Premium
Application of HMQC spectroscopy to the observation of the metal resonance in polymetallic compounds: the effect of multiple‐metal spin transitions
Author(s) -
Heaton B. T.,
Iggo J. A.,
Podkorytov I. S.,
Tunik S. P.
Publication year - 2004
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1428
Subject(s) - chemistry , metal , rhodium , spin (aerodynamics) , spectral line , chemical shift , nuclear magnetic resonance spectroscopy , transition metal , coupling constant , spectroscopy , crystallography , resonance (particle physics) , analytical chemistry (journal) , nuclear magnetic resonance , stereochemistry , atomic physics , organic chemistry , physics , particle physics , quantum mechanics , astronomy , catalysis , thermodynamics
Multiple‐metal spin transitions which distort the HMQC spectra of rhodium carbonyl clusters are discussed. These effects are seen whenever the detector nucleus, e.g. 13 C or 31 P, couples to more than one metal spin and are not restricted to detector ligands occupying edge‐ or face‐bridging sites. These effects are illustrated in, but not limited to, the 13 C‐{ 103 Rh} and 31 P‐{ 103 Rh} HMQC spectra of [Rh 6 (CO) 15 L], (where L = P(4‐F‐C 6 H 4 ) 3 ), [Rh 4 (CO) 11 {P(OPh) 3 }], [Rh 6 C(CO) 15 ] 2 − and [Rh 2 (carboxylate) 2 PPh 3 ]. The effect is to modulate the intensity and position of the correlations in the metal dimension; cross peaks are displaced from the true chemical shift, additional cross peaks are seen and the intensity of the coherences varies as a function of the preparation delay, d 2 , and coupling constant, and may go to zero at the conventional value of 1/(2 J ). Analyses of the relevant spin systems are given together with experimental strategies to overcome these effects. Copyright © 2004 John Wiley & Sons, Ltd.