Metal coordination compound

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. 

The triply connected phosphoms compounds have a lone electron pair that dominates much of the chemistry for these compounds. Triply connected compounds typically exhibit pyramidal symmetry arising fromp hybridization. A considerable amount of sp character may be present as well. Bond angles range near 100° vs 90° theoretical. Tricoordinate compounds typically act as electron donors, forming metal coordination compounds and addition compounds such as H P BF [41593-56-0]. 

Metal coordination compounds may also provide alternatives to the heterogeneous catalysts used for the water gas shift reaction. In fact, Ru, Rh, Ir, and Pt coordination compounds have all shown some promise (27). 

The most numerous cases of homogeneous catalysis are by certain ions or metal coordination compounds in aqueous solution and in biochemistry, where enzymes function catalyticaUy. Many ionic effects are known. The hydronium ion and the hydroxyl ion OH" cat-... 

VI. Stabilization of Unusual Tautomeric Forms of Azoles and Their Derivatives in Metal Coordination Compounds... 

Due to the relatively high acidities of their hydroxy groups, hydroxyazoles readily exchange their protons with metal ions, which leads to stabilization of metal derivatives of the hydroxy tautomeric forms in metal coordination compounds of 2(5)-oxoazoles [97UK434 98AHC(72)1]. A typical example is the mercury complex 361 [93JCS(D)1003]. 

The complex 23 is the first X-ray structurally characterized metal coordination compound with a benzochalcogenazole ligand in which chalcogen behaves as the ligating atom. 

Compared with other metal coordination compounds, relatively little is known about chelate photochemistry. 

Unsubstituted phthalocyanines are accessible by the reaction of phthalonitrile with metals, alloys, metal salts or metal coordination compounds. Often a mixture of these compounds and phthalonitrile are heated without solvent beyond the melting point of phthalonitrile. 

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... 

A recoil-implanted metal atom (radioactive M) undergoes the following chemical reaction with a metal coordination compound in a film of catcher material ... 

Similar methods of encapsulation are also observed in pillared clays, which were also introduced as catalysts as long ago as the early 1980s. The field has been thoroughly reviewed up to 2000 [65], Layered double hydroxide structures have also been used for the entrapment of metal coordination compounds [66],... 

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... 

To date, most small molecule-based OLEDs are prepared by vapor deposition of the metal-organic light-emitting molecules. Such molecules must, therefore, be thermally stable, highly fluorescent (in the solid state), form thin films on vacuum deposition, and be capable of transporting electrons. These properties limit the number of metal coordination compounds that can be used in OLED fabrication. 

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. 

Rare-earth ion exchange, 11 680 Rare earth metal coordination compounds, 7 584... 

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... 

Platinum and Other Metal Coordination Compounds in Cancer Chemotherapy 2, Pineto, H. M. and Schornagel, J. H., Eds. Plenum New York, 1996. 

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. 

Oudeman law physchem The law that the molecular rotations of the various salts of an acid or base tend toward an identical limiting value as the concentration of the solution is reduced to zero. od-a-man, I6 ) outer orbital complex phys chem A metal coordination compound in which the d orbital used in forming the coordinate bond is at the same energy level as the s and p orbitals. aud-or 6rb-od-3l kam.pleks) overall stability constant analychem Reaction equilibrium constant for the reaction... 

Metallocene, An organo-metallic coordination compound, or more specifically a cyclopentadienyl derivative of a transition metal or metal halide. Metallocenes are best known as catalysts for polymerizing ethylene and propylene. 

---