A new form of P: The crystal structure of a fibrous type of red phosphorus was solved using single‐crystal X‐ray diffraction methods and transmission electron microscopy. It consists of double tubes (see picture) and is closely related to the structure of Hittorf's phosphorus. Density functional calculations confirm the experimental results.
Lehrbüchern der allgemeinen Chemie zufolge existieren drei Hauptmodifikationen des Elementes Phosphor, und zwar weißer, roter und schwarzer Phosphor, die sich erheblich in ihren chemischen und physikalischen Eigenschaften unterscheiden. Wird weißer Phosphor erhitzt oder Strahlung aus-
Structure D 2000Fibrous Red Phosphorus. -Fibrous red phosphorus is prepared from amorphous red phosphorus by sublimation with iodine (evacuated silica tubes, 590-570°C, several days). The samples are characterized by single crystal XRD and TEM and the previously assumed structure is confirmed. This form of red phosphorus crystallizes in the triclinic space group P1. The crystal structure consists of tubes with pentagonal cross section, which in turn are a regular sequence of three different building units. The subunits are cages of eight or nine P atoms and dumbbells of two P atoms. The fibrous type of crystalline red phosphorus shows strong structural resemblance to Hittorf's phosphorus. -(RUCK*, M.; HOPPE, D.; WAHL, B.; SIMON, P.; WANG, Y.; SEIFERT, G.; Angew. Chem., Int. Ed. 44 (2005) 46, 7616-7619; Inst. Anorg.
Abstract. Intensely red, moisture-sensitive crystals of [(TiCl 2 )(1,3-P 2 S 8 )] 2 were obtained by the reaction of TiCl 4 and P 4 S 10 at room temperature. The crystal structure determination revealed molecules formally consisting of two units of the anion [1,3-P 2 S 8 ] 2-connected with
The (31)P MAS NMR spectrum of Hittorf's phosphorus has been measured and assigned to the 21 crystallographically distinct phosphorus atoms based on two-dimensional dipolar correlation spectroscopies. Application of such 2D techniques to phosphorus-based networks is particularly challenging owing to the wide chemical shift dispersions, rapid irreversible decay of transverse magnetization, and extremely slow spin-lattice relaxation in these systems. Nevertheless, a complete assignment was possible by using the combination of correlated spectroscopy (COSY) and radiofrequency-driven dipolar recoupling (RFDR). The assignment is supported further by DFT-based ab initio chemical shift calculations using a cluster-model approach, which gives good agreement between experimental and calculated chemical shift values. The (31)P chemical shifts appear to be strongly correlated with the average P-P bond lengths within the P(P(1/3))(3) coordination environments, whereas no clear dependence on average P-P-P bond angles can be detected. Calculations of localized Kohn-Sham orbitals reveal that this bond-length dependence is reflected in energy variations in the corresponding localized p-p-σ orbitals influencing the paramagnetic deshielding contribution in Ramsey's equation. In contrast, the contributions of the lone pairs to shielding differences are small and/or do not vary in a systematic manner for the different crystallographically distinct phosphorus sites. The combined spectroscopic and quantum chemical approach applied here and the increased theoretical understanding of (31)P chemical shifts will facilitate the structural elucidation of other phosphorus-based clusters and networks.
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