Coordination chemistry of tin: Part III. The crystal structure and thermal behavior of dipotassium dimethyl-tetrafluoro-stannate dihydrate, K2[(CH3)2SnF4]·2H2O

Reaction of (CH3)2SnF2 with two equivalents of KF in aqueous medium leads to the formation of the complex salt K2[(CH3)2SnF4]·2H2O (1). Its crystal structure was determined by single-crystal X-ray diffraction. Complex 1 crystallizes in the monoclinic space group C2 (No. 5) with the lattice parameters a=9.265(1), b=7.556(1), c=7.076(1) Å; β=98.21(1)° and Z=2. The structure is characterized by the anion [(CH3)2SnF4]2− in which the tin atom adopts a slightly distorted octahedral coordination, with the methyl groups in trans position. The potassium cations are pentacoordinated from three fluorine atoms and the oxygen atoms of two water molecules in the form of a distorted square pyramid. In addition, the thermal behavior of the compound was studied with the aid of TG/DSC-measurements coupled with MS, revealing that the dehydration of 1 takes place at 75 °C, with an enthalpy of 57.79 kJ mol−1, and that it decomposes without melting in two further endothermic steps to undetermined phases in the system KF–SnF2–SnF4 and free carbon (∼0.1%).