Assessment of floodplain vulnerability during extreme Mississippi River flood 2011.

Regional change in the variability and magnitude of flooding could be a major consequence of future global climate change. Extreme floods have the capacity to rapidly transform landscapes and expose landscape vulnerabilities through highly variable spatial patterns of inundation, erosion, and deposition. We use the historic activation of the Birds Point-New Madrid Floodway during the Mississippi and Ohio River Flooding of 2011 as a scientifically unique stress experiment to analyze indicators of floodplain vulnerability.

Biologically relevant phosphoranes: synthesis and structural characterization of glucofuranose-derived phosphoranes with penta- and hexacoordination at phosphorus.

Carbohydrate-based phosphoranes were synthesized by reacting the appropriate diphenol with phosphorus trichloride followed by the addition of chloralose to form 1 and by the addition of isopropylidene-D-glucofuranose to form 2 and 3. Phosphorane 4 was obtained by reacting 1,2-O-isopropylidene-alpha-D-glucofuranosyl-3,5,6-phosphite (13) with a diphenol. For the synthesis of 5-9, the appropriate phosphite was reacted with isopropylidene-glucofuranose.

Biologically relevant phosphoranes: structural characterization of glucofuranose- and xylofuranose-based phosphoranes.

Carbohydrate-based phosphoranes were synthesized by reacting 2,2'-ethylidenebis(4,6-di-tert-butylphenyl)fluorophosphite with 1,2-O-isopropylidene-alpha-D-glucofuranose, beta-chloralose, and 1,2-isopropylidene-alpha-D-xylofuranose to form the monocyclic biophosphoranes 1-3, respectively, in the presence of N-chlorodiisopropylamine. Synthesis of the monocyclic biophosphorane 4 was achieved by reacting tris(2,6-di-isopropylphenyl)phosphite with 1,2-O-isopropylidene-alpha-D-glucofuranose in the presence of N-chlorodiisopropylamine. X-ray analysis of 1-4 revealed trigonal bipyramidal structures with the carbohydrate components occupying axial-equatorial sites.

Biologically relevant phosphoranes: structural characterization of a nucleotidyl phosphorane.

The first successful crystal structures of biorelevant nucleoside and carbohydrate-based phosphoranes are reported. Employing thymidine, a nucleotidyl phosphorane was synthesized in 90% yield and was shown by X-ray analysis to possess a trigonal bipyramidal geometry. With the use of 1,2-O-isopropylidene-alpha-d-glucofuranose, a carbohydrate-based phosphorane was formed and similarly found to have a trigonal bipyramidal geometry.

Phosphorus-nitrogen donor interaction leading to atrane formation in phosphate and oxyphosphorane compositions. Implications for phosphoryl transfer enzymes(1).

Reaction of aminotriphenols, tris(2-hydroxy-3,5-dimethylbenzyl)amine (E) and tris(2- hydroxy-3-tert-butyl-5-methylbenzyl)amine (F), with triphenylphosphite, tris(p-methoxyphenyl)phosphite, or phenyldiphenoxyphosphane in the presence of N-chlorodiisopropylamine led to the isolation of tetraoxyphosphorane 1, pentaoxyphosphorane 3, phosphate-atrane 2, hexacoordinated pentaoxyphosphorane-atrane 4, and the first hexacoordinated tetraoxyphosphorane-atrane 5. X-ray analysis of 1-3 and 5 were obtained. NMR data is reported and supports that the atrane 4 has the same hexacoordinated structure as 5.

Phosphoryl transfer enzymes and hypervalent phosphorus chemistry.

The coordination tendencies of phosphorus to form a hexacoordinated state from a pentacoordinated state, which might assist in describing the mechanistic action of phosphoryl transfer enzymes, are delineated. The factors discussed include substrate and transition or intermediate state anionicity, hydrogen bonding, packing effects, that is, van der Waals forces, the ease of formation of hexacoordinate phosphorus from lower coordinate states, and the pseudorotation problem common to nonrigid pentacoordinate phosphorus. In view of the work reported in this Account and recent work on enzyme promiscuity and moonlighting activities, it is suggested that donor action should play a role in determining active site interactions in phosphoryl transfer enzyme mechanisms.

Influence of hydrogen bonding in competition with lattice interactions on carbonyl coordination at phosphorus. Implications for phosphoryl transfer activated states.

A series of phosphorus compounds containing carboxyl groups that serve as mimics for amino acid residues was synthesized. The series was composed of the phosphonium salts 1A, 1B, and 2, the anionic phosphines 3A and 3B, and the anionic phosphine oxide 4. X-ray structural analysis revealed that P-O coordination occurred in the presence of extensive hydrogen bonding and led to pseudo or regular trigonal bipyramidal geometries.

Pseudoheptacoordination and pseudohexacoordination in tris(2-N,N-dimethylbenzylamino)phosphane.

The phosphane (C(6)H(4)-2-CH(2)NMe(2))(3)P (1) upon recrystallization from various solvents yielded the structurally different forms 1A, 1C, 1B(1), and 1B(2). Phosphane oxide (C(6)H(4)-2-CH(2)NOMe(2))(3)PO (2) was obtained from 1 by oxidation with hydrogen peroxide. X-ray analysis provided molecular structures for 1A, 1B(1), 1B(2), and 2.

Conversion of tricoordinate to hexacoordinate phosphorus. Formation of a phosphorane-phosphatrane system.

Reaction of RPCl(2) with tris(2-hydroxy-3-tert-butyl-5-methylbenzyl)amine (4) led to the formation of a tricoordinated phosphonite (1) when R = Ph and to a hexacoordinated phosphorane-phosphatrane (2) when R = Et. The X-ray structures showed that the unreacted hydroxyl group in 1 oxidatively added to phosphorus in 2 leading to the formation of three additional bonds, a P[bond]O, a P[bond]H, and a P[bond]N linkage. In solution, (31)P measurements assisted by solid-state (31)P measurements revealed that each of the compounds existed in both structural forms.

P-O donor action from carboxylate anions with phosphorus in the presence of hydrogen bonding. A model for phosphoryl-transfer enzymes.

A series of phosphorus compounds (1-3) containing anionic carboxylate groups were synthesized by treatment of the respective neutral precursor acid forms B-D with amines, which also served to introduce hydrogen-bonding interactions. The compounds, subjected to X-ray structure analysis, resulted in hexacoordinated anionic phosphoranates 1A and 1B, a pseudo-trigonal-bipyramidal anionic phosphine (2), and a trigonal-bipyramidal anionic phosphine oxide (3). The structures revealed that P-O donor coordination was present in all members of the anionic series 1-3 and resulted in stronger interactions than existed in the precursor neutral acid forms B-D as measured by the presence of shorter P-O distances.

Chloro- and Fluoro-Substituted Phosphites, Phosphates, and Phosphoranes Exhibiting Sulfur and Oxygen Coordination(1).

New cyclic phosphoranes, O(2)S[Me(t-Bu)C(6)H(2)O](2)PCl(3) (1), O(2)S[Me(t-Bu)C(6)H(2)O](2)P(OC(6)H(4)-m-CF(3))(3) (2), and O(2)S[(t-Bu)(2)C(6)H(2)O](2)PCl(3) (3), containing sulfone donor groups and halogen substituents were synthesized by oxidative addition reactions of a diol with a tricoordinated phosphorus precursor. Cyclic phosphates, O(2)S[(t-Bu)(2)C(6)H(2)O](2)P(O)Cl (4) and O(2)S[Me(t-Bu)C(6)H(2)O](2)P(O)(OC(6)H(4)-m-CF(3)) (5), resulted from hydrolysis reactions of 3 and 2, respectively. Phosphate O(2)S[Me(t-Bu)C(6)H(2)O](2)P(O)(OC(6)F(5)) (6) was prepared from a known phosphorane precursor and independently from the reaction of an N-oxide molecule with a parent phosphite, O(2)S[Me(t-Bu)C(6)H(2)O](2)P(OC(6)F(5)).

Cyclic Three-, Four-, Five-, and Six-Coordinate Nitrogen-Containing Phosphorus Compounds Varying in Ring Size from Five- to Ten-Membered. P-N Donor Action(1).

New nitrogen-containing phosphorus compounds 1 and 3-5 were prepared by the reaction of a nitrogen-containing phenol with PhPCl(2). Hydrolysis of 1 gave an acyclic anionic phosphinate hydrogen bonded to an ammonium component (2). Use of a nitrogen-containing diol with P(OPh)(3) resulted in oxidative addition to give hexacoordinate pentaoxyphosphorus compound 6 exhibiting P-N donor action.

Molecular Structures of Three-, Four-, and Five-Coordinate Phosphorus Compounds Containing Salicylate Ligands(1).

The new cyclic compound 2,2'-sulfurylbis(4-methyl-6-tert-butylphenyl) methyl 2-benzoate phosphite, O(2)S[(t-Bu)MeC(6)H(4)O](2)(OC(6)H(4)CO(2)Me)P (3), containing a salicylate ligand was synthesized from 2,2'-sulfurylbis(4-methyl-6-tert-butylphenyl) chlorophosphite and methyl salicylate in the presence of triethylamine in ether solution. X-ray analyses of bis(methyl salicylate-O)phenylphosphine, (OC(6)H(4)CO(2)Me)(2)PPh (1), and bis(methylsalicylato-O)phenyl(tetrachlorophenylene-1,2-dioxy)phosphorane, (O(2)C(6)Cl(4))(OC(6)H(4)CO(2)Me)(2)PPh (2), as well as that for 3 were obtained. The phosphane 1 has a pseudo trigonal bipyramidal (TBP) structure due to coordination of a carbonyl oxygen atom at an axial site.

Increased Coordination via Sulfur Donor Action in Cyclic Pentaoxyphosphoranes and the Parent Cyclic Phosphite. Influence of Pentafluorophenoxy Ligands(1).

The pentafluorophenoxy ligand was introduced into the new cyclic pentaoxyphosphoranes S[(t-Bu)MeC(6)H(2)O](2)P(OC(6)F(5))(O(2)C(6)Cl(4)) (1), S[(t-Bu)MeC(6)H(2)O](2)P(OC(6)F(5))(O(2)C(14)H(8)) (2), and S[(t-Bu)MeC(6)H(2)O](2)P(OC(6)F(5))(3) (3). X-ray analysis revealed hexacoordinate structures formed by sulfur donor action present as a bridging atom in flexible eight-membered rings for 1-3. X-ray analysis showed that sulfur coordination also occurred with the same type of ring system as part of the phosphite S[(t-Bu)MeC(6)H(2)O](2)P(OC(6)F(5)) (4) to give a pseudo-trigonal-bipyramidal geometry.

Structure-Reactivity Relationships for Associative Displacement Reactions of Penta- and Hexacoordinate Cyclic Oxyphosphoranes with Catechols(1)(,)(2).

The reactivity of a series of cyclic pentaoxyphosphoranes containing a sulfonyl group was carried out, O(2)S[(t-Bu)MeC(6)H(2)O](2)P(OCH(2)CF(3))(3) (1), O(2)S[(t-Bu)MeC(6)H(2)O](2)P(OPh)(3) (2), O(2)S[(t-Bu)(2)C(6)H(2)O](2)P(OCH(2)CF(3))(3) (4), and O(2)S[(t-Bu)(2)C(6)H(2)O](2)P(OPh)(3) (5). Also included were derivatives containing sulfur, S[(t-Bu)MeC(6)H(2)O](2)P(OPh)(3) (6) and S[(t-Bu)(2)C(6)H(2)O](2)P(OPh)(3) (8), and the methylene group, CH(2)[(t-Bu)MeC(6)H(2)O](2)P(OPh)(3) (7), in place of the sulfonyl group in the ring-containing component. (31)P NMR monitoring of the reactions of the oxyphosphoranes with catechol and 4-nitrocatechol shows the following order of reactivity: 7 > 8 > 6 > 2 > 5 >> 1.

Conformational Preference and Donor Atom Interaction Leading to Hexacoordination vs Pentacoordination in Bicyclic Tetraoxyphosphoranes(1).

New bicyclic tetraoxyphosphoranes all containing a six-membered oxaphosphorinane ring, C(6)H(8)(CH(2)O)(2)P(OC(12)H(8))(OXyl) (1), (C(6)H(4)O)(2)P(OC(12)H(8))(OXyl) (2), CH(2)[(t-Bu)(2)C(6)H(2)O](2)P(OC(12)H(8))(OXyl) (3), O(2)S[(t-Bu)MeC(6)H(2)O](2)P(OC(12)H(8))(OXyl) (4), and S[(t-Bu)MeC(6)H(2)O](2)P(OC(12)H(8))(OXyl) (5), were synthesized by the oxidative addition reaction of the cyclic phosphine P(OC(12)H(8))(OXyl) (6) with an appropriate diol in the presence of N-chlorodiisopropylamine. X-ray analysis revealed trigonal bipyramidal (TBP) geometries for 1-4 where the dioxa ring varied in size from six- to eight-membered. With a sulfur donor atom as part of an eight-membered ring in place of a potential oxygen donor atom of a sulfone group as in 4, the X-ray study of 5 showed the formation of a hexacoordinated structure via a P-S interaction.

Hexacoordination via Sulfur Donor Action in Bicyclic Pentaoxyphosphoranes(1).

New bicyclic oxyphosphoranes, S[(t-Bu)MeC(6)H(2)O](2)P(OC(6)H(5))(O(2)C(6)H(3)F) (1) and S[(t-Bu)MeC(6)H(2)O](2)P(OC(6)H(5))(O(2)C(6)H(4)) (3), were synthesized by displacement reactions of a monocyclic pentaoxyphosphorane by a diol, and S[(t-Bu)(2)C(6)H(2)O](2)P(OCH(2)CF(3))(O(2)C(6)Cl(4)) (2) and S[(t-Bu)(2)C(6)H(2)O](2)P(C(6)H(5))(O(2)C(6)Cl(4)) (4), by oxidative addition reactions of a phosphite or phosphine with tetrachlorobenzoquinone. X-ray studies revealed hexacoordinated structures formed by the presence of a sulfur donor atom incorporated in a flexible eight-membered ring. The structures were displaced along a coordinate from a square pyramid toward an octahedron.

Axial Site Occupancy by the Least Electronegative Ligands in Trigonal Bipyramidal Tetraoxyphosphoranes(1).

Analogous to the formation of CH(2)[(t-Bu)(2)C(6)H(2)O](2)P(Ph)(O(2)C(6)Cl(4)) (1), the new bicyclic tetraoxyphosphoranes CH(2)[(t-Bu)(2)C(6)H(2)O](2)P(Et)(O(2)C(6)Cl(4)) (3) and CH(2)[ClC(6)H(3)O](2)P(Ph)(O(2)C(6)Cl(4)) (4) were synthesized by the oxidative addition of the appropriate cyclic phosphines with o-tetrachlorobenzoquinone. For the formation of CH(2)[(t-Bu)(2)C(6)H(2)O](2)P(Ph)(O(2)C(2)Ph(2)) (2), a similar reaction was followed with the use of benzil (PhCOCOPh) in place of o-tetrachlorobenzoquinone. X-ray analysis of 1-3 revealed trigonal bipyramidal geometries and provided evidence for the first series of complexes in the absence of ring strain in which the least electronegative group, ethyl or phenyl, is located in an axial position, in violation of the electronegativity rule.

Synthesis and Molecular Structures of Pyridine-Containing Large-Membered Cyclic Bis(alkoxy)silanes(1).

The new cyclic silanes [(C(5)H(3)N)(CH(2)O)(2)SiMe(2)](2) (1) and (C(5)H(3)N)(CH(2)CPh(2)O)(2)SiMe(2) (2) containing 16-membered and 10-membered rings, respectively, were prepared by the condensation reaction of Me(2)SiCl(2) with an appropriate pyridine diol in the presence of Et(3)N. X-ray studies show that the dimeric formulation for 1 represents a tetracoordinate cyclic silane, whereas 2 has a geometry halfway from a tetrahedron toward a trigonal bipyramid (TBP) as a result of Si-N(ax) donor action. (29)Si and (1)H NMR indicate retention of the coordination geometry for 2 in solution that undergoes rapid Si-N cleavage and ring rearrangement.