Group 13 Superacid Adducts of [PCl2N]3 - Inorganic Chemistry (ACS

Article pubs.acs.org/IC

Group 13 Superacid Adducts of [PCl2N]3 Zin-Min Tun, Amy J. Heston, Matthew J. Panzner, Vincenzo Scionti, Doug A. Medvetz, Brian D. Wright, Nicholas A. Johnson, Linlin Li, Chrys Wesdemiotis, Peter L. Rinaldi, Wiley J. Youngs, and Claire A. Tessier* Department of Chemistry, The University of Akron, Akron, Ohio 44325-3601, United States S Supporting Information *

ABSTRACT: Irrespective of the order of the addition of reagents, the reactions of [PCl2N]3 with MX3 (MX3 = AlCl3, AlBr3, GaCl3) in the presence of water or gaseous HX give the air- and light-sensitive superacid adducts [PCl2N]3·HMX4. The reactions are quantitative when HX is used. These reactions illustrate a Lewis acid/Brønsted acid dichotomy in which Lewis acid chemistry can become Brønsted acid chemistry in the presence of adventitious water or HX. The crystal structures of all three [PCl2N]3·HMX4 adducts show that protonation weakens the two P−N bonds that flank the protonated nitrogen atom. Variable-temperature NMR studies indicate that exchange in solution occurs in [PCl2N]3·HMX4, even at lower temperatures than those for [PCl2N]3·MX3. The fragility of [PCl2N]3·HMX4 at or near room temperature and in the presence of light suggests that such adducts are not involved directly as intermediates in the hightemperature ring-opening polymerization (ROP) of [PCl2N]3 to give [PCl2N]n. Attempts to catalyze or initiate the ROP of [PCl2N]3 with the addition of [PCl2N]3· HMX4 at room temperature or at 70 °C were not successful.

■

Brønsted−Lewis superacids,14 which are prepared from the reaction of a Brønsted acid with a Lewis acid. Herein we focus on the superacids derived from the common, group 13 Lewis acids AlCl3, GaCl3, and AlBr3 and HX (X = Cl, Br), two of which have been used to initiate the ROP of [PCl2N]3.15 There is no agreement on how to refer to conjugate Brønsted−Lewis superacids. They have been referred to as HX/MX3 or HX− MX3 to emphasize their source, as HX → MX3 to describe their computed gas-phase structure, or as HMX4 to emphasize that an acidic species that is different from HX and MX3 is formed.14,16 We will use the latter general formula because the crystal structures of [PCl2N]3·HMX4 (see below) are consistent with the HMX4 formula. It should be emphasized that none of these simple ways of describing HMX4 can specify all of the species that could be involved in solution, species that include the dimetallic anions [M2X7]−.14,17 In our studies of the reactions of group 13 Lewis acids MX3 (MX3 = AlCl3, GaCl3, AlBr3) with [PCl2N]3, we have observed two major types of products. With the most rigorous exclusion of water or HX,18 the adducts [PCl2N]3·MX3 are the major products. Herein we continue this work and describe the effect of added water or HX to [PCl2N]3/MX3 systems. Specifically, we report the syntheses and characterization of three [PCl2N]3· HMX4 (HMX4 = •HAlCl4, HGaCl4, and HAlBr4) complexes. Because traces of water are always present when MX3 is used, the results described herein may apply to subfields other than phosphazenes.

INTRODUCTION Most phosphazene compounds, including the important polyphosphazenes, are prepared from chlorophosphazenes.1 In order to understand the difficulties in the synthesis, storage, and handling of the parent polymer [PCl2N]n, we have been studying the fundamental acid−base chemistry of chlorophosphazenes. One poorly understood aspect of chlorophosphazene chemistry is the role that Brønsted acids play. The effect of various Brønsted acids on the ring-opening polymerization (ROP) of [PCl2N]3 to give [PCl2N]n has been studied. The acids behave as initiators/catalysts2 or retardants3 or show variable effects.4 Unspecified Brønsted acids are impurities in freshly prepared mixtures of rings [PCl2N]m (m ≈ 3−12) and linear oligomers,5,6 may be involved in the otherwise uncatalyzed ROP of [PCl2N]3,7 and may lead to the degradation of polymeric [PCl2N]n on prolonged storage.8 The most obvious role for a Brønsted acid in the above chemistry would be to protonate the nitrogen atoms of the chlorophosphazenes. In contrast to alkyl- and aminosubstituted phosphazenes, which can be strong bases, most reports indicate that halogen-substituted phosphazenes have very low basicities.9,10 Although several complexes of strong acids of either [PCl2N]3 or [PCl2N]4 have been reported,11 only those of the superacids HAlBr4,12 and H[CB11R5X6] (R = H, Me, X; X = Cl, Br)13 have been characterized by X-ray crystallography. Protonation at a nitrogen atom to yield H[PCl2N]3+ has been observed in these cases. This work describes the reactions of [PCl2N]3 with superacids. Our work with HAlBr4 indicated above was the starting point for this project.12 The superacids are conjugate © XXXX American Chemical Society

Received: October 10, 2015

A

DOI: 10.1021/acs.inorgchem.5b02341 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry Table 1. Crystal Data and Structure Refinement for [PCl2N]3·HAlCl4, [PCl2N]3·HGaCl4, and [PCl2N]3·HAlBr4 empirical formula formula weight temperature (K) wavelength (Å) cryst syst space group unit cell dimens a (Å) α (deg) b (Å) β (deg) c (Å) γ (deg) volume (Å3) Z density (calcd) (Mg/m3) abs coeff (mm−1) F(000) cryst size (mm3) θ range for data collection (deg) index ranges reflns collected indep reflns completeness to θ = 26.30° (%) abs corrn max and min transmn refinement method data/restraints/param GOF on F2 final R indices [I > 2σ(I)] R indices (all data) largest diff peak and hole (e· Å−3)

■

Al Cl10 H N3 P3 517.43 100(2) 0.71073 monoclinic P2(1)/n

Cl10 Ga H N3 P3 560.17 100(2) 0.71073 monoclinic P2(1)/n

Al Br4 Cl6 H N3 P3 695.27 100(2) 0.71073 triclinic P1̅

12.684(3) 90 10.277(3) 108.495(4) 13.962(4) 90 1726.0(8) 4 1.991 1.923 1000 0.39 × 0.34 × 0.07 1.89−26.30

12.723(5) 90 10.263(4) 108.603(6) 13.981(6) 90 1730.2(12) 4 2.150 3.391 1072 0.29 × 0.10 × 0.06 1.89−26.30

7.6721(9) 4.643(2) 9.9263(12) 85.055(2) 12.3245(14) 73.178(2) 892.77(18) 2 2.586 10.212 644 0.10 × 0.06 × 0.03 1.66−26.30

−15 ≤ h ≤ 15, −12 ≤ k ≤ 12, −17 ≤ l ≤ −15 ≤ h ≤ 15, −12 ≤ k ≤ 12, −17 ≤ l ≤ 16 16 13468 13033 3505 [R(int) = 0.0366] 3500 [R(int) = 0.0648] 100.0 99.7

−9 ≤ h ≤ 9, −12 ≤ k ≤ 12, −14 ≤ l ≤ 15 7222 3598 [R(int) = 0.0240] 98.9

semiempirical from equivalents 0.8771 and 0.5209 Full-matrix least-squares on F2 3505/0/158 1.663 R1 = 0.0288, wR2 = 0.0635 R1 = 0.0322, wR2 = 0.0643 0.557 and −0.501



bath) traps and stored in a glass bulb attached to the high-vacuum line, which was equipped with a manometer. To add dry HCl to a reaction, the Schlenk flask containing the reaction mixture was attached to the high-vacuum line. The desired volume of HCl was measured, and the gas was condensed into the reaction flask at liquid-N2 temperature. HBr gas was purchased in a lecture bottle from Matheson Gas Products, Inc., and used as received. X-ray Crystallography. In the glovebox, crystals were put into Paratone oil on a slide. The slide was transported from the glovebox to the instrument in a desiccator that was wrapped in aluminum foil. The crystals were immediately mounted in low light and cooled to 100 K on the diffractometer. Data collection took place with the laboratory lights turned off. Crystal structure data sets were collected on a Bruker Apex CCD diffractometer with graphite-monochromated Mo Kα radiation (λ = 0.71073 Å). Unit cell determination was achieved by using reflections from three different orientations. An empirical absorption correction and other corrections were done using multiscan SADABS. Structure solution, refinement, and modeling were accomplished using the Bruker SHELXTL package.21 The structures were obtained by full-matrix least-squares refinement of F2 and the selection of appropriate atoms from the generated difference map. Crystal data and structure refinement for the three [PCl2N]3·HMX4 adducts are given in Table 1. The crystal structure of [PCl2N]3·HAlCl4 was solved in two different space groups. The solution of the monoclinic structure is featured herein because it had a lower R value. The disordered orthorhombic structure of [PCl2N]3·HAlCl4 is given in the Supporting Information.

EXPERIMENTAL SECTION

General Procedures. Except where otherwise specified, all manipulations were performed under argon, nitrogen, or vacuum using standard anaerobic techniques such as Schlenk, vacuum-line, and glovebox techniques.19,20 The vacuum line had an ultimate capability of 2 × 10−4 Torr. The atmosphere of the argon-filled glovebox was routinely checked by a light-bulb test, and the oxygen and moisture contents inside the glovebox were kept between 1 and 5 ppm. All glassware was dried in an oven overnight (∼120 °C). Either the reaction apparatuses were assembled hot and immediately subjected to vacuum on the Schlenk line or the hot glassware was placed in the port of the glovebox and immediately evacuated before assembly in the glovebox. The glassware was made with virtually greaseless Fisher/ Porter Solv-seal glass joints. High-vacuum valves on the flasks were purchased from Kimble/Kontes. Materials. Hexane, chloroform, methylene chloride, and chlorobenzene (Fisher) were dried and deoxygenated by alumina and copper columns in the Pure Solv solvent system (Innovative Technologies, Inc.). Deuterated methylene chloride (99.9%) and deuterated chloroform (99.8%) were purchased from Cambridge Isotopes, distilled three times over freshly activated 4 Å molecular sieves, and stored under argon in foil-wrapped storage tubes in the glovebox. [PCl2N]3 (Aldrich or made according to the literature27) and AlCl3, AlBr3, and GaCl3 (Alfa Aesar) were purified by sublimation and stored in the glovebox. BCl3 (1 M solution in heptane) from Aldrich was used as received. [PCl2N]3·MX3 were prepared following the published procedures.18 HCl gas (Praxair, 99%) was purified by fractional vacuum distillation through two −78 °C (dry ice/acetone B


Article

Inorganic Chemistry

slowly added to the flask. The flask was wrapped with aluminum foil, and the reactants were stirred overnight in the dark. A clear, slightly brown solution was observed the following morning. The solution was stored in the dark for 2 days, and no further change was observed. The volatile components were slowly removed in vacuo to give colorless crystals of [PCl2N]3·HAlCl4. Recrystallization in chlorobenzene afforded better crystals in an orthorhombic unit cell. Yield: 90%. HRMS (ESI+). Calcd for [H(PCl2N)3]: m/z 345.7. Found: m/z 345.7. HRMS (ESI−). Calcd for [AlCl4]: m/z 166.9. Found: m/z 166.9. Route 4. In the glovebox, [PCl2N]3 (0.69 g, 2.0 mmol) was dissolved in CHCl3 (20 mL) to give a colorless solution. AlCl3 (0.266 g, 2.0 mmol) was added, and the reaction was allowed to stir for 30 min. Because of the light sensitivity of the solution, the reaction flask was wrapped in aluminum foil and taken out of the glovebox. The flask was attached to the high-vacuum line, and dry HCl (0.50 L at 0.096 atm, 295 K; 2 mmol) was condensed into the flask. The reaction flask was thawed, and the solution was stirred overnight at room temperature. The volatiles were slowly removed in vacuo to yield colorless crystals, which were characterized as [PCl2N]3·HAlCl4. Yield: 90%. Syntheses of [PCl2N]3·HAlBr4. Route 1. In the glovebox, [PCl2N]3· AlBr3 (10 mg, 0.016 mmol) was dissolved in CDCl3 (0.70 mL) in a NMR tube. Gaseous HBr (excess) was bubbled in the tube on the Schlenk line. The NMR tube was flame-sealed, and VT NMR studies were conducted. 31P NMR (CDCl3): δ 18.0 (s) at 25 °C, 17.8 (s) at 0 °C, 17.6 (s) at −20 °C, 17.45 (s) at −40 °C. 1H NMR (CDCl3): δ 10.19 (s) at 25 °C, 10.10 (s) at 0 °C, 10.02 (s) at −20 °C, 9.94 (s) at −40 °C. Route 2. In the glovebox, [PCl2N]3·AlBr3 (1.23 g, 2.0 mmol) was dissolved in CHCl3 (20 mL) to give a colorless solution. In air, H2O (2 mmol) was added into the flask via syringe, and the reaction mixture was stirred overnight. The reaction flask was left undisturbed in the dark for 360 days until colorless crystals were observed on the wall of the flask. The volatiles were slowly removed in vacuo. Crystallographic analysis showed that the product crystals were [PCl2N]3·HAlBr4. The 31 P NMR spectrum of the crystals was as above except that weak resonances were observed that were consistent with the hydrolysis products of [PCl2N]3.22 Route 3. In the glovebox, (PCl2N)3 (0.695 g, 2.0 mmol) was dissolved in CHCl3 (20 mL) to give a colorless solution. AlBr3 (0.533 g, 2.0 mmol) was added, and the reaction was allowed to stir for 30 min. The reaction flask was wrapped in aluminum foil and taken out of the glovebox. The flask was attached to the Schlenk line, and HBr (excess) was bubbled into the flask. The mixture was stirred overnight at room temperature in the dark. The volatiles were slowly removed in vacuo to yield colorless crystals of [PCl2N]3·HAlBr4. Yield: 85%. HRMS (ESI+). Calcd for [H(PCl2N)3]: m/z 345.7. Found: m/z 345.7. Syntheses of [PCl2N]3·HGaCl4. Route 1. In the glovebox, (PCl2N)3 (0.695 g, 2.0 mmol) was dissolved in CHCl3 (20 mL) to give a colorless solution. GaCl3 (0.352 g, 2.0 mmol) was added, and the reaction was allowed to stir for 30 min. The reaction flask was wrapped in aluminum foil and taken out of the glovebox. The flask was attached to the high-vacuum line, and dry HCl (0.50 L at 0.096 atm, 295 K; 2.0 mmol) was distilled into the flask. The reaction mixture was thawed and stirred overnight at room temperature in the dark. The volatiles were slowly removed in vacuo to yield colorless crystals of [PCl2N]3· HGaCl4. Yield: 92%. 31P NMR (CDCl3): δ 19.75 (s) at 25 °C, 19.19 (s) at 0 °C, 18.26 (s) at −20 °C, 18.09 (s) at −40 °C. 1H NMR (CDCl3): δ 10.30 (s) at 25 °C, 10.29 (s) at 0 °C, 10.26 (s) at −20 °C, 10.20 (s) at −40 °C. HRMS (ESI+). Calcd for [H(PCl2N)3]: m/z 345.7. Found: m/z 345.7. HRMS (ESI−). Calcd for [GaCl4]: m/z 208.7. Found: m/z 208.7. Route 2. In the glovebox, [PCl2N]3·GaCl3 (1.05 g, 2.0 mmol) was dissolved in CHCl3 (20 mL) to give a colorless solution. On the vacuum line, HCl (0.50 L at 0.096 atm, 295 K; 2.0 mmol) was distilled into the flask. The reaction mixture was thawed and stirred overnight at room temperature in the dark. The volatiles were slowly removed in vacuo to yield colorless crystals of [PCl2N]3·HGaCl4. Attempted Synthesis of [PCl2N]3·HBCl4. In the glovebox, (PCl2N)3 (0.695 g, 2.0 mmol) was dissolved in CHCl3 (20 mL) to give a

NMR Spectroscopy. NMR samples were prepared in the glovebox, and all NMR tubes were flame-sealed under vacuum. In order to minimize the presence of degradation products, NMR samples of [PCl2N]3·HMX4 were made within 24 h of the adduct’s preparation. Either the NMR spectra were taken immediately after the NMR samples were prepared or the tube was kept frozen (liquid N2) until the spectra were taken. Routine and variable-temperature (VT) NMR spectra were obtained on a Varian INOVA 400 MHz NMR spectrometer with a 5 mm switchable probe. 1H NMR spectra were referenced to the residual proton resonance of the deuterated solvent. External references were used for the other nuclei: a 0.15 M H3PO4 solution in deuterated solvent (0 ppm) for the 31P spectra and a 1 M AlCl3 solution in deuterated water (0 ppm) for the 27Al spectra. 27Al and 31P NMR were collected with continuous decoupling because of the nuclear Overhauser effect. Mass Spectrometry (MS). For MS, samples were prepared in the glovebox and the sample syringe was brought to the spectrometer in a desiccator. MS spectra were acquired with a SYNAPT HDMS Q/ToF mass spectrometer (Waters, Beverly, MA) equipped with a z-spray electrospray source. The concentration of the electrosprayed samples was 0.01 mg/mL in dry CHCl3. The sample flow rate was set at 10 μL/min. Data acquisition, data processing, and theoretical isotope distribution generation were performed using Waters’ MassLynx 4.1 software. For the positive mode, the instrument was operated at a voltage of 3.5 kV, a sample cone voltage of 35 V, and an extraction cone voltage of 3.2 V; the desolvation gas flow was 800 L/h (N2); the source and desolvation gas temperatures were 90 and 250 °C, respectively. The settings used for the negative mode of [PCl2N]3·HGaCl4 were different from those used for [PCl2N]3·HAlCl4 and [PCl2N]3·HAlBr4. For [PCl2N]3·HGaCl4, the instrument was operated at a voltage of 3.5 kV, a sample cone voltage of −40 V, and an extraction cone voltage of −4.0 V; the desolvation gas flow was 800 L/h (N2); the source and desolvation gas temperatures were 120 and 250 °C. For [PCl2N]3· HAlCl4 and [PCl2N]3·HAlBr4, the instrument was operated at a voltage of −3.5 kV, a sample cone voltage of −30 V, and an extraction cone voltage of 3 V; the desolvation gas flow was 500 L/h (N2); the source and desolvation gas temperatures were 40 and 50 °C, respectively. Syntheses. [PCl2N]3·HMX4 species are extremely light-sensitive, and exposure to light was kept at a minimum throughout the entire synthesis and characterization process. Syntheses of [PCl2N]3·HAlCl4. Route 1. In the glovebox, [PCl2N]3· AlCl3 (10 mg, 0.02 mmol) was dissolved in CDCl3 (0.7 mL) in an NMR tube. Gaseous HCl (excess) was bubbled into the tube on the Schlenk line. The NMR tube was flame-sealed, and VT NMR studies were conducted. 31P NMR (CDCl3): δ 18.76 (s) at 25 °C, 18.42 (s) at 0 °C, 18.17 (s) at −20 °C, 17.92 (s) at −40 °C. 1H NMR (CDCl3): δ 10.21 (s) at 25 °C, 10.11 (s) at 0 °C, 10.01 (s) at −20 °C, and 9.92 (s) at −40 °C. 27Al NMR (CDCl3): δ 102.84 (s) at 25 °C, 102.93 (s) and 97.44 (s) at 0 °C, 102.97 (s) and 97.94 (s) at −20 °C, 103.05 (s) and 97.67 (s) at −40 °C. Route 2. In the glovebox, [PCl2N]3·AlCl3 (0.96 g, 2.0 mmol) was dissolved in CHCl3 (20 mL) to give a colorless solution. In air, H2O (2 mmol) was added to the flask via syringe, and the reaction mixture was stirred overnight. The reaction flask was left undisturbed in the dark for 360 days until colorless crystals were observed on the wall of the flask. The volatiles were slowly removed in vacuo. Crystallographic analysis showed that the product crystals were monoclinic [PCl2N]3· HAlCl4. The 31P NMR spectrum of the crystals was as above except that weak resonances were observed that were consistent with the hydrolysis products of [PCl2N]3.22 Route 3. In the glovebox, AlCl3 (0.13 g, 1.0 mmol) was put into a Schlenk flask and CHCl3 (20 mL) was added. In a storage tube, [PCl2N]3 (0.35 g, 1.0 mmol) was dissolved in CHCl3 (10 mL). The storage tube was attached to the arm of the Schlenk flask containing the AlCl3 solution. The Schlenk flask was attached to the high-vacuum line, and HCl (0.50 L at 0.048 atm, 295 K; 1.0 mmol) was condensed into the reaction flask at liquid-N2 temperature. The flask was thawed, and the solution was stirred for 3 h before the [PCl2N]3 solution was C


Article

Inorganic Chemistry colorless solution. BCl3 in a 1 M solution of heptane (2 mL, 2.0 mmol) was added, and the reaction was stirred for 30 min. The reaction flask was wrapped in aluminum foil and taken out of the glovebox. The flask was attached to the high-vacuum line, and dry HCl (0.50 L at 0.096 atm, 295 K; 2.0 mmol) was transferred into the flask. The reaction mixture was thawed and stirred overnight at room temperature in the dark. The volatiles were slowly removed in vacuo to yield unreacted [PCl2N]3. NMR-Tube Reactions of [PCl2N]3·HMCl4 (M = Al, Ga) with Additional MCl3. In the glovebox, 7 mg of [PCl2N]3·HMCl4 (M = Al, Ga; ∼0.01 mmol) was dissolved in 0.7 mL of CDCl3 in a 9-in. NMR tube. The NMR tube was flame-sealed, and the spectra of the sample were obtained. Immediately after, the tube was scored open in the glovebox, 3 mg of MCl3 (∼0.02 mmol) was added, and the tube was flame-sealed. NMR spectra of the sample were obtained immediately on the same instrument using the earlier instrument settings. NMR spectra are given in the Results and Discussion. Attempted ROP of [PCl2N]3 Catalyzed/Initiated by [PCl2N]3· HAlCl4. In the glovebox, [PCl2N]3 (0.695 g, 2.0 mmol) was dissolved in chlorobenzene (15 mL) to give a colorless solution in a 3-in.-long, medium-walled glass tube with an inner diameter of 10 mm and a constriction. [PCl2N]3·[HAlCl4] (1.03 g, 0.2 mmol) was added. The tube was flame-sealed, and the reaction was heated at 70 °C for 1 h. No ROP was observed. Only the starting material, [PCl2N]3, and black materials, which appeared to be the degradation product of [PCl2N]3· HAlCl4, were recovered.

to have taken only the simplest precautions to keep water out of their reaction, and it appears that the solid product was stored in air before analysis. Therefore, we believe that [PCl2N]3·HAlCl4 or its degradation products were isolated instead in this older work. The reactions of Scheme 1 raise the question of whether [PCl2N]3 forms adducts with HX. In spite of suggestions that such adducts exist,11b,c we could not isolate them by bubbling excess HX (X = Cl, Br) gas into solutions of [PCl2N]3, nor could they be observed by NMR spectroscopy even at a pressure of ∼2 atm (see the Supporting Information). In our hands, we could only isolate protonated complexes of [PCl2N]3 by using a superacid. The three [PCl2N]3·HMX4 adducts are air- and lightsensitive and have significantly greater light sensitivity than the respective [PCl2N]3·MX3. [PCl2N]3·HGaCl4 degrades the quickest of the three. We suspect that the light sensitivity of [PCl2N]3·MX3 adducts may be due to the presence of small amounts of [PCl2N]3·HMX4 impurities. Attempted ROP of [PCl2N]3 in the presence of 10% [PCl2N]3·HAlCl4 as a catalyst/initiator at 70 °C gave only a mixture of [PCl2N]3 and degradation products of [PCl2N]3· HAlCl4, which were not identified. It has been reported that protonated (and methylated) adducts of [PCl2N]3 with carborane anions failed to catalyze or initiate the ROP of [PCl2N]3 at room temperature or at 160 °C.24 BCl3 and its derivative BCl3·OP(OPh)3 are two of the best catalysts/initiators for the ROP of [PCl2N]3.25 In the presence of adventitious water, it is possible that HBCl4 could play a role in the ROP and, therefore, the reaction of HBCl4 (BCl3/HCl) with [PCl2N]3 was investigated. No reaction was observed, which suggests that HBCl4 is too weak of an acid to protonate [PCl2N]3. As mentioned in our previous work,18 we only were able to isolate [PCl2N]3 from the room temperature reaction of BCl3 with [PCl2N]3. Because neither [PCl2N]3·BCl3 nor [PCl2N]3·HBCl4 can be isolated at room temperature, it would not be expected that these adducts exist at higher temperatures. Therefore, these observations suggest that the BCl3-initiated ROP of [PCl2N]3 at ∼210 °C does not involve either [PCl2N]3 adduct. X-ray Crystal Structures. Single crystals suitable for X-ray diffraction of [PCl2N]3·HGaCl4 and [PCl2N]3·HAlBr4 were obtained by crystallization from CHCl3. Depending on the crystallization solvent, monoclinic (chloroform or methylene chloride) and orthorhombic (chlorobenzene) crystals of [PCl2N]3·HAlCl4 were obtained. The discussion concerning the structure of [PCl2N]3·HAlCl4 will center on the monoclinic crystals because a lower R value was obtained. The structure of monoclinic [PCl2N]3·HAlCl4 is isomorphous to that of [PCl2N]3·HGaCl4. The thermal ellipsoid plots of [PCl2N]3· HAlCl4 (monoclinic), [PCl2N]3·HGaCl4, and [PCl2N]3.HAlBr4 are shown in Figure 1. Selected bond distances and angles are given in Table 2. The hydrogen atom was found in all three [PCl2N]3·HMX4 structures. The N−H---X distances are less than the sum of the van der Waals radii of nitrogen and the halogen (3.30 Å for X = Cl; 3.45 Å for X = Br) and therefore are consistent with N− H---X hydrogen bonds.26 Protonation distorts the [PCl2N]3 rings. In [PCl2N]3·HAlCl4 and [PCl2N]3·HGaCl4, the phosphazene ring attains a slight chairlike structure in which the protonated nitrogen atom (dihedral angles: AlCl3, 11.8°; GaCl3, 11.9°) and the opposite phosphorus atom (dihedral angles: AlCl3, 11.4°; GaCl3, 10.1°)

■

RESULTS AND DISCUSSION We first encountered [PCl2N]3·HMX4 species as byproducts of the reactions of MX3 (MX3 = AlCl3, AlBr3, GaCl3) with [PCl2N]3 that were carried out under less-strict anaerobic conditions.12,18 We hypothesized a three-step process for the formation of [PCl2N]3·HMX4 that involved (1) hydrolysis of MX3 to give HX, (2) the reaction of HX with more MX3 to give superacids HMX4,14 and (3) protonation of [PCl2N]3 by HMX4. Scheme 1 shows the results of a series of experiments Scheme 1. Series of Experiments To Investigate How [PCl2N]3·HMX4 Species Were Formeda

a

When H2O was used, small amounts of hydrolysis products also formed, but they are not shown.

that are consistent with this hypothesis. Chloroform, methylene chloride, and chlorobenzene are suitable solvents for the reactions in Scheme 1. The addition of 1 equiv of water to a solution of [PCl2N]3·MX3 gave a mixture of [PCl2N]3·HMX4 and small amounts of unidentified products that appear to be due to hydrolysis of [PCl2N]3.22 The addition of 1 equiv of pure HX either to a solution of preformed [PCl2N]3·MX3 or to a mixture of [PCl2N]3 and MX3 gave [PCl2N]3·HMX4 as the sole product. The order of the addition of the reagents does not have any effect on the formation of the [PCl2N]3·HMX4 product. In this (Scheme 1) and our earlier work, we have not observed any evidence for the formation of phosphazenium cation products, as had been proposed for the reaction of [PCl2N]3 with AlCl3 by Bode and Bach.23 The authors appear D


Article

Inorganic Chemistry

Figure 1. Thermal ellipsoid plots for the crystal structures of [PCl2N]3·HMX4: (a) [PCl2N]3·HAlCl4; (b) [PCl2N]3·HGaCl4; (c) [PCl2N]3·HAlBr4.

[PCl2N]3 (1.575 Å27). The P−N−P angles at the protonated nitrogen are slightly smaller than the other P−N−P angles, and all P−N−P angles are larger by ∼4−5° than the average P−N− P angle in a free [PCl2N]3 (121.2°27). The average N−P−N angles that involve the protonated nitrogen are ∼3° smaller than the remaining N−P−N angles, and all N−P−N angles in [PCl2N]3·HMX4 are smaller than those in the free [PCl2N]3 ring (average = 118.4°27). The structures of the three [PCl2N]3·HMX4 adducts show several intermolecular contacts that are shorter than the sum of covalent radii (N---Cl = 3.30 Å, N---Br = 3.45 Å, Cl---Cl = 3.60

are bent below and above the plane of the remaining ring atoms. The crystal structures of [PCl2N]3·MX3 (MX3 = AlCl3, GaCl3, AlBr3) also show slight chairlike structures.18 On the other hand, the [PCl2N]3 ring in the [PCl2N]3·HAlBr4 adduct becomes slightly twisted upon protonation. A similar twisted ring conformation has been reported in [PCl 2 N] 3 · CH3(CHB11((CH)3)5Br6).13 Protonation also weakens the two ring P−N bonds that flank the protonated nitrogen atom of [PCl2N]3·HMX4. As in [PCl2N]3·MX3,18 these weakened P− N bonds show single-bond character, whereas the remaining P−N bonds are similar to the average bond distances in free E


Article

Inorganic Chemistry

the ranges 3.312−3.527 Å in [PCl2N]3·HAlCl4 and 3.302− 3.596 Å in [PCl2N]3·HGaCl4. In [PCl2N]3·HAlBr4, there are no N---X halogen bonds, and only two bromine atoms of the AlBr4− anion interact with the chlorine atoms of [PCl2N]3 at 3.510−3.741 Å. NMR Studies. VT NMR studies were carried out for all three [PCl2N]3·HMX4 adducts in CDCl3. For comparison, VT NMR studies were also conducted on pure [PCl2N]3 and on mixtures of [PCl2N]3 and gaseous HX (∼1 and 2 atm; X = Br or Cl), and these spectra are given in the Supporting Information. The VT NMR spectra of [PCl2N]3 and [PCl2N]3/HX mixtures are essentially identical. In both, the 31 P resonance shifts upfield by ∼0.4 ppm as the temperature is lowered from +25 to −40 °C. The VT 31P NMR spectra of [PCl2N]3·HAlCl4 at +25, 0, −20, and −40 °C in CDCl3 can be seen in Figure 2. Similar spectra for [PCl2N]3·HGaCl4 and [PCl2N]3·HAlBr4 are shown in the Supporting Information. On the basis of the solid-state structures, a doublet and a triplet are expected in the 31P NMR spectra of [PCl2N]3·HMX4 for the two inequivalent phosphorus atoms. At 25 °C, only one 31P resonance was observed at 18.8 ppm for [PCl2N]3·HAlCl4, 19.8 ppm for [PCl2N]3· HGaCl4, and 18.0 ppm for [PCl2N]3·HAlBr4. These 31P chemical shifts are very close to that of free [PCl2N]3, which is observed at 20.1−19.9 ppm. Even at the lowest temperature (−40 °C), the coupling expected from the solid-state structure was not observed, and only one 31P resonance was observed for all three [PCl2N]3·HMX4 adducts. In addition, line broadening was observed in the VT 31P NMR spectra of [PCl2N]3·HGaCl4. It is unclear whether this line broadening was caused by the nature of the GaCl4− anion or by the concentration effect of the NMR sample. In all three [PCl2N]3·HMX4 adducts, the 31P resonance shifted slightly upfield with decreasing temperature. The net changes in the chemical shift were 1.1, 1.6, and 1.1 ppm for [PCl2N]3·HAlCl4, [PCl2N]3·HGaCl4, and [PCl2N]3· HAlBr4, respectively. Along with the shift in the resonance, there is also a decrease in the half-width (w1/2) in the 31P NMR

Table 2. Selected Distances (Å) and Angles (deg) in [PCl2N]3·HAlCl4 (Monoclinic), [PCl2N]3·HGaCl4, and [PCl2N]3·HAlBr4 [PCl2N]3· HAlCl4

[PCl2N]3· HGaCl4

P−N Distances That Flank the Protonated Nitrogen P(1)−N(1) 1.6524(19) 1.652(3) P(2)−N(1) 1.6461(19) 1.644(3) average 1.649 1.648 Other P−N Bond Distances P(1)−N(3) 1.5438(18) 1.556(3) P(2)−N(2) 1.5458(19) 1.554(3) P(3)−N(3) 1.5844(18) 1.580(3) P(3)−N(2) 1.5854(19) 1.580(3) average 1.565 1.568 P−N−P Angle for Nitrogen Bound to HMX4 P(2)−N(1)−P(1) 124.72(12) 124.83(19) Other P−N−P Angles P(2)−N(2)−P(3) 126.20(12) 126.2(2) P(1)−N(3)−P(3) 126.15(12) 126.10(19) average 126.2 126.1 N−P−N Angles N(3)−P(1)−N(1) 112.68(10) 112.50(16) N(2)−P(2)−N(1) 112.51(10) 112.47(17) N(3)−P(3)−N(2) 115.53(10) 115.73(15) average 112.6 112.5 Hydrogen Bond Distances and Angles N(1)−Cl(7) 3.133(2) 3.134(3) N(1)−H(1)−Cl(7) 171(2) 174(4) N(1)−Br(1) N(1)−H(1)−Br(1)

[PCl2N]3· HAlBr4 Atom 1.658(4) 1.652(4) 1.655 1.554(3) 1.555(3) 1.582(3) 1.577(3) 1.567 124.7(2) 125.5(2) 126.3(2) 125.9 111.71(18) 111.94(18) 115.27(18) 111.8

3.378(4) 151(5)

Å, and Cl---Br = 3.75 Å) and that are consistent with halogen bonding. In isomorphous [PCl2N]3·HAlCl4 and [PCl2N]3· HGaCl4, each has one N---Cl halogen bond (Al, 3.229 Å; Ga, 3.231 Å) and every chlorine atom of the MCl4− anion interacts with at least one chlorine atom of [PCl2N]3 with distances in

Figure 2. VT 31P NMR spectra of [PCl2N]3·HAlCl4 in CDCl3 taken between −40 and +25 °C: (a) +25 °C; (b) 0 °C; (c) −20 °C; (d) −40 °C. F


Article

Inorganic Chemistry

Figure 3. VT 1H NMR spectra of [PCl2N]3·HAlCl4 in CDCl3 taken between −40 and +25 °C: (a) 25 °C; (b) 0 °C; (c) −20 °C; (d) −40 °C.

Figure 4. VT 27Al NMR spectra of [PCl2N]3·HAlCl4 in CDCl3 taken between −40 and +25 °C: (a) +25 °C; (b) 0 °C; (c) −20 °C; (d) −40 °C. The spectra are offset by ∼4 ppm for clarity.

upfield with decreasing temperature for all three adducts. The net changes in the chemical shift were 0.29 ppm for [PCl2N]3· HAlCl4, 0.25 ppm for [PCl2N]3·HGaCl4, and 0.10 ppm for [PCl2N]3·HAlBr4. VT 27Al NMR spectra of [PCl2N]3·HAlCl4 taken between −40 and +25 °C in CDCl3 are shown in Figure 4. A singlet at 102.8 ppm was observed at 25 °C, and this resonance shifted slightly downfield with decreasing temperature. The net change in the chemical shift was 0.25 ppm from +25 to −40 °C. This relatively narrow resonance is consistent with the symmetric AlCl4− anion, which has been reported in the range 99−102 ppm.28 A smaller broader resonance at ∼97.5 ppm is assigned

spectra when the temperature is decreased. Fluxionality in solution can be attributed to movement of the proton among the three nitrogen atoms of [PCl2N]3. Fluxionality in solution was also observed for Lewis acid adducts [PCl2N]3·MX3, although the couplings in their spectra were resolved at −40 °C.18 VT 1H NMR spectra of [PCl2N]3·HAlCl4 taken between −40 and +25 °C in CDCl3 are shown in Figure 3. Similar plots of [PCl2N]3·HGaCl4 and [PCl2N]3·HAlBr4 can be seen in the Supporting Information. At 25 °C, a singlet was observed at 10.21 ppm for [PCl2N]3·HAlCl4, 10.30 ppm for [PCl2N]3· HGaCl4, and 10.19 ppm for [PCl2N]3·HAlBr4. Similar to the 31 P NMR spectral data, the chemical shift of the singlet moved G


Article

Inorganic Chemistry

Figure 5. 27Al NMR spectra of [PCl2N]3·HAlCl4 in CDCl3 taken at 30 °C to investigate the effect of excess AlCl3 concentration in the sample: (a) sample of [PCl2N]3·HAlCl4 with no excess AlCl3; (b) same sample of [PCl2N]3·HAlCl4 with excess AlCl3.

Figure 6. 1H NMR spectra of [PCl2N]3·HAlCl4 in CDCl3 taken at 30 °C to investigate the effect of additional AlCl3: (a) sample of [PCl2N]3· HAlCl4; (b) same sample of [PCl2N]3·HAlCl4 with additional AlCl3.

to the less symmetric [Al2Cl7]− anion, which is observed ∼5 ppm upfield of AlCl4−.28 We have observed only MX4− anions in the crystal structures of the reaction products in Scheme 1. However, with excess MX3 in solution, [PCl2N]3·HMX4 could react to give high concentrations of species with M2X7− or higher anions such as M3X10−.29 These larger anions are expected to be less coordinating than MX4− and, therefore, HM2X7 would be expected to be stronger acids than HMX4. The reaction of roughly 2 mol equiv of MCl3 with 1 equiv of [PCl2N]3·HMCl4 was examined by multinuclear NMR spectroscopy. The 27Al NMR spectrum of 1:2 [PCl2N]3·HAlCl4/AlCl3 (Figure 5b) shows a slight upfield shift for the resonance at ∼100 ppm and a significant increase in the half-line width (Δw1/2) compared to the spectrum of [PCl2N]3·HAlCl4 (Figure 5a). The increase in Δw1/2 can be attributed to an increase in the concentration of less symmetric Al2Cl7− and to chemical exchange between

Al2Cl7− and AlCl4− ions. Similarly, upfield shifts and increases in Δw1/2 of resonances are observed in the 1H and 31P NMR spectra of 1:2 [PCl2N]3·HAlCl4/AlCl3 depicted in Figures 6 and 7. In addition, Figure 5b shows a new, very broad 27Al resonance centered at ∼48 ppm in the 1:2 [PCl2N]3·HAlCl4/ AlCl3 mixture that was not observed for [PCl2N]3·HAlCl4. This resonance is assigned to Al3Cl10− and higher anions, which would have lower symmetry than either Al2Cl7− or AlCl4− ions. 1 H and 31P NMR spectra of the reaction of roughly 2 mol equiv of GaCl3 with 1 equiv of [PCl2N]3·HGaCl4 can be seen in the Supporting Information. The spectra of 1:2 [PCl2N]3·HGaCl4/ GaCl3 shows upfield shifts and increases in Δw1/2 of the 1H and 31 P resonances relative to those of [PCl2N]3·HGaCl4. The presence of Ga2Cl7− and higher anions in 1:2 [PCl2N]3· HGaCl4/GaCl3 would account for these changes in the spectra. MS. The three [PCl2N]3·HMX4 adducts were studied with electrospray ionization mass spectrometry (ESI-MS) in both H


Article

Inorganic Chemistry

Figure 7. 31P NMR spectra of [PCl2N]3·HAlCl4 in CDCl3 taken at 30 °C to investigate the effect of additional AlCl3: (a) sample of [PCl2N]3· HAlCl4; (b) same sample of [PCl2N]3·HAlCl4 with additional AlCl3.

Figure 8. ESI-MS spectrum of [PCl2N]3·HAlCl4 in positive mode: (a) theoretical isotope distribution for (H[PCl2N]3)+; (b) experimental isotope distribution.

Figure 9. ESI-MS spectrum of [PCl2N]3·HAlCl4 in negative mode: (a) theoretical isotope distribution for AlCl4−; (b) experimental isotope distribution.

I


Article

Inorganic Chemistry positive and negative modes in order to identify both the cationic and anionic species. The positive-mode spectra of the [PCl2N]3·HACl4 adduct are shown in Figure 8, whereas the positive-mode spectra for [PCl2N]3·HGaCl4 and [PCl2N]3· HAlBr4 are shown in the Supporting Information. These spectra showed the (H[PCl2N]3)+ ion, and excellent agreement between the observed and theoretical isotopic distributions was obtained. It is important to note that when the ESI-MS spectrum was obtained for [PCl2N]3, only weak fragmentation signals and no signals for (H[PCl2N]3)+ were observed in the positive mode.27 This supports our earlier statement that a superacid is required to protonate [PCl2N]3. The negativemode spectra of [PCl2N]3·HAlCl4 (Figure 9) and [PCl2N]3· HGaCl4 (Supporting Information) showed the respective anions AlCl4− and GaCl4−, and excellent agreement between the observed and theoretical isotopic distributions also was obtained. In order to detect AlCl4− in [PCl2N]3·HAlCl4, milder conditions were needed for the ionization than were used to detect GaCl4− in [PCl2N]3·HGaCl4. The AlBr4− anion was not detected in the negative-mode ESI-MS spectrum of [PCl2N]3· HAlBr4, even under milder conditions than those used to detect the AlCl4− ion. Therefore, the more stable MX4− anion (GaCl4− > AlCl4− > AlBr4−) under the ionization conditions has a larger central atom and smaller halide substituents.

■

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Tel: 330-972-5304. Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS We thank John Rapko (St. Louis College of Pharmacy, St. Louis, MO) for reading the manuscript and providing useful suggestions. We thank the National Science Foundation (NSF) for partial support of this work under Grants CHE-0316944 and CHE-0616601. More recently, support was provided by Israel Chemicals Ltd. and OMNOVA Foundation. The MS studies were supported by NSF Grants CHE-1012636 and CHE-1308307 (to C.W.). We also thank the NSF and Ohio Board of Regents for funds used to purchase the NMR (Grant CHE-9977144), MS (Grant DMR-0821313), and X-ray diffractometer (Grant CHE-0116041) instruments used in this work. We thank the Goodyear Corp. for donation of an NMR instrument used in this work.

■

SUMMARY The reactions of [PCl2N]3 with MX3 under less strict anaerobic conditions or in the presence of water or HX give the protonated phosphazenes [PCl2N]3·HMX4. In all of these reactions, we find no evidence for the formation of the cationic phosphazenium species such as [P 3 Cl 5 N 3 ] + [MX 4 ] − or [P 3 N 3 Cl 4 ] 2+ [AlCl 4 ] − 2 . The complexes [PCl 2 N] 3 ·HCl, [PCl2N]3·HBr, and [PCl2N]3·HBCl4 could not be isolated from reactions of [PCl2N]3 and the appropriate acid. In [PCl2N]3·HMX4, protonation distorts the [PCl2N]3 ring and weakens the two P−N bonds that flank the protonated nitrogen. VT NMR spectra show that the [PCl2N]3·HMX4 adducts are fluxional in solution. For [PCl2N]3·HAlCl4, direct evidence for the presence of both AlCl4− and Al2Cl7− anions in solution was obtained. Solutions of 1:2 [PCl2N]3·HMCl4/MCl3 appear to contain MCl4−, M2Cl7−, and higher anions. As with [PCl2N]3·MX3,18 the fragility of the [PCl2N]3·HMX4 adducts at or below the room temperature rules out that these adducts participate directly as intermediates in the MX3-initiated hightemperature ROP of [PCl2N]3 to give [PCl2N]n. As observed for protonated adducts of [PCl2N]3 with carborane anions,24 [PCl2N]3·HMX4 did not catalyze or initiate the ROP of [PCl2N]3 at room temperature or at 70 °C. The results presented herein have relevance to other areas of chemistry. Water-sensitive Lewis acids such as MX3 are commonly used in electrophilic aromatic substitutions, carbocationic polymerization, and other processes in both organic and inorganic chemistry. When combined with our previous work on [PCl2N]3·MX3,12 the results herein clearly illustrate the dichotomy that can result in the chemistry of water-sensitive Lewis acids such as MX3. Our work brings to light this often overlooked phenomenon.

■

X-ray diffraction data for all crystal structures including orthorhombic [PCl2N]3·HAlCl4 and studies of the reaction of [PCl2N]3 with HX (PDF) X-ray crystallographic data in CIF format (CIF) X-ray crystallographic data in CIF format (CIF) X-ray crystallographic data in CIF format (CIF) X-ray crystallographic data in CIF format (CIF)

■

REFERENCES

(1) Allcock, H. R. Chemistry and Applications of Polyphosphazenes; Wiley-Interscience: New York, 2003; Chapters 4 and 5. (2) (a) Ganapathiappan, S.; Dhathathreyan, K. S.; Krishnamurthy, S. S. Macromolecules 1987, 20, 1501−1505. (b) Mujumdar, A. N.; Young, S. G.; Merker, R. L.; Magill, J. H. Macromolecules 1990, 23, 14−21. (c) Liu, H.; Stannett, V. T. Macromolecules 1990, 23, 140−144. (d) Luten, J.; van Steenis, J. H.; van Someren, R.; Kemmink, J.; Schuurmans-Nieuwenbroek, N. M. E.; Koning, G. A.; Crommelin, D. J. A.; van Nostrum, C. F.; Hennink, W. E. J. Controlled Release 2003, 89, 483−497. (e) Renard, K. A.; Gerber, A. H. U.S. Patent 4,257,917, 1981. (f) Sinclair, D. P.; US Patent # 4,242,316 (1980). (3) (a) Allcock, F. R.; Gardner, J. E.; Smeltz, K. M. Macromolecules 1975, 8, 36−42. (b) Dieck, R. L.; Garrett, T. B.; Magnusson, A. B. U.S. Patent 4,116,891, 1978. (4) Renard, K. A.; Gerber, A. H. U.S. Patent 4,005,171, 1977. (5) Sayed, M. B. Int. J. Chem. 2002, 5, Paper No. 6. http://www.ijc. com/articles/2002v5/6/ (6) Liu, H. Q.; Stannett, V. T. Macromolecules 1990, 23, 140−144. (7) (a) Emsley, J.; Udy, P. B. Polymer 1972, 13, 593−594. (b) Sulkowski, W. W. In Synthesis and Characterizations of Poly(organophosphazenes); Gleria, M., De Jaeger, R., Eds.; Nova Science: New York, 2004; Chapter 4. (8) Andrianov, A. K.; Chen, J.; LeGolvan, M. P. Macromolecules 2004, 37, 414−420. (9) Allcock, H. R. Phosphorus−Nitrogen Compounds; Academic Press: New York, 1972; Chapter 4, pp 10−12. (10) (a) Feakins, D.; Last, W. A.; Neemuchwala, N.; Shaw, R. A. J. Chem. Soc. 1965, 2804−2811. (b) Feakins, D.; Last, W. A.; Shaw, R. A. J. Chem. Soc. 1964, 4464−4471. (11) (a) Bode, H.; Bütow, K.; Lienau, G. Chem. Ber. 1948, 81, 547− 552. (b) Paddock, N. L.; Searle, H. T. Adv. Inorg. Chem. Radiochem. 1959, 1, 347−83. (c) Sayed, M. B. International Journal of Chemistry; Canadian Center of Science and Education: Toronto, Ontario, Canada, 2002; Vol. 5, Paper No. 6.

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.5b02341. J


Article

Inorganic Chemistry (12) (a) Heston, A. J.; Panzner, M. J.; Youngs, W. J.; Tessier, C. A. Phosphorus, Sulfur Silicon Relat. Elem. 2004, 179, 831−837. (13) Zhang, Y.; Tham, F. S.; Reed, C. A. Inorg. Chem. 2006, 45, 10446−10448. (14) (a) Molnar, A.; Olah, G. A.; Surya Prakash, G. K.; Sommer, J. Superacids, 2nd ed.; Wiley: New York, 2009; Chapters 1 and 2. (b) O’Donnell, T. A. Superacids and Acidic Melts as Inorganic Chemical Reaction Media; VCH Publishers: New York, 1993. (15) (a) Coxon, G. E.; Sowerby, D. B. J. Chem. Soc. A 1969, 3012− 3014. (b) Sohn, Y. S.; Cho, Y. H.; Baek, H.; Jung, O.-S. Macromolecules 1995, 28, 7566−7568. (16) Sikorska, C.; Freza, S.; Skurski, P. J. Phys. Chem. A 2010, 114, 2235−2239. (17) (a) Taylor, M. J.; Brothers, P. J. In Chemistry of Aluminum, Gallium, Indium and; Thallium, Downs, A. J., Eds.; Chapman and Hall: London, 1993; Chapter 3. (b) Aldridge, S. In The Group 13 Metals Aluminum, Gallium, Indium, and Thallium: Chemical Patterns and Peculiarities; Aldridge, S., Downs, A. J., Eds.; Wiley: New York, 2011; Chapter 2. (c) Farcasiu, D. Acc. Chem. Res. 1982, 15, 46−51. (d) Koppel, I. A.; Burk, P.; Koppel, I.; Leito, I.; Sonoda, T.; Mishima, M. J. Am. Chem. Soc. 2000, 122, 5114−5124. (e) Otto, A. H.; Steiger, T.; Schrader, S. Chem. Commun. 1998, 391−392. (f) Sikorska, C.; Freza, S.; Skurski, P. J. Phys. Chem. A 2010, 114, 2235−2239. (g) Senger, S.; Radom, L. J. Phys. Chem. A 2000, 104, 7375−7385. (h) Kramer, G. M. J. Org. Chem. 1975, 40, 298−302. and 302−307. (i) Volkov, A. N.; Timoshkin, A. Y.; Suvorov, A. V. Int. J. Quantum Chem. 2004, 100, 412−418. (j) Vianello, R.; Maksić, Z. B. J. Phys. Chem. A 2007, 111, 11718−11724. (k) Jimenez-Fabian, I.; Jalbout, A. F.; Boutalib, A. Cent. Eur. J. Chem. 2007, 5, 1007−1018. (l) Farcasiu, S. L.; Fisk, S. L.; Melchior, M. T.; Rose, K. D. J. Org. Chem. 1982, 47, 453−457. (18) (a) Heston, A. J.; Panzner, M.; Youngs, W. J.; Tessier, C. A. Inorg. Chem. 2005, 44, 6518−6520. (b) Tun, Z.; Heston, A. J.; Panzner, M. J.; Medvetz, D. A.; Wright, B. D.; Savant, D.; Dudipala, V. R.; Banerjee, D.; Rinaldi, P. L.; Youngs, W. J.; Tessier, C. A. Inorg. Chem. 2011, 50, 8937−8945. (19) Shriver, D. F.; Drexdon, M. A. The Manipulation of Air-Sensitive Compounds, 2nd ed.; Wiley: New York, 1986. (20) Plesch, P. H. High Vacuum Techniques for Chemical Syntheses and Measurements; Cambridge University Press: New York, 1989. (21) Sheldrick, G. M. SHELX97: Programs for Crystal Structural Analysis; University of Göttingen, Göttingen, Germany, 1997. (22) Gabler, D. G.; Haw, J. F. Inorg. Chem. 1990, 29, 4018−4021. (23) Bode, H.; Bach, H. Ber. Dtsch. Chem. Ges. B 1942, 75, 215−226. (24) Zhang, Y.; Huynh, K.; Manners, I.; Reed, C. A. Chem. Commun. 2008, 494−496. (25) (a) Fieldhouse, J. W.; Graves, D. F. ACS Symp. Ser. 1981, 171, 315−320. (b) Horn, H. G.; Kolkmann, F. Makromol. Chem. 1982, 183, 1833−1841. (c) Sennett, M. S.; Hagnauer, G. L.; Singler, R. E.; Davies, G. Macromolecules 1986, 19, 959−964. (d) Potts, M. K.; Hagnauer, G. L.; Sennett, M. S.; Davies, G. Macromolecules 1989, 22, 4235−4239. (e) Snyder, D. L.; Strayer, M. L., Jr.; Wang, J. K. U.S. Patent 4,123,503, 1978. (f) Fieldhouse, J. W.; Fenske, S. L. U.S. Patent 4,327,064, 1982. (g) Graves, D. F. U.S. Patent 4,524,052, 1985. (26) (a) Emsley, J. Chem. Soc. Rev. 1980, 9, 91−124. (b) Kovács, A.; Varga, Z. Coord. Chem. Rev. 2006, 250, 710−727. (27) Bowers, D. J.; Wright, B. D.; Scionti, V.; Schultz, A.; Panzner, M. J.; Twum, E. B.; Li, L.-L.; Katzenmeyer, B. C.; Thome, B. S.; Rinaldi, P. L.; Wesdemiotis, C.; Youngs, W. J.; Tessier, C. A. Inorg. Chem. 2014, 53, 8874−8886. (28) (a) Lewiński, J. In Encyclopedia of Spectroscopy and Spectrometry; Linton, J. C., Holmes, J., Tranter, G., Eds.; Elsevier: New York, 1999; Vol. 1, pp 691−703. (b) Gray, J. L.; Maciel, G. E. J. Am. Chem. Soc. 1981, 103, 7147−7151. (c) Č erny, Z.; Machácě k, J.; Fusek, J.; Heřmánek, S.; Křiž, O.; Č ásensky, B. J. Organomet. Chem. 1991, 402, 139−144. (d) Nara, S. J.; Harjani, J. R.; Salunkhe, M. M. J. Org. Chem. 2001, 66, 8616−8620. (29) Dymek, C. J., Jr.; Wilkes, J. S.; Einarsrud, M.-A.; Øye, H. A. Polyhedron 1988, 7, 1139−1145. K


Group 13 Superacid Adducts of [PCl2N]3 - Inorganic Chemistry (ACS

Recommend Documents