Nuclear Magnetic Resonance

BY B. E. MANN

1 Introduction

Following the criteria established in earlier volumes, only books and reviews directly relevant to this chapter are included, and the reader who requires a complete list is referred to the Specialist Periodical Reports 'Nuclear Magnetic Resonance', where a complete list of books and reviews is given. Reviews which are of direct relevance to a section of this Report are included in the beginning of that section rather than here. Papers where only 1H n.m.r. spectroscopy is used are only included when the 1H n.m.r. spectra make a non-routine contribution, but complete coverage of relevant papers is still attempted where nuclei other than protonsare involved. In view of the greater restrictions on space, and the ever growing numbers of publications, many more papers in marginal areas have been omitted. This is especially the case in the sections on solid-state n.m.r. spectroscopy, silicon and phosphorus.

Two books have appeared: 'N.m.r. spectroscopy of organometallic compounds: testing the use of n.m.r. in the chemistry of organic compounds of heavy nontransition metals', and a two-volume book 'N.m.r. of newly accessible nuclei' with volume 1 containing 'Chemical and biochemical applications, while volume 2 contains 'Chemically and biochemically important elements'. These two volumes contain chapters on 'N.M.R. of less common nuclei' and numerous specific chapters which are referenced in the relevant section of this Report.

A number of reviews have appeared including 'Physical methods and techniques. N.m.r. spectroscopy', 'N.m.r. in the eighties: new nuclei, new pulses',' 'N.m.r of other nuclei', 'Multinuclear n.m.r studies of naturally occurring nuclei,' 25Mg, 43Ca, and 113Cd n.m.r. studies of regulatory calcium binding proteins', 'N.m.r. of the first transition series nuclei (scandium to zinc), 'Reaction of heteropolymolybdic acid with metal ions', 'Synthetic and spectroscopic studies of haems and haem proteins', 'New potentialities of n.m.r spectroscopy in the study of catalysis', 'N.m.r. spectroscopy of molten salts', 'Experimental access to the molecular and electronic structures of organo-f-element complexes by n.m.r. spectroscopy', 'Biological aspects of 23Na imaging', and 'N.m.r. studies of intracellular metal ions in intact cells and tissues.

A number of papers have been published which are too broadly based to fit into a later section and are included here. Isotopic effects on X-nuclei screening and X-H(D) scalar coupling in XH4 and XO4 have been determined for 14N, 15N, 27Al, 51V, 53Cr, 69Ga, 71Ga, and 99Tc. An n.m.r. relaxometer for measuring T1 and T2 for 1H, 7Li, and 23Na has been described. The effect of ro-vibration on the chemical shifts of metals has been examined. For d transition-metal ions, 59CO, 99Ru, 103Rh, and 195Pt n.m.r. chemical shifts have been parameterised. Rules have been discussed for predicting arrangements of point charges that give a zero electric field gradient at a point and applied to quadrupolar relaxation. CNDO calculations have been performed on Cr(CO)6, Fe(CO)5, and Ni(CO)4 to determine charge densities, which are consistent with 13C and 17O chemical shifts. 15N Chemical shifts and coupling constants have been determined for terminal N2 complexes of Mo, W, Re, Fe, Ru, Os, and Rh. The 15N shielding showed periodic variation with the central metal, increasing with increasing atomic number. The n.m.r. chemical shifts of some metalloporphyrins have been calculated. 13C n.m.r spectroscopy has been used to demonstrate intramolecular co-ordination of quinone to some capped metalloporphyrins. 1J(M13C) values, taken from the literature for compounds of 199Hg, 207Pb, and 119Sn, increase with increasing hybridisation of the carbon atom attached to the metal. A method of obtaining the valence and non-valence components of the coupling constants was discussed.

2 Stereochemistry

This section is subdivided into ten parts which contain n.m.r. information about Groups IA and IIA and transition-metal complexes presented by Groups according to the Periodic Table. Within each Group, classification is by ligand type.

Complexes of Groups IA and IIA. — Two reviews have appeared: 'Alkali metals' and 'Magnesium-25 and calcium-43'.

The essentially identical 1J(13C, 1H) for the central carbon atom in the contact and solvent-separated ion pairs of some allyl alkali-metal compounds indicates that this coupling constant is not dependent on out-of-plane distortion at C-2. The solution structure of PhLi has been determined from T1 measurements using 7Li/6Li and 1H/2H isotopic substitution methods. For some 6Li and 13C sulphur- and selenium-substituted organolithium derivatives, 1J(13C, 6Li) is observed. 1J(13C, 1H) and 1J(13C, 13C) decrease and 1J(77Se, 13C) increases upon lithiation. The 7Li n.m.r. spectrum of [Li(μ-PR2)]2 is a triplet, while a doublet is observed for Li(PR2)(tmed). The 31P n.m.r. spectra were also reported. 7Li n.m.r. spectroscopy has been used to detect different Li species in human serum. N.m.r. data have also been reported for M- (M = Na, Rb; 23Na, 87Rb), [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (7Li, 11B) [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (13C), 31p), [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (13C), Li(NHAr)(tmed) (7Li) [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (13C).

The 25Mg n.m.r spectra of Grignard reagents depend on concentration and temperature. The 1H and 13C n.m.r. spectra of Mg(anthracene1 indicate maximum interaction with the 9 and 10 position. 1H n.O.e. and 13C n.m.r measurements have been used to determine the structure of 9-((THF)nMg}-10-(A1R1R2H)-anthracene. Using 500 MHz 1H n.m.r spectroscopy, the signals of chlorophyll a have been assigned. 1H T1 measurements and ring-current shifts have been used to investigate dimer structure of chlorophyll. The complexation of Mg2+ and Cd2+ by guanosine nucleotides has been investigated by 31P n.m.r. spectroscopy. Intracellular calcium measurement has been described using 19F n.m.r. signals of fluorine labelled chelators. Prothrombin fragment 1-membrane interactions have been studied using 43Ca n.m.r. spectroscopy. The n.m.r. quadrupole - coupling constants for 43Ca bound to either a-lactalbumin or trypsin is significantly smaller than for EF-hand Ca2+ binding proteins. The 113Cd chemical shifts indicate that only O ligands are involved in metal-ion binding. The conformation of the barium perchlorate complex of valinomycin has been investigated using 13C n.m.r. spectroscopy. N.m.r. data...