Disubstituted crystallographic studies

In a series of papers on the synthesis (see Section II,B,2) and properties of the lOir-electron 1,4-diazocine 44, 142, its dianion (45, 143), and its N,jV -disubstituted derivatives, groups headed by Prinzbach (75AG(E)348 79AG(E)964 80CB3161) and Vogel (79AG(E)962) carried out spectroscopic and X-ray crystallographic studies, the results of which are outlined below. 

Nemes et al.[56] describe several interesting intramolecular short contacts and an extended H-H bonding pattern that appears to contribute in holding a double-chain arrangement based on the results of an X-ray crystallographic study of (9,9 -disubstituted difluorenyl)(dimethyl) derivative of germanium. 

X-Ray crystallographic studies on calicenes tetrasubstituted by chlorine in the five-membered ring and disubstituted by either phenyl or j,-propyl groups in the three-membered ring clearly show the alternation of single and double bonds as implied by formula (XXX] [260,261], so that delocalisation of electrons and dipolar character is not a major factor. 

Since the appearance of the first reports by Cambi and Szego [1, 2], the tris(N,AT-dialkyl-dithiocarbamato)iron(III) compounds have been extensively studied and the later work has included detailed structural characterisation by X-ray diffraction methods. In addition, new dithiocarbamato-based Fe(III) spin crossover materials have been prepared, those having the alkyl substituents as part of a ring system being of particular note. A schematic representation of the structure of tris(N,AT-disubstituted-dithiocarbama-to)iron(III) is given in Fig. 1, and relevant crystallographic and magnetic data are compiled in Table 1. 

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