The development of group 15 Lewis acids is an area of active investigation that has led to numerous advances in anion sensing and catalysis. While phosphorus has drawn considerable attention, emerging research shows that organoantimony(III) reagents may also act as potent Lewis acids. Comparison of the properties of SbPh , Sb(C F ) , and SbAr with those of their tetrachlorocatecholate analogues SbPh Cat, Sb(C F ) Cat, and SbAr Cat (Cat=o-O C Cl , Ar =3,5-(CF ) C H ) demonstrates that the Lewis acidity of electron deficient organoantimony(III) reagents can be readily enhanced by oxidation to the +V state-as verified by binding studies, organic reaction catalysis, and computational studies. The results are rationalized by explaining that oxidation of the antimony center leads to a lowering of the accepting σ* orbital and a deeper carving of the associated σ-hole.

A niobium-based method for thermal transfer of P 2 to 1,3-dienes has been described previously, but this sole extant method is of limited preparative value due to the multi-step nature of the synthesis.[1] In order to make the interesting class of bi-or tetracyclic P 2 R 4 molecules readily available for detailed scrutiny, we sought and have now discovered a simple one-step procedure, reported herein. The method consists of P 4 photolysis in the presence of commercially available 1,3-diene molecules to produce directly the diphosphane target molecules.In 1937, Rathenau reported that the conversion of white phosphorus to red phosphorus under UV irradiation using a mercury lamp involves unimolecular dissociation of P 4 into P 2 molecules, followed by recombination of the latter into red phosphorus.[2] In one report on the P 4 cophotolysis with metal carbonyl complexes, Dahl et al. mention that "P 4 in solution photolyzes readily to P 2 at ambient temperatures".[3] There have been several other reports on the co-photolysis of P 4 with metal carbonyl complexes and generation of metalphosphorus products,[4] yet we have not found any reports on using photolysis of P 4 molecules for the direct inclusion of phosphorus atoms into organic substrates. [5] Electronic absorption features for P 4 in the gas phase at 62 8C have been reported in the UV region below 300 nm. [6] We found that upon using a mercury lamp that irradiates predominantly at 254 nm, the photolysis of P 4 in the presence of 1,3-dienes affords products consistent with double DielsAlder additions of diene molecules to P 2 units.Initial experiments focused on generating the previously reported [1] tetracyclic diphosphane C 12 H 16 P 2 by irradiating a mixture of P 4 and 1,3-cyclohexadiene (CHD). The appearance of the characteristic sharp singlet of the targeted diphosphane product at d = À80 ppm in 31 P NMR spectra of crude product mixtures was encouraging. However, upon attempting to quantify and isolate the desired diphosphane, only quantities on the order of several milligrams were obtained. Nevertheless, when 1,3-cyclohexadiene was replaced with conjugated dienes that are more transparent in the window of P 4 absorption, improved results were obtained. [7]

The stereoselective synthesis of a family of cis-macrocyclic diphosphines was achieved in only three steps from white phosphorus and commercial materials. These new ligands showed activity in the nickel-catalyzed coupling of CO2 and ethylene.

Thermodynamic, kinetic, and computational studies are reported for oxygen atom transfer (OAT) to the complex V(N[t-Bu]Ar)3 (Ar = 3,5-C6H3Me2, 1) from compounds containing N-O bonds with a range of BDEs spanning nearly 100 kcal mol(-1): PhNO (108) > SIPr/MesCNO (75) > PyO (63) > IPr/N2O (62) > MesCNO (53) > N2O (40) > dbabhNO (10) (Mes = mesityl; SIPr = 1,3-bis(diisopropyl)phenylimidazolin-2-ylidene; Py = pyridine; IPr = 1,3-bis(diisopropyl)phenylimidazol-2-ylidene; dbabh = 2,3:5,6-dibenzo-7-azabicyclo[2.2.1]hepta-2,5-diene). Stopped flow kinetic studies of the OAT reactions show a range of kinetic behavior influenced by both the mode and strength of coordination of the O donor and its ease of atom transfer. Four categories of kinetic behavior are observed depending upon the magnitudes of the rate constants involved: (I) dinuclear OAT following an overall third order rate law (N2O); (II) formation of stable oxidant-bound complexes followed by OAT in a separate step (PyO and PhNO); (III) transient formation and decay of metastable oxidant-bound intermediates on the same time scale as OAT (SIPr/MesCNO and IPr/N2O); (IV) steady-state kinetics in which no detectable intermediates are observed (dbabhNO and MesCNO). Thermochemical studies of OAT to 1 show that the V-O bond in O≡V(N[t-Bu]Ar)3 is strong (BDE = 154 ± 3 kcal mol(-1)) compared with all the N-O bonds cleaved. In contrast, measurement of the N-O bond in dbabhNO show it to be especially weak (BDE = 10 ± 3 kcal mol(-1)) and that dissociation of dbabhNO to anthracene, N2, and a (3)O atom is thermodynamically favorable at room temperature. Comparison of the OAT of adducts of N2O and MesCNO to the bulky complex 1 show a faster rate than in the case of free N2O or MesCNO despite increased steric hindrance of the adducts.

Herein we report the finding that molybdate absorbs not just one but two equivalents of CO2 (the second, reversibly) together with complete characterization including single-crystal X-ray diffraction studies of the resulting mono- and dicarbonate complexes.

Lewis acidic fluorinated organoantimony(v) derivatives have been combined with phosphines for the complexation and colourimetric sensing of formaldehyde in biphasic water/CH2Cl2 mixtures.

The binding of amphiphilic molecules to lipid bilayers is followed by 19F NMR using chemical shift and line shape differences between the solution and membrane-tethered states of -CF 3 and -CHF 2 groups. A chemical shift separation of 1.6 ppm combined with a high natural abundance and high sensitivity of 19F nuclei offers an advantage of using 19F NMR spectroscopy as an efficient tool for rapid time-resolved screening of pharmaceuticals for membrane binding. We illustrate the approach with molecules containing both fluorinated tails and an acrylate moiety, resolving the signals of molecules in solution from those bound to synthetic dimyristoylphosphatidylcholine bilayers both with and without magic angle sample spinning. The potential in vitro and in vivo biomedical applications are outlined. The presented method is applicable with the conventional NMR equipment, magnetic fields of several Tesla, stationary samples, and natural abundance isotopes.

The Nb-P triple bond in [P≡Nb(N[Np]Ar)(3)](-) (Np = CH(2)(t)Bu; Ar = 3,5-Me(2)C(6)H(3)) has produced the first case of P(4) activation by a metal-ligand multiple bond. Treatment of P(4) with the sodium salt of the niobium phosphide complex in weakly coordinating solvents led to formation of the cyclo-P(3) anion [(P(3))Nb(N[Np]Ar)(3)](-). Treatment in tetrahydrofuran (THF) led to the formation of a cyclo-P(5) anion [(Ar[Np]N)(η(4)-P(5))Nb(N[Np]Ar)(2)](-), which represents a rare example of a substituted pentaphosphacyclopentadienyl ligand. The P(4) activation pathway was shown to depend on the dimer-monomer equilibrium of the niobium phosphide reagent, which, in turn, depends on the solvent used for the reaction. The pathway leading to the cyclo-P(3) product was shown to require a 2:1 ratio of the phosphide anion to P(4), while the cyclo-P(5) formation requires a 1:1 ratio. The cyclo-P(3) salt has been isolated in 56% yield as orange crystals of the [Na(THF)](2)[(P(3))Nb(N[Np]Ar)(3)](2) dimer or in 83% yield as an orange powder of [Na(12-crown-4)(2)][(P(3))Nb(N[Np]Ar)(3)]. A solid-state X-ray diffraction experiment on the former salt revealed that each Nb-P(3) unit exhibits pseudo-C(3) symmetry, while (31)P NMR spectroscopy showed a sharp signal at -223 ppm that splits into a doublet-triplet pair below -50 °C. It was demonstrated that this salt can serve as a P(3)(3-) source upon treatment with AsCl(3), albeit with modest yield of AsP(3). The cyclo-P(5) salt was isolated in 71% yield and structurally characterized from red crystals of [Na(THF)(6)][(Ar[Np]N)(η(4)-P(5))Nb(N[Np]Ar)(2)]. The anion in this salt can be interpreted as the product of trapping of an intermediate pentaphosphacycplopentadienyl structure through migration of one anilide ligand onto the P(5) ring. The W(CO)(5)-capped cyclo-P(3) salt was also isolated in 60% yield as [Na(THF)][(OC)(5)W(P(3))Nb(N[Np]Ar)(3)] from the activation of 0.5 equiv of P(4) with the sodium salt of the tungsten pentacarbonyl adduct of the niobium phosphide anion.