88:: the metal forms a π bond with the carbonyl ligand by donating electrons through its d orbitals into the empty π* anti-bonding orbitals on CO. This interaction strengthens the metal-carbon bond but also weakens the carbon-oxygen bond, resulting in a lower vibrational frequency. If other ligands increase the density of π electrons on the metal, the C-O bond is weakened and ν(CO) decreases further; conversely, if other ligands compete with CO for π backbonding, ν(CO) increases.
73:
17:
253:
Several other scales have been proposed for the ranking of the donor properties of ligands. The HEP scale ranks ligands on the basis of the C NMR shift of a reference ligand. Lever's electronic parameter ranking is related to the Ru(II/III) couple. Another scale evaluated ligands on the basis of
83:
carbonyl band is rarely obscured by other bands in the analyte's infrared spectrum. Carbonyl is a small ligand so steric factors do not complicate the analysis. Upon coordination of CO to a metal, ν(CO) typically decreases from 2143 cm of free CO. This shift can be explained by
403:
Lever, A. B. P. (1990). "Electrochemical parametrization of metal complex redox potentials, using the ruthenium(III)/Ruthenium(II) couple to generate a ligand electrochemical series".
63:. The shift in ν(CO) is used to infer the electronic properties of a ligand, which can aid in understanding its behavior in other complexes. The analysis was introduced by
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Chatt, Joseph; Kan, C. T.; Leigh, G. Jeffery; Pickett, Christopher J.; Stanley, David R. (1980). "Transition-metal binding sites and ligand parameters".
368:
Teng, Qiaoqiao; Huynh, Han Vinh (2017). "A Unified Ligand
Electronic Parameter Based on C NMR Spectroscopy of N-Heterocyclic Carbene Complexes".
92:
600:
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455:"Experimental and theoretical investigations on the high-electron donor character of pyrido-annelated N-heterocyclic carbenes"
610:
153:
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Huynh, Han Vinh (30 March 2018). "Electronic
Properties of N-Heterocyclic Carbenes and Their Experimental Determination".
605:
123:
59:, where L is the ligand of interest. was chosen as the model compound because such complexes are readily prepared from
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Tolman, C. A. (1977). "Steric effects of phosphorus ligands in organometallic chemistry and homogeneous catalysis".
187:
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Tonner, Ralf; Frenking, Gernot (2009). "Tolman's
Electronic Parameters for Divalent Carbon(0) Compounds".
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56:
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Gusev, Dmitry G. (2009). "Electronic and Steric
Parameters of 76 N-Heterocyclic Carbenes in Ni(CO)
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261:(NHC) ligands have been ranked according to IR data recorded on cis- complexes.
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304:(2005). "Carbonyls, Phosphine Complexes, and Ligand Substitution Reactions".
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Nonnenmacher, Michael; Buck, Dominik M; Kunz, Doris (23 August 2016).
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40:) is a measure of the electron donating or withdrawing ability of a
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In a treatment akin to the TEP analysis, the donor properties of
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44:. It is determined by measuring the frequency of the A
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97:
432:
Journal of the
Chemical Society, Dalton Transactions
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48:C-O vibrational mode (ν(CO)) of a (pseudo)-C
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459:Beilstein Journal of Organic Chemistry
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249:Other ligand electronic parameters
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28:L used to determine the TEP of L.
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1:
99:TEP for selected phosphines
516:10.1021/acs.chemrev.8b00067
34:Tolman electronic parameter
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601:Organometallic chemistry
24:"stretch" mode of Ni(CO)
254:the redox couples of .
314:10.1002/0471718769.ch4
259:N-heterocyclic carbene
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61:tetracarbonylnickel(0)
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611:Infrared spectroscopy
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57:infrared spectroscopy
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440:10.1039/DT9800002032
606:Inorganic chemistry
471:10.3762/bjoc.12.178
417:10.1021/ic00331a030
405:Inorganic Chemistry
370:Dalton Transactions
355:10.1021/cr60307a002
308:. pp. 87–124.
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382:10.1039/C6DT04222H
302:Robert H. Crabtree
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65:Chadwick A. Tolman
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584:10.1021/om900654g
578:(22): 6458–6461.
557:10.1021/om900206w
551:(13): 3901–3905.
510:(19): 9457–9492.
279:Tolman cone angle
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595:Categories
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288:References
107:ν(CO) cm
53:symmetric
568:(NHC)".
524:29601194
489:27829895
390:27924321
268:See also
480:5082490
242:2110.8
229:2097.0
216:2076.3
203:2071.3
182:2068.9
148:2064.1
135:2061.9
118:2056.1
112:P(t-Bu)
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209:P(OEt)
42:ligand
169:2066
124:P(NMe
79:The A
20:The A
520:PMID
485:PMID
386:PMID
318:ISBN
162:OMe)
32:The
580:doi
553:doi
512:doi
508:118
475:PMC
467:doi
436:doi
413:doi
378:doi
351:doi
310:doi
222:PCl
188:P(C
175:PPh
154:P(C
141:PMe
38:TEP
597::
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549:28
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332:^
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235:PF
196:F)
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50:3v
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192:H
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177:3
164:3
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158:H
156:6
143:3
130:3
128:)
126:2
114:3
104:L
81:1
46:1
36:(
26:3
22:1
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