Photochemistry of some cyclopentadienyl carbonyl complexes of chromium, molybdenum, tungsten, iron and ruthenium isolated in frozen gas matrices at 12K
Photochemistry of some cyclopentadienyl carbonyl complexes of chromium, molybdenum, tungsten, iron and ruthenium isolated in frozen gas matrices at 12K
Photochemical processes of a variety of cyclopentadienyl transition metal carbonyl complexes of general formula (η5-C5H5)M(CO)nR(n = 3, M = Cr, Mo, W; n = 2, M = Fe, Ru; R = alkyl), (η5-C5H5)M(CO)nX (n = 3, M = Mo, W; X = Cl, AsR2, SbR2; n = 2, M = Fe, Ru: X = Cl) and (η5-C5H5)2Fe2(CO)4have been studied for the first time at 12K using primarily infrared spectroscopy together with 13CO labelling.
Photoejection of CO from (η5-C5H5)M(CO)3R complexes (M = Cr, Mo, W; R = CH3, CF3, COCF3) results in the formation of the 16-electron species (η5-C5H5)M(CO)2R. Evidence is also found for α-H and α-F elimination in the complexes (η5-C5H5)Cr(CO)3CH3 and (η5-C5H5)Mo(CO)3CF3 respectively, and for the fluoroalkyl migration to the metal in the complex (η5-C5H5)Mo(CO)3COCF3.
Photolysis of (η5-C5H5)M(CO)3H complexes (M = Cr, Mo, W) in Ar and CH4 matrices generates the16-electron species (η5-C5H5)M(CO)2H. The reactivity of these species is apparent in their reactions with N2and C2H4 to produce (η5-C5H5)M(CO)2(N2)H and (η5-C5H5)M(CO)2(C2H4)H derivatives. In CO matrices the observation of the radicals (η5-C5H5)M(CO)3͘ and HCȮ is indicative of photo-induced metal-hydrogen bond cleavage. Irradiation of trans-(η5-C5H5) W(C0)2(C2H4)H in CH4 matrices causes trans ⇌ cis isomerisation, followed by insertion of C2H4 into the W-H bond to generate the 16-electron species (η5-C5H5)W(CO)2C2H5.
Irradiation of (η5-C5R5̍)M(CO)3 alkyl complexes (M = Mo, W; R' = H, CH3) results in the formation of the 16-electron intermediates (η5-C5R5̍)M(CO)2alkyl. For alkyl complexes with β-hydrogens, thermal and photochemical 6-elimination reactions led to the conversion of (η5-C5R5̍)M(CO)2 alkyl species into the olefin-hydrides (η5-C5R5̍)M(CO)2(olefin)H. Photolysis of the (η5-C5H5)W(CO)3(η1-R) complexes (R = C3H5, CH2C6H5), led to CO dissociation and η1 ⇌ η3 isomerisation.
Direct evidence for CO dissociation as a primary photoprocess for (η5-C5H5)M(CO)2R complexes (M = Fe, Ru; R = CH3, C5H5) was afforded by trapping the 16-electron species (η5-C5H5)Ru(CO)CH3 in a CH4 matrix. Photolysis of (η5-C5H5)M(CO)2C2H5 complexes in CH4 matrices afforded (η5-C5H5)Fe(CO)2H and (η5-C5H5)Ru(CO)2H together with(η5-C5H5)Ru(CO)(C2H4)H, i.e. β-elimination. In CO matrices ring-slippage products, (η3-C5H5)M(CO)3R, were formed.
University of Southampton
Mahmoud, Khalil Assaad
e55ead23-3657-4f3a-93e5-62795ed006ed
1983
Mahmoud, Khalil Assaad
e55ead23-3657-4f3a-93e5-62795ed006ed
Rest, Anthony
3213247f-133a-424b-ad3a-6678d64be000
Mahmoud, Khalil Assaad
(1983)
Photochemistry of some cyclopentadienyl carbonyl complexes of chromium, molybdenum, tungsten, iron and ruthenium isolated in frozen gas matrices at 12K.
University of Southampton, Doctoral Thesis, 264pp.
Record type:
Thesis
(Doctoral)
Abstract
Photochemical processes of a variety of cyclopentadienyl transition metal carbonyl complexes of general formula (η5-C5H5)M(CO)nR(n = 3, M = Cr, Mo, W; n = 2, M = Fe, Ru; R = alkyl), (η5-C5H5)M(CO)nX (n = 3, M = Mo, W; X = Cl, AsR2, SbR2; n = 2, M = Fe, Ru: X = Cl) and (η5-C5H5)2Fe2(CO)4have been studied for the first time at 12K using primarily infrared spectroscopy together with 13CO labelling.
Photoejection of CO from (η5-C5H5)M(CO)3R complexes (M = Cr, Mo, W; R = CH3, CF3, COCF3) results in the formation of the 16-electron species (η5-C5H5)M(CO)2R. Evidence is also found for α-H and α-F elimination in the complexes (η5-C5H5)Cr(CO)3CH3 and (η5-C5H5)Mo(CO)3CF3 respectively, and for the fluoroalkyl migration to the metal in the complex (η5-C5H5)Mo(CO)3COCF3.
Photolysis of (η5-C5H5)M(CO)3H complexes (M = Cr, Mo, W) in Ar and CH4 matrices generates the16-electron species (η5-C5H5)M(CO)2H. The reactivity of these species is apparent in their reactions with N2and C2H4 to produce (η5-C5H5)M(CO)2(N2)H and (η5-C5H5)M(CO)2(C2H4)H derivatives. In CO matrices the observation of the radicals (η5-C5H5)M(CO)3͘ and HCȮ is indicative of photo-induced metal-hydrogen bond cleavage. Irradiation of trans-(η5-C5H5) W(C0)2(C2H4)H in CH4 matrices causes trans ⇌ cis isomerisation, followed by insertion of C2H4 into the W-H bond to generate the 16-electron species (η5-C5H5)W(CO)2C2H5.
Irradiation of (η5-C5R5̍)M(CO)3 alkyl complexes (M = Mo, W; R' = H, CH3) results in the formation of the 16-electron intermediates (η5-C5R5̍)M(CO)2alkyl. For alkyl complexes with β-hydrogens, thermal and photochemical 6-elimination reactions led to the conversion of (η5-C5R5̍)M(CO)2 alkyl species into the olefin-hydrides (η5-C5R5̍)M(CO)2(olefin)H. Photolysis of the (η5-C5H5)W(CO)3(η1-R) complexes (R = C3H5, CH2C6H5), led to CO dissociation and η1 ⇌ η3 isomerisation.
Direct evidence for CO dissociation as a primary photoprocess for (η5-C5H5)M(CO)2R complexes (M = Fe, Ru; R = CH3, C5H5) was afforded by trapping the 16-electron species (η5-C5H5)Ru(CO)CH3 in a CH4 matrix. Photolysis of (η5-C5H5)M(CO)2C2H5 complexes in CH4 matrices afforded (η5-C5H5)Fe(CO)2H and (η5-C5H5)Ru(CO)2H together with(η5-C5H5)Ru(CO)(C2H4)H, i.e. β-elimination. In CO matrices ring-slippage products, (η3-C5H5)M(CO)3R, were formed.
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Mahmoud 1983 Thesis
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Published date: 1983
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Local EPrints ID: 460213
URI: http://eprints.soton.ac.uk/id/eprint/460213
PURE UUID: 83075de9-0a75-4c85-a752-b0a93b992e74
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Date deposited: 04 Jul 2022 18:12
Last modified: 16 Mar 2024 18:36
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Author:
Khalil Assaad Mahmoud
Thesis advisor:
Anthony Rest
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