Crystal structures of the phosphorus-boron adducts n-Pr3P center dot BBr3 and I3P center dot BBr3

摘要

The structures of the phosphorus-boron adducts n-Pr3P . BBr3 (trigonal, space group P (4) over bar 4c1. Z=4, n=11.5423(6), b=11.5423(6) and c=13.8066(7) Angstrom) and I3P . BBr3 (orthorhombic, space group Pnma, Z=4, n=12.761(2), b=11.427(1), c=7.3728(7)A) were determined by X-ray crystallography. The P-B distance of 2.01(1) Angstrom in I3P . BBr3 is significantly longer than the P-B bond in n-Pr3P . BBr3 (1.95(1) Angstrom). The different Lewis basicity of phosphorus halides, PX3 (X = Cl, Pr, I), and alkylphosphines is discussed. The charge transfer and the bond situation in these donor-acceptor complexes is studied on the basis of NBO analysis. Selected frequencies of n-Pr3P . BBr3 obtained by Raman and infrared spectroscopy are assigned and compared with the normal modes of I3P . BBr3. [References: 41]