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Abstract
ConspectusAtomic layer control of semiconductor processing is needed as critical dimensions are progressively reduced below the 10 nm scale. Atomic layer deposition (ALD) methods are meeting this challenge and produce conformal thin film growth on high aspect ratio features. Atomic layer etching (ALE) techniques are also required that can remove material with atomic layer precision. ALE processes are defined using sequential, self-limiting reactions based on surface modification and volatile release. Plasma ALE methods employ energetic ion or neutral species to release the modified material anisotropically using sputtering. In contrast, thermal ALE processes utilize gas species to release the modified material isotropically using thermal reactions. Thermal ALE can be viewed as the "reverse of ALD".There are a number of mechanisms for thermal ALE that have developed over the last five years. This Account will first examine the fluorination and ligand-exchange mechanism for thermal ALE. This mechanism is applicable for many metal oxide and metal nitride materials. Subsequently, the "conversion etch" mechanisms will be explored that are derived from the conversion of the surface of the substrate to a new material. The "conversion etch" mechanisms are needed when the initial material does not have a viable etching pathway via fluorination and ligand-exchange or when the material has a volatile fluoride. The thermal ALE mechanisms founded on either oxidation or halogenation of the initial substrate will then be examined with an emphasis on metal thermal ALE. Lastly, thermal ALE mechanisms will be considered that are based on self-limiting surface ligands or temperature modulation mechanisms. These various mechanisms offer a wide range of pathways to remove material isotropically with atomic layer control.Thermal ALE will be required to fabricate advanced semiconductor devices. This fabrication will increasingly occur beyond the limits of lithography and will extend into the third dimension. The situation is like Manhattan during the advent of skyscrapers. When there was no more room on the ground, building started to move to the third dimension. Three-dimensional devices require a sequential series of deposition and etching steps to build the skyscraper structures. Some etching needs to be vertical and anisotropic to make the elevator shafts. Other etching needs to be horizontal and isotropic to form the hallways. The mechanisms of thermal ALE will be critical for the definition of isotropic ALE processes.Reaching beyond the limits of lithography will also increase the need for maskless processing. The mechanisms of thermal ALE lead to strategies for selective etching of one material in the presence of many materials. In addition, area-selective deposition can benefit from the ability of thermal ALE to enhance deposition on the desired growth surfaces by removing deposition from other surrounding surfaces. Looking ahead, thermal ALE will continue to provide unique capabilities and will grow in importance as a nanofabrication processing technique.
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Affiliation(s)
- Steven M. George
- Department of Chemistry, University of Colorado, Boulder, Colorado 80309-0215, United States
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Igumenov IK, Turgambaeva AE, Krisyuk VV. Volatile zirconium compounds: Prospects for use in gas-phase isotope separation. RUSS J APPL CHEM+ 2017. [DOI: 10.1134/s1070427216120016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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George SM, Lee Y. Prospects for Thermal Atomic Layer Etching Using Sequential, Self-Limiting Fluorination and Ligand-Exchange Reactions. ACS NANO 2016; 10:4889-4894. [PMID: 27216115 DOI: 10.1021/acs.chemmater.6b02543] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Thermal atomic layer etching (ALE) of Al2O3 and HfO2 using sequential, self-limiting fluorination and ligand-exchange reactions was recently demonstrated using HF and tin acetylacetonate (Sn(acac)2) as the reactants. This new thermal pathway for ALE represents the reverse of atomic layer deposition (ALD) and should lead to isotropic etching. Atomic layer deposition and ALE can together define the atomic layer growth and removal steps required for advanced semiconductor fabrication. The thermal ALE of many materials should be possible using fluorination and ligand-exchange reactions. The chemical details of ligand-exchange can lead to selective ALE between various materials. Thermal ALE could produce conformal etching in high-aspect-ratio structures. Thermal ALE could also yield ultrasmooth thin films based on deposit/etch-back methods. Enhancement of ALE rates and possible anisotropic ALE could be achieved using radicals or ions together with thermal ALE.
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Affiliation(s)
- Steven M George
- Department of Chemistry and Biochemistry and ‡Department of Mechanical Engineering, University of Colorado at Boulder , Boulder, Colorado 80309, United States
| | - Younghee Lee
- Department of Chemistry and Biochemistry and ‡Department of Mechanical Engineering, University of Colorado at Boulder , Boulder, Colorado 80309, United States
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Won YS. Computational study on the decomposition of tetraneopentyl zirconium for the chemical vapor deposition of zirconium carbide. KOREAN J CHEM ENG 2012. [DOI: 10.1007/s11814-012-0050-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Taw FL, Clark AE, Mueller AH, Janicke MT, Cantat T, Scott BL, Hay PJ, Hughes RP, Kiplinger JL. Titanium(IV) Trifluoromethyl Complexes: New Perspectives on Bonding from Organometallic Fluorocarbon Chemistry. Organometallics 2012. [DOI: 10.1021/om201055e] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Felicia L. Taw
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Aurora E. Clark
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | | | - Michael T. Janicke
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Thibault Cantat
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Brian L. Scott
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - P. Jeffrey Hay
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Russell P. Hughes
- Dartmouth College, 6128 Burke Laboratories, Hanover, New Hampshire 03755, United States
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Xue ZL, Morton LA. Transition metal alkylidene complexes. Pathways in their formation and tautomerization between bis-alkylidenes and alkyl alkylidynes. J Organomet Chem 2011. [DOI: 10.1016/j.jorganchem.2011.06.048] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Denomme DR, Dumbris SM, Hyatt IFD, Abboud KA, Ghiviriga I, McElwee-White L. Synthesis and Electronic Structure of Tetrakis(η3-phenylpropargyl)zirconium. Organometallics 2010. [DOI: 10.1021/om100405n] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Dan R. Denomme
- Department of Chemistry and Center for Catalysis, University of Florida, Gainesville, Florida 32611-7200
| | - Seth M. Dumbris
- Department of Chemistry and Center for Catalysis, University of Florida, Gainesville, Florida 32611-7200
| | - I. F. Dempsey Hyatt
- Department of Chemistry and Center for Catalysis, University of Florida, Gainesville, Florida 32611-7200
| | - Khalil A. Abboud
- Department of Chemistry and Center for Catalysis, University of Florida, Gainesville, Florida 32611-7200
| | - Ion Ghiviriga
- Department of Chemistry and Center for Catalysis, University of Florida, Gainesville, Florida 32611-7200
| | - Lisa McElwee-White
- Department of Chemistry and Center for Catalysis, University of Florida, Gainesville, Florida 32611-7200
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Zydor A, Elliott SD. Thermal Stability of Precursors for Atomic Layer Deposition of TiO2, ZrO2, and HfO2: An Ab Initio Study of α-Hydrogen Abstraction in Bis-cyclopentadienyl Dimethyl Complexes. J Phys Chem A 2010; 114:1879-86. [DOI: 10.1021/jp9072608] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Aleksandra Zydor
- Tyndall National Institute, University College Cork, Lee Maltings, Cork, Ireland
| | - Simon D. Elliott
- Tyndall National Institute, University College Cork, Lee Maltings, Cork, Ireland
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Abstract
A self-consistent system of additive covalent radii, R(AB)=r(A) + r(B), is set up for the entire periodic table, Groups 1-18, Z=1-118. The primary bond lengths, R, are taken from experimental or theoretical data corresponding to chosen group valencies. All r(E) values are obtained from the same fit. Both E-E, E-H, and E-CH(3) data are incorporated for most elements, E. Many E-E' data inside the same group are included. For the late main groups, the system is close to that of Pauling. For other elements it is close to the methyl-based one of Suresh and Koga [J. Phys. Chem. A 2001, 105, 5940] and its predecessors. For the diatomic alkalis MM' and halides XX', separate fits give a very high accuracy. These primary data are then absorbed with the rest. The most notable exclusion are the transition-metal halides and chalcogenides which are regarded as partial multiple bonds. Other anomalies include H(2) and F(2). The standard deviation for the 410 included data points is 2.8 pm.
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Affiliation(s)
- Pekka Pyykkö
- Department of Chemistry, University of Helsinki, P.O.B. 55 (A.I. Virtasen aukio 1), 00014 Helsinki, Finland.
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Smolensky E, Eisen MS. Design of organometallic group iv heteroallylic complexes and their catalytic properties for polymerizations and olefin centered transformations. Dalton Trans 2007:5623-50. [DOI: 10.1039/b707983b] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Volkis V, Lisovskii A, Tumanskii B, Shuster M, Eisen MS. Determination of the Catalytic Active Species in the Polymerization of Propylene by Titanium Benzamidinate Complexes. Organometallics 2006. [DOI: 10.1021/om0602198] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Victoria Volkis
- Department of Chemistry and Institute of Catalysis Science and Technology, Technion−Israel Institute of Technology, Haifa, 32000, Israel, and Carmel Olefins Ltd., P.O.B. 1468, Haifa 31014, Israel
| | - Anatolii Lisovskii
- Department of Chemistry and Institute of Catalysis Science and Technology, Technion−Israel Institute of Technology, Haifa, 32000, Israel, and Carmel Olefins Ltd., P.O.B. 1468, Haifa 31014, Israel
| | - Boris Tumanskii
- Department of Chemistry and Institute of Catalysis Science and Technology, Technion−Israel Institute of Technology, Haifa, 32000, Israel, and Carmel Olefins Ltd., P.O.B. 1468, Haifa 31014, Israel
| | - Michael Shuster
- Department of Chemistry and Institute of Catalysis Science and Technology, Technion−Israel Institute of Technology, Haifa, 32000, Israel, and Carmel Olefins Ltd., P.O.B. 1468, Haifa 31014, Israel
| | - Moris S. Eisen
- Department of Chemistry and Institute of Catalysis Science and Technology, Technion−Israel Institute of Technology, Haifa, 32000, Israel, and Carmel Olefins Ltd., P.O.B. 1468, Haifa 31014, Israel
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Wang R, Zhang XH, Chen SJ, Yu X, Wang CS, Beach DB, Wu YD, Xue ZL. Reactions of d0 Group 4 Amides with Dioxygen. Preparation of Unusual Oxo Aminoxy Complexes and Theoretical Studies of Their Formation. J Am Chem Soc 2005; 127:5204-11. [PMID: 15810856 DOI: 10.1021/ja042307u] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Reactions of d0 amides M(NMe2)4 (M = Zr, 1; Hf, 2) with O2 have been found to yield unusual trinuclear oxo aminoxide complexes M3(NMe2)6(mu-NMe2)3(mu3-O)(mu3-ONMe2) (M = Zr, 3; Hf, 4) in high yields. Tetramethylhydrazine Me2N-NMe2 was also observed in the reaction mixtures. Crystal structures of 3 and 4 have been determined. Density functional theory calculations have been performed to explore the mechanistic pathways in the reactions of model complexes Zr(NR2)4 (R = H, 5; Me, 1) and [Zr(NR2)4]2 (R = H, 5a; Me, 1a) with triplet O2. Monomeric and dimeric reaction pathways in the formation of the Zr complex 3 are proposed.
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Affiliation(s)
- Ruitao Wang
- Department of Chemistry, The University of Tennessee, Knoxville, Tennessee 37996-1600, USA
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Fenno RD, Halls MD, Raghavachari K. Hafnium Oxide and Zirconium Oxide Atomic Layer Deposition: Initial Precursor and Potential Side-Reaction Product Pathways with H/Si(100)-2×1. J Phys Chem B 2005; 109:4969-76. [PMID: 16863156 DOI: 10.1021/jp048663g] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Hybrid density functional calculations have been carried out using cluster models of the H/Si(100)-2 x 1 surface to investigate the mechanistic details of the initial surface reactions occurring in the atomic layer deposition of hafnium and zirconium oxides (HfO2 and ZrO2). Reaction pathways involving the metal precursors ZrCl4, Zr(CH3)4, HfCl4, and Hf(CH3)4 have been examined. Pathways leading to the formation of a Zr-Si or Hf-Si linkage show a significant sensitivity to the identity of the leaving group, with chloride loss reactions being both kinetically and thermodynamically less favorable than reactions leading to the loss of a methyl group. The energetics of the Zr(CH3)4 and Hf(CH3)4 reactions are similar with an overall exothermicity of 0.3-0.4 eV and a classical barrier height of 1.1-1.2 eV. For the reaction between H2O and the H/Si(100)-2 x 1 surface, the activation energy and overall reaction enthalpy are 1.6 and -0.8 eV, respectively. Due to contamination, trace amounts of H2O may be encountered by metal precursors, leading to the formation of minor species that can lead to unanticipated side-reaction pathways. Such gas-phase reactions between the halogenated and alkylated metal precursors and H2O are exothermic with small or no reaction barriers, allowing for the possibility of metal precursor hydroxylation before the H/Si surface is encountered. Of the contaminant surface reaction pathways, the most kinetically favorable corresponds to the surface -OH deposition. Interestingly, for the hydroxylated metal precursors, a unique reaction pathway resulting in the direct formation of Si-O-Zr and Si-O-Hf linkages has been identified and found to be the most thermodynamically stable pathway available, being exothermic by approximately 1.0 eV.
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Affiliation(s)
- Ryan D Fenno
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, USA
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Itazaki M, Yoda C, Nishihara Y, Osakada K. C−C and C−H Bond Activation of Dialkylmethylenecyclopropane Promoted by Rhodium and Iridium Complexes. Preparation and Structures of M(η1:η2-CH2CR2CHCH2)(CO)(PPh3)2 and trans-M(CHCHCMeR2)(CO)(PPh3)2 (M = Rh, Ir, R = CH2CH2Ph). Organometallics 2004. [DOI: 10.1021/om049632a] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Masumi Itazaki
- Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
| | - Chikako Yoda
- Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
| | - Yasushi Nishihara
- Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
| | - Kohtaro Osakada
- Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
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Yu X, Bi S, Guzei IA, Lin Z, Xue ZL. Zirconium, Hafnium, and Tantalum Amide Silyl Complexes: Their Preparation and Conversion to Metallaheterocyclic Complexes via γ-Hydrogen Abstraction by Silyl Ligands. Inorg Chem 2004; 43:7111-9. [PMID: 15500349 DOI: 10.1021/ic049023v] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
New transition metal silyl amide complexes (Me(2)N)(3)Ta[N(SiMe(3))(2)](SiPh(2)Bu(t)) (1) and (Me(2)N)M[N(SiMe(3))(2)](2)(SiPh(2)Bu(t)) (M = Zr, 2a, and Hf, 2b) were found to undergo gamma-H abstraction by the silyl ligands to give metallaheterocyclic complexes (3) and (M = Zr, 4a, and Hf, 4b), respectively. The conversion of 1 to 3 follows first-order kinetics with DeltaH() = 23.6(1.6) kcal/mol and DeltaS() = 3(5) eu between 288 and 313 K. The formation of 4a from (Me(2)N)Zr[N(SiMe(3))(2)](2)Cl (5a) and Li(THF)(2)SiPh(2)Bu(t) (6) involves the formation of the intermediate 2a, followed by gamma-H abstraction. Kinetic studies of these consecutive reactions, a second-order reaction to give 2a and then a first-order gamma-H abstraction to give 4a, were conducted by an analytical method and a numerical method. At 278 K, the rate constants k(1) and k(2) for the two consecutive reactions are 2.17(0.03) x 10(-)(3) M(-)(1) s(-)(1) and 5.80(0.15) x 10(-)(5) s(-)(1) by the analytical method. The current work is a rare kinetic study of the A + B --> C --> D (+ E) consecutive reactions. Kinetic studies of the formation of a metallaheterocyclic moiety have, to our knowledge, not been reported. In addition, gamma-H abstraction by a silyl ligand to give such a metallaheterocyclic moiety is new. Theoretical investigations of the gamma-H abstraction by silyl ligands have been conducted by density functional theory calculations at the Becke3LYP (B3LYP) level, and they revealed that the formation of the metallacyclic complexes through gamma-H abstraction is entropically driven. X-ray crystal structures of (Me(2)N)(3)Ta[N(SiMe(3))(2)](SiPh(2)Bu(t)) (1), (Me(2)N)Zr[N(SiMe(3))(2)](2)Cl (5a), and (M = Zr, 4a, and Hf, 4b) are also reported.
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Affiliation(s)
- Xianghua Yu
- Department of Chemistry, The University of Tennessee, Knoxville, Tennessee 37996-1600, USA
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Yu X, Morton LA, Xue ZL. Transition-Metal Silyl Complexes and Chemistry in the Reactions of Silanes with Transition-Metal Complexes. Organometallics 2004. [DOI: 10.1021/om049862p] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Xianghua Yu
- Department of Chemistry, The University of Tennessee, Knoxville, Tennessee 37996
| | - Laurel A. Morton
- Department of Chemistry, The University of Tennessee, Knoxville, Tennessee 37996
| | - Zi-Ling Xue
- Department of Chemistry, The University of Tennessee, Knoxville, Tennessee 37996
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Alladin T, Beaudoin MC, Scott SL. Thermolysis of silica-supported bis(neopentyl) complexes of titanium and zirconium. Inorganica Chim Acta 2003. [DOI: 10.1016/s0020-1693(02)01272-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Silyl-substituted alkylidenes: preparation of the novel complexes and mechanistic studies of their formation from reactions of alkylidenes with silanes and silyl-to-alkylidyne migration. ACTA ACUST UNITED AC 2002. [DOI: 10.1016/s1381-1169(02)00221-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Castro A, Galakhov M, Gómez M, Gómez-Sal P, Martín A. Synthesis of Hydride Tantalabenzocyclopentene and µ-Alkylidene Complexes by Direct Alkylation Reactions of [TaCp*Cp′Cl2] − NMR Spectroscopic Study and X-ray Crystal Structure of [TaCp*Cp′(H)(η2-CH2-CMe2-o-C6H4)], (Cp* = η5-C5Me5; Cp′ = η5-C5H4SiMe3). Eur J Inorg Chem 2002. [DOI: 10.1002/1099-0682(200206)2002:6<1336::aid-ejic1336>3.0.co;2-r] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Affiliation(s)
- Richard R Schrock
- Department of Chemistry 6-331, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
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Herndon JW. The chemistry of the carbon–transition metal double and triple bond: annual survey covering the year 1999. Coord Chem Rev 2001. [DOI: 10.1016/s0010-8545(00)00394-5] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Beckhaus R, Santamarı́a C. Carbene complexes of titanium group metals—formation and reactivity. J Organomet Chem 2001. [DOI: 10.1016/s0022-328x(00)00710-5] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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