TRANSFORMATIONS OF DIFLUOROPHOSPHINES: THE INFLUENCE OF SOLVENT ON THE REACTION PATHWAY AND RING SIZE IN CYCLOPOLYPHOSPHINES

Abstract

The spontaneous transformation reactions of some difluorophosphines in chloroform as solvent are described. First, the redox disproportionation of 2,5-dimethylphenyldifluorophosphine, 1, unexpectedly led to the formation of the cyclopolyphosphine, hexakis-(2,5-dimethylphenyl)cyclohexaphosphine, 2a and 2,5-dimethylphenyltetrafluorophosphorane, 3. Secondly, CF₃PF₂, 4, was found to undergo a scrambling reaction with formation of (CF₃), PF, 5 and PF₃, 6, rather than a redox disproportionation. In contrast, the difluorophosphines, RPF₂ with R = 2,4,6-trimethylphenyl, 9-anthracenyl, and 9-phenanthryl were found to be stable with regard to such transformations. A single crystal X-ray diffraction study of 2 (as a 1:1 solvate with CDCl₃, 2a) was conducted. 2 was found to exist in a chair conformation with a PP bond length of 222.9 pm. The previously known hexamer, (PhP)₆, 2b, was formed in the redox disproportionation of a neat sample of PhPF₂, held at–20°C for several months. Its X-ray crystal structure, first reported in 1965, was redetermined, and served to establish the nature of the product. 2b was found to display a conformation very similar to that of 2/2a.

Key Words:

• Difluorophosphines
• redox disproportionation
• cyclopolyphosphines
• X-ray crystal structure