Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY, UK.
Dalton Trans. 2011 Mar 7;40(9):2033-7. doi: 10.1039/c0dt01542c. Epub 2011 Jan 19.
In this paper a series of eight Ti(IV) piperazine based complexes have been prepared and fully characterised in the solid-state by X-ray crystallography and in solution via NMR spectroscopy. In the solid-state either Ti(2)(L)(O(i)Pr)(6) or Ti(2)(L)(2)(O(i)Pr)(4) were observed depending upon the nature of the starting ligand. For complexes with less sterically demanding ligands (1H(2) and 2H(2)) an equilibrium was observed: 2 Ti(2)(L)(O(i)Pr)(6) ⇔ Ti(2)(L)(2)(O(i)Pr)(4) + 2 Ti(O(i)Pr)(4). The thermodynamic properties (ΔG, ΔH and ΔS) have been investigated via variable temperature NMR spectroscopy. With more sterically demanding ligands (3-8H(2)) the Ti(2)(L)(O(i)Pr)(6) form was the most prevalent in the solid-state and in solution. These complexes have been tested for the production of polylactide under melt and solution conditions with high conversions being obtained.
本文合成了一系列八种基于哌嗪的 Ti(IV) 配合物，并通过 X 射线晶体学和 NMR 光谱在固态和溶液中对其进行了全面表征。在固态中，取决于起始配体的性质，观察到 Ti(2)(L)(O(i)Pr)(6)或 Ti(2)(L)(2)(O(i)Pr)(4)。对于具有较小空间位阻要求的配体（1H(2)和 2H(2)），观察到平衡：2 Ti(2)(L)(O(i)Pr)(6) ⇔ Ti(2)(L)(2)(O(i)Pr)(4) + 2 Ti(O(i)Pr)(4)。通过变温 NMR 光谱研究了热力学性质（ΔG、ΔH 和 ΔS）。对于具有更大空间位阻要求的配体（3-8H(2)），Ti(2)(L)(O(i)Pr)(6)形式在固态和溶液中最为普遍。这些配合物已在熔融和溶液条件下用于生产聚乳酸，获得了较高的转化率。
