Ferrocenyl copper

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. 

Chiral ferrocenes have received much attention as ligands in metal-catalyzed reactions [39 but their use in copper chemistry has been very limited [40 41]. The ferrocene moiety offers the possibility of utilizing both central and planar chirality in the ligand By analogy with the copper arenethiolates described above ferrocenyl copper complex 33 (3cheme 8.20) is e ctremdy interesting. 

These complexes can be isolated in some cases in others they are generated in situ from appropriate precursors, of which diazo compounds are among the most important. These compounds, including CH2N2 and other diazoalkanes, react with metals or metal salts (copper, palladium, and rhodium are most commonly used) to give the carbene complexes that add CRR to double bonds. Ethyl a-diazoacetate reacts with styrene in the presence of bis(ferrocenyl) bis(imine), for example, to give ethyl 2-phenylcyclopropane-l-carboxylate. Optically active complexes have... 

The mechanism of the enantioselective 1,4-addition of Grignard reagents to a,j3-unsaturated carbonyl compounds promoted by copper complexes of chiral ferrocenyl diphosphines has been explored through kinetic, spectroscopic, and electrochemical analysis.86 On the basis of these studies, a structure of the active catalyst is proposed. The roles of the solvent, copper halide, and the Grignard reagent have been examined. 

The copper-catalysed enantioselective 1,4-conjugate addition of Et2Zn to chalcones was investigated in the presence of a catalytic amount of Af,P-ferrocenyl ligand (179) with central and planar chirality under mild conditions (0 °C to room temper- ature). Chalcones with ortho-substituents (from ortho-substituted benzaldehydes and acetophenones) exhibited a dramatic improvement in the enantioselectivities (<92% ee).229... 

A number of ferrocenyl chelates containing oxygen and copper,48,55,57,147 as well as other metals,B7,147,1478 have been reported. 

A similar bidentate ligand containing a ferrocenyl bridge between two BINOL moieties was described by Reetz and co-workers. Copper-catalyzed 1,4-addition reactions of diethylzinc to cyclohex-2-enone and cyclohept-2-enone in... 

For the replacement of boron by an amino groiqi in aryl-, styryl- and ferrocenyl-dihydroxyboranes, the reaction of copper(II) phthalimide followed by hydrazinolysis or hydrolysis, has been used (equation 64). - ... 

Solid state electrochemistiy stndies on Cu(hfacac)2L2 (L = 126, 126 ) show that the ferrocenyl subunits are easier to oxidize by abont 30 mV than in the free hgand. A copper(ll)-centred reduction is present at about -1-0.07 V, vs. SCE. ... 

Copper-catalyzed 1,3-dipolar cycloaddition of azomethine imine 264 with ethyl propiolate 265 with a chiral ferrocenyl bidentate ligand efficiently generated dihydropyrazol[l,2- 7]pyrazolones 266 in very good yields and ee... 

The monosulfide, Fc-S-Fc, was first prepared in 1961 by Rausch [48] by reaction of the thiolate Fc-SNa with iodoferrocene, Fc-I, in the presence of copper bronze at 150 °C. The disulfide, Fc-SS-Fc, had been obtained independently by Knox and Pauson [81] and by Nesmeyanov et al. [82] at an even earlier date (1958) by aerial oxidation of mercaptoferrocene, Fc-SH hydrolytic cleavage of ferrocenyl thiocya-... 

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.

Figure 7-67 shows the crystal structure of (C5H5)Fe[C5H4-CH2-NH-(CH2)2-NH-CH2-C5H4]Fe(C5H5) 2Cu(N03)2 [188]. Because of the axial coordination of the two nitrate anions, the central copper (n) ion assumes octahedral coordination. Both the ferrocenyl fragments are in a nearly eclipsed conformation. 

It has been reported that this dicopper complex undergoes an irreversible copper-centered reduction at — l.OV in DMSO and two oxidation steps at p = -t-0.20 V and E° = -t-0.62 V, respectively. The less anodic process, which is not fully reversible and possesses a return peak at p = -0.1 V, is difficult to assign, whereas the more anodic process, which is chemically reversible, has been assigned to electron removal processes from the ferrocenyl fragments [191]. Unfortunately, controlled potential coulometric tests have not been performed to determine the number of electrons involved in each electron-transfer step. We should like to think... 

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