Nuclear Magnetic Resonance Spectroscopy

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.

A number of reviews have appeared including 'N.m.r. and inorganic chemistry', 'N.m.r. of metal nuclides. Part II: the transition metals', 'Scalar spin-spin interactions of nuclei in diamagnetic coordination compounds', 'Steady state techniques for low sensitivity and slowly relaxing nuclei, 'Effect of substituents in RnM organometallic compounds and changes in direct constants of the 1J (M,13C) spin-spin interaction', 'Nuclear magnetic resonance spectroscopy of organic analytical reagents and their metal complexes,' 'Nuclear magnetic resonance spectroscopy of chlorophylls and corrins', 'Structural properties of calmodulin, an intracellular calcium ion-modulator protein, as revealed by different n.m.r. techniques, and 'Elucidation of the structure and metal sequestering properties of metallothionein by nuclear magnetic resonance'.

A number of papers have been published which are too broadly based to fit into a later section and are included here. The general magnitudes of n.m.r. isotope shifts have been discussed. Recycled flow n.m.r. spectroscopy has been used to investigate 13C, 15N, 29Si, 31P, and 113Cd n.m.r. spectra of model compounds. Scalar relaxation of heteronuclear multiple quantum coherences and relative\ signs of nuclear spin-spin coupling constants have been examined and applied to J(35Cl,1H) and J(35Cl,29Si), which have opposite signs in SiHC3. The 13C magnetic shielding in cyclopentadienyl complexes has been calculated by eliminating effects due to charge. The results for the first overlapping sphere Zα-SW chemical shift calculations reproduce the trends in 13C n.m.r. measurements for the CO, CS, CN, and C5H5 ligands in Ni(CO)4, Cr(CO)5CS, and Fe(5CH 5)(CO)2CN. 13C n.m.r. spectra of RN=CHCH=NR in various coordination modes have been discussed with particular reference to the Ru3(CO)12 /RN=CHCH=NR system. Metal-allyl bonding has been studied by using 1J(13C,13C). 1J (13C,13C) varies between 59 Hz for Li or K(C3H5) down to 40 Hz for some transition-metal complexes. N.m.r. data have also been reported for complexes of ethylenediphosphinetetraacetic acid (31P), 1,3-bis(2-hydroxyphenyl)-1,3-propanedione (13C), and 7-methylguanosine (13C).

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. — 1H, 7Li, and 13C n.m.r. spectroscopy has been used to show that Li[Ph2CCLiCPh] has this structure. A similar investigation has been carried out using J(13C, 13C) and J(13C,6Li) on isotopically enriched materials. Solutions of alkylaryllithium salts chelated by Me2NCH2CH2NMe 2 or Me2N(CH2CH2 NMe)3Me have been studied by 7Li n.m.r. spectroscopy. Good correlations between the chemical shift and the pK of the parent hydrocarbon were found. The 13C n.m.r. spectrum of 6Li-benzovalene shows 1J (13C,6Li), 1H, 7Li, and 13C n.m.r. spectra of MSiMenPh3-n M = Li, K, have been discussed in terms of π-polarization of the phenyl rings. At low temperatures J(29Si,6 Li) and J(29Si,7Li) in Ph3-n MenSiLi are observed. A wide range of unsaturated hydrocarbons have been reduced by alkali metals in liquid ammonia, and detected in situ by 13C n.m.r. spectroscopy. K- in [K(15-crown-5)2]+K- in Me2O has been observed by 39K n.m.r. spectroscopy. The 7Li and 31P n.m.r. spectra of LiPR2 show 1J(31P, 7Li). The relaxation times T1 of free Na+ and Na+ bound to macromolecules have been determined simultaneously by the two-dimensional n.m.r. method by using 23Na n.m.r. spectroscopy. The 39K n.m.r. spectrum of K/Cs alloy dissolved in 12-crown-4 or 15-crown-5 shows the presence of K-. N.m.r. data have also been reported for EtCMeCHCH2Li (13C), 1-(Me2N)-3-lithiopropane [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]

A 13C n.m.r. study of the biosynthesis of bacteriochlorophyll using 18O has shown that 18O is incorporated into all possible sites. Similarly the incorporation of 1-[1-13C]glutamate and [2-13C]-glycine into bacteriochlorophyll has been studied by 113C n.m.r. spectroscopy. The structure of a bacteriochlorophyllide dimer in solution has been determined by 1H n.m.r. spectroscopy. 13Ca and 113Cd n.m.r. spectroscopy has been used to investigate structural differences in the two calcium-binding sites of the porcine intestinal calcium-binding protein. Shift reagents have been employed for 43Ca n.m.r. studies of calcium-binding proteins. Quadrupole coupling constants have been determined for 43Ca and 25Mg in M(acac)2, M = Ca, Mg. 13C T1 measurements were also performed. N.m.r. data have also been reported for Mg(C5H5)(CH2Bu t) (13C), Mg(C5H3 R1R2)2 (13C), [Mg(anthracene)]n (13C), 1,2-dimethylanthracenemagnesium (13C), Mg-inosine-5-monophosphate (13C), Be(R1 COCHCOR2)2 (13C, 19F), and MUO2(OAc)4 (M = Mg, Ba, Co, Zn; 19F).

Complexes of Groups IIIA and IVA, the Lanthanides, and Actinides. The 89Y n.m.r. spectra of some organoyttrium complexes such as (MeC5H4)3Y(thf) have been reported, and vary over a range of 400 p.p.m. For (MeC5 H4)3Y(thf), J(89Y,1 H) = 27 Hz. The 17O chemical shifts are related to the lowest electronic transition energies of UO2 complexes. 1H, 17O, and 79Br n.m.r. spectra have been recorded for aqueous-organic solutions of the perbromates of uranyl and neptunyl and the coordination of water and anion investigated. The 19F relaxation in gaseous UF6, WF6, and MoF6 is consistent with relaxation dominated by spin-rotation interaction. The possibility of the use of 19F n.m.r....