1a is unperturbed within the limits of spectroscopic analysis, and (ii) rate determining methyl migration. The reaction parameters are K for the pre-equilibrium step (K = 1.5 (CyNC), 7.3 (PHPh(2)), 7.1 (PMePh(2)) dm(3) mol(-1) at 323 K) and k(2) for the slow carbon-carbon bond formation (k(2)(10(5)) = 6.9 (CyNC), 1.2 (PHPh(2)), 1.0 (PMePh(2)) s(-1) at 323 K). The activation parameters for the methyl migration step in the reaction with PMePh(2), obtained between 308 and 338 K, are Delta H not equal = 106 +/- 16 kJ mol(-1) and Delta S not equal = -14 +/- 5 JK(-1) mol(-1). The reaction of 1a with PMePh(2) proceeds at similar rates in tetrahydrofuran (K = 3.7 dm(3) mol(-1), k(2)(10(5)) = 1.2 s(-1), 323 K). The crystal structure of (C(5)Me(5))Ir(Cl)(COMe)(PMe(2)Ph) has been determined by X-ray diffraction. C20H29ClOPIr: M(r) = 544.1, monoclinic, P2(1)/n, a = 8.084(2), b = 9.030(2), c = 28.715(3) Angstrom, beta = 91.41(3)degrees, Z = 4, D-c = 1.71 g cm(-3), V = 2095.5 Angstrom(3), room temperature, Mo K alpha, lambda = 0.71069, mu = 65.55 cm(-1), F(000) = 1044, R = 0.037 for 2453 independent observed reflections. The complex shows a deformed tetrahedral coordination assuming the eta(5)-C(5)Me(5) molecular fragment as a single coordination site. The iridium-chlorine bond is staggered with respect to two adjacent C(ring)-methyl bonds, while the Ir-P and the Ir-COMe bonds are eclipsed with respect to C(ring)-methyl bonds.
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页码:485 / 493
页数:9
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