1.5- Dithia-2,4,6,8-tetrazocine, structure

The ultraviolet spectra of l,5-dithia-2,4,6,8-tetrazocines (16 R=Ph) (klllM 306.5 nm) and (16 R = NMe,) ( mH 229nm) reflect the unusual structural dependence on substitution that exists for these compounds (81JA1540). Whereas the former compound has perfectly planar eight-membered ring, the 3,7-bis(dimethylamino) derivative was folded about an axis drawn through the two sulfur atoms as shown in (17) (see also Sec. 2.5.4.2.2). 

Only scant reference has been made to model studies on these types of compounds. Thus ab initio (STO-3G) and MNDO calculations on l,5-dithia-2,4,6,8-tetrazocine propound a preference for the lOrc-electron planar monocyclic structure (3) (X = H), and suggest that the bicyclic [l,2,5]thiadiazolo[3,4-c][l,2,5]thiadiazole-2,5-S(IV) (4), an 8n system with a transannular C—C bond could never be the stable structure for this molecule. Hence it is proposed the preparation of... 

Of theoretical interest, l,5-dithia-2,4,6,8-tetrazocine and its derivatives exhibit unusual electronic and structural properties. 

In an attempt to explain the structural dichotomy exhibited by l,5-dithia-2,4,6,8-tetrazocines (see Section 9.26.4.2), a series of calculations have been performed on the system. Several studies have been conducted on the system (1) and derivatives using ab initio and semiempirical methods (84ICA55, 84JA312, 84JA3437, 87JCS(P2)259>. Table 1 summarizes the results of the calculations on the three possible geometries for the parent compound. The l,5-dithia-2,4,6,8-tetrazocine system prefers to adopt a planar lOn-electron monocyclic structure (la). Substituents at the carbon atoms with... 

The electronic spectrum of 3,7-diamino-l,5-dithia-2,4,6,8-tetrazocine (2) has been computed by the CNDO-CI method for the geometries (la) and (lb) corresponding to Djh and C2, symmetries, respectively. The results for the bicyclic >2h structure compare well with the experimentally determined spectrum <84ICA55>. 

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