~ Pergamon 0277-5387(94)00466-8 Polyhedron Vol. 14. No. 13 14, pp. 1731 1740, 1995 Copyright ~2' 1995 Elsevier Science Ltd Printed in Great Britain. All rights reserved 0277 5387/95 $9.50+0.00 MOSSBAUER AND X-RAY STRUCTURAL STUDIES ON CHLORO(ORGANO)TIN(IV) POLYPYRAZOLYLBORATES S. CALOGERO* and L. STIEVANO Dipartimento di Chimica Fisica, Universitfi, 1-30123 Venezia, Italy G. GIOIA LOBBIA and A. CINGOLANI Dipartimento di Scienze Chimiche, Universitfi, 1-62032 Camerino, Italy and P. CECCHI Dipartimento ABAC, Universitfi della Tuscia, 1-01100 Viterbo, Italy and G. VALLE Centro dei Biopolimeri del C.N.R., 1-35100 Padova, Italy (Received 5 Auyust 1994 ; accepted 23 November 1994) Abstract--The l l9mSn MOssbauer parameters at 4.2 K for a series of compounds of general formula RnSnCI3 n" L [n = 0, 1 and 2; R = Me or Ph; L = L ° hydridotris(1H-pyrazol- 1-yl)borate, L I hydridotris(3-methyl-lH-pyrazol-l-yl)borate, L 2 hydridotris(3,5-dimethyl- 1 H-pyrazol- 1-yl)borate, or L °' tetrakis(1 H-pyrazol- l-yl)borate] are reported and discussed. The compounds generally contain a distorted octahedral tin(IV) coordination geometry with one facial N-tridentate polypyrazolylborate. The X-ray crystal structures for SnC13 • L °, Ph2SnCI" L ° and Ph2SnCI" L 2 confirm these results. Polypyrazolylborate complexes are still attracting considerable attention. ~ Part of the current interest is due to the possibility of modulating electronic and steric effects by varying the substitution pattern on the ligands. 2 In the case of organotin(IV) complexes the Lewis acidity of the metal fragment can in general be easily regulated upon substitution of electro- negative halogen atom(s) with organyl group(s). Investigations on d I° metal complexes such as (organo)tin(IV) 3 or (organo)mercury(II) 4 com- plexes, containing variously substituted pyra- zolylborates, have previously been performed. ~tgSnNMR data suggested a clear dependence of * Author to whom correspondence should be addressed. 173 the chemical shifts on the electronic demand of the tin fragment. 3b Sound correlations were also obtained with EXAFS measurements. 5 The series of tin complexes RnC13 nSn" L [n = 0, 1 and 2; R = Me or Ph; L = L ° hydridotris(lH- pyrazol-l-yl)borate, L I hydridotris(3-methyl-lH- pyrazol-l-yl)borate, L 2 hydridotris(3,5-dimethyl- 1H-pyrazol-l-yl)borate, L 3 hydridotris(3,4,5-Me3- 1H-pyrazol-l-yl)borate, L °' tetrakis(1H-pyrazol-1- yl)borate, Fig. 1] are particularly suitable as ~lgsn nuclide offers the opportunity to take advantage of sensitive techniques such as NMR and M6ssbauer spectroscopy. Additional interest in these com- pounds is conveyed by the known antimutagenic activity displayed by some of them. 6 Here a representative collection of compounds in the family are examined through M/Sssbauer spec-