Phenylphosphinidene oxide. Thermal decomposition of 2,3-benzo-1,4,5,6,7-pentaphenyl-7-phosphabicyclo[2.2.1]hept-5-ene oxide

Crystallographic characterization of a stable 7-phosphanorbornadiene-7-oxide: 2,3-benzo-1,4,5,6,7-pentaphenyl-7-phosphabicyclo[2.2.1] hepta-2,5-diene-7-oxide

“…In fact, the only such compound to be fully characterized (including X-ray crystallographic data) to date [9a] is the Cr(CO) 5 complex of 2,3-bis(methoxycarbonyl)-5,6-dimethyl-7-phenyl-7-phosphabicyclo[2.2.1]hepta-2,5-diene. The synthesis reported herein is, broadly speaking, similar to that very briefly referred to (without experimental details) in the initial report by Stille et al [6]. It involves a Diels-Alder reaction between the known [11] pentaphenylphosphole oxide, 3 (prepared [11] from the phosphole, 2), and benzyne, which is generated in situ [12].…”

“…Compound 1 was chosen for the initial part of our investigation since, although it was the first stable phosphanorbornadiene derivative to be reported [6], no synthetic or spectroscopic (other than mass spectrometric) details were recorded and characterization was based almost entirely upon its chemical behavior. In fact, the only such compound to be fully characterized (including X-ray crystallographic data) to date [9a] is the Cr(CO) 5 complex of 2,3-bis(methoxycarbonyl)-5,6-dimethyl-7-phenyl-7-phosphabicyclo[2.2.1]hepta-2,5-diene.…”

“…A pure sample of 1 was subsequently obtained (45% yield, c.f. 92%, Stille et al [6]) by recrystallization from a mixture of pentane and benzene.…”

“…However, two successful approaches have been developed for the preparation of stable compounds containing the 7-phosphanorbornadiene skeleton. These methods are also of the Diels-Alder type and involve use of either a phosphole oxide [6][7][8] or a metal (Cr, Mo, W) pentacarbonyl complex of a phosphole as the diene in the [4 ‫ם‬ 2] cycloaddition [9]. Metal complexation of the 7-phosphanorbornadienes gives rise to quite stable products [9,10], while preparation of the oxides provides short- [7] or long-term [6,8] stability at room temperature; both of these methods effectively circumvent unwanted reactions at the phosphorus center of a P(III) phosphole derivative.…”

X-ray structures of adducts of 1,2,5-triphenylphosphole with dimethyl acetylenedicarboxylate: a confirmation, a revision, and a new structure

“…In the absence of sufficient material for full characterization of this product these possibilities could not be better established. However, support for these suggestions is obtained from the reported isolation of poly(pheny1-phosphinidene oxide) from an analogous reaction of pentaphenylphosphole oxide with benzyne (20). …”