Complexes of tin(IV) halides and diorganotin(IV) dihalides with 3,5-dimethyl-1-(2′-pyridyl)pyrazole

3,5-Dimethyl-1-(2'-pyridyl)pyrazole (DMPP) reacts with SnX4 and R2SnX2 (X=Cl, Br, I; R = Me, Et, Bu, Ph) to yield adducts of types [SnX4(DMPP)] and [SnR2X2(DMPP)], respectively. The structure of [SnEt2Br2(DMPP)] has been determined by X-ray diffractometry. The crystal consists of discrete [SnEt2Br2(DMPP)] molecules with the metal atom octahedrally coordinated to two Br atoms [Sn-Br = 2.631(3), 2.703(3) Angstrom; Br-Sn-Br = 98.00(10)degrees], two ethyl carbons [Sn-C = 2.11(3), 2.143(19) Angstrom; C-Sn-C = 172.3(11)degrees] and the two donor N atoms of the ligand [Sn-N = 2.379(16), 2.387(16) Angstrom; N-Sn-N = 66.8(6)degrees]. The IR data and Mossbauer parameters are consistent with all the organotin derivatives having, similar geometry whereas in the case of the [SnX4(DMPP)] complexes the results of both techniques support the expectation of cis stereochemistry. The H-1 NMR data indicate significant dissociation in solution. The chlorobutyl derivative exhibited significant in vitro antitumour activity against the human carcinoma cell line KB. (C) 2003 Elsevier B.V. All rights reserved.