266:
254:
1013:
107:
115:
1007:
205:
197:
1019:
278:
lengthening of the P–C distance is often hidden by an opposing effect: as the phosphorus lone pair is donated to the metal, P(lone pair)–R(bonding pair) repulsions decrease, which acts to shorten the P–C bond. The two effects have been deconvoluted by comparing the structures of pairs of metal-phosphine complexes that differ only by one electron. Oxidation of R
212:
As in metal–carbonyls, electrons are partially transferred from a d-orbital of the metal to antibonding molecular orbitals of the alkenes and alkynes. This electron transfer strengthens the metal–ligand bond and weakens the C–C bonds within the ligand. In the case of metal-alkenes and alkynes, the
122:
The electrons are partially transferred from a d-orbital of the metal to anti-bonding molecular orbitals of CO (and its analogs). This electron-transfer strengthens the metal–C bond and weakens the C–O bond. The strengthening of the M–CO bond is reflected in increases of the vibrational frequencies
277:
Phosphines accept electron density from metal p or d orbitals into combinations of P–C σ* antibonding orbitals that have π symmetry. When phosphines bond to electron-rich metal atoms, backbonding would be expected to lengthen P–C bonds as P–C σ* orbitals become populated by electrons. The expected
180:
can either be raised (for example, upon complexation with weak π-donor metals, such as Pt(II)) or lowered (for example, upon complexation with strong π-donor metals, such as Ni(0)). For the isocyanides, an additional parameter is the MC=N–C angle, which deviates from 180° in highly electron-rich
282:
P–M complexes results in longer M–P bonds and shorter P–C bonds, consistent with π-backbonding. In early work, phosphine ligands were thought to utilize 3d orbitals to form M–P pi-bonding, but it is now accepted that d-orbitals on phosphorus are not involved in bonding as they are too high in
165:, RNC, are another class of ligands that are capable of π-backbonding. In contrast with CO, the σ-donor lone pair on the C atom of isocyanides is antibonding in nature and upon complexation the CN bond is strengthened and the ν
303:
process with donation of electrons from the filled π-orbital or lone electron pair orbital of the ligand into an empty orbital of the metal (donor–acceptor bond), together with release (back donation) of electrons from an
123:
for the M–C bond (often outside of the range for the usual IR spectrophotometers). Furthermore, the M–CO bond length is shortened. The weakening of the C–O bond is indicated by a decrease in the wavenumber of the
753:
Fey, N.; Orpen, A. G.; Harvey, J. N. (2009). "Building ligand knowledge bases for organometallic chemistry: Computational description of phosphorus(III)-donor ligands and the metal–phosphorus bonds".
694:
Dunne, B. J.; Morris, R. B.; Orpen, A. G. (1991). "Structural systematics. Part 3. Geometry deformations in triphenylphosphine fragments: A test of bonding theories in phosphine complexes".
233:
to assume the character of a metallacyclopropane. Alkenes and alkynes with electronegative substituents exhibit greater π backbonding. Some strong π backbonding ligands are
1472:
95:
717:
Gilheany, D. G. (1994). "No d
Orbitals but Walsh Diagrams and Maybe Banana Bonds: Chemical Bonding in Phosphines, Phosphine Oxides, and Phosphonium Ylides".
229:
bond is reflected in bending of the C–C–R angles which assume greater sp and sp character, respectively. Thus strong π backbonding causes a metal-alkene
633:
Orpen, A. G.; Connelly, N. G. (1990). "Structural systematics: the role of P–A σ* orbitals in metal–phosphorus π-bonding in redox-related pairs of M–PA
1106:
1262:
1305:
1224:
1151:
832:
147:
342:
181:
systems. Other ligands have weak π-backbonding abilities, which creates a labilization effect of CO, which is described by the
798:
678:
592:
525:
500:
425:
400:
373:
450:
1320:
1146:
327:
1412:
617:
475:
1578:
1447:
1442:
1407:
1071:
1573:
1457:
1452:
1437:
895:
1086:
1462:
1340:
922:
883:
873:
755:
153:
Many ligands other than CO are strong "backbonders". Nitric oxide is an even stronger π-acceptor than CO and ν
39:
on an adjacent ion or molecule. In this type of interaction, electrons from the metal are used to bond to the
1255:
878:
825:
1513:
308:
d orbital of the metal (which is of π-symmetry with respect to the metal–ligand axis) into the empty π*-
1518:
542:
1568:
1330:
1141:
1131:
1121:
1096:
1066:
1402:
1366:
1271:
1248:
912:
1173:
1076:
1048:
818:
1547:
1432:
158:
1467:
1217:
1178:
1212:
299:
A description of the bonding of π-conjugated ligands to a transition metal which involves a
1422:
1285:
1136:
1027:
890:
849:
230:
8:
1542:
1361:
1335:
1290:
1038:
902:
868:
337:
242:
234:
1202:
1356:
1310:
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666:
238:
265:
1537:
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969:
942:
786:
763:
727:
719:
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648:
554:
332:
130:
band(s) from that for free CO (2143 cm), for example to 2060 cm in Ni(CO)
48:
1376:
1371:
1207:
1081:
952:
639:
139:
91:
84:
44:
1493:
1392:
1116:
143:
68:
36:
32:
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558:
1562:
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1125:
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389:
Cotton, Frank Albert; Wilkinson, Geoffrey; Murillo, Carlos A., eds. (1999).
1240:
1111:
739:
390:
363:
1417:
1197:
947:
703:
309:
731:
652:
208:π backbonding from electrons in metal center d-orbital to alkene's LUMO.
204:
182:
162:
80:
196:
106:
1529:
1325:
932:
907:
790:
368:(2nd ed.). Upper Saddle River, N.J: Prentice Hall. p. 338.
60:
52:
20:
783:
IUPAC. Compendium of
Chemical Terminology, 2nd ed. (the "Gold Book")
610:
468:
200:σ bonding from electrons in alkene's HOMO to metal center d-orbital.
118:π backbonding from electrons in metal center d-orbital to CO's LUMO.
1006:
176:. Depending on the balance of σ-bonding versus π-backbonding, the ν
114:
810:
300:
56:
28:
110:σ bonding from electrons in CO's HOMO to metal center d-orbital.
76:
72:
64:
40:
520:(3., compl. rev. and extended ed.). Weinheim: WILEY-VCH.
101:
541:
Zhao, Haitao; Ariafard, Alireza; Lin, Zhenyang (2006-08-01).
292:
585:
Organotransition metal chemistry: from bonding to catalysis
516:
Elschenbroich, Christoph; Elschenbroich, Christoph (2011).
493:
Organotransition metal chemistry: from bonding to catalysis
67:
involved in π backbonding can be broken into three groups:
1473:
Arene complexes of univalent gallium, indium, and thallium
1018:
515:
191:
543:"In-depth insight into metal–alkene bonding interactions"
549:. Protagonists in Chemistry: Professor D.M.P. Mingos.
388:
169:
increased. At the same time, π-backbonding lowers the
671:
443:
83:. Compounds where π backbonding is prominent include
696:
Journal of the
Chemical Society, Dalton Transactions
420:(2nd ed.). Pearson Prentice-Hall. p. 702.
286:
51:
with low oxidation states that have ligands such as
138:, and 1790 cm in the anion . For this reason,
780:
1560:
693:
587:. Sausalito (Calif.): University science books.
495:. Sausalito (Calif.): University science books.
415:
540:
752:
608:Elias, Anil J.; Gupta, B D (January 1, 2013).
466:Elias, Anil J.; Gupta, B D (January 1, 2013).
31:interaction between a filled (or half filled)
1256:
826:
785:. Oxford: Blackwell Scientific Publications.
632:
1270:
361:
248:
362:Miessler, Gary L.; Tarr, Donald A. (1999).
295:definition of back donation is as follows:
102:Metal carbonyls, nitrosyls, and isocyanides
1357:Oxidative addition / reductive elimination
1263:
1249:
833:
819:
607:
465:
47:and stabilizes the metal. It is common in
445:(6th ed.). Wiley. pp. 105–106.
416:Housecroft, C. E.; Sharpe, A. G. (2005).
1306:Polyhedral skeletal electron pair theory
1225:Polyhedral skeletal electron pair theory
716:
673:(5th ed.). Wiley. pp. 99–100.
665:
440:
264:
252:
203:
195:
148:infrared spectroscopy of metal carbonyls
142:is an important diagnostic technique in
113:
105:
96:molybdenum and iron dinitrogen complexes
35:of a transition metal atom and a vacant
781:McNaught, A. D.; Wilkinson, A. (2006).
637:complexes (A = R, Ar, OR; R = alkyl)".
582:
490:
192:Metal–alkene and metal–alkyne complexes
1561:
1244:
814:
578:
576:
16:Form of interaction between two atoms
1413:Transition metal fullerene complexes
612:(2nd ed.). Universities Press.
470:(2nd ed.). Universities Press.
601:
43:, which dissipates excess negative
13:
1448:Transition metal carbyne complexes
1443:Transition metal carbene complexes
1408:Transition metal indenyl complexes
840:
573:
14:
1590:
1458:Transition metal alkyne complexes
1453:Transition metal alkene complexes
484:
459:
395:(6th ed.). New York: Wiley.
287:IUPAC definition of Back Donation
1463:Transition-metal allyl complexes
1017:
1011:
1005:
583:Hartwig, John Frederick (2010).
491:Hartwig, John Frederick (2010).
1438:Transition metal acyl complexes
774:
746:
710:
687:
659:
626:
534:
509:
434:
409:
382:
355:
1:
348:
441:Crabtree, Robert H. (2014).
392:Advanced inorganic chemistry
7:
1514:Shell higher olefin process
1321:Dewar–Chatt–Duncanson model
328:Dewar–Chatt–Duncanson model
316:
10:
1595:
1403:Cyclopentadienyl complexes
1367:β-hydride elimination
1341:Metal–ligand multiple bond
923:Metal–ligand multiple bond
150:discusses this in detail.
134:and 1981 cm in Cr(CO)
1527:
1481:
1468:Transition metal carbides
1385:
1349:
1278:
1187:
1164:
1095:
1057:
1037:
1026:
1003:
986:
968:
859:
848:
768:10.1016/j.ccr.2008.04.017
559:10.1016/j.ica.2005.12.013
249:Metal-phosphine complexes
1579:Organometallic chemistry
1272:Organometallic chemistry
213:strengthening of the M–C
159:metal–nitrosyl chemistry
157:is a diagnostic tool in
144:metal–carbonyl chemistry
1433:Half sandwich compounds
547:Inorganica Chimica Acta
1574:Coordination chemistry
1548:Bioinorganic chemistry
314:
312:orbital of the ligand.
274:
262:
209:
201:
119:
111:
71:and nitrogen analogs,
1519:Ziegler–Natta process
1423:Metal tetranorbornyls
297:
268:
256:
207:
199:
117:
109:
1528:Related branches of
1286:Crystal field theory
913:Coordinate (dipolar)
704:10.1039/dt9910000653
1543:Inorganic chemistry
1362:Migratory insertion
1336:Agostic interaction
1291:Ligand field theory
1087:C–H···O interaction
869:Electron deficiency
732:10.1021/cr00029a008
667:Crabtree, Robert H.
653:10.1021/om00118a048
418:Inorganic Chemistry
365:Inorganic chemistry
338:Ligand field theory
243:hexafluoro-2-butyne
235:tetrafluoroethylene
1428:Sandwich compounds
1386:Types of compounds
1311:Isolobal principle
1072:Resonance-assisted
275:
263:
239:tetracyanoethylene
210:
202:
120:
112:
1556:
1555:
1538:Organic chemistry
1509:Olefin metathesis
1499:Grignard reaction
1398:Grignard reagents
1238:
1237:
1189:Electron counting
1160:
1159:
1049:London dispersion
1001:
1000:
978:Metal aromaticity
800:978-0-9678550-9-7
756:Coord. Chem. Rev.
680:978-0-470-25762-3
594:978-1-891389-53-5
553:(11): 3527–3534.
527:978-3-527-29390-2
502:978-1-891389-53-5
427:978-0-130-39913-7
402:978-0-471-19957-1
375:978-0-13-841891-5
323:Bridging carbonyl
273:P–M π backbonding
49:transition metals
1586:
1569:Chemical bonding
1504:Monsanto process
1301:d electron count
1296:18-electron rule
1265:
1258:
1251:
1242:
1241:
1230:Jemmis mno rules
1082:Dihydrogen bonds
1035:
1034:
1021:
1015:
1009:
943:Hyperconjugation
857:
856:
835:
828:
821:
812:
811:
805:
804:
791:10.1351/goldbook
778:
772:
771:
762:(5–6): 704–722.
750:
744:
743:
726:(5): 1339–1374.
714:
708:
707:
691:
685:
684:
663:
657:
656:
647:(4): 1206–1210.
630:
624:
623:
605:
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580:
571:
570:
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531:
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488:
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481:
463:
457:
456:
452:978-1-11813807-6
438:
432:
431:
413:
407:
406:
386:
380:
379:
359:
343:Pi-donor ligands
333:18-electron rule
1594:
1593:
1589:
1588:
1587:
1585:
1584:
1583:
1559:
1558:
1557:
1552:
1523:
1477:
1393:Gilman reagents
1381:
1377:Carbometalation
1372:Transmetalation
1345:
1274:
1269:
1239:
1234:
1183:
1156:
1099:
1091:
1053:
1040:
1030:
1022:
1016:
1010:
997:
982:
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839:
809:
808:
801:
779:
775:
751:
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688:
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664:
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640:Organometallics
636:
631:
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518:Organometallics
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140:IR spectroscopy
137:
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104:
88:
53:carbon monoxide
17:
12:
11:
5:
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1582:
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1534:
1532:
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1511:
1506:
1501:
1496:
1494:Cativa process
1491:
1485:
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1268:
1267:
1260:
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1245:
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1235:
1233:
1232:
1227:
1222:
1221:
1220:
1215:
1210:
1205:
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1192:
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1184:
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1168:
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1154:
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1139:
1134:
1129:
1119:
1114:
1109:
1103:
1101:
1093:
1092:
1090:
1089:
1084:
1079:
1074:
1069:
1063:
1061:
1055:
1054:
1052:
1051:
1045:
1043:
1032:
1028:Intermolecular
1024:
1023:
1004:
1002:
999:
998:
996:
995:
992:
990:
984:
983:
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980:
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905:
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886:
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876:
865:
863:
854:
850:Intramolecular
846:
845:
842:Chemical bonds
838:
837:
830:
823:
815:
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806:
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745:
709:
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625:
619:978-8173718748
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477:978-8173718748
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146:. The article
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9:
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3:
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1500:
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1492:
1490:
1489:Carbonylation
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1486:
1484:
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1474:
1471:
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1454:
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1360:
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1354:
1352:
1348:
1342:
1339:
1337:
1334:
1332:
1329:
1327:
1324:
1322:
1319:
1317:
1316:π backbonding
1314:
1312:
1309:
1307:
1304:
1302:
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1231:
1228:
1226:
1223:
1219:
1216:
1214:
1211:
1209:
1206:
1204:
1203:Hückel's rule
1201:
1200:
1199:
1196:
1195:
1193:
1190:
1186:
1180:
1177:
1175:
1172:
1171:
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1167:
1166:Bond cleavage
1163:
1153:
1150:
1148:
1145:
1143:
1140:
1138:
1135:
1133:
1132:Intercalation
1130:
1127:
1123:
1122:Metallophilic
1120:
1118:
1115:
1113:
1110:
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1102:
1098:
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1070:
1068:
1065:
1064:
1062:
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1056:
1050:
1047:
1046:
1044:
1042:
1039:Van der Waals
1036:
1033:
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1020:
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1008:
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993:
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989:
985:
979:
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404:
398:
394:
393:
385:
377:
371:
367:
366:
358:
354:
344:
341:
339:
336:
334:
331:
329:
326:
324:
321:
320:
313:
311:
307:
302:
296:
294:
284:
267:
261:P–M σ bonding
255:
246:
244:
240:
236:
232:
206:
198:
189:
187:
185:
172:
164:
160:
151:
149:
145:
141:
126:
116:
108:
99:
97:
93:
89:
82:
78:
74:
70:
66:
62:
58:
54:
50:
46:
42:
38:
34:
30:
26:
25:π backbonding
22:
1482:Applications
1418:Metallocenes
1315:
1208:Baird's rule
928:Charge-shift
917:
891:Hypervalence
782:
776:
759:
754:
748:
723:
718:
712:
695:
689:
670:
661:
644:
638:
628:
609:
603:
584:
550:
546:
536:
517:
511:
492:
486:
467:
461:
442:
436:
417:
411:
391:
384:
364:
357:
305:
298:
290:
276:
211:
183:
170:
152:
124:
121:
92:Zeise's salt
24:
18:
1331:spin states
1198:Aromaticity
1174:Heterolysis
1152:Salt bridge
1097:Noncovalent
1067:Low-barrier
948:Aromaticity
938:Conjugation
918:Pi backbond
310:antibonding
163:Isocyanides
1563:Categories
1279:Principles
1126:aurophilic
1107:Mechanical
720:Chem. Rev.
349:References
81:phosphines
61:phosphines
1530:chemistry
1350:Reactions
1326:Hapticity
1218:spherical
1179:Homolysis
1142:Cation–pi
1117:Chalcogen
1077:Symmetric
933:Hapticity
567:0020-1693
291:The full
69:carbonyls
29:π-bonding
21:chemistry
1147:Anion–pi
1137:Stacking
1059:Hydrogen
970:Metallic
861:Covalent
853:(strong)
740:27704785
669:(2009).
317:See also
301:synergic
283:energy.
1112:Halogen
958:bicyclo
903:Agostic
698:: 653.
231:complex
221:and M–C
77:alkynes
73:alkenes
65:ligands
57:olefins
37:orbital
33:orbital
1213:Möbius
1041:forces
1031:(weak)
797:
738:
677:
616:
591:
565:
524:
499:
474:
449:
424:
399:
372:
241:, and
186:effect
94:, and
85:Ni(CO)
79:, and
63:. The
45:charge
41:ligand
1191:rules
1100:other
988:Ionic
896:3c–4e
884:8c–2e
879:4c–2e
874:3c–2e
293:IUPAC
59:, or
27:is a
953:homo
908:Bent
795:ISBN
736:PMID
675:ISBN
614:ISBN
589:ISBN
563:ISSN
522:ISBN
497:ISBN
472:ISBN
447:ISBN
422:ISBN
397:ISBN
370:ISBN
75:and
787:doi
764:doi
760:253
728:doi
700:doi
649:doi
555:doi
551:359
184:cis
19:In
1565::
793:.
734:.
724:94
643:.
575:^
561:.
545:.
245:.
237:,
188:.
178:CN
174:CN
167:CN
161:.
155:NO
128:CO
98:.
90:,
55:,
23:,
1264:e
1257:t
1250:v
1128:)
1124:(
834:e
827:t
820:v
803:.
789::
770:.
766::
742:.
730::
706:.
702::
683:.
655:.
651::
645:9
635:3
622:.
597:.
569:.
557::
530:.
505:.
480:.
455:.
430:.
405:.
378:.
306:n
280:3
271:3
269:R
259:3
257:R
227:2
225:R
223:2
219:4
217:R
215:2
171:ν
136:6
132:4
125:ν
87:4
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