266:
254:
1005:
107:
115:
999:
205:
197:
1011:
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
745:
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
1464:
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
1098:
1254:
1297:
1216:
1143:
824:
147:
342:
181:
systems. Other ligands have weak π-backbonding abilities, which creates a labilization effect of CO, which is described by the
790:
678:
592:
525:
500:
425:
400:
373:
450:
1312:
1138:
327:
1404:
617:
475:
1570:
1439:
1434:
1399:
1063:
1565:
1449:
1444:
1429:
887:
1078:
1454:
1332:
914:
875:
865:
747:
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
1247:
870:
817:
1505:
308:
d orbital of the metal (which is of π-symmetry with respect to the metal–ligand axis) into the empty π*-
1510:
542:
1560:
1322:
1133:
1123:
1113:
1088:
1058:
1394:
1358:
1263:
1240:
904:
1165:
1068:
1040:
810:
1539:
1424:
158:
1459:
1209:
1170:
1204:
299:
A description of the bonding of π-conjugated ligands to a transition metal which involves a
1414:
1277:
1128:
1019:
882:
841:
230:
8:
1534:
1353:
1327:
1282:
1030:
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337:
242:
234:
1194:
1348:
1302:
949:
666:
238:
265:
1529:
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969:
929:
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613:
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1221:
961:
934:
778:
755:
727:
719:
699:
648:
554:
332:
130:
band(s) from that for free CO (2143 cm), for example to 2060 cm in Ni(CO)
48:
1368:
1363:
1199:
1073:
944:
639:
139:
91:
84:
44:
1485:
1384:
1108:
143:
68:
36:
32:
759:
558:
1554:
1480:
1157:
1117:
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1004:
979:
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833:
566:
389:
Cotton, Frank Albert; Wilkinson, Geoffrey; Murillo, Carlos A., eds. (1999).
1232:
1103:
390:
363:
1409:
1189:
939:
703:
309:
731:
652:
208:π backbonding from electrons in metal center d-orbital to alkene's LUMO.
204:
182:
162:
80:
196:
106:
1521:
1317:
924:
899:
782:
368:(2nd ed.). Upper Saddle River, N.J: Prentice Hall. p. 338.
60:
52:
20:
775:
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.
998:
176:. Depending on the balance of σ-bonding versus π-backbonding, the ν
114:
802:
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:
1465:
Arene complexes of univalent gallium, indium, and thallium
1010:
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,
772:
1552:
693:
587:. Sausalito (Calif.): University science books.
495:. Sausalito (Calif.): University science books.
415:
540:
744:
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)
1248:
818:
777:. Oxford: Blackwell Scientific Publications.
632:
1262:
361:
248:
362:Miessler, Gary L.; Tarr, Donald A. (1999).
295:definition of back donation is as follows:
102:Metal carbonyls, nitrosyls, and isocyanides
1349:Oxidative addition / reductive elimination
1255:
1241:
825:
811:
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).
1298:Polyhedral skeletal electron pair theory
1217: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
773:McNaught, A. D.; Wilkinson, A. (2006).
637:complexes (A = R, Ar, OR; R = alkyl)".
582:
490:
192:Metal–alkene and metal–alkyne complexes
1553:
1236:
806:
578:
576:
16:Form of interaction between two atoms
1405:Transition metal fullerene complexes
612:(2nd ed.). Universities Press.
470:(2nd ed.). Universities Press.
601:
43:, which dissipates excess negative
13:
1440:Transition metal carbyne complexes
1435:Transition metal carbene complexes
1400:Transition metal indenyl complexes
832:
573:
14:
1582:
1450:Transition metal alkyne complexes
1445:Transition metal alkene complexes
484:
459:
395:(6th ed.). New York: Wiley.
287:IUPAC definition of Back Donation
1455:Transition-metal allyl complexes
1009:
1003:
997:
583:Hartwig, John Frederick (2010).
491:Hartwig, John Frederick (2010).
1430:Transition metal acyl complexes
766:
738:
710:
687:
659:
626:
534:
509:
434:
409:
382:
355:
1:
348:
441:Crabtree, Robert H. (2014).
392:Advanced inorganic chemistry
7:
1506:Shell higher olefin process
1313:Dewar–Chatt–Duncanson model
328:Dewar–Chatt–Duncanson model
316:
10:
1587:
1395:Cyclopentadienyl complexes
1359:β-hydride elimination
1333:Metal–ligand multiple bond
915:Metal–ligand multiple bond
150:discusses this in detail.
134:and 1981 cm in Cr(CO)
1519:
1473:
1460:Transition metal carbides
1377:
1341:
1270:
1179:
1156:
1087:
1049:
1029:
1018:
995:
978:
960:
851:
840:
760:10.1016/j.ccr.2008.04.017
559:10.1016/j.ica.2005.12.013
249:Metal-phosphine complexes
1571:Organometallic chemistry
1264:Organometallic chemistry
213:strengthening of the M–C
159:metal–nitrosyl chemistry
157:is a diagnostic tool in
144:metal–carbonyl chemistry
1425:Half sandwich compounds
547:Inorganica Chimica Acta
1566:Coordination chemistry
1540:Bioinorganic chemistry
314:
312:orbital of the ligand.
274:
262:
209:
201:
119:
111:
71:and nitrogen analogs,
1511:Ziegler–Natta process
1415:Metal tetranorbornyls
297:
268:
256:
207:
199:
117:
109:
1520:Related branches of
1278:Crystal field theory
905:Coordinate (dipolar)
704:10.1039/dt9910000653
1535:Inorganic chemistry
1354:Migratory insertion
1328:Agostic interaction
1283:Ligand field theory
1079:C–H···O interaction
861: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
1420:Sandwich compounds
1378:Types of compounds
1303:Isolobal principle
1064:Resonance-assisted
275:
263:
239:tetracyanoethylene
210:
202:
120:
112:
1548:
1547:
1530:Organic chemistry
1501:Olefin metathesis
1491:Grignard reaction
1390:Grignard reagents
1230:
1229:
1181:Electron counting
1152:
1151:
1041:London dispersion
993:
992:
970:Metal aromaticity
792:978-0-9678550-9-7
748: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
1578:
1561:Chemical bonding
1496:Monsanto process
1293:d electron count
1288:18-electron rule
1257:
1250:
1243:
1234:
1233:
1222:Jemmis mno rules
1074:Dihydrogen bonds
1027:
1026:
1013:
1007:
1001:
935:Hyperconjugation
849:
848:
827:
820:
813:
804:
803:
797:
796:
783:10.1351/goldbook
770:
764:
763:
754:(5–6): 704–722.
742:
736:
735:
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:
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538:
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531:
513:
507:
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488:
482:
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
1586:
1585:
1581:
1580:
1579:
1577:
1576:
1575:
1551:
1550:
1549:
1544:
1515:
1469:
1385:Gilman reagents
1373:
1369:Carbometalation
1364:Transmetalation
1337:
1266:
1261:
1231:
1226:
1175:
1148:
1091:
1083:
1045:
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1022:
1014:
1008:
1002:
989:
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831:
801:
800:
793:
771:
767:
743:
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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:
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53:carbon monoxide
17:
12:
11:
5:
1584:
1574:
1573:
1568:
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1526:
1524:
1517:
1516:
1514:
1513:
1508:
1503:
1498:
1493:
1488:
1486:Cativa process
1483:
1477:
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1471:
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1468:
1467:
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1452:
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1300:
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1260:
1259:
1252:
1245:
1237:
1228:
1227:
1225:
1224:
1219:
1214:
1213:
1212:
1207:
1202:
1197:
1186:
1184:
1177:
1176:
1174:
1173:
1168:
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1160:
1154:
1153:
1150:
1149:
1147:
1146:
1141:
1136:
1131:
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1121:
1111:
1106:
1101:
1095:
1093:
1085:
1084:
1082:
1081:
1076:
1071:
1066:
1061:
1055:
1053:
1047:
1046:
1044:
1043:
1037:
1035:
1024:
1020:Intermolecular
1016:
1015:
996:
994:
991:
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988:
987:
984:
982:
976:
975:
973:
972:
966:
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927:
922:
917:
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902:
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891:
890:
880:
879:
878:
873:
868:
857:
855:
846:
842:Intramolecular
838:
837:
834:Chemical bonds
830:
829:
822:
815:
807:
799:
798:
791:
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737:
709:
686:
679:
658:
634:
625:
619:978-8173718748
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526:
508:
501:
483:
477:978-8173718748
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146:. The article
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15:
9:
6:
4:
3:
2:
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1523:
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1507:
1504:
1502:
1499:
1497:
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1492:
1489:
1487:
1484:
1482:
1481:Carbonylation
1479:
1478:
1476:
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1466:
1463:
1461:
1458:
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1451:
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1426:
1423:
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1411:
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1403:
1401:
1398:
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1391:
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1386:
1383:
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1362:
1360:
1357:
1355:
1352:
1350:
1347:
1346:
1344:
1340:
1334:
1331:
1329:
1326:
1324:
1321:
1319:
1316:
1314:
1311:
1309:
1308:π backbonding
1306:
1304:
1301:
1299:
1296:
1294:
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1286:
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1281:
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1223:
1220:
1218:
1215:
1211:
1208:
1206:
1203:
1201:
1198:
1196:
1195:Hückel's rule
1193:
1192:
1191:
1188:
1187:
1185:
1182:
1178:
1172:
1169:
1167:
1164:
1163:
1161:
1159:
1158:Bond cleavage
1155:
1145:
1142:
1140:
1137:
1135:
1132:
1130:
1127:
1125:
1124:Intercalation
1122:
1119:
1115:
1114:Metallophilic
1112:
1110:
1107:
1105:
1102:
1100:
1097:
1096:
1094:
1090:
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1080:
1077:
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1067:
1065:
1062:
1060:
1057:
1056:
1054:
1052:
1048:
1042:
1039:
1038:
1036:
1034:
1031:Van der Waals
1028:
1025:
1021:
1017:
1012:
1006:
1000:
986:
985:
983:
981:
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971:
968:
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951:
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579:
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371:
367:
366:
358:
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344:
341:
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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:
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151:
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126:
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99:
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82:
78:
74:
70:
66:
62:
58:
54:
50:
46:
42:
38:
34:
30:
26:
25:π backbonding
22:
1474:Applications
1410:Metallocenes
1307:
1200:Baird's rule
920:Charge-shift
909:
883:Hypervalence
774:
768:
751:
746:
740:
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:
1323:spin states
1190:Aromaticity
1166:Heterolysis
1144:Salt bridge
1089:Noncovalent
1059:Low-barrier
940:Aromaticity
930:Conjugation
910:Pi backbond
310:antibonding
163:Isocyanides
1555:Categories
1271:Principles
1118:aurophilic
1099:Mechanical
720:Chem. Rev.
349:References
81:phosphines
61:phosphines
1522:chemistry
1342:Reactions
1318:Hapticity
1210:spherical
1171:Homolysis
1134:Cation–pi
1109:Chalcogen
1069:Symmetric
925:Hapticity
567:0020-1693
291:The full
69:carbonyls
29:π-bonding
21:chemistry
1139:Anion–pi
1129:Stacking
1051:Hydrogen
962:Metallic
853:Covalent
845:(strong)
669:(2009).
317:See also
301:synergic
283:energy.
1104:Halogen
950:bicyclo
895:Agostic
698:: 653.
231:complex
221:and M–C
77:alkynes
73:alkenes
65:ligands
57:olefins
37:orbital
33:orbital
1205:Möbius
1033:forces
1023:(weak)
789:
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
1183:rules
1092:other
980:Ionic
888:3c–4e
876:8c–2e
871:4c–2e
866:3c–2e
293:IUPAC
59:, or
27:is a
945:homo
900:Bent
787:ISBN
675:ISBN
614:ISBN
589:ISBN
563:ISSN
522:ISBN
497:ISBN
472:ISBN
447:ISBN
422:ISBN
397:ISBN
370:ISBN
75:and
779:doi
756:doi
752:253
728:doi
700:doi
649:doi
555:doi
551:359
184:cis
19:In
1557::
785:.
724:94
643:.
575:^
561:.
545:.
245:.
237:,
188:.
178:CN
174:CN
167:CN
161:.
155:NO
128:CO
98:.
90:,
55:,
23:,
1256:e
1249:t
1242:v
1120:)
1116:(
826:e
819:t
812:v
795:.
781::
762:.
758::
734:.
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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