Application of HMQC spectroscopy to the observation of the metal resonance in polymetallic compounds: the effect of multiple-metal spin transitions

✍ Scribed by B. T. Heaton; J. A. Iggo; I. S. Podkorytov; S. P. Tunik

• Publisher: John Wiley and Sons
• Year: 2004
• Tongue: English
• Weight: 448 KB
• Volume: 42
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1428

✦ Synopsis

Abstract

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.