Toggle Main Menu Toggle Search

Open Access padlockePrints

N-alkoxy-beta-ketoiminate complexes of groups 4 and 5: Synthesis and characterization of the complexes [(eta(5)-C5H4R)M{CH3C(O)CHC(NCH2CHR ' O)CH3}Cl-n] (M = Ti, n = 1; M = Nb, n = 2; R = H, Me; R ' = H, Me), [Ti{CH3C(O)CHC(NCH2CHR ' O)CH3}Cl-2(thf)], and [Ti{CH3C(O)CHC(NCH2CHR ' O)CH3}(2)]

Lookup NU author(s): Dr Simon Doherty, Dr John Errington, Neil Housley, Emeritus Professor Bill Clegg, Dr Mark Elsegood

Downloads

Full text for this publication is not currently held within this repository. Alternative links are provided below where available.


Abstract

The synthesis and characterization of a range of N-alkoxo beta-ketoiminate complexes of groups 4 and 5 are reported. Reactions between the acylic N-hydroxyalkyl beta-ketoimines CH3C(O)CH2C(NCH2CHR ' OH)CH3 (R ' = H, Me) and [(eta(5)-C5H4R)TiCl3] (R = H, Me) in the presence of triethylamine afford the monocyclopentadienyl derivatives [(eta(5)-C5H4R)Ti-{CH3C(O)CHC(NCH2CHR ' O)CH3}Cl] (R = H, R ' = H, 2a; R = Me, R ' = H, 2b; R = H: R ' = Me, 2c; R = Me, R ' = Me, 2d). Complex 2a adopts a square pyramidal coordination geometry with the Cp occupying the apical site and the terdentate ketoiminate and chloride occupying basal positions. Upon standing in thf, solutions of 2a-d containing NEt3HCl deposit deep orange crystals of [Ti{CH3C(O)CHC(NCH2CHR ' O)CH3)Cl-2(thf)] (R ' = H, 3a; R ' = Me, 3b) via protonolysis of the Ti-Cp bond. Alternatively, compounds 3a and 3b can be prepared in near quantitative yield either from the reaction between [TiCL4(thf)(2)] and the corresponding acylic N-hydroxyalkyl beta-ketoimine, in the presence of NEt3, or via a ligand exchange reaction between [Ti(OPri)(2)Cl-2] and the N-hydroxyalkyl beta-ketoimine. Variable-temperature H-1 NMR studies of 3a and 3b have shown that stereoisomers of these complexes interchange via a dissociative dynamic process, involving the trigonal bypyramidal intermediate [Ti{CH3C(O)CHC(NCH2CHR ' O)CH3}Cl-2]. The free energy of activation associated with this exchange has been determined (Delta G(double dagger) = 45.5 kJ mol(-1), 3a; Delta G(double dagger) = 47.0 kJ mol(-1), 3b). Surprisingly, treatment of [Ti(OPri)al with N-hydroxyalkyl beta-ketoimine (1:1) results in complete alcoholysis to afford [Ti{CH3C(O)CHC(NCH2CHR ' O)CH3}(2)] (R ' = H, 4a; R ' = Me, 4b), which contain two meridianally coordinated terdentate ketoiminate ligands. The reactions between N-hydroxyalkyl beta-ketoimine derivatives and [(eta(5)-C5H4R)NbCl4] afford [(eta(5)-C5H4R)Nb{CH3C(O)CHC(NCH2CHR ' O)CH3}Cl-2] (R = H, R ' = H, 5a; R = Me, R ' = H, 5b; R = H, R ' = Me, 5c; R = Me, R ' = Me, 5d). A single-crystal X-ray study of 5a revealed a structure based on an octahedral geometry, such that the nitrogen of the mer-terdentate ligand is trans to the Cp and the two chloro Ligands mutually trans. The single-crystal X-ray structures of 2a, 3a, 3b, 4a . CH2Cl2, and 5a are reported.


Publication metadata

Author(s): Elsegood MRJ; Errington RJ; Doherty S; Housley N; Clegg W; Ridland J

Publication type: Article

Publication status: Published

Journal: Organometallics

Year: 1999

Volume: 18

Issue: 6

Pages: 1018-1029

Print publication date: 01/03/1999

ISSN (print): 0276-7333

ISSN (electronic): 1520-6041

Publisher: American Chemical Society

URL: http://dx.doi.org/10.1021/om980510q

DOI: 10.1021/om980510q


Altmetrics

Altmetrics provided by Altmetric


Actions

Find at Newcastle University icon    Link to this publication


Share