Oxygen catenation

Fluorinated Compounds that Contain Catenated Oxygen, Sulfur or Nitrogen Atoms Kirchmeier, R.L. Shrecvc. J.M. Verma, R.D. Coord. Chem. Rev. 1992, 112, 169-213. 

The pseudohalogen concept (p. 319) might lead one to expect the existence of a cyanate analogue of cyanogen but there is little evidence for NCO-OCN, consistent with the known reluctance of oxygen to catenate. By contrast. 

Catenation is well established in organotin chemistry and distannane derivatives can be prepared by standard methods (see Ge, p. 396). The compounds are more reactive than organodiger-manes e.g. Sn2Meg (mp 23°) inflames in air at its bp (182°) and absorbs oxygen slowly at room temperature to give (Me2Sn)20. Typical routes to higher polystannanes are ... 

Sulfur has a striking ability to catenate, or form chains of atoms. Oxygen s ability to form chains is very limited, with H202, 03, and the anions 02, 022-, and OG the only examples. Sulfur s ability is much more pronounced. It appears, for instance, in the existence of Ss rings, their fragments, and the long strands of plastic sulfur that form when sulfur is heated to about 200°C and suddenly... 

Poly(hydrosilane)s are stable compounds and can be manipulated in the air only for a short period since they are oxygen-sensitive. The oxidized products obtained from poly(phenylhydrosilane) exposed to the air contain the units 119-122 without the formation of silyl hydroperoxides and peroxides. In particular, units 119,120, and 121+122 were present in the relative percentages of 27,54, and 19%, respectively, which means that more than 70% of the catenated silicons are altered. 

On the other hand, formates are less stable. This seems to be related to the H-CO-S atomic catenation in which 2 is an oxygen or chlorine atom. Nevertheless, with esters, the presence of a base as well as a high temperature and pressure are necessary. In the presence of sodium methoxide in a small quantity (0.5%), at 100°C and under 70 bar, methyl formate decomposes according to the reaction below the violent release of carbon oxide creates a dangerous overpressure in the apparatus ... 

The 0=0 and S=S bond energies are 498 and 431 kj mol-1, respectively, and the 0-0 and S-S bond energies are 142 and 264. Explain why it is reasonable to expect structures containing sulfur that have extensive catenation but such structures are not expected for oxygen. 

Whereas the variously catenated modifications of elemental sulfur can be satisfactorily treated by the MM method (207), organic sulfides and other sulfur-containing molecules suffer from the same polarization problem as do oxygen-containing molecules. Thus,... 

Poly(hydrosilane)s are stable compounds and can be manipulated in the air only for a short period since they are oxygen sensitive. In order to study the oxidation products, a xylene solution of poly(phenylhydrosilane)(Mw = 2340, Mw/Mn = 1.72) was refluxed (140 °C) for 12 h in a system exposed to the air [15]. Only minor changes were observed by GPC analysis whereas FTIR showed characteristic absorptions due to siloxane-type structures on the polymer backbone. A detailed NMR analysis, based on H NMR, Si INEPT and H- Si HMQC spectroscopies, indicated that the oxidized material contains the units 7-10 shown in Scheme 8.2. In particular, units 7,8 and 9+10 were present in relative percentages of 27%, 54% and 19%, respectively, which mean that more than 70% of the catenated silicons were altered. It has also been reported that silyl hydroperoxides and peroxides are not found as products in the autoxidation of poly(phenylhy-drosilane) [16]. 

Aromatic cyclic chains are more stable than aliphatic catenated carbon chains at elevated temperatures. Thus linear phenolic and melamine polymers are more stable at elevated temperatures than polyethylene, and the corresponding cross-linked polymers are even more stable. In spite of the presence of an oxygen or a sulfur atom in the backbones of polyphenylene oxide (PPO), polyphenylene sulfide (PPS), and polyphenylene sulfone, these polymers are... 

As with nitrogen, catenation occurs only to a very limited extent. In peroxides and superoxides there are two consecutive oxygen atoms. Only in 03, Oj, and the few Rf03Rf molecules are there well-established chains of three oxygen atoms. There is a four-atom chain in 04F2. 

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