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Reactions of tBuCP with Cyclooctatetraene-Supported Titanium Imido Complexes

journal contribution
posted on 2023-06-08, 00:38 authored by Geoff Cloke, Jennifer C Green, Nilay Hazari, Peter B Hitchcock, Philip Mountford, John F Nixon, D James Wilson
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.

History

Publication status

  • Published

Journal

Organometallics

ISSN

02767333

Issue

15

Volume

25

Page range

3688-3700

Department affiliated with

  • Chemistry Publications

Full text available

  • No

Peer reviewed?

  • Yes

Legacy Posted Date

2012-02-06

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