Chromium molecular structure

Fig. la. Structure of the complex bis( -butoxysilane-diyl)tetracarbonyliron(O) x HMPA 4. b. Molecular structure of the chromium complex bis( -butoxy-silanediyl)pentacarbonylchromium(O) x HMPA 9. c. Van der Waals surface of 9... 

In an attempt to change the electronics of the chromium atom, we are replacing the carbon based cyclopentadienyl ring with ligands containing harder donor atoms. For example, we have employed the tris(pyrazolyl)borate moiety, an isoclectronic replacement for Cp featuring tridentate N-coordination.[9] Figure 2 shows the molecular structure of Tp SU Cr-Ph, a representative Cr° alkyl. It will be noted, that this complex is mononuclear, due to the steric protection of the extremely bulky tris(pyrazolyl)borate. 

The molecular structure of the anchored Cr(VI) has been a strong point of discussion in the literature, and several molecular structures (monochromate, dichromate, polychromates) have been proposed (see Scheme 3). The nature of the silica support, the chromium loading, and the activation method can all influence the chemical state of the supported chromium. 

As a further confirmation of the extended redox aptitude of polypyridine ligands, Figure 15 shows the cyclic voltammetric behaviour of the heteroleptic chromium(III) complex with 2,2/-6/,2"-6//,2"/-quaterpyr-idine (qpy), together with its molecular structure.28... 

Mordant dyes have hydroxy groups in their molecular structure that are capable of forming complexes with melals. Although a variety of metals such as iron, copper, aluminum, and cohalt have been used, chromium is most preferable as a mordant. Alizarin or Cl Mordant Red 11 (Cl 38000). the principal component of the natural dye obtained from madder root, is the most typical mordant dye. Many murdant dyes have given way to the vat or the azoic dyes, which arc applied by much simpler dyeing procedures. 

Static SIMS would be particularly appropriate to study films formed by silane coupling agents by virtue of its high surface sensitivity, its capability to detect all elements and isotopes, and because it provides molecular structural information on organic materials [9-12], So far, SIMS has rarely been used to study silane films. It was used, however, to detect covalent bonds between iron or chromium and silane films deposited on stainless steel [13, 14], Such bonds were indeed reported this claim was based on the presence of ions in the spectrum which were assumed to be FeOSi+ and CrOSi. However, these SIMS analyses were not done under static conditions, which had not yet been established at the time of these studies. 

This section describes the structural chemistry of 14 molecular structures, 3 of chromium, 8 of molybdenum, and 3 of tungsten. The only binary xanthate structures are those of chromium, all other structures are at least ternary in nature. For the chromium and tungsten structures, conventional monodent-ate and bidentate coordination modes of the xanthate ligand are found. By contrast, a rich, diverse, and fascinating coordination range is observed for the... 

Fig. 2. Molecular structure of dicarbonyl- j4-( , )-2,4-hexadienebis(trimethylphosphine)-chromium(O) (24d) (25). Reprinted with permission from Z. Naturforsch. 39B, 1553 (1984). Copyright by Verlag der Zeitschrift fur Naturforschung.

The rearrangement could be corroborated via addition and cycloaddition reactions and also by the synthesis of the (OC)5 V=SnRR, complex97. The analogous chromium complex is formed via a reaction of chromium hexacarbonyl in THF (Scheme 16)98. The molecular structure is shown in Figure 42. The molybdenum complex is formed in the same way (Scheme 16, Figure 43)98. 

Finally, phosphole sulfides can behave as 77 4-electron or Tj -CjTj -Y-b-electron donors toward transition metals. For example, derivative 106 reacts with CpCo(CO)2 to afford the [7] -(phosphole sulphide)]cobalt(I) complex 107 (Scheme 31), which was characterized by X-ray diffraction <2006HAC344>. The chromium complex 109 was obtained in high yield from thioxophosphole 108 and its molecular structure determined crystallographically (Scheme 31). 

A very similar molecular structure has been observed (56) for the chromium complex of 1,3,5,7-tetramethylcyclooctatetraene (TMCOT), (TMCOT)Cr(CO)3 (30). The Cr(CO)3 group is linked to six of the ring... 

Figure 7-9 illustrates the molecular structure of (>j -C5H5)Fe[>7 -C5H4 = Cr(CO)4Br] [34], showing that the chromium atom possesses octahedral coordination the... 

The molecular structure of a chromium(II) complex [Cr(OC-f-Bu3)2 LiCl(thf)2] (281) is shown in Fig. 45. The structure is noteworthy in several respects, being a rare example of three-coordinate chromium(II) alkoxide. The geometry at chromium with a wide 0(1)—Cr—0(2) angle of 157.2(2)° may be considered as T-shaped. All five atoms forming the core 0(1), 0(2), Cr, Cl, and Li are coplanar. The geometry around the lithium atom is a severely... 

Introduction.—A report has been published listing heats of reaction and formation for chromium oxides and halides and for some chromates. Inorganic pyro compounds, M (X207)j, have been reviewed with consideration of species with X = Cr. A review of X-ray diffraction studies of the molecular structure of a number of Cr, Mo, and W complexes and organometallic compounds has appeared. ... 

Figure 2. The molecular structure of the chromium(lll) compound Cr3(//3-0)(02CNEt2)6Cl(NHEt2) (ethyl groups not shown),...

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