Nuclear Magnetic Resonance Spectroscopy

BY B. E. MANN

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 been published which are relevant to this review:- 'Multinuclear N.m.r.', edited by J. Mason, and 'N.m.r. Spectroscopy of Organic Analytical Reagents and Their Complexes with Metal Ions' by L.A. Fedorov.

Several relevant reviews have been published, including 'Theory of N.m.r. and chemical shift of metal nucleus', 'Spectroscopic characterization of inorganic and organometallic complexes by metal and high-pressure n.m.r.', 'N.m.r. studies of metal complexes', 'N.m.r. of metal nucleus. Applications to coordination chemistry and bioinorganic chemistry', 'Recent developments in n.m.r. spectroscopy of organometallic compounds', 13C Chemical shifts of bridging CH2 groups', 'Protein metalloen-zymes', 'Structure and bonding of dinitrogen complexes', General experimental techniques and compilation of chemical shift data', which contains a review of 31P n.m.r. spectra, and 'N.m.r. of inorganic compounds and clay minerals'.

A number of papers have been published which are too broadly based to fit into a later section and are included here. A theoretical interpretation of the effect of geometrical isomerism on metal chemical shifts has been published and applied to 59Co chemical shifts. Calculations have shown that a difference of a few mHz should be observed in the metal resonance frequency of enantiomers, containing 195Pt or 207Pb. Inverse two-dimensional INEPT 1H-(M) and 31P-(M) measurements have been used to observe 57Fe, 61Ni, 103Rh, and 183W in a variety of organometallic compounds. A T1 method has been described for distinguishing classical hydrides with terminal M-H bonds from nonclassical hydrides with H-H as well as M-H bonds, and has been applied to a range of transition metal di- and poly-hydrides. It has been observed that carbene α-CH 1H n.m.r. signal shifts to low frequency when there is an agostic interaction. The 13C n.m.r. data were also recorded. High field 1H and 13C n.m.r. spectroscopy has been shown to be valuable in determining the structure of mixed metal clusters containing carbyne or ketenylidene bridges. The interaction between two anthracenocryptands with K+, Ag+, and T1+ has been studied by 13C n.m.r. spectroscopy. 13C N.m.r. spectroscopy has been used to study the complexation of transition metal ions with 1-phenylazo-2-naphthol. 1H and 13C n.m.r. spectroscopy has ben used to characterize complexes of penicillins with metal ions. 15N N.m.r. spectroscopy has been used to differentiate between the linear and bent geometry of diazenido complexes. Complexes of AlIII, InIII, ScIII, TlIII, NiII, ZnII, and CdII with hexadentate Schiff base ligands have been characterized by 1H n.m.r. spectroscopy, including COSY. A correlation has been found between the meso carbon bond angle and 1J(13C-1H) in some diamagnetic metal complexes of octaethylporphyrin. A 13C n.m.r. method has been described which determines the number of atoms in chelate rings of coordination compounds. 13C N.m.r. data have been reported for Ba2+, [UO2]2+, Ni2+, and Zn2+ complexes of 1,2-C6H4(N=CHC6H3 (OH-2)-3-(OCH2CH2)n)2O. 77Se N.m.r. spectra of a wide range of co-ordination compounds containing unsaturated dithio-, thioseleno-, or diseleno-ligands have been reported with NiII, ZnII, SeII, and TeII as the central atoms.

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. — A review entitled 'Structure and dynamic behaviour of organolithium compounds' has appeared. T1 has been measured for 7Li and 8Li in liquid lithium. 1H and 7Li n.m.r. spectroscopy has been used to investigate cryptated lithium carbanions. 1J(29Si-13C) and 1J(13C-1H) have been determined in Me3SiCH2Li. The 7Li n.m.r. spectrum of Bun (py)Li.2py shows three signals at low temperature. The 13C n.m.r. spectrum was also recorded. 6Li-(1H) HOESY has been used to detect short Li-H distances and to make 1H spectral assignments for 1,8-dilithio-1,2-diphenylhex-1-ene, which exists as a monomer-dimer equilibrium mixture in thf. Selective 6Li-(13C) double resonance and two-dimensional double quantum based shift correlation experiments have been used to establish 6Li-13C connectivities in Li2-((Me3Si)2CSO2C6H4). The complexation of polybutadienyllithium with various electron donors has been studied by n.m.r. spectroscopy. 7Li and 13C n.m.r. spectra of PhLi and several methyl substituted phenyl lithiums have been recorded in the presence of coordinating solvents and the relative amounts of dimeric and tetrameric aggregates determined. 7Li and 13C n.m.r. spectra have been used to study the behaviour of several aryl-lithium compounds containing a N,N-Me2N substituent in the presence of coordinating solvents. Differences in J(13C-6Li) have been used to demonstrate that [(2,6-(MeO)2C6H3)Li]4 is two interacting dimers. Complete dissociation of [2-ButS-C6H4Li(tmeda)ln into monomers in solution is indicated by J(13C-6Li). Close Li-H contacts were detected using 6Li-1H two-dimensional HOESY n.m.r. spectra. The formation of triple anions in thf solutions of 2-MeCHLiC5H4N has been demonstrated by 7Li n.m.r. spectroscopy. N.m.r. data have also been reported for [LiCH(CN)2(hmpt)]n, (13C) [(PhCHNCHPh)Na(pmdeta)]n, (13C), ButCH=CLiC[equivalent to]CBut, (13C), metallated hydrazone cryptates, (6Li, 13C, 23Na) and [Li2C10H8)2, (6Li, 13C).

The structure of [(Pri2NH)Li((cyclohex-1-enyl)PhN)2Li(NHPri2)] has been investigated by 6Li, 7Li,...