Daniela Belli Dell’Amico

Isolation and structural determination of two derivatives of the elusive carbamic acid

The dibenzyl-substituted carbamic acid (PhCH2)2NC(O)OH (1), its deprotonation product [(PhCH2)2NH2]- [(PhCH2)2NCO2] (2) and CoCl(NO)2[PhP(OCH2CH2)2NC(O)OH ]·2MeCOMe(3·2MeCOMe) are reported, the diffractometric study showing the carbamic acids 1 and 3 to be paired through hydrogen bonds.

Triphenylphosphine-substituted N,N-di-iso-propylcarbamate of ruthenium(II) and its reactions with carbon monoxide

Abstract Chloride displacement from RuCl 2 (PPh 3 ) 3 by NH i Pr 2 /CO 2 in toluene as medium gave the N , N -di- iso -propylcarbamato derivative Ru(O 2 CN i Pr 2 ) 2 (PPh 3 ) 2 , ( 1 ), whose X-ray crystal structure determination showed the mononuclear compound to contain hexacoordinated ruthenium bonded to bidentate carbamato and to cis -arranged tertiary phosphine groups in a distorted octahedral geometry. Carbonylation at room temperature rapidly converted 1 to the monocarbonyl derivative Ru(O 2 CN i Pr 2 ) 2 (PPh 3 ) 2 (CO) ( 2 ), presumably containing a monodentate carbamato group, the dicarbonyl compound Ru(O 2 CN i Pr 2 ) 2 (PPh 3 ) 2 (CO) 2 ( 3 ) being formed over longer reaction times. X-ray diffraction data showed 3 to contain hexacoordinate ruthenium(II) with monodentate carbamato groups trans to the carbonyl groups and with trans -arranged triphenylphosphine groups. Controlled hydrolysis of 3 yielded the dicarbonyl-carbonato complex Ru(O 3 C)(PPh 3 ) 2 (CO) 2 ·H 2 O ( 4 ), crystallographically established to contain a bidentate carbonato group, trans triphenylphosphine ligands and water hydrogen-bonded to the carbonato ligand.

N,N-Dialkylcarbamato complexes as precursors for the chemical implantation of metal cations on a silica support. Part 3 Palladium

Chemical implantation of palladium(II) has been carried out under mild conditions by reacting trans-Pd(O 2 CNEt 2 ) 2 (NHEt 2 ) 2 with the silanol groups of amorphous silica, carbon dioxide and secondary amine being released in the process. The palladium-containing silica has been characterized and the coordination environment of the implanted cation has been defined by 13 C CP MAS NMR, DRIFT and XPS spectra, and by WAXS measurements. Silica-bonded palladium(II) was reduced thermally in vacuo or with dihydrogen at room temperature. Catalytic activity in the hydrogenation of cyclohexene was found for all samples containing the silica-supported reduced palladium; the best results, with rates independent of olefin concentration, were found for the samples treated thermally (200°C) under reduced pressure.

Reaction of a tetranuclear N,N-di-iso-propylcarbamato complex of cerium(III) with dioxygen: synthesis and X-ray characterization of both the oxidation product and its precursor

Abstract The tetranuclear N,N-di-iso-propylcarbamato complex of cerium(III) Ce 4 ( O 2 CN i Pr 2 ) 12 , 1, has been synthesized and its crystal structure solved through X-ray diffraction methods. The oxidation of the cerium(III) complex by dioxygen produces the μ3-oxo tetranuclear cerium(IV) derivative Ce 4 ( μ 3 - O ) 2 ( O 2 CN i Pr 2 ) 12 , 2, which has been characterised by single crystal X-ray diffractometry. Structural rearrangements on going from the cerium(III) derivative to the corresponding cerium(IV) product have been established. This is the first case of a μ-oxo-carbamato complex being obtained by oxygenation, whereby product and precursor maintain the basic structural features.

N,N-dialkylcarbamato metal complexes, molecular inorganic precursors to functionalized inorganic matrices

Abstract The relatively new class of the N,N-dialkylcarbamato metal complexes, of general formula [M(O2CNR2)n]m, n and m being the oxidation number of the central metal atom M and the nuclearity of the system, is reviewed with particular attention to compounds of Main Group elements (particularly tin, silicon and aluminium), and of transition d- and f-metals. Synthetic procedures and structural properties of the homoleptic compounds (i.e., compounds in which the set of anionic ligands is constituted by the monoanionic O2CNR2(−) ligand exclusively) are reported, also in relation to the results obtained by other research groups in this area. The reactivity of these systems is reported in connection with: (a) homoleptic derivatives; (b) non-homoleptic N,N-dialkylcarbamato complexes; (c) controlled hydrolysis of the homoleptic precursors to μ-oxo derivatives; (d) N,N-dialkylcarbamato complexes as reactive species towards surface hydroxyl groups, whereby Si–O–M linkages can be formed; (e) exhaustive hydrolysis of the N,N-dialkylcarbamato complexes; (f) metal N,N-dialkylcarbamato complexes as reactive intermediates to organic products. The literature references to papers originated from this research group can be found in the web site of the University of Pisa ( http://www.dcci.unipi.it/∼facal/ICA-BIB.htm ).

Carbonyl Derivatives of Gold and Related Organometallics

The properties and reactions of simple gold carbonyls and related compounds are described and the bonding within the gold carbonyl molecules discussed in terms of bond dissociation enthalpies.

Smart Grafting of Lanthanides onto Silica via N,N-Dialkylcarbamato Complexes.

The grafting and the postgrafting functionalization of lanthanide ions on commercial amorphous silica have been herein carried out by using as a precursor the terbium N,N-dibutylcarbamato derivative [Tb(O2CNBu2)3]. The reaction of the complex with the surface silanols involved only a fraction of the carbamato ligands. The following protolytic substitution of the residual carbamato ligands was carried out by exploiting the Brønsteds acidity of the β-diketone dibenzoylmethane (Hdbm), in view of the antenna effect of the β-diketonato groups, which are commonly used in lanthanide photoluminescence studies. The reaction proceeded at room temperature in a clean and easy way affording the introduction of the chosen functionality in the lanthanide coordination sphere. The same procedure has been followed by using as a precursor the X-ray characterized heterometallic N,N-dibutylcarbamato complex [NH2Bu2]2[Ln4(CO3)(O2CNBu2)12] (Ln = Eu, Tb, Tm). In both cases, X-ray photoelectron spectroscopy evidenced the chemical implantation of the lanthanide ions on the silica surface, and photoluminescence studies pointed out the potentiality of the proposed synthetic approach in the preparation of highly luminescent materials.

Preparation of N,N-Dialkylcarbamato Lanthanide Complexes by Extraction of Lanthanide Ions from Aqueous Solution into Hydrocarbons

Lanthanides are easily extracted as N,N-dibutylcarbamato complexes from aqueous solutions of their chlorides into heptane solutions of dibutylamine saturated with CO2. The products are recovered in high yields and are soluble in hydrocarbons. The derivatives [Ln(O2CNBu2)3]n [Ln = Nd (1), Eu (2), Tb (3)], [NH2Bu2]2[Ln4(CO3)(O2CNBu2)12] [Ln = Tb (4), Sm (5), Eu (6)], and [Sm4(CO3)(O2CNBu2)10], 7, have thus been obtained. The crystal and molecular structure of 4 has been solved; the samarium and europium complexes 5 and 6 were found to be isostructural. Mass spectra of the complexes 1-3, 4, and 7 (in MeCN/toluene) reveal that equilibria are present in solution. Compound 2 has been reacted in toluene with NHBz2 in the presence of CO2 affording [NH2Bz2][Eu(O2CNBz2)4], 8, through a ligand exchange process. By thermal treatment, 8 afforded [Eu(O2CNBz2)3]n, 9. With a similar procedure [Sm(O2CNBz2)3]n, 10, was obtained from 5. According to the photoluminescence study carried out on solid samples of 2, 4, 5, 7, and 8, the metal centered f-f transitions represent the only effective way to induce lanthanide luminescence in these complexes.

Synthesis, antiproliferative and mitochondrial impairment activities of bis-alkyl-amino transplatinum complexes.

A convenient synthetic route and the characterization of complexes trans-[PtCl2(L)(PPh3)] (L=Et2NH (2), (PhCH2)2NH (3), (HOCH2CH2)2NH) (4) are reported. The antiproliferative activity was evaluated on three human tumor cell lines. The investigation on the mechanism of action highlighted for the most active complex 4 the capacity to affect mitochondrial functions. In particular, both the induction of the mitochondrial permeability transition phenomenon and an aspecific membrane damage occurred, depending on concentration.

New trans dichloro (triphenylphosphine)platinum(II) complexes containing N-(butyl),N-(arylmethyl)amino ligands: Synthesis, cytotoxicity and mechanism of action

Some new platinum(II) complexes have been prepared, of general formula trans-[PtCl2(PPh3){NH(Bu)CH2Ar}], where the dimension of the Ar residue in the secondary amines has been varied from small phenyl to large pyrenyl group. The obtained complexes, tested in vitro towards a panel of human tumor cell lines showed an interesting antiproliferative effect on both cisplatin-sensitive and -resistant cells. For the most cytotoxic derivative 2a the investigation on the mechanism of action highlighted the ability to induce apoptosis on resistant cells and interestingly, to inhibit the catalytic activity of topoisomerase II.