| Title
| - Dissociation of 2,4-Bis(2,4,6-tri-tert-butylphenyl)-cyclo-1,3-dipnicta-2,4-diazanes(pnict = P, As, Sb) Imposed by Substituent Steric Strain: A Cyclobutane/Olefin Analogy
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| Abstract
| - Three 2,4-bis(Mes*)-cyclo-1,3-dipnicta-2,4-diazanes, 2PnX, have been synthesized as 1,3-dichloro- (Pn = As; X= Cl) or 1,3-bis(triflato)- (Pn = P, Sb; X = OTf) derivatives (Mes* = 2,4,6-tri-tert-butylphenyl; OTf = triflato =trifluoromethanesulfonoxy). The compounds have been structurally characterized as cyclodimers, but spectroscopiccharacterization of melts and solutions indicates facile dissociation of the diphosphadiazane 2POTf derivative togive the corresponding iminophosphine 1POTf and of the diarsadiazane 2AsCl derivative to give the correspondingiminoarsine 1AsCl. 1,3-Bis(triflato)-2,4-bis(Mes*)-cyclo-1,3-distiba-2,4-diazane (2SbOTf) does not dissociate in themelt or in solution. The presence of the sterically bulky Mes* substituent does not preclude association of N−Pnolefin analogues to give single bonded cyclobutane analogues. The facile dissociation of 2POTf and isolation of1POTf implicates a relatively high degree of substituent steric strain in the dimer. In comparison, dissociation of2AsCl is only apparent in the melt and in solution, likely the result of the lower substituent strain in the larger N2As2framework. The largest N2Pn2 framework in 2SbOTf provides sufficient space for the Mes* substituents, and themonomer is not observed under the conditions examined.
- Three 2,4-bis(Mes*)-cyclo-1,3-dipnicta-2,4-diazanes (Pn = As; X = Cl; Pn = P, Sb; X = OTf) have been structurally characterized as cyclodimers, but the spectroscopic characterization of melts and solutions indicates facile dissociation of the diphosphadiazane and diarsadiazane derivatives to the corresponding iminopnictines, while the distibadiazane does not dissociate in the melt or in solution because of the lower substituent strain in the larger N2Pn2 framework.
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