Matrix photochemistry of (eta/sup 5/-cyclopentadienyl)bis)ethene)rhodium and (eta/sup 5/-cyclopentadienyl)(ethene)carbonylrhodium: a test-bed for intermediates in C-H activation

Journal Article · Wed Mar 16 04:00:00 EST 1988 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00214a025· OSTI ID:7004401

Haddleton, D M; McCamley, A; Perutz, R N

The photochemical reactivities of CpRh(C/sub 2/H/sub 4/)/sub 2/ (1) and CpRh(C/sub 2/H/sub 4/)CO (Cp = eta/sup 5/=C/sub 5/H/sub 5/) have been examined in low-temperature matrices with IR and UV/vis detection. Photodissociation of ethene from 1 in inert matrices (Ar or CH/sub 4/) yields the coordinatively unsaturated (CpRhb(C/sub 24/; the reaction is reversed by long-wavelength irradiation. The identity of CpRh(C/sub 2/H/sub 4/) is demonstrated with /sup 2/H labeling of ethene and cyclopentadienyl groups. The IR results support a bent, ground-state geometry for CpRh(C/sub 2/H/sub 4/). UV photolysis of 1 in CO matrices releases ethene and generates 2 and CPRh(CO)/sub 2/ sequentially. The corresponding reaction in nitrogen matrices leads to CpRh(C/sub 2/H/sub 4/)(N/sub 2/). On photolysis of 1 in CO-doped methane matrices, CpRh(CO)(CH/sub 3/)H is formed in addition to substitution products. Complex 2 undergoes loss of either CO, yielding CpRh(C/sub 2/H/sub 4/), or of C/sub 2/H/sub 4/, yielding CPRHCO, on UV photolysis in argon matrices. These reactions are reversed by long-wavelength photolysis, but in more concentrated matrices Cp/sub 2/Rh/sub 2/(CO)/sub 2/ is formed as an additional product. In nitrogen matrices both CpRh(C/sub 2/H/sub 4/)(N/sub 2/) and CpRh(CO)(N/sub 2/) are generated. In methane matrices CpRH(C/sub 2/H/sub 4/) is still detected on UV photolysis, but CpRhCO is replaced by the product of oxidative addition of methane, CpRh(CO)(CH/sub 3/)H. Long-wavelength photolysis removes CpRh(C/sub 2/H/sub 4/) but increases conversion to the (methyl)hydride complex. These experiments demonstrate that oxidative addition of methane must proceed via CpRhCO. The role of CpRhL (L = C/sub 2/H/sub 4/, CO) intermediates in solution reactions is discussed.

• Research Organization: Univ. of York (England)
• OSTI ID: 7004401
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 110:6; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400500* -- Photochemistry
ABSORPTION SPECTROSCOPY
ALKENES
CARBONYLS
CHEMICAL REACTIONS
CHEMISTRY
CYCLOALKENES
DATA
DECOMPOSITION
DIENES
EXPERIMENTAL DATA
HYDROCARBONS
INFORMATION
INFRARED SPECTRA
NUMERICAL DATA
ORGANIC COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOCHEMISTRY
PHOTOLYSIS
POLYENES
REACTION INTERMEDIATES
SPECTRA
SPECTROSCOPY
ULTRAVIOLET SPECTRA
VISIBLE SPECTRA