Organometallic Chemistry: Volume 31 (Specialist Periodical Reports - Organometallic Chemistry, Volume 31) - Hardcover

Hardcover

ISBN 10: 0854043381 ISBN 13: 9780854043385

Publisher: Royal Society of Chemistry, 2004

Synopsis

Organometallic chemistry is an interdisciplinary science which continues to grow at a rapid pace. Although there is continued interest in synthetic and structural studies the last decade has seen a growing interest in the potential of organometallic chemistry to provide answers to problems in catalysis, synthetic organic chemistry and also in the development of new materials. This Specialist Periodical Report aims to reflect these current interests, reviewing progress in theoretical organometallic chemistry, main group chemistry, the lanthanides and all aspects of transition metal chemistry. Volume 31 covers literature published during 2001. Specialist Periodical Reports provide systematic and detailed review coverage in major areas of chemical research. Compiled by teams of leading authorities in the relevant subject areas, the series creates a unique service for the active research chemist, with regular, in-depth accounts of progress in particular fields of chemistry. Subject coverage within different volumes of a given title is similar and publication is on an annual or biennial basis.

About this title

Excerpt. © Reprinted by permission. All rights reserved.

Organometallic Chemistry Volume 31

A Review of the Literature Published During 2001

By M. Green

The Royal Society of Chemistry

Copyright © 2004 The Royal Society of Chemistry
All rights reserved.

ISBN: 978-0-85404-338-5

Contents

Chapter 1 Theoretical Organometallic Chemistry By A.J. Bridgeman, 1, 
Chapter 2 Groups 1 and 11: The Alkali and Coinage Metals By D.J. Linton and A.E.H. Wheatley, 48, 
Chapter 3 Group 2 (Be–Ba) and Group 12 (Zn–Hg) By Dominic S. Wright, 70, 
Chapter 4 Scandium, Yttrium and the Lanthanides By John G. Brennan and Andrea Sella, 85, 
Chapter 5 Carboranes, Including Their Metal Complexes By Paul A. Jelliss, 112, 
Chapter 6 Group III: B, Al, Ga, In and Tl By Simon Aldridge, 130, 
Chapter 7 Group 14: Silicon, Germanium, Tin and Lead By Richard A. Layfield, 177, 
Chapter 8 Group 15: Phosphorus, Arsenic, Antimony and Bismuth By Matthew D. Francis, 191, 
Chapter 9 Organic Aspects of Organometallic Chemistry By Guy C. Lloyd-Jones, 209, 
Chapter 10 Complexes Containing Metal–Carbon σ-Bonds of Groups 4 and 5 (Including Multiple Bonded Species) By Jason M. Lynam, 279, 
Chapter 11 Complexes Containing Metal–Carbon σ-Bonds of the Group 7 (Including Multiple Bonded Species) By Jason M. Lynam, 289, 
Chapter 12 Organo-Transition Metal Cluster Complexes By Mark G. Humphrey and Marie P. Cifuentes, 297, 
Chapter 13 Complexes Containing Metal–Carbon σ-Bonds of the Groups Iron, Cobalt and Nickel, Including Carbenes and Carbynes By Philip J. King, 349, 
Chapter 14 Transition Metal Complexes of Cyclopentadienyl Ligands By Ian R. Butler, 393, 

CHAPTER 1

Theoretical Organometallic Chemistry

By A.J. BRIDGEMAN

1 Introduction

This chapter aims to cover theoretical and computational studies on organometallic molecules. Section 2 covers the s-block elements, Section 3 covers the p-block metals and Section 4 covers the d- and f-block metals. Clusters, carbonyls and metal-metal bonded systems containing M-C bonds are included. Cyanide complexes, metal fullerene derivatives, extended systems and organic species on metal surfaces are excluded except where calculations have been performed on model complexes designed to mimic solid state and surface chemistry.

Only a brief mention of the computational method is given. Standard abbreviations for computational methods are employed throughout. Given the plethora of basis sets available in modern computational chemistry programs and the variety of basis set designations employed by authors in this field, no description of basis sets is given. The reader should consult the original work for further details of the computational method and the basis set.

2 s-Block Metals

2.1 Structural, Spectroscopic and Mechanistic Studies. – 2.1.1 Metal Alkyls. B3LYP calculations have been used to study the structures and oligomerisation of methyllithium and tert-butyllithium (RnLin, n = 1-4; R = Me, t-Bu) and phenyllithium (PhnLin, n = 1,4) leading to good agreement with available experimental and previous computational results. Aggregation energies, computed at the B3LYP/6-311+ G(2d,p) + ZPC//B3LYP/6-31+ G* level, for the tetramers of methyllithium, t-butyllithium, and phenyllithium are -124.4, -108.6, and -117.2 kcal mol-1, respectively. B3LYP studies of the inversion of methyllithium in both tetrameric and dimeric aggregates show that inversion occurs either via dissociation of the tetramer into the dimers, passage of a four-membered-ring transition state, and association of the dimers to form the inverted tetramer, or via a nonconcerted route involving an eight-membered-ring transition state. Both routes are predicted to have similar activation energies.

The structure of the lithiated 4-isopropyl-3-methylthiomethyl-5,5-diphenyloxazolidin-2-one derivative features coordination of Li to carbonyl oxygen and an antiperiplanar arrangement of the C, Li and S, CH3 bonds, according to a B3LYP study. The Si-Li bond lengths and the unusual 29Si chemical shifts in amino-functionalized silyllithium compounds are influenced by the electronegativity of substituents located at the nitrogen centre according to RI-DFT and IGLO calculations. B3LYP, CBS-Q, CBS-QB3, G1, G2MP2, G2, G3, and G3B3 methods have been used to calculate the vibrational spectra and ionization energies of BeCH3, MgCH3 and CaCH3. The B3LYP method when used with a large basis set such as 6-311+ +G (3df, 3pd) is accurate for both vibrational frequencies and ionization energies. G2M(MP2 calculations show that the BeO + CH4 reaction proceeds by barrier-less formation of the CH4BeO complex followed by isomerization to a CH3BeOH molecule. This can dissociate without an exit barrier to BeOH + CH3 or rearrange through a high barrier to a weakly bound CH3OHBe complex. The most stable structure of lithium dimethylaminoborohydride is a dimer in which the lithium and boron atoms were bridged by two hydrogen atoms, similar to the three-center two-electron bonds in diborane according to a B3LYP study. The rotation barrier of the C-N bond in lithium acetamide is less than 10 kcal mol-1 with conjugation effects comparable to that in vinylamine, according to an MP3 and B3LYP study. The possible structures of dimers of 2-(lithiomethyl)-1-methylimidazole, and the role of THF and 1,2-dimethylimidazole in the solvation of the dimers have been investigated at the PM3 and B3LYP levels indicating that 1,2-dimethylimidazole will replace THF in the salvation sphere. The rate-limiting activated complex for the deprotonation of epoxide by chiral lithium amides is composed of two molecules of the monomer of lithium amide and one molecule of epoxide according to a B3LYP study.

The structures and vibrational frequencies of [MgC3]+ and [MgC3H]+ have been investigated at the MP2 and B3LYP levels and their energies have been computed at the G2 and CCSD(T) levels. The 2A1 ground state of [MgC3]+ has a rhombic structure. Its four-membered ring is maintained upon protonation to give the ground state of [MgC3H]+.

2.1.2 Interactions with Unsaturated Organic Systems. The stable isomers of the ferrocene-lithium cation gas-phase ion complex have been studied using the B3LYP method. The most stable isomer 1 has a Li+ bonded on top of a cyclopentadienyl ring, while in the other isomer 2 lithium binds to the central iron atom. The energy difference between the isomer is estimated to ca. 8 kcal mol-1 with an activation energy for their interconversion of ca. 2.6 kcal mol-1. The structure of ferrocene is not greatly affected by either type of coordination.

The interaction energies of the Li+, Na+ and K+ cations with the π systems benzene, toluene, ethylbenzene, and tert-butylbenzene have been calculated at the MP2 level. Induction and electrostatic interactions are the major source of the attraction. B3LYP methods have been used to model the protonation and the binding of Li+ to corannulene. A proton attaches preferentially to one carbon atom, forming a o-complex. The lithium cation positions itself preferentially over a ring. MP2 and MPW1PW91 calculations have been reported for the interaction of Na+ with phenylalanine and alanine leading to a higher affinity for the former by 5-7 kcal mol-1. The ground-state geometries of the complexes of C2H2 and C2H4 with H+, Li+, and Na+ ions have been optimized at the B3LYP and MP2 levels. Bond indices and localized MOs indicate the presence of three-centre bonding in all the complexes. In the protonated species the bonding is found to be predominantly covalent; in the Li+ and Na+ complexes the covalent interaction also plays a fairly important role. The main characters of the potential energy surface of the methylenelitho-flurosilylenoid (H2C = SiLiF) have been studied at the G2(MP2) level revealing four equilibrium structures corresponding to a π-complex, a three-membered ring, a σ-complex and a silene, and three isomerization transition states. The non-planar π-complex has the lowest energy. The cation-π complexation of oligo[(dimethylsilylene)phenylene] with alkali metal cations has been studied at the MP2 level showing that SiMe3 group but not the SiH3 group substantially increases the attraction between the cation and the π system. Significant conformational changes on the silamacrocycles occur due to complexation.

The structures and vibrational spectra of alkali metal cyclopentadienyl (CpM, M = Li, Na, K) and pentamethylcyclopentadienyl (Cp*M, M = Li, Na) complexes have been studied at the BLYP level leading to a reassignment of the IR spectra. The apparent non-VSEPR shapes of d0 complexes including the (η5-C5R5)2M (M = alkaline earth) have been reviewed identifying the roles of the metal d-orbitals and metal-ring π bonding in controlling the shape.

Li bonds to pyrenes, anthracenes and phenanthrenes with binding energies of 143,211 and 146 kJ mol-1 respectively on interstitial and edge sites according to a B3LYP study. Li dimers attached to anthracene and phenanthrene with binding energies of 200 and 146 kJ mol-1, respectively, are also predicted. The aromatic rings lose their planarity when they accommodate Li atoms. The complex formed between Na and C2H2 is very weak with large metal-ligand distances and can be considered as effectively a ground state ligand and a metal atom according to CEPA calculations. The nominally hypervalent complexes LiXCH2 (X = O or NH) are stable, residing in three potential energy minima, according to HF calculations. Two states resemble C-centered radicals carrying an ion pair, Li+[XCH2]-, and can be viewed as lithiated derivatives of hydroxymethyl (HOCH2) or aminomethyl (H2NCH2) radicals. The third state is a conventional, electrostatically bonded Li-X = CH2 complex with an essentially intact X-C double bond and the unpaired electron located at the metal atom.

The most stable structure of phenyl calcium hydride in donor solvents is dimeric, although monomers or tetramers may be present at very low or very high concentrations respectively according to a B3LYP study. Hydride bridging is favoured over phenyl bridging and the coordination number of six is predicted to be dominant for these calcium species in solution. The interaction between alkaline earth metal ions and benzene is very strong according to B3LYP and MP2 calculations. Charge transfer and induction make a significant contribution to the bonding through metal s-ring π and metal p-ring π orbital interactions. The gas-phase and solvated structures of fluorescent indicators, used for the intracellular determination of Ca2+ and Mg2+ and their coordination to these metals has been studied at the B3LYP level. Binding to the metal is enhanced by electron-donating substituents and weakened by electron-withdrawing groups on the indicator.

Conversion of carbon monoxide to formaldehyde can be catalyzed by beryllium oxide in the gas phase, according to a MP2 study. One possible mechanism involves BeO reacting with CO to form a OBeOC complex which interacts with H2 to give a BeO / H2CO complex. This decomposes to BeO and formaldehyde without an exit barrier. A second possible mechanism involves reaction of BeO with H2 followed by CO insertion into the Be-H bond of HBeOH to form HCOBeOH. This undergoes a 1,3-hydrogen shift from carbon to oxygen yielding the OBeOCH2 complex which decomposes to the final products.

3 p-Block Metals

3.1 Structural and Spectroscopic Studies. – 3.1.1 Metal Alkyls and Analogues. Alkyl, silyl, and phosphane ligands contain sp3-hybridized C, Si and P donor atoms respectively and are related to each other by the isolobal analogy. This analogy has been reviewed enabling the reactivity and bonding of these ligands to be consistently described.

BP86 calculations have been used to calculate the energies and structures of 36 different methylaluminoxane cage structures with the general formula (MeAlO)n, where n ranges from 4 to 16. By fitting to the calculated energies, a formula for the total energies of these clusters, thought to be activators in Cp2ZrMe2/AlMe3 ethene polymerization, has been devised. Topological arguments show that the clusters contain a limited amount of square faces as compared to octagonal and hexagonal ones. The lack of square faces, with their strained Al-O bonds, may explain the high molar Al:catalyst ratio required for activation. BP86 calculations have been used to obtain structures and energies of over 30 different structures with the general formula (AlOMe)n·(AlMe3)m where n ranges from 6 to 13 and m ranges between 1 and 4, depending upon the structure of the parent (AlOMe)n cage. Trimethylaluminum does not bond to methylaluminoxane for cages where n = 12 or n ≥ 14.

A comparison of inorganic and organometallic fluorides in the framework of the hard and soft arid and base principle, has been made using HF, MP2 and B3LYP calculations on alkylaluminium fluorides. A new theoretical model is proposed to put in equation form the qualitative statements of the Bent rule. The model allows the rationalization of the tendencies of bond angle variation in R2MX2 systems containing a main group metal, in terms of hybridization of the central atom and the reciprocal influence of hard and soft ligands.

The structural, electronic, and thermochemical properties of indium compounds which are of interest in halide transport and organometallic chemical vapor deposition processes, including In(CH3), In(CH3)H, In(CH3)H2, In(CH3)2, In(CH3)2H, In2(CH3)4, In(CH3, In(CH3)2CH2, In(CH3)CH2, In(CH2), (CH3)3In:NH3, (CH3)3In:N(CH3)3, (CH3)3In:N(H2)N(H2), In(CH3)2(NH) and In(CH3)(NH), have been studied by B3LYP calculations and statistical thermodynamic methods. The electronic structures of the ground and lowest lying excited state of the silicon methylidyne radical (HCSi) have been investigated at the SCF, CISD, CCDS and CCSD(T) levels. The ground and first excited electronic states, 2Π and 2Σ+ respectively, it is linear with C–Si triple bond character. The linear excited 2Σ+ state has a real degenerate bending vibrational frequency, whereas the groundstate is subject to the Renner–Teller effect and presents two distinct real vibrational frequencies. The HCSi radical is an A-type Renner–Teller molecule.Thegeometries, energies and vibrational frequencies of the X 2Π and A 2Σ+ states of the HCGe radical have been investigated at the SCF, CISD, CCSD, and CCSD(T) levels. The ground state is linear with C–Ge triple bond character. The dipole moment of HCGe is 0.122 D according to HF calculations.

HnGe(H2)+ (n = 0,1) play an important role in the unimolecular dissociation of the metastable [Ge,Hn]-/0/+ (n = 2, 3) cations according to combined mass spectrometry and CCSD(T,full) and B3LYP studies. [Ge,H2]+ could exist in one of three low lying states, 2A1 HGeH+, 2B2 Ge(H2)+ and 2B1 Ge(H2)+. The vibrational frequencies of the gauche, ortho, transoid and anti conformations of the tetrasilanes SiMe3SiX2SiX2SiMe3 (X = H, F, Cl, Br, I) have been studied at the B3LYP level. Silanes are weak Lewis acids towards neutral N and O donor Lewis bases as the energy gained by interaction is not much bigger than the energy necessary to change the geometry of the silane from the ground state to that in the complex according to a B3LYP study. The interaction between Si and the donor atoms exhibit an highly ionic character, increasing from SiH3X to SiH2X2 to SiX4 and from X = Br to Cl to F.

(Continues...)

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Edition details

• Publisher: Royal Society of Chemistry
• Publication date: 2004
• Language: English
• ISBN 10: 0854043381
• ISBN 13: 9780854043385
• Binding: Hardcover
• Edition number: 1
• Number of pages: 464
• Editor: Green M