CRYSTAL AND MOLECULAR-STRUCTURES OF P,P-DIPHENYL-N-METHYL-PHOSPHINYLTHIOFORMAMIDE AND P-DI-PHENYL-N-PHENYL-SELENOPHOSPHINYLTHIOFORMAMIDE

The crystal structures of the title compounds P,P-diphenyl-N-methyl-ph osphinylthioformamide, [Ph2P(O)C(S)N(H)Me], and P-diphenyl-N-phenyl-se lenophosphinylthioformamide, [Ph2P(Se)C(S)N(H)Ph], have been determine d at room temperature. The pale-yellow crystals of [Ph2P(O)C(S)N(H)Mel are monoclinic, space group P2(1)/c with unit cell dimensions a = 9.6 63(l), b = 14.073(2), c = 10.775(1) angstrom, beta = 105.78(1)-degrees , Z = 4 and D(x) = 1.297 Mg m -3. The green crystals of [Ph2P(Se)C(S)N (H)Ph] are orthorhombic, crystallizing in the Pbca space group with di mensions a = 11.978(l), b = 8.772(5), c = 34.241(4) angstrom, Z = 8 an d D(x) = 1.477 Mg m-3. The structures were solved by direct-methods an d Patterson methods, respectively and each refined by a full-matrix le ast-squares procedure to final R = 0.041 using 1474 reflections for [P h2P(O)C(S)N(H)Me] and R = 0.046 using 1371 reflections for [Ph2P(Se)C( S)N(H)Ph]. The conformation about the C - N bond in [Ph2P(O)C(S)N(H)Me ] is Z with important parameters: P = O 1.485(2), P-C 1.843(3), C = S 1.653(3) and C-N 1.313(4)angstrom. Centrosymmetric molecules associate in the lattice via hydrogen bonding contacts. A similar Z conformatio n is found in [Ph2P(Se)C(S)N(H)Ph] with important parameters: P = Se 2 .108(2), P - C 1.871(7), C = S 1.634(8) and C - N 1. 317(9) angstrom. The analysis of the geometric parameters defining the central chromoph ore indicate that the P - C bonds are comparatively weak in these phos phorus(V) compounds.