Kinetics and mechanism of the formation of the bis(ethylidyne) tricobalt cluster Cp{sup *}{sub 3}Co{sub 3}({mu}{sub 3}-CCH{sub 3}){sub 2} from reaction of acetylene with Cp{sup *}{sub 3}Co{sub 3}({mu}{sub 2}-H){sub 3}({mu}{sub 3}-H)
- Univ. of Wisconsin, Madison, WI (United States)
The paramagnetic tetrahydride cluster Cp{sup *}{sub 3}Co{sub 3}({mu}{sub 2}-H){sub 3}({mu}{sub 3}-H) (1) reacts with acetylene to ultimately form the bis(ethylidyne) cluster Cp{sup *}{sub 3}Co{sub 3}({mu}{sub 3}-CCH{sub 3}){sub 2} (2). Two kinetically formed intermediates were isolated from the reaction: the diamagnetic mono(ethylidyne) trihydride cluster Cp{sup *}{sub 3}Co{sub 3}({mu}{sub 2}-H){sub 3}({mu}{sub 3}-CCH{sub 3}) (3) and the paramagnetic mono(ethylidyne) monohydride cluster Cp{sup *}{sub 3}Co{sub 3}({mu}{sub 3}-H)({mu}{sub 3}-CCH{sub 3}) (4). Cluster 3 loses H{sub 2} at 80{degree}C [{Delta}G{sup {double_dagger}} = 29.5(1) kcal mol{sup -1}] to generate 4, and 4 reacts with H{sub 2} at 80{degree}C [{Delta}G{sup {double_dagger}} = 23.8(1) kcal mol{sup -1}] to regenerate 3. A third intermediate in the reaction of 1 with acetylene, the bridging acetylene dihydride cluster Cp{sup *}{sub 3}Co{sub 3}({mu}-H){sub 2}({mu}{sub 3}-{eta}{sup 2}-HCCH) (5), was detected by {sup 1}H NMR spectroscopy at 23{degree}C and rearranges to form exclusively cluster 4. Cluster 1 reacts with DC{equivalent_to}CD at 80{degree}C to form Cp{sup *}{sub 3}Co{sub 3}({mu}{sub 2}-H){sub 2}({mu}{sub 2}-D)({mu}{sub 3}-CCH{sub 2}D) (3-CH{sub 2}D) as the exclusive diamagnetic product. The formation of 3-CH{sub 2}D is consistent with the presence of the ethylidene dihydride intermediate Cp{sup *}{sub 3}-Co{sub 3}({mu}{sub 2}-H){sub 2}({mu}{sub 2}-CDCH{sub 2}D) (III). 85 refs., 6 figs., 1 tab.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 45027
- Journal Information:
- Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Journal Issue: 16 Vol. 117; ISSN JACSAT; ISSN 0002-7863
- Country of Publication:
- United States
- Language:
- English
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