Copper complexes planar

Chiral ferrocenes have received niucli attenlion as ligands in metal-calalyzed reactions [39], bul tiieir use in copper cliemislry has been very limited [40, 41]. Hie ferrocene moiety offers die possibility of utilizing botli central and planar cliirality in die ligand. By analogy witli tlie copper arenetiiiolales described above, ferrocenyl copper complex 33 iSclieme 8.20) is extremely inleresling. 

These authors further described the synthesis and resolution (by chiral HPLC) of a new C2-symmetric planar-chiral bipyridine ligand [43] (see structure 35 in Scheme 18). They obtained an X-ray crystal structure of the corresponding copper complex proving a bidentate complexation. This system led to high diastereo- (up to 94%) and enantioselectivity (up to 94%) in the... 

In their pursuit of determining solution structures of dinuclear copper complexes as carried out for complex (29) (Section 6.6.3.1.1). Comba reported complex (431) (r = 0.02 Cu-Cu 6.9 A, comparable with the values of 7.2 A predicted by molecular mechanics calculations and 6.7 A obtained from the simulated EPR spectrum).54 They reported369 complexes (432) (square planar) and (433) (Cu-Cu 3.35 A) as well. As part of studying magnetic properties of mono-, di-, and... 

X-ray crystallographic data has become available on the commercially important 1 1 copper complex azo dyes. The symmetrical dihydroxyazo ligand (16) forms the 1 1 square planar complex (17).13 A pyridine molecule occupies the fourth coordination site since this complex facilitated the formation of crystals suitable for X-ray diffraction. The complex (17) actually exists as an unusual trimer which is held together by long bridging interactions between the copper atom in one molecule and one of the hydroxy oxygen atoms from the adjacent molecules. 

Evans suggests that the catalyst resting state in this reaction is a 55c Cu alkene complex 58, Scheme 4 (35). Variable temperature NMR studies indicate that the catalyst complexes one equivalent of styrene which, in the presence of excess alkene, undergoes ready alkene exchange at ambient temperature but forms only a mono alkene-copper complex at -53°C. Addition of diazoester fails to provide an observable complex. These workers invoke the metallacyclobutane intermediate 60 via a formal [2 + 2] cycloaddition from copper carbenoid alkene complex 59. Formation of 60 is the stereochemistry-determining event in this reaction. The square-planar S Cu(III) intermediate 60 then undergoes a reductive elimination forming the cyclopropane product and Complex 55c-Cu, which binds another alkene molecule. 

In an approach to planar chiral ferrocenes, Siegel and Schmalz (85) report that bis(oxazoline)-copper complexes induce efficient aromatic C-H insertion from a... 

The required long planar shape is more readily supplied by simple disazo structures such as Cl Direct Blue 1 (4.60). Copper complexes of such disazo compounds are important and are dealt with elsewhere (section 5.5.3). A widely used method of producing A—A type disazo dyes relies on treating J acid with phosgene (COCl2) to give the bis-coupling component carbonyl J acid (4.61). 

The anisotropy of the g and the hfs tensor of the central ion are of the same order of magnitude, but the principal axes of each tensor with the largest anisotropy coincide. Examples are planar cobalt and copper complexes. 

An EPR and ENDOR investigation of the planar copper complex 63Cu(sal)2 (Fig. 30) substituted into a single crystal of Ni(sal)2 has been reported by Schweiger et al.62,65). The aim of this work was to determine the structure of the internal H-bond occuring in Cu(sal)2, and to draw a detailed picture of the unpaired electron distribution on the... 

Nitrogen ENDOR. The nitrogen hfs tensor is nearly axially symmetric with the largest principal axis oriented approximately along the Cu-N bond direction (<(Cu-N, A ) = 7°). A very similar result has been reported by Moores and Belford168 for the planar copper complex Cu(msal)2. 

The blue copper protein stellacyanin, with a molecular weight of about 20,000, is obtained from the Japanese lacquer tree Rhus vemicifera. The EPR spectrum is described by roughly axial g and ACu hfs tensors and an unusually small a j value. As shown in Fig. 39 a, only the largest copper hf value A u can be directly determined from the EPR spectrum202. This coupling does not lie along the largest g-principal axis, in contrast to the usual behaviour of square planar copper complexes. 

Besides, comparisons with other non-macromolecular gelling systems are in progress. Specially, we can co.mpare with a square planar copper complex, which aggregates in linear chains to gelify the cyclohexane (l ). It is immediatly noticed that characteristic times of the aggregation kinetics are correlated to the complexity of the molecular aggregation mechanism involved. 

In the solid state, the metal atoms in bis(salicylaIdoximato)copper(II) show two additional contacts with the oxime oxygens of adjacent molecules, resulting in a distorted octahedral structure. However, the axial Cu—O distance (2.66 A) is much longer than the metal—ligand distances in the square-planar array (Cu—O, 1.92 A and Cu—N, 1.94 A).154 Studies by ESR of copper(II) extracts of the commercial reagent SME 529 (14 R = Me, R = C9H)9) have shown that the copper complex exists as a square-planar species in hydrocarbon solutions, but that five-coordinate adducts are formed in the presence of ammonia or pyridine.155... 

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