The Use of Reaction Calorimetric Methods for Measuring Heats of Formation of Organo-metallic Compounds

The measurement of the heats of formation of organo-metallic compounds presents, usually, a difficult task to the experimental thermochemist. Thus the method of combustion in a conventional bomb-calorimeter, although it has been applied to a number of metallic alkyls in recent years! and yielded valuable results, is nevertheless not entirely satisfactory. The difficulty is that complete oxidation of the organo-metallic compound is not always attained, and the metal may be left, after the combustion, in a partially oxidized state, as a mixture of free metal, oxides, and possibly carbonate and carbide. The development of the rotating-bomb technique offers a solution of this major difficulty, and successful studies have already been reported by Scott, Good and Waddington2 on the combustion of lead tetraethyl, and by Good, Fairbrother and Waddington'' on manganese carbonyl. One can therefore feel confident that in due course precision measurements of combustion heats of organo-metallic compounds will be made. However, it is desirable that methods other than that of combustion should be investigated, not only to provide independent checks on combustion results, but also to develop reaction calorimetric methods. Several typical reactions of organo-metallic compounds are potentially suitable for heat of formation measurements, but comparatively few such thermal studies have as yet been made. Some of these studies are briefly discussed below.