Nuclear Magnetic Resonance Spectroscopy

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 proton are 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, namely 'Introduction of Multinuclear N.M.R.: Theory and Application and 'Nuclear Magnetic Resonance in Solutions of Inorganic Substances'.

Several relevant reviews have been published, including 'Multinuclear n.m.r. methods for the in situ characterisation of chemical species', 'Patterns of nuclear magnetic shielding of transition-metal nuclei', 'Modern n.m.r. spectroscopy of organolithium compounds', which contains examples of 1H, 6Li, 7Li, and 13C n.m.r. spectroscopy, 'Transition metal pentadienyl chemstry', 'Studies on mixed-metal clusters containing cobalt, ruthenium and rhodium and on the catalytic reactivity of homogeneous ruthenium-rhodium and ruthenium-cobalt systems', 'The use of multinuclear n.m.r. to study CunLimRn+m', 'Naked phosphorus atoms and units in transition-metal compounds, and 'Measurement of cation compartmentalization in tissue by high resolution metal cation n.m.r.'

A number of papers have been published which are too broadly based to fit into a later section and are included here. A high-pressure probe for n.m.r. studies of homogeneous catalyst has been developed. This probe was then used to obtain line-narrowing for 14N, 33S, and 55Mn for solutions in supercritical fluid solvents. The heavy atom effect on 13C chemical shifts has been discussed in terms of a relativistic contribution. The microscopic theory of nuclear quadrupolar relaxation has been applied to liquid melts of salts. N.m.r. chemical shifts and shift derivatives upon bond length extension have been calculated for the first and second row hydrides. The extended Hückel method has been used to calculate [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] and [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] for CH4, TiCl3Me, Mn(CO)5Me, and ZnMe2 as a function of CH distance and MCH angle. The positive geminal coupling found for TiCl3Me was shown to be caused by the small TiCH angle. [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] has been determined for a range of (n4- diene) transition metal complexes. The solution conformation of M(octa-ethylchlorin), M = Mg, Ni, Cu, Zn, has been determined using 1H and 13C n.m.r. spectroscopy. Geminal [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] of transition metal complexes of [SnCl3]- have been correlated with orbital characteristics of specific occupied and unoccupied molecular orbitals. J(119Sn-99Ru) values were also discussed. 19F and 31P n.m.r. spectra have been reported for [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII], M = Mn, Fe, Co, Ni. 31P n.m.r. spectra of [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII], M = Fe, Co, Ni, Cu, Ag, Au, Zn, Cd, Hg, Ga, In, and Tl, have been recorded. Theoretical calculations have been used to explain 1H and 13C chemical shifts of metal acac, tfac, and hfac derivatives. 19F T1 values for SF6, MOF6, WF6, and UF6 have been recorded and used to obtain intermolecular potentials.

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. — The nuclear spin and magnetic moment of 11Li have been measured by optical pumping of a fast atomic beam. 6Li-1H n.O.e. measurements have been performed on compounds such as Li(thf)3AlH3{C(SiMe3)3}. 7Li and 27Al n.m.r. spectra were also recorded. The 13C chemical shift parameters have been presented for carbon atoms α, β, γ, and δ to the lithium atom and were based on the chemical shift of 14 6Li enriched alkyl lithium compounds. A 6Li-13C n.m.r. chemical shift correlation has been described and applied to 3,4-dilithio-2,5-dimethyl-2,4-hexadiene. 6Li-1H HOESY and 13C n.m.r. spectroscopy have been used to show that some Li-H distances are short. The 13C n.m.r. spectrum of [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] has been analysed. The 7Li and 31P n.m.r. spectra of [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] shows J(31-7Li) = 36 Hz. The 119Sn n.m.r. spectrum of [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] was also recorded. 1H, 6Li, 7Li and 13C n.m.r. spectra, including J(13C-13C), have been used to investigate the structure of [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] M = Li, K. Variable temperature 13C n.m.r. spectroscopy on isotopically perturbed samples shows that allyl Na and allyl K have symmetric structures, but allyl Li is an unsymmetric dimer in thf. The solvent induced 13C shifts in indenyl lithium have been interpreted. 6Li, 13C, and 15N n.m.r. spectroscopy has been used to study lithiated cyclohexane phenylimine and three species were detected. The quadrupole splitting constant in lithum arylamides, phenolates, and enolates and for several organolithium compounds in ether and tertiary amine solvents have been determined from 7Li and 13C T1 data. The excess charge in [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] is delocalised into the phenyl ring according to 1H, 7Li, 13C, and 15N n.m.r. data. N.m.r. data have also been reported for [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (13C), [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (7Li) N-lithiocarbazole, (13C), and [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (7Li, 31P).

The 7Li linewidth in 7LiC1 in D2O has been determined as ca. 0.04 Hz. The results were used to put a limit on gravitational coupling to electromagnetism. 7Li n.m.r. spectroscopy has been used to study normal human erythrocytes. 1H...