Carla Ferragina

Oxidative carbonylation of aniline catalyzed by Pd(II)-2,2'-bipyridyl complex intercalated in α-zirconium-phosphate

Abstract Palladium(II) and palladium(II)-copper(II) complexes (with N-donor ligands intercalated between the layers of α-zirconium phosphate) have been employed in the oxidative carbonylation of aniline. The catalytic activity of the materials has been studied together with the properties of α-zirconium phosphate as a supporting agent. Their very low activity observed in an initial induction period slowly increases to more marked levels in mild working conditions (80 °C, atmospheric pressure); in more drastic conditions diphenylurea and methyl carbamate are produced in a non-selective way due to a concomitant oxidation of aniline. By pre-heating the materials at 130 °C under CO or CO/O2, an increase of the catalytic activity is obtained, and the treated systems are able to catalyze selectively the carbonylation of aniline in mild conditions. By submitting the pretreated systems to a series of catalytic cycles and by re-employing the same catalyst in each cycle, a decrease in activity is observed until complete deactivation of the catalyst, when Pd is almost completely eliminated by the solid. On the basis of the analysis of the pretreated sample before and after deactivation, this behaviour is ascribed to migration of the Pd from the inner layers to the surface of the solid matrix and to its subsequent solubilization in the reaction medium.

Coordination of Co2+, Ni2+ and Cu2+ to 2,9 - dimethyl - 1,10 phenanthroline intercalated in α-zirconium phosphate: Evidence for dimers

2,9-Dimethyl-1,10-phenanthroline (dmp) intercalates into α-Zr(HPO4)2. (2EtOH) to form α-Zr(HPO4)2 (dmp)0.50. 2.5H2O at maximum uptake, at 25°C. This lamellar composite has an interlayer distance of 14.60(5) A, which changes little - to 13.58(5) A - when the pseudo-zeolitic water is lost. An almost vertical orientation of the dmp between the phosphate layers is proposed, as was found previously for the unsubstituted phenanthroline analogue. When the material is exchanged with Co2+, Ni2+, and Cu2+, under conditions such that [M] : [L] = 1:1 there is partial elution of the dmp, giving rise to materials of formulation α-ZrH1.3M(OH2)0.35(dmp)0.35(PO4)2·nH2O, with no change in interlayer distance. Spectroscopic evidence for the formation of dimers to the intercalated dmp is described.

Rh3+ and Rh3+–diamine complexes intercalated in γ-titanium hydrogen phosphate. Synthesis, characterisation and catalytic activity towards aniline oxidative carbonylation processes

Abstract New materials containing Rh(III) ions or Rh(III)–diamine complexes [(L=2,2′-bipyridyl (bipy); 1,10-phenanthroline (phen); 2,9-dimethyl-1,10-phenanthroline (dmp)] intercalated in γ-titanium phosphate (γ-TiP) are described. The compounds have formula γ-TiPHxRhy·tH2O (x=2–3y; 0

Pillar chemistry. Part 5. Intercalation of 2,2′-bipyridine, 1,10-phenanthroline, and 2,9-dimethyl-1,10-phenanthroline into γ-zirconium phosphate and formation of interlayer copper(II) complexes

2,2′-Bipyridine (bipy), 1,10-phenanthroline (phen), and 2,9-dimethyl-1,10-phenanthroline (dmphen) can be intercalated into γ-Zr(HPO4)2·2H2O as such (i.e. without first pre-swelling the matrix) to give materials having the final formulation γ-Zr(HPO4)2Lx·n H2O (x= 0.48–0.50). With dmphen, if the γ-Zr(HPO4)2·2H2O is first pre-swelled using ethanol, a further, pure layered phase of composition γ-Zr(HPO4)2(dmphen)0.28·2H2O is obtained; bipy and phen do not give this latter phase. Indirect evidence, X-ray diffraction and i.r. spectroscopy, indicates that the orientations of the amines in the interlayer are different from those in the α-Zr(HPO4)2·H2O analogues, probably due to the presence of specific hydrogen bonding by the interlayer water molecules. All four materials exchange CuII. As expected, given its lower interlayer ligand density compared with the other materials, γ-Zr(HPO4)2(dmphen)0.28·2H2O takes up CuII most readily. Further, within the series γ-Zr(HPO4)2Lx·n H2O the order of uptake, phen > dmphen > bipy, is not that expected from ligand steric requirements alone and the uptake is in all cases slower than that in the α-Zr(HPO4)2·H2O analogues, both results indicating the importance of ligand–matrix interactions. The final pure layered materials obtained have [Cu2+]: [] ratios of 1:1 [γ-(dmphen)0.28] and 1:2 [γ-dmphen)0.48 and γ-(bipy)0.48]; γ-(phen)0.50 gave [Cu2+] : []= 0.8:1. Spectroscopic evidence shows that CuII co-ordinates to the amine ligand only in the bipy and phen cases, whereas both dmphen-containing materials exchange Cu2+ into cavities widened by the dmphen but without co-ordination to the intercalated ligand.

XPS studies on the host-guest interaction of 2,2′-Bipyridyl, 1,10-phenanthroline and 2,9-dimethyl-1,10-phenanthroline intercalated inα-zirconium phosphate

The host-guest interactions of 2,2′-bipyridyl, 1,10-phenanthroline and 2,9-dimethyl-1,10-phenanthroline intercalated between the layers of crystallineα-zirconium monohydrogen phosphate have been studied by X-ray photoelectron spectroscopy. Evidence that, on average, only one of the two nitrogen atoms of each aromatic diamine is protonated by the ≡P-OH groups of the host is given. The acid-base interaction is strongly reduced on dehydration of the materials. The role of the cointercalated water is discussed, together with the probable disposition of the guests within the interlayer region.

XPS characterization ofγ-zirconium phosphate and of some of its intercalation compounds. A comparison with the α-zirconium phosphate analogues

An X-ray photoelectron spectroscopic investigation ofγ-Zr (HP04)2·2 H2O and its intercalation compounds with 1,10-phenanthroline, Co2+-phenanthroline and Cu2+-phenanthroline is described. The analysis of theNls spectra of the compound containing only phenanthroline clearly shows that, on average, more than one nitrogen atom of the diamine interacts with the acid groups of the host, giving protonated species. XPS also provides evidence of the coordination of Co2+ and Cu2+ ions after their diffusion in the phenanthroline-γ-zirconium phosphate intercalation compound. They form mixed N-and O-coordinated species with the diamine and the oxygens of the interlayer region, but the presence of the characteristic peaks of uncoordinated phenanthroline, even at low intensity, shows that the diamine molecules anchored to the host are still present.A comparison is made with the analogous derivatives of α-Zr (HPO4)2·H2O and the differences between the two series of compounds are discussed.

Pillaring of layers in α-zirconium phosphate by 1,10-phenanthroline and bis(1,10-phenanthroline)copper(II): formation of complex pillars in situ

The complex [Cu(phen)2]2+(phen = 1,10-phenanthroline) can be diffused between the layers of α-zirconium phosphate only if the layers are first pre-swelled by preparing the diethanol intercalate, α-Zr(HPO4)2(EtOH)2. At maximum uptake a material of formula α-ZrH1.6[Cu(phen)2]0.20(PO4)2·3H2O is obtained and no further complex can be intercalated. X-Ray and spectroscopic evidence show that the [Cu(phen)2]2+ remains intact after intercalation, and probably has a tetragonal-octahedral geometry. A ‘complex pillared’ layer structure is still present after the zeolitic water has been removed. However, the geometry adopted by the [Cu(phen)2]2+ is now square-based pyramidal, and it is bonded asymmetrically between the phosphate layers. Further ions (Cu2+, Pd2+, or Ag+) can be exchanged into the pillared cavities, to form solid solutions. 1,10-Phenanthroline itself diffuses into α-Zr(HPO4)2(EtOH)2 to form the ‘intercalated ligand’ phase α-Zr(HPO4)2(phen)0.50·2H2O at maximum uptake. This is a pure, well ordered Stage I phase with an interlayer distance of 13.58 A, and it is suggested that the phen is ordered throughout the layers in a ‘slanted’ fashion. This phase exchanges Co2+, Ni2+, and Cu2+(in the order Cu2+ Co2+ > Ni2+) much more slowly than does the 2,2′-bipyridyl analogue, due to the steric hindrance caused by the bulkier ligand backbone and higher pillar density. Only in the case of Cu2+ does subsequent co-ordination to the phen proceed to complete formation of α-ZrH [Cu(phen)]0.50(PO4)2·3H2O. In the cobalt and nickel analogues there is competition between phen-co-ordinated and cavity-co-ordinated metal ion. Spectroscopic evidence (u.v.–visible, e.s.r.) is presented which shows that these complex pillars formed in situ have very distorted geometries, caused by the steric constraints imposed by the interlayer region.

Intercalation compounds of α-zirconium hydrogen phosphate with RhIII ions and RhIII-diamine complexes. Part 1.—Preparation, thermal behaviour and X-ray photoelectron spectroscopy investigation

Rhodium(III) can be exchanged between the layers of α-zirconium phosphate by employing the pre-swelled diethanol intercalate, α-Zr(HPO4)2(ethanol)2. During the Rh3+/H+ exchange, four rhodium-containing phases are formed with different interlayer distances. However, only the fully Rh-exchanged compound, α-ZrRh0.66(PO4)2.4H2O, is obtained as a pure phase. Rhodium(III) can also be exchanged into the layered intercalation compounds α-Zr(HPO4)2(bipy)0.251.5H2O (bipy = 2,2′-bipyridyl), α-Zr(HPO4)2(phen)0.52H2O (phen = 1,10-phenanthroline) and aZr(HPO4)2(dmp)0.5·2.5H2O (dmp = 2,9-α-dimethyl-1,10-phenanthroline). Exchange is accompanied by a partial elution of the diamine for the phen and dmp derivatives. Various materials are obtained and their thermal properties discussed. X-Ray photoelectron spectroscopy (XPS) gives evidence that RhIII-diamine complex species mixed N- and O-coordinated RhIII are formed in the interlayer region of the three intercalation compounds.

Phenylacetylene carbonylation catalysed by Pd(II) and Rh(III) intercalated in zirconium phosphates

Palladium(II) and rhodium(III) ions, or palladium(II) complexes (Pd-L) with bidentate N-donor ligands such as 2,2-bipyridyl (bipy) and 1,10-phenanthroline (phen), intercalated in the layers of zirconium hydrogen phosphate, in a or y phases (a- or γ-ZrP), catalyze both single and double metnoxo-carbonylation of phenylacetylene. The monocarbonylation products, PhC(COOCH 3 )=CH 2 (1) and its regio isomer PhCH=CH(COOCH 3 ) (2) are obtained when phenylacetylene reacts, in methanol, under C() pressure (1-4 MPa). at temperatures of 80-130°C. When the reaction is carried out under oxidative conditions using a CO/O 2 mixture, double-carbonylation products are obtained as well as monofunctionalized phenylacetylene. The double-carbonylation product PhC (COOCH 3 )=CH(COOCH 3 ) (3) and the corresponding anhydride PhCCO(O)=CHCO (4) are obtained when the process is carried out with a CO/O 2 mixture under pressure (2-4 MPa; pO 2 =0.8 MPa) at 60-100°C, using methanol or acetonitrile as solvent. When the reaction is carried out in the presence of tertiary amines such as NEt 3 or NPh 3 , under mild pressure conditions (0.4-0.7 MPa) at 60-90°C, the triple bond remains unchanged and the monocarboxylate PhC=CCOOCH 3 (5) is isolated. Compound 5 is also prepared in a neutral medium when γ-Zr-Rh 3 is used as catalyst.

Intercalation of 2,2′-bipyridyl, 2,4′-bipyridyl and 4,4′-bipyridyl into γ-zirconium phosphate. physical–chemical characterization and solvent effect on the intercalation

Abstract The uptake into γ-zirconium phosphate by batch method of 2,2′-bipyridyl, 2,4′-bipyridyl, and 4,4′-bipyridyl in ethanol:water solutions of various solvent ratios has been studied. The obtained materials were examined by powder X-ray diffraction (PXRD), thermogravimetric and differential thermal analysis (TG-DTA) techniques, and UV-vis, IR and Raman spectroscopy. It has been found that the ligand content into the exchanger depends on batch temperature, ligand:exchanger ratio in the contact batch, ethanol:water solvent ratio, and isomeric nitrogen position in the diamines. The highest uptake was obtained for the ligand 2,2′-bipyridyl with an ethanol:water ratio of 1:9.