COMPLEXES OF STANNIC CHLORIDE WITH AROMATIC HYDROCARBONS AND OXYGEN-CONTAINING DONORS IN SOLUTION

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Abstract
Complex formation between stannic chloride and various alkylbenzenes has been investigated by means of optical measurements. It is found that weak 1:1 complexes are formed in methylene chloride solution at 25 °C. The absorption at 355 mμ can be used to determine the concentration of free stannic chloride in benzene to which oxygen-containing donors have been added. The results are interpreted in terms of 1:1 and 1:2 complex formation between stannic chloride and donor. For the stronger donors such as tetrahydrofuran and acetone, the main complexes formed with excess of stannic chloride must contain equimolar amounts of stannic chloride and donor, and it is probable that they involve tin with a coordination number of five. Ethyl esters of chloroacids are very much weaker donors than ethyl esters of unsubstituted acids. The heat of reaction for the addition of a donor molecule to the 1:1 complex is usually close to the heat of reaction for the addition of the first donor molecule to stannic chloride. The decrease in entropy in each case is approximately 30 e.u./mole.