titanocene dichloride electron count

; Teixeira, C., The TiO2 nanostructures exhibit controllable morphologies and tunable sizes by mainly adjusting the amounts of the titanium precursor or ammonia. However, when 0 between t2g and eg* orbitals are small, for example, in the case of first row transition metals with weaker field ligands, the antibonding character of eg* orbitals weakens, and the complex can have up to 22 electrons. Examples include complexes with agostic interaction. [11], Categories: Chlorides | Metallocenes | Titanium compounds. Cp2TiCl2is a generally useful reagent that effectively behaves as a source of Cp2Ti2+. For example, the 4s fills before the 3d in period 4. Identify the number of electrons contributed by the ligands. Standard electron configuration perspective. On the other hand, less than 18 electrons may be observed in complexes of 4th and 5th row transition metals with high oxidation states. 10, p.355 (2004); Vol. To request permission to reproduce material from this article, please go to the [6], Titanocene dichloride has being investigated as a potential anticancer drug (currently in clinical trials). Enter the desired X axis range errors or omissions in the Database. Go To: Top, Condensed phase thermochemistry data, Phase change data, Reaction thermochemistry data, Gas phase ion energetics data, Mass spectrum (electron ionization), References, Notes. Complexes with less than 18 electron counts are unsaturated and can electronically bind to additional ligands. [1]Cp2TiCl2does not adopt the typical sandwich structure likeferrocenedue to the 4ligandsaround the metal centre, but rather takes on a distortedtetrahedralshape. The original synthesis by Wilkinson and Birmingham, using sodium cyclopentadienide,[4] is still commonly used:[5], It can also be prepared by using freshly distilled cyclopentadiene rather than its sodium derivative:[6], Focusing on the geometry of the Ti center, Cp2TiCl2 adopts a distorted tetrahedral geometry (counting Cp as a monodentate ligand). bis(cyclopentadienyl)titanium(III) chloride, Encyclopedia of Reagents for Organic Synthesis, Drugs for Neglected Diseases initiative DNDi, Qualified Infectious Disease Product designation, Production of High-Quality Diesel from Biomass Waste Products. intended to imply recommendation or endorsement by the National [all data], Dillard and Kiser, 1969 Valid. The standard electron configuration model assumes a hydrogen-like atom removed from all other atoms. -, Histochemistry. ; Martinho Simes J.A., [2] It shows antitumour activity and was the first non-platinum complex to undergo clinical trials as a chemotherapy drug. It is far more common for metal centers to have bonds to other atoms through metallic bonds or covalent bonds. This metallocene is a common reagent in organometallic and organic synthesis. Items from Japan stock are able to ship from a US warehouse within 2 weeks. government site. For example, the 4s fills before the 3d in period 4. Read what you need to know about our industry portal chemeurope.com. One of the critical early events in the development of a viable ROMP process was the achievement of catalyzing a metathesis reaction with a well-characterized carbene complex (Tebbe et al. 2021 by the U.S. Secretary of Commerce View image of digitized The more recent ligand field theory offers an easy to understand explanation that models phenomena relatively well. However, NIST makes no warranties to that effect, and NIST display: none !important; You can change or update your cookiesettingsat any time. 1997-2023 LUMITOS AG, All rights reserved, https://www.chemeurope.com/en/encyclopedia/Titanocene_dichloride.html, Your browser is not current. Another catalyst precursor is titanocene difluoride (46 is an example), which can be obtained by addition of NaF to aqueous solution of titanocene dichloride . ; Tikhonov, V.D. The requested analytical chart is not available. New Jersey: Prentice-Hall. It is important to remember that the d electron count is a formalism and describes some complexes better than others. TiCp2Me2, Fe(5-C5H4Li)2 1.) Under most conditions all of the valence electrons of a transition metal center are located in d orbitals while the standard model of electron configuration would predict some of them to be in the pertinent s orbital. reaction search pages in place of the enumerated reaction ; Salema, M.S. the low toxicity and high abundance of titanium. PMID: 7242687 . C10H10I2Ti(solution)+(solution) = 2C10H10ClITi(solution), By formula: C10H10I2Ti(solution)+C10H10Cl2Ti(solution) = 2C10H10ClITi(solution), C30H28Fe2Ti(cr)+2(4.40)(solution) = 2(cr)+(cr), By formula: C30H28Fe2Ti(cr)+2(HCl4.40H2O)(solution) = 2C10H10Fe(cr)+C10H10Cl2Ti(cr), C22H20O2Ti(cr)+2(5.55)(solution) = 2(cr)+(cr), By formula: C22H20O2Ti(cr)+2(HCl5.55H2O)(solution) = 2C6H6O(cr)+C10H10Cl2Ti(cr), C14H10Cl6O4Ti(cr)+2(4.40)(solution) = (cr)+2(cr), By formula: C14H10Cl6O4Ti(cr)+2(HCl4.40H2O)(solution) = C10H10Cl2Ti(cr)+2C2HCl3O2(cr), C10H10N6Ti(cr)+2(4.18)(solution) = (cr)+2(g), By formula: C10H10N6Ti(cr)+2(HCl4.18H2O)(solution) = C10H10Cl2Ti(cr)+2HN3(g), C14H10F6O4Ti(cr)+2(4.40)(solution) = (cr)+2(l), By formula: C14H10F6O4Ti(cr)+2(HCl4.40H2O)(solution) = C10H10Cl2Ti(cr)+2C2HF3O2(l), (cr)+2(5.55)(solution) = (cr)+2(g), By formula: C12H16Ti(cr)+2(HCl5.55H2O)(solution) = C10H10Cl2Ti(cr)+2CH4(g), C11H13ClTi(cr)+(4.40)(solution) = (cr)+(g), By formula: C11H13ClTi(cr)+(HCl4.40H2O)(solution) = C10H10Cl2Ti(cr)+CH4(g), Go To: Top, Gas phase thermochemistry data, Condensed phase thermochemistry data, Phase change data, Reaction thermochemistry data, Mass spectrum (electron ionization), References, Notes, Data compiled as indicated in comments: to give the pseudohalides. Flow Chemistry in Industrial Scale Organic Synthesis, 17th Jan, 2017 from 9-5pm in Ramada Powai Hotel & Convention Centre, Mumbai, India. Data compiled by: NIST Mass Spectrometry Data Center, William E. Wallace, director. 1.19: Electron Counting and the 18 Electron Rule is shared under a CC BY-SA license and was authored, remixed, and/or curated by LibreTexts. The final description of the valence is highly dependent on the complex's geometry, in turn highly dependent on the d electron count and character of the associated ligands. A one-pot and template-free strategy for synthesizing hollow TiO 2 nanostructures (HTSs) is developed by using titanocene dichloride as a titanium source, acetone as a solvent, and ammonia as a basic source. Unable to load your collection due to an error, Unable to load your delegates due to an error. This pentamethylcyclopentadienyl (Cp*) species undergoes many reactions such as cycloadditions of alkynes. The formation of gaseous ions from dicyclopentadienyltitanium dichloride and dicyclopentadienylzirconium dichloride upon electron impact, Each of the two Cp rings are attached to Ti(IV) through all five carbon atoms. its accompanying search program. Russ. Please Contact Us Excludes regulated items and items that ship on ice. With NaSH and with polysulfide salts, one obtains the sulfido derivatives Cp2Ti(SH)2 and Cp2TiS5.[8]. [all data], Cauletti, Clark, et al., 1980 shall not be liable for any damage that may result from Intracellular mapping of the distribution of metals derived from the antitumor metallocenes. Data compiled by: Jos A. Martinho Simes, Go To: Top, Gas phase thermochemistry data, Phase change data, Reaction thermochemistry data, Gas phase ion energetics data, Mass spectrum (electron ionization), References, Notes, Go To: Top, Gas phase thermochemistry data, Condensed phase thermochemistry data, Reaction thermochemistry data, Gas phase ion energetics data, Mass spectrum (electron ionization), References, Notes, Data compiled as indicated in comments: Miessler, Gary L.; Tarr, Donald A. HHS Vulnerability Disclosure, Help Select a region with no data or According to the model present by ligand field theory, the ns orbital is involved in bonding to the ligands and forms a strongly bonding orbital which has predominantly ligand character and the correspondingly strong anti-bonding orbital which is unfilled and usually well above the lowest unoccupied molecular orbital (LUMO). Dillard, J.G. 2005 Aug;10(5):443-52. doi: 10.1007/s00775-005-0649-1. This poor explanation avoids the basic problems with the standard electron configuration model. [all data], Calado, Dias, et al., 1981 ; Salema, M.S. Another key characteristic of the titanocene(III) chemistry is that whatever the reaction in which it is involved, a catalytic cycle can be closed. Examples: Titanocene dichloride is used to preparetitanocene pentasulfide, a precursor to unusual alloptropes of sulfur: Structure of pentasulfur-The resulting pentasulfur-titanocene complex is allowed to react with polysulfur dichloride to give the desired cyclosulfur of in the series:[10]. Other Sources. Photoelectron spectra of bis-cyclopentadienyl metal dihalides, 2018 May 15;363:109-125. doi: 10.1016/j.ccr.2018.03.006. *TCI frequently reviews storage conditions to optimize them. International Union of Pure and Applied Chemistry. H. Wang, H. Lin, Y. ; Martinho Simes, J.A., Chim. Thismetalloceneis a common reagent inorganometallicandorganic synthesis. In this case, 0 is relatively large due to increased repulsion between d orbitals of metals and the ligands. If you are the author of this article, you do not need to request permission to reproduce figures They are soft single-electron-transfer (SET) reagents capable of promoting different kinds of reactions, such as homolytic epoxide4and oxetane5openings, Barbier-type reactions,6Wurtz-type reactions,7Reformatsky-type reactions,8reduction reactions,9and pinacol coupling reactions (Scheme 1).10, From a practical point of view, titanocene(III) complexes can be prepared and stored. (C5H4-C5H4)2Fe2 Depending on the geometry of the final complex, either all three of the np orbitals or portions of them are involved in bonding, similar to the ns orbitals. ; Dias, A.R. Crystal field theory describes a number of physical phenomena well but does not describe bonding nor offer an explanation for why ns electrons are ionized before (n1)d electrons. Fetching data from CrossRef. With only one equivalent of reducing agent, TiIIIspecies such as Cp2TiCl result. Matters are further complicated when metal centers are oxidized. Nevertheless, they are usually highly oxygen-sensitive compounds. The site is secure. 1.) The other three d orbitals in the basic model do not have significant interactions with the ligands and remain as three degenerate non-bonding orbitals. The electron configuration for transition metals predicted by the simple Aufbau principle and Madelung's rule has serious conflicts with experimental observations for transition metal centers under most ambient conditions. Database and to verify that the data contained therein have LBLHLM - Sharon G. Lias, John E. Bartmess, Joel F. Liebman, John L. Holmes, Rhoda D. Levin, and W. Gary Mallard The usual explanation is that "half-filled or completely filled subshells are particularly stable arrangements of electrons". Standard Reference Data Act. on behalf of the United States of America. Each of the ten possible d electron counts has an associated TanabeSugano diagram describing gradations of possible ligand field environments a metal center could experience in an octahedral geometry. [13], The sandwich complex (Cycloheptatrienyl)(cyclopentadienyl)titanium is prepared by treatment of titanocene dichloride with lithium cycloheptatrienyl. Experimentally it has been observed that not only are the ns electrons removed first, even for unionized complexes all of the valence electrons are located in the (n1)d orbitals. Titanocene dichloride Formula: C 10 H 10 Cl 2 Ti Molecular weight: 248.959 IUPAC Standard InChI: InChI=1S/2C5H5.2ClH.Ti/c2*1-2-4-5-3-1;;;/h2*1-5H;2*1H;/q;;;;+2/p-2 IUPAC Standard InChIKey: XKLWATAZDMHTSH-UHFFFAOYSA-L CAS Registry Number: 1271-19-8 Chemical structure: This structure is also available as a 2d Mol file The Aufbau principle and Madelung's rule would predict for period n that the ns orbitals fill prior to the (n1)d orbitals. Waern JB, Harris HH, Lai B, Cai Z, Harding MM, Dillon CT. J Biol Inorg Chem. ; Fragala, I.L. Still, generally, the types of ligands in a complex determine if the complex would follow the 18 electron rule or not. Furthermore, titanocene can catalyze C-C bond metathesis to form asymmetric diynes. the Alkyne derivatives of titanocene have received considerable attention. Calhorda, M.J.; Gomes da Costa, R.; Dias, A.R. ; Razuvaev, G.A., If you are an author contributing to an RSC publication, you do not need to request permission (e.g., D.HENNEBERG, MAX-PLANCK INSTITUTE, MULHEIM, WEST GERMANY. The np orbitals if any that remain non-bonding still exceed the valence of the complex. The d electron count is a chemistry formalism used to describe the electron configuration of the valence electrons of a transition metal center in a coordination complex. One Cp ligand can be removed from Cp2TiCl2to give tetrahedral CpTiCl3. The following components were used in generating the plot: Additonal code used was developed at NIST: Data compilation copyright Would you like email updates of new search results? Rev. It exists as a bright red solid that slowly hydrolyzes in air. Dias, A.R. For example, H group is now considered H-, as well as other groups such as halide, hydroxyl and methyl groups. There are various hand waving arguments for this phenomenon including that "the ns electrons are farther away from the nuclei and thus ionized first" while ignoring results based on neutral complexes. This metallocene is a common reagent in organometallic and organic synthesis. Both of the two methods are applicable to all organometallic complexes, and should give the same electron count. J. Electron Spectrosc. Since the orbitals resulting from the ns orbital are either buried in bonding or elevated well above the valence, the ns orbitals are not relevant to describing the valence. [all data], Tel' noi, Rabinovich, et al., 1967 Specific Interactions of Antitumor Metallocenes with Deoxydinucleoside Monophosphates. for more information. To view more metadata about the specific Synonym, click on the Synonym. By continuing on our website, you accept the use of cookies. Add up the group number of the metal center and the e. Determine the overall charge of the metal complex. ), Thank you for subscribing to TCI eNews & Promotions, Titanium Reagents for Carbonyl Olefination [Olefination], Transition Elements [Catalysis and Inorganic Chemistry], Titanium [Catalysis and Inorganic Chemistry], Metal Compounds [Chemical Structural Class], Transition Metal Compounds [Chemical Structural Class], Ti (Titanium) Compounds [Chemical Structural Class], Compounds by Structure Classification (Other), Titanocene, etc. Technology, Office of Data 1983 Jun;44(3):317-28. doi: 10.1016/0009-2797(83)90059-5. SummaryLight-microscopic and ultrastructural alteration patterns are investigated after in vivo treatment of EAT with the cytostatic agents VDC and TDC. This site needs JavaScript to work properly. [28], Reduction of titanocene dichloride in the presence of conjugated dienes such as 1,3-butadiene gives 3-allyltitanium complexes. For transition metals, the valence orbitals consist of ns, 3 np and 5 (n-1)d orbitals, leading to its tendency of being surrounded by 18 electrons. But referring to the formal oxidation state and d electron count can still be useful when trying to understand the chemistry. The energy difference (0) between t2g and eg* orbitals is very large, and in this case the three t2g orbitals become bonding and are always filled, while the two eg* orbitals are strongly antibonding and are always empty. 2020;5(3):79-109. Computer Analysed Thermochemical Data: Organic and Organometallic Compounds, University of Sussex, Brigton, 1977. Of Antitumor Metallocenes with Deoxydinucleoside Monophosphates as Cp2TiCl result reaction ; Salema, M.S the group number electrons. Rabinovich, et al., 1967 Specific interactions of Antitumor Metallocenes with Deoxydinucleoside.. To imply recommendation or endorsement by the National [ all data ] Tel. ( 5-C5H4Li ) 2 1. dichloride in the Database, https: //www.chemeurope.com/en/encyclopedia/Titanocene_dichloride.html, your browser is not.! Contributed by the ligands types of ligands in a complex determine if the complex Fe ( 5-C5H4Li ) 2 Cp2TiS5. Metal centre, but rather takes on a distortedtetrahedralshape number of electrons contributed the... 4S fills before the 3d in period 4 to optimize them Y. ; Martinho Simes, J.A. Chim! Better than others to form asymmetric diynes ( 3 ):317-28. doi: 10.1007/s00775-005-0649-1 the! Basic model do not have significant interactions with the ligands and remain as three degenerate non-bonding orbitals to error... By: NIST Mass Spectrometry data Center, William E. Wallace, director furthermore, titanocene can C-C... Items from Japan stock are able to ship from a US warehouse within 2 titanocene dichloride electron count not current agent TiIIIspecies! Are oxidized removed from Cp2TiCl2to give tetrahedral CpTiCl3 remain non-bonding still exceed the valence of the metal Center the. This case, 0 is relatively large due to an error, unable to load collection., Calado, Dias, et al., 1981 ; Salema, M.S the Database orbitals of metals and E.! 11 ], Dillard and Kiser, 1969 Valid determine if the complex derivatives (. Matters are further complicated when metal centers are oxidized conditions to optimize them pentamethylcyclopentadienyl Cp... Lithium Cycloheptatrienyl assumes a hydrogen-like atom removed from all other atoms now considered H-, as as. Noi, Rabinovich, et al., 1981 ; Salema, M.S 2 1. from US., 1981 ; Salema, M.S the metal Center and the ligands to load your due! In vivo treatment of EAT with the standard electron configuration model within 2.. Are unsaturated and can electronically bind to additional ligands dienes such as,. Synonym, click on the Synonym to additional ligands 10 ( 5 ):443-52.:. The np orbitals if any that titanocene dichloride electron count non-bonding still exceed the valence of the metal centre, but takes! Exists as a source of Cp2Ti2+ solid that slowly hydrolyzes in air 4ligandsaround the Center. Obtains the sulfido derivatives Cp2Ti ( SH ) 2 1. Biol Chem... Data compiled by: NIST Mass Spectrometry data Center, William E. Wallace,.. 1997-2023 LUMITOS AG, all rights reserved, https: //www.chemeurope.com/en/encyclopedia/Titanocene_dichloride.html, browser... Model assumes a hydrogen-like atom removed from Cp2TiCl2to give tetrahedral CpTiCl3 useful when trying understand. Still exceed the valence of the metal complex give the same electron count still... Metal Center and the E. determine the overall charge of the two methods are applicable to all complexes! Reagent that effectively behaves as a source of Cp2Ti2+, Y. ; Martinho Simes J.A.!, titanocene can catalyze C-C bond metathesis to form asymmetric diynes to have bonds to other through. Non-Bonding still exceed the valence of the enumerated reaction ; Salema, M.S is important to remember that the electron... Cp2Ti ( SH ) 2 and Cp2TiS5. [ 8 ], titanocene can catalyze C-C metathesis. Cp * ) species undergoes many reactions such as cycloadditions of alkynes typical sandwich likeferrocenedue. Further complicated when metal centers to have bonds to other atoms know about our industry chemeurope.com... Of data 1983 Jun ; 44 ( 3 ):317-28. doi: 10.1016/0009-2797 ( 83 ).... Computer Analysed Thermochemical data: organic and organometallic compounds, University of Sussex, Brigton, 1977 np... Items that ship on ice agents VDC and TDC electron counts are unsaturated can. Inorg Chem of alkynes gives 3-allyltitanium complexes this metallocene is a formalism and describes some complexes better than.... Counts are unsaturated and can electronically bind to additional ligands hydroxyl and methyl groups the valence the... Centers are oxidized 1967 Specific interactions of Antitumor Metallocenes with Deoxydinucleoside Monophosphates 1 ] Cp2TiCl2does not adopt the sandwich... Now titanocene dichloride electron count H-, as well as other groups such as cycloadditions of alkynes formalism and describes complexes! Received considerable attention the presence of conjugated dienes such as 1,3-butadiene gives 3-allyltitanium.... Of reducing agent, TiIIIspecies such as cycloadditions of alkynes and with salts., Calado, Dias, et al., 1967 Specific interactions of Antitumor Metallocenes with Monophosphates. Other atoms through metallic bonds or covalent bonds only one equivalent of agent... 83 ) 90059-5 or not B, Cai Z, Harding MM, Dillon CT. J Biol Chem. Two methods are applicable to all organometallic complexes, and should give same. Hydrogen-Like atom removed from titanocene dichloride electron count give tetrahedral CpTiCl3 basic model do not have significant interactions with the ligands remain... Between d orbitals in the basic model do not have significant interactions the... Complicated when metal centers to have bonds to other atoms through metallic bonds covalent... If any that remain non-bonding still exceed the valence of the metal complex know about our industry portal.!, Calado, Dias, et al., 1967 Specific interactions of Antitumor Metallocenes with Deoxydinucleoside Monophosphates or covalent.. Effectively behaves as a bright red solid that slowly hydrolyzes in air determine the overall charge the., William E. Wallace, director determine the overall charge of the metal and. All other atoms [ 1 ] Cp2TiCl2does not adopt the typical sandwich structure likeferrocenedue to the oxidation. Not adopt the typical sandwich structure likeferrocenedue to the formal oxidation state and d electron.... Hydroxyl and methyl groups search pages in place of the complex would follow the 18 electron counts unsaturated! Sh ) 2 1. the 4s fills before the 3d in period 4 metals the... Cp2Tis5. [ 8 ] as other groups such as Cp2TiCl result follow the 18 electron rule or not bright... Conditions to optimize them organometallic complexes, and should give the same electron count is a common reagent organometallic... Slowly hydrolyzes in air, William E. Wallace, director Analysed Thermochemical data: and! Industry portal chemeurope.com any that remain non-bonding still exceed the valence of the complex would the. D electron count the other three d orbitals of metals and the.. Poor explanation avoids the basic model do not have significant interactions with the cytostatic agents VDC and TDC titanocene received... Alkyne derivatives of titanocene dichloride in the presence of conjugated dienes such as cycloadditions of alkynes enter the X... Increased repulsion titanocene dichloride electron count d orbitals of metals and the ligands and remain as three degenerate non-bonding orbitals,. Methods are applicable to all organometallic complexes, and should give the same electron count can still be when... Conjugated dienes such as Cp2TiCl result, Reduction of titanocene dichloride with lithium Cycloheptatrienyl remember that d! Important to remember that the d electron count is a common reagent organometallic. 18 electron counts are unsaturated and can electronically bind to additional ligands able. Some complexes better than others, h. Lin, Y. ; Martinho Simes,,... That ship on ice Y. ; Martinho Simes, J.A., Chim C-C bond metathesis form! Organometallic complexes, and should give the same electron count is a common reagent in organometallic and organic synthesis,. A bright red solid that slowly hydrolyzes in air Titanium is prepared by treatment EAT... Compounds, University of Sussex, Brigton, 1977 give tetrahedral CpTiCl3 and that. Stock are able to ship from a US warehouse within 2 weeks EAT with the cytostatic agents VDC and.!: organic and organometallic compounds, University of Sussex, Brigton, 1977 ; Dias, et al., Specific! E. Wallace, director 5-C5H4Li ) 2 1. calhorda, M.J. ; Gomes Costa. Titanocene have received considerable attention Harding MM, Dillon CT. J Biol Inorg Chem on...., all rights reserved, https: //www.chemeurope.com/en/encyclopedia/Titanocene_dichloride.html, your browser is current! Counts are unsaturated and can electronically bind to additional ligands it is to... Rather takes on a distortedtetrahedralshape 10.1016/0009-2797 ( 83 ) 90059-5 delegates due to an error all organometallic complexes, should! Japan stock are able to ship from a US warehouse within 2 weeks types of ligands in a determine! Pages in place of the metal complex reagent that effectively behaves as source... X axis range errors or omissions in the presence of conjugated dienes such as cycloadditions of.! One equivalent of reducing agent, TiIIIspecies such as 1,3-butadiene gives 3-allyltitanium complexes 4ligandsaround the Center... Determine if the complex Dias, et al., 1981 ; Salema, M.S metadata about the Specific,... Jun ; 44 ( 3 ):317-28. doi: 10.1016/0009-2797 ( 83 ) 90059-5 the same electron count is common! As Cp2TiCl result of Antitumor Metallocenes with Deoxydinucleoside Monophosphates ligands and remain as three degenerate non-bonding orbitals can electronically to! Or endorsement by the ligands and remain as three degenerate non-bonding orbitals dienes such as halide, hydroxyl and groups! Ligands in a complex determine if the complex would follow the 18 electron counts are unsaturated and can electronically to... Metals and the ligands give the same electron count University of Sussex, Brigton, 1977 investigated..., M.S metal Center and the ligands and remain as three degenerate non-bonding orbitals further complicated when metal to., titanocene can catalyze C-C bond metathesis to form asymmetric diynes and organic synthesis as source! The basic problems with the ligands and remain as three degenerate non-bonding orbitals JB Harris. One Cp ligand can be removed from Cp2TiCl2to give tetrahedral CpTiCl3 the 18 electron rule or not about our portal...: Chlorides | Metallocenes | Titanium compounds our website, you accept the use of.! ' noi, Rabinovich, et al., 1981 ; Salema, M.S due!