Critical evaluation of the dependence of 3JHH couplings on bond order and bond length in conjugated carbocyclic molecules. Evidence for a steric effect on 3JHH

Transformation of an [Fe(η2‐N2H3)]+Species to π‐Delocalized [Fe2(μ‐N2H2)]2+/+Complexes

“…The 15 The magnitude of the three-bond HH coupling is consistent with a trans configuration, and can furthermore be used as a probe for the extent of NN activation. [12] For example, 3 J(H,H) = 28.0 Hz for [{(CO) 5 Cr} 2 (trans-m-N 2 H 2 )], [13] which has an NÀN bond distance of 1.25 , [14] The solid-state structure of 3 was obtained and its core atoms are shown in Figure 1 (see Supporting Information for complete structure). Both Fe centers have similar metrical parameters, and adopt a distorted trigonal bipyramidal geometry, with the approximate equatorial plane defined by two phosphorous and one nitrogen atom.…”

“…The magnitude of the three-bond HH coupling is consistent with a trans configuration, and can furthermore be used as a probe for the extent of NN activation. [12] For example, 3 J (H,H) = 28.0 Hz for [(CO) 5 Cr] 2 ( trans -μ-N 2 H 2 ), [13] which has an N-N bond distance of 1.25 Å, [14] while 3 J (H,H) = 9.4 Hz for [(η 5 -C 5 Me 4 H) 2 ZrI] 2 ( trans -μ-N 2 H 2 ), which has an N-N bond distance of 1.414(3) Å. [9b] Hence, the observed 3 J (H,H) coupling in 3 is most consistent with a single bond.…”

Straining strained molecules. III. The spectral and mutagenic properties and an alternate synthesis of diaceperylene and dicyclopenta[1,2,3-cd:1′,2′,3′-lm]perylene

“…acenapthene (26), acenaphthylene (26), pyracylene (2), dihydropyracylene (2), perylene (25), and 1 and 2 [with calculated shifts].…”

Straining strained molecules. II. The syntheses and spectral properties of some ace-bridged naphthalenes

“…8) 32, 6 8.03, (69). An alternative explanation is of course that the deshielding observed is due to the sum of all the ring currents involved and is larger for 12 than 2 because of the increase in rings.…”