Alkylphosphonic dihalides —

A convenient preparatory method is to form the tertiary phosphine molybdenum hexafluoride complex in methylene chloride at -60°C. On heating such complexes, R3PF2-type compounds are liberated (6.510). Hydrogen fluoride adds to alkylphosphonous dihalides (6.511). Fluorophosphoranes are also obtained from diphosphines (6.538 below), or by halogenation of R2NPF2 -type compounds (7.107). 

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