249:
418:-labilizing ligands, which can be explained by stabilization of the intermediate that results upon CO dissociation. This can be attributed to the partial interaction of the oxygen from the thiobenzoate and the metal, which can eliminate
158:
to ligand X. CO is a neutral ligand that donates 2 electrons to the complex, and therefore lacks anionic or cationic properties that would affect the electron count of the complex. For transition metal complexes that have the formula
590:
Atwood, J.; Brown, Theodore L. (1976). "Cis labilization of ligand dissociation. 3. Survey of group 6 and 7 six-coordinate carbonyl compounds. The site preference model for ligand labilization effects".
437:
to X, which is hypothesized to be due to the weak pi-accepting and/or sigma donating behavior of ligand X. This lack of strong sigma donation/pi-accepting will allow the CO (a strong pi-acceptor)
678:
Kovacs, A.; Frenking, Gernot (2001). "Stability and
Bonding Situation of Electron-Deficient Transition-Metal Complexes. Theoretical Study of the CO-Labilizing Effect of Ligands L in (L = C
225:
position to the X, followed by the association of ligand Y. This is an example of a dissociative mechanism, where an 18 e complex loses a CO ligand, making a 16 e
523:
425:
Note that the strongest labilizing effects come from ligands that are weak sigma donors with virtually no pi-accepting behavior. The
172:, group 6 metals (M, where the oxidation state of the metal is zero) paired with neutral ligand X, and group 7 metals (M, where the
662:
445:
toward it, strengthening the M-CO bond. This phenomenon is further supported by the evidence from extensive studies on the
229:, and a final complex of 18 e results from an incoming ligand inserting in place of the CO. This mechanism resembles the
571:
546:
507:
461:
effects seem to have generally opposite trends, the electronic argument supports both phenomena. Further evidence for
812:
802:
449:
effect, which in turn shows how ligands that are actually strong sigma donors and pi-acceptors weaken the M-L bond
95:
402:
complexes. This is because these ligands will stabilize the 16 e intermediate by electron donation from the p-pi
184:, and 18 electrons will in turn fill these valences shells, creating a very stable complex, which satisfies the
65:
807:
214:
45:
35:
242:
414:-containing ligands, particularly thiobenzoate, are other examples of particularly useful CO
226:
433:. It has also been determined that labilizing X ligands do in fact strengthen the M-CO bond
627:
68:
8:
20:
631:
778:
517:
57:
658:
567:
542:
503:
465:
labilization of CO can be attributed to the CO ligands being in competition for the d
407:
238:
196:
position creates a square pyramidal transition state, which lowers the energy of the
782:
770:
743:
635:
600:
442:
430:
210:
185:
177:
103:
419:
294:
173:
138:
134:
28:
53:
774:
192:-labilization of 18 e complexes suggests that dissociation of ligand X in the
154:
have been found to be the most prominent in regards to dissociation of the CO
796:
181:
230:
88:
422:
that can occur during ligand dissociation in transition metal complexes.
302:
604:
761:
Asali, K. J.; Janaydeh, Husam Al (2003). "Transition Metal
Chemistry".
107:
747:
176:
of the metal is +1), paired anionic ligands, will create very stable
639:
403:
385:
429:
effect can be attributed to the role of ligand X in stabilizing the
381:
377:
364:
734:) and the Structure of the 16-Valence-Electron Complexes and ".
478:
368:
360:
271:
complexes. If ligands X and Y are neutral donors to the complex:
41:
31:
129:
411:
352:
332:
477:
orbitals. This argument especially holds true when the X is a
248:
389:
106:
complexes. It has been determined that ligands that are weak
325:
16:
Destabilization of CO ligands that are cis to other ligands
618:
Jensen, W. (2005). "The Origin of the 18-Electron Rule".
280:
110:
donors and non-pi acceptors seem to have the strongest
27:
is defined as the labilization (or destabilization) of
122:-effect, which effectively labilizes ligands that are
83:
where X is the ligand that will labilize a CO ligand
502:(2nd ed.). New York: Oxford University Press.
126:to strong pi accepting and sigma donating ligands.
392:have particularly strong CO labilizing effects in
794:
566:(5th ed.). New York: W. H. Freeman and Co.
539:Inorganic and organometallic reaction mechanisms
94:, which is most often observed in 4-coordinate
677:
102:effect is observed in 6-coordinate octahedral
760:
180:complexes. Transition metal complexes have 9
130:Electron counting in metal carbonyl complexes
522:: CS1 maint: multiple names: authors list (
498:Miessler, Gary O. Spessard, Gary L. (2010).
40:to other ligands. CO is a well-known strong
589:
564:Shriver & Atkins' inorganic chemistry
52:position when adjacent to ligands due to
652:
497:
60:. The system most often studied for the
258:. Intermediates in the substitution of
795:
617:
561:
536:
541:(2. ed.). New York : Wiley-VCH.
118:effect has the opposite trend of the
655:Advances in Organometallic Chemistry
585:
583:
293:-labilizing effects are as follows:
114:-labilizing effects. Therefore, the
289:The order of ligands which possess
13:
247:
14:
824:
580:
754:
671:
646:
611:
555:
530:
491:
213:. The scheme below shows the
1:
484:
710:, F, Cl, OH, SH) and (L = O
7:
277:M = Group 7 metal (m = +1)
141:transition metal complexes
10:
829:
274:M = Group 6 metal (m = 0)
48:that will labilize in the
653:Hill AF, Fink MJ (2010).
813:Chemical bond properties
803:Organometallic chemistry
500:Organometallic chemistry
376:Anionic ligands such as
46:organometallic chemistry
775:10.1023/A:1022953903025
657:. Oxford: Academic Pr.
537:Atwood, Jim D. (1997).
209:complex, enhancing the
562:Atkins, Peter (2010).
281:Ligands effects on CO
252:
243:coordination compounds
217:of a CO ligand in the
251:
44:-accepting ligand in
441:to ligand X to pull
215:dissociation pathway
632:2005JChEd..82...28J
605:10.1021/ja00427a017
453:to them. Since the
21:inorganic chemistry
808:Carbonyl complexes
763:Transit. Met. Chem
253:
87:to it. Unlike the
58:electronic effects
748:10.1021/om0101893
742:(12): 2510–2524.
664:978-0-12-378649-4
599:(11): 3160–3166.
241:, and applies to
239:organic chemistry
820:
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443:electron density
431:transition state
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211:rate of reaction
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186:18-electron rule
182:valence orbitals
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104:transition metal
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98:complexes, the
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769:(2): 193–198.
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285:-labilization
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237:mechanism in
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96:square planar
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64:effect is an
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375:
290:
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273:
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227:intermediate
222:
218:
193:
189:
155:
133:
123:
119:
115:
111:
99:
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84:
61:
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363:, NCO <
320:< P(O)Ph
178:18 electron
797:Categories
485:References
66:octahedral
25:cis effect
626:(1): 28.
518:cite book
410:. Other
404:lone pair
245:as well.
34:that are
783:91996293
686:, NCH, N
256:Figure 1
628:Bibcode
479:halogen
473:, and d
408:orbital
335:< CH
297:, AuPPh
139:group 7
135:Group 6
69:complex
32:ligands
781:
661:
570:
545:
506:
412:sulfur
406:donor
388:, and
309:, GePh
305:, SnPh
188:. The
92:effect
54:steric
23:, the
779:S2CID
459:trans
451:trans
447:trans
439:trans
435:trans
367:<
359:<
351:<
331:<
324:<
315:M(CO)
260:M(CO)
223:trans
198:M(CO)
161:M(CO)
143:M(CO)
124:trans
120:trans
108:sigma
90:trans
72:M(CO)
706:, NH
702:, SH
698:, OH
659:ISBN
568:ISBN
543:ISBN
524:link
504:ISBN
457:and
343:, NC
221:and
137:and
56:and
771:doi
744:doi
722:, S
690:, C
636:doi
601:doi
469:, d
463:cis
455:cis
427:cis
416:cis
326:PPh
291:cis
283:cis
219:cis
194:cis
190:cis
156:cis
116:cis
112:cis
100:cis
85:cis
62:cis
50:cis
37:cis
19:In
799::
777:.
767:28
765:.
740:20
738:.
634:.
624:82
622:.
597:98
595:.
582:^
520:}}
516:{{
481:.
475:xz
471:yz
467:xy
390:SH
386:OH
384:,
382:Cl
380:,
369:NO
365:Cl
361:Br
357:CO
353:CH
339:SO
313:,
301:,
295:CO
42:pi
29:CO
785:.
773::
750:.
746::
732:2
730:H
728:2
726:C
724:2
720:2
718:H
716:2
714:C
712:2
708:3
704:2
700:2
696:4
694:H
692:2
688:2
684:2
682:H
680:2
667:.
642:.
638::
630::
607:.
603::
576:.
551:.
526:)
512:.
378:F
371:3
355:3
349:5
347:H
345:5
341:2
337:3
333:I
328:3
322:3
317:n
311:3
307:3
303:H
299:3
269:X
265:5
235:1
233:N
231:S
207:X
203:4
170:X
166:5
152:X
148:5
81:X
77:5
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