Phosphorus structures with

Black phosphorus is formed when white phosphorus is heated under very high pressure (12 000 atmospheres). Black phosphorus has a well-established corrugated sheet structure with each phos phorus atom bonded to three neighbours. The bonding lorces between layers are weak and give rise to flaky crystals which conduct electricity, properties similar to those ol graphite, it is less reactive than either white or red phosphorus. 

Phosphine is a colourless gas at room temperature, boiling point 183K. with an unpleasant odour it is extremely poisonous. Like ammonia, phosphine has an essentially tetrahedral structure with one position occupied by a lone pair of electrons. Phosphorus, however, is a larger atom than nitrogen and the lone pair of electrons on the phosphorus are much less concentrated in space. Thus phosphine has a very much smaller dipole moment than ammonia. Hence phosphine is not associated (like ammonia) in the liquid state (see data in Table 9.2) and it is only sparingly soluble in water. 

The grades with the 410 or 420 numerals are the basic 13% chromium type with varied carbon content. The additions of sulphur or selenium (possibly with phosphorus) to some grades (416 group) is to improve machinability. 431S29 has increased chromium content to improve corrosion resistance, but reference to Fig. 3.11 shows that such addition alone would lead to a mixed martensite-5-ferrite structure with certain disadvantages to mechanical properties. The nickel addition is to limit ferrite content. 

PdP2, however, contains continuous chains of phosphorus atoms (with, as expected, planar 4-coordinate Pd) while PdP3 has the CoAs3 structure (P4 rings). 

Semiconductor properties are imparted by doping its structure with boron, phosphorus, or arsenic atoms. Silicon is relatively inert chemically but is attacked by halogens and dilute alkalies. It has good optical transmission especially in the infra-red. 

A variety of complexes with numerous novel structural features have also been unearthed in the study of phosphorus ligands with group 13 halides which will not be described in this review [38, 39]. 

The diazaphosphane or aminoiminophosphane ligands with a NPN framework are another subclass of cyclophosphazenes. These compounds with both phosphorus in oxidation state (111) [104-110] and (V) [111-112] have been employed in the synthesis of four membered heterocycles and coordination chemistry with group 13 derivatives. Several complexes of trivalent phosphorus derivatives with both aluminum halide and alkyls are known as illustrated for 48 in Scheme 21 [113-119]. The structure determination of 48 confirms the formation of a four membered metallacycle [116, 117],... 

Many types of phosphorus-phosphorus bonds are known, but it is rare to find such bonds in hexacoordinated phosphorus compounds (with the exception of 57). Cavell reported in 1998 the reaction of PCI5 with phenylbis(o-(trimethyl-siloxy)phenyl)phosphane, yielding the corresponding bischelate 61 in decent yield (52%) [99]. The octahedral nature of the central phosphorus atom was unambiguously determined by X-ray structural analysis. Two short axial bonds (2.202 A) lie perpendicular to the pseudo-octahedral equatorial plane. 

Yamashita M (2007) Preparation, Structure, and Biological Properties of Phosphorus Heterocycles with a C - P Ring System. 8 173-222... 

Although 1,3,2-diazaphospholenium cations are usually prepared from neutral NHPs or 1,3,2-diazaphospholes via Lewis-acid induced substituent abstraction or A-alkylation, respectively (cf. Sect. 3.1.2), the group of Cowley was the first to describe a direct conversion of a-diimines into cationic heterocycles by means of a reaction that can be described as capture of a P(I) cation by diazabutadiene via [4+1] cycloaddition [31] (Scheme 4). The P(I) moiety is either generated by reduction of phosphorus trihalides with tin dichloride in the presence of the diimine [31] or, even more simply, by spontaneous disproportionation of phosphorus triiodide in the presence of the diimine [32], The reaction is of particular value as it provides a straightforward access to annulated heterocyclic ring systems. Thus, the tricyclic structure of 11 is readily assembled by addition of a P(I) moiety to an acenaphthene-diimine [31], and the pyrido-annulated cationic NHP 12 is generated by action of appropriate... 

Hypervalent Structures with a Pentacoordinated Phosphorus and Two Five-Membered Rings... 

Coordination behavior of 2,5-dimethyl-4-phosphino-[l,2,3]diazaphosphole as potential multifunctional ligand has been investigated for complexation with a variety of metal centers. Despite the presence of three possible coordination sites, coordination takes place via exocyclic phosphino phosphorus (Structure 5) [81-83, 115],... 

Our focus is on the most comprehensively studied series, the monophosphides of the first-row transition metals, whose structures successively distort from NaCl-type (ScP) to TiAs-type (TiP), NiAs-type (VP), MnP-type (CrP, MnP, FeP, CoP), and NiP-type, forming stronger metal-metal and phosphorus-phosphorus bonding with greater electron count (Fig. 11) [63-65], The P atoms are six-coordinate, but... 

Acyclic boryloxyalkylphosphines with tricoordinated phosphorus and boron are capable of forming cyclic betaine structures with four-coordinated P and B atoms. The ability to be converted into a more stable four-coordinated state accounts for many chemical transformations of boryloxyalkylphosphines. Diphenylboryloxymethyl(methyl) phenylphosphine (92) readily disproportionates to give 1,3,2,5-dioxabora-taphosphoniarinane (103). [Eq. (60)] (83IZV2541). Similar interaction is... 

However, other reaction directions via the formation of the phosphorane structure with migration of the methyl anion from one phosphorus atom... 

Organometallic betaines of type I can be considered as the closest structural analogs of carbon betaines of the (+ )P-C-C-X( ) type (IV), which were regarded for a long time as possible intermediates in classical reactions of carbonyl and thiocarbonyl compounds with phosphorus ylides (Wittig and Corey-Chaykovsky reactions and related processes,5,6 Scheme 1). Vedejs and coworkers7,8 proved unambiguously that oxapho-sphetanes (III) are true intermediates in the reactions of nonstabilized phosphorus ylides with carbonyl compounds. The formation of oxabetaines (+)p-c-c-o(-> was detected only in the form of their adducts with lithium salts.9,10... 

To date, following significant contributions by Knowles, Kagan, Noyori, and Burk et al., thousands of efficient chiral phosphorus ligands with diverse structures have been developed for asymmetric hydrogenation, and their catalytic asymmetric hydrogenation processes have been extensively utilized in both academic research and industry. 

Hydrogenation of ct-dehydroamino acid derivatives has been a typical reaction to test the efficiency of new chiral phosphorus ligands. Indeed, a number of chiral phosphorus ligands with great structural diversity are found to be effective for the Rh-catalyzed hydrogenation of a-dehydroamino acid derivatives. Since (Z)-2-(acetamido)cinnamic... 

The electron structure of phosphorus ends with 3s2 3p3 3d°. As we saw previously, the phosphorus atom normally forms three bonds. However, it is able to undergo sp3d hybridization as shown below. 

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