MULTINUCLEAR NMR

EDITED BY JOAN MASON The Open University Milton Keynes, Buckinghamshire, England

PLENUM PRESS • NEW YORK AND LONDON

CONTENTS

Chapter 1 Introduction 1

Joan Mason

Chapter 2 The Parameters of NMR Spectroscopy

Cynthia J. Jameson and Joan Mason

1. Nuclear Properties of the Elements and the Resonance Condition 3 2. The Nucleus in a Chemical Environment 5

2.1. The Chemical Shift and the Shielding Tensor 6 2.2. Dipolar (D) Coupling 8 2.3. Indirect Spin-Spin (/) Coupling 9 2.4. Electric Quadrupole Coupling 11 2.5. Relaxation 15

3. The Larmor Precession and the Bloch Equations 19 4. The Fourier Transform Technique 22 5. Multipulse and Multiple Resonance Techniques 25

5.1. Double Resonance Experiments 29 5.2. Techniques for Signal Enhancement 32 5.3. Techniques in Aid of Spectral Analysis and Assignment 34

6. Oriented Systems 35 6.1. High Resolution NMR Techniques for Solids 36 6.2. Experimental Determination of Tensor Components of <x, J, D, and q . . . 37

7. The NMR Time Scale 39 8. Physical Effects on the NMR Parameters 42

8.1. Medium and Temperature Effects 42 8.2. Isotope Effects 44 8.3. Effects of Paramagnetic Substances 44 References 46

Chapter 3 The Chemical Shift

Cynthia J. Jameson and Joan Mason

1. Nuclear Magnetic Shielding and the Chemical Shift 51 1.1 The Absolute Shielding Te'nsor 51 1.2. The Diamagnetic and Paramagnetic Contributions to Shielding 52 1.3. The Relationship between ap and the Nuclear Spin-Rotation Constant .. 53

xi

XU CONTENTS

1.4. Molecular Symmetry and Nuclear Magnetic Shielding 54 1.5. Absolute Shielding Scales 55 1.6. Experimental Methods of Determining the Shielding Anisotropy 57

2. Theoretical Description 59 2.1. Computational Schemes 59 2.2. Relativistic Effects 60 2.3. Approximate Calculations and Models 62

3. Patterns of Chemical Shifts 64 3.1. Chemical Shift Ranges of the Nuclei 64 3.2. Scaling of Chemical Shifts 65 3.3. General Factors in the Shielding of Main-Group and Transition Metal

Nuclei 65 3.4. Dependence of Nuclear Shielding on Charge Density, Oxidation State,

and Substituent Electronegativity 66 3.5. Correlations with Electronic Excitation and Ionization Energies 68 3.6. Substituent Effects 69

4. Correlations of Chemical Shifts with Other Molecular Properties 75 4.1. Nuclear Quadrupole Coupling Constants 75 4.2. Van Vleck Paramagnetism, and the Electronic' g Tensor 75 4.3. Spin-Spin Coupling Constants and Relaxation Times 76 4.4. Bond Properties 76

5. Shifts in Paramagnetic Systems 77 6. Effects of Intermolecular Interactions and Intramolecular* Dynamics 79

6.1. Medium Effects 79 6.2. Rovibrational Averaging and Isotope Effects 80 6.3. Dynamic Processes: Fluxional, Conformational and Exchange Equilibria 82 References 83

Chapter 4 Spin-Spin Coupling

Cynthia J. Jameson

1. General Considerations 89 1.1. Mechanisms of Spin-Spin Coupling 90 1.2. Anisotropy of the Spin-Spin Coupling 92 1.3. Methods of Determining Signs of Coupling Constants 93

2. Empirical Patterns of Coupling Constants 95 2.1. Signs and General Magnitudes of "K(XY) 96 2.2. Structural Factors Affecting lK 101 2.3. Structural Factors Affecting the Sign and Magnitude of 2K 106 2.4. Structural Factors Affecting the Sign and Magnitude of 3K 109

3. Effects of Intermolecular Interactions and Intramolecular Dynamics on Spin-Spin Coupling 110 3.1. Averaging via Rotameric Equilibria and Intramolecular Rearrangement 110 3.2. Isotope Effects 111 3.3. Chemical Exchange and Medium Effects 112

4. Theoretical Description 113 4.1. Computational Schemes 113

CONTENTS Xlll

4.2. Relative Importance of the Fermi Contact, Spin Dipolar and Orbital Terms 116

4.3. Relativistic Effects 117 4.4. Approximate Calculations and Models 118 References 123

Chapter 5 Relaxation and Related Time-Dependent Processes

Oliver Howarth

1. Importance 133 2. Definitions 134

2.1. Macroscopic Definition of 7\ and T2: Bloch Equations 134 2.2. Microscopic Interpretation 135 2.3. Nuclear Overhauser Enhancement 137 2.4. Relaxation in the Rotating Frame: Tlp 139

3. Microscopic Theory 140 3.1. Spin-Lattice Relaxation 140 3.2. Spin-Spin Relaxation 141 3.3. Dependence of Spectral Density upon Frequency 142 3.4. The Static Part V 144 3.5. More Complete Treatments 144

4. Specific Mechanisms , 145 4.1. Dipole-Dipole Relaxation 145 4.2. Scalar Interactions 148 4.3. Shielding Anisotropy 149 4.4. Spin-Rotation Interactions 150 4.5. Electric Quadrupole Interactions 150

5. Methods of Measurement 153 5.1. 7\ Measurements 153 5.2. Nuclear Overhauser Enhancement Measurements 154 5.3. T2 Measurement, and Other Uses of Spin Echoes 154

6. Line Broadening Due to Chemical Exchange 157 6.1. Ti in the Presence of Chemical Exchange , 159

7. Paramagnetic Interactions 160 7.1. Kinetics 160 7.2. Paramagnetic Contributions to Tt and T2 162

8. Two-Dimensional NMR 164 8.1. Shift-Correlation Experiments 165 8.2. /-Resolved Two-Dimensional Spectroscopy 167 References 168

Chapter 6 Hydrogen and Its Isotopes: Hydrogen, Deuterium, and Tritium

J. W. Akitt

1. Introduction 171 2. Experimental Techniques 172

XIV CONTENTS

3. Hydrogen or the Proton, or Protium 172 3.1. Strong or Weak Hydrogen Bonds 174 3.2. Ionic Solvation 174 3.3. Chemical Shifts of Adducts 176 3.4. Hydrogen on Carbon 176 3.5. Hydride Protons 177 3.6. Dynamic Processes ' 180

4. Deuterium 181 4.1. Deuterium NMR in Isotropie Liquids 181 4.2. Deuterium NMR of Liquid Crystalline Phases 183 4.3. Deuterium NMR in Solids and Heterogeneous Systems 184

5. Tritium 184 References 185

Chapter 7 The Alkali and Alkaline Earth Metals: Lithium, Sodium, Potassium, Rubidium, Cesium, Beryllium, Magnesium, Calcium, Strontium, and Barium

J. W. Akitt

1. Introduction to Groups I and II 189 2. Experimental Techniques 192 3. Aqueous Solutions of Simple Salts 195

3.1. Nuclear Relaxation 197 3.2. Chemical Shifts 203

4. Mixed and Nonaqueous Solutions of Simple Salts 205 4.1. Nuclear Relaxation 205 4.2. Chemical Shifts 206

5. Complexes Between the Cations and Various Types of Ligands 209 5.1. Complexes with Low-Molecular-Weight Compounds 209 5.2. Complexes with Synthetic Polymerie Ligands 210 5.3. Complexes with Biopolymers 210 5.4. Cations in Liquid Crystals 211

6. Group I and II Metal Organic Compounds 212 6.1. Lithium Organic Compounds 213 6.2. Beryllium Covalent Compounds 215 References 215

Chapter 8 Boron

John D. Kennedy

1. Nuclear Properties and General Considerations 221 2. Trigonal and Tetrahedral Compounds 224

2.1. Chemical Shifts 224 2.2. Coupling Constants 227 2.3. Relaxation Studies 231

CONTENTS XV

3. Polyhedral Boron-Containing Species 231 3.1. General Considerations 231 3.2. Boron Chemical Shifts 233 3.3. Coupling Constants 245 3.4. Relaxation Times 248 3.5. Polyhedral Species—Nuclei Other than Boron 250 3.6. Fluxionality 252 References 253

Chapter 9 Aluminum, Gallium, Indium, and Thallium

J. W. Akitt

1. The Nuclear Properties of AI, Ga, and In, the Quadrupolar Nuclei 259 2. Aluminum 259

2.1. Operational Techniques 260 2.2. Aluminum-27 NMR Parameters 261 2.3. Some Observations on the Parameters 277

3. Gallium 279 3.1. Operational Techniques 279 3.2. Gallium-69 and Gallium-71 NMR Parameters 279

4. Indium 283 4.1. Indium-115 NMR Parameters 283

5. Thallium 285 References 287

Chapter 10 Carbon 293

Brian E. Mann

Chapter 11 Silicon, Germanium, Tin, and Lead

John D. Kennedy and W. McFarlane

1. Introduction 305 2. Experimental Aspects 305 3. Chemical Shifts 307

3.1. Isotope Effects 307 3.2. Solvent and Temperature Effects 307 3.3. Chemical Shift Patterns 307 3.4. Factors Influencing Shielding 309 3.5. Chemical Shifts in Specific Classes of Compound 314

4. Coupling Constants 318 4.1. One-Bond Couplings 318 4.2. Two-Bond Couplings 323 4.3. Three-Bond Couplings 325

XVI CONTENTS

5. Relaxation Behavior 326 6. Miscellaneous and Solid State Work 327

References 328

Chapter 12 Nitrogen

Joan Mason

1. Nitrogen NMR Spectroscopy 335 1.1. Nitrogen Referencing 335 1.2. Medium Effects 337 1.3. Solid State Measurements in High Resolution 337 1.4. Isotope Effects and Tracer Studies 340

2. 15N NMR Spectroscopy 340 2.1. 15N Relaxation and NOE Factors 340 2.2. Sensitivity Enhancement 344

3. 14N NMR Spectroscopy 344 3.1. 14N Quadrupolar Relaxation 345

4. Patterns of Nitrogen Shielding 349 4.1. Nitrogen NMR Criteria of Structure 353 4.2. Inorganic Azines and Azenes 355 4.3. Coordination Shifts 356

5. Nitrogen Spin-Spin Coupling 357 6. Dynamics 362 7. Biomolecules 362

References 362

Chapter 13 Phosphorits to Bismuth

Keith R. Dixon

1. Phosphorus-31 369 1.1. Introduction 369 1.2. Spin Lattice Relaxation (7^) 371 1.3. Chemical Shifts 7 374 1.4. Coupling Constants 390

2. Arsenic-75, Antimony-121,123 and Bismuth-209 397 References 398

Chapter 14 Oxygen

H. C. E. McFarlane and W. McFarlane

1. Introduction 403 2. Experimental Aspects 403 3. Chemical Shifts 404 4. Spin Coupling 408

CONTENTS XV11

5. Relaxation Behavior 410 6. Applications 411 7. The Solid State 412

References 412

Chapter 15 Sulfur, Selenium, and Tellurium

H. C. E. McFarlane and W. McFarlane

1. Introduction 417 2. Sulfur 417 3. Selenium and Tellurium 421

3.1. Chemical Shifts 421 3.2. Coupling Constants 429 3.3. Relaxation Behavior 431 3.4. Applications 431 References 432

Chapter 16 Fluorine

Cynthia J. Jameson

1. 19F NMR Measurements 437 2. 19F Chemical Shifts 438

2.1. Absolute Shielding Scale 438 2.2. Empirical Patterns of 19F Nuclear Shielding 440 2.3. Anisotropy of the 19F Shielding Tensor 442

3. Spin-Spin Coupling Involving 19F 442 4. 19F Relaxation 445

References 445

Chapter 17 The Quadrupolar Halides: Chlorine, Bromine and lodine

J. W. Akitt

1. Introduction 447 2. Experimental Techniques 448 3. NMR Parameters 448

3.1. Covalent Compounds 448 3.2. Ionic Solutions 455 References 458

Chapter 18 The Noble Gases

Cynthia J. Jameson

1. Introduction 463 2. 129Xe NMR Studies of Bonding and Structure of Xenon Compounds 463

W i l l CONTENTS

2.1. 129Xe Chemical Shifts 466 2.2. Spin-Spin Coupling to Xenon 469

3. Probing Nonspecific Intermolecular Interactions with Noble Gas Nuclei . . . . 473 3.1. Medium Shifts 473 3.2. Relaxation Times 473 References 475

Chapter 19 Early Transition Metals, Lanthanides and Actinides

Dieter Rehder

1. Introduction 479 2. Group Illb 480

2.1. Scandium 480 2.2. Yttrium 482 2.3. Lanthanum 483 2.4. The Lanthanides 486 2.5. Actinium and the Actinides 486

3. Group IVb: Titanium, Zirconium, and Hafnium 487 4. Group Vb 488

4.1. Vanadium 488 4.2. Niobium 493 4.3. Tantalum 497

5. Group VIb 497 5.1. Chromium 497 5.2. Molybdenum 499 5.3. Tungsten 505

6. Group Vllb 507 6.1. Manganese 507 6.2. Technetium 511 6.3. Rhenium 512 References 512

Chapter 20 Group VIII Transition Metals

R. J. Goodfellow

1. Introduction 521 2. Observation 521

2.1. Relaxation Behavior 522 2.2. Methods of Observation 526

3. Chemical Shifts 531 3.1. Evaluation of Chemical Shifts 531 3.2. Results 534 3.3. Theoretical Approaches 539 3.4. Empirical Correlations 547 3.5. Effects of the Molecular Environment and Isotopes 548

CONTENTS XIX

4. Spin-Spin Coupling 551 4.1. Sign Determinations 552 References 554

Chapter 21 Post-Transition Metals, Copper to Mercury

R. J. Goodfellow

1. Introduction 563 2. Observation 563

2.1. 63Cu and 65Cu 564 2.2. 67Zn 564 2.3. 107Ag and 109Ag 565 2.4. m Cd and 113Cd 566 2.5. 197Au 567 2.6. 199Hg and 201Hg 568

3. Chemical Shifts 569 3.1. Results 569 3.2. Discussion 579

4. Spin-Spin Coupling 582 4.1. Sign Determinations 584 References 584

Chapter 22 NMR Spectroscopy in Bioinorganic Chemistry

Henry W. E. Rattle

1. Introduction 591 2. Some Examples of Biological Applications: Isotope Shifts in 31P NMR 591 3. Sodium Transport Through Membranes Using 23Na Resonance 593 4. Active Site Interactions in Fluorine-Labeled a-Chymotrypsin 595 5. 113Cd Studies of Alkaline Phosphatase 596 6. 31P NMR in Living Tissue 597 7. Ion Binding to Cytochrome c Studied by Nuclear Magnetic Quadrupole

Relaxation 598 8. Deuterium Label Studies of Membranes 599 9. Direct Determination of Correlation Times in Enzyme Complexes Involving

Monovalent Cations and Paramagnetic Centers 600 Index of Reviews 601 References 603

Chapter 23 Biomedical NMR

Joan Mason

1. Biomedical NMR 605 2. NMR Imaging 606

XX CONTENTS

3. Localized NMR Spectroscopy 610 4. Further Applications 611

References 613

Symbols and Abbreviations 615

SI Units and Fundamental Constants 619

Appendix: NMR Properties of the Elements 623

Index 631

i