C18H15PS4, M(r) = 390.5, monoclinic, P2(1)/n, a = 10.1406 (5), b = 10.1948 (6), c = 18.870 (1) angstrom, beta = 97.253 (2)-degrees, V = 1935.2 (3) angstrom3, Z = 4, D(x) = 1.34 g cm-3, lambda(Mo K-alpha) = 0.71069 angstrom (graphite monochromator), mu = 5.49 cm-1, F(000) = 808, T = 297 K, R = 0.045 for 2507 observed reflections with I > 3-sigma(I). Distances: P=S 1.899 (1), P-S (av.) 2.102 (2) angstrom; angles (av.): S=P-S 117.1 (3), S-P-S 109.9 (2)-degrees. These are the first crystallographic data for the SP(SCR)3 unit.