Synthesis of an (/eta//sup 3/-allyl(hydrido)iridium complex and its reactions with arenes and alkanes. Sequential intermolecular C-H oxidative addition and hydride-to-alkene migratory insertion reactions
The iridium allyl hydride complex (/eta//sup 5/-C/sub 5/Me/sub 5/)(/eta//sup 3/-C/sub 3/H/sub 5/)(H)Ir (2) has been prepared from ((/eta//sup 5/-C/sub 5/Me/sub 5/)IrCl/sub 2/)/sub 2/, and its reaction with arenes and alkanes has been investigated. The hydride reacts with C-H bonds in benzene and cyclopropane in the presence of phosphines L, leading to the phenyl and cyclopropyl complexes (/eta//sup 5/-C/sub 5/Me/sub 5/)(L)Ir(n-propyl)(R) (3,4, and 5). Irradiation of 2 in the presence of PMe/sub 3/ takes a different course, giving the previously uncharacterized (/eta//sup 5/-C/sub 5/Me/sub 5/)Ir(PMe/sub 3/)/sub 2/ (6). Thermal reaction of 2 in alkane solvents such as n-butane and isobutane, which are capable of ..beta..-elimination, leads to products 8a, 8b, and 9 formed by replacement of the allyl group in 2 by a substituted allyl ligand formed by overall dehydrogenation of the alkane. Thermolysis of 2 in the presence of arenes such as n-propylbenzene and cumene leads to more complicated products resulting from intermolecular C-H activation followed by cyclometalation (e.g., 13, 15) and/or dimerization (20). The structure of cyclometalated dimer 20 has been determined by X-ray diffraction. Mechanistic studies, including kinetics, isotope tracer experiments, and intra-versus intermolecular isotope effect determinations, implicate the coordinatively unsaturated species (/eta//sup 5/-C/sub 5/Me/sub 5/)(/eta//sup 2/-propene)Ir (complex A in Scheme XX) as the initially formed intermediate in the thermal reactions of 1 with alkanes and arenes. Significant differences exist between the behavior of this intermediate (cf. Schemes XIX and XXIII) and that of the closely related phosphine-substituted complex (/eta//sup 5/-C/sub 5/Me/sub 5/)(PMe/sub 3/Ir) studied earlier; possible reasons for these differences are discussed.
- Research Organization:
- Lawrence Berkeley Lab., CA (USA)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 5993226
- Journal Information:
- J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 110:13; ISSN JACSA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400201* -- Chemical & Physicochemical Properties
ALKANES
AROMATICS
CARBON
CHEMICAL BONDS
CHEMICAL PREPARATION
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
COHERENT SCATTERING
COMPLEXES
DATA
DEHYDRATION
DIFFRACTION
ELEMENTS
EXPERIMENTAL DATA
HYDRIDES
HYDROCARBONS
HYDROGEN
HYDROGEN COMPOUNDS
INFORMATION
IRIDIUM COMPLEXES
KINETICS
NONMETALS
NUMERICAL DATA
ORGANIC COMPOUNDS
OXIDATION
REACTION INTERMEDIATES
REACTION KINETICS
SCATTERING
SYNTHESIS
TRANSITION ELEMENT COMPLEXES
X-RAY DIFFRACTION