Diazaallyls of group 4 metals based on trans-1,2-diaminocyclohexane |
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Authors: | Edward J Crust |
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Institution: | Department of Chemistry, University of Warwick, Gibbett Hill Road, Coventry CV4 7AL, UK |
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Abstract: | Amination of 1-bromo-2-methylpyridine with trans-1,2-diaminocyclohexane gives the corresponding bis(aminopyridine) H2L1. Conversion of the same diamine to the N,N′-bis(amino-4,4-dimethylthiazoline) H2L2 is also completed in three steps. The analogous aminooxazoline is however inaccessible, although the aminocyclohexane analogue is prepared readily. The proligand H2L1 forms bis(aminopyridinato) alkyl complexes of the type ZrL1R2] (R = CH2Ph, CH2But). The molecular structure of the neopentyl complex shows that the chiral backbone leads to a puckering of the N4Zr coordination sphere, which contrasts with the related cyclohexyl-bridged Schiff-base complexes which are essentially planar. ZrL2(CH2But)2] - the first aminothiazolinato complex - is formed similarly. A comparison of the structures of ZrL1(CH2But)2] and ZrL2(CH2But)2] indicates that the latter has a fully delocalised N-C-N system, rather similar to a bis(amidinate). Reaction of H2L2 with Ti(NMe2)4] gives TiL2(NMe2)2] which appears to be C2-symmetric like the above complexes according to NMR spectra, but has one uncoordinated thiazoline unit in the solid state. This is a result of increased ring strain at the smaller titanium metal centre. |
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Keywords: | NCN Chiral Titanium Zirconium Amidinate |
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