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(-TMG)4(Et)2(1) and cyclic Zn(-TMG)(Et)3(2) complexes. Further investigations have shown 2to react with alcohols, HOR, to form complexes with the general formula Zn(Et)(OR)(H-TMG)n, where OR OCH2C(CH3)3ONep, n2 (3), OC6H3(CMe3)2-2,6 DBP, n1 (4), and OC6H2But2-2,6-Me-4 DBP-4-Me, n1 (5). The addition of (Et)2Zn to a solution of 4yielded the unusual Zn2(-TMG)(-DBP)(Et)2(6). Complex 5readily reacts with the alcohol, HOR‘, yielding dinuclear compounds with the formula Zn(-OR‘)(DBP-4-Me)(H-TMG)2, where OR‘ OCH3(OMe, 7) and OCH2CH3(OEt, 8). Additionally, compound 4was reacted with EtOH, yielding a complex with the formula Zn(-OEt)(DBP)(H-TMG)2(9). The utility of compound 8for use as a catalyst in the ring-opening polymerization of rac-lactide was additionally investigated. Compounds 1−9were 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. [ABSTRACT FROM AUTHOR]