Reduced inorganic phosphorus in the natural environment: significance, speciation and determination

It is commonly assumed that phosphorus occurs almost exclusively in the environment as fully oxidized phosphate (primarily H₂PO₄⁻ and HPO₄²⁻, where the oxidation state of phosphorus is +V). Recent developments in the field of microbiology and research on the origin of life have suggested a possibly significant role for reduced, inorganic forms of phosphorus in bacterial metabolism and as evolutionary precursors of biological phosphate compounds. Reduced inorganic forms of phosphorus include phosphorus acid (H₃PO₃, P(+III)), hypophosphorus acid (H₃PO₂, P(+I)) and various forms of phosphides (P(−III)). Reduced phosphorus has been detected in anaerobic sediments, sewage treatment facilities and in industrial and agricultural processes.Microbiological evidence suggests a significant role for reduced phosphorus species in metabolic processes and raises interesting questions regarding the biogeochemistry of this nutrient in the environment. However, the paucity of data on the presence and cycling of reduced phosphorus compounds in the environment requires attention in order to elucidate the role of these compounds in natural systems. This paper discusses the significance of reduced phosphorus in the natural environment, its speciation and methods of detection.     

A simple TiCl4 promoted arylation of orthoformate and benzyl ethers by N,N-dialkylarylamines

N,N-Dialkylarylamines react with trimethyl orthoformate and TiCl₄ under ambient conditions to give the corresponding formyl derivatives in 75-89% yields, whereas the corresponding arylated products are obtained from benzyl ethers and acetals in 42-78% yields.     

Efficient esterification of carboxylic acids and phosphonic acids with trialkyl orthoacetate in ionic liquid

An operationally simple, inexpensive, efficient, and environmentally friendly esterification of various carboxylic acids, phosphonic acids, and phosphinic acids with triethyl orthoacetate or trimethyl orthoacetate under neutral conditions in a typical room temperature ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate, was successfully carried out to provide the corresponding ethyl esters or methyl esters in high yields.     

Tunable phosphinite, phosphite and phosphoramidite ligands for the asymmetric hydrovinylation reactions

Only a limited number of ligands have been successfully employed for the Ni-catalyzed asymmetric hydrovinylation reaction. Diarylphosphinites, carrying β-acylamino groups prepared from readily available carbohydrates, in conjunction with highly dissociated counteranions {[(3,5-(CF₃)₂C₆H₃]₄B⁻ or SbF₆⁻}, effect the hydrovinylation of vinylarenes under ambient pressure of ethylene with high enantioselectivity. Nitrogen substituents such as -COCF₃ and COPh groups lead to isomerization of the primary products (3-arylbutenes) to Z- and E-2-aryl-2-butenes. In a prototypical synthesis of a 2-arylproionic acid, (S)-3-(4-bromophenyl)-1-butene (89% ee) has be transformed into (R)-ibuprofen by Ni-catalyzed cross-coupling with i-BuMgBr, followed by oxidation of the double bond with NaIO₄ and KMnO₄. Asymmetric codimerization of norbonene and ethylene using binaphthol-derived phosphoramidites as ligands gives 1:1, 2:1 or polymeric adducts depending on the relative configurations and nature of the BINAP and amine moieties. With one of the phosphoramidite-Ni complexes, counteranions BAr₄⁻ [Ar=3,5-(CF₃)₂C₆H₃] and SbF₆⁻, which had been used interchangeably in other reactions, give either a 1:1 adduct or a 2:1 adduct, respectively.     

Ozone as an oxygen source for alkene ene-reactions

Summary A strategy was developed which uses the adduct of ozone and triphenyl phosphite as a substitute for photochemically generated singlet oxygen in ene reactions of olefins. The resulting allylic hydroperoxide can be conveniently reduced by a second mole of phosphite to yield the corresponding allylic alcohol. The aryl phosphate produced as the by-product can either be recycled by reduction or used itself as a commodity. As an example, the two key steps of the rose oxide synthesis involving singlet oxygen can thus be reduced to a one pot procedure. With respect to the reaction mechanism, additional arguments for the direct reaction of the olefin with the phosphite ozonide were gathered. A simple decomposition of the ozonide to produce singlet oxygen was made rather unlikely.

---

Ozon als Sauerstoffquelle für En-Reaktionen von Olefinen

Zusammenfassung Es wurde eine Strategie zum Ersatz von photochemisch erzeugtem Singlett-Sauerstoff durch das Addukt aus Ozon und Triphenylphosphit zum Einsatz in En-Reaktionen von Olefinen entwickelt. Das entstehende allylische Hydroperoxid kann durch ein zweites Molekül Phosphit einfach zum entsprechenden allylischen Alkolhol reduziert werden. Das als Nebenprodukt entstehende Arylphosphat kann entweder durch Reduktion recycliert oder direkt als Handelsware weiterverwendet werden. Auf diese Weise können zum Beispiel die beiden Stufen der Rosenoxidsynthese, an denen Singlett-Sauerstoff beteiligt ist, zu einer Eintopfreaktion vereinfacht werden. Bezüglich des Reaktionsmechanismus wurden zusätzliche Hinweise auf die direkte Reaktion des Phosphitozonids mit dem Olefin gefunden. Eine Zersetzung des Ozonids unter Bildung von Singlettsauerstoff ist nicht wahrscheinlich.

     

The Crystal Structure of Trimethyl Borate by Neutron and X‐ray Powder Diffraction

The crystal structure of one of the simplest organoboron compounds, trimethyl borate does not appear to have been determined hitherto. The compound is of interest for the study of π‐donor ligands and their interaction with the π‐acceptor behavior of trigonal boron and the consequences of such interactions on molecular structure. We used powder neutron (with isotopically labeled material) and X‐ray diffraction to determine the crystal structure of trimethyl borate at 15 K and 200 K (neutron) and 200 K (X‐ray). The material is hexagonal (Z = 2) with a = b = 6.950(8) Å and c = 6.501(3) Å at 15 K. The unit cell volume is 272.00(1) ų. The space group is P6₃/m (SG 176) at 15 K and 200 K. This is the first crystal structure solved on the Neutron Powder Diffractometer (NPDF) at the Lujan Center.     

Synthesis,Structure and Reactivity of [1, 2‐Bis(diphenylphosphinite)ethane]bromotricarbonylmanganese(I) with Reactions of Phosphites,Phosphonites. and Phosphinites

The manganese carbonyl complex [MnBr(CO)₃ L ] ( 1 ), where L = Ph₂POCH₂CH₂OPPh₂, was prepared by reacting [MnBr(CO)₅] with the bidentate ligand 1, 2‐Bis(diphenylphosphinite)ethane. From this compound and the appropriate phosphite, phosphinite or phosphonite ligands were synthesized the complexes [MnBr(CO)₂ LL ′], where L ′ = P(OMe)₃ ( 2 ) or P(OEt)₃ ( 3 ) and [MnBr(CO)₃ L ′₂], where L ′ =PPh(OEt)₂ ( 4 ) or PPh₂(OEt) ( 5 ). The obtained compounds have been characterized by elemental analysis, mass spectrometry, IR and NMR (¹H, ¹³C and ³¹P) spectroscopies and X‐ray diffractometry for the complexes 1 , 4 and 5 .     

Synthese von [(η-C5H5)2Ti(Cl)(CCSiMe3)]Ni(CO) und dessen Reaktionsverhalten gegenüber Phosphiten: die Festkörperstruktur von (CO)2Ni[P(OC6H4CH3-2)3]2

Treatment of [Ti](Cl)(CCSiMe₃) (1) {[Ti]=(η⁵-C₅H₅)₂Ti} with Ni(CO)₄ (2) in a 1:1 molar ratio produces the heterobimetallic early-late transition metal complex {[Ti](Cl)(CCSiMe₃)}Ni(CO) (3), which features a low-valent Ni(CO) entity stabilized by a datively bonded Cl and a η²-coordinated Me₃SiCC ligand. As side-products [Ti]Cl₂ (8) and {[Ti](CCSiMe₃)₂}Ni(CO) (5) are formed. The latter complex can also be synthesized by the reaction of [Ti](CCSiMe₃)₂ (4) with equimolar amounts of 2. If 3 is reacted with stoichiometric amounts of P(OR)₃ (6a, R=C₆H₅; 6b, R=C₆H₄CH₃-2; 6c, R=C₆H₄^tBu-2) the bis(alkynyl) titanocene 4, (CO)₂Ni[P(OR)₃]₂ (7a, R=C₆H₅; 7b, R=C₆H₄CH₃-2; 7c, R=C₆H₄^tBu-2), complex 8, {[Ti](μ,η¹:η²-CCSiMe₃)}₂ (9) along with Me₃SiCCCCSiMe₃ (10) is produced. A possible mechanism for the formation of these species is presented. The solid-state structure of 7b is reported. Complex 7b crystallizes in the tetragonalic space group P-42₁c with the following parameters: a=14.852(2), b=14.852(2), c=19.410(4) Å, V=4281.5(12) ų, Z=4 and ρ=1.271 g cm⁻³. Mononuclear 7b features a Ni(0) centre in a pseudo-tetrahedral environment, caused by the CO and P(OC₆H₄CH₃-2)₃ ligands.     

Supramolecular stabilization of the phosphite-based polyoxomolybdate [Mo6(PO3)(HPO3)3O18]

A novel phosphite-based hetero-polyoxomolybdate, [Mo₆(PO₃)(HPO₃)₃O₁₈]⁹⁻, has been isolated and structurally characterized. The most striking feature of this polyanion is the presence of peripheral phosphite groups linked to the MoO₆ octahedra. In the solid state, this cluster shows strong hydrogen bonding interactions that apparently play a key role in its stabilization and isolation from solution.     

Silica Gel Supported Chromium Trioxide: An Efficient Reagent for Oxidative Cleavage of Oximes to Carbonyl Compounds under Mild Condition

A facile, efficient oxidative deblocking of aldoximes and ketoximes to their corresponding aldehydes and ketones have been achieved by using silica gel supported chromium trioxide.