Coordination compounds paramagnetism

Bonding Energetics of Organometallic Compounds Electron Transfer in Coordination Compounds Paramagnetic Organometallic Complexes Structure Property Maps for Inorganic Solids. 

In a large number of coordination compounds, paramagnetic resonance results are used to investigate the bonding between the central metal and the ligands. This analysis is usually based on the molecular orbital theory for the system under consideration. As an example, we present here the relevant relations for a copper(II) complex with symmetry [30],... 

The properties of copper(Il) are quite different. Ligands that form strong coordinate bonds bind copper(Il) readily to form complexes in which the copper has coordination numbers of 4 or 6, such as tetraammine copper(Tl) [16828-95-8] [Cu(NH3)4], and hexaaquacopper(Il) [14946-74-8] [Cu(H,0),p+ ( see Coordination compounds). Formation of copper(Il) complexes in aqueous solution depends on the abiUty of the ligands to compete with water for coordination sites. Most copper(Il) complexes are colored and paramagnetic as a result of the unpaired electron in the 2d orbital (see Copper... 

The striking feature of many coordination compounds is that they are colored or paramagnetic or both. How do these properties arise To find out, we need to understand the electronic structures of complexes, the details of the bonding, and the distribution of their electrons. 

There are few reported coordination compounds of Ir°. Monomeric Ir° species are paramagnetic (id9 electronic configuration), and binuclear compounds are diamagnetic with a metal-metal bond. 

All the monomeric molybdenum(III) complexes are paramagnetic, and in Table l5 the magnetic moments of some typical examples are given. For six-coordinate compounds the values lie between 3.53 and 3.86 BM, with most in the region 3.7 to 3.8 BM as predicted for octahedral d3 complexes.37 The value of 1.73 BM in ELt[Mo(CN)7] 2H20 is consistent with a spin-doublet ground state d3 system.3S... 

Molecular mechanics has been used in combination with NMR spectroscopy to solve structural problems. MM-NMR techniques have been extensively used to solve protein structures125,1221. The main NMR information used in the modeling process is based on Karplus relations and NOE effects. Recent applications also involved the simulation of paramagnetic shifts in proteins with metal centers such as co-balt(II)11231. In such systems, the fact that protons close to the metal centers have short relaxation times (T and T2) can be used to establish connectivity patterns1124-1261. Applications in the area of simple coordination compounds are quite raretl27-130] although these are of importance, especially in respect of the determination of solution structures of metalloproteins, where the modeling of the metal center can be one of the more serious problems (see also Chapter 12). 

Klaus H. Theopold was born in Berlin, studied at the Universitat Hamburg for his Vordiplom in 1977, and at UC Berkeley, where he obtained his PhD in 1982 under the direction of Professor R. G. Bergman. After spending a year as postdoctoral fellow in the laboratory of Professor R. R. Schrock at MIT, he began his independent career in 1983 as an Assistant Professor at Cornell University. In 1990 he moved to the University of Delaware, where he is currently Professor of Chemistry. His scientific interests encompass synthetic and mechanistic studies of transition metal compounds, in particular paramagnetic organometal-lics, polymerization catalysis, and coordination compounds relevant to the activation of O2. 

This volume of the Handbook illustrates the rich variety of topics covered by rare earth science. Three chapters are devoted to the description of solid state compounds skutteru-dites (Chapter 211), rare earth-antimony systems (Chapter 212), and rare earth-manganese perovskites (Chapter 214). Two other reviews deal with solid state properties one contribution includes information on existing thermodynamic data of lanthanide trihalides (Chapter 213) while the other one describes optical properties of rare earth compounds under pressure (Chapter 217). Finally, two chapters focus on solution chemistry. The state of the art in unraveling solution structure of lanthanide-containing coordination compounds by paramagnetic nuclear magnetic resonance is outlined in Chapter 215. The potential of time-resolved, laser-induced emission spectroscopy for the analysis of lanthanide and actinide solutions is presented and critically discussed in Chapter 216. 

Radical anion — is a molecule (mostly organic or coordination compound) after a one-electron reduction, having a charge of -1, and bearing an unpaired electron, i.e., being paramagnetic. 

C. Piguet and C.F.G.C. Geraldes, HRE, 2003, 33, 353 (solution structure of lanthanide-containing coordination compounds by paramagnetic nnclear magnetic resonance). 

Paramagnetic coordination compounds where the spin resides predominantly on one or more of the organic (or inorganic) ligands are quite common, especially complexes of radical anions [17] such as o-semiquinones 1 or other negatively charged chelates such as tetrapyrrole macrocycles 2 [18],... 

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