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The films of magnesium boride were grown on Si(100) substrate by chemical vapor deposition, starting from the synthesis of the single-source precursor Mg(BH 4 ) 2 . The deposition time was varied to study its influence on the film composition. The chemical composition of produced samples was investigated by the XPS technique. The depth profiling of MgB x films was carried out by using Ar ion sputtering combined with cyclic XPS measurements. The contributions of different chemical species (boride and oxides) in the depth profiles were separated by peak-fitting analysis of photoelectron B 1s and Auger Mg KLL spectra. In order to determine the correct parameters of peak fitting, the reference samples of MgB 2 and MgO were studied as well. The produced samples were composed of MgB x film covered by an overlayer of magnesium and boron oxides, whose thickness was increasing with deposition time. The surface of the films was enriched with magnesium, while the volume was characterized by the B : Mg ratio exceeding 2. XPS results confirmed that the bulk decomposition of Mg(BH 4 ) 2 precursor was successful; therefore, some other phenomenon, such as Mg segregation, was responsible for the formation of MgB x films with x > 2. In addition, a prolonged deposition time resulted in a thicker surface overlayer of Mg and B oxides, but it did not change the stoichiometry of the boride film.

Metal Organic Chemical Vapor Deposition of cubic stabilized zirconia was investigated by the addiction of the alkaline-earth oxides MgO and CaO. While Cp 2 ZrMe 2 [(Cp = –C 5 H 5 , Me = –CH 3 )] was used as precursor for ZrO 2 , two different Mg compounds were tested for the MgO deposition, namely bis-(η 5 -methylcyclopentadienyl)Mg(II) [(Mg(Cp-Me) 2 ] and bis-(2,2,6,6-tetramethyl-3,5-heptanedionate)(tetramethylethylenediamine)Mg(II) [Mg(tmhd) 2 ·tmeda]. Bis-(2,2,6,6-tetramethyl-3,5-heptanedionate)(triethyleneglycoldimethylether)Ca(II) [Ca(tmhd) 2 ·triglyme] was used for CaO growth. Depositions were carried out on fused quartz at 500 °C, yielding colorless and crack-free films well adherent to the substrates. A thorough characterization of their microstructure and chemical composition was obtained by the combined use of XRD (X-ray Diffraction), XPS (X-ray Photoelectron Spectroscopy) and EDXS (Energy Dispersive X-Ray Spectroscopy). The obtained results indicated a complete stabilization of zirconia in its cubic-fluorite phase when the magnesium and calcium content ranged from 12 to 30 at.% and from 17 to 38 at.%, respectively.

Unsymmetrically substituted dimethyldiaminosilanes of the general formula SiMe2(NR2)(NR′2) have been prepared by treating LiNR2 with SiMe2Cl(NR′2) (NR2, NR′2 = NMe2, NC4H8, NHiPr, NHtBu, NHCH2CH2NMe2 or NHCH2CH2OMe). Their ligating properties towards zirconium(IV) have been investigated as a function of the nitrogen substituents and the syntheses of the binary compound Zr[SiMe2(NiPr)(NtBu)]2 and of the zirconium derivatives ZrX3(L) [X = Cl, NMe2; L = SiMe(NR)(NR′2), NR = NiPr, NtBu, NCH2CH2NMe2, NCH2CH2OMe; NR′2 = NMe2, NC4H8, NHiPr, NHtBu] are also reported. The solution structures and dynamics of the compounds have been elucidated by 1D/2D multinuclear NMR spectroscopy. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Thin film depositions of metallic silver were performed by the MOCVD (Metal Organic Chemical Vapor Deposition) technique on glass substrate using, as precursors, the two new compounds (1,1,1,5,5,5-hexafluoro-2,4-pentanedionato)(2,2’-bipyridine)silver(I), [Ag(hfac)(bipy)] (1), and (1,1,1,5,5,5-hexafluoro-2,4-pentanedionato)(N,N,N’,N’-tetramethylethylenediamine)silver(I), [Ag(hfac)(tmeda)] (2). Both silver compounds were characterized by single crystal X-ray diffraction measurements, indicating that 1 exists as a dimeric species, and 2 as polymeric chains. The films were analysed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) revealing, a high crystallinity and fairly good quality with little carbon and oxygen contamination when using the tetramethylethylenediamine derivative

The functionalised diaminodimethylsilanes SiMe2[NH(CH2)nX]2 (X = NMe2, n = 2, H2L1; n = 3, H2L2; X = OMe, n = 2, H2L3; n = 3, H2L4) have been synthesised by aminolysis of SiMe2Cl2 with NH2(CH2)nX, and their ligating ability towards zirconium(IV) has been investigated. The syntheses of [ZrY2(L)] (Y = Cl, NMe2, Me; L = L1, L2, L3, L4) are reported and the solid-state structures of some selected compounds determined by X-ray crystallography. In addition, the solution molecular structures of all the metal derivatives have been elucidated by variable-temperature multinuclear 1D/2D NMR spectroscopy, and the dynamics have been investigated in some selected cases. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

The new η 2 -formamidinyl Zr complex Zr(NMeCyc) 2 [C(NAr)NMeCyc] 2 (1) (Ar = 2,6-dimethylphenyl, Cyc = cyclohexyl) was prepared upon double insertion of 2,6-dimethyl phenyl isocyanide in the Zr-N bond of Zr(NMeCyc) 4 . 1 wasthen converted into Zr(OC 6 F 5 ) 2 [C(NAr)N-MeCyc] 2 (2) and ZrCl 2 [C(NAr)NMeCyc] 2 (3) by reacting it with C 6 F 5 OH and [NHMe 3 ]Cl, respectively. The crystal structure of 1 was established by X-ray analysis. All the complexes have been tested as catalysts for the polymerization of ethylene and 1-hexene in the presence of [NHMe 2 Ph][B(C 6 F 5 ) 4 ] as cocatalyst.

The salts Li[Al(C4H8N)4]·nC4H8NH (n = 1, 2; C4H8NH = pyrrolidine) have been prepared and characterised in solution by 1H-, 13C-, 7Li- and 27Al-NMR spectroscopy. Their reaction with AlCl3 (Cl/Li molar ratio = 3) affords the binary amido derivative [Al(C4H8N)3]2, which, on turn, is reactive towards AlX3, yielding [AlX2(C4H8N)]2 (X = Cl, CH3). The binuclear derivatives [AlY2(C4H8N)]2 (Y = Cl, CH3, C4H8N) react with [NH2Et2]Cl affording the amine complexes AlY2Cl(C4H8NH)n (Y = CH3, n = 1; Y = Cl, n = 1, 2). Alternatively, the monochloro species Al(CH3)2Cl(C4H8NH) results from the reaction of Al(CH3)3(C4H8NH) and AlCl3(C4H8NH) (CH3/Cl molar ratio = 2). The dichloro-methyl derivative Al(CH3)Cl2(C4H8NH) is obtained by reacting Al(CH3)3(C4H8NH) and AlCl3(C4H8NH) (Cl/CH3 molar ratio = 2). The Lewis adducts AlCl3(amine)n (amine = pyrrolidine, n = 1, 2; amine = N,N,N′-trimethylpropanediamine, n = 1) have been isolated when AlCl3 was contacted with the stoichiometric amount of the amine. At variance with N,N,N′-trimethylpropanediamine, N,N,N′-trimethylethylenediamine and N,N,N′,N′-tetramethylethylenediamine react with AlCl3 yielding the salt derivatives [AlCl2(amine)2][AlCl4]. The dynamic processes of the coordinated amine ligands of AlCl3(amine)n (amine = pyrrolidine, n = 1, 2; amine = N,N,N′-trimethylpropanediamine, n = 1) and [AlCl2(amine)2][AlCl4] (amine = N,N,N′,N′-tetramethylethylenediamine) have been investigated in solution by NMR spectroscopy.

The silicon compounds SiMe2(NRR′)2 [NRR′ = NMe2 (1), NEt2 (2), NC4H8 (3), NHEt (4), NHiPr (5), NHtBu (6), NMeBu (7)] have been synthesised via aminolysis of the dichloro species SiMe2Cl2 and their ligating ability has been investigated towards zirconium(IV). The dimer zirconium compound {Zr[(NiPr)2SiMe2]2}2 (8) has been synthesised by reacting ZrCl4 with the lithium salt Li2[(NiPr)2SiMe2] and its molecular structure has been determined in the solid state by X-ray diffraction analysis. The reaction of ZrCl4 with SiMe2(NRR′)2 yields the Lewis adducts ZrCl4[(NRR′)2SiMe2] [NRR′ = NMe2 (10), NC4H8 (11), NHEt (12), NHiPr (13), NHtBu (14), NMeBu (15)]. On the other hand, the mixed amido derivative Zr(NMe2)3(NHMe)[(NtBu)SiMe2(NHtBu)] (9) has been obtained from the reaction of Zr(NMe2)4 with SiMe2(NHtBu)2. The solution molecular structure and dynamics of the zirconium derivatives have been elucidated by 1D and 2D multinuclear NMR spectroscopy.

The aminolysis of the Si–Cl bond in SiCln(NR2)4−n (n = 1, 2, 3, 4) has been employed for the synthesis of binary amido, chloro–amido or mixed amido derivatives, depending on the nature of the silicon derivative and of the amine. The kinetics of the reaction have been investigated in some representative cases, i.e. SiCl4 + NHiPr2, SiCl(NMe2)3 + NH2iPr, SiCl2(NEt2)2 + NH2iPr, showing that the rate law is first-order with respect to the silicon compound and does not depend on the concentration of the amine. Moreover, the activation parameters of the reaction of SiCl2(NEt2)2 with NH2iPr have been determined. The ligand exchange reaction between SiCl4 and SiCln(NR2)4−n yields a number of chloro–amido derivatives, whose composition is strictly determined by the molar ratio of the reactants. The kinetics of the reaction between SiCl4 and SiCln(NR2)4−n were investigated for n = 3, R = Me, and n = 2, R = Et. Moreover in the latter case the equilibrium and activation parameters have been determined.

A series of new bis(indenyl) zirconium diaryloxides of general formula Ind2Zr(OL)2 (L = C6H5, 2; C6F5, 3; 2,6-Me2C6H3, 4; 2,4,6-Me3C6H2, 5; 4-tBuC6H4, 6) were synthesized by a metathesis reaction of Ind2ZrCl2 (1) with the appropriate thallium aryloxide salt, TlOL. The complexes 1–6 were characterized by 1H and 13C NMR techniques. They were also examined as catalysts for ethene and 1-hexene polymerization with methylalumoxane as co-catalyst, and a trend of the polymerization activity as a function of aryloxide ligands was observed. An interpretation of this trend, considering both the electronic and steric effects of the substituents on the aryloxide rings, was proposed. Copyright © 2001 John Wiley & Sons, Ltd.

SnO2 nanocrystalline thin films are deposited on Al2O3 and SiO2/Si(100) by chemical vapor deposition starting from diethylaminodimethylstannane (IV) [(CH3)2Sn(N(C2H5)2)2]. X-ray photoelectron spectra of the principal core levels for the surface of a SnO2 film on SiO2/Si(100) are presented.

Magnesium borohydride, Mg(BH4)2, a long-sought candidate for efficient hydrogen storage chemisorption technology, has been obtained in a pure and crystalline form by two new synthetic routes in a hydrocarbon solvent. A first synthetic approach involves a metathetical reaction between organometallic magnesium compounds; a second route consists of an insertion reaction of BH3 species, released from BH3.S(CH3)2, into the Mg-C bonds of MgR2, with complete replacement of R groups with BH4 groups. Both methods, based on commercially available reagents, afford identical, pure, polycrystalline materials, identified by X-ray diffraction as the so-called low-temperature hexagonal form of Mg(BH4)2, stable below 180 degrees C, recently shown to possess a complex, unpredictable, crystal structure.

The new solid-state complex {[Hf(NEt2)2Cl2(DME)] (DME = 1,2-dimethoxyethane)}, intermediate in the synthesis of the new bis-diethylamide bis-isopropoxy hafnium (IV) complex [Hf(NEt2)2(OiPr)2], has been synthesized, isolated and characterized by NMR spectroscopy and X-ray diffraction. The crystal structure showed the metal to be hexa-coordinated with a distorted octahedral geometry. Catalytic tests for the polymerization of ethylene have been carried out using this intermediate with [(NHMe2Ph)B(C6F5)4] as cocatalyst. The obtained polymer had a high molecular weight and a high melting point, characteristic of a high density polyethylene (HDPE).

Mass spectrometry has been employed as a diagnostic tool to investigate the decomposition of some zirconium cyclopentadienyl derivatives, namely dimethyl zirconium bis(cyclopentadiene) [(C5H5)2Zr(CH3)2] (1), dimethyl zirconium bis(methylcyclopentadiene) [(CH3C5H4)2Zr(CH3)2] (2) and bis(methylcyclopentadienyl) zirconium ditetrahydroborane [(CH3C5H4)2Zr(BH4)2] (3), used as precursors in the metallo-organic chemical vapour deposition (MOCVD) technique for ZrO2 thin films, as an alternative to the β-diketonates and alkoxides which represent the usually employed precursors. The measurements, performed both under electron ionization and electrospray ionization conditions, indicate that the most favoured decomposition channel involves the loss of the methyl or the tetrahydroborane ligands. For compounds 2 and 3 a more complicated decomposition mechanism, involving molecular rearrangements with formation of species containing intramolecular bonds by CH2 bridges, is observed. Copyright © 1998 John Wiley & Sons, Ltd.

The synthesis of homoleptic and heteroleptic alkylindium derivatives (generally as diethyl ether adducts) was carried out in high yields from InI3. The nuclear magnetic resonance and mass spectra of the compounds MenInEt3−n (n = 0, 1, 2, or 3) and of their trideuteromethyl analogues showed that both heteroleptic Me2InEt and MeInEt2 exist as single compounds, although disproportionation to InMe3 and InEt3 has been observed at temperatures slightly higher than room temperature. The crystal structure of unusual diphosphine-bridged adduct, [(InMe3)diphos(Me2InEt)] · [(InMe3)diphos(InMe3)], (diphos = (C6H5)2PCH2CH2P(C6H5)2 is reported.

The compounds Et2InNR2 (R  Me, Et, or SiMe3) and Et2InPyrr (HPyrr  pyrrole) have been prepared by reaction of Et2InCl with the corresponding lithium amide or pyrrolide in diethylether. Their 1H NMR, IR and mass spectra are reported and discussed. The amides are dimers in the vapour phase. Diethylindium bromide is a layer polymer. The octahedral coordination geometry of indium is characterized by four distinct InBr distances ranging from 2.777(2) to 3.848(2) A. Diethylindium pyrrolide has a chain structure as shown by the relatively short intermolecular interactions between each indium atom and the double bonds of two adjacent different pyrrole units (3.063(5) and 2.950(5) A, respectively). The indium coordination geometry is then trigonal bipyramidal, with the shortest bonds in the equatorial plane (InC(5) 2.143(5) A, InC(7) 2.141(5) A, InN 2.166(4) A).

Metal-organic chemical vapor deposition (MOCVD) can now be used routinely for the preparation of a wide variety of groups III-V semiconductor materials. Ga- and In-based binary (e.g., GaAs, InP), ternary (e.g., In(x)Ga(1-x)As), and quaternary (e.g., In(x)Ga(1-x)P(y)As(1-y) compounds may be prepared as epitaxial layers ranging in thickness from a few angstroms to several microns for device applications. However, an understanding of the chemistry involved in the gas phase and at growing surfaces during MOCVD is at a primitive level despite the progress of the past few years. In this account we shall review recent progress in the use of organometallic precursors for MOCVD. The purity of these starting materials will be considered in relation to the quality of resulting epitaxial layers. Reaction mechanisms involved in their decomposition and reactivity both in the gas phase and at substrate surfaces will be discussed. Carbon incorporation is comprehensively covered, and growth using alternative group III and group V precursors together with the decomposition reactivity of these reagents is reviewed. The prospects for chemists in this research field are excellent, and in our opinion they are essential to its further development and extension into hitherto unexplored territories.

Magnesium borohydride, Mg(BH4)2, a long-sought candidate for efficient hydrogen storage chemisorption technology, has been obtained in a pure and crystalline form by two new synthetic routes in a hydrocarbon solvent. A first synthetic approach involves a metathetical reaction between organometallic magnesium compounds; a second route consists of an insertion reaction of BH3 species, released from BH3·S(CH3)2, into the Mg−C bonds of MgR2, with complete replacement of R groups with BH4 groups. Both methods, based on commercially available reagents, afford identical, pure, polycrystalline materials, identified by X-ray diffraction as the so-called low-temperature hexagonal form of Mg(BH4)2, stable below 180 °C, recently shown to possess a complex, unpredictable, crystal structure.

The present communication is focused on the synthesis of the versatile heterobimetallic LaCo(ODiEt)5 (ODiEt = OC(CH2CH3)2CH2OCH3) alkoxide compound and on its innovative and unprecedented use as single-source precursor in the preparation of LaCoO3 films by both sol–gel and Chemical Vapour Deposition techniques. Nanostructured LaCoO3 films characterized by thermal stability of the perovskite structure up to 900 °C have been obtained thus evidencing the versatility of the adopted source compound. Morphological analysis revealed that high-quality smooth, well-adherent and crack-free layers have been prepared.

Magnesium titanium oxide thin films were deposited at 450 °C on fused quartz and Si (001) substrates by using the MOCVD technique, employing titanium tetra-isopropoxide Ti(OiPr)4 and bis-(η5-methylcyclopentadienyl)Mg(II) [(Mg(Cp-Me)2] as metalorganic sources. The Mg(Cp-Me)2 can be considered an unusual MOCVD precursor having never been used for this purpose to date. The as-grown samples, amorphous at this deposition temperature, became polycrystalline after an annealing treatment in air between 600 °C and 800 °C. The films were analyzed by XRD and RBS for a thorough characterization of their microstructure and chemical composition. The obtained results indicated the possibility to obtain the Mg2TiO4 (qandilite) or the MgTiO3 (geikielite) crystalline phases as a function of the input Mg/Ti molar ratio.

MnAs thin films were grown by metalorganic vapour-phase epitaxy (MOVPE) on GaAs(0 0 1), Si(0 0 1) and oxidised silicon substrates. All films are crystalline and contain only the ferromagnetic α-MnAs phase. X-ray diffraction (XRD) and atomic force microscopy (AFM) measurements show that films on GaAs(0 0 1) have strong preferential orientation, developing elongated grains parallel to [1 –1 0] GaAs while films on bare and oxidised Si are polycrystalline with irregular-shaped, randomly oriented grains. Magneto-optic Kerr effect (MOKE) measurements show good magnetic properties for films on GaAs, such as strong in-plane anisotropy and squareness of the hysteresis loop in the easy direction. A Curie temperature of 340 K, remarkably higher than the bulk material (315 K), was found for a 65 nm thick film on GaAs. Films grown on bare and oxidised silicon wafers had lower Curie temperature and were magnetically isotropic.

Thin films of chromia (Cr 2 O 3 ) for anti-wear protection were grown by metal-organic (MO)CVD on AISI 304 stainless steel, soda-lime glass, and (001) silicon substrates. The structural, morphological, and chemical compositions were compared for films grown by using three different, commercial, organochromium compounds; Cr(CO) 6 (1), Cr(III) (hexafluoroacetylacetonate) (2), and tris(2,2,6,6-tetra-methyl-3,5-heptanedionato) chromium (III) (3). The depositions were performed using a hot-wall reactor at 500 °C, under 3 torr, using N 2 as the carrier gas and O 2 mixed with water vapor as the reactant gas. The films were analyzed by X-ray diffraction (XRD), atomic force microscopy (AFM), Rutherford backscattering (RBS), nuclear reaction analysis (NRA), elastic recoil detection (ERD), X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared (FTIR) spectroscopy. The films grown with all three precursors on all three substrates were crystalline with hexagonal Cr 2 O 3 eskalonite structure. FTIR and XPS measurements confirmed the XRD results, showing IR absorption bands characteristic of Cr 2 O 3 and an oxidation state +3 of chromium. The highest growth rate was obtained with precursor (1) (20 nm min -1 ). Films grown with (1) on stainless steel were analyzed by nanoindentation measurements and scratch test to determine the hardness and the film adhesion.

The new β-diketonate complexes (hfac)2ZrCl2, (hfac)3ZrCl, hfac = hexafluoroacetylacetonate, and (thd)2ZrCl2, thd = 2,2,6,6-tetramethyl-3,5-heptanedionate, have been prepared in good yield by reacting the corresponding β-diketonate thallium complexes with ZrCl4 in stoichiometric amounts and they have been characterized by elemental analyses and NMR spectra. These complexes and the β-diketonate complexes (acac)2ZrCl2, (acac)3ZrCl and (thd)3ZrCl have been tested as catalysts in the polymerization of 1-hexene in the presence of N,N′-(dimethylanilinium)-tetrakis(pentafluorophenylborate) or ethyltrichloroacetate as co-catalysts at room temperature using ethyl aluminum sesquichloride as scavenger.

Amorphous alumina coatings of different thickness have been deposited on AISI 304 stainless steel substrates by MOCVD in a hot wall reactor at 380 °C under O 2 /H 2 O atmosphere. The used aluminium precursor was the high volatile and easy to prepare dimethyl-aluminum-isopropoxide. Selected films were annealed in N 2 and O 2 atmosphere at 500 and 700 °C to evaluate the effects of the thermal treatments on the morphology and on the nano-mechanical properties of the coatings. X-ray diffraction and Rutherford backscattering spectroscopy measurements indicated that both the as grown and annealed films were amorphous and very pure with the correct Al 2 O 3 stoichiometry. The surface morphology, investigated by atomic force microscopy, was free of cracks with a roughness of the films that increases with deposition time and with annealing in oxygen atmosphere. The hardness and the elastic modulus of the films and of the AISI 304 stainless steel substrate were measured by load-depth nano-indentation tests. The results highlighted a significant increase in the Berkovich hardness of the coated samples compared to that of the bulk AISI 304 stainless steel.

The interaction of dimethyldiaminosilane ligands of general formula SiMe2(NR2)(NR'2)(NR2, NR'2 = NiHPr, NHtBu, NC4H8, NHCH2CH2NMe2) with AlX3 (X = Cl, Me) has been investigated and the synthesis of novel aluminium derivatives is reported, namely AlMe3[SiMe2(NR2)(NR'2)], AlX2[SiMe2(NR)(NR'2)] and AlMe[SiMe2(NR)2], containing the silane ligand as neutral, monoanionic and dianionic species, respectively. Moreover, the solution molecular structures and dynamics have been elucidated via 1D/2D variable temperature NMR spectroscopy showing the influence of the N-substituents of the silane ligand and of the aluminium ancillary ligands.

Cobalt aluminate (CoAl 2 O 4 ) thin films were grown in a low-pressure hot wall metal organic chemical vapour deposition (MOCVD) reactor on Si(1 0 0) and quartz substrates with a total pressure of 2 Torr using bis(η 5 -cyclopentadienyl)Co(II) (Co(η 5 -C 5 H 5 ) 2 ] and aluminium dimethylisopropoxide [AlMe 2 (O i Pr)] as precursors at 500 and 900 C. Films showed a dark-brown and dark-green colouration, respectively, and after an overnight heat treatment in air at 1200°C, they turned blue. Film microstructure, composition and morphology were investigated in detail by X-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS), scanning electron microscopy (SEM) and secondary ion mass spectrometry (SIMS) analyses. Films were polycrystalline and the UV-vis spectra showed three electronic transitions allowed by the spin (540-630 nm range) characteristic of Co(II) ions with 3d 7 configuration in tetrahedral coordination. SEM micrographs of the heat-treated CoAl 2 O 4 samples revealed the presence of agglomerated crystallites with a highly porous structure.

Zirconia (ZrO 2 ) titania (TiO 2 ) and alumina (Al 2 O 3 ) thin films were deposited on a graphite substrate both in mono- and in multi-layer systems, using the metal organic chemical vapor deposition technique, to test their practical qualities as protective coatings against oxidation at high temperatures. The depositions were performed using a hot wall reactor at reduced pressure (0.6 Torr) in the temperature range 350–500 °C, using, as precursors, (η 5 -C 5 H 5 ) 2 Zr(CH 2 C(CH 3 ) 3 ) 2 , Ti(OCH(CH 3 ) 2 ) 4 , and (CH 3 CH 2 ) 2 Al(OCCH 3 CHCCH 3 O), respectively. Surface and topographical analysis of the deposits using X-ray photoelectron spectroscopy, X-ray diffraction and scanning electron microscopy techniques as well as thermogravimetric measurements (TG and DTA) in an oxygen flux of mono- and multi-layer systems are reported and examined.

InMe3 reacts with CNR (RC6H4-p-OMe, C6H4-p-Me) affording the corresponding adducts Me3InCNR, which are formed even in the presence of an excess of CNR. Me3InCNR reacts with pyrrolidine to give the [Me2InC(NR)(Pyrr)] products [Pyrr=conjugated base of pyrrolidine], which form through the insertion of CNR into the InNPyrr bond. These insertion products decompose easily to give the corresponding formamidines.

Nanophasic tungsten oxides thin films have been deposited at 500 °C on quartz and glass substrates starting from W(CO)6 using the metal organic chemical vapor deposition technique (MOCVD). Two series of deposition experiments were carried out to make a comparison between the results obtained employing, as reactant gases, O2 mixed with water vapor and a dry mixture of N2 with 25% H2, respectively. The obtained tungsten oxides were analyzed by x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) in order to investigate their microstructure, chemical composition, and surface morphology. In this work, XPS analyses of two tungsten oxides thin films deposited in different atmospheres are presented. Besides the wide scan spectra, charge corrected binding energies for the W 4f7/2, W 4f5/2, O ls, and C 1s surface photoelectron signals are reported. In particular, the film obtained in H2 atmosphere shows the presence of W in an oxidation state lower than VI.

The first three representatives of a new family of volatile organohafnium compounds suitable as metallo-organic chemical vapour deposition precursors were synthetized. A combination of cyclopentadienyl- and alkoxo-ligands with a bicyclo[2.2.1]heptane framework was used. Volatility at relatively low temperatures for hafnium compounds was found and the precursors were characterized by elemental analysis and spectroscopic methods (IR, 1 H and 13 C NMR, mass spectrometry and mass-analysed ion kinetic energy spectroscopy). The outlook for use in hafnium functional materials synthesis was derived from the fragmentation data

The electron ionization mass spectrometric behaviour of a new class of hafnocene dialcoholates, and, for comparison, of hafnocene dichloride, is discussed. They are also compared on the basis of mass-analysed ion kinetic energy spectrometry. Fragmentation patterns of oxygen-containing species give relevant information on their potential as precursors for the deposition of HfO2 thin films via metal-organic chemical vapour deposition.

The thermal behaviour of dialkylindium-dialkylamides R2InNR/2 (R,R'=Me, Et) and dialkylindium-azolides R2lnNR' (NR'=Pyrrole, Pyrazole) has been examined by a mass spectrometric thermal evolution technique, in the temperature range 30–400°C. Data on volatility, identity of gasified molecules, threshold temperature and products of the decomposition processes are reported and discussed.

The title compound, di-μ-diethyl­amido-N:N-bis­[chloro­di­methyl­tin(IV)], consists of discrete [Sn2Cl2(CH3)4(C4H10N)2] dimer mol­ecules, with Sn atoms linked by bridging diethyl­amido groups. The coordination geometry about the metal atom is distorted trigonal bipyramidal, with the two methyl C atoms and one N atom in the equatorial plane, and the Cl and second N atom in axial positions.

Cobalt phosphide thin films were grown by metal-organic chemical vapor deposition (MOCVD) in H 2 atmospheres on InP(001) substrates using bis(η-methylcyclopentadienyl)Co(II)[Co(Cp Me ) 2 ] and phophine (PH 3 ) precursors at 550°C. Film microstructure, composition, and morphology were investigated in detail by X-ray diffraction, X-ray photoelectron spectroscopy (XPS), Rutherford backscattering (RBS), and atomic force microscopy. Films were crystalline and consisted mainly of the orthorhombic CoP phase and some amount of the CoP 2 phase. XPS measurements indicate an oxidation state (III) for Co, while the P/Co ratio was found by RBS to lie in the range 1-2. The coatings were highly textured with (202), (103) CoP, and (-311) CoP 2 crystal planes parallel to the substrate surface. The root mean square surface roughness was below 10 A for thicknesses smaller than 20 nm and increased to a maxiumum of 70 A for a 35 nm thick film. Cobalt and In intermixing was investigated by XPS depth profiles.

Some new Cp 2 MX 2 (M = U IV ; Th IV ) compounds, stable towards ligand redistribution, have been synthesized by using very bulky X-ligands such as N , N ′-di- p -tolyltriazenide (triaz) and N , N ′-di- p -tolylformamidide (form). Whereas Cp 2 Th(NEt 2 ) 2 undergoes protolysis by Htriaz in refluxing toluene to give Cp 2 Th(triaz) 2 , under the same conditions there is no protolysis by Hform. A suggested coordination mode of the ligands around the central ions of the Cp 2 UX 2 (X = triaz; form) and Cp 2 Th(triaz) 2 is based on the 1 H NMR and mass spectrometric data.

Transition metal amides are known to show a very useful reactivity of the metal-nitrogen bonds towards molecules containing acidic hydrogens and dipolar double bonds[1]. This behaviour has been videly used in order to provide a quite easy synthetic approach to many transition metal complexes[2]. The usefulness of bis-cyclopentadienyl-uranium- bis-amides as reactive intermediates, has been firstly tested by Takats et al. [3] towards the carboxylic and thiocarboxylic acids [4] and some inserting molecules like CS2, COS and CO2 [5]. With the aim to extend the use of Actinide amides as reagents in the synthesis of new organometallic actinide derivatives, recently we reported the routes to CpnM)NEt24-n(M = U(IV);Th(IV);n ⩽ 4) [6]. In this paper we report the results concerning the reactivity of uranium mono-, bis-, and tris-cyclopentadienyl amides towards molecules containing acidic hydrogens, and the CO insertion reaction; the Schemes 1 and 2 summarize these results. One of the most interesting aspects resulting from the Scheme 1 is the possibility of obtaining stable Cp2UX2 products, without any redistribution of ligands, by using very bulky and/or polydentate X-ligands. This behaviour confirms that the steric hindrance is the limiting factor to the ligands redistribution and that a good stability of the Cp2UX2 systems can be obtained either by using polysubstituted cyclopentadienyls or bulky X-ligands. In the Table 1 the 1H NMR spectra of the new Cp2UX2 compounds are reported. The CO insertion into the UN bond represents the first example of such an insertion in systems like Cp3U-X [12, 13], to date considered coordinatively saturated. This insertion reaction together with the reactivity of Cp3UNEt2 and Cp3UPPh2 towards MeCN are t001 . 1H NMR Spectra of the New Cp2MX2 Compounds: M =U(IV), Th(IV) (Benzene-d6; ppm from Benzene-d6as Internal Standard). Compounds ppm (T = 27 °C) Cp2U(Ox)2 +19.19(d,2H,C7H,J6,7 = 7.7Hz);+5.20(t,2H,C6H, J5,6 = 8.0;J6,7 = 7.7 Hz);+1.73(d,2H,C4H;J3,4 = 7.5 Hz);+0.16(d,2H,C5H,J5,6 = 8.0Hz);−8.9(dd,2H,C3H,J2,3 = 4.6;J3,4 = 7.5 Hz); −10.72(d, 2H, C2H, J2,3 = 4.6Hz)−23.01(s,10H,Cp). Cp2U(Form)2 +11.59(bs,4H,meta-phenyls);+4.73(bs,4H,meta'-phenyls); -2.08(bs,6H,CH′3);-3.86(s,10H,Cp);-10.65(bs,10H ortho′-phenyls + CH3);-23.86(s,2H,CH);-34.86(bs,4H, ortho-phenyls). Cp2(Triaz)2 +10.70(d,4H,meta-phenyl, J = 7.9);+4.04(d,4H,Meta′-phenyls J = 7.8);-2.91(s,6H,CH′3);-3.33(s,10H,Cp); -10.39(s,6H,CH3);-10.90(d,4H,ortho′-phenyll, J = 6.6); -38.92(d,4H,ortho-phenyl, J = 6.4 Hz). Cp2U(OR)2 +8.47(m,4H,CH2CH)+6.41(sept.,2HCH(CH3)2); +5.74(s,6H,OCCH3);+4.62(m,2H,CH2CHCH2; +0.85 (d,2H,transCH2);-0.52(d,2H,cisCH2,J = 10 Hz); - 2.03(d,12H,CH(CH3),J = 6.6 Hz); -31.78(s,10H, cp) Cp2Th(NEt2)2 -1.02(s,10H,Cp);-4.00(q,4H,α-CH2);-6.17(t,6H,β-CH3, J = 6.8 Hz) Cp2Th(Triaz)2 +0.08(q, 16H,AA′BB′,phen.);-0.84(s,10H,Cp);-4.99(s, 12H, CH3 The negative sign is indicative of upfield shift, and the positive one downfield shift from benzene -d6. further a confirmation that under particular conditions the Cp3UX compounds bahave as coordinatively unsaturated systems [14]. The CpU(NEt2)3, firstly isolated and characterized by us [6], shows an unexpected behaviour towards weakly acidic molecules like HPPh2. In fact by reacting CpU(NEt2)3 at room temperature with one equivalent of HPPh2, Cp2U(NEt2)2 as the major products is obtained together with a mixture of hardly separable products. Such a behaviour can be interpreted by making two hypotheses: a)CpU(NEt2)3 does not react with HPPh2and completely rearranges to Cp2U(NEt2)2and U(NEt2)4 during the reaction time. b)CpU(NEt2)3 reacts with HPPh2 giving rise to an unstable intermediate (A) containing both -NEt2 and -PPh2 groups, which rearranges immediately to Cp2U(NEt2)2. By considering the hypothesis (a) the reaction mixture should contain Cp2U(NEt2)2 and U(NEt2)4 in the presence of HPPh2. As we reported, Cp2U(NEt2)2 reacts with HPPh2, to produce Cp3UPPh2 and in addition we observed that U(NEt2)4 and HPPh2 (in molar ratio 1:1) quantitatively afford U(NEt2)3(PPh2) [9]; the lack of the Cp3UPPh2 and U(NEt2)3(PPh2) in the reaction mixture suggests that the hypothesis (a) has to be excluded while the (b) one seems to be acceptable. On the other hand, the reaction, of U(NEt2)3(PPh2) and cyclopentadiene in the molar ratio 1:1 produces the same reaction mixture as previously observed for the reactions between CpU(NEt2)3 and HPPh2, making realistic the hypothesis (b) concerning the rearrangement of an unstable intermediate (A): Analogous studies on reactivity of the corresponding thorium amides are in progress.

Insertion of CNC6H3Me2-2,6 into the U–N bonds of [U(η-C5H5)2(NEt2)2] and [U(η-C5H5)3(NEt2)] has been observed, leading to the formation of iminocarbamoyl derivatives. The structure of one of the resulting complexes [U(η-C5H5)3{C(NEt2)NC6H3Me2-2,6}] has been determined by X-ray analysis; this shows that the [C(NEt2)NC6H3Me2-2,6]– anion is η2-co-ordinated and the CN double bond lies perpendicular to the U–M axis (where M is the midpoint of the CN bond). 1H N.m.r. shows that the C5H5 protons are magnetically inequivalent. Some evidence of the insertion of CNC6H3Me2-2,6 into the U–P bond of [U(η-C5H5)3(PPh2)] is also reported.

The synthesis of some new chloride and tropolonato mixed complexes of the general composition MCl 4−n Trop n ·mL (M = U IV , Th IV ; n = 1, 2, 3; m = 1 2 , 2 3 , 1, 2 and 3; L = DME, THF, LiCl and 18-crown-6) by the reaction of uranium and thorium tetrachlorides with M′Trop (M′ = Tl and Li) is described. The residual chloride atoms in UTropCl 3 ·THF undergo further substitution reactions involving TlCp, while UTrop 2 Cl 2 ·THF shows a different behaviour toward TlCp, since Cp 3 UCl as one of the main reaction products is obtained. Protolysis of Cp 2 U(NEt 2 ) 2 by HTrop affords a mixture of CpUTrop 3 and Cp 2 UTrop 2 . Finally both UTropCl 3 ·THF and UCl 4 react directly with HTrop, the nature of the resulting products depending on the reaction solvent.

A study of gas phase photoelectron spectra of a series of U(η5-C5H5)2X2 (X = BH4, NEt2 O2CC(CH3)3, S2CNEt2) complexes has revealed changes in the sequence of upper filled molecular orbitals along the series. In all cases the first ionization event corresponds to removal of uranium 5ƒ electrons. In the case of X = NEt2, the next highest occupied ligand-based MO is an almost pure N2p lone pair, but in the other complexes this MO is π-ring in nature. The observations are consistent with the higher reactivity of the amido complexes toward molecules containing polar double bonds or acidic hydrogens and with the greater labilities of the UCp bonds in the other complexes.

Some new chloride and oxinate mixed complexes of general composition MCl4−nOxn (M = U(IV) and Th(IV); Ox = 8-hydroxyquinolinato; n = 1, 2) were synthesized by the reaction of uranium or thorium tetrachlorides with M′Ox (M′ = Na, K, Tl) or MgOx2. By using the oxine the formation of the adducts MCl4·2HOx occurs, without the substitution of the chloride ions. By suspending MCl4·2HOx in the presence of a strong base (Proton Sponge) MCl2Ox2 was formed immediately. The reaction of UCl2Ox2 and TlCp did not afford Cp2UOx2, which can be easily prepared by reaction of Cp2U(NEt2)2 and HOx.

In contrast to some earlier indications, various organo-uranium(IV) complexes of the general type Cp 3 UX (Cp = η 5 -C 5 H 5 ; X = CH 3 , C 2 H 5 , i-C 3 H 7 , n-C 4 H 9 , t-C 4 H 9 , N(C 2 H 5 ) 2 , and even P(C 6 H 5 ) 2 and NCBH 3 , but not BH 4 or NCS) react in solution with CO under mild conditions, (viz. room temperature and atmospheric pressure of CO). The (IR, 1 H NMR and NIR/VIS) spectroscopic properties of the (1:1) insertion products in case of X = alkyl or dialkylamide are in full accord with their formulation as dihapto-acyl and dihapto-carbamoyl complexes, respectively. While the carbenoid η 2 -OCX ligands are reluctant to undergo consecutive reactions typical of other oxy-carbene systems, reversible equilibria between monomers and dimers in solution (for R = CH 3 and C 2 H 5 ) cannot be ruled out. On the other hand, the dihapto-acyl complexes show a clean reversibility of the CO-uptake at temperatures above 60°C.

The He(I) photoelectron spectra of the antinocene species Th(cot) 2 and U(cot) 2 (cot = cyclooctatetraene) have been determined. The 5 f metal ionization has been detected at the onset of the uranocene spectrum. The low ionization energy region of both spectra is discussed in terms of simple qualitative molecular orbital scheme.

The photoelectron spectra of some cyclopentadienyI derivatives of uranium(IV) and thorium(IV), namely (C 5 H 5 ) 3 ThCl, (C 5 H 5 ) 3 UCl, (C 5 H 4 CH 3 ) 3 ThCl, (C 5 H 4 CH 3 ) 3 UCl, (C 5 H 4 CH 3 ) 3 UBr and (C 5 H 4 CH 3 ) 3 UBH 4 , are reported the metal 5 f ionization has been detected in all the uranium derivative spectra and a simple molecular orbital scheme qualitatively accounts for the number and position of the observed low energy bands.

The use of LiAlH 4 saturated solutions in tetrahydrofuran and dimethoxyethane media as reducing agent is reported. The obtained products are easily isolable from the reaction mixture and correspond to the composition LiU 2 Cl 7 ·9/2S and UCl 3 ·3/2S′ respectively (S = tetrahydrofuran and S′ = dimethoxyethane).