Cobalt compounds structures

Naturally occurring compounds with carbon-metal bonds are very rare The best example of such an organometallic compound is coenzyme Bi2 which has a carbon-cobalt ct bond (Figure 14 4) Pernicious anemia results from a coenzyme B12 deficiency and can be treated by adding sources of cobalt to the diet One source of cobalt IS vitamin B12 a compound structurally related to but not identical with coen zyme B12... 

About structures of lithium compounds LisMeFs we have but rare knowledge. Klemm, Brandt and Hoppe (193) report in accordance with Meyers and Cotton (225) that the x-ray-diagrams of the cobalt compound LisCoFe were of a poor quality. The polymorphism that Carton and Wanklyn (108) report of the aluminium compound LisAlFe points to a more complicated situation in this ternary fluoride. The sizes given of the unit cells do not show any simple relation to the cryolite cell. The same may be true of compounds LisMeFa of the transition metals. 

However the existence of the bromine co-product is speculative and has not been experimentally verified. The reaction may be regarded as a one electron oxidation by the S i. Me , )2 aminyl radical, and it is interesting to note that aminyl radical complexes of transition metals such as [Rh(Ntrop2)(bipy)][OTf]5 (trop = 5-H-dibenzo[a,d]cycloheptene) have been isolated. The manganese and cobalt compounds were the first examples of three-coordinate Mn(lll) and Co(lll) complexes to have been structurally characterized. 

Four of the eight triangular faces in octahedral Rh6(CO)16 (Rhftfri3-CO)4(CO),. J (Fig. 15.10) contain carbonyl groups bridging three metal atoms. The corresponding cobalt compound is thought to have a similar structure.17... 

The d-spacings of the 211 (d = 33.1 A) and 220 (d = 28.6 A) reflections of the pristine MCM-48 silica are observable in the host/guest compounds whereas the higher order reflections (20 4-6°) disappear. In addition, the 113/021 (d = 2.53 A 1=100%) and 208/220 (d = 1.48 A 1=36%) reflections of the inverse cobalt iron structure appear in sample A and B. In contrast to the bulk material of CoFe24 (figure 2) synthesized under exact the same conditions as the phases A and B, the reflections of the host/guest compounds are much broader and weaker in intensity, indicating the occurrence of very small particles. 

By polymerizing the trans isomer of 1,3-pentadiene two different types of crystalline cis-1,4 polymers have been obtained, one with an isotactic, the other with a syndiotactic structure. The isotactic polymer was obtained by homogeneous systems from an aluminum alkyl chloride and a cobalt compound, the syndiotactic one by homogeneous systems from an aluminum trialkyl and a titanium alkoxide. Some features of the polymerization by Ti and Co catalysts are examined. IR and x-ray spectra, and some physical properties of the crystalline cis-1,4 polymers are presented. The mode of coordination of the monomer to the catalyst, and possible mechanisms for the stereospecific polymerization of pentadiene to cis-1,4 stereoisomers are discussed. 

A remarkable difference between butadiene and isoprene is that with polymerization catalysts based on / -TiCl3, VC13, or cobalt compounds the structure of polybutadiene is mixed cis-1,4-+ trans 1,4, high trans-1,4, and high cis-1,4,... 

The Cambridge Structural Database contains X-ray crystallographic data for aU reported compounds and complexes of cobalt that contain carbon (see X-ray Crystallography). The November 2002 version of this database lists 10403 structures containing cobalt, with the earhest, the Co(n) complex of the phthalocyaninate dianion, dating back to 1936. The Inorganic Crystal Stmcture Database contains stmctural data for cobalt compounds... 

The sample studied was a cobalt bis(phosphonate) of composition C02(O3PC6H4OC6H4PO3)-2H2O. It is one of the series of first row transition element compounds with the same general formula, but different water contents. The Cu(ll) compound structure was solved from its powder pattern, unit cell dimensions a = 8 1012(5), b = 5.3109(3), c = 29.2595(5) A. It has a layered structure in which the layers are spaced at half the c-axis dimension. The reason for the doubling of the c-axis is that in one layer the rings are tilted around the ether oxygen to the left and in the next layer to the right. The Cu atoms are 5-coordinate with square pyramidal structure. 

Figure 7-64 shows the crystal structure of the copper homolog of the cobalt compound represented in Scheme 7-20 [119]. The copper(ii) center assumes a distorted tetrahedral coordination. The cyclopentadienyl rings of the two ferrocenyl fragments are eclipsed.

Type AIII. The two structures in this class, both of hexahydrates of 3d metal halides, form a striking contrast to two structures of All. Both contain octahedral coordination groups M(H20)4Cl2 with the trans configuration. (NiCl2. 6 H2O is similar to the cobalt compound.)... 

In 1893, at the age of 26, Alfred Werner stepped outside the box and proposed his coordination theory that revolutionized the held of inorganic chemistry. Werner s work, in part, made use of colorful cobalt compounds prepared by the reaction of ammonia with cobalt salts. Fortunately, these cobalt salts are quite stable ( robust ) in aqueous solution. This stability, along with the rapid development of qualitative and quantitative analytical techniques, enabled Werner to carry out the rigorous and in-depth analyses that led to the determination of molecular formulas and prediction of structures and geometries. His work opened the door to understanding bonding and stability (Chapter 3) and reactivity (Chapters 4 and 5) in metal coordination complex systems. 

Another supporting evidence for complex formation as a prerequisite to synergism was obtained from the study of the catalysis of phenyl isocyanate-butanol reaction by soluble organic cobalt compounds in presence and absence of DABCO catalyst. The results obtained are presented in Figures 4 and 5. It is evident that the combination of DABCO catalyst with divalent cobalt compounds shows synergistic effects while the trivalent cobalt acetylacetonate shows relatively low activity. The explanation of these observations is the structure of these compounds. 

---