Phosphorus rings structure

The cage-like phosphonium salt (17) with phenyl-lithium in THF gave the phosphorane (18) which probably owes its great stability to the relief of strain in the ring structure on changing the bond angle at phosphorus to 90°. For the photolysis of (18) see Chapter 10, Section 1. 

A number of metal complexes have been prepared that have a [3.3.0] ring structure and phosphorus at the bridgehead. Schmidpeter et al. have reported the formation of complexes 129 and 130 <1996PS(118)129>. An extensive study of the reaction between activated alkynes and diphosphamanganacyclopropanes resulted in the... 

Two approaches have been used in the synthesis of these types of compounds. Small boron-phosphorus ring compounds can serve as building blocks, and addition and elimination reactions with other main group elements can then extend the cage structure (see Schemes 23 and 24, Section 12.12.6.4.5). Alternatively, an unsaturated carbenoid fragment can be added to the bicyclic fragment as illustrated in Scheme 31 <1998IC490>. 

Several books and general reviews are already available on phosphorus ring and cage systems (16). This one will focus more specifically on the coordination chemistry of molecular tetraphos-phorus-based doso-compounds, including itself and closely related analogs, and will also include structural data on both free and coordinated species. The questions of the transmission of electronic and structural effects through the molecular frame, and of the extent oftt-bonding, will be critically considered. 

A. Specific Features of the Electronic Structure of Nitrogen and Phosphorus Rings Compared with the Corresponding Parent Hydrocarbons... 

A well-defined chiral pocket produced by the binaphthyl skeleton and the appended bulky 3,3 substituents, (iii) A ring structure attached to the phosphoric acid moiety to prevent free rotation at the a-position of the phosphorus center. This feature is not found in other Bronsted acids such as carboxylic and sulfonic acids (Figure 5.2). 

In P-coordinated azaphosphole complexes (Tables 2, 4) the metal atom lies strictly in the plane of the ring and the ring structure is not significantly different from that of the free azaphosphole. Of the 3,5-di- -butyl-l,2,4-triphospholide ion both 17 and rj complexes are known. In most of the t] complexes (Table 6) the metal atom is coplanar with the ring and the sum of bond angles around the ligating phosphorus atom P-1 is 360° in accord with bonding mode (1). 

Oxidation of a A3-phosphorus atom of stable P-heterocycles is a general reaction, which leaves the basic ring structures intact in many cases. This includes the conversion of l,2-dihydro-lA3,2A3-diphosphete derivatives like lc, for example, to form l,2-dihydro-lAs,2A3-diphosphete 22. Oxidation agents used are elemental selenium or [(CH3)3Si]202 <1997CB1519>. Upon photolysis lc rearranges partly into its m-isomer Id. The mixture of isomers can be reconverted completely into the trails-isomer lc by heating <1997JOC7605>. 

Rieche and Meister34 obtained bis(l-hydroxyethyl) peroxide (21) from 2 moles of acetaldehyde and 1 mole of hydrogen peroxide. Treatment of 21 with phosphorus pentoxide in ether followed by distillation gives 3,5-dimethyl-l,2,4-trioxolan (2,3-butylene ozonide) (22) as the distillate and dimeric butylene ozonide with a ten-membered ring structure (23) as the residue.23-34 Thermal decomposition of (23) at 60 to 80° in vacua yields polymeric ethylidene peroxide (25), 3,5,7-trimethyl-l,2,4,6-tetroxepan (mono-... 

Phosphorus forms many types of hydrides (7-9), called phosphanes (Table I). Phosphine (PH3) and diphosphine (H2P—PH2) are the best known. Phosphine is a colorless, toxic gas with a characteristic smell. The higher condensed phosphorus hydrides tend to form chain and ring structures such as cyclopolyphosphine and catenapolyphosphine, respectively. The PH entity has been detected only by spectroscopic analysis, and PH5, P3H, and P18H2 have not been found. 

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