Phosphorus nonequivalence

The origin of the correlation reported for phosphorus nonequivalence in diastereomeric phosphorthioic acid salts (17,61) is unclear. A direct anisotropic effect of the CSA aromatic substituent on the... 

On the basis of the deconvolution, the ABCX pattern was assigned to originate from the three complexed nonequivalent phosphorus atoms of monocyclic 1,3-diphenylphosphinopropane 3-(diphenylphosphino)-propyldiphenylphosphinerhodium(I) carbonyl hydride. 

The solution and solid P-31 NMR spectra of the prophos ligand are presented in Figure 10. As seen from this figure, the expected nonequivalence of the phosphorus atoms was observed in both spectra. The signals in the solid-state spectrum showed increased shielding relative to the solution spectrum. The solution spectrum also revealed a P-P coupling (/P P = 20.5 Hz). 

The 119Sn NMR spectrum of the adduct PhSnCl3 (EtO)2POCH2CH2PO(OEt)2 at —90 °C consists of a triplet at —557 ppm and a doublet of doublets at —551 ppm with approximately 5 1 relative intensities. These resonances were attributed to isomers of the hexacoordinate complex301,1056. The first isomer has two equivalent phosphorus atoms in the tin coordination sphere and consists of cis-fac octahedra in accordance with the preferred cis -bridging behavior of the ethylene-diphosphonate ligand. The second isomer with nonequivalent phosphorus atoms consists of cis-mer octahedra125. 

AA X See Fig. 14 Phosphorus nuclei nonequivalent J(AX) J(A X) See Fig. 12 five-line multiplet, often deceptively simple... 

In 10, there are two remote stereogenic centers at phosphorus and it was isolated as an almost equimolecular mixture of the two sets of diastereoisomers, that is, (RR/SS) and (RS/SR). In each chiral diastereoisomer, the phosphorus atoms are nonequivalent and four distinct 31P resonances were obtained almost in a 1 1 1 1 ratio <1997J(P2)1445>. The kinetics of the thermal decomposition of 11 in dibutyl phthalate was studied. The high rate of decomposition was probably determined by mutual steric influence of the bulky dinitromethylene moieties <2006RJC499>. 

A -Dioxaphospholanes show no inversion at the phosphorus atom, which can be seen in the nonequivalence of the CFj groups (273). A -Dioxaphospholanes 73 can be oxidized with halogens to form A -dioxaphospholanes 74 (228). Exchange of the halogens in 73a-c with suitable reaction partners (e.g., LiNHj) yields substituted A -phospholanes [e.g., 73g (265)] (see also Section III,A,2). 

The oxidation of (171) with (172) gave the zwitterionic compound (173) that was analyzed by X-ray crystallography and shown to contain both and atoms and a P-H bond. The P H NMR data on (173) in CDCI3 showed a high field doublet of triplets at —134.2 ppm, characteristic of hexacoordinate phosphorus with the splitting pattern due to one nonequivalent and two equivalent fluorines. 

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