Phenoxy-thiophosphoryl-dihydrazide C6H5OP(S)(NH-NH2)2 (1a) and phenoxy-phosphoryl- dihydrazide C6H5OP(O)(NH-NH2)2 (1b) react with tetraalkyl-1,3-dichloro-disiloxanes to give the 1-oxa-3,5-diaza-4-phospha(λ5)-2,6-disila-cyclohexanes 2a-2d. Their 1H NMR, 31P NMR, IR, and Raman data are given