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 SnX 4 and R 2 SnX 2 (X=Cl, Br, I; R = Me, Et, Bu, Ph) to yield adducts of types [SnX4(DMPP)] and [SnR 2 X 2 (DMPP)], respectively. The structure of [SnEt 2 Br 2 (DMPP)] has been determined by X-ray diffractometry. The crystal consists of discrete [SnEt 2 Br 2 (DMPP)] molecules with the metal atom octahedrally coordinated to two Br atoms [Sn-Br = 2.631(3), 2.703(3) A; Br-Sn-Br = 98.00(10)°], two ethyl carbons [Sn-C = 2.11(3), 2.143(19) A; C-Sn-C = 172.3(11)°] and the two donor N atoms of the ligand [Sn-N = 2.379(16), 2.387(16) A; N-Sn-N =66.8(6)°]. The IR data and Mossbauer parameters are consistent with all the organotin derivatives having, similar geometry whereas in the case of the [SnX 4 (DMPP)] complexes the results of both techniques support the expectation of cis stereochemistry. The 1 H NMR data indicate significant dissociation in solution. The chlorobutyl derivative exhibited significant in vitro antitumour activity against the human carcinoma cell line KB.