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Titanium Imido Complexes of Cyclooctatetraenyl Ligands
Author(s) -
Dunn Simon C.,
Hazari Nilay,
Jones Nicholas M.,
Moody Aidan G.,
Blake Alexander J.,
Cowley Andrew R.,
Green Jennifer C.,
Mountford Philip
Publication year - 2005
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200401104
Subject(s) - chemistry , crystallography , steric effects , dimer , lone pair , ligand (biochemistry) , ring (chemistry) , aryl , metal , density functional theory , transition metal , stereochemistry , computational chemistry , molecule , biochemistry , alkyl , receptor , organic chemistry , catalysis
Reaction of [Ti(NR)Cl 2 (py) 3 ] (R= t Bu or 2,6‐ i Pr 2 C 6 H 3 ) with K 2 [COT] (COT=C 8 H 8 ) or Li 2 [COT′′] (COT′′=1,4‐C 8 H 6 (SiMe 3 ) 2 ) gave the monomeric complexes [Ti(NR)(η 8 ‐COT)] or [Ti(NR)(η 8 ‐COT′′)], respectively. The pseudo‐two coordinate, ′pogo stick′ geometry for these complexes is unique in both early transition‐metal and cyclooctatetraenyl ligand chemistry. In contrast, reaction of [Ti(N‐2,6‐Me 2 C 6 H 3 )Cl 2 (py) 3 ] with K 2 [COT] gave the μ‐imido‐bridged dimer [Ti 2 (μ‐N‐2,6‐Me 2 C 6 H 3 ) 2 (η 8 ‐COT) 2 ]. It appears that as the steric bulk of the imido and C 8 ring substituents are decreased, dimerisation becomes more favourable. Aryl imido COT complexes were also prepared by imido ligand exchange reactions between anilines and [Ti(N t Bu)(η 8 ‐COT)] or [Ti(N t Bu)(η 8 ‐COT′′)]. The complexes [Ti(N t Bu)(η 8 ‐COT)], [Ti(N‐2,6‐ i Pr 2 C 6 H 3 ) 2 (η 8 ‐COT)] and [Ti 2 (μ‐N‐2,6‐Me 2 C 6 H 3 ) 2 (η 8 ‐COT) 2 ] have been crystallographically characterised. The electronic structures of both the monomeric and dimeric complexes have been investigated by using density functional theory (DFT) calculations and gas‐phase photoelectron spectroscopy. The most striking aspect of the bonding is that binding to the imido nitrogen atom is primarily through σ and π interactions, whereas that to the COT or COT′′ ring is almost exclusively through δ symmetry orbitals. A DFT‐based comparison between the bonding in [Ti(N t Bu)(η 8 ‐COT)] and the bonding in the previously reported late transition‐metal ′pogo‐stick′ complexes [Os(N t Bu)(η 6 ‐C 6 Me 6 )], [Ir(N t Bu)(η 5 ‐C 5 Me 5 )] and [Ni(NO)(η 5 ‐C 5 H 5 )] has also been undertaken.