Unexpected formation of ansa isomers enabled by phosphazene ring flexibility in the reactions of cyclotetraphosphazene with 1,2-ethanediol.

In this work, the nucleophilic substitution reactions of the cyclotetraphosphazene, tetramer, (1) (N4P4Cl8) with the disodium salt of 1,2-ethanediol in THF solution at different mole ratios were demonstrated. Surprisingly, one double bridged (2) and three ansa derivatives [bis (3), tris (4) and tetrakis (5)] were formed demonstrating two competing pathways in these reactions. The new type cyclotetraphosphazene compounds (2-5) consisting of multiple rings were characterized by elemental analysis, mass spectrometry, 1H and 31P NMR spectroscopy and X-Ray crystallography. Although 1,2-ethanediol, a short chain diol, can only produce spiro type products with cyclotriphosphazene, (N3P3Cl6), it was able to give ansa type products with cyclotetraphosphazene which suggests the role of the ring flexibility of 1. Crystallographic evidence shows the distortion of the cyclotetraphosphazene ring.

Regiochemical Control in the Substitution Reactions of Cyclotriphosphazene Derivatives with Secondary Amines.

The substitution reactions of the monospiro and geminally disubstituted cyclotriphosphazene derivatives N3P3Cl4R2 (R2 = OCH2(CF2)2CH2O (1a), SPh (1b), OCH2CH2CH2O (1c), NHPh (1d), OCH2CH2CH2NH (1e), NHBut (1f)) with two secondary amines (pyrrolidine and dimethylamine) were carried out to investigate geminal or non-geminal directing effects in mixed substituent cyclophosphazenes. The relative amounts of isomeric products, geminal and non-geminal trans or cis, was established quantitatively from the 31P NMR spectra of the reaction mixtures. Although secondary amines generally follow a non-geminal pathway in the reactions with hexachlorocyclotriphosphazene, in this work, the reactions of two different secondary amines with some N3P3Cl4R2 (R2 = OCH2CH2CH2NH, NHPh, NHBut) derivatives lead to the formation of geminal products. We have shown that this observation depends on the electron-donating properties of the PR2 groups. Isolated compounds were analyzed by standard techniques such as elemental analysis, mass spectrometry, and 1H and 31P NMR spectroscopy. The structures of compounds for which suitable crystals could be obtained were characterized by X-ray crystallography.

New Synthetic Approach to Molecular Rods Using Cyclophosphazene-Based Oligospiranes.

A synthetic approach was developed to prepare a new type of highly functionalized inorganic-organic heterocyclic molecular rod (3a and 3b) consisting of cyclophosphazene and carbocyclic units. Single-crystal X-ray diffraction analysis of 3a revealed that the molecular length was ca. 2.5 nm. The products of this high-yield process have the potential for derivatization via known phosphazene reactions.

Unexpected Ring Expansion of a Four-Membered Cyclophosphazane.

Nucleophilic substitution reactions of the N(R),N(R)-spiro-bridged octachlorobis(cyclotriphosphazene), N3P3Cl4[N(CH2)5CH3]2N3P3Cl4 (1), with sodium salts of alcohols (1,3-propanediol, 2,2,3,3,4,4-hexafluoro-1,5-pentanediol, and phenol) give ansa products (2-4) via an unexpected rearrangement. These products were characterized by elemental analysis, mass spectrometry, and (1)H and (31)P NMR spectroscopy. The molecular structures of compounds 3 and 4 were also established by X-ray crystallography. This new class of phosphazene structures consists of three fused P3N3 rings that arise from expansion of the four-membered phosphazane ring in 1 to a six-membered N3P3 ring during alcoholysis reactions.

The mechanism of a phosphazene-phosphazane rearrangement.

The phosphazene-phosphazane rearrangement of N3P3Cl5O(CH2)2OC(=O)CMe=CH2 (8) has been examined in detail using one and two dimensional NMR ((31)P, (1)H) spectroscopy and mass spectrometry. The mixed phosphazene-phosphazane [NPCl2]2[N((CH2)2OC(=O)CMe=CH2)P(O)Cl] (14), [NPCl2]2[NHP(O)Cl] (13) and a two ring assembly [NPCl2]2[NP(O{(NPCl2)2(N((CH2)2OC(=O)CMe=CH2)P(O)}] (15) have all been detected in the product mixture. The rate of the rearrangement has been measured at five temperatures by (31)P and (1)H NMR. The reaction is first order in 8 (T1/2 at 111° is 4.65 hours). The activation enthalpy is positive and the activation entropy is negative. A mechanism involving competing intra and inter molecular processes which fits the product distribution and kinetic data has been proposed. Several other methyacrylphosphazenes were examined under the same thermolysis conditions. The rearrangement was observed and the rates obtained in cases where the (CH2)2 spacer unit of the methacrylate was replaced by linear and branched propyl units. The rearrangement was not observed when the methacrylate was appended to a spirocyclic unit, the spacer unit was extended to the n-butyl group and when the methacrylate unit was replaced by a methoxy group. These results are all consistent with the proposed mechanism. This investigation resolves conflicting results previous reported for the rearrangement.

Synthesis of a new class of fused cyclotetraphosphazene ring systems.

Octachlorocyclotetraphosphazene (1) was reacted with butylamines [n-butyl, i-butyl, sec-butyl, and t-butyl] in a 1:0.8 mol ratio in THF to obtain cyclotetraphosphazenes bearing a P-NH group, N4P4Cl7(NHR) [R = n-butyl (2a), i-butyl (2b), sec-butyl (2c), t-butyl (2d)](2a-d). The cyclotetraphosphazene derivatives 2a, 2b, and 2c were treated with sodium hydride giving rise to a new type of cyclophosphazene compounds (P8N8 ring) consisting of three fused tetramer rings (3a-c). Whereas reaction of sodium hydride with the t-butylaminocyclophosphazene derivative (2d) gave a P-O-P bridged compound (4) presumably as a result of hydrolysis reaction associated with moisture in the solvent. It is likely that the 16-membered cyclooctaphosphazene derivatives (3a-c) are formed by a proton abstraction/chloride ion elimination, intramolecular nucleophilic attack, ring opening and intermolecular condensation processes, respectively.

Reactions of alkyne- and butadiyne-derived fluorinated cyclophosphazenes with diiron and dimolybdenum carbonyls.

The reaction of (ß-phenylethynyl)pentafluorocyclotriphosphazene, [(PhC≡C)(F)PN](PNF2)2, with Fe2(CO)9 in refluxing hexane resulted in five new compounds, namely, [Fe(CO)2{η(2):η(2)-2,4-(P3N3F5)2Ph2C4Fe(CO)3}-µ-CO] (1), [Fe(CO)2{η(2):η(2)-2,5-(P3N3F5)2Ph2C4Fe(CO)3}-µ-CO] (2), [Fe(CO)2{η(5)-2,5-(P3N3F5)2Ph2C4CO}C(Ph)═C(P3N3F5)](3), [Fe(CO)3{η(2):η(2)-2,4-(P3N3F5)2Ph2C4CO] (4), and [Fe(CO)3{η(2):η(2)-2,5-(P3N3F5)2Ph2C4CO] (5). While compounds 1, 2, 4, and 5 have five-membered ferracyclopentadiene or cyclopentadienone rings coordinated to the Fe(CO)3 unit in the η(2):η(2) mode, compound 3 has a 2,5-cyclopentadienone ring attached to an Fe(CO)2(P3N3F5)C═C(Ph) unit, where Fe is η(5)-bonded to the cyclopentadienone ring, and the carbon that is α to the phenyl unit of the Fe(CO)2(P3N3F5)C═C(Ph) group is σ-bonded to the oxygen atom of the cyclopentadienone ring. Formation of five-membered cyclic compounds having two fluorophosphazene units on the vicinal carbon atoms of C4R2R'2Y rings was not observed in this reaction. No examples of Fe(CO)3-bound cyclobutadiene complexes were also isolated from this reaction. A similar reaction in the presence of trimethylamine N-oxide, NMe3O, was found to proceed at -20 °C with the formation of compounds 4 and 5 only. In contrast to the Fe2(CO)9 reaction, a reaction of alkyne-derived pentafluorocyclotriphosphazenes, [(RC≡C)(F)PN](PNF2)2 [R = Ph, Fe(C5H5)2] with the molybdenum complex Cp(CO)3Mo-Mo(CO)3Cp (Cp = cyclopentadienyl) in refluxing toluene resulted in the simple tetrahedral clusters Cp(CO)2Mo(P3N3F5)C-C(Ph)Mo(CO)2Cp (6) and Cp(CO)2Mo(P3N3F5)C-C(Fc)Mo(CO)2Cp (7) (Fc = ferrocenyl). A similar reaction of Cp(CO)3Mo-Mo(CO)3Cp with butadiyne-derived fluorophosphazenes, [(RC≡C-C≡C)(F)PN](PNF2)2 [R = Ph, Fe(C5H5)2], yielded the tetrahedral clusters Cp(CO)2Mo(P3N3F5)C-C(C≡CPh)Mo(CO)2Cp (8) and Cp(CO)2Mo(P3N3F5)C-C(C≡CFc)Mo(CO)2Cp (9) with the tetrahedral Mo2C2 unit forming exclusively with the alkyne unit of the butadiyne group bound to the cyclophosphazene ring. The crystal structures and infrared spectral data of these molybdenum clusters showed the presence of a semibridging carbonyl on one of the molybdenum units. All new compounds were characterized by IR, NMR [(1)H, (13)C{(1)H}, (31)P{(1)H}, and (19)F{(1)H}] and high-resolution mass spectrometry studies. Compounds 2, 3, 5, and 7-9 were also structurally characterized using single-crystal X-ray diffraction studies.

Organophosphazenes. 26. Factors controlling the pathways observed in the reactions of ethynyl lithium reagents with hexafluorocyclotriphosphazene.

In contrast to previously studied reactions of ethynyl lithium reagents, the reactions of propynyl and hexynyl lithium with N(3)P(3)F(6) lead to predominantly nongeminal isomers. A modest cis stereo selectivity was observed. The sequential addition of a lithio acetylene reagent which follows a predominately geminal pathway (lithiophenylacetylene) and an aryl lithium reagent (p-propenylphenyl lithium) which follows a predominantly nongeminal pathway were examined. The relative order of addition of the two reagents was interchanged, resulting in a change of reaction pathway demonstrating ring substituent control of the regio and stereo chemical pathways. Hydrogenation of the ethynyl unit in the phosphazene derivatives provides a facile pathway to the difficult to prepare alkylphosphazenes. The chemical shift of the organosubstituted phosphorus center undergoes a remarkably large change (46-47 ppm) on going from the ethynyl to the alkyl derivatives, which reduces the complex (31)P and (19)F NMR spectra of the ethynyl derivatives to easily interpretable first-order spectra, thus allowing for structure assignment. The (13)C NMR data shows that nongeminal regio selectivity increases with the amount of s character on the ethynyl carbon atom attached to the phosphorus center. These observations allow for an understanding of the factors controlling regio and stereo chemical control in the reactions of carbanionic nucleophiles with N(3)P(3)F(6).

Stereodirective effects in mixed substituent vinyloxycyclotriphosphazenes.

Reaction pathways leading to the new mixed substituent cyclophosphazenes, N(3)P(3)Cl(4)(OCH=CH(2))(OCH(2)CF(3)) and N(3)P(3)Cl(3)(OCH=CH(2))(OCH(2)CF(3))(2), have been explored. Examination of the relative isomeric yields and the spectroscopic properties of these new derivatives gave insight into the mechanism of substitution of cyclophosphazenes with oxyanions. The syntheses of the mixtures of compounds were carried out by two different synthetic pathways. The nucleophilic substitution reaction involves either the vinyloxy ((-)OCH=CH(2)) or the trifluoroethoxy ((-)OCH(2)CF(3)) ion. Either oxyanion could be reacted with the phosphazene first to be followed by the other oxyanion. A comparison of the observed pathways shows the stereoselectivity is controlled by the ring substituent with trifluoroethoxy species favoring trans substitution and the vinyloxy species favoring increased cis substitution. Density Functional Theory and NMR ((13)C, (31)P) studies show the electronic relationships between the exocyclic group and the cyclophosphazenes including transmission of electronic information throughout the phosphazene ring.

Ride Safe: a child passenger safety program for American Indian/Alaska Native children.

BACKGROUND: In American Indian/Alaska Native (AI/AN) communities, child safety seat (CSS) use rates are much lower than in non-native communities. To reduce this disparity, Indian Health Service (IHS) staff developed, pilot-tested, and implemented Ride Safe, which provided education, training, and child safety seats for children aged 3-5 participating in Tribal Head Start Centers. METHODS: Focus groups, key informant interviews, and technical review guided program development and implementation. Progress reports and child safety seat use observations, conducted at the beginning and end of three program years (Fall 2003 to Spring 2006), assessed program reach and impact. To examine CSS use, we used three multiple logistic regressions, including a conservative intent to treat analysis. RESULTS: Ride Safe reached approximately 3,500 children and their families at 14 sites in six states, providing over 1,700 parents/family members with educational activities, 2,916 child safety seats, and child passenger safety (CPS) technician certification training for 78 Tribal staff. Children were 2.5 times (OR = 2.55, p < .01) as likely to be observed in child safety seats comparing Rounds 1 and 2 data, with the most conservative model showing that the odds of being observed restrained were 74% higher (OR = 1.74, p = or<.01) after implementation of the program. CONCLUSIONS: The Ride Safe Program effectively increased child safety seat use in AI/AN communities, however, observed use rates ranging from 30% to 71% remain well below the 2006 all US rate of 93%. Results from CSS educational and distribution/installation programs such as Ride Safe should be considered in light of the need to increase distribution programs and enhance enforcement activities in AI/AN communities, thereby reducing the disparity in AI/AN motor vehicle injuries and death.

The origin of endocyclic bond length variations in disubstituted cyclotriphosphazenes.

Intraannular ring alternation in heterogeneously substituted cyclotriphosphazenes is investigated using both ab initio and density functional methods. Comparisons of the calculated geometries for N3P3X6 (X = H, F, Cl, Me, Ph) and N3P3X4Y2 (X = F, Cl; Y = Me, Ph, X, Cl) with experimental X-ray data establish the utility of the 6-31G* basis for use with both Hartree-Fock and the B3LYP and B3PW91 functionals. Analysis of orbitals and charges shows that the bonding is best described using a polarized bond model rather than the previous explanation of asymmetric nitrogen-lone-pair donation into the phosphorus-nitrogen bond.

N-(ferrocenylmethyl)-N-methylaminocyclotriphosphazenes.

The reactions of N-(ferrocenylmethyl)-N-methylamine, C(5)H(5)FeC(5)H(4)CH(2)(Me)NH, with hexachlorocyclotriphosphazene, N(3)P(3)Cl(6), led to the formation of the N-(ferrocenylmethyl)-N-methylaminocyclotriphosphazene derivatives, N(3)(-)P(3)Cl(6-n)[N(Me)CH(2)C(5)H(4)FeC(5)H(5)](n) (n = 1-3). Only small amounts of higher degrees of substitution could be detected. In the case of the disubstituted products, the ratio of isomers was dependent on the polarity of the solvent. In nonpolar solvents the ratio was trans > geminal > cis while in acetonitrile only equal amounts of trans and cis isomers were observed. The reaction of N-(ferrocenylmethyl)-N-methylamine with (methacryloylbutenedioxy)pentachlorocyclotriphosphazene, N(3)P(3)Cl(5)O(CH(2))(4)OC(O)C(Me)=CH(2), gives the surprising geminal isomer 2,2-N(3)P(3)Cl(4)[O(CH(2))(4)OC(O)C(Me)=CH(2)]N(Me)CH(2)C(5)H(4)FeC(5)H(5) and the tris derivative 2,2',4-N(3)P(3)Cl(3)[O(CH(2))(4)OC(O)C(Me)=CH(2)][N(Me)CH(2)C(5)H(4)FeC(5)H(5)](2). All of the phosphazene derivatives were characterized by elemental analyses, mass spectrometry, IR and NMR ((1)H, (13)C, (31)P) spectroscopy, and electrochemical techniques (cyclic, normal pulse, and differential pulse voltametry). The compounds all undergo a single, reversible oxidation reduction process.