Metal clusters, principal types

The application of such linguistic rules presupposed (as was also remarked above) classes of substances that were already distributed into the five principal types of compounds (column II-VI). This distribution and, a fortiori, the establishment of these five orders of compounds, were a matter of neither linguistic laws or derivations nor formal classificatory rules. Rather, they were classificatory distinctions, distributions, and arrangements resting on chemical assumptions and convictions held by the authors of the Methode. As was shown in chapter 9, the core of these assumptions and convictions developed in the course of the eighteenth century. It was in particular the traditional clusters of classes around the conception of neutral salts and that around the conception of metals, metal calces, and alloys that provided the structure within which systematically coordinated names could be elaborated. 

Table 22-2 lists some well-characterized di- and poly-nuclear, neutral, unsubstituted metal carbonyls. In all these compounds there are M—M bonds but in many cases they are supplemented by bridging CO groups of several types. The principal structural types of cluster are shown in Fig. 22-3. 

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