Reactions of tBuCP with Cyclooctatetraene-Supported Titanium Imido Complexes

Cloke, F Geoffrey N, Green, Jennifer C, Hazari, Nilay, Hitchcock, Peter B, Mountford, Philip, Nixon, John F and Wilson, D James (2006) Reactions of tBuCP with Cyclooctatetraene-Supported Titanium Imido Complexes. Organometallics, 25 (15). pp. 3688-3700. ISSN 02767333

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Reaction of the pseudo two-coordinate titanium imido complexes [Ti(N tBu)(COT)] (1; COT = ¿8-C8H8) and [Ti(NtBu)(COT¿)] (2; COT¿ = ¿ 8-1,4-C8H6(SiMe3)2) with 2 equiv of tBuC=P generated the new complexes [Ti{N( tBu)PC(tBu)PC(tBu)}(COT)] (4) and [Ti{N( tBu)PC(tBu)PC(tBu)}(COT¿)] (5), respectively. Complex 4 was crystallographically characterized, and a density functional theory (DFT) study combined with photoelectron (PE) spectroscopy revealed this apparently 20-valence-electron species to contain a HOMO which is almost entirely ligand-based. In contrast, the organic compound N(Ar)-P 2C2tBu2 (6), which incorporates a 1,2,4-azadiphosphole ring, was the only isolated product from the reaction of the arylimido species [Ti(NAr)(COT)] (3; Ar = 2,6-iPr 2C6H3) with an excess of tBuC=P. DFT studies indicated that the mechanisms for the formation of compounds 4-6 are similar. Initially, one molecule of tBuC=P undergoes a [2 + 2] cycloaddition with [Ti(NR)(COT)] to form [Ti{N(R)PC-(tBu)}(COT)], which contains a Ti-C bond. Subsequently, a second molecule of tBuC=P reacts with [Ti{N(R)PC(tBu)}(COT)] to form [Ti{N(R)PC(tBu)PC( tBu)}(COT)]. When R = 2,6-iPr2C 6H3 or a substituent which is less sterically bulky, the formation of a heterocyclic ring such as N(Ar)P2C2tBu2 (6) is favored. However, when R = tBu, it is sterically unfavorable to form such a ring and thus compound 4 is stable.

Item Type: Article
Schools and Departments: School of Life Sciences > Chemistry
Depositing User: Geoff Cloke
Date Deposited: 06 Feb 2012 19:56
Last Modified: 26 Mar 2012 10:01
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