Synthesis and X-ray crystal structure of a novel long chain acyclic phosphazene, N,N -{dimethyl-bis(diphenylphosphin- iminophosphorane)}ethylenediamine {(PhO) 2 P(O)NPN(CH 3 )CH 2 } 2 , obtained via a Staudinger reaction Maravanji S. Balakrishna,* Rita M. Abhyankar and Mrinalini G. Walawalker Department of Chemistry, Indian Institute of Technology, Bombay 400 076, India Abstract—The title compound was synthesized by the reaction of N,N-dimethyl-N,N-bis(diphenylphosphino)ethylenediamine with phosphoryl azide and characterized by mass spectrometry, microanalysis, and 31 P and 1 H NMR spectroscopy and the structure was confirmed by single crystal X-ray studies. Since the utilization of the well-known Staudinger reac- tion in the clean synthesis of phosphinimines, a large number of mono- and bis(phosphines) have been effec- tively converted into the corresponding iminophospho- ranes, 1 which were found to be excellent reagents in bridging the main group elements with transition ele- ments. 2,3 The versatility of phosphinimines in the syn- thesis of heterocycles embedded with high-valent transition metals is well documented. 4 The partial oxi- dation of phosphorus centers in bidentate or tridentate ligands with organic azides has led to very useful heterofunctional systems, which have created a host of new coordination and organometallic complexes. 5–8 We report here a new member of this class of com- pounds, the first example of an acyclic bis(iminophos- phorane) derivative of N,N -dimethylethylenediamine having as many as 12 atoms in the chain with as many as six donor atoms. This compound was synthesized by the direct reaction of N,N -dimethyl-N,N -bis- (diphenylphosphino)ethylenediamine 9 with a phosphoryl azide and isolated as an air-stable white crystalline solid in quantitative yield. 10 The 31 P{ 1 H} NMR spectrum of 2 shows two doublets as expected for the phosphin- imine and phosphoryl centers at  23.8 and 9.0, respec- tively, with a 2 J PP value of 32 Hz. The 1 H NMR spectrum of 2 shows a doublet at  2.28 for the methyl protons and a multiplet at  2.98 for the ethylene protons. Further evidence comes from microanalysis and the high-resolution mass spectrum (HRMS), which shows a mass corresponding to a molecular weight of 951. The structure of compound 2 was confirmed by a single crystal X-ray structure determination. 11 The ORTEP 12 plot (Fig. 1) establishes the presence of crystallographically imposed centrosymmetry. The core looks like a diphenyl molecule opened on opposite sides, resembling an unlocked ‘handcuff’. The P(1)N(1) bond distance of 1.651(2) A  is slightly shorter than that of a diphosphine (Ph 2 PN(CH 2 Ph)- CH 2 CH 2 (PhCH 2 )NPPh 2 : 1.680(2) A  ), which is similar to the parent diphosphine 1 but with different sub- Keywords : phosphazene; phosphinimines; Staudinger reaction; X-ray structure.