Titanium Amides Research Articles

The Synthesis, Structure and Reactivity of B(C6F5)3‐Stabilised Amide (MNH2) Complexes of the Group 4 Metals

Treatment of the homoleptic titanium amides [Ti(NR(2))(4)] (R=Me or Et) with the Brønsted acidic reagent H(3)NB(C(6)F(5))(3) results in the elimination of one molecule of amine and the formation of the four-coordinate amidoborate complexes [Ti(NR(2))(3){NH(2)B(C(6)F(5))(3)}], the identity of which was confirmed by X-ray crystallography. The reaction with [Zr(NMe(2))(4)] proceeds similarly but with retention of the amine ligand to give the trigonal-bipyramidal complex [Zr(NMe(2))(3){NH(2)B(C(6)F(5))(3)}(NMe(2)H)]. Cyclopentadienyl (Cp) amidoborate complexes, [MCp(NR(2))(2){NH(2)B(C(6)F(5))(3)}] (M=Ti, R=Me or Et; M=Zr, R=Me) can be prepared from [MCp(NR(2))(3)] and H(3)NB(C(6)F(5))(3), and exhibit greater thermal stability than the cyclopentadienyl-free compounds. H(3)NB(C(6)F(5))(3) reacts with nBuLi or LiN(SiMe(3))(2) to give LiNH(2)B(C(6)F(5))(3), which complexes with strong Lewis acids to form ion pairs that contain weakly coordinating anions. The attempted synthesis of metallocene amidoborate complexes from dialkyl or diamide precursors and H(3)NB(C(6)F(5))(3) was unsuccessful. However, LiNH(2)B(C(6)F(5))(3) does react with the highly electrophilic reagents [MCp(2)Me(mu-Me)B(C(6)F(5))(3)] to give [MCp(2)Me(mu-NH(2))B(C(6)F(5))(3)] (M=Zr or Hf). Comparison of the molecular structures of the Group 4 amidoborate complexes reveals very similar B--N, Ti--N and Zr--N bond lengths, which are consistent with a description of the bonding as a dative interaction between an {M(L)(n)(NH(2))} fragment and the Lewis acid B(C(6)F(5))(3). Each of the structures has an intramolecular hydrogen-bonding arrangement in which one of the nitrogen-bonded hydrogen atoms participates in a bifurcated FHF interaction to ortho-F atoms.

A Molecular Route to Dip-coated Transition Metal Nitride Thin Films.

ABSTRACTThere is an increasing interest in sol-gel synthesis of nitrides. The ability to deposit films of these materials by dip- or spin-coating will increase the range of applications in which they are viable and is an important step toward general sol-gel processing of nitride materials.With transition metals, the ammono based analogue of the well established alkoxy route to gels is inherently difficult to control. Due to the basicity of the system, the overwhelming tendency is of the starting materials to favour particle growth which results in a precipitate rather than a stable emulsion, unless both environment and synthetic pathway are carefully controlled. Hence reports to date of sol-gel routes to nitrides describe production of powders. We report work on a sol-gel route to titanium nitride with the ammonolysis of titanium amides controlled by temperature and chemical moderators, resulting in stable emulsions useful for dip-coating.

Synthesis and structure of a linked-bis(amidate) ligand and some complexes with titanium.

The synthesis of a new ligand system in which two amides are coupled via a rigid phenylene spacer is readily accomplished in a high-yield, single-step reaction. The dilithio salt (NO)2Li2(THF)x reacts with Ti(NR2)4 (R = Me, Et) to yield the titanium amides [(NO)2Ti(NR2)2]2. The latter react with excess Me3SiCl to produce the dichloride (NO)2TiCl2, which was also obtained by the reaction of [(NO)2Ti(NMe2)2]2 with TiCl4(THF)2 in refluxing toluene, and in a lower-yielding route, by salt metathesis between the dilithio salt and TiCl4(THF)2.

Synthesis of supported titanocene amide complex and its use as a catalyst in ethylene polymerization

Heterogeneous ethylene polymerization catalysts were prepared by supporting tetrakis(dimethylamino)titanium, Ti[N(CH3)2]4, on chemically modified silica surface. The modification of silica was made using a silane coupling agent, Cp(CH2)3Si(OCH2CH3)3 and atomic layer chemical vapor deposition (ALCVD). Titanium amide was also immobilized straight on the silica and on a methyllithium-treated modified silica. The aim of methyllithium treatment was to alkylate the unreacted ethoxy groups of the silane coupling agent on the silica. Methyllithium methylates, besides ethoxy groups, also silica surface and surface cyclopentadienyl groups. A model compound for these heterogeneous catalysts was prepared using a reaction of Ti[N(CH3)2]4 with trimethylsilylcyclopentadienyl yielding a monocyclopentadienyl titanium compound, Me3SiCpTi[N(CH3)2]3. The preliminary results of ethylene polymerization using the prepared heterogeneous and homogeneous titanocene amide complexes and the effect of amount of MAO are presented.

Synthese und Kristallstruktur von [(Cl3Si)2N]2TiCl2 -ein perchloriertes N-Silyl-titanamid /Synthesis and Crystal Structure of [(Cl3Si)2N]2TiCl2 -a Fully Chlorinated N-Silyl Titanium Amide

Abstract The chlorinated titanium amides [(Cl3Si)2N]2TiCl2 (1) and (Cl3Si)2NTiCl3 have been syn­thesized selectively from hexachlorodisilazane lithium and TiCl4. The crystal structure of 1 was determined by single crystal X-ray methods at room temperature (P212121, a = 1232.4(2), b = 1265.5(2), c -1469.1(2) pm, Z = 4). The central titanium atom of 1 is bound to two nitrogen atoms and two Cl atoms and is weakly coordinated further by two Cl atoms of the trichlorosilyl groups.

Spectroscopic studies of side-on and end-on bonding of dinitrogen in low-valent binuclear titanium amide complexes

Spectroscopic studies of side-on and end-on bonding of dinitrogen in low-valent binuclear titanium amide complexes

Molecular structures of titanium(IV) and vanadium(IV) amides and alkoxides

Gas-phase electron diffraction data for Ti(NMe2)4, V(NMe2)4 and V(OBut)4 obtained with nozzle temperatures of 130–156 °C are consistent with molecular models of S4 symmetry. The metal to ligand bond distances (ra) are Ti–N 191.7(3), V–N 187.9(4) and V–O 177.9(6) pm, respectively. A set of bonding radii for TiIV, VIV, CrIV and WVI for use with the modified Schomaker–Stevensen rule is proposed. The valence angle bisected by the S4 axis in the titanium amide, N–Ti–N 114.2(17)°, indicates that the co-ordination tetrahedron is slightly flattened. The corresponding angles in the vanadium amide and alkoxide are N–V–N 100.6(5)° and O–V–O 115.1(19)°, indicating that the co-ordination polyhedron in the former is significantly elongated, while in the latter it is significantly flattened. The shapes of the co-ordination tetrahedra in these and related molecules are discussed in terms of donation of π electrons from N or O into low-lying d orbitals on the metal atom.

Plasma-assisted chemical vapour deposition with titanium amides as precursors

One possible way of reducing the high deposition temperatures required for conventional chemical vapour deposition (CVD) is the application of metal-organic compounds; a second is the excitation of the precursors in a glow discharge. In the production of wear-resistant coatings such as TiN in a low temperature plasma-assisted CVD process, the use of TiCl 4 can cause corrosion as well as producing coatings of undesirably low hardness. To avoid these problems, the application of a metal-organic precursor and plasma enhancement of the CVD process were combined in this investigation. Two titanium amides, Ti(N(CH 3) 2) 4 and Ti(N(C 2H 5) 2) 4, both liquids with sufficient volatility, were used together with hydrogen and argon in a d.c. glow discharge at a total pressure of approximately 1 mbar. The temperature of the steel substrates during deposition was varied from 200 to 500 °C. It was established by means of glow discharge optical spectrometry and X-ray diffraction that titanium carbonitride coatings were obtained. The morphology of the Ti(C,N) layers was examined by scanning electron microscopy. Up to a temperature of 400 °C fine-grained polycrystalline layers were observed whose hardness measured more than 2000 HV. At 500 °C thermal decomposition of the metal-organic compounds by a homogeneous reaction became dominant and reduced the quality of the coating.

Tandem conjugate addition-aldol reaction to α,β-unsaturated esters and ketones using titanium amide

Titanium dialkylamide, readily available, adds to a α,β-unsaturated esters and ketones in a conjugate addition mode to give ester and ketone enolates, respectively, which are successively quenched with electrophiles such as aldehydes and acetals. The aldol products can be readily converted to the corresponding deaminated or dehydrated derivatives selectively.

Lewis acidic titanium species: the synthesis, structure, bonding and molecular modelling considerations of the complexes Ti(NR2)3Cl (R = Me, Et)

Reaction of simple amides with TiCl4 affords mixed amido-chloride species Ti(NR2)4−nCln. The trisamide-chloride species Ti(NR2)3Cl can be prepared directly employing three equivalents of amide or by reaction Ti(NR2)4 with TiCl4. The compound Ti(NMe2)3Cl, 1, crystallizes in the trigonal space group [Formula: see text] with a = 11.525(5), c = 14.939(3) Å, Z = 6, and V = 1718(1) Å3. The compound Ti(NEt2)3Cl, 2, crystallizes in the monoclinic space group P21/c, with a = 8.385(2) Å, b = 15.958(2) Å, c = 14.230(4) Å, β = 107.79(1)°, Z = 4, and V = 1813(1) Å3. The geometry of the Ti coordination sphere in these complexes is best described as pseudo-tetrahedral. The structural data are consistent with Ti—N multiple bonding. Preliminary results of EHMO calculations are consistent with dπ—pπ Ti—N bonding. Attempts to replace the halides with phosphides (LiPR2, R = Me, Et, Ph) led not to the Ti(IV) phosphido species, but rather to redox chemistry yielding Ti(III) amides and P2R4. The barrier to rotation about the Ti—N bonds has been considered. Variable temperature 1H NMR studies reveal that the barrier is small. Extended Hückel total energy minimization calculations have been performed. In addition, MMX calculations of the barrier to Ti—N rotation are reported. The results of these calculations imply that the rotational barrier is dominated by steric effects. Key words: titanium amides, structures, Ti—N bonding

Structural characterization of titanium(III) amide complexes; a planar geometry at nitrogen in the absence of Ti–N multiple bonding

The titanium(II) complexes [Ti(η5-C5Me5)2(NMePn)] and [Ti(η5-C5Me5)2(NMePh)(CNBun)] have been characterized by X-ray crystallography.

ChemInform Abstract: The First Partial Synthesis of 14‐Hydroxygibberellin Esters. A Titanium(IV) Amide Catalyzed Rearrangement of Epoxides.

ChemInformVolume 21, Issue 29 Natural Products ChemInform Abstract: The First Partial Synthesis of 14-Hydroxygibberellin Esters. A Titanium(IV) Amide Catalyzed Rearrangement of Epoxides. B. M. FRAGA, B. M. FRAGA Inst. Prod. Nat. Org., CSIC, La Laguna, Tenerife, SpainSearch for more papers by this authorJ. R. HANSON, J. R. HANSON Inst. Prod. Nat. Org., CSIC, La Laguna, Tenerife, SpainSearch for more papers by this authorM. G. HERNANDEZ, M. G. HERNANDEZ Inst. Prod. Nat. Org., CSIC, La Laguna, Tenerife, SpainSearch for more papers by this authorF. G. TELLADO, F. G. TELLADO Inst. Prod. Nat. Org., CSIC, La Laguna, Tenerife, SpainSearch for more papers by this author B. M. FRAGA, B. M. FRAGA Inst. Prod. Nat. Org., CSIC, La Laguna, Tenerife, SpainSearch for more papers by this authorJ. R. HANSON, J. R. HANSON Inst. Prod. Nat. Org., CSIC, La Laguna, Tenerife, SpainSearch for more papers by this authorM. G. HERNANDEZ, M. G. HERNANDEZ Inst. Prod. Nat. Org., CSIC, La Laguna, Tenerife, SpainSearch for more papers by this authorF. G. TELLADO, F. G. TELLADO Inst. Prod. Nat. Org., CSIC, La Laguna, Tenerife, SpainSearch for more papers by this author First published: July 17, 1990 https://doi.org/10.1002/chin.199029279Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume21, Issue29July 17, 1990 RelatedInformation

Group transfer polymerisation of acrylonitrile

The polymerization of acrylonitrile, initiated by titanium amides, is interpreted in terms of a group-transfer mechanism.

ChemInform Abstract: A New Method for the Synthesis of α‐Substituted Phenethylamines (VI) via Titanium Amide Complexes (III) and (VIII).

ChemInformVolume 19, Issue 27 Isocyclic Compounds ChemInform Abstract: A New Method for the Synthesis of α-Substituted Phenethylamines (VI) via Titanium Amide Complexes (III) and (VIII). H. TAKAHASHI, H. TAKAHASHI Inst. Med. Chem., Hoshi Univ., Shinagawa, Tokyo 142, JapanSearch for more papers by this authorT. TSUBUKI, T. TSUBUKI Inst. Med. Chem., Hoshi Univ., Shinagawa, Tokyo 142, JapanSearch for more papers by this authorK. HIGASHIYAMA, K. HIGASHIYAMA Inst. Med. Chem., Hoshi Univ., Shinagawa, Tokyo 142, JapanSearch for more papers by this author H. TAKAHASHI, H. TAKAHASHI Inst. Med. Chem., Hoshi Univ., Shinagawa, Tokyo 142, JapanSearch for more papers by this authorT. TSUBUKI, T. TSUBUKI Inst. Med. Chem., Hoshi Univ., Shinagawa, Tokyo 142, JapanSearch for more papers by this authorK. HIGASHIYAMA, K. HIGASHIYAMA Inst. Med. Chem., Hoshi Univ., Shinagawa, Tokyo 142, JapanSearch for more papers by this author First published: July 5, 1988 https://doi.org/10.1002/chin.198827135AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume19, Issue27July 5, 1988 RelatedInformation

Preparation of titanium nitride and titanium carbonitride by the preceramic polymer route

Abstract : The pyrolysis of selected titanium amides in a stream of ammonia gives titanium nitride. In a stream of argon titanium carbonitride is produced. We have developed useful routes for the preparation of silicon and boron carbonitrides and nitrides by the pyrolysis of suitable polymeric precursors, and we were interested in developing such an approach for the synthesis of titanium carbonitride and nitride. Keywords: Titanium nitride, Titanium carbonitride, Titanium amides, Ceramics.

A New Method for the Synthesis of α-Substituted Phenethylamines via Titanium Amide Complexes

Substituted phenethylamines (1-substituted 2-phenylethylamines) 4 are obtained in high yields by a new, facile reaction of titanium amide complexes with aldehydes and benzylmagnesium chloride.

The reaction of TiCl 4 and CpTiCl 3 with tridentate triaminosilyl ligands. crystal and molecular structure of a titanibicycloheptane with an unusual Si-N-Li-Cl-Ti chain

The reaction of lithiated triaminosilanes RSi(NLiR′) 3 (R = Me, t-Bu, Ph; R′ = t-Bu, SiMe 3) with TiCl 4 and CpTiCl 3 gives, in poor yields, the novel spiro- and monocyclic sila-titana-diazacyclobutane derivatives Ti[(NR′) 2Si(Me)(NHR′)] 2 (R′ = SiMe 3 (VII)), R′NH(Ph)S iNR′TiX 1X 2N R′ (R′ = SiMe 3, X 1 = X 2 = Cl (VIII), R′ =t-Bu, X 1 = X 2 = Cl (X) and R′ = SiMe 3, X 1 = Cl, X 2 = Cp (XIII)). Cleavage of VII with TiCl 4 yields R′NH(Me) SiNr′TiCl 2N R′ (R′ = SiMe 3), while Me 2SiNR′-TiCl 2NR′ (R′ = SiMe 3 (XI) and t-Bu (XII) were obtained with Me 2Si(NHSiMe 3) 2 and Me 2Si(NH-t-Bu) 2. If the synthesis of XIII is performed at −30°C, the moholithiated cyclic titanium amide R′(Li)N(Ph)SiNR′Ti(Cl)(Cp)NR′ (R′ = SiMe 3 (XIV)) is isolated as diethyletherate. It crystallizes in the monoclinic space group P2 1/ n with a 11.033(1), b 17.504(2), c 18.001(2) Å, β 98.21(2)°, Z = 4, D x 1.151 g cm −3 and R = 0.045 for 4277 observed reflections. The structure contains an unusual heteronuclear bicyclo[3.1.1]heptane system with CpTi and PhSi groups at the bridge-heads. The main bridge contains the Ti-bonded Cl atom, a Li·O(C 2H 5) 2 moiety and an NSiMe 3 Fragment whereas NSiMe 3 groups are found in the other two bridges. Important bond distances are LiCl (2.455(7) Å), TiCl (2.364(1) Å) and TiN (1.859(6) Å).

Titan—stickstoff-verbindungen : XXV. Cyclische titan-silylamide

Monocyclic silyl-substituted titanium amides of the general formula Z 2TiL 2 where L 2 is a bidentate ligandNMeSiMe 2YSiMe 2NMe(Y  , NMe, O, CH 2, Z  NMe 2, NEt 2, F, Cl, Br) have been prepared either by the reaction of the dilithiated ligand Li 2L 2 with the appropriate halide Z 2TiHal 2 or by the cleavage of the spiro compound Ti(L 2) with TiZ 4. With the exception of the difluoride L 2TiF 2 all compounds are monomeric and of sufficient thermal stability to be distilled or sublimed in vacuo. The difluoride is associated via TiFTi bridges. All compounds have been characterized by 1H (and 19F) NMR spectra and by IR and Raman spectra. Most of the skeletal stretching vibrations have been assigned.

ChemInform Abstract: LOW TEMPERATURE DEPOSITION OF METAL NITRIDES BY THERMAL DECOMPOSITION OF ORGANOMETALLIC COMPOUNDS

AbstractDialkylamide von Ti, Zr, Nb und Ta zersetzen sich zwischen 300 und 500°C zu Nitriden, während die Dialkylamide von B, Si und Sn bei höheren Temperaturen metallische Abscheidungen liefern.

Low Temperature Deposition of Metal Nitrides by Thermal Decomposition of Organometallic Compounds

Decomposition reaction of dialkylamides of boron, silicon, tin, titanium, zirconium, niobium, and tantalum was investigated. The amides of transition metals decomposed to the corresponding nitrides at 300°–500°C, whereas those of boron, silicon, and tin yielded elemental deposits at higher temperatures. In the deposition of titanium nitride from titanium tetrakis(dimethylamide), two optimum temperatures at 400° and at 800°C in nitrogen or hydrogen atmosphere were found, but in argon only low temperature deposition was possible. The low and high temperature processes are discussed in relation to mass spectral analysis of the exhaust gases formed at various decomposition temperatures of titanium amide.