Michael A. McGinn

Bio: Michael A. McGinn is an academic researcher from University College Dublin. The author has contributed to research in topics: Ab initio & Molecular orbital. The author has an hindex of 9, co-authored 14 publications receiving 252 citations.

Structure and properties of phosphaketene (H―P=C=O): phosphorus versus oxygen protonation?

Abstract: Phosphaketenes carrying bulky substituents to limit dimerization have recently been reported and for comparison the simple model phosphaketene (1) was investigated using ab initio methods. It has an E-bent structure with a CP bond length of 1.728A; and a CPH bond angle of 90.6°(using the 4-31 G basis set). This is rationalized in terms of stabilizing interactions between the PH and CO fragments so that the C–P bond is essentially a dative single bond enforced by π-back-donation. Both P and O centres carry an overall negative charge; of five possible structures of protonated HPCO considered, phosphorus protonation is unambiguously preferred and the perpendicular structure (11) calculated to be the most stable. Inclusion of polarization functions and correlation energies favours phosphorus protonation further. Also reported are the vibrational frequencies, dissociation energies of the protonated and neutral phosphaketene, and the predicted reactivity in both cycloadditions and additions of HX; comparison is made with reported experimental data where available.

A theoretical characterization of some diatomic copper species

Abstract: As test cases for an economic ab initio treatment of copper complexes with the aid of the GAUSSIAN 82 package, results on three diatomic copper species CuX (X = H, F and Cl) and their cations are reported. At the SCF and MP4SDQ levels of accuracy along with the MIDI-4 basis set, calculated spectroscopic parameters can be compared with available experimental data. Reasonable confidence in the computed results combined with the efficient performance of the program makes it a good tool for the study of chemical reactivity of copper compounds, and thus more attractive to chemists.

All-Metal Aromaticity and Antiaromaticity

Abstract: Metals and organic molecules are at the opposite sides in chemistry. Thus one may think that chemical bonding models, such as aromaticity, developed in organic chemistry will not be applicable in systems involving metallic elements. Yet in recent years there have been significant advances in extending the aromaticity and antiaromaticity concepts into the realm of metal clusters and alloys. These new developments have shown that aromaticity and antiaromaticity in metal systems have frequently multiple nature, being o-aromatic/antiaromatic and n-aromatic/antiaromatic, which is not found in organic aromatic/antiaromatic molecules.

Stable Noncyclic Singlet Carbenes

Abstract: 2.2.1. Diaminoand Aminohydrazinocarbenes 3338 2.2.2. Aminothioand Aminooxycarbenes 3340 2.3. Phosphinoaryland Phosphinoalkylcarbenes 3341 2.4. Aminoaryland Aminoalkylcarbenes 3344 2.5. Aminophosphonio and Aminosilylcarbenes 3346 2.6. Aminophosphinocarbenes 3347 3. Reactivity 3348 3.1. Typical Carbene Behavior 3348 3.1.1. Coupling Reactions 3348 3.1.2. Cycloaddition Reactions 3352 3.1.3. Insertion Reactions 3355 3.1.4. Migration Reactions 3358 3.2. Basic/Nucleophilic Behavior 3359 3.2.1. Protonation of Carbenes 3359 3.2.2. Reactions with Group 14 Electrophiles 3360 3.2.3. Reactions with Group 13 Lewis Acids 3360 3.2.4. Reactions with Group 15 Electrophiles 3361 3.3. Electrophilic Behavior 3362 3.3.1. Reaction with 1,5-Diazabicyclo[4.3.0]non-5-ene (DBN) 3362

Electronic structure of diatomic molecules composed of a first-row transition metal and main-group element (h-f).

Abstract: Understanding the nature of the transition-metal (TM)-main-group-element bond is important in many areas of science, such as organometallic chemistry,1,2 surface science,3 catalysis,4 high-temperature chemistry,5,6 and astrophysics.7,8 For example, the oxides are of interest to astrophysics as the constituents of cool stars and to surface science as zero-order models for the oxidation of a transition-metal surface.9 These systems are electronically complex and very difficult to treat theoretically. Indeed, while the use of quantum chemistry to obtain useful and reliable information about small organic molecules is now routine,11 a very different situation arises in the theoretical description of molecules containing a transition element. This is due to several factors, but the most important is that the extent of electron correlation required for even qualitatively correct results is significantly raised relative to molecules containing only main-group elements. The correlation between the electronic states of a molecule and the states of its constituent atoms has been an important concept in chemistry and physics for many years. For example, we know that if a molecule is composed of atoms that have large energy differences between their various electronic states, the molecule will be characterized by electronic states that are widely spaced, or granular. In the context of the preeminent orbital theory, the Hartree-Fock (HF) theory, this means that the molecular orbitals of molecules formed from these atoms will be widely spaced in energy, and the HF configuration will dominate the wave function around equilibrium. This is, of course, the reason the HF theory has achieved its unique role as both an interpretive and predictive tool in the chemistry of the firstand second-row, main-group elements. While the situation becomes somewhat flawed as one moves away from equilibrium structures, the conceptual simplicity and interpretability of the orbital picture can be preserved by constructing self-consistent wave functions in which the HF configuration is augmented by one or more configurations. This multiconfiguration, self-consistent field (MCSCF) approach is capable, in principle, of providing a uniform description of the evolution 679 Chem. Rev. 2000, 100, 679−716

13C NMR Spectroscopy of “Arduengo-type” Carbenes and Their Derivatives

Abstract: Since the isolation and crystallographic characterization of the first stable N-heterocyclic carbene in early 1991,1 nucleophilic diaminocarbenes (also known as “Arduengotype” carbenes) and their analogues have emerged as a powerful class of carbon-based ligands with broad applications in metal-based catalytic reactions.2-12 The main reason for their success in catalysis is their superior properties as ligands in comparison with their phosphine counterparts.11,13-18 In addition, carbene organocatalysis has emerged as an extremely fruitful area of research in synthetic organic chemistry. The benzoin condensation, the Stetter reaction, transformations involving homoenolates, 1,2-additions, transesterifications, and ring opening polymerizations are among the many reactions promoted by nucleophilic carbenes. Several excellent reviews, chapters, and books highlighting the recent progress of nucleophilic carbenes in metal-based catalysis and organocatalysis are available.7,9,11-16,19-24 Significant efforts have been made to better understand the unique properties associated with the free nucleophilic carbenes using a wide range of experimental techniques. X-ray diffraction,1,25 neutron diffraction,26,27 photoelectron spectroscopy,28 cyclic voltammetry,29-34 NMR spectroscopy, and IR spectroscopy10,35-40 are among the experimental techniques employed in these studies. The experimental methods have been complemented by theoretical investigations, which have become extremely important because they enable the study of a great number of related systems, a task that would be difficult or sometimes impossible to achieve experimentally. Density functional theory and molecular orbital theory have been employed for the study of these intriguing species.26-28,41-49