The reaction of lithiated Ph(H)PCH2P(H)Ph with (ClCH2)2PPh yields 1,3,5-Triphenyl-1,3,5- triphosphorinane (1) as a mixture of two isomers. The isomers have been separated by column chromatography and characterized by NMR spectroscopy and single crystal X-ray diffraction as the eq-eq-eq (1a) and eq-eq-ax-isomers (1b). (1a) crystallizes with a = 1326.9(3) pm and c = 933.4(3) pm in the rhombohedral space group R3 and displays 3-fold symmetry, showing an eq-eq-eq conformation. (1b) crystallizes in the monoclinic space group P21/c with a = 984.09(12) pm, b = 1757.5(2) pm, c = 1083.13(12) pm, β = 93.329(2)° and displays an ax-eq-eq conformation.