Counting procedures

Perhaps the most notable difference between S-N and N-O compounds is the existence of a wide range of cyclic compounds for the former. As indicated by the examples illustrated below, these range from four- to ten-membered ring systems and include cations and anions as well as neutral systems (1.14-1.18) (Sections 5.2-5.4). Interestingly, the most stable systems conform to the well known Htickel (4n -1- 2) r-electron rule. By using a simple electron-counting procedure (each S atom contributes two electrons and each N atom provides one electron to the r-system in these planar rings) it can be seen that stable entities include species with n = 1, 2 and 3. 

Hence, the problem of counting how many experimental conditions are required to fix the matrix P satisfying Equation (6) is equivalent to that for the case satisfying Equation (7). We treat here the problem of imposing Equations (7), because, as we shall see, we can display a clear counting procedure for them. This approach represents a generalization of that used by Fano and Roman for the specific case N = 1. 

Having derived if by a method independent of those used in [1-3], we now compare our result to those obtained in these previous papers. From the perspective of our present counting procedure, we hope to shed light on the previous derivations. We shall take them up in the order in which they appeared in the literature. 

The mean radon concentrations determined by the passive detectors are based on calibrations using NBS standard radium-226 solutions and also from participation in the OECD (Nuclear Energy Agency)/CEC radon dosimeter intercomparisons (Commission of the European Communities, 1986) held at the U.K. National Radiological Protection Board (NRPB). Recent calibrations of the new LR-115 based detectors, in terms of response to radon concentrations and F factors have been carried out at the NRPB, which assistance is greatly appreciated. For the etching and track counting procedures used the inner LR-115 piece in the detectors has a mean sensitivity of approximately 1.6 tracks cm 2 kBq l m hr l. 

The counting procedure represented by Eqn. IV.9 is termed the neutral-bonded formalism, and may (like Eqn. IV.7) be regarded as a set of equations supplementary to those presented in Eqn. IV.3 for the generalized (8-N) rule formalism. 

Wade s electron-counting procedures (22) start from a closed polyhedron and require that neither removing a vertex from this polyhedron nor capping a face will alter the number of skeletal bonding orbitals. This capping principle has been demonstrated to be general (31). For... 

The anion [Osg(CO)18p has an octahedral arrangement of metal atoms of approximately Oh symmetry, and is crystallographically very similar to the [HRus(CO)w]- ion. This collection of structural data on electron-equivalent systems emphasizes some of the dangers in trying to predict the structure of complexes solely on the basis of electron counting procedures (220). 

It should also be noted that a six-electron rule affords conformity with the electron counting procedures of Rudolph (13)... 

The foregoing examples show the relevance to metal-carbonyl cluster chemistry of the borane-oarborane structural and bonding pattern. Its relevance to other areas of chemistry may be explored readily using a systematic skeletal electron-counting procedure (161, 201). 

For mixed main group-transition element clusters containing but one transition element, modifying the above electron-counting procedure to include the 6 nonbonding electron pairs on the transition metal has been advocated (128) as a way of bringing the electron count into line... 

For a description of the electron-counting procedure as applied to metal clusters, see Ref 37.) The paramagnetism of the nickel cluster, in principle, could be detected directly by neutron diffraction with a polarized beam and an external magnetic field. However, such measurements were not undertaken, and the effects of paramagnetism on the observed diffraction intensities, that are small in the present experiment, were ignored. 

Finally, in applying any electron-counting procedure to orgnnometallic complexes, we must remember that it is merely a formalism—albeit a very useful one We - ... 

Some of the beautiful relationships that exist between r/iuo. nitlti., ind unit lino osmium complexes tire shown in Fig. 16.56.m For Lick of space wc have not touched on many subtleties associated with geometry/bontling/electron counting procedures and the reader is encouraged to consult more advanced sources.144... 

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