The tungsten chlorophosphinovinyl complexes {(eta(5)-C5H5)(Cl)(NO)W(C=CH2)[PR2]} (R = C6H5, 3a; R = CH(CH3)(2), 3b; R = C(CH3)(3), 3c) have been prepared, and their hydrolysis to mu-oxo complexes 4a, 4b, and 5 is described. The molecular structure of 4a, 4b, and 5 is determined by single-crystal X-ray diffraction studies.