“…cases depending also on steric demand. 78 However, it has been shown that the introduction of strongly electron-withdrawing substitutents such as fluoride, 79 trifluoromethyl-(CF 3 ) 80 or 2,4-bis(trifluoromethyl)phenyl-(2,4-(CF 3 ) 2 C 6 H 3 ) groups stabilize the anhydrides of the phosphinous acids. 81 The bis(bis(trifluoromethyl)phosphanyl) oxide, (CF 3 ) 2 P-O-P(CF 3 ) 2 , is stable with respect to its corresponding phosphane oxide tautomer, however, it deflagrates readily on contact with air.…”
This review aims to highlight and comprehensively summarize recent developments in the field of mixed-coordinate phosphorus chemistry. Particular attention is focused on the synthetic approaches to compounds containing at least two directly bonded phosphorus atoms in different coordination environments and their unexpected properties that are derived from spectroscopic and crystallographic data. Novel substance classes are discussed in order to supplement previous reviews about mixed-coordinate phosphorus compounds.
“…cases depending also on steric demand. 78 However, it has been shown that the introduction of strongly electron-withdrawing substitutents such as fluoride, 79 trifluoromethyl-(CF 3 ) 80 or 2,4-bis(trifluoromethyl)phenyl-(2,4-(CF 3 ) 2 C 6 H 3 ) groups stabilize the anhydrides of the phosphinous acids. 81 The bis(bis(trifluoromethyl)phosphanyl) oxide, (CF 3 ) 2 P-O-P(CF 3 ) 2 , is stable with respect to its corresponding phosphane oxide tautomer, however, it deflagrates readily on contact with air.…”
This review aims to highlight and comprehensively summarize recent developments in the field of mixed-coordinate phosphorus chemistry. Particular attention is focused on the synthetic approaches to compounds containing at least two directly bonded phosphorus atoms in different coordination environments and their unexpected properties that are derived from spectroscopic and crystallographic data. Novel substance classes are discussed in order to supplement previous reviews about mixed-coordinate phosphorus compounds.
“…Pyrophosphites are an interesting class of compounds that are the phosphorus analogues of the commonly found carboxylic acid anhydrides in organic chemistry. Pyrophosphites are useful reagents for peptide synthesis and, quite recently, were found to be useful bridging ligands for the synthesis of polynuclear metal complexes. , The ability of three-coordinate P(III) to rehybridize to four-coordinate P(V) provides the basis for the observed anhydride to tetraalkoxydiphosphine monoxide tautomerism (eq 1). , …”
Section: Introductionmentioning
confidence: 99%
“…The position of the equilibrium is dependent upon both the electronic and steric properties of the substituents on phosphorus. Alkoxy substituents on phosphorus increase the stability of the pyrophosphite tautomer relative to the diphosphine monoxide, and tetralkoxydiphosphine monoxides are reported to isomerize to pyrophosphites rapidly . Relatively little structural information is available for free uncomplexed pyrophosphites.…”
The synthesis and structural characterization of the sterically congested pyrophosphite 6-[(2,4,8,10-tetrakis(1,1-dimethylethyl)-dibenzo[d,f][1,3,2]dioxaphosphepin-6-yl)oxy]-2,4,8,10-tetrakis(1,1-dimethylethyl)-dibenzo[d,f][1,3,2]dioxaphosphepin, 3, is described. In solution at room temperature, a single species was observed that was consistent with a pyrophosphite structure without any evidence for the tautomeric diphosphine monoxide. Below the coalescence temperature (T(C)), 0 degrees C, three atropisomers were observed with relative absolute configurations of (R,R,R), (R,S,R), and (R,R,S). Ring inversion of the seven-membered rings below the T(C) is slow on the NMR time scale, which leads to observable diastereoisomerism because of the presence of two independent stereoaxes (sp2-sp2 C-C single bond connecting the two aryl rings). Additionally, a rotation about an exocyclic P-O single bond connecting the two seven-membered rings, which constitutes a third stereoaxis, is slowed on the NMR time scale. In the X-ray crystal structure of 3, the solid-state conformation was found to be the same as the major conformation in solution below the T(C), namely, the (R,R,S) atropisomer. The results of a conformational search, performed with a specifically parametrized AMBER force field, were in agreement with the 31P NMR assignment of the major (R,R,S) atropisomer, which was found to be an energy minimum. Additionally, we could independently assign the relative configuration of the minor isomers based on the calculated results.
“…Substituted diphosphane monoxides B' are also easily prepared and gained academic interest due to unexpected reactivity . The equilibrium between diphosphane monoxides R 2 P–P(O)R 2 and anhydrides of phosphorus acids R 2 P–O–PR 2 has already been studied in dependency of the substituents at phosphorus . Tautomeric proton shifts from phosphorus to oxygen have not been observed in ArP(H)–P(O)(H)Ar with bulky aryl groups (Ar = C 6 H 3 ‐2,6‐Mes 2 ) and the crystal structure determination gave a P–P single bond length of 219.46(8) pm for this diphosphane monoxide .…”
The reaction of LiP(H)Tipp (2a) and KP(H)Tipp (2b, Tipp = C6H2‐2,4,6‐iPr3), which are accessible via metalation of Tipp‐PH2 (1), with bis(4‐tert‐butylphenyl)phosphinic chloride yields Tipp‐P=P(OM)Ar2 [M = Li (3a) and K (3b)]. These complexes show characteristic chemical 31P shifts and large 1JPP coupling constants. These compounds degrade with elimination of the phosphinidene Tipp‐P: and the alkali metal diarylphosphinites M–O–PAr2 [M = Li (4a) and K (4b)]. The phosphinidene forms secondary degradation products (like the meso and R,R/S,S‐isomers of diphosphane Tipp‐P(H)–P(H)Tipp (5) via insertion into a P–H bond of newly formed Tipp‐PH2), whereas the crystallization of [Tipp‐P=P(OLi)Ar2·LiOPAr2·LiCl·2Et2O]2 (i.e. [3a·4a·LiCl·2Et2O]2) succeeds from diethyl ether. The metathesis reactions of LiP(SiiPr3)Tipp and LiP(SiiPr3)Mes (Mes = C6H2‐2,4,6‐Me3) with Ar2P(O)Cl yield Ar*‐P=P(OSiiPr3)Ar2 (Ar* = Mes, Tipp) which degrade to Ar2POSiiPr3 and other secondary products.
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