A series of imine and amine Schiff-base tin(ii) complexes were synthesized. Complexes having dimethylamino side arm appears to be innocent while those having pyridyl side arm underwent unusual ligand dimerization.
A series of tin(II) complexes supported by N 2 O 2 bis(phenol)-amine ligands were prepared from the reactions of the corresponding ligands with Sn[N(SiMe 3 ) 2 ] 2 in benzene at room temperature. The ligands were designed to have different substituted group at the ortho-position on the aryl rings (R = t Bu, CH 3 ) and N-containing side arm (E = CH 2 NEt 2 and pyridine) giving a variation of tin(II) complexes (R = t Bu, E = CH 2 NEt 2 , 2a; R = t Bu, E = py, 2b; R = CH 3 , E = CH 2 NEt 2 , 2c; R = CH 3 , E = py, 2d). All complexes were characterized by NMR spectroscopy and single-crystal X-ray analysis. The single-crystal X-ray crystallography revealed that all complexes have a monomeric four-coordinate tin center with a distorted seesaw structure. All complexes are active for solvent-free polymerization of L-lactide at 120 C giving poly(L-lactide) with narrow to moderate dispersity (Ð = 1.12-1.56). In the presence of benzyl alcohol during the polymerization, the resulting polymer was found to be linear having benzyl alcohol as the end group while, in the absence of benzyl alcohol, the polymer was cyclic. The large t Bu group at the ortho-position was found to decrease polymerization activity while the more basic CH 2 NEt 2 group was found to increase the polymerization activity. The polymerization of rac-lactide under a similar condition gave PLA having a slight heterotactic bias for all catalysts.
Bis(amidinate) tin(II) complex (1) was reported as active catalyst for ring‐opening copolymerization of cyclic anhydrides and epoxides via a binary catalyst system. Polymerizations of six combinations of epoxides and cyclic anhydrides were carried out giving highly alternating poly(anhydride‐alt‐epoxide) with narrow dispersities, except for cyclohexene oxide where significant amount of ether linkage up to 62 % was observed. This ether linkages could be diminished by increasing the amount of cocatalyst to over 3 equiv. Six well‐known cocatalysts were screened where PPNCl was found to be the best cocatalyst.
A facile alcoholysis of L-lactide (LA) and lactones was developed using inexpensive and commercially available Al(OiPr)3 (1), Ti(OiPr)4 (2), and Zr(OiPr)4.iPrOH (3) yielding alkyl (S,S)-lactyllactates and hydroxy esters. Complex 1...
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