Clusters nomenclature

Wade electron counting rules borane-like cluster nomenclature. On initially studying compounds such as boranes (boron hydrides) and carboranes (or carbaboranes boron—carbon hydrides), Wade (1976) proposed a number of rules which have then been extended to several compounds and which relate the number of skeletal electrons with the structure of deltahedral clusters. A polyhedron which has only A-shaped, that is triangular, faces is also called a deltahedron. 

Isopropyl group (Section 2 13) The group (CH3)2CH— Isotactic polymer (Section 7 15) A stereoregular polymer in which the substituent at each successive chirality center is on the same side of the zigzag carbon chain Isotopic cluster (Section 13 22) In mass spectrometry a group of peaks that differ in m/z because they incorporate differ ent isotopes of their component elements lUPAC nomenclature (Section 2 11) The most widely used method of naming organic compounds It uses a set of rules proposed and periodically revised by the International Union of Pure and Applied Chemistry... 

Elemental composition, ionic charge, and oxidation state are the dominant considerations in inorganic nomenclature. Coimectivity, ie, which atoms are linked by bonds to which other atoms, has not generally been considered to be important, and indeed, in some types of compounds, such as cluster compounds, it caimot be appHed unambiguously. However, when it is necessary to indicate coimectivity, itaUcized symbols for the connected atoms are used, as in trioxodinitrate(A/,A/), O2N—NO . The nomenclature that has been presented appHes to isolated molecules (or ions). Eor substances in the soHd state, which may have more than one crystal stmcture, with individual connectivities, two devices are used. The name of a mineral that exemplifies a particular crystal stmcture, eg, mtile or perovskite, may be appended. Alternatively, the crystal stmcture symmetry, eg, rhombic or triclinic, may be cited, or the stmcture may be stated in a phrase, eg, face-centered cubic. 

The nomenclature of boron hydride derivatives has been somewhat confusing and many inconsistencies exist in the Hterature. The stmctures of some reported boron hydride clusters are so compHcated that only a stmctural drawing or graph, often accompanied by explanatory text, is used to describe them. Traditional nomenclature systems often can be used to describe compounds unambiguously, but the resulting descriptions may be so long and unwieldy that they are of Htde use. The lUPAC (7) and the Chemical Abstract Service (8) have made recommendations, and nomenclature methods have now been developed that can adequately handle nearly all clusters compounds however, these methods have yet to be widely adopted. Eor the most part, nomenclature used in the original Hterature is retained herein. 

J. B. Casey, W. J. Evans, W. H. PoweU, and T. E. Sloan, "A Stmctural Definitive Descriptor and Numbering System for Cluster Compound Nomenclature," Chemical Abstract Service, presented at the 198th National Meeting of the American Chemical Society, Miami Beach, FI., Sept. 1989. 

Development of Coordination Chemistry Since 1930 Coordination Numbers and Geometries Nomenclature of Coordination Compounds Cages and Clusters Isomerism in Coordination Chemistry Ligand Field Theory Reaction Mechanisms... 

Based on recently obtained crystallographic data, cluster I and II were renamed cluster 2 and 1, respectively. In the following discussion the new nomenclature will be used. 

CBP Cromolyn-binding protein CCK Cholecystokinin CCR Creatinine clearance rate CD Cluster of differentiation (a system of nomenclature for sur ce molecules on cells of the immune system) cluster determinant CDl Cluster of differentiation 1 also known as MHC class I-like surfitce glycoprotein... 

Figure 1 Binuclear iron core inserted over a) Z" and b) Z"0h clusters used to represent the 5MR portion of the ZSM-5 zeolite framework. T site numbers follow the ZSM-5 nomenclature. Pink balls are Al, grey balls are Si, blue balls are Fe, red balls are O and white balls are H.

The sections are divided by the coordination number of the reacting ion defined as the number of donor atoms that interact with the metal. The nomenclature used for the ligands is L for neutral molecules that act as ligands and X for anions that act as ligands. Most of the examples in this section will involve cations [ML ]+ or [MX ]+, but there will be a short section on bare metal anions, M . The anions of more complexity than M will be discussed in Section IV on clusters. Many reactions produce an initial product that continues to react resulting in further coordi-native changes and possibly redox changes. Tables I and II will indicate the initial reaction product and other major reaction products. 

FIGURE 5.1 Cluster model of amylopectin. A and B denote nomenclature of branch chains, 0=reducing end, c.l. = chain length in degree of polymerization. Reprinted from Carbohydrate Research, Vol. 147, Hizukuri (1986), Polymodal distribution of the chain lengths of amylopectin, and its significance, Pages 342-347, with permission from Elsevier. 

The names helper cells, cytotoxic cells and natural killer cells indicate the function of the cells and are, therefore, useful. The more formal , nomenclature is the CD classification (e.g. CD4-tve cells and CD8-tve cells). CD stands for the cluster of differentiation, which is a technique for distinguishing between different protein molecules attached to different cells its value is that it can identify very precisely the type of immune cell (Appendix 17.3). Thus the helper cells express CD4 molecules on their surface, whereas cytotoxic cells express CDS molecules on their surface. 

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