A New Synthesis of &Substituted 2,3-Dihydro-1,3-dimethyl-l,3,2h3benzodiazaphosphorin-4(l~-ones and Alkylaminodifluorophosphanes with Chlorodifluorophosphane. -Synthesis and Structure of f cis-Bis [ bis( 2-chloroet hy1)aminodifluorop hosphane] dichloro} platinum(I1) * Key Words: 2,3-Dihydro-l,3-dimethyl-1,3,2-benzodiazaphosphorin-4-( lH)-ones, 2-trimethylsiloxy-, 2-0xo-, and 2-fluorosubstituted I Equilibrium reaction I Aminodifluorophosphanes I Platinum complex 2,3 -Dihy dro -1,3dimethyl -2 -ox0 -1,3, 2h4benzo diaz a p hosphorin-4( 1H)-one 1 reacted with diethylaminotrimethylsilane to give solely the 2-trimethylsiloxy-h3-diazaphosphorinone 2.The reaction of 2 with the 2-chloro-h3-diazaphosphorinone 3 yielded the P-0-P-bridged compound 4 in a n equilibrium reaction with elimination of trimethylchlorosilane. The synthesis of the P-difluorophosphite-substituted h3-benzodiazaphosphorinone 6 was effected by the reaction of chlorodifluorophosphane (5) with 1 in the presence of triethylamine in a I : 1 molar ratio, or in the reaction of 5 with 2 or 4. The reac-1.ion of 5 with 6 led, with elimination of p-0x0-bis(dif1uorophosphane), to the P(II1)Cl species 3. 5 reacted with N,N'dimethylanthranilamide in the presence of triethylamine in a 2:1:2 molar ratio to give the N,N'-bis(dif1uorophosphane) derivative 9, as evidenced by low temperature (-30°C) "Fand 31P-NMR data. At room temperature the 2-fluoro-h3-diazaphosphorinone 10 was formed from 9 with intramolecular elimination of phosphorus trifluoride. 2-Chloroethyl-or bis(2-chloroethy1)aminodifluorophosphane 11 and 12 were obtained in the reaction of 5 with 2-chloroethyl-or bis(2-chloro-ethy1)amine hydrochloride in the presence of triethylamine in a 1:1:2 molar ratio. 12 reacted with (COD)PtC12 (COD = 1 3cyclooctadiene) in a 2 : l molar ratio to give the (cis-bis[bis(2chloroethyl) aminodifluorophosphane]dichloro)platinum(II) complex 13. The characterization of 2, 4, 6, and 11-13 is based on their NMR and mass spectra. The structures of 10 and 13 were established by single-crystal X-ray analysis. 10 crystallizes with two independent molecules. Both six-membered heterocycles display a n envelope conformation with the phosphorus atoms 36.9 and 50.4 pm, respectively, out of the plane. The phosphorus atoms have pyramidal coordination geometry. The cis-configuration at platinum(I1) in the complex 13 was confirmed; two ligands (12) are coordinated to Pt" via phosphorus. The platinum atom has a distorted square-planar coordination geometry.