Schiffs Base Complexes

FIGURE 25 Overview of N-alkyl salicylaldimine Schiff s base ligands. 

TABLE 2 Thermal Behavior of Lanthanide Compounds With Two-Ring Schiff s Base Ligands L1H  

crystalline phase SmA, smectic A phase 1, isotropic liquid dec., decomposition.  

TABLE 3 Thermal Behavior of the Lanthanide Complexes of the /V-alkyl-4-(3,4-dialkoxylbenzoyloxy)salicylaldimine Schiff s Base Ligands L2H  

crystalline phase Colh, hexagonal columnar phase 1, isotropic liquid.  

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Rhodium complexes with oxygen ligands, not nearly as numerous as those with amine and phosphine complexes, do, however, exist. A variety of compounds are known, iucluding [Rh(ox)3] [18307-26-1], [Rh(acac)3] [14284-92-5], the hexaaqua ion [Rh(OH2)3] [16920-31 -3], and Schiff base complexes. Soluble rhodium sulfate, Rh2(804 )3-a H2 0, exists iu a yellow form [15274-75-6], which probably coutaius [Rh(H20)3], and a red form [15274-78-9], which contains coordinated sulfate (125). The stmcture of the soluble nitrate [Rh(N03)3 2H20 [10139-58-9] is also complex (126). Another... 

In another type of mixed ligand oxo-vanadium Schiff base complexes chloro-oxo-bis[N(4-bromophe-nyl) salicylideneiminato] vanadium (V) chelate, VOL2CI, and methoxo-oxobis[N(4-bromophenyl)sali-cylideneimine vanadium (V) chelate, VOL2OCH3 Aiiwi and Salih [43] show that these complexes are active pho-... 

The conformation of Schiff-base complexes of copper(IT) a stereo-electronic view. H. S. Maslen and T. N. Waters, Coord. Chem. Rev., 1975,17,137-176 (127). 

Further results on organotin(IV)-amino acid or 2-amino-2-methyl-l-propanol Schiff base complexes were reported in Refs. (264-271). 

Gonzalez-Arellano, C., Corma, A., Iglesias, M. and Sanchez, F. (2005) Homogeneous and heterogenized Au(III) Schiff base-complexes as selective and general catalysts for self-coupling of aryl boronic acids. Chemical Communications, (15), 1990. 

Much work has been devoted to the study of Schiff base complexes, in particular M(salen), where M = metal, has been the subject of extensive work 114). The early work by Calvin et al. (section 111(A)) suggested that the 2 1 (M O2) dioxygen adduct, type I, formed by Co(salen) in the solid state, contains a peroxo linkage. An X-ray analysis 115, 116) of the complex (Co Salen)202(DMF)2 supports this hypothesis see Fig. 5 for the pertinent results of this study. 

An X-ray photoelectron spectroscopic study (132) of some cobalt(II) Schiff base complexes and their dioxygen adducts finds that the cobalt core electron binding energies in... 

An EPR study of the monomeric 02 adducts of the Schiff base complexes of Co(bzacen)(py) (71a) and the thiobenzoyl analog Co(Sbzacen)(py) (71b) characterized the five-coordinate mono (pyridine) precursors and the six-coordinate 02 adducts.327 Increased covalency in the Co—S bonds was seen in the EPR parameters, indicative of 7r-backbonding. Substituent effects on the aromatic rings had no effect on the EPR spectra, but these were reflected in the observed redox potentials. Furthermore, the S-donors stabilize the Co ion in lower oxidation states, which was consistent with destabilization of the 02 adducts. 

The P-N chelate (91) (dapdmp) exhibits a variety of coordination geometries in complexes with divalent Co. Pseudotetrahedral Co(dapdmp)X2 (X = C1, Br, I, NCS), low-spin five-coordinate [Co(dapdmp)2X]+ (X = C1, Br, I), planar [Co(dapdmp)2]2+ and pseudo-octahedral Co(dapdmp) (N03)2 were all identified.390 The tetradentate P2N2 Schiff base complex (92) is formed by reacting the free ligand with CoI2. The iodo complex is low spin and square pyramidal.391... 

There are many biomimetic model Co complexes of the cobalamins.1149 The primary criterion for an effective B12 model has been that the complex may be reduced to the monovalent state and undergo facile oxidative addition to generate a stable alkylcobalt(III) complex. The two main classes of B12 model complexes that have been investigated are Co oximes and Schiff base complexes. The former class shares the planar CoN4 array of their biological analogs whereas the majority of effective Schiff base Bi2 model complexes comprise equatorial czj-N202 donor sets. 

Ni111 Schiff base complexes have been produced by electrochemical oxidation of Ni11 complexes derived from naphthaldehyde, and identified by EPR spectroscopy.88... 

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... 

The physicochemical properties of Schiff-base complexes encapsulated in zeolite70 and the surface chemistry of zeolite-encapsulated CoSalen and [Fe(bpy)3]2+ catalysts were studied and published.71... 

Domination of the S-diastereomers for the dioxovanadium(V) Schiff base complexes being derivatives of aromatic orf/zo-hydroxyaldehydes or ketones and (S)-(+)-2-(aminomethyl)-pyrrolidine [35] was shown and the molar ratio of the diastereomers was determined by means of integration of the H signals.85... 

NMR spectra of (p-cymene)ruthenium (II) Schiff base complex, derivative of (S)-(a-methylbenzyl) and 3,5-di-ferf-butylsalicylaldimine, at room temperature in CDCI3 solution evidenced the presence of diastereomers at the ratio of 88 12.93 On the basis of a detailed analysis of 2D NMR spectra (ROESY) measured at 293 and 233 K, the (RRu,Sc) configuration of the major diastereomer in solution was suggested. 

Analysis of the 27A1 NMR spectra has confirmed the structure of the aluminium di-Schiff bases complexes being derivatives of trans-1,2-dia-minocyclohexane. The A1 chemical shift values of 6.57 and 39.48 ppm indicated the presence of dynamic equilibrium between five- and six-coordinated states in CDC13 solution. 

Interesting results have been presented by Baleizao et al. for chiral vanadyl Schiff base complex [50].120 The 29Si MAS NMR spectra have confirmed covalent grafting of the vanadyl complex into the silicate skeleton. 

Penicillamine reacts with pyridoxal-5-phosphate to form a thiazolidine derivative, and is able to displace many amino acids from their Schiff base complexes, forming stable compounds of this type. The reactivity of the thiol group of penicillamine is less than that of cysteine, probably because of steric hindrance by the adjacent methyl groups of penicillamine, which in consequence is less rapidly oxidized in vivo [7]. 

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