Measurement of Magnitude and Sign of Heteronuclear Coupling Constants in Transition Metal Complexes

Gottfried Otting*, Linnea P. Soler, Barbara A. Messerle

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

17 Citations (Scopus)

Abstract

Sets of specifically tailored E.COSY-type correlation experiments and double-quantum/zero-quantum (DQ/ZQ) experiments are presented which enable the determination of sign and size of small heteronuclear coupling constants across the metal center of transition metal complexes. For the octahedrally coordinated complexes, [Ru(TPM)(H)(CO)(PPh3)]+[BF4]- (1) and [Ir(TPM)(H)-(CO)(CO2CH3)]+[BF4] - (2), 14 of 15 and 15 of 15 possible two-bond scalar coupling constants across the metal center were measured, respectively, using 15N and 15N/13C enriched samples (TPM = tris(1-pyrazolyl)methane)). The reduced coupling constants 2KX-M-Y = 4π22J/(hγXγY) were found to be positive when the coupled nuclei X and Y were trans with respect to the metal center, and negative when the coupled nuclei were in cis position. The validity of this sign rule was verified for JCC, JNN, JPN, JPC, JCN, JHP, JHC, and JHN couplings. Idiosyncracies associated with 2D NMR spectra for the sign determination of coupling constants with 15N which lead to corrections for the signs of JHN, JPN, and JCN couplings reported previously are discussed.

Original languageEnglish
Pages (from-to)413-429
Number of pages17
JournalJournal of Magnetic Resonance
Volume137
Issue number2
Publication statusPublished - Apr 1999
Externally publishedYes

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