234:. Increasing the bond order to two by involving another lone pair changes the hybridization at the oxygen to an sp center with an expected expansion in the M-O-R bond angle and contraction in the M-O bond length. If all three lone pairs are included for a bond order of three than the M-O bond distance contracts further and since the oxygen is a sp center the M-O-R bond angle is 180˚ or linear. Similarly with the imidos are commonly referred to as either bent (sp) or linear (sp). Even the oxo can be sp or sp hybridized. The triply bonded oxo, similar to
260:
including the most common linear imidos with a six electron bonding interaction to the metal center. Similarly amido complexes are usually drawn with a single line even though most amido bonds involve four electrons. Alkoxides are generally drawn with a single bond although both two and four electron bonds are common. Oxo can be drawn with two lines regardless of whether four electrons or six are involved in the bond, although it is not uncommon to see six electron oxo bonds represented with three lines.
945:
68:
269:
oxidation state becomes more of a formalism with much of the positive charge distributed between the ligands. This distinction can be expressed by using a Roman numeral for the lower oxidation states in the upper right of the metal atomic symbol and an Arabic number with a plus sign for the higher oxidation states (see the example below). This formalism is not rigorously followed and the use of Roman numerals to represent higher oxidation states is common.
939:
951:
259:
Imido ligands, also known as imides or nitrenes, most commonly form "linear six electron bonds" with metal centers. Bent imidos are a rarity limited by complexes electron count, orbital bonding availability, or some similar phenomenon. It is common to draw only two lines of bonding for all imidos,
268:
There are two motifs to indicate a metal oxidation state based around the actual charge separation of the metal center. Oxidation states up to +3 are believed to be an accurate representation of the charge separation experienced by the metal center. For oxidation states of +4 and larger, the
225:
A ligand described in ionic terms can bond to a metal through however many lone pairs it has available. For example, many alkoxides use one of their three lone pairs to make a single bond to a metal center. In this situation the oxygen is sp
81:
is a formalism. Furthermore, the usage of multiple bonding is not uniform. Symmetry arguments suggest that most ligands engage metals via multiple bonds. The term 'metal–ligand multiple bond" is often reserved for ligands of the type
165:
N), and fluoride. For late transition metals, strong pi-donors form anti-bonding interactions with the filled d-levels, with consequences for spin state, redox potentials, and ligand exchange rates. Pi-donor ligands are low in the
293:"Metal–Ligand Multiple Bonds: The Chemistry of Transition Metal Complexes Containing Oxo, Nitrido, Imido, Alkylidene, or Alkylidyne Ligands" W. A. Nugent and J. M. Mayer; Wiley-Interscience, New York, 1988.
401:
Aliaga-Alcalde, N.; George, S.D.; Mienert, B.; Bill, E.; Wieghardt, K.; Neese, F. "The
Geometric and Electronic Structure of : A Genuine Iron(V) Species with a Ground-State Spin S=1/2"
341:
Rohde,J; In,J.; Lim, M.H.; Brennessel, W.W.; Bukowski, M.R.; Stubna, A.; Muonck, E.; Nam, W.; Que L. "Crystallographic and
Spectroscopic Characterization of a Nonheme Fe(IV)O Complex"
153:, a pi-donor ligand is a kind of ligand endowed with filled non-bonding orbitals that overlap with metal-based orbitals. Their interaction is complementary to the behavior of
656:
161:
for the early transition metals is one consequence of this kind of bonding. Classic pi-donor ligands are oxide (O), nitride (N), imide (RN), alkoxide (RO), amide (R
318:; Johnson, A.M. "Experimental and Crystal Field Study of the Absorption Spectrum at 2000 to 8000 A of to Manganous Perchlorate in Aqueous Perchloric Acid"
1038:
77:
As a cautionary note, the classification of a metal–ligand bond as being "multiple" bond order is ambiguous and even arbitrary because
17:
446:
1156:
1083:
764:
489:
213:
allow for many bonds between ligands and the metal center. A d metal center can accommodate up to 9 bonds without violating the
1078:
504:
378:"Spectroscopic and Quantum Chemical Characterization of the Electronic Structure and Bonding in a Non-Heme FeO Complex"
596:
1003:
631:
626:
591:
55:
1187:
827:
641:
636:
621:
1018:
815:
805:
646:
298:
810:
439:
757:
697:
702:
1182:
1073:
1063:
1053:
1028:
998:
514:
844:
586:
550:
455:
432:
31:
1105:
1008:
980:
750:
246:
at which point the oxygen no longer bears a partial positive charge and is reactive toward acid.
731:
616:
205:) ligands are generally assigned to high oxidation states with low d electron counts. The high
167:
150:
1149:
1110:
651:
227:
194:
1144:
1068:
959:
822:
781:
606:
469:
51:
242:
at the oxygen atom. When such a complex is reduced, the triple bond can be converted to a
8:
970:
834:
800:
726:
545:
519:
474:
231:
1134:
889:
540:
494:
365:
154:
1120:
909:
869:
859:
721:
692:
682:
611:
403:
380:
375:
351:
343:
320:
294:
67:
59:
1161:
901:
874:
687:
581:
484:
479:
415:
392:
358:
332:
315:
214:
210:
362:
239:
1139:
1013:
884:
560:
555:
235:
206:
54:
featuring multiply bonded ligands are of both scholarly and practical interest.
1048:
849:
677:
576:
499:
1176:
1097:
1057:
990:
944:
919:
792:
773:
672:
1043:
424:
419:
355:
202:
119:
1129:
879:
601:
243:
179:
336:
62:
reaction. Metal oxo intermediates are pervasive in oxidation catalysis.
369:
158:
78:
47:
27:
Chemical interaction of certain ligands with metals of bond order >1
396:
864:
839:
713:
509:
220:
71:
Most common classes of complexes showing metal–ligand multiple bonds
938:
742:
238:, is partially positive at the oxygen atom and unreactive toward
190:
182:
138:
39:
198:
186:
43:
308:
950:
657:
Arene complexes of univalent gallium, indium, and thallium
118:(n = 0, 1) where R is H or an organic substituent, or
217:, whereas a d species can only accommodate 6 bonds.
221:Reactivity explained through ligand hybridization
137:are not included in this classification, nor are
1174:
263:
209:stabilizes the highly reduced ligands. The low
173:
758:
440:
454:
765:
751:
541:Oxidative addition / reductive elimination
447:
433:
254:
1157:Polyhedral skeletal electron pair theory
490:Polyhedral skeletal electron pair theory
309:Further reading (specialized literature)
66:
289:
287:
14:
1175:
746:
428:
38:describes the interaction of certain
597:Transition metal fullerene complexes
284:
144:
24:
772:
632:Transition metal carbyne complexes
627:Transition metal carbene complexes
592:Transition metal indenyl complexes
56:transition metal carbene complexes
25:
1199:
642:Transition metal alkyne complexes
637:Transition metal alkene complexes
949:
943:
937:
647:Transition-metal allyl complexes
622:Transition metal acyl complexes
374:Decker, A.; Rohde,J.; Que, L.;
249:
13:
1:
363:10.1126/science.299.5609.1037
277:
264:Representing oxidation states
157:. The existence of terminal
7:
698:Shell higher olefin process
505:Dewar–Chatt–Duncanson model
174:Multiple bond stabilization
10:
1204:
855:Metal–ligand multiple bond
587:Cyclopentadienyl complexes
551:β-hydride elimination
525:Metal–ligand multiple bond
178:Metals bound to so-called
36:metal–ligand multiple bond
18:Metal ligand multiple bond
1119:
1096:
1027:
989:
969:
958:
935:
918:
900:
791:
780:
711:
665:
652:Transition metal carbides
569:
533:
462:
456:Organometallic chemistry
32:organometallic chemistry
617:Half sandwich compounds
255:Bonding representations
1188:Coordination chemistry
732:Bioinorganic chemistry
420:10.1002/anie.200462368
168:spectrochemical series
151:coordination chemistry
72:
52:Coordination complexes
703:Ziegler–Natta process
607:Metal tetranorbornyls
404:Angew. Chem. Int. Ed.
70:
845:Coordinate (dipolar)
712:Related branches of
470:Crystal field theory
1019:C–H···O interaction
801:Electron deficiency
727:Inorganic chemistry
546:Migratory insertion
520:Agostic interaction
475:Ligand field theory
337:10.1021/ja01557a001
232:valence bond theory
155:pi-acceptor ligands
1004:Resonance-assisted
612:Sandwich compounds
570:Types of compounds
495:Isolobal principle
106:(n = 0, 1, 2) and
73:
50:greater than one.
1170:
1169:
1121:Electron counting
1092:
1091:
981:London dispersion
933:
932:
910:Metal aromaticity
740:
739:
722:Organic chemistry
693:Olefin metathesis
683:Grignard reaction
582:Grignard reagents
397:10.1021/ja0498033
381:J. Am. Chem. Soc.
321:J. Am. Chem. Soc.
60:olefin metathesis
16:(Redirected from
1195:
1183:Chemical bonding
1162:Jemmis mno rules
1014:Dihydrogen bonds
967:
966:
953:
947:
941:
875:Hyperconjugation
789:
788:
767:
760:
753:
744:
743:
688:Monsanto process
485:d electron count
480:18-electron rule
449:
442:
435:
426:
425:
302:
291:
215:18 electron rule
211:d electron count
145:Pi-donor ligands
136:
135:
134:
125:
122:. Historically,
117:
116:
115:
105:
104:
103:
93:
92:
91:
21:
1203:
1202:
1198:
1197:
1196:
1194:
1193:
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1173:
1172:
1171:
1166:
1115:
1088:
1031:
1023:
985:
972:
962:
954:
948:
942:
929:
914:
896:
784:
776:
771:
741:
736:
707:
661:
577:Gilman reagents
565:
561:Carbometalation
556:Transmetalation
529:
458:
453:
311:
306:
305:
292:
285:
280:
266:
257:
252:
236:carbon monoxide
223:
207:oxidation state
176:
164:
147:
133:
131:
130:
129:
127:
123:
114:
111:
110:
109:
107:
102:
99:
98:
97:
95:
90:
87:
86:
85:
83:
28:
23:
22:
15:
12:
11:
5:
1201:
1191:
1190:
1185:
1168:
1167:
1165:
1164:
1159:
1154:
1153:
1152:
1147:
1142:
1137:
1126:
1124:
1117:
1116:
1114:
1113:
1108:
1102:
1100:
1094:
1093:
1090:
1089:
1087:
1086:
1081:
1076:
1071:
1066:
1061:
1051:
1046:
1041:
1035:
1033:
1025:
1024:
1022:
1021:
1016:
1011:
1006:
1001:
995:
993:
987:
986:
984:
983:
977:
975:
964:
960:Intermolecular
956:
955:
936:
934:
931:
930:
928:
927:
924:
922:
916:
915:
913:
912:
906:
904:
898:
897:
895:
894:
893:
892:
887:
877:
872:
867:
862:
857:
852:
847:
842:
837:
832:
831:
830:
820:
819:
818:
813:
808:
797:
795:
786:
782:Intramolecular
778:
777:
774:Chemical bonds
770:
769:
762:
755:
747:
738:
737:
735:
734:
729:
724:
718:
716:
709:
708:
706:
705:
700:
695:
690:
685:
680:
678:Cativa process
675:
669:
667:
663:
662:
660:
659:
654:
649:
644:
639:
634:
629:
624:
619:
614:
609:
604:
599:
594:
589:
584:
579:
573:
571:
567:
566:
564:
563:
558:
553:
548:
543:
537:
535:
531:
530:
528:
527:
522:
517:
512:
507:
502:
497:
492:
487:
482:
477:
472:
466:
464:
460:
459:
452:
451:
444:
437:
429:
423:
422:
399:
372:
339:
310:
307:
304:
303:
282:
281:
279:
276:
275:
274:
265:
262:
256:
253:
251:
248:
240:Brønsted acids
222:
219:
175:
172:
162:
146:
143:
132:
112:
100:
88:
75:
74:
26:
9:
6:
4:
3:
2:
1200:
1189:
1186:
1184:
1181:
1180:
1178:
1163:
1160:
1158:
1155:
1151:
1148:
1146:
1143:
1141:
1138:
1136:
1135:Hückel's rule
1133:
1132:
1131:
1128:
1127:
1125:
1122:
1118:
1112:
1109:
1107:
1104:
1103:
1101:
1099:
1098:Bond cleavage
1095:
1085:
1082:
1080:
1077:
1075:
1072:
1070:
1067:
1065:
1064:Intercalation
1062:
1059:
1055:
1054:Metallophilic
1052:
1050:
1047:
1045:
1042:
1040:
1037:
1036:
1034:
1030:
1026:
1020:
1017:
1015:
1012:
1010:
1007:
1005:
1002:
1000:
997:
996:
994:
992:
988:
982:
979:
978:
976:
974:
971:Van der Waals
968:
965:
961:
957:
952:
946:
940:
926:
925:
923:
921:
917:
911:
908:
907:
905:
903:
899:
891:
888:
886:
883:
882:
881:
878:
876:
873:
871:
868:
866:
863:
861:
858:
856:
853:
851:
848:
846:
843:
841:
838:
836:
833:
829:
826:
825:
824:
821:
817:
814:
812:
809:
807:
804:
803:
802:
799:
798:
796:
794:
790:
787:
783:
779:
775:
768:
763:
761:
756:
754:
749:
748:
745:
733:
730:
728:
725:
723:
720:
719:
717:
715:
710:
704:
701:
699:
696:
694:
691:
689:
686:
684:
681:
679:
676:
674:
673:Carbonylation
671:
670:
668:
664:
658:
655:
653:
650:
648:
645:
643:
640:
638:
635:
633:
630:
628:
625:
623:
620:
618:
615:
613:
610:
608:
605:
603:
600:
598:
595:
593:
590:
588:
585:
583:
580:
578:
575:
574:
572:
568:
562:
559:
557:
554:
552:
549:
547:
544:
542:
539:
538:
536:
532:
526:
523:
521:
518:
516:
513:
511:
508:
506:
503:
501:
500:π backbonding
498:
496:
493:
491:
488:
486:
483:
481:
478:
476:
473:
471:
468:
467:
465:
461:
457:
450:
445:
443:
438:
436:
431:
430:
427:
421:
417:
414:, 2908–2912.
413:
409:
406:
405:
400:
398:
394:
391:, 5378–5379.
390:
386:
383:
382:
377:
376:Solomon, E.I.
373:
371:
367:
364:
360:
357:
353:
349:
346:
345:
340:
338:
334:
331:, 6471–6477.
330:
326:
323:
322:
317:
314:Heidt, L.J.;
313:
312:
300:
296:
290:
288:
283:
272:
271:
270:
261:
247:
245:
241:
237:
233:
230:according to
229:
218:
216:
212:
208:
204:
200:
196:
192:
188:
184:
181:
180:triply bonded
171:
169:
160:
156:
152:
142:
140:
121:
80:
69:
65:
64:
63:
61:
58:catalyze the
57:
53:
49:
45:
41:
37:
33:
19:
1140:Baird's rule
860:Charge-shift
854:
823:Hypervalence
666:Applications
602:Metallocenes
524:
411:
407:
402:
388:
384:
379:
347:
342:
328:
324:
319:
316:Koster, G.F.
267:
258:
224:
177:
148:
120:pseudohalide
76:
35:
29:
1130:Aromaticity
1106:Heterolysis
1084:Salt bridge
1029:Noncovalent
999:Low-barrier
880:Aromaticity
870:Conjugation
850:Pi backbond
515:spin states
350:1037–1039.
250:Conventions
244:double bond
159:oxo ligands
1177:Categories
1058:aurophilic
1039:Mechanical
463:Principles
299:0471854409
278:References
228:hybridized
79:bond order
48:bond order
1150:spherical
1111:Homolysis
1074:Cation–pi
1049:Chalcogen
1009:Symmetric
865:Hapticity
714:chemistry
534:Reactions
510:Hapticity
1079:Anion–pi
1069:Stacking
991:Hydrogen
902:Metallic
793:Covalent
785:(strong)
356:12586936
1044:Halogen
890:bicyclo
835:Agostic
370:3833551
348:VOL 299
344:Science
197:), and
195:nitrido
191:nitride
183:carbyne
139:halides
46:with a
42:with a
40:ligands
1145:Möbius
973:forces
963:(weak)
368:
354:
297:
1123:rules
1032:other
920:Ionic
828:3c–4e
816:8c–2e
811:4c–2e
806:3c–2e
366:JSTOR
199:oxide
187:imide
44:metal
885:homo
840:Bent
408:2005
385:2004
352:PMID
325:1959
295:ISBN
273:vs.
126:and
94:and
34:, a
416:doi
393:doi
389:126
359:doi
333:doi
203:oxo
149:In
30:In
1179::
412:44
410:,
387:,
329:80
327:,
286:^
189:,
185:,
170:.
141:.
128:NO
124:CO
108:OR
96:NR
84:CR
1060:)
1056:(
766:e
759:t
752:v
448:e
441:t
434:v
418::
395::
361::
335::
301:.
201:(
193:(
163:2
113:n
101:n
89:n
20:)
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
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