Octahedral amines

NMR, 5, 56 octahedral amines, 2, 28 electronic spectra, 5, 49 magnetic properties, 5, 60 oligonuclear... 

Snbstitution of various chelating hi- and polydentate amines, for example, en, 1,3-diaminopropane, dien, trien, and so on, in nonaqneons media yields an extensive series of octahedral amine complexes, which range in color from bine to pnrple. Their effective magnetic moments (4.7-4.9/xb) and electronic spectra are best explained assuming tetragonally distorted octahedral geometries. 

The majority of U(V1) coordination chemistry has been explored with the trans-ddo s.o uranyl cation, UO " 2- The simplest complexes are ammonia adducts, of importance because of the ease of their synthesis and their versatihty as starting materials for other complexes. In addition to ammonia, many of the ligand types mentioned ia the iatroduction have been complexed with U(V1) and usually have coordination numbers of either 6 or 8. As a result of these coordination environments a majority of the complexes have an octahedral or hexagonal bipyramidal coordination environment. Examples iuclude U02X2L (X = hahde, OR, NO3, RCO2, L = NH3, primary, secondary, and tertiary amines, py n = 2-4), U02(N03)2L (L = en, diamiaobenzene n = 1, 2). The use of thiocyanates has lead to the isolation of typically 6 or 8 coordinate neutral and anionic species, ie, [U02(NCS)J j)/H20 (x = 2-5). 

Compounds analogous to the cobaltammines may be similarly obtained using chelating amines such as ethythenediamine or bipyridyl, and these too have played an important role in stereochemical studies. Thus ct5-[Co(cn)2(NH3)Cl] was resolved into d(+) and /(—) optical i.so-mers by Werner in 1911 thereby demonstrating. to all but the most determined doubters, its octahedral stereochemistry. More recently, the absolute configuration of one of the optical isomers of [Co(en)3] was determined (.sec Panel on p, 1125),... 

Similarity with cobalt is also apparent in the affinity of Rh and iH for ammonia and amines. The kinetic inertness of the ammines of Rh has led to the use of several of them in studies of the trans effect (p. 1163) in octahedral complexes, while the ammines of Ir are so stable as to withstand boiling in aqueous alkali. Stable complexes such as [M(C204)3], [M(acac)3] and [M(CN)5] are formed by all three metals. Force constants obtained from the infrared spectra of the hexacyano complexes indicate that the M--C bond strength increases in the order Co < Rh < [r. Like cobalt, rhodium too forms bridged superoxides such as the blue, paramagnetic, fCl(py)4Rh-02-Rh(py)4Cll produced by aerial oxidation of aqueous ethanolic solutions of RhCL and pyridine.In fact it seems likely that many of the species produced by oxidation of aqueous solutions of Rh and presumed to contain the metal in higher oxidation states, are actually superoxides of Rh . ... 

Kinetics and mechanisms of substitution reactions of octahedral macrocyclic amine complexes. C. K. Poon, Coord. Chem. Rev., 1973,10,1-35 (130). 

Polyhedral oligomeric silsesquioxane (POSS) has been extensively studied as starting substrate to construct nanocomposites with precise control of nanoarchitecture and properties. Octahedral derivatives are the most representative ones of this family. It was reported that the HRP-catalyzed conjugation of catechin on amine-substituted octahedral silsesquioxane amplified the beneficial physiological property of flavonoids. The POSS-catechin conjugate exhibited great... 

NiS4 core is conserved giving trans octahedral complexes, while with bidentate amines cis octahedral complexes are obtained. Linear bidentate amines can result in a ID chain like in compound (341) where 4,4 -bipyridine molecules bridge the square planar units. 

Ni11 complexes of various amine/thiophenolate ligands have been investigated (for Ni complexes of ortho-aminothiophenol see Section 6.3.4.9.2(iv)). Thiophenolate is expected to exhibit decreased bridging tendency compared to aliphatic thiolates, but complexes (466) and (467) still consist of two pseudo-octahedral NiL fragments bridged via thiolate donors. In contrast to the parent complex (466), the thiolate and thioether donors in (467) coordinate cis to the Ni center... 

Complex [Ni(468)] is formed with Ni11 salts and the amine-thiolate ligand, or by reduction of the corresponding Schiff base complex with NaBH4-[Ni(468)] is easily deprotonated to form the dianionic complex, which is subsequently oxidized to the monoanion. On the other hand, the dianionic complex reacts with CH3I to form the fourfold methylated octahedral complex (469).1305 Since without preceding deprotonation only the S-donors are methylated, the complex with twofold amine methyla-tion must be synthesized via protection and subsequent deprotection of the S-donors.1306... 

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