The novel macrocyclic compounds {(OCH2CMe2CH2O)[(S)PN-t-Bu]2}2 (4) and {(OCH2CMe2CH2O)[P(N-t-Bu)2P(1,2-O2C6Cl4)]}2·3C6H5CH3 (5·3C6H5CH3) based on the cyclodiphosphazane unit are synthesized and characterized by X-ray structure determination; their solution state NMR spectra are consistent with the solid state structures.

The reactivity of diethyl azodicarboxylate (DEAD)/diisopropyl azodicarboxylate (DIAD) with P(III) compounds bearing oxygen or nitrogen substituents is explored. Compounds with structures quite different from that of Morrison-Brunn-Huisgen intermediate R'(3)P(+)N(CO(2)R)N(-)(CO(2)R) (1), observed in the Mitsunobu reaction, have been established by using X-ray crystallography and NMR spectroscopy. Thus reactions with X(6-t-Bu-4-Me-C(6)H(2)O)(2)P-NH-t-Bu [X = S (8), CH(2) (9)] or XP(mu-N-t-Bu)(2)P-NH-t-Bu [X = Cl (14) or NH-t-Bu (15)] and DEAD/DIAD lead to phosphinimine-carbamate-type of products X[6-t-Bu-4-Me-C(6)H(2)O](2)P[N-t-Bu][N(CO(2)R)NH(CO(2)R)] [X = S, R = Et (16); X = CH(2), R = Et (17); X = CH(2), R = i-Pr (18)] or XP(mu-N-t-Bu)(2)P(N-t-Bu)[N-(CO(2)-i-Pr)-N(H)(CO(2)-i-Pr) [X = Cl (19), NH-t-Bu (20)]. Treatment of 19 with 2,2,2-trifluoroethanol afforded the product [(CF(3)CH(2)O)P(mu-N-t-Bu)(2)P(+)(NH-t-Bu)[N(CO(2)-i-Pr)(HNCO(2)-i-Pr)]][Cl(-)] (21) whose structure is close to one of the intermediates proposed in the Mitsunobu reaction. The isocyanate CH(2)(6-t-Bu-4-Me-C(6)H(2)O)(2)P-NCO (10) underwent 1,3-(P,C) cycloaddition with DEAD/DIAD to lead to CH(2)(6-t-Bu-4-Me-C(6)H(2)O)(2)P[N(CO(2)R)N(CO(2)R)-C(O)-N] [R = Et (22), i-Pr (23)]. Reaction of 22-23 with 1,1'-bi-2-naphthol or catechol leads to novel tetracoordinate CH(2)(6-t-Bu-4-Me-C(6)H(2)O)(2)P(2,2'-OC(10)H(6)-C(10)H(6)-OH)[NC(O)-(CO(2)R)NH(CO(2)R)] [R = Et (24), i-Pr (25)] or pentacoordinate CH(2)(6-t-Bu-4-Me-C(6)H(2)O)(2)P(1,2-O(2)C(6)H(4))[NHC(O)-N(CO(2)R)NH(CO(2)R)] [R = Et (26), i-Pr (27)] compounds in which the original NCO residue is retained; this mode of reactivity is quite different from that observed for the MBH betaine 1. In 27, the nitrogen, rather than the oxygen, occupies an apical position of the trigonal bipyramidal phosphorus violating the commonly assumed preference rules for apicophilicity. It is shown that the previously reported azide derivative 3, obtained from the reaction of 11 with DIAD, undergoes a Curtius-type rearrangement to lead to the fused cyclodiphosphazane [(CH(2)(6-t-Bu-4-Me-C(6)H(2)O)(2))P(OC(O-i-Pr)NN(CO(2)-i-Pr)N)](2) (28); this compound is in equilibrium with its monomeric form in solution at >300 K. Finally, reaction of S(6-t-Bu-4-Me-C(6)H(2)O)(2)P(OPh) (13) with DIAD gave the hexacoordinate compound S[6-t-Bu-4-Me-C(6)H(2)O](2)P(OPh)[N(CO(2)-i-Pr)NC(O-i-Pr)O] (30) with an intramolecular S-->P bond. X-ray crystallographic evidence for compounds 16, 19, 21, 22, 25, 27, 28, and 30 has been provided.

New spirocyclic (amino/amido)tetraoxyphosphoranes CH(2)(6-t-Bu-4-Me-C(6)H(2)O)(2)P(NRR')(O(2)C(6)Cl(4)) [R = Me, R' = Ph (1), R = R' = i-Pr (2); R = R' = H (3); R = H, R' = Ph (4)] and the isothiocyanatotetraoxyphosphorane CH(2)(6-t-Bu-4-Me-C(6)H(2)O)(2)P(NCS)(O(2)C(6)Cl(4)) (5) have been synthesized. X-ray crystallography for these compounds reveals that -N(Me)Ph, -N(i-Pr)(2), and -NCS groups occupy an apical position whereas -NH(2) and -NHPh groups occupy an equatorial position in a trigonal bipyramidal geometry around phosphorus. These results are in contrast with the common assumption that a sterically bulky and less electronegative substituent [e.g. -N(i-Pr)(2)] should be less apicophilic than a sterically small and more electronegative substituent (e.g. -NH(2)). The possible rationalization for these results is discussed. Variable-temperature ((1)H, (31)P) NMR spectra of these compounds show some unusual features not reported before for pentacoordinate phosphorus. Probable intramolecular processes involving (i) apical-equatorial <--> equatorial-apical exchange, (ii) apical-equatorial <--> equatorial-equatorial exchange, and (iii) boat-chair <--> tub (for the eight-membered ring) interconversion as well as cessation of the P-N bond rotation have been invoked to explain the spectral features.