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) Å; BrSnBr=98.00(10)°], two ethyl carbons [SnC=2.11(3), 2.143(19) Å; CSnC=172.3(11)°] and the two donor N atoms of the ligand [SnN=2.379(16), 2.387(16) Å; NSnN=66.8(6)°]. The IR data and Mössbauer 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 1H NMR data indicate significant dissociation in solution. The chlorobutyl derivative exhibited significant in vitro antitumour activity against the human carcinoma cell line KB.