Guest Editor's Foreword
NMR spectroscopy in transition metal and organometallic chemistry
Organometallic and coordination chemistry have flourished ever since the advent of NMR spectroscopy because of the fast and non-invasive access that this spectroscopic technique offers to detailed structural information on the sub-molecular scale concerning new, exciting organometallic compounds and catalysts. Nuclei such as 59 Co having been scouted from the early days of NMR (the chemical shift was discovered when determining the gyromagnetic ratios of a number of elements and it was found that it varied as a function of the chemical composition of cobalt complexes) and transition metal nuclei (both spin-1/2 and higher spin) have been investigated ever since. It is only natural that the metal atom itself, being the scaffold of the organometallic molecule or coordination compound, often featuring catalytic activity by virtue of vacant coordination sites, has been sought as the subject of NMR studies. Large parts of organometallic chemistry and catalysis take place on moderately sized molecules in solution, hence most applications are found in high-resolution NMR; however, solid-state NMR has become increasingly important for the field of research.
A few (quadrupole) nuclei (such as the palladium and iridium isotopes) have been particularly evasive and remain extremely difficult to measure to date. For many low-abundance (spin-1/2) nuclides with low receptivities, such as 57 Fe, 103 Rh, 109 Ag, 117/119 Sn, 183 W and 187 Os, the advent of polarization transfer techniques has paved the way to their faster and more routine acquisition. People such as A. Bax, C. Brevard, R. Benn and W. von Philipsborn have contributed tremendously to the implementation of polarization transfer NMR techniques to the 'less-common' nuclei, after the theoretical general descriptions by R. R. Ernst, A. A. Maudsley and L. M ΓΌller. Later, its routine accessibility and the availability of probes and customer-friendly hardware and software have resulted in the participation of many interested practitioners. Recently, the development of gradient-enhanced techniques, notably ge-HMQC variants, has boosted applications to main group and transition metal chemistry even more.
More readily measured nuclei such as 19 F and 31 P and quadrupole nuclei such as 6 Li, 49 Ti, 51 V, 55 Mn and 59 Co feature in many organometallic compounds. Their study is indispensable for the elucidation of structures and for the advancement of knowledge in the field of coordination chemistry and organometallic chemistry, which are closely related to catalysis, biocatalysis and materials science.
It is therefore timely to devote a special issue to this topic, the publication date of which has been chosen close to the 75th birthday of one of the protagonists and founders of the field of transition metal NMR and its applications to organometallic chemistry: Wolfgang von Philipsborn, Emeritus and Honorary Professor at the University of Z ΓΌrich.
This Special Issue covers a range of contributions from several areas, some close to and others further away from organometallic and coordination chemistry: a review concerning 103 Rh NMR of the last 15 years; DFT calculations of 49 Ti and of 57 Fe NMR chemical shifts; 51 V NMR of vanadate binding to proteins; 57 Fe NMR of ferrocenes; 57 Fe-13 C coupling in ferrocenes; 59 Co NMR of cobalt complexes in lyotropic liquid crystals; 103 Rh NMR of a series of rhodium(I) compounds; multiple-metal spin transitions (e.g. 31 P-103 Rh-103 Rh) in HMQC applied to polymetallic compounds; 31 P and 109 Ag NMR of organosilver complexes; weak donor-acceptor interactions probed by 1 H-117 SnJ-HMQC spectroscopy; 15 N and 195 Pt studies of organoplatinum compounds; 6 Li and 13 C NMR of methyllithium aggregates; PGSE diffusion and 1 H-19 F HOESY studies of rhodium complexes; 19 F NMR of isomeric Co complexes; 31 P MAS NMR of ruthenium-diphosphine-diamine compounds; 31 P-105 Pd CP/MAS study of palladium phosphine compounds; and solid-state 109 Ag CP/MAS NMR of silver complexes.
Many thanks go to the authors, who agreed to contribute papers concerning various subjects in the exciting field of NMR spectroscopy in transition metal and organometallic chemistry, which has resulted in this Special Issue celebrating the 75th anniversary of Professor Wolfgang von Philipsborn.
Finally, let me wish you enjoyable and inspiring reading!