The First Free 7λ³-Phosphanorbornadiene

Abstract

The first uncoordinated 7λ 3 -phosphanorbornadiene 10 is reported. This missing member of the class of 7-heteranorbornadienes was prepared by decomplexation of its pentacarbonyltungsten complex 6 with iodine and N-methylimidazole. It is moderately stable at room temperature toward loss of the phosphinidene bridge (PhP:) because the aromatic fragment, [5]metacyclophane ( 5), is a highly strained compound. For this reason, 10 may be considered to be a hyperstable compound. An analysis of the energetics of the system by density functional calculations supports this rationalization.

X-ray structural analyses and DFT study of 7-thianorbornenes: 4-aza-4-phenyl-10-thiatricyclo[5.2.1.0.2,6]deca-8-ene-3,5-dione and 4-aza-l,4,7-trimethyl-10-thiatricyclo[5.2.1.0.2,6]deca-8-ene-3,5-dione

“…1 Nevertheless, these results cannot be directly compared to 1 Table 9. The largest calculated interactions are electron transfer from the 109.9 C(7)-C(8)-C (9) 110.05 (15) 109.4 109.4 C(1)-S(10)-C (7) 80.02(7) 79.6 7 9 .0 7 9 .0 7 9 .6 7 9 .8 7 9 .5 7 7 .7 C(2)-C(1)-C (9) 105.84 ( 110.9 C(7)-C(8)-C (9) 110.05(15) C(1)-S(10)-C (7) 80.05 (9) These interactions, are combined with a strong π (C 8 C 9 ) → σ * (C 1 H 12 ) hyperconjugative electron transfer. Since the relatively stronger hyperconjugative interactions in sulphoxides 12 and 13 involve the double bonds (in particular π (C 8 C 9 ) → σ * (X 10 O 16 ) interaction in 13), 2 the tendency towards double bond bending on going from methylene to oxygen and sulphoxide bridge is greatly diminished.…”

“…Particularly interesting in this context are molecules in which the carbon atom of the methano-bridge is replaced by a heteroatom [2]. So far, experimental and highlevel computational studies dealing with hetero-norbornene counterparts with oxygen [3][4][5], boron [6], phosphorus [7], silicon and germanium [8] bridges were reported. There is also a low-level computational study (MINDO/3) by Gleiter dealing with deviation of the double bond from planarity in dithiasesquinorbornene [9].…”

Evidence for Iron‐Catalyzed α‐Phosphinidene Elimination with Phenylphosphine

“…Indeed, it is well established that phosphinidene fragments are readily trapped by dienes . Despite advances from each Lammerstma and Cummins in easier‐to‐prepare phosphinidene precursors, limitations remain, most notably that the method is not catalytic. Our objective has been to leverage α‐phosphinidene elimination in the catalytic synthesis of organophosphines akin to stoichiometric PR transfer.…”

Dual Activation of Aromatic Diels–Alder Reactions

“…[5] Ar evealing example of the difference in reactivity between benzene and [5]metacyclophane [6] is the transfer of the carbene-likep hosphinideneP hP(CO) 4 from ap hosphanorbornadiene to the strained hydrocarbon by [4+ +1] cycloaddition (Scheme 1c). [8] Early semi-empirical MNDO and Xa calculations attributed the reduced HOMO-LUMO( H-L) gap in cyclophanes to the distortion of the p framework. [8] Early semi-empirical MNDO and Xa calculations attributed the reduced HOMO-LUMO( H-L) gap in cyclophanes to the distortion of the p framework.…”