The YLID-IV (C22H18O3PCl3) crystal belongs to the monoclinic system with space group P21/n and unit cell parameter α = 13.518(6)?, b = 14.923(7)?, c = 11.473(5)?, β = 99.81(2), z = 4. The intensity data were collected on the Philips PW-1100 diffrac-tometer. The structure was determined by direct method (MULTAN-78) and refined by full-matrix least-squares method to a final R value of 0.074 for 2592 reflexions. The hydrogen atom locations were determined by difference Fourier synthesis.