Carbamato

Organic carbamates (RNHCOO-) commonly display monodentate coordination, as exemplified in the structurally characterized tetrahedral Co(bmc)2Cl2,438 (bmc = lV-(benzimidazoyl-2-yl)-O-methylcarbamate). An unusual route to a carbamato complex involves the reaction of Co2(CO)8 in the presence of a fourfold excess of the stable radical species tmpo, which yields the blue Co40(OOCNC9H18)6 cluster, presumably via a Co(CO)2(tmpo) intermediate, with the nitroxyl radical serving as oxidant.439... 

Zinc dithiocarbamates have been used for many years as antioxidants/antiabrasives in motor oils and as vulcanization accelerators in rubber. The crystal structure of bis[A, A-di- -propyldithio-carbamato]zinc shows identical coordination of the two zinc atoms by five sulfur donors in a trigonal-bipyramidal environment with a zinc-zinc distance of 3.786 A.5 5 The electrochemistry of a range of dialkylthiocarbamate zinc complexes was studied at platinum and mercury electrodes. An exchange reaction was observed with mercury of the electrode.556 Different structural types have been identified by variation of the nitrogen donor in the pyridine and N,N,N, N -tetra-methylenediamine adducts of bis[7V,7V-di- .vo-propyldithiocarbamato]zinc. The pyridine shows a 1 1 complex and the TMEDA gives an unusual bridging coordination mode.557 The anionic complexes of zinc tris( V, V-dialkyldithiocarbamates) can be synthesized and have been spectroscopically characterized.558... 

The preparation of ZnSe materials is an area of interest and study. The coordinating ability of the solvent used in the solvothermal synthesis of zinc selenide was demonstrated to play an important role in the nucleation and growth of nanocrystalline ZnSe.604 Thermolysis of bis [methyl( -hexyl)di-seleno]carbamato]zinc gave highly monodispersed particles characterized by electronic spectroscopy, photoluminescence, X-ray diffraction, and electron microscopy.605... 

Tris(N,N-Disubstituted-XY-Carbamato)lron(lll) Compounds (XY=SO, SSe, SeSe)... 

Tris-carbamato-iron(III) complexes [Fe(02CNR2)3] have been prepared for R = ethyl, isopropyl, cyclohexyl (cx), and benzyl, and binuclear //-oxo derivatives (for R = Et, cx) and various /U3-OXO, //4-0X0, and /i-carbamato polynuclear complexes also obtained. Iron(III) chloride reacts with potassium 2-prqpanenitronate, K(pn), to give [Fe(Me2C=N02)3] (mean Fe—0 = 2.019 A, mean bite angle 66.0 A), which in ethanol gives binuclear [(pn)2Fe(//-OEt)2Fe(pn)2]. ... 

The spectra of copper(II) complexes with R-dtp ligands remain an unsettled problem in view of the tendency of Cu(R-dtp)2 complexes to disproportionate. The recent discussion 3 4) of the energy levels of 6is(diethyldithio-carbamato)copper(II) may serve as a useful starting point for discussions of the spectra of Cu(R-dtp>2 compounds. 

Reactions of Cr(NEt2)4, some examples of which have been discussed elsewhere, are presented in Scheme 119. The unusual reactions with C02, which produce the chromium(III) and chromium(II) carbamato complexes (287) and (288), are believed163 to proceed by C02 insertion into a Cr—N bond, which promotes /3-hydrogen elimination from a coordinated diethylamido ligand, and then reductive elimination of Et2NH produces a reactive chromium(II) species Crn(02CNEt2)(NEt2). The subsequent reaction is dependent upon the relative concentration of C02. 

The phenomenon of spin equilibrium in octahedral complexes was first reported by Cambi and co-workers in a series of papers between 1931 and 1933 describing magnetic properties of tris(iV,iV-dialkyldithio-carbamato)iron(III) complexes. By 1968 the concept of a thermal equilibrium between different spin states was sufficiently well established that the definitive review by Martin and White described the phenomenon in terms which have not been substantially altered subsequently (112). During the 1960s the planar-tetrahedral equilibria of nickel(II) complexes were thoroughly explored and the results were summarized in comprehensive reviews published by Holm and coworkers in 1966 and 1973 ( 79, 80). Also, in 1968, Busch and co-workers... 

An analogous process for the formation of carbamato derivatives containing the Mo=Mo unit from the reactions of l,2-Mo2R2(NMe2)4 compounds [R = CH3 and CH2Si(CH3)3] with carbon dioxide has been reported by Chisholm and co-workers (99, 100). That is, the insertion of C02 into... 

The synthesis of hydroxycarbamates from secondary aliphatic amines, C02 and epoxides has been found to be catalyzed by (5,10,15,20-tetraphenylporphinato) aluminum(III) acetate, AI(TPP)(02CCH3) [80], Scheme 6.14 illustrates the mechanism proposed for the catalytic process, which can be carried out under not severe conditions (293-343 K 0.1-5 MPa C02 pressure). The key step here is the insertion of epoxide into the Al-O bond of the A1-carbamate A (Scheme 6.14), which preliminarily forms by the reaction of A1(TPP)(02CCH3) with the amine and C02. Protolytic cleavage of the Al-alkoxide bond in the insertion product, C, by dialkylcarbamic acid regenerates the catalytkally active carbamato-species A and... 

Silver(n) and Silvery hi).—The cationic complex bis-(2,2, 2"-terpyridyl)Ag2+ has been isolated as its peroxydisulphate salt.217 The presence of a d-+d band at 15600 cm-1 is indicative of a six-co-ordinate ion. X-ray photoelectron spectra have provided Ag(3d5/2>3/2) binding energies for this complex and the mono-terpy complex. The influence of pyridine and 2-, 3-, and 4-picoline on bis(diethyl dithio-carbamato)AgH has been examined by e.s.r. spectroscopy.218 The results indicate formation of mono-addition products and the spin hamiltonian parameters for these complexes have been determined. 

D. Belli Dell Amico, F. Calderazzo, L. Labella, F. Marchetti, G. Pampaloni, Converting Carbon Dioxide into Carbamato Derivatives, Chem. Rev. 2003, 103, 3857-3897. 

Ureato and Carbamato Complexes. These can be made in a variety of ways such as the interaction of metal carbonyls with RNCO or RN3. A more general method involves the sequence218 ... 

They are good precursors to other divalent compounds. In the presence of C02 and an alkylamine they produce diamagnetic carbamato-containing complexes. 

Odeacylation does not occur with non-ester protecting groups such as a carbamato group. 

If titanium-nitrogen and titanium-oxygen bonds arc available in the same molecule, CO insertion yields carbamates [104]. If carbon dioxide has the capability (0 insert into a metal-carbon or a metal-nitrogen bond, the insertion into M-N is preferred hafnium dialkyl diarnides react with CO at room temperature to yield the carbamato derivatives HfRjfOjCNR ) [105). 

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