Phosphorus atomic properties

Table 4. Properties and Electronegativity Differences of Phosphorus—Atom Bonds ...

The nucleophilic properties of phosphorus in phosphaferrocene were demonstrated by reaction with n-butyllithium occurring at the phosphorus atom (81IC3252 820M312). 

Phospholes and analogs offer a wide variety of coordination modes and reactivity patterns, from the ti E) (E = P, As, Sb, Bi) through ri -dienic to ri -donor function, including numerous and different mixed coordination modes. Electrophilic substitution at the carbon atoms and nucleophilic properties of the phosphorus atom are well documented. In the ri -coordinated species, group V heteroles nearly acquire planarity and features of the ir-delocalized moieties (heterocymantrenes and -ferrocenes). 

Significant advance in the field of asymmetric catalysis was also achieved with the preparation of l,2-bis(phospholano)benzene (DuPHOS 4) and its confor-mationally flexible derivative (l,2-bis(phospholano)ethane, known as BPE) by Burk et al. [59]. Two main distinctive features embodied by these Hgands, as compared to other known chiral diphosphine ligands, are the electron-rich character of the phosphorus atoms on the one hand and the pseudo-chirality at phosphorus atoms, on the other. These properties are responsible for both the high activity of the corresponding metal complex and an enantioselection indepen-... 

As just mentioned, phosphorus porphyrins have unique photochemical properties. Their photophysics is also interesting. Emitter-quencher assemblies based on porphyrin building blocks have attracted attention due to their potential to serve as models in photosynthetic research (see [90] for an example) or for the development of photoswitches that could be used for the fabrication of molecular electronic/optical devices. In this context, Maiya and coworkers constructed a P(VI) porphyrin system 59b with two switchable azobenzene groups positioned in the apical positions of the pseudo-octahedral phosphorus atom [92]. Photoswitch ability (luminescence on/off) was demonstrated as... 

At the Department of Organic Chemistry and Technology, Budapest University of Technology and Economics, we have been dealing with the synthesis and utilization of P-heterocycles for more than two decades. In this chapter, the synthesis and properties of phospholes with bulky substituent on the phosphorus atom are described. 

The cyclic phosphoranes so obtained demonstrate properties typical for the compounds with pentacoordinated phosphorus atom (Scheme 30) [78, 83],... 

The series of wide-bite-angle, bulky ligands derived from a cyclobutene scaffold gave Pd complexes (117) showing appreciable activity in the cross-coupling of reactive aryl bromides with trimethylsilylacetylene. A considerable shift of electron density to the phosphorus atoms, probably arising from alternative aromatic canonical structures, may account for the ligand properties.422... 

These reactions may be considered to be a method of obtaining 1,3,2,5-dioxaborataphosphoniarinanes with different substituents at carbon and phosphorus atoms of the ring. Comparing the properties of cyclic oxyalkyl-phosphines and boryloxyalkylphosphines, it should be noted that in both cases the reaction with alkyl halides results in the formation of a tertiary phosphonium salt. The reaction with electrophilic reagents such as diphe-nylchlorophosphine and diphenylchloroborane proceeded quite differently [Eq. (100)]. 

The electronic properties around the phosphorus atom can be varied by manipulation of the groups on that atom. MOD-DIOP (12c) was developed by Achiwa and used to reduce itaconic acids [68-72, 75, 103]. Some variations built on BCPM (18e), itself a variant of BPPM, such as the MOD-BCPM (18f) and MCCPM (18g) [88-93, 95-98, 104]. Other variants are PYRPHOS (21a also called DeguPHOS) [105, 106], DPCP (22) [107], NorPhos (23) [108], BDPP (24a) (also called SkewPHOS) [109-111], and PPCP (25) [112]. 

The properties result from both the nature of the metal atom and the nature of the organic substituents on the phosphorus atom... 

The phosphorus atom in a r-coordinated phospholyl ligand still exhibits a lone-pair of electrons that is capable of binding a second metal atom, so that a phospholyl complex such as phosphaferrocene is—in contrast to ferrocene—itself a ligand. This special property which has no direct correspondence in the chemistry of cyclopentadienyl complexes has recently been fruitfully exploited as the underlying principle which allowed the introduction of phosphaferrocenes as effective ligands in catalytic applications [10, 13, 14]. 

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