Nonfluorinated Volatile Copper(I) 1,3-Diketiminates as Precursors for Cu Metal Deposition via Atomic Layer Deposition

Ligand Degradation Study of Unsymmetrical β-Diketiminato Copper Dioxygen Adducts: The Length Chelating Arm Effect

An investigation on the reactivity of O₂ binding to unsymmetrical β-diketiminato copper(I) complexes by spectroscopic and titration analysis was performed. The length of chelating pyridyl arms (pyridylmethyl arm vs pyridylethyl arm) leads to the formation of mono- or di-nuclear copper-dioxygen species at -80 °C. The pyridylmethyl arm adduct (L₁CuO₂) forms mononuclear copper-oxygen species and shows ligand degradation, resulting in the formation of (2E,3Z)-N-(2,6-diisopropylphenyl)-4-(((E)-pyridin-2-ylmethylene)amino)pent-3-en-2-imine, which slowly converts to its cyclization isomer 1-(2,6-diisopropylphenyl)-4,6-dimethyl-2-(pyridin-2-yl)-1,2-dihydropyrimidine after addition of NH₄OH at room temperature. On the other hand, the pyridylethyl arm adduct [(L₂Cu)₂(μ-O)₂] forms dinuclear species at -80 °C and does not show any ligand degradation product. Instead, free ligand formation was observed after the addition of NH₄OH. These experimental observations and product analysis results indicate that the chelating length of pyridyl arms governs the Cu/O₂ binding ratio and the ligand degradation behavior.

Role of Anionic Backbone in NHC-Stabilized Coinage Metal Complexes: New Precursors for Atomic Layer Deposition

Cu and Ag precursors that are volatile, reactive, and thermally stable are currently of high interest for their application in atomic-layer deposition (ALD) of thin metal films. In pursuit of new precursors for coinage metals, namely Cu and Ag, a series of new N-heterocyclic carbene (NHC)-based CuI and AgI complexes were synthesized. Modifications in the substitution pattern of diketonate-based anionic backbones led to five monomeric Cu complexes and four closely related Ag complexes with the general formula [M(tBu NHC)(R)] (M=Cu, Ag; tBu NHC=1,3-di-tert-butyl-imidazolin-2-ylidene; R=diketonate). Thermal analysis indicated that most of the Cu complexes are thermally stable and volatile compared to the more fragile Ag analogs. One of the promising Cu precursors was evaluated for the ALD of nanoparticulate Cu metal deposits by using hydroquinone as the reducing agent at appreciably low deposition temperatures (145-160 °C). This study highlights the considerable impact of the employed ligand sphere on the structural and thermal properties of metal complexes that are relevant for vapor-phase processing of thin films.

Crystal structure and enantiomeric layer disorder of a copper(I) nitrate π-coordination compound

The novel π-coordination compound [CuI(m-dmphast)NO3], where m-dmphast = 5-(allylthio)-1-(3,5-dimethylphenyl)-1H-tetrazole, is characterized using single-crystal X-ray diffraction and crystallizes in a noncentrosymmetric space group. Additionally, for the first time in this group of materials, the streaks of X-ray diffuse scattering in the reciprocal space sections were observed and described. This gave the possibility for a deeper insight into the local structure of the title compound. The conjecture about the origin of diffuse scattering was derived from average structure solution. It was then confirmed using the local structure modelling. The extended [Cu(m-dmphast)NO3]∞ chains, connected by weak interactions, produce layers which can exist in two enantiomeric forms, one of which predominates.

Reactivity of 1,3-dichloro-1,3-bis(dimethylamino)-propenium salts with primary amines

1,3-Dichloro-1,3-bis(dimethylamino)propenium salts react with primary amines to give different products depending on properties of the amine used, including the size of the R groups, whether it is aromatic, and if there is a hydrogen on the α-carbon.

Low-Symmetry β-Diketimine Aryloxide Rare-Earth Complexes: Flexible, Reactive, and Selective

We report the synthesis, characterization, and reactivity of a new low-symmetry β-diketimine featuring a pendant amino(methyl)phenol donor and its corresponding heteroleptic rare-earth (RE) complexes. This includes the first structurally characterized examples of alcoholysis and insertion from an isolated RE^III amide in a β-diketimine framework. The flexible methylene linkage leads to RE^III complexes with tunable dynamic solution behavior that defines their stoichiometric and catalytic reactivity. The addition of a strong neutral donor ligand, tricyclohexylphosphine oxide, suppresses a prevalent catalyst degradation pathway (base-promoted elimination) and dramatically enhances the catalyst performance in the stereospecific ring-opening polymerization of rac-β-butyrolactone. Our results further demonstrate the importance of ligand reorganization in the stoichiometric and catalytic activity of RE^III ions.

Controlled growth of Cu and CuOx thin films from subvalent copper precursors

Volatile mixed-ligand complexes of copper based on stabilizing cyclooctadiene and reactive enaminone are reported as efficient precursors for chemical vapor deposition of Cu(0), Cu₂O, or CuO thin films.

β-Ketoiminato-based copper(ii) complexes as CVD precursors for copper and copper oxide layer formation

The synthesis of ketoiminato copper(ii) complexes [Cu(OCRCHC(CH3)NCH2CH2X)(μ-OAc)]2 (X = NMe2: 4a, R = Me; 4b, R = Ph. X = OMe: 5, R = Me) and [Cu(OCRCHCMeNCH2CH2NEt2)(OAc)] (6, R = Me) from RC(O)CHC(CH3)N(H)CH2CH2X (X = NMe2: 1a, R = Me; 1b, R = Ph. X = NEt2: 1c, R = Me. X = OMe: 2, R = Me) and [Cu(OAc)2·H2O] (3) is reported. The molecular solid-state structures of 4-6 were determined by single crystal X-ray diffraction studies, showing that 4a,b and 5 are dimers which are set up by two [{Cu(μ-OAc)L}] (L = ketoiminato ligand) units featuring a square-planar Cu2O2 core with a distorted square-pyramidal geometry at Cu(ii). In contrast, 6 is monomeric with a tridentate-coordinated OCMeCHCMeNCH2CH2NEt2 ligand and a σ-bonded acetate group, thus inducing a square-planar environment around Cu(ii). The thermal behavior of all complexes was studied by TG (Thermogravimetry) and DSC (Differential Scanning Calorimetry) under an atmosphere of Ar and O2. Complex 4b shows the highest first onset temperature at 213 °C (under O2) and 239 °C (Ar). PXRD studies confirmed the formation of CuO under an atmosphere of O2 and Cu/Cu2O under Ar. TG-MS studies, exemplarily carried out with 4a, indicate the elimination of the ketoiminato ligands with detectable fragments such as m/z = 15, 28, 43, 44, 45, and 60 at a temperature above 250 °C. Vapor pressure measurements displayed that 5 shows the highest volatility of 3.6 mbar at 70 °C (for comparison, 4a, 1.4; 4b, 1.3; 6, 0.4 mbar) and hence 4a and 5 were used as MOCVD precursors for Cu/Cu2O deposition on Si/SiO2 at substrate temperatures of 450 °C and 510 °C. The deposition experiments were carried out under an atmosphere of nitrogen as well as oxygen. The as-obtained layers were characterized by SEM, EDX, XPS, and PXRD, showing that with oxygen as the reactive gas a mixture of metallic copper and copper(i) oxide without carbon impurities was formed, while under N2 Cu films with 53-68 mol% C contamination were produced. In a deposition experiment using precursor 5 at 510 °C under N2 a pure copper film was obtained.

Synthesis, Characterization, and Thermal Properties of N-alkyl β-Diketiminate Manganese Complexes

A series of N, N'-dialkyl-β-diketiminato manganese(II) complexes was synthesized and characterized by single crystal X-ray diffraction, UV-vis and FTIR spectroscopy, and then assayed for volatility, thermal stability, and surface reactivity relevant to vapor-phase film growth processes. Bis( N, N'-dimethyl-4-amino-3-penten-2-imine) manganese(II), 1, and bis( N- N'-diisopropyl-4-amino-3-penten-2-imine) manganese(II), 2, specifically, emerge as the most promising candidates, balancing volatility (sublimation temperatures < 100 °C at 100 mTorr) with coordinative unsaturation and reactivity, as revealed by rapid release of ligand in the presence of a silica surface. Good correlation is observed between buried volume calculations and relative surface reactivity data, indicating that metal availability resulting from sterically open ligand alkyl substituents increases surface reactivity. The thermal stability, volatility, and reactivity exhibited by these compounds render them promising precursors for the growth of manganese oxide films via vapor-phase growth processes.

Reactivity Study of Unsymmetrical β-Diketiminato Copper(I) Complexes: Effect of the Chelating Ring

β-Diketiminato copper(I) complexes play important roles in bioinspired catalytic chemistry and in applications to the materials industry. However, it has been observed that these complexes are very susceptible to disproportionation. Coordinating solvents or Lewis bases are typically used to prevent disproportionation and to block the coordination sites of the copper(I) center from further decomposition. Here, we incorporate this coordination protection directly into the molecule in order to increase the stability and reactivity of these complexes and to discover new copper(I) binding motifs. Here we describe the synthesis, structural characterization, and reactivity of a series of unsymmetrical N-aryl-N'-alkylpyridyl β-diketiminato copper(I) complexes and discuss the structures and reactivity of these complexes with respect to the length of the pyridyl arm. All of the aforementioned unsymmetrical ß-diketiminato copper(I) complexes bind CO reversibly and are stable to disproportionation. The binding ability of CO and the rate of pyridyl ligand decoordination of these copper(I) complexes are directly related to the competition between the degree of puckering of the chelate system and the steric demands of the N-aryl substituent.

σ-Complexation as a strategy for designing copper-based light emitters

Introduction of weak σ-SiH coordination to a copper(i) center leads to a highly emissive copper complex to minimize geometry relaxation in MLCT excited states.

Copper(I) π-complexes with allyl derivatives of heterocyclic compounds: structural survey of their crystal engineering

In this review an exhaustive crystallochemical analysis of copper(I) π-complexes with allyl derivatives of heterocyclic compounds has been performed. Structural genesis of inorganic constituents starting from the simplest units to the most complicated aggregates was considered taking into account the specific role of Cu-(C=C) interaction, the construction of the organic ligands, the basicity and nucleophilic activity of their heteroatoms, as well as olefin Cu(I) π-complex preparation route.

CVD of pure copper films from novel iso-ureate complexes

We report the synthesis and characterisation of a new family of copper(i) metal precursors based around alkoxy-N,N'-di-alkyl-ureate ligands, and their subsequent application in the production of pure copper thin films. The molecular structure of the complexes bis-copper(i)(methoxy-N,N'-di-isopropylureate) (1) and bis-copper(i)(methoxy-N,N'-di-cyclohexylureate)(5) are described, as determined by single crystal X-ray diffraction analysis. Thermogravimetric analysis of the complexes highlighted complex 1 as a possible copper CVD precursor. Low pressure chemical vapour deposition (LP-CVD) was employed using precursor 1, to synthesise thin films of metallic copper on ruthenium substrates under an atmosphere of hydrogen (H2). Analysis of the thin films deposited at substrate temperatures of 225 °C, 250 °C and 300 °C, respectively, by SEM and AFM reveal the films to be continuous and pin hole free, and show the presence of temperature dependent growth features on the surface of the thin films. Energy dispersive X-ray spectroscopy (EDX), powder X-ray diffraction (PXRD) and X-ray photoelectron spectroscopy (XPS) all show the films to be high purity metallic copper.

A N-aryloxy-β-diketiminate ligand in 4d, 4f and 5f-metals complexes

A new class of functionalized β-diketiminate ligands has been prepared from commercially available reagents. The novel N-aryloxy-β-diketiminate ligand proves to be an excellent ligand to support 4d, 4f and 5f metal ions.

One-pot synthesis of β-diketimine ligands

Symmetric N,N′-dialkyl-2-amino-4-imino-pent-2-enes (nacnacRH) can be prepared in high yields in a simple one-pot reaction from acetylacetone and 2 equiv. of amine. Optimized conditions require the azeotropic removal of water, use of a minimum amount of solvent, and of 1 equiv. of acid. Either para-toluenesulfonic acid, hydrochloric acid, or a mixture of both can be employed, with the latter being most advantageous. Symmetric nacnacRH are thus obtained in higher than 95% purity and with 65% yield for R = Me and 80%–95% yields for R = n-Pr, i-Pr, i-Bu, Bn, Cy, and (+)-CH(Me)Ph.

Synthesis and structures of isopropyl-β-diketiminato copper(I) complexes

The reaction of N,N′-diisopropyl-2-amino-4-iminopent-2-ene (nacnaci-PrH, 1) either with CuOt-Bu or with a mixture of mesityl copper and 10% CuOt-Bu afforded, in the presence of PPh3, CN(C6Me2H3), or MeCN, the Lewis base coordinated complexes nacnaci-PrCuPPh3·0.5 C6H14 (2), nacnaci-PrCuCN(C6Me2H3) (3), and nacnaci-PrCu(NCMe) (4). Compounds 2, 3, and 4 were characterized by single-crystal X-ray diffraction studies. Compound 4 afforded two species in deuterated benzene in a 2:1 ratio, which were assigned to {nacnaci-PrCu}2(μ-NCMe) and nacnaci-PrCuNCMe (4). Upon addition of 5 equiv. of MeCN, the two sets collapsed into that of 4. No copper complexes were formed in the presence of styrene, stilbene, or diphenylacetylene.

Macrocyclic Binucleating β-Diketiminate Ligands and their Lithium, Aluminum, and Zinc Complexes

The incorporation of rigid aromatic linkers into β-diketiminate ligands creates a binucleating scaffold that holds two metals near each other. This paper discloses the synthesis, characterization, and reactivity of mBin(2-), which has a meta-substituted xylylene spacer, and pBin(2-), which has a para-substituted xylylene spacer. Lithium, aluminum, and zinc complexes of each ligand are isolated, and in some cases are characterized by X-ray crystallography. The lithium complexes are coordinated to solvent-derived THF ligands, while the zinc and aluminum complexes have alkyl ligands. Complexes of the mBin(2-) ligand have an anti conformation in which the metals are on opposite sides of the macrocycle, while pBin(2-) complexes prefer a syn conformation. The (1)H NMR spectra of the complexes demonstrate that the conformations rapidly interconvert in the lithium complexes, and less rapidly in the zinc and aluminum complexes.