ISBN: 0-8247-0478-9 This book is printed on acid-free paper Headquarters Marcel Dekker, Inc 270 Madison Avenue, New York, NY 10016 tel: 212-696-9000; fax: 212-685-4540 Eastern Hemisphere Distribution Marcel Dekker AG Hutgasse 4, Postfach 812, CH-4001 Basel, Switzerland tel: 41-61-261-8482; fax: 41-61-261-8896 World Wide Web http:/ /www.dekker.com The publisher offers discounts on this book when ordered in bulk quantities For more information, write to Special Sales/Professional Marketing at the headquarters address above Copyright  2001 by Marcel Dekker, Inc All Rights Reserved Neither this book nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, microfilming, and recording, or by any information storage and retrieval system, without permission in writing from the publisher Current printing (last digit): 10 PRINTED IN THE UNITED STATES OF AMERICA Preface This book is intended to fill a gap in the literature by covering a broad range of topics in computational organometallic chemistry Two objectives were foremost in putting together this volume First, pedagogical aspects are emphasized throughout The particular challenges inherent in reliable modeling (quantum or classical) in organometallic chemistry are discussed, and strategies for addressing these challenges are offered Second, ‘‘how-to’’ aspects are complemented with applications-oriented material covering a wide spectrum of research areas, including catalysis, medicine, organic synthesis, actinide chemistry, and so forth The first goal will assist those who may have limited experience in computational organometallic chemistry research upon entering this exciting and dynamic field The second objective will provide motivation for undertaking such an intellectual journey Computational Organometallic Chemistry has been written to be accessible to a general scientific audience These pages will provide upper-division undergraduate students and graduate students with useful lessons that can be employed in their future scientific endeavors, while the applications chapters will spark future research contributions Similarly, senior researchers, academic and industrial, who may wish to bring their energies to bear on this field will find both iii iv Preface motivation and suitable background to so To accomplish these ambitious goals, an internationally recognized group of experts has been assembled, each focusing on his or her particular area of expertise within this growing field of science Thomas R Cundari Contents Preface Contributors iii ix Introduction Thomas R Cundari Recipe for an Organometallic Force Field Per-Ola Norrby Computational Approaches to the Quantification of Steric Effects David P White 39 The Accuracy of Quantum Chemical Methods for the Calculation of Transition Metal Compounds Michael Diedenhofen, Thomas Wagener, and Gernot Frenking 69 v vi Contents Nondynamic Correlation Effects in Transition Metal Coordination Compounds Kristine Pierloot 123 Quantitative Consideration of Steric Effects Through Hybrid Quantum Mechanics/Molecular Mechanics Methods Feliu Maseras 159 HIV Integrase Inhibitor Interactions with Active-Site Metal Ions: Fact or Fiction? Abby L Parrill, Gigi B Ray, Mohsen Abu-Khudeir, Amy Hirsh and Angela Jolly Cyclometallation of a Computationally Designed Diene: Synthesis of (Ϫ)-Androst-4-ene-3,16-dione Douglass F Taber, James P Louey, Yanong Wang, and Wei Zhang Rhodium-Mediated Intramolecular C–H Insertion: Probing the Geometry of the Transition State Douglass F Taber, Pascual Lahuerta, James P Louey, Scott C Malcolm, Robert P Meagley, Salah-eddine Stiriba, and Kimberly K You 185 205 217 10 Molecular Mechanics Modeling of Organometallic Catalysts David P White and Warthen Douglass 237 11 Titanium Chemistry Mark S Gordon, Simon P Webb, Takako Kudo, Brett M Bode, Jerzy Moc, Dmitri G Fedorov, and Gyusung Chung 275 12 Spin-Forbidden Reactions in Transition Metal Chemistry Jeremy Noel Harvey 291 13 Oxidative Addition of Dihydrogen to M(PH3)2Cl, M ϭ Rh and Ir: A Computational Study Using DFT and MO Methods Margaret Czerw, Takeyce K Whittingham, and Karsten Krogh-Jespersen 14 The Electronic Structure of Organoactinide Complexes via Relativistic Density Functional Theory: Applications to the 323 Contents Actinocene Complexes An(η8-C8H8)2 (An ϭ Th–Am) Jun Li and Bruce E Bursten vii 345 15 Pi Bonding in Group 13–Group 15 Analogs of Ethene Ashalla McGee, Freida S Dale, Soon S Yoon, and Tracy P Hamilton 381 16 Main Group Half-Sandwich and Full-Sandwich Metallocenes Ohyun Kwon and Michael L McKee 397 Index 425 Contributors Mohsen Abu-Khudeir, B.S Department of Chemistry, The University of Memphis, Memphis, Tennessee Brett M Bode, Ph.D Applied Mathematical Sciences, Ames Laboratory, Iowa State University, Ames, Iowa Bruce E Bursten, Ph.D Department of Chemistry, The Ohio State University, Columbus, Ohio Gyusung Chung, Ph.D Department of Chemistry, Konyang University, Chungnam, Korea Thomas R Cundari, Ph.D Department of Chemistry, Computational Research on Materials Institute, The University of Memphis, Memphis, Tennessee Margaret Czerw, B.A Department of Chemistry, Rutgers, The State University of New Jersey, New Brunswick, New Jersey ix 414 Kwon and McKee the calculation of metallocenes A good comprehensive review of basis sets is provided in the chapter by Feller and Davidson in Reviews in Computational Chemistry (75) Since the nature of C(Cp)–E bonding ranges from highly ionic to covalent, small basis sets, such as STO-3G and 3-21 G, may result in significant BSSE (basis set superposition error) Previous calculations indicate that at least double-zeta plus polarization basis sets, such as 6-31G*, should be applied to main group metallocene calculations For example, Waterman and Streitweiser found a considerable effect of the basis set on the CH bending angle of CpLi at the HF level (44) In an HF and DFT study of Cp 2Li, Kwon and Kwon (20) found that adding polarization functions to the basis set improved relative energies and bond distances in conformers and that adding diffuse functions to the basis set had an effect on the CH bending angle Basis set requirements for atoms beyond the third row of the periodic table are different from the elements with lower atomic number For heavier metals, such as Ba and Pb, relativistic effects become important, and core electrons must be treated differently from valence electrons The effective core potential (ECP) can be used to handle the core electrons of these heavier atoms effectively The ECPs and associated basis sets of Hay– Wadt (76), Stevens and coworkers (77), and Stuttgart–Dresden ECP (78) are widely used and already implemented in many computational chemistry packages A good review of using ECPs is provided in two chapters in Reviews in Computational Chemistry, vol (79) The main advantage of using ECPs plus valence basis sets rather than all-electron basis sets is that the former consider relativistic effects effectively and require less computer time But it should be noted that these larger basis sets should be accompanied by electron-correlated methods in order to obtain reliable results It is also noted that the addition of the polarization function for the Cp ligand is required in order to get a correct bent conformation for Cp 2Ca (28) Population Analysis Methods It is easy to understand the nature of bonding between Cp ligand and main group elements using available population analysis methods Among them, Mulliken population analysis and natural population analysis (NPA) (50) have been widely used to calculate orbital and bonding populations and partial atomic charges of main group metallocenes It should be noted that the values from these population analyses not have physical meanings but rather give an interpretation Mulliken population analysis is strongly basis set dependent Because of this, the Mulliken population analysis fails to produce meaningful results when the basis set includes diffuse functions Mulliken population analysis overestimates the electron density on alkali metals and thus underestimates the polar character of the carbon–metal bond (80) In contrast, NPA gives a more realistic picture almost independent of the basis set Natural population analysis indicates about 80–90% ionic character for the C–Li bond in general for organolithium compounds (80) Main Group Half- and Full-Sandwich Metallocenes 415 Another way to produce atomic charges is electrostatic charge analysis, which assigns point charges to fit the computed electrostatic potential at points on the van der Waals surface This is also less basis set dependent and gives a good description of partial charges for molecules with polar interactions CHelpG (81) and Merz–Kollman–Singh (MKS) (82) charge analyses are well-known electrostatic charge methods and can be compared with Mulliken and NPA charge methods Vibrational Frequencies and Nuclear Magnetic Resonance Chemical Shift Calculations Since experimental observations may be difficult or even impossible for some main group metallocenes, theoretical calculations of physical properties may provide an important source of information Vibrational frequencies play an important role in characterizing the potential energy surface (PES) and can be used to identify minima among the possible structural alternatives Thus, calculated normal vibrational modes can be used to characterize stationary points on the PES in order to distinguish local minima, which have all real frequencies, from saddle points, which have one imaginary frequency It must be noted that frequency calculations are valid only at stationary points on the potential energy surface, which means that frequency calculations must be done on optimized structures Also, a frequency calculation must use the same theoretical level and basis set as the optimized geometry (otherwise the structure would not correspond to a stationary point) Vibrational frequencies can also be used to make zero-point corrections (ZPCs), which are necessary to make accurate predictions when only small energy differences separate different hapticities Nuclear magnetic resonance is a powerful tool for characterizing main group metallocenes, since it can often reveal information about fluxionality among different isomers However, it has been known that due to the nonrigid structure and the free rotation of Cp rings with respect to the principal C axis of main group metallocenes, NMR chemical shifts are often difficult to measure and interpret when there are no available experimental data for comparison Thus, accurate calculation of absolute chemical shieldings (relative to the calculated absolute chemical shielding of a known standard) can be compared with experimental spectra to help elucidate the exact hapticities of metallocenes Many ab initio and DFT approaches to the NMR chemical shift calculations have become available in the last decade, supported by the improvement of computer hardware and program algorithms Among known efficient techniques for calculating NMR chemical shifts, the individual gauge for localized orbital (IGLO) (83) and gauge-including atomic orbital (GIAO) (84,85) methods have been widely used during the last decade The most important factor is to obtain reliable equilibrium geometries at the electron-correlated levels, since calculated chemical shifts are highly de- 416 Kwon and McKee pendent on the geometrical environments Since it is known that the HF method is not always reliable, electron correlation methods might be preferable for computing chemical shifts MP2 or DFT methods seem to be adequate for this purpose, especially DFT, which is more efficient in terms of computer time and disk space than MP2 in calculating chemical shifts Usually, it is recommended to use gradient-corrected or hybrid functionals (such as B3LYP) for the DFT calculation It should also be noted that basis sets at least as large as 6-31G* must be used in computing chemical shifts Substituted Cyclopentadienyl Ligand Effects on the Metallocene The sterically bulky pentamethylcyclopentadienyl (Cp*) ligand has successfully been used to synthesize metallocenes, where the simpler cyclopentadienyl group led to polymerization (86) Thus, many Cp*2 E systems have been characterized experimentally in monomeric form, such as Cp 2*Ca and Cp *2 Si From ab initio calculations of Cp 2Ca and Cp*2 Ca, it has been shown that adding ten methyl ˚ groups on the Cp ligands reduced the Cp(centroid)–Ca distance by only 0.01 A (28,73) Therefore, the often-simplifying approximation of replacing Cp* with Cp in theoretical calculations is not expected to introduce a large discrepancy between theory and experiment Also, B3LYP calculations on Cp 2Si and Cp 2*Si suggest that methyl substitutions on Cp ligand not cause any significant influence on the electronic and geometrical structures of metallocenes (37) Model Calculations This section provides some model calculations of main group metallocenes to compare different theoretical methods Optimized geometrical parameters for the Cp 2Li anion at various levels of theory are shown in Table The superiority of the DFT method over HF and semiempirical methods is most striking in the prediction of geometrical parameters Semiempirical methods overestimate the CH bending angle as well as the C–C distances in Cp rings compared to the DFT and experimental results The calculated distances in Cp– Li at B3LYP/631G* and B3LYP/6-31G** levels are very close to experiment In a comparison of different basis sets (Table 4), it can be seen that including diffuse functions in the basis set results in longer a C–Li bond distance, and adding p functions on hydrogen atoms has little influence on the Cp 2LiϪ anion geometry Table represents the optimized geometrical parameters of Cp 2Mg at various computational levels The PM3 and HF methods predict slightly longer C– Mg distances compared to experiment and B3LYP/6-31G* Similar to the Cp 2LiϪ anion, including diffuse functions in the basis set results in larger C–Mg bond distances, while adding p functions on hydrogen atoms has little influence on the geometry of Cp 2Mg Main Group Half- and Full-Sandwich Metallocenes 417 TABLE Optimized Geometrical Parameters for Cp 2LiϪ Anion at Various Theoretical Levels (distance in A˚, angle in degrees) Theoretical level MNDO/d PM3 HF/6-31G* HF/6-31ϩG* HF/6-31G** B3LYP/6-31G* B3LYP/6-31ϩG* B3LYP/6-31G** Exptl datab a b C(Cp)–Li Cp–Li C–C C–H C–H bending anglea 2.323 2.367 2.390 2.399 2.390 2.348 2.356 2.349 1.974 2.033 2.069 2.079 2.070 2.015 2.024 2.016 2.008 1.439 1.424 1.406 1.408 1.406 1.417 1.419 1.417 1.362 1.086 1.089 1.076 1.076 1.076 1.086 1.086 1.085 6.50 5.48 0.06 Ϫ0.49 0.13 Ϫ0.27 Ϫ1.06 Ϫ0.17 The negative value of CH bending angle indicates inward bending X-ray diffraction data TABLE Optimized Geometrical Parameters for Cp 2Mg at Various Theoretical Levels (distance in A˚, angle in degrees) Theoretical level C(Cp)–Mg Cp–Mg C–C C–H C–H bending anglea PM3 HF/6-31G* HF/6-31ϩG* HF/6-31G** B3LYP/6-31G* B3LYP/6-31ϩG* B3LYP/6-31G** Exptl data 2.407 2.383 2.385 2.382 2.364 2.366 2.363 2.339b 2.304c 2.079 2.058 2.061 2.058 2.030 2.032 2.030 2.008b 1.977c 1.425 1.411 1.412 1.411 1.424 1.425 1.423 1.091 1.073 1.073 1.073 1.084 1.084 1.083 6.51 1.62 1.47 1.61 1.29 0.97 1.28 a The negative value of CH bending angle indicates inward bending Electron diffraction data c X-ray diffraction data b 418 Kwon and McKee TABLE Optimized Distances of Cp–E for LiCp, LiCp*, MgCp, [MgCp*]ϩ, AlCp, and AlCp* at Various Theoretical Levels (distance in A˚, angle in degrees) LiCp LiCp* MgCpϩ MgCp*ϩ AlCp AlCp* PM3 HF/6-31G* B3LYP/6-31G* 1.956 2.007 2.039 2.058 2.173 2.197 1.765 1.748 1.908 1.888 2.050 2.008 1.730 1.717 1.881 1.864 2.065 2.022 The effects caused by methyl substitution (Cp → Cp*) on the main structural features of metallocenes are shown in Table Comparison of calculated Cp–E distance between Cp-containing half-sandwich metallocenes and Cp*-containing half-sandwich metallocenes suggests that methyl substitutions on the Cp rings has little affect on Cp–E distances This fact is also supported by previous calculations of Cp 2Ca, in which optimized geometrical parameters are in good agreement with the experimental data on Cp 2*Ca (28) One of the interesting features for main group metallocenes is electron distribution between main group elements and Cp rings We have evaluated atomic charges and bond populations on the basis of some useful partitioning schemes for the total electron density distributions, such as Mulliken population analysis, NPA, CHelpG, and MKS, and results are shown in Tables and Calculated atomic charges of different elements, such as Li, Mg, and Al, shows TABLE Calculated Atomic Charges of Some HalfSandwich and Full-Sandwich Metallocenes at the B3LYP/6-31G*/ /B3LYP/6-31G* LiCp LiCp* Cp 2LiϪ MgCpϩ MgCp*ϩ Cp 2Mg AlCp AlCp* Cp 2Alϩ Q(Li) Q(Li) Q(Li) Q(Mg) Q(Mg) Q(Mg) Q(Al) Q(Al) Q(Al) Mulliken NPA CHelpG MKS 0.154 0.176 0.034 0.679 0.615 0.310 0.155 0.112 0.531 0.902 0.916 0.906 1.746 1.717 1.757 0.629 0.657 1.817 0.439 0.499 0.306 1.025 1.060 0.367 Ϫ0.069 Ϫ0.169 0.233 0.451 0.540 0.252 1.073 1.174 0.401 0.011 Ϫ0.074 0.209 Main Group Half- and Full-Sandwich Metallocenes 419 TABLE Calculated Mulliken Bond Populations and Wiberg Bond Indices of C(Cp)–E for Some Half-Sandwich and FullSandwich Metallocenes at the B3LYP/6-31G*/ / B3LYP/6-31G* LiCp LiCp* Cp 2LiϪ MgCpϩ MgCp*ϩ Cp 2Mg AlCp AlCp* Cp 2Alϩ Mulliken bond population Wiberg bond index from NPA 0.097 0.104 0.058 0.129 0.128 0.102 0.036 0.035 0.115 0.038 0.032 0.017 0.069 0.099 0.045 0.138 0.123 0.197 positive charges, as expected The values of electrostatic charges are between those of Mulliken and NPA charges Mulliken charges overestimate the polarity of main group elements, while NPA and electrostatic charges give a reasonable interpretation of the electron distribution of main group elements Mulliken bond populations for metallocenes of Li and Mg show that there is a certain covalent interaction between C(Cp) and E, which is somewhat controversial given that these metallocenes have a large amount of ionic bonding character between C(Cp) and E On the other hand, the Wiberg bond indices (WBI), which are included in the NBO analysis, shows a reasonable description of C(Cp)–E bonding Thus, the C(Cp)–Al bonding is predicted to be stronger than C(Cp)–Li and C(Cp)–Mg bonding, which explains why Group 13 metallocenes have larger amount of covalent bond character between carbon and the central atom When a Cp ligand is replaced by Cp*, the Mulliken bond populations and WBI are changed very little, which implies that methyl substitution on the Cp ring should not significantly influence the nature of bonding of metallocenes CONCLUSIONS While metallocenes are often thought to be entirely in the domain of transition metal chemistry, we have shown that main group chemists have a legitimate claim as well The lack of d orbital participation in the metal–ligand bonding may result in less thermodynamic stability but does not preclude the possibility of novel structural motifs or future ‘‘real-world’’ applications Computational 420 Kwon and McKee chemistry is expected to play a very active role in the development of this field, calculating properties of known compounds and predicting properties of unknown compounds Even at the present stage of computer software and hardware, it can be expected that the calculation of main group metallocene potential energy surfaces will give the experimentalist clues for the successful synthesis of new compounds We hope that this chapter provides an introduction and motivation to continued explorations in this field Happy hunting! RECENT DEVELOPMENTS A series of Group 14 metallocenes with substituted Cp rings [C 5Me 4(SiMe 2But)] was recently reported (87) Single-crystal X-ray structural analysis of each metallocene (E ϭ Ge, Sn, Pb) showed that the mixed alkyl- and silyl-substituted Cp rings are parallel for all three metallocenes (in contrast to most Group 14 with unsubstituted Cp rings) Theoretical calculations at the DFT level indicated that the preference of parallel Cp rings over bent ones is due to the SiR substituent on the Cp rings, which lowers the a*1g orbital (stereochemically active lone pair) below the e 1u orbital REFERENCES C Elschenbroich, A Salzer Organometallics Weinheim: VCH Verlagsgesellschaft, 1989 G Wilkinson, M Roseblum, MC Whiting, RB Woodward J Am Chem Soc 74:2125– 2126, 1952 P Jutzi J Organomet Chem 400:1–17, 1990 MA Beswick, JS Palmer, DS Wright Chem Soc Rev 27:225–232, 1998 (a) P Jutzi, N Burford In: A Togni, RL Halterman, eds Metallocenes New York: Wiley-VCH, 1998, pp 3–54 (b) P 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11:361–373, 1990 82 BH Besler, KM Merz Jr, PA Kollman J Comput Chem 11:431–439, 1990 83 W Kutzelnigg Isr J Chem 19:193–200, 1980 84 HF Hameka Mol Phys 1:203–215, 1958 85 R Ditchfield Mol Phys 27:789–807, 1974 86 R Blom, J Boersma, PHM Budzelaar, B Fischer, A Haaland, HV Volden, J Weidlein J Acta Chem Scand A40:113–120, 1986 87 SP Constantine, H Cox, PB Hitchcock, GA Lawless Organometallics 19:317–326, 2000 Index Actinide contraction, 357 Agostic, 163, 164 AIDS (acquired immunodeficiency syndrome), 185 AIMPs (ab initio model potentials), 71, 73, 126 All-electron basis sets, 113, 276, 286, 414 Allylation, 248 (-)-Androst-4-ene-3,16-dione, 205, 213 Angular overlap model, 143 Austin method (AM1), 410 Avian sarcoma virus (ASV), 195 Avoided crossing, 296 B3LYP, 7, 17, 18, 74, 93, 266, 284, 311, 313, 324, 384, 406, 409, 416 Basis set superposition error (BSSE), 414 Bent’s rule, 389 Binding affinity, 196 BINOL, 215 Blue copper proteins, 147 BLYP, 307, 313, 324, 413 BP86, 74, 76 Buckingham potential, 43, 44 CASPT2 (complete active space— second order perturbation theory), 125, 126, 129, 139, 151, 283 CASSCF (complete active space SCF), 124, 133, 143, 151, 277, 284, 312 Catalysis, 95, 323 CCSD(T)-coupled clusters, 70, 74, 76, 94, 125, 277, 281, 284, 311, 325, 340, 349, 384 C-H insertion, 217 CHelpG, 33 425 426 CHIRAPHOS, 244 Cone-angle profile, 51 Cone-angle radial profile (CARP), 52, 53 Conformational searching, 240, 263 Conical intersections, 295 Correlation energy, 146 Correlation functional, 72 CpRh(CO), 49 Cr(CO)5L, 45, 46, 61, 65 Cr(NO)4, 152 Crossing point, 308 Crossing seam, 309 Crystal distortion energy, 16 CT (charge transfer), 130, 143 Cycloaddition, 34, 99 Cyclometallation, 205 Cyclozirconation, 207 DFT (density functional theory), 18, 247, 284, 316, 323, 324, 336, 340, 347, 349, 372, 405, 410 Dihydrogen complexes, 337 Dihydroxylation catalyst, 178, 180, 248 Dimerization, 394 Dirhodium carboxylates, 218, 226, 227, 233 Distributed data interface (DDI), 278 DKH (Douglas-Kroll-Hess), 80 Docking, 196 D-orbital splitting, 292 Double group, 362 Double shell effect, 125, 130, 147, 155 DPT (direct perturbation theory), 83, 88 DV-Xa (discrete variational Xa), 349 Dynamic correlation, 125, 347, 349 ECP (effective core potential), 18, 70, 73, 76, 194, 113, 276, 286, 307, 315, 325, 384, 389, 414 Electron transfer, 298 (ϩ)-Elemol, 210 Epoxidation, 104, 248 Fe(CO)5, 293 Ferrocene, 345 Index Flavones, 188 Force field, Fourier transform, 197 Fully optimized reaction space (FORS), 277, 279 Genetic algorithms, 239 GIAO (gauge-including atomic orbital), 108, 109, 113, 415 Group 16 ligands, 88 (-)-Haliclonadiamine, 209 Heme, 165, 300 Hessian, 17, 27 Hexacarbonyls, 74, 109, 148, 151 HF (Hartree-Fock), 194, 285, 384, 410 HIV-1 (human immunodeficiency virus), 185 HIV-1 protease, 185, 186, 250 Hydrocyanation, 250 Hydrodesulfurization, 250 Hydroformylation, 250, 251 Hydrogenation, 240, 241, 251, 382, 394 Hydrosilation, 275 Hydroxylation, 251 IGLO (individual gauge for localized orbital), 108, 109, 113, 415 Inert-pair effect, 407 Integrase, 185 Integrated molecular orbital/molecular mechanics (IMOMM), 160, 170 Integrated molecular orbital/molecular orbital (IMOMO), 160 Ionization potentials, 135 Ir(biph)(X)(QR3)2, 175 Jahn-Teller effect, 383 Kohn-Sham orbitals, 350 Koopmans’ theorem, 135 Lagrange multipliers, 25, 26 Landau-Zener formula, 296 LDA (local density approximation), 351 Lennard-Jones potential, 42, 43 Index Ligand association, 300 Ligand design, 252 Ligand dissocation, 300 Ligand field theory (LFT), 143, 146 Ligand repulsive energy (Er), 40, 44 Light-induced excited spin-state trapping, 299 Linear free energy relationship (LFER), 39 LMCT (ligand-to-metal charge transfer), 130, 143, 153 Macromodel, 32, 33 MCPF (modified coupled-pair functional), 125 MCSCF (multiconfiguration SCF), 277, 278, 283, 317, 356 Metallocarbohedrenes, 275 Metallocene, 397 Metathesis, 253 MINDO/3, 64 Minimum energy crossing point, 309, 310, 318 Miroiterations, 169, 170 MLCT (metal-to-ligand charge transfer), 130, 148, 153, 155 MM2, 41, 64, 65 MM3, 32, 41, 42 MM4, 42 MMP2, 45, 65 MNDO (modified neglect of differential overlap), 64, 410 MnRe(CO)10, 61 Monte Carlo, 45, 197, 240, 263 MP2 (Moller-Plesset second order perturbation theory), 7, 17, 70, 93, 123, 125, 277, 281, 324, 349, 356, 406, 408, 410, 411 Mulliken population analysis, 389, 407, 408, 414 Natural orbital occupation numbers, 283 NDDO (neglect of diatomic differential overlap), 410 Nephelauxetic effect, 146 Neural networks, 239 427 Newton–Raphson, 19, 24, 25 Ni(CO)3L, 49 Nitrido complexes, 90, 92 NMR chemical shifts, 108, 415 Noble gas complexes, 83 Nonadiabatic chemistry, 291, 294 Nonbonded parameters, 21 Nonbonded potential, 42 Nondynamic electron correlation, 123, 124, 140, 147, 155 Nonlocal-DFT, 70 Nonlocal exchange functional, 72 NPA (natural population analysis), 414 Olefin complex, 244 ONIOM, 160 Organoactinide, 345 Ortho-metalated phosphines, 229 Oxidative addition, 102, 301, 331 Parameter tethering, 28 Parameterization, 12, 238, 248, 249 Partial optimization, 307, 308 Pauli Hamiltonian, 352 Pd-olefin complex, 33 Penalty function, 20, 22, 23, 25, 26, 30 Pentacarbonyl complexes, 83 Phosphido complexes, 90 Phosphine complexes, 86, 241, 330, 407 Pi bonding, 381, 382, 395 PM3 (parameterization method 3), 33, 192, 410, 411, 416 Points on a sphere (POS), 14, 32, 33 Polymerization, 253 Potential energy surface (PES), 293, 294, 415 Protein DataBank, 198 PW91, 353, 355, 359, 368 Quantum mechanics-guided molecular mechanics (Q2MM), 13, 18, 34 Quantum mechanics/molecular mechanics (QM/MM), 34, 159, 161, 169, 181 428 Reductive elimination, 102 Restricted active space SCF (RASSCF), 134, 139, 151, 153 Restricted open shell Hartree-Fock (ROHF), 139, 279 Reverse transcriptase, 185, 186 Rhenium peroxides, 104 Rhodium, 217 Rhodium carbene, 219, 221 Rotational barriers, 385 Ru(bipy)3, 32 Ru(CO)2(PR3)3, 173 Salicylhydrazines, 190, 191, 198 Sandwich complexes, 346, 368, 399, 407 Scalar relativistic effects, 352 Self-consistent field (SCF), 65, 356 Semiempirical methods, 416 SHOP (Shell higher olefin process), 265, 267 Silane polymerization, 275 Simplex, 19,23 Singular value decomposition, 25, 26 6-31G*, 266, 416 Slater determinant, 294, 382 Slater-type orbitals (STOs), 351, 352 Solid angles, 53, 56 Spin crossover, 299 Spin orbitals (spinors), 362 Index Spin-forbidden reactions, 291, 292, 297, 318 Spin-orbit coupling, 129, 281, 285, 293, 295, 352, 362 Sum-over-states (SOS), 108 Taddol, 215 Thiazolothiazepines, 189, 191 3-21G*, 192 Tolman’s cone angle, 40, 49, 50, 65 Tricarbonyl complexes, 83 Universal Force Field (UFF), 45, 238, 266 Uranocene, 346, 359 Urey-Bradley, 41 Water-gas shift reaction, 97, 100 Weight factors, 20 Werner complexes, 143, 153 Wilkinson’s catalyst, 323 X-ray crystallography, 15 Zeolites, 239, 255, 262, 264, 265 Zerner’s intermediate neglect of differential overlap (ZINDO), 208, 211, 214 Zero order regular appoximation (ZORA), 80, 88 Ziegler-Natta polymerization, 239, 240, 256, 258, 260, 262, 275 ... user-friendly, computational chemistry packages Another trend, and a very welcome one at that, in modern computational organometallic chemistry is in some respects a return to the roots of computational chemistry. .. present volume Computational chemistry and organometallic chemistry are, almost by definition, interdisciplinary endeavors The latter exists at the interface between inorganic and organic chemistry, ... the ‘‘how’’ and ‘‘why’’ of organometallic chemistry, with less concern for ‘‘how much.’’ For a while, it seemed that the only trend in computational organometallic chemistry was to be more quantitative,