Electron counting in clusters: A view of the concepts
About: This article is published in Polyhedron.The article was published on 1988-01-01. It has received 57 citations till now. The article focuses on the topics: Electron counting & Chemical bond.
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TL;DR: In this paper, the geometrical structure of small nickel clusters was probed via molecular adsorption of nitrogen on their surfaces, and the proposed structures can be rationalized with the predicted structures if it is assumed that N2 binds to every exposed nickel atom, that the binding energies decrease with increasing metal coordination, and that atoms that are four or less coordinate can bind two nitrogen molecules.
Abstract: The geometrical structure of small nickel clusters is probed via molecular adsorption of nitrogen on their surfaces. Nitrogen uptake patterns can be rationalized with the proposed structures if it is assumed that N2 binds to every exposed nickel atom, that the binding energies decrease with increasing metal—metal coordination, and that atoms that are four or less coordinate can bind two nitrogen molecules. In some cases nitrogen adsorption causes a change in cluster structure, usually to one that can accommodate more nitrogen molecules. Cluster structures are proposed for all clusters (bare and nitrogenated) in the 3–15‐atom size range except Ni4 and Ni11. The nitrogen uptake for Ni4 is consistent with virtually any structure, and the data for Ni11 could not be interpreted in terms of a specific structure. In general, nickel cluster structures are different from those found for rare gas clusters as well as those derived from bulk packing. A comparison of the experimental results with existing theoretical ...
198 citations
TL;DR: In this article, it was shown that the preferred closed-shell electron structures, such as those in typical high-symmetry 18-electron systems, are driven both by the bonding contributions to the centre and by the kinetic energy (nodal-structure) terms in the ligand subsystem, Ln.
153 citations
134 citations
TL;DR: In this article, the threshold collision-induced dissociation method is applied to study the fragmentation patterns and to measure the dissociation energies of small anionic copper clusters and their monocarbonyls.
Abstract: The threshold collision-induced dissociation method is applied to study the fragmentation patterns and to measure the dissociation energies of small anionic copper clusters (Cun−, n=2–8) and their monocarbonyls (CunCO−, n=3–7). For the bare clusters, the main reaction channels are loss of an atom and loss of a dimer. For the copper cluster monocarbonyls, the main channel is loss of CO. Dissociation energies for the loss of an atom from bare copper cluster anions, D0(Cun−1−–Cu), show even–odd alternation. The species with the highest dissociation energy, Cu7−, and the highest carbonyl desorption energy, Cu5CO−, have eight valence electrons, consistent with closed shells in the jellium model. Bond energies are compared with theoretical models.
110 citations
TL;DR: In this article, the issue of (phosphanido)platinum complexes, subdividing them into terminal and bridging species, has been discussed, and a rich chemistry has been developed on organometallic phosphanido Pt complexes bearing the pentafluorophenyl group.
Abstract: The PR2– group (the phosphanido group, according to the modern IUPAC rules) possesses a strong nucleophilicity, a high bridging tendency and a remarkable flexibility. This review addresses the issue of (phosphanido)platinum complexes, subdividing them into terminal and bridging species. Terminal (phosphanido)platinum complexes are usually prepared by deprotonation of a coordinated secondary (or primary) phosphane on a cationic PtII complex, by an appropriate base. The terminally bonded phosphanide group shows no tendency to form multiple bonds with platinum: in all crystallographically characterised Pt complexes, the terminal phosphanido P atom is pyramidal. Due to the high nucleophilicity granted by the presence of the active lone pair on P, terminal (phosphanido)platinum complexes react with molecules such as O2 and S8, and they can be used for the synthesis of dimetallic compounds upon reaction with suitable metal fragments. The known PtI phosphanido-bridged complexes are dinuclear, diamagnetic and endowed with a strong Pt–Pt bond. The μ-PPh2 bridge in PtI dimers arises often by (thermal) activation of the P–C bond in coordinated PPh3 or dppm. PtI phosphanido-bridged complexes are also prepared by reaction of (dichlorido)platinum complexes with reagents such as Na, NaOH, alcohols. For such complexes a multifaceted reactivity, including the substitution of a terminal ligand, the reaction with electrophiles such as H+ and its isolobal analogues, the insertion into the μ-P–Pt bond, has been reported. Hydridophosphanido complexes are formed by oxidative addition of a P–H bond onto zero-valent Pt complexes, by protonation of PtI dimers or by action of BH4– on halido species. Dehydrochlorination of secondary (and primary) phosphane complexes gives chlorido complexes which are mostly prepared in the anti-[(PRR′2)(Cl)Pt(μ-PR″2)]2 geometry. Chiral complexes are obtained when asymmetric phosphanido P atoms are present in the molecule. A rich coordination chemistry has been developed on organometallic phosphanido Pt complexes bearing the pentafluorophenyl group. In this framework, a great number of Pt complexes of various nuclearity have been crystallographically characterised and their reactivity towards oxidants studied. The class of polynuclear phosphanido Pt complexes is represented by triangulo species, in which the bridging phosphanide group is typically μ-PPh2 or μ-PtBu2, by linear complexes of various nuclearity and by bent species stemming from the presence of a triply bridging diphenylphosphanido ligand in the molecule. Applications of phosphanido Pt complexes in catalysis and materials chemistry are also discussed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
65 citations
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TL;DR: In this paper, the borane-carborane structural pattern has been studied in a wide range of other compounds, including metal clusters, metal-hydrocarbon 7∼ complexes, and various neutral or charged hydrocarbons.
Abstract: Publisher Summary This is one of two articles in this volume that is concerned with the borane-carborane structural pattern. In the other, Williams has shown how the pattern reflects the coordination number preferences of the various atoms involved. The purpose of the present article is to note some bonding implications of the pattern, and to show its relevance to a wide range of other compounds, including metal clusters, metal-hydrocarbon 7∼ complexes, and various neutral or charged hydrocarbons. Boranes and carboranes may be regarded as cluster compounds in the sense defined by Cotton; they contain a finite group or skeleton of atoms held together entirely, mainly, or at least to a significant extent by bonding directly between those atoms, even though some other atoms may be associated intimately with the cluster. Examples of their structural pattern, however, can be found far beyond the confines of what is normally regarded as cluster chemistry, so this survey includes many systems not commonly referred to as clusters.
1,235 citations
TL;DR: In this article, a technique for image reconstruction by a maximum entropy method is presented, which is sufficiently fast to be useful for large and complicated images and is applicable in spectroscopy, electron microscopy, X-ray crystallography, geophysics and virtually any type of optical image processing.
Abstract: Results are presented of a powerful technique for image reconstruction by a maximum entropy method, which is sufficiently fast to be useful for large and complicated images. Although our examples are taken from the fields of radio and X-ray astronomy, the technique is immediately applicable in spectroscopy, electron microscopy, X-ray crystallography, geophysics and virtually any type of optical image processing. Applied to radioastronomical data, the algorithm reveals details not seen by conventional analysis, but which are known to exist.
969 citations
773 citations
TL;DR: In this paper, simple rules for rationalizing and predicting the geometries of complex polynuclear aggregates of atoms and molecular fragments are presented, and simple rules are presented for rationalization and prediction of the geometry of these aggregates.
Abstract: Simple rules are presented for rationalizing and predicting the geometries of complex polynuclear aggregates of atoms and molecular fragments
497 citations
331 citations