Transition metal coordination compounds

MOMEC is a force field for describing transition metal coordination compounds. It was originally parameterized to use four valence terms, but not an electrostatic term. The metal-ligand interactions consist of a bond-stretch term only. The coordination sphere is maintained by nonbond interactions between ligands. MOMEC generally works reasonably well for octahedrally coordinated compounds. 

In addition to the processes mentioned above, there are also ongoing efforts to synthesize formamide direcdy from carbon dioxide [124-38-9J, hydrogen [1333-74-0] and ammonia [7664-41-7] (29—32). Catalysts that have been proposed are Group VIII transition-metal coordination compounds. Under moderate reaction conditions, ie, 100—180°C, 1—10 MPa (10—100 bar), turnovers of up to 1000 mole formamide per mole catalyst have been achieved. However, since expensive noble metal catalysts are needed, further work is required prior to the technical realization of an industrial process for formamide synthesis based on carbon dioxide. 

Photoluminescence of transition metal coordination compounds. P. D. Fleischauer and P. Flei-schauer, Chem. Rev., 1970, 70,199-230 (219). 

Photochemistry of transition metal coordination compounds. A. W. Adamson, W. L. Waltz,... 

The mutual influence of ligands in transition metal coordination compounds with multiple metal-ligand bonds. E. M. Shustorovich, M. A. Porai-Koshits and Y. A. Buslaev, Coord. Chem. Rev., 1975,17,1-98 (345). 

Transition metal coordination compounds in oscillating chemical reactions. K. B. Yatsimirskii and L. P. Tikhonova, Coord. Chem. Rev., 1985, 63,241 (90). 

Several different types of isomers arise in transition-metal coordination compounds, and these are described below. 

The photoaquation of a transition metal coordination compound (Reinecke s Salt) has recently been developed as an actinometer for the... 

In the last example, a serious handicap is the extreme sensitivity of the calculations to the parameterization of the metal atoms. In a paper concerning the spin states of metal dimer complexes (38) as studied by EHT, heavy manipulation of the original theory was needed. In the field of transition metal coordination compounds self-consistent charge (SCC) calculations (of the type already mentioned for electronegative atoms) are essential to obtain the diagonal elements Hu. 

An early example of a combinatorial approach to a reaction catalyzed by transition metal coordination compounds concerns phosphatase mimics, specifically in the hydrolysis of bis(/ -nitrophenyl)phosphate (1)—>(2) (Equation (l)) 29... 

Whereas 3c/4e hypervalent interactions (4.77) tend to be relatively uncommon and fragile in main-group compounds (often leading to transition states for nucleophilic displacement reactions, rather than stable equilibrium species), the corresponding interactions in transition-metal coordination compounds are ubiquitous and robust. The far higher prevalence of hypervalent co-bonding in transition-metal chemistry may be attributed to three major factors. 

Transition metal complexes, catalysts based on, 20 193 Transition-metal compounds cause of color, 7 326t, 328-331 Transition-metal coordination compounds, 7 582-584... 

Properties of hydrogen Properties of metals Band theory Properties of nonmetals Properties of transition metals Coordination compounds Crystal-held theory Complex ions... 

In simpler metal complexes the theoretical understanding of cis and tram effects has recently experienced a considerable advance this may be taken from various authoritative reviews on the mutual influence of ligands in transition metal coordination compounds (9) published by Hartley (10), Appleton, Clark, and Manzer (11), and by Shustorovich, Porai-Koshits, and Buslaev (9). Nevertheless, the interdependence of the various electronic effects is very difficult to appraise, and a theoretically rigorous description of the effects for metalloporphyrins seems premature at present. Therefore, we shall treat the matter in a rather intuitive manner. 

Early transition metals, coordination compounds of 2,2 6, 2"-terpyridine, 30 80-81... 

Table 5-10 Metal-Ligand Bond Distances in Transition-Metal Coordination Compounds... 

PM3 semi-empirical calculations furnish a solid account of the geometries of transition-metal coordination compounds. Most distances are within a few hundredths of an A of their experimental values, but large errors appear for a few compounds. PM3 can be recommended (with due caution) for preliminary structure determinations of transition-metal coordination compounds. 

See, R. F., Kruse, R. A., and Strub, W. M. (1998). Metal-ligand bond distances in first-row transition metal coordination compounds Coordination number oxidation state and specific ligand effects. Inorg. Chem. 37, 5369-75. 

The two main methods currently used in computational and combined computational/experimental studies in the general area of transition metal coordination compounds, and specifically also with macrocyclic ligands, are DFT and MM. While DFT yields structural data, energies and molecular vibrations, as well as electronic information (the ground state wave function, spin density, charge distribution etc ), the latter is missing in MM. 

Examinations of possible correlations between the volume of activation and the entropy of activation for series of similar reactions have been reported for reactions of transition metal coordination compounds, such as solvent exchange, ligand substitution, or isomerization.163 167 A limiting factor in a potential correlation may be the lack of precision that often attends experimental determination of the entropy of activation. Attention has been drawn specifically to the qualitative nature of the correlations between the two parameters for solvent exchange at some 3 + cations, and at square planar Pd2+ and Pt2+ ions.168... 

For transition metal coordination compounds AG° involves terms related to the ionization potential / of the free metal ion, the difference in complexation free energy A(AGc), involving the oxidized and the reduced free metal ion, and the difference in solvation free energy A(AGaq), involving the complexes in the two oxidation states ... 

Keywords. Electrospray ionization, Ion-molecule chemistry, Transition-metal coordination compounds, Organometallic catalysis... 

A large number of covalently linked systems are currently being synthesized and investigated, differing in the nature of A, B, and L, as well as in the number of functional units in the supramolecular system (nuclearity). It is common to call simple two-component donor-acceptor systems such as that of Eq. 2 dyads , and progressively more complex systems triads , tetrads , pentads , etc.. Systems where all the A and B units are organic molecules are dealt with in Chapter 1 of this section. The present chapter deals with systems where at least one of the A/B functional units is a transition metal coordination compound. From this definition, however, are excluded (a) systems where A and/or B are porphyrins or related species (dealt with in Chapter 2) and (b) systems of high nuclearity with dendritic structures (dealt with in Chapter 9). 

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