Direct observation of chair and boat conformations for dibenzocycloocta-1,5-diene by nuclear magnetic resonance

Abstract

2023sponding tzg orbitals on each metal atom, then, gives three Fe-Fe bonds, one Q and two T .Concerning the evaluation of the Fe-Fe bond order in this compound, we are in agreement with Cotton' that any attempt to find a direct correlation of the metal-metal distance with bond order in this type of structures is meaningless. Therefore, it does not seem unreasonable to affirm that in the [FezH3(P3)z]+ complex cation there are three Fe-Fe interactions, some or all of which are weaker than a full bonding interaction.

Stereodynamic Investigation of Dibenzo-1,5-cyclooctadiene and 5,6,11,12-tetrahydrodibenzo[b,f] [1,4]diazocine Derivatives

“…In fact the spectrum of 2-d4 in a TB conformation should exhibit two AB patterns (eight lines) or four lines if the coupling constants were not resolved, unless the chemical shift differences for protons on the nonidentical carbons of TB are too small to be resolved. The spectrum of 2-d4 is therefore compatible with the existence of a major TB conformation and a minor C conformation in agreement with earlier suggestions for 2 (3,6).…”

“…Specifically, the conformational properties of 1,5-cyclooctadiene (1) are significantly different from that of dibenzo-l,5-cyclooctadiene (2). The stable conformation of 1 has been re~orted to be a twist boat which can undergo two dynamic processes (2) while 2 exists as a mixture of chair and boat conformations of varying proportion depending on the nature of the solvent (3). For this latter molecule, owing to spectral complexities and solubility problems, only one of the possible dynamic processes has been identified for the boat form.…”

“…method. Several investigations (5)(6)(7)(8) have shown that heteroatoms in the ring modify significantly its conformational properties and an examination of the literature has led us to anticipate a markedly different behavior for N,N'-dimethyldiazocine (3) and N,N'-diacetyldiazocine (4) because no spectral change was reported for compounds analogous to 3 (e.g. R = CH2C6H5) whereas two spectral changes were observed for 4 but none was attributed to hindered amide bond rotation.…”

Gas-phase conformations and exciton couplings in 5,6,11,12-tetrahydrodibenzo[a,e]cyclooctene

“…The conformations of 5,6,11,12-tetrahydrodibenzo[a,e]cyclooctene (THDC), also known as [2.2]-orthocyclophane, have been extensively investigated by X-ray and NMR techniques [1][2][3]. Previous theoretical studies of THDC were limited to molecular mechanics and density functional theory (DFT) calculations [3,4].…”

“…1. The twist-boat (TB) and chair (C) conformers have been observed in solution using NMR techniques [2,3]. X-ray studies show that only the C conformer is present in the crystal [1].…”