Diazaallyls of group 4 metals based on trans-1,2-diaminocyclohexane
作者:Edward J. Crust、Ian J. Munslow、Peter Scott
DOI:10.1016/j.jorganchem.2005.04.019
日期:2005.7
Amination of 1-bromo-2-methylpyridine with trans-1,2-diaminocyclohexane gives the corresponding bis(aminopyridine) H-V. 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 FIX forms bis(aminopyridinato) alkyl complexes of the type [(ZrLR2)-R-1] (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 C-2-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. (c) 2005 Elsevier B.V. All rights reserved.
Development of Amino-Oxazoline and Amino-Thiazoline Organic Catalysts for the Ring-Opening Polymerisation of Lactide
作者:Jan M. Becker、Sarah Tempelaar、Matthew J. Stanford、Ryan J. Pounder、James A. Covington、Andrew P. Dove
DOI:10.1002/chem.200902518
日期:2010.5.25
The ring‐opening polymerisation of lactide by a range of amino–oxazoline and amino–thiazolinecatalysts is reported. The more electron‐rich derivatives are demonstrated to be the most highly active and polymerisation is well controlled, as evidenced by the linear relationship between the molecular weight and both the monomer conversion and the monomer‐to‐initiator ratio. Mechanistic studies reveal