Jonathan W. Dube

A Convenient Preparative Method for Cyclic Triphosphenium Bromide and Chloride Salts

Analytically pure chloride and bromide salts of two different cyclic triphosphenium cations are prepared by the reaction of PX3 (X=Cl, Br) in the presence of the halogen-scavenging reagent cyclohexene. For the brominated species, the neutral, volatile 1,2-dibromocyclohexane byproduct is readily removed under reduced pressure, and the desired salts are obtained in high yield. Reactions involving phosphorus trichloride are complicated by the formation of salts containing both chloride and hydrogen dichloride anions. Reactivity experiments on potential undesired halogenated diphosphine byproducts suggest that the formation of such species can be prevented by increasing the concentration of cyclohexene employed in the reaction.

Accessing the Coordination Chemistry of Phosphorus(I) Zwitterions

Go for the gold! Incorporating a borate anion into the backbone of a triphosphenium cation produces a unique zwitterionic phosphanide that can coordinate to one or two {AuCl} fragments depending on the steric bulk of the ligand (see picture; Au yellow, P purple, Cl green). Computational investigations show that in this μ-type ligand, the phosphorus atom behaves only as a σ,π donor.

Reversible, Photoinduced Activation of P4 by Low‐Coordinate Main Group Compounds

Two unique systems based on low-coordinate main group elements that activate P4 are shown to quantitatively release the phosphorus cage upon short exposure to UV light. This reactivity marks the first reversible reactivity of P4, and the germanium system can be cycled 5 times without appreciable loss in activity. Theoretical calculations reveal that the LUMO is antibonding with respect to the main group element-phosphorus bonds and bonding with respect to reforming the P4 tetrahedron, providing a rationale for this unprecedented activity, and suggesting that the process is tunable based on the substituents.

Homoleptic pnictogen-chalcogen coordination complexes.

The synthesis and structural characterization of dicationic selenium and tellurium analogues of the carbodiphosphorane and triphosphenium families of compounds are reported. These complexes, [Ch(dppe)][OTf](2) [Ch = Se, Te; dppe = 1,2-bis(diphenylphosphino)ethane; OTf = trifluoromethanesulfonate], are formed using [Ch](2+) reagents via a ligand-exchange protocol and represent extremely rare examples of homoleptic pnictogen → chalcogen coordination complexes. The corresponding arsenic compounds were also prepared, [Ch(dpAse)][OTf](2) [Ch = Se, Te; dpAse = 1,2-bis(diphenylarsino)ethane], exhibiting the first instance of an arsenic → chalcogen dative bond. The electronic structures of these unique compounds were determined and compared to previously reported chalcogen dications.

Synthesis of Zwitterionic Triphosphenium Transition Metal Complexes: A Boron Atom Makes The Difference

A collection of zwitterionic phosphanide metal carbonyl coordination complexes has been synthesized and fully characterized, representing the first isolated series of metal complexes for the triphosphenium family of compounds. The dicoordinate phosphorus atom of the zwitterion is formally in the +1 oxidation state and can coordinate to one metal, 2M (M = Cr, Mo, W) and 2Fe, or two metals, a Co2(CO)6 fragment 4, depending on the starting reagents. All complexes have been isolated in greater than 80% yield, and structures were confirmed crystallographically. Metrical parameters are consistent with 1 being a weak donor and results in long metal-phosphorus bonds being observed in all cases. Unique bimetallic structures, 3M (M = Cr, Mo, W), consisting of a M(CO)5 fragment on phosphorus and a piano-stool M(CO)3 fragment on a boron phenyl group have been identified in the (31)P{(1)H} NMR spectra and confirmed using X-ray diffraction studies. Use of the borate backbone in 1, which renders the molecule zwitterionic, proves to be a determining factor in whether these metal complexes will form; the halide salt of a cationic triphosphenium ion, 6[Br], shows no evidence for formation of the analogous metal complexes by (31)P{(1)H} NMR spectroscopy, and tetraphenylborate salts, 6[BPh4] and 7[BPh4], produce complexes that are unstable.

Photoinduced Carbene Generation from Diazirine Modified Task Specific Phosphonium Salts To Prepare Robust Hydrophobic Coatings

3-Aryl-3-(trifluormethyl)diazirine functionalized highly fluorinated phosphonium salts (HFPS) were synthesized, characterized, and utilized as photoinduced carbene precursors for covalent attachment of the HFPS onto cotton/paper to impart hydrophobicity to these surfaces. Irradiation of cotton and paper, as proof of concept substrates, treated with the diazirine-HFPS leads to robust hydrophobic cotton and paper surfaces with antiwetting properties, whereas the corresponding control samples absorb water readily. The contact angles of water were determined to be 139° and 137° for cotton and paper, respectively. In contrast, water placed on the untreated or the control samples (those treated with the diazirine-HFPS but not irradiated) is simply absorbed into the surface. Additionaly, the chemically grafted hydrophobic coating showed high durability toward wash cycles and sonication in organic solvents. Because of the mode of activation to covalently tether the hydrophobic coating, it is amenable to photopatterning, which was demonstrated macroscopically.