Homoleptic complexes copper

A very interesting amido functionahsed carbene was prepared by Legault et al. [116] from A-mesitylimidazole and 0-(2,4-dinitrophenyl)hydroxylamine, an electrophilic ami-nation reagent [117]. The exo-amino group is subsequently acylated to afford a zwitterionic amido functionalised carbene (see Figure 4.38). Reaction with silver(l) acetate and sodium carbonate [a rare variant of the silver(I) oxide method] yields the silver(l) carbene complex as a dimer with a Ag-Ag bond. The silver(l) carbene complex can be used as a carbene transfer reagent to synthesise the homoleptic monomeric copper(Il) carbene complex. 

Complex 154 is an anionic homoleptic complex in which the five square-plane-coordinated copper(II) atoms are exclusively bound to the deprotonated /3-D-mannopyranose in Ci conformation. The increased redox stability therefore is not a consequence of the spatial separation of the oxidizing Cu(II) atoms and the half-acetal function of the monosaccharide. However, it is a consequence of the involvement of the O atoms, at the anomer C atoms, in the coordination of copper, as it is for the homoeptic lyxose complexes. 

Examples of silver(l) alkyl and alkenyl (including aryl) complexes have been known from as early as 1941 6-9 however, the number of examples is fairly limited with respect to that of the heavier congeners, copper(l) and gold(l). Such a phenomenon can readily be attributed to the relatively low stability of this class of complexes, both photochemically and thermally. Simple homoleptic alkyl and alkenyl complexes of silver(i) are known to be very unstable under ambient temperature and light, and successful isolation of this class is fairly limited and mainly confined to those involving perfluoroorganics.10 The structures and the metal-carbon bond-dissociation energies for... 

Such J-mctals as Cu(I) [but not Cu(II)], form a variety of compounds with ethenes, for example [Cu(C2H4)(H20)2]C104 (from Cu, Cu2+, and C2H4) or Cu(C2H4)(bipy)+. It is necessary to mention that, of all the metals involved in biological systems, only copper reacts with ethylene [74b]. Such homoleptic alkene complexes can be useful intermediates for the synthesis of other complexes. The olefin complexes of the metals in high formal oxidation states are electron deficient and therefore inert toward electrophilic reagents. By contrast, the olefin complexes of the metals in low formal oxidation states are attacked by electrophiles such as protons at the electron-rich metal-carbon a-bonds [74c]. 

Dinuclear complexes were obtained by reacting some binary copper(I) and silver(I) homoleptic pyrazolate complexes with neutral ligands. The trimeric [Cu(dmpz)]3 (23) readily reacted with phen or RNC (R = cyclohexyl) to give the doubly bridged species [(phen)Cu(/i-dmpz)2Cu(phen)], 32, (49) or [(RNC)Cu(/t-dmpz)2Cu(RNC)], 33 (50). The dimeric nature of 32 was argued from its spectroscopic and chemical properties, while 33 was characterized by an X-ray crystal structure analysis (50). 

Recently, it has been found that the copper(I) homoleptic pyrazolate complexes [Cu(dmpz)], 6, and [Cu(dppz)]4, 8, are catalytically active in the oxidative coupling of primary aromatic amines to give the corresponding azobenzenes in the presence of 02 at atmospheric pressure (17, 137). 

The synthesis of Bpph,4CN has been reported by Eichhorn and coworkers.174 The monomeric homoleptic square-planar copper complex [Cu(BpPh,4GN)2] has been prepared by the reaction of... 

A series of homoleptic copper(i), silver(i), and gold(i) complexes of two bisphosphine ligands l,2-bis(diphenylphosphino)benzene, dppb bis[2-(diphenylphosphino)phenyl]ether, POP has been studied to demonstrate that these species are very low emissive in solution but highly luminescent in the solid state. In particular, the silver and copper complexes afford quite broad electroluminescence spectra with white light emission when used in the fabrication of light-emitting devices. ... 

Another source of interest came from biochemistry. Research on the blue copper proteins revealed unusual electronic properties (redox potential and kinetics, EPR and optical behavior) that were suspected of arising from interaction of the copper ion with a thioether group from methionine [7]. While crystallographic studies established a weak interaction (Cu -- - S 2.9 A) [8,9,10], its influence on the electronic properties of the Cu site is now considered questionable. Nevertheless, the controversy regarding the blue eopper proteins, like the analogy to phosphines, served to focus attention on the broad issue of how thioether coordination affects the electronic structure of transition metal ions. Homoleptic thioether complexes provide the best way of assessing these consequences, since no other groups obscure the effect of thioether coordination. 

ABSTRACT. Lithiumthiazoles react by substitution or addition with gold and copper chlorides and subsequent protonation or alkylation affords stable mono- or bis(carbene) complexes. Complications which occur during these syntheses include homoleptic rearrangement, dissociative polymerization and carbon-carbon ligand coupling. 

More systematic insight into the coordinatirMi of diphenylplatinum complexes to d metals was obtained using the simple a-diimine ligand 2,3-bis(2,6-dichlorophe-nylimino)butane (NISI). The complex [(NN)PtPh2] reacts with half an equivalent of MOTf (M = Cu, Ag) to form homoleptic 2 1 cationic complexes in which the coinage metal is bound to the diphenylplatinum unit in a type III fashion (Scheme 15, top). The X-ray crystal structure of the copper cation is presented in Figure 1. 

The trinuclear [ClCu Zr2(OPr )9 ] has the [CuZr(jU3-OPr )2(jU,-OPr )3] core similar to the analogous titanium complex. The homoleptic Cu(i)Zr(iv) complex has a different structure [Cu2Zr2(OPr )io] containing the confacial bi-octahedral Zr2(OPr )9 unit into which the Cu2(/u,-OPr ) group is inserted by the copper atoms bridging with terminal isopropoxo ligands on each Zr. The (/i-OPr ) Cu(/i-OPr ) system has a hnear O-Cu-0... 

A. J. Arduengo, H. V. R. Dias, J. C. Calabrese, F. Davidson, Organometallics 1993,12, 3405-3409. Homoleptic carbene-silver(I) and carbene-copper(I) complexes. 

In order to prepare a homoleptic solvento-complex by metal oxidation in a non-aqueous medium, the reduction products must not compete with the solvent molecules as ligands. Nitrosonium perchlorate, N(DC104, is a suitable oxidant. 4,15 Reactions have been performed in acetonitrile, nitromethane and ethylacetate. In acetonitrile this oxidant converts copper powder into the copper(I) and copper(II) homoleptic solvento-complexes, [Cu(MeCN)4][C104] and [Cu(MeCN)4][C104]2. On boiling an acetonitrile solution of these complexes with metallic copper, reduction of the copper(II)... 

More recently the oxidation of metals by nitrosonium salts in acetonitrile has been used to synthesize homoleptic solvento-complexes. Thus, the complexes, [Cu(MeCN)4]X (X = BF4, C104), l have been obtained by oxidation of metallic copper in acetonitrile with NOX the perchlorate, NOCIO4, in MeCN oxidizes metallic gold to form [Au(MeCN)4][C104], 3 Eq. 8.6 ... 

It has been shown 4 that Ph3CBp4 can function as a one-electron oxidant and is able to oxidize metallic copper with formation of the homoleptic solvento-complex, [Cu(MeCN)4][BF4]. Yamazaki S has reported that the phosphine and phosphite complexes of palladium(n), [Pd(PPh3)4]X2 (X = BF4, PF, and Pd P(OPh)3 4][PF6]2, have been synthesized in 60% and... 

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