Synthesis of diorganotin derivatives containing asymmetric disubstituted bis(pyrazol-1-yl)methanes: X-ray crystal structures of (3-isopropylpyrazol-1-yl-5 '-isopropylpyrazol-1-yl)methane diphenyltin(IV) dibromide and bis(5-isopropylpyrazol-1-yl)metha

摘要

The reaction of 3-tert-butylpyrazole with dibromomethane under phase-transfer catalytic conditions afforded a new ligand, bis(3-tert-butylpyrazol-1-yl)methane [CH2(3-Bu(t)Pz)(2)]. However, the reaction of 3-isopropylpyrazole with dibromomethane under the same conditions yielded three isomers: bis(5-isopropylpyrazol-1-yl)methane [CH2(5-iPrPz)(2)], (3-isopropylpyrazol-1-yl-5'-isopropylpyrazol-1-yl) methane [CH2(3-iPrPz-5'-iPrPz)] and bis(3-isopropylpyrazol-1-yl)methane [CH2(5-iPrPz)(2)]. Although CH2(5-iPrPz), suffered the greatest degree of steric hindrance, this ligand was obtained in highest yield. Upon treating the isomeric mixture with diorganotin halides in petroleum ether (60-90 degrees C), the isomers were isolated in the form of diorganotin derivatives of bis(pyrazol-1-yl)methanes. The crystal structures of CH2(3-iPrPz-5'-iPrPz) SnPh2Br2 and CH2(5-iPrPz)(2)SnPh2Br2 determined by X-ray crystallography indicated that the isopropyl group in the 3-position of the pyrazole ring decreased the coordination ability of CH, (3-iPrPz-5'-iPrPz), and the average Sn-N distance in CH2(3-iPrPz 5'-iPrPz) SnPh2Br2 (2.52 Angstrom) was longer than that in CH2(5-iPrPz)(2)SnPh2Br2 (2.435 Angstrom). (C) 2000 Elsevier Science Ltd All rights reserved. [References: 26]