Ambiphilic compounds: Synthesis and structure of a phosphane-borane with a flexible diphenyl ether tether

The preparation of desired phosphane-borane 1 involves selective lithiation trapping of 2-bromo-2′-iododiphenyl ether 3 to give bromophosphane 4 followed by a second lithiation/electrophilic trapping to install the boron fragment. The structure of the new phosphane-borane was verified by single-crystal X-ray diffraction studies. A problematic intramolecular cyclization of lithiated intermediate 7 in THF was prevented by the use of toluene as the solvent. This result will also be of interest to chemists seeking to prepare related unsymmetrical diphosphanes.