Syntheses of Halogenated Polyhedral Phosphaboranes: Crystal Structure of conjuncto-3,3′-(closo-1,2-P2B4Br3)2
- Publication Type
- Other publication
- Authors
- Keller, W.
- Year of publication
- 2017
- Published in
- Z. Anorg. Allg. Chemie
- Pubisher
- Wiley-VCH
- Band/Volume
- 8/
- DOI
- 10.1002/zaac.201770081
- Page (from - to)
- 517-522
Co-pyrolysis of B2Br4 with PBr3 at 480 °C gave, in addition to the main product closo-1,2-P2B4Br4, conjuncto-3,3′-(1,2-P2B4Br3)2 (1) and the twelve-vertex closo-1,7-P2B10Br10 (2), both in low yields. X-ray structure determination for 1 [triclinic, space-group P1 with a = 7.220(2) Å, b = 7.232(2) Å, c = 8.5839(15) Å, α = 97.213(15)°, β = 96.81(2)°, γ = 94.07(2)° and Z = 1] confirmed that 1 adopts a structure consisting of two symmetrically boron–boron linked distorted octahedra with the bridging boron atoms in the 3,3′-positions and the phosphorus atoms in the 1,2-positions. The intercluster 2e/2c B–B bond length is 1.61(3) Å. The shortest boron–boron bond within the cluster framework is 1.68(2) Å located between the boron atoms antipodal to the phosphorus atoms. The icosahedral phosphaborane 2 was characterized by 11B-11B COSY NMR spectroscopy showing cross peaks indicative for the isomer with the phosphorus atoms in 1,7-positions. Both the X-ray data of 1 and the NMR spectroscopic data of 1 and 2 give further evidence for the influence of an antipodal effect of heteroatoms to cross-cage boron atoms and, vice versa, of an additional shielding of the phosphorus atoms caused by B-Hal substitution at the boron positions trans to phosphorus.