Fundamentals of H2 Binding and Reactivity on Transition Metals Underlying Hydrogenase Function and H2 Production and Storage

The fact that a new text book introducing the essentials of computational chemistry contains more than 500 pages shows impressively the grown and still growing size and importance of this field of chemistry. The author’s objectives of the book, using his own words, are “to provide a survey of computational chemistry its underpinnings, its jargon, its strengths and weaknesses that will be accessible to both the experimental and theoretical communities”. This design as a general introduction into computational chemistry makes it an alternative to Andrew R. Leach’s well-established “Molecular Modeling” (Prentice Hall) and Frank Jensen’s “Introduction to Computational Chemistry” (Wiley), although the latter focuses on the theory of electronic structure methods. Cramer’s “Essentials” covers force field and molecular orbital theory, Monte Carlo and Molecular Dynamics simulations, thermodynamic and electronic (spectroscopic) property calculation, condensed phase treatment and a few more topics. Moreover, the book contains thirteen selected case studies sexamples taken from the literature sto illustrate the application of the just presented theoretical and computational models. This especially makes the text book well suited for both classroom discussion and self-study. Each chapter of “Essentials” covers a main topic of computational chemistry and will be briefly described here; all chapters are ended by a bibliography and suggested additional readings as well as the literature references cited in the text. In chapter 1 the author defines basic terms such as “theory”, “model”, and “computation”, introduces the concept of the potential energy surface and provides some general considerations about hardware and software. Interestingly, the first equation occurring in the text is not Schro ̈dinger’s equation, as is the case for most computational chemistry introductions, but the famous Einstein relation. The second chapter deals with molecular mechanics. It explains the different potential energy contributions, introduces the field of structure optimization, and provides an overview of the variety of modern force fields. Chapter 3 covers the simulation of molecular ensembles. It defines phase space and trajectories and shows the formalism of, and problems and difference between, Monte Carlo and molecular dynamics. In chapter 4 the author introduces the foundations of molecular orbital theory. Basic concepts such as Hamilton operator, LCAO basis set approach, many-electron wave functions, etc. are explained. To illuminate the LCAO variational process, the Hu ̈ckel theory is presented with an example. Chapter 5 deals with semiempirical molecular orbital (MO) theory. Besides the classical approaches (extended Hu ̈ckel, CNDO, INDO, NDDO) and methods (e.g., MNDO, AM1, PM3) and their performance, examples are provided from the ongoing development in that still fascinating area. Ab initio MO theory is presented in chapter 6; the basis set concept is discussed in detail, and, after some considerations from an user’s point of view, the general performance of ab initio methods is explicated. The next chapter covers the problem of electron correlation and gives the most prominent solutions for its treatment: configuration interaction, theory of the multiconfiguration self-consistent field, perturbation, and coupled cluster. Practical issues are also discussed. Chapter 8’s topic is density functional theory (DFT). Its theoretical foundation, methodology, and some functionals as well as its pros and cons compared to MO theory are presented together with a general performance overview. The next two chapters deal with charge distribution, derived and spectroscopic properties (e.g., atomic charges, polarizability, rotational, vibrational, and NMR spectra), and thermodynamic properties (e.g., zero-point vibrational energy, free energy of formation, and reaction). The modeling of condensed phases is addressed in chapters 11 (implicit models) and 12 (explicit models), which closes with a comparison between the two approaches. Chapter 13 familiarizes the reader with hybrid quantum mechanical/molecular mechanical (QM/MM) models. Polarization as well as the problematic implications of unsaturated QM and MM components are discussed, and empirical valence bond methods are also presented. The treatment of excited states is the topic of chapter 14; besides CI and MCSCF as computational methods, transition probabilities and solvatochromism are discussed. The last chapter deals with reaction dynamics, mostly adiabaticskinetics, rate constants, reaction paths, and transition state theory are section topics here sbut also nonadiabatic, introducing curve crossing and Marcus theory in brief. The appendix is divided into four parts: an acronym glossary (which is very helpful), an overview of symmetry and group theory, an introduction to spin algebra, and finally a section about orbital localization. A rather detailed index ends the book. The “Essentials” writing style fits the fascinating topic: one reads on and on andssurprise! sanother chapter has been absorbed. The text is complemented by a large number of black and white figures and clear tables, mostly self-explanatory with descriptive captions. The use of equations and mathematical formulas in general is well-balanced, and the level of math should be understandable for every natural scientist with some basic knowledge of physics. There are only a few minor shortcomings: for example, a literature reference cited in the text (“Beck et al.”, p 142) is missing in the bibliography; “Kronecker” is mistyped with o ̈; and the author completely forgot to reference Leach’s text book when referring to other computational chemistry introductions. However, the author has established a specific errata web page (http://pollux.chem.umn.edu/ ∼cramer/Errors.html) with all known errors. These will be corrected in the next printing or next revised edition, respectively. With its emphasis, on one hand, on the basic concepts and applications rather than pure theory and mathematics, and on the other hand, coverage of quantum mechanical and classical mechanical models including examples from inorganic, organic, and biological chemistry, “Essentials” is a useful tool not only for teaching and learning but also as a quick reference, and thus will most probably become one of the standard text books for computational chemistry.

Essentials Of Computational Chemistry Theories And Models

Additions to Metal-Activated Organonitriles†

Reactions of transition metal dihydrogen complexes

Biological nitrogen fixation by the nitrogenase enzymes has long been a touchstone for dinitrogen chemists.1,2 Both the enzymatic reduction and protonation of N2 mediated by these metalloenzymes (eq 1)3,4 and the industrial hydrogenation of N2 exemplified by the Haber-Bosch process (eq 2)5-7 employ transition metal-based catalysts to accelerate the thermodynamically feasible production of ammonia.

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Dinitrogen Coordination Chemistry: On the Biomimetic Borderlands

Hydride complexes IrHCl(2)(PiPr(3))P(2) (1) and IrHCl(2)P(3) (2) [P = P(OEt)(3) and PPh(OEt)(2)] were prepared by allowing IrHCl(2)(PiPr(3))(2) to react with phosphite in refluxing benzene or toluene. Treatment of IrHCl(2)P(3), first with HBF(4).Et(2)O and then with an excess of ArCH(2)N(3), afforded benzyl azide complexes [IrCl(2)(eta(1)-N(3)CH(2)Ar)P(3)]BPh(4) (3, 4) [Ar = C(6)H(5), 4-CH(3)C(6)H(4); P = P(OEt)(3), PPh(OEt)(2)]. Azide complexes reacted in CH(2)Cl(2) solution, leading to the imine derivative [IrCl(2){eta(1)-NH=C(H)C(6)H(5)}P(3)]BPh(4) (5). The complexes were characterized by spectroscopy and X-ray crystal structure determination of [IrCl(2)(eta(1)-N(3)CH(2)C(6)H(5)){P(OEt)(3)}(3)]BPh(4) (3a) and [IrCl(2){eta(1)-NH=C(H)C(6)H(5)}{P(OEt)(3)}(3)]BPh(4) (5a). Both solid-state structure and (15)N NMR data indicate that the azide is coordinated through the substituted Ngamma [Ir]-Ngamma(CH(2)Ar)NNalpha nitrogen atom.

Preparation of benzyl azide complexes of iridium(III).

Reaction of OsH2P4 [P = P(OEt)3, PPh(OEt)2, PPh2OEt] with methyl triflate followed by the treatment with hydrazines gave the [OsH(RNHNH2)P4]BPh4 (1−3) (R = H, CH3, C6H5, 4-NO2C6H4) derivatives. Instead, the reaction of OsH2P4 first with methyl triflate, then with triflic acid, and finally with an excess of the appropriate hydrazine afforded the bis(hydrazine) [Os(RNHNH2)2P4](BPh4)2 (4, 5) (R = H, CH3, C6H5) complexes. Also the [Os(NH2NH2){P(OEt)3}5](BPh4)2 (7) derivative was prepared. All the hydrazine complexes were fully characterized by IR and 1H and 31P NMR spectra, and a single-crystal X-ray structure determination of the complex [Os(NH2NH2)2{P(OEt)3}4](BPh4)2·C2H5OH (4a) is reported. The compound crystallizes in the space group P21/c with a = 20.550(4) A, b = 19.663(4) A, c = 20.843(4) A, β = 99.84(9)°, and Z = 4. The coordination around the osmium atom is octahedral and the orientation of the ligands in the [Os(NH2NH2)2{P(OEt)3}4]2+ cation is determined by several strong hydrogen bonds involving hy...

Mono- and Bis(hydrazine) Complexes of Osmium(II): Synthesis, Reactions, and X-ray Crystal Structure of the [Os(NH2NH2)2{P(OEt)3}4](BPh4)2 Derivative

Triazenide [M(η2-1,3-ArNNNAr)P4]BPh4 [M = Ru, Os; Ar = Ph, p-tolyl; P = P(OMe)3, P(OEt)3, PPh(OEt)2] complexes were prepared by allowing triflate [M(κ2-OTf)P4]OTf species to react first with 1,3-Ar...

Synthesis and characterization of triazenide and triazene complexes of ruthenium and osmium.

Molecular hydrogen complexes [MH(η 2 -H 2 )P 4 ]BF 4 [M=Ru, Os; P=PhP(OEt) 2 , P(OEt) 3 , P(OMe) 3 ] were prepared by allowing the MH 2 P 4 hydrides to reaction with HBF 4 •Et 2 O in ethanol or diethyl ether. Their characterization by variable-temperature 1 H and 31 P NMR data. The influence of the phosphite ligand and the central metal (Fe, Ru, Os) on the properties of the complexes is also discussed. Monohydrido complexes of the type [MHLP 4 ]BPh 4 [L=CO, 4-CH 3 C 6 H 4 NC, 4-CH 3 C 6 H 4 CN; P=PhP(OEt) 2 , P(OEt) 3 ] were obtained by substitution of dihydrogen with the appropriate ligand

Molecular Hydrogen Complexes. Preparation and Reactivity of New Ruthenium(II) and Osmium (II) Derivatives and a Comparison along the Iron Triad

Reactions of molecular hydrogen complexes [RuH(η2-H2)P4]BF4 with alkynes : preparation and crystal structure of the [Ru{η3-(p-tolyl)C3CH(p-tolyl)}{PhP(OEt)2}4]BPh4 derivative

Stefano Antoniutti

Papers

Preparation of benzyl azide complexes of iridium(III).

Mono- and Bis(hydrazine) Complexes of Osmium(II): Synthesis, Reactions, and X-ray Crystal Structure of the [Os(NH2NH2)2{P(OEt)3}4](BPh4)2 Derivative

Synthesis and characterization of triazenide and triazene complexes of ruthenium and osmium.

Molecular Hydrogen Complexes. Preparation and Reactivity of New Ruthenium(II) and Osmium (II) Derivatives and a Comparison along the Iron Triad

Reactions of molecular hydrogen complexes [RuH(η2-H2)P4]BF4 with alkynes : preparation and crystal structure of the [Ru{η3-(p-tolyl)C3CH(p-tolyl)}{PhP(OEt)2}4]BPh4 derivative