1.3- Dithianes crystal structure

A template synthesis employing Ni(OAc)2, 2,5-dihydroxy-2,5-dimethyl-1,4-dithiane, and 3,3 -iminobis(propylamine) gave the water-soluble five-coordinate complex [Ni(495)], the crystal structure of which shows trigonal bipyramidal coordination of Ni11 with the central amine and terminal thiolates in plane and the two imino nitrogens in axial positions. Solvatochromism of the complex is interpreted in terms of S" H bonding, which may be of relevance to the catalytic cycle in hydrogenases.1341... 

Ogura and coworkers178,179 continued their study of the addition of lithiated heterocycles to 2,3 5,6-di-0-isopropylidene-L-gulono-l,4-lactone (50) and related compounds. In the case of the addition of lithiated 1,3-dithiane to 50, it was shown178 by X-ray crystal-structure analysis that l-(l,3-dithian-2-yl)-2,3 5,6-di-0-isopropylidene-/3-L-gulofuranose is R at the anomeric carbon atom. This demonstrates that the product of this reaction is, surprisingly, the more sterically hindered of the two products possible. This is the opposite of that predicted for addition of the lithiated dithiane from the less hindered side of 50 if no equilibration of the initial adduct is involved. 

Reaction of bis(disilanyl)dithiane 6 with an equimolar amount of Pd(CN-t-Bu)2 in benzene was examined at room temperature. The reaction was completed within 5 min, affording l,l,2,2-tetramethyl-l,2-diphenyldisilane and a four-membered cyclic bis-(organosilyl) complex 7 in 85% yield after isolation by crystallization with pentane (Scheme 5). A crystal structure of 7 exhibited a distorted square planar structure, in which the two silicon atoms in the ring are separated only by 2.61 A. Presumably, the formation of 7 may have arisen from the simultaneous activation of the two Si—Si bonds on palladium, which led to intramolecular metathesis (disproportionation). 

Stoichiometric reaction of the triplatinum(O) isocyanide cluster Pt3(CNBu )6 with a bis(disilanyl)dithiane at 80 °C gives the Pt(rv) complex 119 directly via the double oxidation of Si-Si bonds (Equation (16)). A crystal structure confirmed the proposed formulation. 

Single crystal X-ray structural analysis was carried out for 4,7-bis(l,3-dithian-2-ylidene)-l,2,3,5,6-pentathiepane (see Section 13.17.7.13) <1995MI1>. 

The stereochemical requirements of adjacent lone electron pairs and polar bonds have been discussed in an important paper which analysed the considerable volume of available data, including those pertaining to 1,4-dithians and similar systems. The Edwards-Lemieux effect in substituted 1,4-dithians was accounted for satisfactorily by calculations using fluoromethanol as a model compound. The temperature-dependence of the F n.m.r. spectrum of perfluoro-1,4-dithian indicated a barrier to ring-inversion of 10.05 0.10 kcalmol. The fluorine chemical-shift differences at — 90 °C appeared to be consistent with a preferred chair conformation, possibly strongly puckered as in 1,4-dithian. The i.r. and Raman spectra of 1,4-dithian and 1,4-diselenan have received detailed attention, and the crystal and molecular structures of... 

The lower-melting cw-1,3-dioxide of 2,2-diphenyl-1,3-dithian (160) exists in the crystal in the conformation with both sulphoxide oxygens syn-diaxial. Other A ray data have been reported on the structure of the trimethyl-1,3,5-trithian (161) and on several 1,4-dithian derivatives. ... 

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