Spin-Spin Coupling

Determination of 1J(59Co–59Co) scalar coupling constants in the tetrahedral mixed-metal cluster HFeCo3(CO)10(PCyH2)(PPh2[CH2C(O)Ph]) using COSY-type NMR experiments

“…The 1 J( 59 Co-59 Co) couplings determined previously were surprisingly very small compared to the 1 J( 59 Co-59 Co) couplings determined in this work: 1 Table 1 Parameters obtained from the analysis of the 1D 59 Co spectrum for the three nuclei, along with the results of the relaxation time measurements of cobalt nuclei, Co1, Co2 and Co3 (See Fig. 1) in the cluster HFeCo 3 (CO) 10 Table 1. not the same).…”

“…1) to obtain information about the coupling pattern between the chemically different 59 Co nuclei. This case study should demonstrate the feasibility of the NMR experiments even in the case of very broad (2.5-4.5 kHz) lines in the conventional 1D spectrum, and the determination of these coupling constants should provide very useful information on the nature of the metal-metal interactions [1].…”

“…Since its discovery in the early days of NMR spectroscopy, indirect spin-spin coupling J has been considered as an important structural parameter [1][2][3][4]. Because the coupling is mediated via bonding electrons, it provides fundamental information about the molecular structure and the connectivity of the mutually coupled nuclei.…”

Understanding NMR J‐couplings by the theory of polarization propagators

“…Given that the sign of D can be obtained when the sample is subjected to an external electric field, and the fact that the relative signs of D and J can be derived from spectra of a partially oriented molecule, the absolute sign of J can be inferred from an electricfield experiment (89). One needs to know at least the absolute sign of only one coupling constant in order to get the sign of all others in a relative way (90).…”

NMRSpectroscopy of Azo, Azoxy and Hydrazo Compounds

“…They are negative, and become more negative with increasing s character in the N−H bonding orbital, from sp 3 hybridization, as in hydrazines, to sp 2 in planar groups and to sp in linear groups. In addition to this, coupling constants to nitrogen are reduced (in absolute value) by the presence of a lone pair, with s character, since bonding and non-bonding s electrons (which approach the nucleus) give oppositely-signed contributions to the Fermi contact term which dominates the coupling 38,39 . This is why the values are small for amines, and the smallest values involve bent nitrogen, as in diazenides M−N=NH.…”