127:
67:
176:
115:. Complexes such as this are called "low-spin" since filling an orbital matches electrons and reduces the total electron spin. If the separation between the orbitals is small enough then it is easier to put electrons into the higher energy orbitals than it is to put two into the same low-energy orbital, because of the repulsion resulting from matching two electrons in the same orbital. So, one electron is put into each of the five
163:
137:
The charge of the metal center plays a role in the ligand field and the Δ splitting. The higher the oxidation state of the metal, the stronger the ligand field that is created. In the event that there are two metals with the same d electron configuration, the one with the higher oxidation state is
246:
In the case of octahedral complexes, the question of high spin vs low spin first arises for d, since it has more than the 3 electrons to fill the non-bonding d orbitals according to ligand field theory or the stabilized d orbitals according to crystal field splitting.
138:
more likely to be low spin than the one with the lower oxidation state; for example, Fe and Co are both d; however, the higher charge of Co creates a stronger ligand field than Fe. All other things being equal, Fe is more likely to be high spin than Co.
88:
plays an important role in the electron spin state of a coordination complex. Three factors affect Δ: the period (row in periodic table) of the metal ion, the charge of the metal ion, and the field strength of the complex's ligands as described by the
34:
configurations. The ambiguity only applies to first row metals, because second- and third-row metals are invariably low-spin. These configurations can be understood through the two major models used to describe coordination complexes;
152:. Strong-field ligands, such as CN and CO, increase the Δ splitting and are more likely to be low-spin. Weak-field ligands, such as I and Br cause a smaller Δ splitting and are more likely to be high-spin.
468:
levels are anti-bonding with respect to the metal-ligand bonds. Famous "exchange inert" complexes are octahedral complexes of d and low-spin d metal ions, illustrated respectfully by Cr and Co.
96:
In order for low spin splitting to occur, the energy cost of placing an electron into an already singly occupied orbital must be less than the cost of placing the additional electron into an e
123:
resulting in what is known as a "high-spin" complex. Complexes such as this are called "high-spin" since populating the upper orbital avoids matches between electrons with opposite spin.
238:(CFT) give similar results. CFT is an older, simpler model that treats ligands as point charges. LFT is more chemical, emphasizes covalent bonding and accommodates pi-bonding explicitly.
464:
Generally, the rates of ligand dissociation from low spin complexes are lower than dissociation rates from high spin complexes. In the case of octahedral complexes, electrons in the e
191:
is smaller than that for an octahedral complex. Consequently, tetrahedral complexes are almost always high spin
Examples of low spin tetrahedral complexes include Fe(2-norbornyl)
624:
Scarborough, Christopher C.; Sproules, Stephen; Doonan, Christian J.; Hagen, Karl S.; WeyhermĂĽller, Thomas; Wieghardt, Karl (2012). "Scrutinizing Low-Spin Cr(II) Complexes".
947:
218:
Many d complexes of the first row metals exist in tetrahedral or square planar geometry. In some cases these geometries exist in measurable equilibria. For example,
111:
If the separation between the orbitals is large, then the lower energy orbitals are completely filled before population of the higher orbitals according to the
102:
orbital at an energy cost of Δ. If the energy required to pair two electrons is greater than the energy cost of placing an electron in an e
737:
219:
780:
659:
Shannon R.D. (1976). "Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides".
26:
refers to the potential spin configurations of the central metal's d electrons. For several oxidation states, metals can adopt
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887:
542:
703:
494:
922:
917:
882:
78:
1043:
932:
927:
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937:
815:
289:
730:
324:
988:
993:
533:
Zumdahl, Steven (2009). "19.6 Transition Metals and
Coordination Chemistry: The Crystal Field Model".
360:
589:-Dichlorobis(triphenylphosphine)nickel(II) Bis(dichloromethane) Solvate: Redetermination at 120 K".
433:
Octahedral low spin: Includes Fe ionic radius 62 pm, Co ionic radius 54.5 pm, Ni ionic radius 48 pm.
1048:
877:
841:
746:
723:
263:, substitutionally labile. Includes Cr (many complexes assigned as Cr(II) are however Cr(III) with
200:
44:
558:
Bower, Barton K.; Tennent, Howard G. (1972). "Transition Metal
Bicyclo[2.2.1]hept-1-yls".
688:
Kinetics and
Mechanism of Reactions of Transition Metal Complexes, 2nd Thoroughly Revised Edition
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907:
489:(2nd ed.). Upper Saddle River, New Jersey: Pearson Education, Inc. Pearson Prentice Hall.
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93:. Only octahedral complexes of first row transition metals adopt high-spin states.
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Octahedral high spin: Fe, the ionic radius is 78 pm, Co ionic radius 61 pm.
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892:
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571:
222:
has been crystallized in both tetrahedral and square planar geometries.
187:
The Δ splitting energy for tetrahedral metal complexes (four ligands), Δ
166:
Light-induced spin-crossover of , which switches from high and low-spin.
637:
1004:
800:
441:
Octahedral high spin: Co ionic radius 74.5 pm, Ni ionic radius 60 pm.
403:
175:
159:, where the high and low spin states exist in dynamic equilibrium.
444:
Octahedral low spin: Co ionic radius 65 pm, Niionic radius 56 pm.
395:. For a given d-electron count, high-spin complexes are larger.
623:
510:
GĂĽtlich, P. (2001). "Photoswitchable
Coordination Compounds".
225:
162:
250:
All complexes of second and third row metals are low-spin.
948:
Arene complexes of univalent gallium, indium, and thallium
316:, substitutionally labile. Includes Fe, Co. Examples: , .
323:, substitutionally inert. Includes Fe, Co, Ni. Example:
141:
Ligands also affect the magnitude of Δ splitting of the
484:
419:
Octahedral high spin: Fe, the ionic radius is 64.5 pm.
347:, substitutionally labile. Includes Co, Ni. Example: .
148:
according to their field strength as described by the
288:, substitutionally labile. Includes Fe, Mn. Example:
183:
is a rare example of a low-spin tetrahedral complex.
585:
Batsanov, Andrei S.; Howard, Judith A. K. (2001). "
422:
Octahedral low spin: Fe, the ionic radius is 55 pm.
119:orbitals before any pairing occurs in accord with
369:, substitutionally labile. Includes Ni. Example:
359:, substitutionally labile. Includes Ni. Example:
299:, substitutionally inert. Includes Fe. Example:
241:
1035:
391:The spin state of the complex affects an atom's
379:, substitutionally inert. Includes Ni. Example:
375:Square planar low-spin: no unpaired electrons,
584:
455:Square planar low-spin: Ni ionic radius 49 pm.
731:
685:
365:Tetrahedral high-spin: 2 unpaired electrons,
745:
658:
557:
452:Octahedral high spin: Ni ionic radius 69 pm.
355:Octahedral high-spin: 2 unpaired electrons,
336:Octahedral high-spin: 3 unpaired electrons,
319:Octahedral low-spin: no unpaired electrons,
312:Octahedral high-spin: 4 unpaired electrons,
284:Octahedral high-spin: 5 unpaired electrons,
259:Octahedral high-spin: 4 unpaired electrons,
340:, substitutionally labile. Includes Co, Ni.
270:Octahedral low-spin: 2 unpaired electrons,
226:Ligand field theory vs crystal field theory
832:Oxidative addition / reductive elimination
738:
724:
485:Miessler, Gary L.; Donald A. Tarr (1998).
295:Octahedral low-spin: 1 unpaired electron,
274:, substitutionally inert. Includes Cr, Mn.
213:
343:Octahedral low-spin:1 unpaired electron,
220:dichlorobis(triphenylphosphine)nickel(II)
50:
781:Polyhedral skeletal electron pair theory
560:Journal of the American Chemical Society
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174:
170:
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125:
65:
532:
509:
61:
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719:
888:Transition metal fullerene complexes
13:
923:Transition metal carbyne complexes
918:Transition metal carbene complexes
883:Transition metal indenyl complexes
551:
155:Some octahedral complexes exhibit
43:(a more advanced version based on
14:
1060:
933:Transition metal alkyne complexes
928:Transition metal alkene complexes
230:In terms of d-orbital splitting,
108:, Δ, high spin splitting occurs.
938:Transition-metal allyl complexes
913:Transition metal acyl complexes
409:Octahedral low spin: Mn, 58 pm.
402:Octahedral high spin: Cr, 64.5
679:
652:
617:
578:
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512:Coordination Chemistry Reviews
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478:
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290:Tris(acetylacetonato)iron(III)
242:High-spin and low-spin systems
1:
520:10.1016/S0010-8545(01)00381-2
471:
7:
989:Shell higher olefin process
796:Dewar–Chatt–Duncanson model
10:
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878:Cyclopentadienyl complexes
842:β-hydride elimination
816:Metal–ligand multiple bond
54:
1002:
956:
943:Transition metal carbides
860:
824:
753:
673:10.1107/S0567739476001551
603:10.1107/S1600536801008741
537:. Cengage Learning, Inc.
747:Organometallic chemistry
696:10.1002/bbpc.19920960429
45:molecular orbital theory
908:Half sandwich compounds
214:Square planar complexes
1044:Coordination chemistry
1023:Bioinorganic chemistry
686:R. G. Wilkins (1991).
661:Acta Crystallographica
184:
167:
150:spectrochemical series
134:
91:spectrochemical series
74:
51:High-spin vs. low-spin
24:coordination complexes
994:Ziegler–Natta process
898:Metal tetranorbornyls
460:Ligand exchange rates
178:
171:Tetrahedral complexes
165:
133:crystal field diagram
129:
73:crystal field diagram
69:
1003:Related branches of
761:Crystal field theory
514:. 219–221: 839–879.
236:crystal field theory
62:Octahedral complexes
37:crystal field theory
1018:Inorganic chemistry
837:Migratory insertion
811:Agostic interaction
766:Ligand field theory
626:Inorganic Chemistry
572:10.1021/ja00762a056
535:Chemical Principles
487:Inorganic Chemistry
232:ligand field theory
41:ligand field theory
903:Sandwich compounds
861:Types of compounds
786:Isolobal principle
591:Acta Crystallogr E
185:
168:
135:
75:
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1030:
1013:Organic chemistry
984:Olefin metathesis
974:Grignard reaction
873:Grignard reagents
690:. Weinheim: VCH.
638:10.1021/ic300882r
632:(12): 6969–6982.
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979:Monsanto process
776:d electron count
771:18-electron rule
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566:(7): 2512–2514.
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197:nitrosyl complex
113:Aufbau principle
57:Magnetochemistry
21:transition metal
19:when describing
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1049:Electron states
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868:Gilman reagents
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852:Carbometalation
847:Transmetalation
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667:(5): 751–767.
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964:Carbonylation
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957:Applications
893:Metallocenes
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393:ionic radius
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367:paramagnetic
357:paramagnetic
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338:paramagnetic
314:paramagnetic
297:paramagnetic
286:paramagnetic
272:paramagnetic
261:paramagnetic
249:
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195:, , and the
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31:
27:
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806:spin states
597:: 308–309.
387:Ionic radii
377:diamagnetic
321:diamagnetic
121:Hund's rule
79:Δ splitting
17:Spin states
1038:Categories
754:Principles
472:References
234:(LFT) and
1005:chemistry
825:Reactions
801:Hapticity
131:High-spin
28:high-spin
646:22676275
611:97381117
146:orbitals
86:orbitals
71:Low-spin
32:low-spin
201:(N(tms)
199:Cr(NO)(
81:of the
702:
644:
609:
541:
493:
267:), Mn.
607:S2CID
587:trans
700:ISBN
642:PMID
539:ISBN
491:ISBN
77:The
39:and
30:and
692:doi
669:doi
665:A32
634:doi
599:doi
568:doi
516:doi
189:tet
47:).
1040::
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630:51
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593:.
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404:pm
210:.
739:e
732:t
725:v
708:.
694::
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466:g
449:d
438:d
427:d
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352:d
331:d
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307:d
302:.
292:.
279:d
254:d
207:3
205:)
203:2
193:4
181:4
144:d
117:d
105:g
99:g
84:d
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
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