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Regioselective reactivity, molecular cleft selectivity, and conformational properties have been examined in the skeletally stabilized triphosphazanes C 6 H 4 N 2 [P(NEt 2 ) 2 ] 2 PNEt 2 (4), C 6 H 4 N 2 -[P(S)(NEt 2 ) 2 ] 2 PCl (5), and C 6 H 4 N 2 [P(S)(NEt 2 ) 2 ] 2 P(S)NEt 2 (9) and in a series of new derivatives. 3 is oxidized/coordinated regioselectively by O 3 , Se, PhN 3 , and BH 3 to C 6 H 4 N 2 [P(O)(NEt 2 ) 2 ] 2 PNEt 2 and C 6 H 4 N 4 [P(O)(NEt 2 ) 2 ] 2 P(O)NEtz

Reactions of 1,2,4,5-(NH 2 ) 4 C 6 H 2 with (Et 2 N) 3 P and 1,2,3-(NH 2 ) 3 C 6 H 3 with (Me 2 N) 3 P yield the new bis(triphosphazane) C 6 H 2 {N 2 [P(NEt 2 ) 2 ] 2 PNEt 2 } 2 (4) and tetraphosphazane C 6 H 3 N 3 [P(NMe 2 ) 2 ] 2 (PNMe 2 ) 2 (6), respectively. 4 with sulfur is oxidized at the exo phosphorus atoms to a tetrasulfide C 6 H 2 {N 2 [P(S)(NEt 2 ) 2 ] 2 PNEt 2 } 2 (5). 6 reacts with elemental selenium to form stepwise diselenide C 6 H 3 N 3 [P(Se)(NMe 2 ) 2 ] 2 (PNMe 2 ) 2 and tetraselenide C 6 H 3 N 3 [P(Se)(NMe 2 ) 2 ] 2 [P(Se)NMe 2 ] 2 . 6 with elemental sulfure yields directly the tetrasulfide C 6 H 3 N 3 [P(S)(NMe 2 ) 2 ] 2 [P(S)NMe 2 ] 2

The orthocyclophane cyclotetraphosphazanes [C 6 H 4 N 2 (PR) 2 ] 2 (R=Ph (4), Me) have been obtained from RPCl 2 /1,2-(NH 2 ) 2 C 6 H 4 /Et 3 N reactions. S 8 oxidation yields [C 6 H 4 N 2 (PhP)(PhPS)] 2 and [C 6 H 4 N 2 ] 2 (PhPS) 3 (PhP) (7); are characterized by spectral (MS, IR, 1 H and 31 P NMR) data. 4 and 6 are further characterized by X-ray single-crystal analyses. Monoclinic, C2/c

The structural characterization of PhN(PCl2)2 and m-MeC6H4N(PCl2)2 in solution by 31P NMR spectroscopy and of PhN(PCl2)2 in the solid by single crystal X-ray analysis is reported. PhN(PCl2)2 adopts a C2v conformation in the solid, in which the phosphorus lone pair electrons are eclipsed and both trans to the Ph group. The C2v conformation assignment for PhN(PCl2)2 and m-MeC6H4N(PCl2)2 is consistent with the low temperature 31P NMR spectral data. PhN(PCl2)2 crystallizes in space group P21, a=6.360(2) A, b=25.618(11) A, c=7.146(2) A, β=90.62(2) deg, Z=4, with two independent molecules per unit cell. The structure was solved and refined by direct methods to R=0.058 and Rw=0.078 for 671 independent reflections. Mean distances (A) and angles (deg) are: P-Cl, 2.036(13); P - N, 1.69(3)

Reaction of 1,2-(NH2),C6H4 with (Et2N)'P produces the linear triphosphazane C6H4N2[P(NEt2),],PNEt2 (6) , in which the phosphorus-nitrogen skeleton is stabilized by incorporation into a 1,3,2-diazaphosphole unit. 'lP NMR spectral evidence has been obtained for monoand diphosphorus intermediates C6H4(NH),PNEt, (7) and C,H,N(NH)(PNEt,)P(NEt,), (8). Reaction of 6 with SB yields C6H4N2[P(S)(NEtZ)2]2PNEt2 (9) followed by C6H4N2[P(S)(NEt2),],P(S)NEt2 (lo), in a highly regioselective oxidation of exo phosphorus atoms. Hydrolysis of 6 occurs exclusively at the central phosphorus atom to form phosphine oxide C6H4N2[P(NEt2)2]2P(0)H (11). 9 with gaseous HC1 yields the monochloride C6H4N2[P(S)(NEt2)2]2PCl (12). Reactions of 12 with Et2NH, H20, NH3, and Me3SiN3 yield 6 and the new compounds C,H,N,[P(S)(NEt,),],P(O)H (13), C6H4N2[P(S)(NEt2),I2PNH2 (14), and C6H4N2[P(S)(NEt2),j2PNs (15), respectively. 6 and 9-15 have been characterized by spectral (IH and 'IP NMR, IR, and MS) data. In addition, 9 has been characterized by single-crystal X-ray diffraction: orthorhombic, Pbca, a = 14.652 ( 5 ) A, b = 18.91 1 (9) A, c = 24.324 (9) A, V = 6739 (4) A', Z = 8, R = 0.060, R, = 0.075. The P=S bonds of the bulky P(S)(NEt,), units are oriented approximately trans relative to the electron pair of the inner phosphorus atom P(2), creating a hindered molecular cleft at that phosphorus atom. The reactivity data for 6, 9, and 12 confirm the hindered, highly selective character of the central phosphorus site.