Structures of Electron Donor-Acceptor Complexes of Boron Trihalides in the Gas Phase

Abstract

The molecular structures of n-v type electron donor-acceptor complexes of boron trihalides with trimethylamine, trimethylphosphine, pyridine and dimethyl ether were determined in the gaseous phase by electron diffraction. From comparison with the results from X-ray diffraction and microwave spectroscopy, it appears that the results obtained from electron diffraction method are the most reliable to determine the structure and stability relation for these complexes. The systematic study yielded that the structural parameters of the cornplexed donor and acceptor changed significantly from those of the uncomplexed donor and acceptor and also changed continuously depending on the acceptor and donor without controversy reported so far. It was found that the acceptor and donor strengths were in the order of BF₃ <BCl₃ <BBr₃ <BI₃ and Me₂0 <C₅H₅N <Me₃N <Me₃P, respectively.