The synthesis, structure, and reactions of 1,2,3-triphenyl-1,2,3-triphosphaindane, a novel heterocyclic system. A new synthesis of the 5,10-dihydrophosphanthren system

Abstract

Phenyldilithiophosphine can be prepared in tetrahydrofuran by the action of lithium on phenylphosphonous dichloride and (more satisfactorily) by that of butyl-lithium on phenylphosphine. It reacts with o-bromoiodobenezene and with o-di-iodobenzene to give the crystalline 1,2,3-triphenyl-1,2,3-triphosphaindane, 5,10-dihydro-5,10-diphenylphosphanthren [isolated as the insoluble di(benzyl bromide)], and much apparently polymeric material. The structure of the triphosphaindane has been elucidated by chemical means, and independently by X-ray crystal analysis. A mechanism for the formation of the triphosphaindane and the dihydrophosphanthren, involving the interaction of benzyne and (PhP)_n units, is suggested.

Triphenyltriphosphaindane forms a monosulphide and two isomeric disulphides but not, apparently, a trisulphide, whereas the corresponding triethyl compound readily forms a trisulphide. The structure of the two disulphides can be deduced from the configuration of the parent phosphaindane.

The yield of the diphenylphosphanthren di(benzyl bromide) by the present method is lower than that by the earlier recorded method but the present method is more rapid.