Phosphor(V)-nitride durch Hochdruck-Hochtemperatur-Synthese

1. Development and establishment of the high-pressure high-temperature synthesis as a broad approach to nitridophosphates. In this thesis for the first time a broad access to nitridophosphates was developed and therefore the basis for a systematic investigation of this class of compounds was established. It was shown, that under high-pressure conditions (> 3 GPa) using a belt or Walker module crystalline nitridophosphates can be obtained by reaction of phosphorus(V) nitride with alkaline or earth alkaline azides at temperatures of 1200-1600 °C. Thus the possibilty to suppress eliminiation of N2 from nitridophosphates, which occurs at 800 °C under atmospheric pressure, was proved by use of high-pressure conditions. Thereby the maximum temperature in synthesis of nitridophosphates was approximately doubled. A raise of the maximum temperature during the synthesis leads to much better crystallization conditions. Hence the main problem in synthesis of crystalline nitridophosphates, which consists of bad crystallisation conditions due to limited maximum reaction temperature, was solved and the number of the crystallographically well characterized ternary phosphorus(V) nitrides was doubled from nine to eighteen. Especially the number of highly condensed nitridophosphates (molar ratio P : N > 1 : 2) could be raised from three to nine and a second modification of the binary phosphorus(V) nitride P3N5 was obtained. Consequently the high-pressure high-temperature synthesis can be seen as the first widely applicable approach to nitridophosphates. Due to the hermetically sealed reaction cell precise modulation of the P-N framework by systematic variation of the P3N5 : azide molar ratio in the starting materials. Moreover under high-pressure conditions the reaction time was reduced dramatically compared to conventional synthesis. While using conventional methods several hours or days are needed for quantitative reactions, reactions under high pressure conditions succeed in 5-15 min. At the beginning of the work the apparatus for the high-pressure experiments did not exist within the laboratory equipment of our research group. The success of the first experiments (synthesis of NaP4N7, KP4N7, RbP4N7, CsP4N7), which were performed in cooperation with Evers, significantly contributed to the aquisition of the 1000 t-press installed by Huppertz, and the introduction of the multianvil high-pressure technique at the University of Munich (LMU). 2. NaP4N7, KP4N7, RbP4N7, and CsP4N7. The nitridophosphates NaP4N7, KP4N7, RbP4N7, and CsP4N7 were synthesized by reaction of P3N5 with the respective alkaline azide in the molar ratio MN3 : P3N5 = 3 : 4 (M = Na, K, Rb, Cs) at approximately 40 kbar and 1300 °C using a belt module. NaP4N7 (C2/c, a = 1233.45(4), b = 852.30(3), c = 513.97(1) pm, b = 102.572(2)°, Z = 4, Rp = 0.0772, wRp = 0.1077, RF = 0.0718) crystallizes isotypic to CaAl4O7 in a three-dimensional network structure of corner-sharing PN4 tetrahedra with Na + ions in the channels. According to the formula ¥ 3 [(P [4] 4 N 5 [2] N 2 [3] ) - ] N [2] - and N [3] -bridges exist in a molar ratio 5 : 2. KP4N7 (Pnma, a = 1222.72(2), b = 984.25(2), c = 466.24(1) pm, Z = 4, Rp = 0.0865, wRp = 0.1113, RF = 0.0821), RbP4N7 (a = 1231.07(2), b = 989.46(1), c = 468.44(1) pm, Z = 4, Rp = 0.0350, wRp = 0.0462, RF = 0.0589), and CsP4N7 (a = 1242.91(3), b = 997.63(3), c = 471.33(2) pm, Z = 4, Rp = 0.0524, wRp = 0.0646, RF = 0.0494) crystallize isotypic to the mineral barylite BaBe2Si2O7 in a three-dimensional network structure from corner-sharing PN4 tetrahedra with the alkaline ions in the channels. According to the formula ¥ 3 [(P [4] 4 N 5 [2] N 2 [3] ) - ] N [2] - and N [3] -bridges exist in a molar ratio 5 : 2. Using the obtained crystallographic data of MP4N7 (M = Na, K, Rb, Cs) MAPLE and CHARDI calculations as well as calculations based on the bond-length bond-strength concept were carried out and discussed. The radiographically obtained results were confirmed. The compounds were characterized by IR- and 31 P-MAS NMR-spectroscopy (d = -23.5, -25.0 (NaP4N7); -0.4, -1.7 (KP4N7), -19.6, -28.2 (RbP4N7), -21.6, -31.9 ppm (CsP4N7)). Thermogravimetric examinations under inert gas conditions revealed the thermal decomposition temperature of the compounds, which is about 850-900 °C. 3. Rb3P6N11 and Cs3P6N11. The nitridophosphates Rb3P6N11 and Cs3P6N11 were synthesized by reaction of P3N5 with the respective alkaline azide in the molar ratio MN3 : P3N5 = 3 : 2 (M = Rb, Cs) using a Walker module at approximately 35 kbar and 1300 °C. Rb3P6N11 (P4132, a = 1049.74(1) pm, Z = 4, Rp = 0.0979, wRp = 0.1077, RF = 0.0612) and Cs3P6N11 (P4132, a = 1065.15(1) pm, Rp = 0.0487, wRp = 0.0618, RF = 0.0812) crystallize isotypic to K3P6N11 in a three-dimensional network structure of corner-sharing PN4 tetrahedra with the alkaline ions in the channels. According to the formula ¥ 3 [(P 6 [4] N 9 [2] N 2 [3] ) 3- ] N [2] - and N [3] -bridges exist in the molar ratio 9 : 2. Using the obtained crystallographic data of M3P6N11 (M = Rb, Cs) MAPLE and CHARDI calculations as well as calculations based on the bond-length bond-strength concept were carried out and discussed. The radiographically obtained results were confirmed. The compounds were characterized by IR- and 31 P-MAS NMR-spectroscopy (d = -7.4 (Rb3P6N11), -8.9 ppm (Cs3P6N11)). Thermogravimetric examinations under inert gas conditions revealed the thermal decomposition temperature of the compounds, which is about 850-900 °C. Temperature-dependant powder X-ray investigations revealed that Rb3P6N11 shows no thermal expansion between room temperature and 540 °C.4. NaPN2. The nitridophosphate NaPN2 was synthesized by reaction of P3N5 with NaN3 in the molar ratio NaN3 : P3N5 = 3 : 1 using a Walker module at approximately 35 kbar and 1300 °C. NaPN2 (I 4 2d, a = 497.21(2), c = 697.60(3) pm, Z = 4, Rp = 0.0502, wRp = 0.0649, RF = 0.0788) crystallizes isotypic to LiPN2 in a three-dimensional network structure of corner-sharing PN4 tetrahedra with the Na + ions in the channels. According to the formula ¥ 3 [(P [4] N 2 [2] ) - ] N [2] -bridges exist exclusively. Using the obtained crystallographic data of NaPN2, MAPLE and CHARDI calculations as well as calculations based on the bond-length bond-strength concept were carried out and discussed. The radiographically obtained results were confirmed. The compound was characterized by IR- and 31 P-MAS NMR-spectroscopy (d = -15.0 ppm). Thermogravimetric examinations under inert gas conditions revealed the thermal decomposition temperature of the compound, which is about 900 °C. 5. CaP2N4 and SrP2N4. The nitridophosphates CaP2N4 und SrP2N4 were obtained by reaction of Ca(N3)2 and Sr(N3)2 with P3N5 (molar ratio M(N3)2 : P3N5 = 3 : 2) at 35 kbar and 1300 °C in a Walker module. A structure model could be obtained from X-ray powder data. CaP2N4 (P6322, a = 972.11(1) pm, c = 785.90(1) pm, Z = 8, Rp = 0.059, wRp = 0.079, RF = 0.174) and SrP2N4 (P6322, a = 987.44(1), c = 785.90(1) pm, Z = 8, Rp = 0.075, wRp = 0.098, RF = 0.115) crystallize isotypic in a network structure from corner-sharing PN4 tetrahedra with the alkaline earth ions within the channels. Perpendicular to [001] layers from condensed P6N6 sechser rings exists which are linked by P4N4 vierer rings and further P6N6 sechser rings forming the network structure. According to the formula ¥ 3 [(P [4] N 2 [2] ) - ] N [2] -bridges occur exclusively. Using the obtained crystallographic data of CaP2N4 and SrP2N4, MAPLE and CHARDI calculations as well as calculations based on the bond-length bond-strength concept were carried out and discussed. The radiographically obtained results were confirmed. The compounds were characterized by IR- and 31 P-MAS NMR-spectroscopy (d = -20.0, -15.9, -5.2, -3.6, - 2.6 (CaP2N4), -27.8, -23.4, -17.1, -15.5, -14.1 ppm (SrP2N4). Thermogravimetric examinations under inert gas conditions revealed the thermal decomposition temperature of SrP2N4, which is about 900 °C. CaP2N4 was stable up to 1000 °C. 6. g-P3N5. The synthesis of g-P3N5 was successfully carried out at 110 kbar and 1500 °C. In contrast to a-P3N5, which is exclusively build up from PN4 tetrahedera, g-P3N5 forms a three-dimensional network structure from PN4 tetrahedra and tetragonal PN5 pyramids. The tetragonal PN5 pyramid is a formerly unknown structural building unit. In the crystal- structure of g-P3N5 (Imm2, a = 1287.20(5), b = 261.312(6), c = 440.04(2) pm, Z = 2, Rp = 0.073, wRp = 0.094, RF = 0.048) rods of trans edge-sharing PN5 pyramids are condensed via vertice forming layers. These layers are linked by chains of corner-sharing tetrahedra. According to the formula ¥ 3 [P ] 4 [ 1 P ] 5 [ 2 N ] 2 [ 1 N ] 3 [ 4 ] N [2] and N [3] bridges occur in the molar ratio 1 : 4. Using the obtained crystallographic data of g-P3N5, MAPLE and CHARDI calculations as well as calculations based on the bond-length bond-strength concept were carried out and discussed. The radiographically obtained results were confirmed. The compound was characterized by IR- and 31 P-MAS NMR-spectroscopy (d = -11.9, -101.7 ppm). Thermogravimetric examinations under inert gas conditions revealed the thermal decomposition temperature of the compound, which is about 900 °C. The Vickers hardness was determined with a value of 9.7 GPa. 7. Hexaaminodiphosphazenium-bromide, -nitrate, and -toluenesulfonate. It was shown, that the hexaaminodiphosphazenium-salts [(NH2)3PNP(NH2)3]Br, [(NH2)3PNP(NH2)3] [NO3], and [(NH2)3PNP(NH2)3][CH3C6H4SO3] are accessible by anion exchange in water using [(NH2)3PNP(NH2)3]Cl as starting material. The structures of these compounds were obtained from single crystals, which were obtained from an acetonitrile solution in a temperature gradient ([(NH2)3PNP(NH2)3]Br: P 1 , a = 596.2(1), b = 744.5(1), c = 1114.4(1) pm, a = 108.78(1), b = 104.18(1), g = 90.64(1)°, R1 = 0.048, wR2 = 0.104; [(NH2)3PNP(NH2)3][NO3]: P 1 , a = 550.9(1), b = 796.3(1), c = 1115.7(1) pm, a = 94.45(1), b = 99.55(1), g = 101.53(1)°, R1 = 0.033, wR2 = 0.095; [(NH2)3PNP(NH2)3][CH3C6H4SO3]: P21/c, a = 804.1(1), b = 596.1(1), c = 3218.7(3) pm, b = 94.59(1)°, R1 = 0.052, wR2 = 0.136). The compounds crystallize in structures with discrete [(NH2)3PNP(NH2)3] + -ions and the corresponding anions. [(NH2)3PNP(NH2)3]Br is isotypic to [(NH2)3PNP(NH2)3]Cl. Between the ions many hydrogen bonds exist. In [(NH2)3PNP(NH2)3]Br the [(NH2)3PNP(NH2)3] + -ion occurs in a staggered conformation, while in [(NH2)3PNP(NH2)3][NO3] an ecliptic conformation is preferred. In [(NH2)3PNP(NH2)3][CH3C6H4SO3] the gauche-conformation exists. It was shown by Extended Hückel calculations, that no significant rotation barriers exist between the conformations. The compounds were characterized by IR and 31 P NMR-spectroscopy (d = -15.0 ppm). The thermal behaviour of the compounds was examined by thermogravimetry.

Level thesis:degree_level

thesis.doctoral

Grantor dc:publisher

Ludwig-Maximilians-Universität

Year

2001

Author dc:creator

• Landskron, Kai

Repository record source_url

https://edoc.ub.uni-muenchen.de/254/

OAI identifier oai:identifier

oai:edoc.ub.uni-muenchen.de:254