scispace - formally typeset
Search or ask a question

Showing papers in "Advances in Inorganic Chemistry and Radiochemistry in 1972"


Book ChapterDOI
TL;DR: In this article, a qualitative explanation of the secondary bond behavior is given, and it is argued that the secondary bonds are the result of directed forces rather than electrostatic or non-nondirectional van der Waals forces.
Abstract: Publisher Summary A number of recent crystal structure determinations on compounds of the nonmetals have discovered intramolecular distances that are much longer than normal bonds, and intermolecular distances that are much shorter than van der Waals distances. In this chapter, these interactions are examined and a qualitative explanation is attempted. It will become clear that in most of them an approximately linear arrangement is found, Y-A—X where Y-A is a normal bond and A—X is a short intermolecular distance. It is with these approximately linear interactions that we are particularly concerned, and it will be our contention that they are the result of directed forces and that their behavior is sufficiently regular and understandable for the name secondary bond to be appropriate. The only conclusive method of establishing the presence of secondary interactions is by crystal structure determinations. An intermolecular interaction can be recognized as being significant by being shorter than the expected intermolecular (van der Waals) distance, but if it is the result of directed forces— that is, bonds rather than electrostatic or nondirectional van der Waals forces.

494 citations


Book ChapterDOI
TL;DR: In this article, the authors compare the performance of Mossbauer spectroscopy and ultraviolet spectroscopic methods, and show that the differences in spectra can be attributed to the hyperfine interactions; the interactions between the nuclear charge distribution, and the extranuclear electric and magnetic fields.
Abstract: Publisher Summary Mossbauer spectroscopy can be likened to ultraviolet spectroscopy. Both techniques employ a source of radiation, an absorber and a detector. In Mossbauer spectroscopy, we consider transitions between nuclear energy levels with the emission and absorption of y rays; whereas, in ultraviolet spectroscopy, we consider the transitions between electronic energy levels with the emission and absorption of ultraviolet radiation. To observe resonance, a range of source photon energies is scanned: in ultraviolet by the use of a prism or grating, and in Mossbauer by employing the Doppler effect. The energy of the y ray (E,) is varied by the well-known Doppler formula d E = (V/C)E, where AE = change in energy of y photon, 11 = velocity of source relative to the absorber, and c = velocity of light. As in ultraviolet, absorption is plotted versus the energy of source photon (usually in velocity units for Mossbauer). Different compounds of one isotope give different spectra— that is, the nuclear energy levels are sensitive to the extranuclear environment. These differences in spectra can be attributed to the hyperfine interactions; the interactions between the nuclear charge distribution, and the extranuclear electric and magnetic fields. These hyperfine interactions give rise to the isomer shift (IS.) , the quadrupole splitting (Q.S.), and the magnetic Zeeman splitting.

208 citations


Book ChapterDOI
P.L. Timms1
TL;DR: In this article, it was shown that carbon vapor, formed from a carbon arc under vacuum, reacted with organic compounds at -196° to give new compounds incorporating the carbon vapor species.
Abstract: Publisher Summary The idea of studying gaseous radicals and high temperature species by condensing them on very cold surfaces has been employed for many years. The work of Rice and Freamo on the thermal decomposition of hydrazoic acid was a spectacular example. The imine radical produced condensed to a bright blue solid at -196°, which on warming to room temperature formed white ammonium azide. Various methods of trapping unstable species were reviewed in 1960, in a book by Bass and Broida . An important development occurred in 1963, when Skell and Westcott reported that carbon vapor, formed from a carbon arc under vacuum, reacted with organic compounds at -196° to give new compounds incorporating the carbon vapor species. The objectives of these experiments and the reaction conditions used are fundamental to the work discussed in this chapter. The carbon was vaporized under high vacuum such that the vapour species could move away from the arc without intermolecular collisions, which would have caused aggregation. The walls of the surrounding vacuum chamber were cooled with liquid nitrogen.

108 citations


Book ChapterDOI
TL;DR: The metal dialkylamides M(NR) as mentioned in this paper are of special interest, in that they contain covalent metal-nitrogen bonds, and occupy a position between the metal alkoxides and the metal alkyls.
Abstract: Publisher Summary Since the metal alkoxidesM(OR), were first comprehensively reviewed in 1960 , considerable progress has been maintained and the next major review in 1967 quoted over three hundred references. The most significant advances have involved the chemistry of the transition metal alkoxides with the emphasis on the ligand field aspects of the alkoxo group (e.g., electronic spectra, magnetism, etc.) and on X-ray crystallographic and NMR structural determinations. Industrial applications have been concerned with metal alkoxides as components of soluble Ziegler-Natta catalysts for olefin polymerization and also as sources for the production of pure metal oxides. The metal dialkylamides M(NR,) are of special interest, in that they contain covalent metal-nitrogen bonds, and occupy a position between the metal alkoxides and the metal alkyls. The field has not been fully reviewed, hitherto. However, excellent reviews have recently appeared on titanium dialkylamides and the reactivity of metal-dialkylamido bonds.

94 citations


Book ChapterDOI
TL;DR: In this paper, several transition metal complexes containing bidentate phosphine ligands are described, and a major complication in diphosphine complexes is the relative complexity of the ligands.
Abstract: Publisher Summary This chapter describes several transition metal complexes containing bidentate phosphine ligands. The bonding in metal–phosphine ligands due to the formation of π-type bonds between the metal and phosphorus atoms. Several techniques are used to study metal–phosphine complexes. These techniques include mass spectroscopy infrared spectroscopy, nuclear magnetic resonance, electronic spectroscopy, electron spin resonance, and Mossbauer spectroscopy. A major complication in diphosphine complexes is the relative complexity of the ligands. When a diphosphine complexes with a metal ion, the electron density on the phosphorus atom changes, and the ligand is restricted in the conformation it can assume. Thus the vibrational spectra of the free and coordinated ligands differ.

55 citations


Book ChapterDOI
TL;DR: The chemistry of these compounds has been the subject of several reviews, and has also been covered more or less fully in reviews on sulphurfluorine and sulphur-nitrogen chemistry as mentioned in this paper.
Abstract: Publisher Summary Since the preparation of the first pure sulphur-nitrogen-fluorine compounds, NSF, NSF and S4N4F4, in 1955 this field has developed very rapidly. The chemistry of these compounds has been the subject of several reviews, and has also been covered more or less fully in reviews on sulphur-fluorine and sulphur-nitrogen chemistry . The spate of recent publications has, however, rendered these earlier summaries incomplete. The present article covers developments up to the middle of 1970, with main emphasis on the recent work. Compounds with other halogens are considered only insofar, as they are of interest in this context. The earlier division into acyclic and cyclic compounds has been retained, as has been the classification in terms of the various oxidation numbers of sulphur. An attempt has been made starting from NSF and NSF, to point out the general relationships in the chemistry of sulphur-nitrogen-fluorine compounds.

32 citations


Book ChapterDOI
TL;DR: In this paper, the structure of tetrasulfur tetranitride, S,N, was not known and could not even be reliably postulated until the middle of the twentieth century.
Abstract: Publisher Summary Although tetrasulfur tetranitride, S,N, was first prepared about 1835 , the chemistry of the sulfur nitrides progressed slowly until the middle of the twentieth century. In 1940, the structure of S,N, was not known and could not even be reliably postulated. Of the eight other sulfur nitrides described as individual chemical species in the present review, only two were known, and these had not been fully characterized. Since then, there have been great advances and the whole subject has been put on a systematic footing. Some key contributions have come from the schools of Donohue, who correctly determined the structure of S4N, Becke-Goehring and Meuwsen, whose wide-ranging and meticulous experimental work, and original thinking have extended our knowledge in many directions, and Weiss, whose introduction of chromatography to this area of chemistry has proved to be one of the most significant of the many advances made by him. At present, several research groups in Europe, North America, and Asia are working on sulphur nitrides, and the subject is still in a lively state, though the effort is on a much smaller scale than in more fashionable fields of inorganic chemistry.

26 citations


Book ChapterDOI
TL;DR: A review of the halide and pseudohalide chemistry of beryllium can be found in this article, where the literature has been covered up to the middle of 1970.
Abstract: Publisher Summary The recent interest in the chemistry of beryllium and its compounds perhaps stems from its wide applications currently being developed, having moved from the nuclear power orientation, prevalent in 1961, to one which now explores aerospace and instrument applications. Berylium possesses a generous supply of unique chemical and physical properties. It and the beryllides have great scientific and practical interest owing to the low neutron capture cross section of beryllium, their high melting points, relatively low specific gravities, hardness, high strengths at high temperature (ten times that of ceramics) and resistance to corrosion, these properties making them useful in aviation, rocket, and nuclear technology his present review deals with all the major aspects of the halide and pseudohalide chemistry of beryllium; the literature has been covered up to the middle of 1970. Beryllium fluorides and chlorides are important industrially, as intermediates in the preparations of metallic beryllium. Beryllium chloride has also been used in diagnosing tuberculosis ; sodium beryllium fluoride has been used in the manufacture of glass having high ultraviolet permeability, as a flux in certain porcelain enamels, and in coating special welding rods.

19 citations


Book ChapterDOI
TL;DR: In this paper, the preparation and properties of alicyclic fluorocarbon (fluoroalicy clic) derivatives of metals and metalloids are discussed, and the discussion is restricted to compounds containing the fluorocric ring sigma-bonded to elements other than carbon, nitrogen, oxygen and the halogens.
Abstract: Publisher Summary This article will be concerned with the preparation and properties of alicyclic fluorocarbon (fluoroalicy clic) derivatives of metals and metalloids The discussion will be restricted to compounds containing the fluoroalicyclic ring sigma-bonded to elements other than carbon, nitrogen, oxygen, and the halogens, although inevitably, the chemistry of some compounds from this latter group will need to be described Complexes, in which the metal or metalloid is a part of a ring, such as are excluded as are n complexes of fluoroalicyclic olcfins that some authors regard as metallocyclopropanes The general class of sigma-bonded fluorocarbon derivatives of metals and metalloids has been known for some time Most of the early work was concerned with the chemistry of trifluoroiodomethane and the preparation of trifluoromethyl derivatives, such as (CF), Hg Since then fluoroaliphatic derivatives of many transition metals have been prepared, and some interest has been shown in studying vinylic and acetylenic derivatives

16 citations