Synthesis, Structure, and Reactivity of Alkylzinc Complexes Stabilized with 1,1,3,3-Tetramethylguanidine

The synthesis and structural characterization of several novel alkylzinc guanidinate, alkoxide, and aryloxide complexes are reported. 1,1,3,3-Tetramethylguanidine, H-TMG, was successfully reacted with (Et)2Zn in a 4:3 and a 1:1 ratio to yield the corresponding linear [Zn3(μ-TMG)4(Et)2] (1) and cyclic [Zn(μ-TMG)(Et)]3 (2) complexes. Further investigations have shown 2 to react with alcohols, HOR, to form complexes with the general formula [Zn(Et)(OR)(H-TMG)]n, where OR = OCH2C(CH3)3 {ONep, n = 2 (3)}, OC6H3(CMe3)2-2,6 {DBP, n = 1 (4)}, and OC6H2But2-2,6-Me-4 {DBP-4-Me, n = 1 (5)}. The addition of (Et)2Zn to a solution of 4 yielded the unusual [Zn2(μ-TMG)(μ-DBP)(Et)2] (6). Complex 5 readily reacts with the alcohol, HOR‘, yielding dinuclear compounds with the formula [Zn(μ-OR‘)(DBP-4-Me)(H-TMG)]2, where OR‘ = OCH3 (OMe, 7) and OCH2CH3 (OEt, 8). Additionally, compound 4 was reacted with EtOH, yielding a complex with the formula [Zn(μ-OEt)(DBP)(H-TMG)]2 (9). The utility of compound 8 for use as a catalyst in the ring-opening polymerization of rac-lactide was additionally investigated. Compounds 1−9 were characterized by single-crystal X-ray diffraction. The bulk powders for all complexes were found to be in agreement with the crystal structures based on elemental analyses, FT-IR spectroscopy, and 1H and 13C NMR studies. The polymer was characterized by multi-nuclear NMR spectroscopy and MALDI-TOF mass spectrometry.

本文报道了数种新型烷基锌胍基、烷氧基及芳氧基配合物的合成与结构表征。1,1,3,3-四甲基胍（1,1,3,3-Tetramethylguanidine, H-TMG）可与二乙基锌（(Et)₂Zn）分别以4:3和1:1的摩尔比发生反应，得到对应线性结构的[Zn₃(μ-TMG)₄(Et)₂]（配合物1）与环状结构的[Zn(μ-TMG)(Et)]₃（配合物2）。进一步研究表明，配合物2可与醇HOR反应，生成通式为[Zn(Et)(OR)(H-TMG)]ₙ的配合物，其中OR分别为OCH₂C(CH₃)₃（新戊氧基，ONep，n=2，配合物3）、2,6-二叔丁基苯酚氧基（OC₆H₃(CMe₃)₂-2,6，DBP，n=1，配合物4）以及2,6-二叔丁基-4-甲基苯酚氧基（OC₆H₂But₂-2,6-Me-4，DBP-4-Me，n=1，配合物5）。向配合物4的溶液中加入二乙基锌，可得到非常规结构的[Zn₂(μ-TMG)(μ-DBP)(Et)₂]（配合物6）。配合物5可与醇HOR'顺利反应，得到通式为[Zn(μ-OR')(DBP-4-Me)(H-TMG)]₂的双核配合物，其中OR'分别为甲氧基（OCH₃，OMe，配合物7）与乙氧基（OCH₂CH₃，OEt，配合物8）。此外，将配合物4与乙醇反应，可得到分子式为[Zn(μ-OEt)(DBP)(H-TMG)]₂的配合物（配合物9）。本文还探究了配合物8作为催化剂在外消旋丙交酯开环聚合反应中的应用效用。所有配合物1~9均通过单晶X射线衍射（single-crystal X-ray diffraction）完成结构表征。基于元素分析、傅里叶变换红外（FT-IR）光谱、氢谱（¹H NMR）与碳谱（¹³C NMR）表征结果，所有配合物的本体粉末结构均与单晶衍射解析结果相符。所制备的聚合物则通过多核核磁共振波谱与基质辅助激光解吸电离飞行时间（MALDI-TOF）质谱进行了表征。