Group 10 and group 11 transition metal chemistry of benzimidazolin 2 ylidene and indazolin 3 ylidene ligands

GROUP 10 AND GROUP 11 TRANSITION METAL CHEMISTRY OF BENZIMIDAZOLIN-2-YLIDENE AND INDAZOLIN-3-YLIDENE LIGANDS RAMASAMY JOTHIBASU (M.Sc., ANNA UNIVERSITY, CHENNAI, INDIA) A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF CHEMISTRY NATIONAL UNIVERSITY OF SINGAPORE 2010 Acknowledgements Acknowledgements I would like express my greatest gratitude to my supervisor Dr Huynh Han Vinh for his kind guidance and patience throughout my research I am really fortunate to be his student as he taught me things not only related to Chemistry but also other aspects like presentation skills My sincere thanks to the technical staff at X-ray diffraction (Prof Koh and Miss Tan), Nuclear Magnetic Resonance (Mdm Han and Mr Chee Ping), Mass spectrometry and Elemental Analysis laboratories for their technical support I would like to thank my group members Han Yuan, Yuan Dan, Hong Lee, Surajit and Weiheng for their assistance and helpful discussions I appreciate my friends in Singapore Balaji, Karthik and Ranga for their support and timely help I am very grateful to NUS for my research scholarship Last but not least, I am very thankful to my family members for their unconditional love and incredible support I Table of contents Table of contents V Summary VIII Chart Compounds synthesized in this work List of tables XI List of figures XII List of schemes XV List of abbreviations XVII Introduction 1.1 Definition of carbenes 1.2 Synthesis, electronic structures and applications of N-heterocyclic carbenes 1.3 Preparation and application of N-heterocyclic carbene complexes 1.4 Aim and objective 11 16 Palladium(II) complexes of benzimidazolin-2-ylidenes bearing non-halo 22 anionic co-ligands and their reactivity towards isopropylthiol 2.1 Synthesis and characterization of mixed dicarboxylato-bis(carbene) 22 Pd(II) complexes 2.2 Reactivity study of the mixed diacetato-bis(carbene) Pd(II) complexes 27 towards isopropylthiol Nickel(II) complexes of benzimidazolin-2-ylidene ligands 32 3.1 Mixed diazido-bis(carbene) nickel(II) complexes 32 3.1.1 Synthesis and characterization of mixed diazido-bis(carbene) 32 Ni(II) complex 3.1.2 Reactivity study of mixed diazido-bis(carbene) Ni(II) complex 34 II Table of contents towards isocyanides 3.1.3 Template directed synthesis of a mixed benzimidazolin-2-ylidene/ 41 tetrazolin-5-ylidene complex 3.2 Mixed diisothiocyanato-bis(carbene) nickel(II) complexes 3.2.1 Synthesis and characterization of mixed isothiocyanato-bis(carbene) 45 45 Ni(II) complexes 3.2.2 Catalytic studies in the Kumada-Corriu reaction 3.3 Homoleptic tetracarbene and cis-chelating di(carbene) complexes 49 53 of nickel(II) 3.3.1 Synthesis and characterization of ligand precursor 53 3.3.2 Synthesis and characterization of Ni(II) complexes 54 3.3.3 Catalytic studies in the Kumada-Corriu reaction 60 Au(I) and Au(III) complexes of 1,3-diisopropylbenzimidazolin-2-ylidene 63 4.1 Synthesis of monocarbene and bis(carbene) Au(I) complexes 63 4.2 Synthesis of bis(carbene) Au(III) complex 67 4.3 Electronic Properties of complexes 13-15 69 Synthesis of Pd(II), Au(I) and Rh(I) complexes of indazolin-3-ylidenes 72 5.1 Synthesis of ligand precursors 5.2 Synthesis of transition metal complexes 73 5.3 Evaluation of donor strength of indazolin-3-ylidene ligands 72 81 Palladium and gold complexes of fused indazolin-3-ylidene ligands 90 6.1 Synthesis of ligand precursors 90 6.2 Synthesis of Pd(II) complexes 92 III Table of contents 6.3 Synthesis of monocarbene Au(I) and Au(III) complexes 94 Conclusions 102 Experimental Section 107 Appendix 145 Reference 154 IV Summary Summary This dissertation reports the synthesis, reactivity and catalytic studies of transition metal complexes (mainly Ni, Pd and Au) bearing benzimidazolin-2-ylidene and indazolin-3-ylidene ligands The findings of the research are presented in five chapters Chapter describes the synthesis of mono- and dipalladium complexes of benzimidazolin-2-ylidene ligands The reaction of Pd(OAc)2 with 1,3- dibenzylbenzimidazolium bromide (A) and 1-propyl-3-methylbenzimidazolium iodide (B) afforded the dihalo-bis(carbene) complexes cis-[PdBr2(Bz2-bimy)2] (1a) and cis[PdI2(Pr,Me-bimy)2] (1b), respectively Halide substitution of 1a and 1b with AgO2CCH3 gave the mixed diacetato-bis(carbene) complexes cis-[Pd(O2CCH3)2(Bz2-bimy)2] (2a) and cis-[Pd(O2CCH3)2(Pr,Me-bimy)2] (2b) in good yields The reactivity of these complexes (2a and 2b) toward aliphatic thiols has been investigated In situ deprotonation of isopropylthiol (iPr-SH) by the basic acetato ligands of 2a and 2b yielded the novel dipalladium complexes [Pd2(μ-iPr-S)2(Bz2-bimy)4](BF4)2 (3a) and [Pd2(μ-iPrS)2(Pr,Me-bimy)4](BF4)2 (3b) with a [Pd2S2] core solely supported by N-heterocyclic carbenes Chapter deals with a series of Ni(II) NHC complexes bearing non-halo anionic co-ligands Salt metathesis reaction of the dihalo-bis(carbene) complex trans-[NiBr2(iPr2bimy)2] (C, 1,3-diisopropylbenzimidazolin-3-ylidene) with NaN3 yielded the diazidobis(carbene) complex trans-[Ni(N3)2(iPr2-bimy)2] (4), which has been used as a template for the cycloaddition reactions of organic isocyanides Depending on the reaction conditions and the type of isocyanides used for cycloaddition reactions, a mixed V Summary tetrazolato-carbodiimido complex trans-[Ni(CN4-Xyl)(NCNXyl)(iPr2-bimy)2] (5), a dicarbodiimido complex trans-[Ni(NCN-Xyl)2(iPr2-bimy)2] (6), and ditetrazolato complexes trans-[Ni(CN4-R)2(iPr2-bimy)2] (7, R = tert-butyl; 8, R = cyclohexyl) were obtained in good yields The novel cationic “abnormal” tetrazolin-5-ylidene complex trans-[Ni(CN4-tBu,Me)2(NHC)2](BF4)2 (7) was also synthesized by direct methylation of with [Me3O]BF4 In addition, mixed diisothiocyanato-bis(carbene) nickel(II) complexes [Ni(NCS)2(R,R’-bimy)2] (10a, R = R’ = isopropyl; 10b, R = R’ = isobutyl; 10c, R = R’ = benzyl; 10d, R = R’ = 2-propenyl; 10e, R = propyl, R’ = methyl) were synthesized by the metathetical reaction of AgSCN with the corresponding dihalo-bis(carbene) Ni(II) complexes trans-[NiX2(R,R’-bimy)2] (C-G) A preliminary catalytic study showed that complexes 10a-e are active precatalysts in the Kumada-Corriu coupling reaction with the best performance observed for 10d Besides that, the reaction of methylene-bridged diazolium salt [MeCCmethH2]Br2 (11a) with Ni(OAc)2 yielded a dicationic bis(chelate) complex [Ni(MeCCmeth)2]Br2 (12a), whereas a neutral monochelate complex [NiBr2(MeCCprop)] (12c) was obtained by the reaction of a more flexible propylenebridged carbene precursor [MeCCpropH2]Br2 (11c) with Ni(OAc)2 The catalytic activity of 12c was tested in the Kumada–Corriu coupling reactions Complex 12c performs better than the isothiocyanato complexes (10a-e) as well as tetracarbene complex 12a Chapter describes the synthesis and photophysical properties of Au(I) and Au(III) complexes The reaction of [AuCl(SMe2)] with in situ generated [AgCl(iPr2-bimy)], which in turn was obtained by the reaction of Ag2O with 1,3-diisopropylbenzimidazolium bromide (iPr2-bimyH+Br, H), afforded the Au(I) complex [AuCl(iPr2-bimy)] (13) Subsequent reaction of 13 and iPr2-bimyH+BF4 (I) in the presence of K2CO3 yielded the VI Summary bis(carbene) complex [Au(iPr2-bimy)2]BF4 (14) The oxidative addition of elemental iodine to 14 gave Au(III) complex trans-[AuI2(iPr2-bimy)2]BF4 (15), which shows absorption and photoluminescence properties owing to a LMCT In Chapter 5, the synthesis and properties of the first Pd(II), Au(I) and Rh(I) complexes with indazolin-3-ylidene ligands are described Reaction of 1,2dimethylindazolium iodide (16a, Me2-indyH+I) and 1,2-diethylindazolium iodide (16b, Et2-indyH+I) with Pd(OAc)2 afforded dimeric Pd(II) complexes [PdI2(R2-indy)]2 (17a/b) The latter readily undergo cleavage reactions with PPh3 to yield mixed carbene/co-ligand complexes [PdI2(PPh3)(R2-indy)] (18a/b) in good yields Halide substitution of 18a/b with AgO2CCF3 gave the corresponding trifluoroacetato complexes [Pd(O2CCF3)2(PPh3)(R2-indy)] (19a/b) In addition, transmetalation reactions of [PdBr2(CH3CN)2], [AuCl(SMe2)] and [RhCl(cod)] with in situ generated Ag-carbene complexes, afforded [PdBr2(Et2-indy)]2 (20), [AuCl(Et2-indy)] (21) and [RhCl(cod)(Me2indy)] (22), respectively Furthermore, the studies on -donor properties of the new indazolin-3-ylidene ligands were also carried out Chapter deals with the synthesis of Pd(II) and Au(I) complexes bearing fused indazolin-3-ylidene ligands The reaction of Ag2O with fused indazolium salts C3IndyH+Br- (28a), C4-IndyH+Br- (28b) and C5-IndyH+Br- (28c) yielded the corresponding Ag-carbene complexes in situ, which were subsequently added to [PdBr2(CH3CN)2] and [AuCl(SMe)2] to afford the corresponding [PdBr2(Cn-indy)]2 (29a-c) and [AuCl(Cnindy)] (31a-c) complexes The metathetical reaction of Au(I) 31a-c with LiBr afforded [AuBr(Cn-indy)] (32a-c), to which bromine was oxidatively added to obtain the respective Au(III) complexes [AuBr3(Cn-indy)] (33a-c) VII Chart Chart Compounds synthesized in this work 2+ NR N R' R N NR X Pd X NR' 1a: R = R' = CH2Ph, X = Br 1b: R = Pr, R' = Me, X = I iPr N3 iPr N Ni N N iPr N iPr N N R' R N NR O2CCH3 Pd O2CCH3 NR' N C N N S S iPr RN N N N BF4 RN 3a: R = R' = CH2Ph 3b: R = Pr, R' = Me R iPr i N iPr N C N iPr N Ni N N R R' N Pd R iPr R'N iPr Pd NR' 2a: R = R' = CH2Ph 2b: R = Pr, R' = Me iPr N R' R N Pr N i Pr N Ni N R R = 2,6-dimethylphenyl N C N N iPr R = 2,6-dimethylphenyl S N N N NR i i Pr Pr N N Ni N N iPr iPr RN N N N 7: R = tert-butyl 8: R = cyclohexyl N N N NR i iPr Pr N N Ni N N iPr iPr RN N 2BF4 N N R = tert-butyl C N R' N N Ni N N R' N R C S R 10a: R = R' = iPr 10b: R = R' = iBu 10c: R = R' = benzyl Br2 N R R N N R' N C S Ni N C S N N N N 2Br N R' N N N Ni N N N N N 11c 10d: R = R' = propenyl 10e: R = Pr, R' = Me 12a VIII Chart N N N N Br N Au N N Ni N Au Cl N N Br BF4 12c 14 13 R N I Au I N N N BF4 15 R R N N Pd N R I R N N Pd N Br I I O2CCF3 N R Br Pd O2CCF3 Pd Br Pd Br Br R N N Au Cl 19a R = Me 19b R = Et 21 N N CO Rh CO I 25 N N L Rh L Cl L Rh L I N N Br N Pd Br 26 N N N R CO Rh CO Cl 24 23, L L = cod N N 20 R = Et N N 22 L L = cod N R 17a R = Me 17b R = Et PPh3 18a R = Me 18b R = Et N 16d R N PPh3 I Pd R 16a R = Me, X = I 16b R = Et, X = I 16c R = Et, X = Br I R I N R N X R N N N Br N Pd Br N N 27 IX Appendix Continued… formula fw color, habit cryst size [mm] temp [K] crys syst space group a [Å] b [Å] c [Å]  [deg]  [deg]  [deg] V [Å3] Z Dc [g cm3] radiation used  [mm1]  range [deg] no of unique data max., transmn final R indices [I > 2(I)] R indices (all data) goodness-of-fit on F2 peak/hole [e Å3] 10a C28H36N6S2Ni 549.46 colorless, block 0.32  0.24  0.14 223(2) monoclinic P2(1)/c 8.799(3) 18.152(6) 9.661(3) 90 91.646(7) 90 1542.3(8) 1.248 Mo K 0.790 2.2427.48 10477 0.8974, 0.7860 R1 = 0.0623, wR2 = 0.1353 R1 = 0.1000, wR2 = 0.1500 0.989 0.852/0.246 10b C32H44N6S2Ni 635.56 orange, block 0.28  0.26  0.16 295(2) triclinic P-1 9.3168(7) 10.0285(8) 10.3736(8) 103.240(2) 94.178(2) 113.049(2) 853.75(11) 1.236 Mo K 0.720 2.0527.50 11224 0.8935, 0.8238 R1 = 0.0573, wR2 = 0.1447 R1 = 0.0693, wR2 = 0.1538 1.055 0.697/0.323 10c C44H36N6S2Ni 771.62 yellow, plate 0.80  0.20  0.10 223(2) monoclinic P2(1)/c 12.6333(11) 18.7005(16) 8.4257(7) 90 106.050(2) 90 1913.0(3) 1.340 Mo K 0.657 1.6827.50 13453 0.9372, 0.6217 R1 = 0.0541, wR2 = 0.1208 R1 = 0.0784, wR2 = 0.1313 1.034 0.652/0.406 10d C28H28N6S2Ni 571.39 yellow, block 0.52  0.21  0.18 293(2) monoclinic C2/c 14.5167(14) 13.9716(15) 14.0918(14) 90 100.996(2) 90 2805.6(5) 1.353 Mo K 0.868 2.0427.50 9861 0.8954, 0.6609 R1 = 0.0497, wR2 = 0.1191 R1 = 0.0624, wR2 = 0.1255 1.049 0.654/0.353 148 Appendix Continued… formula fw color, habit cryst size [mm] temp [K] crys syst space group a [Å] b [Å] c [Å]  [deg]  [deg]  [deg] V [Å3] Z Dc [g cm3] radiation used  [mm1]  range [deg] no of unique data max., transmn final R indices [I > 2(I)] R indices (all data) goodness-of-fit on F2 peak/hole [e Å3] 10e C24H28N6S2Ni 523.35 yellow, rhombus 0.12  0.10  0.08 223(2) monoclinic C2/c 17.0446(12) 14.3126(11) 10.7475(8) 90 97.304(2) 90 2600.6(3) 1.337 Mo K 0.930 1.8627.48 8986 0.9293, 0.8966 R1 = 0.0597, wR2 = 0.1302 R1 = 0.0762, wR2 = 0.1374 1.128 0.649/0.257 12a·0.5H2O C34H32Br2N8Ni·0.5H2O 780.21 colorless, rod 0.24  0.06  0.04 223(2) monoclinic P2(1)/n 11.8792(15) 10.0604(14) 13.9968(19) 90 97.895(4) 90 1656.9(4) 1.564 M K 3.036 2.5027.50 11296 0.8882, 0.5294 R1 = 0.0877, wR2 = 0.1481 R1 = 1336, wR2 = 1643 1.141 1.026/0.603 12c·C3H7NO C19H20Br2N5Ni·C3H7NO 596.02 brown , block 0.16  0.16  0.10 223(2) orthorhombic P2(1)2(1)2(1) 8.1304(4) 15.8139(8) 18.7790(10) 90 90 90 2414.5(2) 1.640 M K 4.137 1.0827.48 17199 0.6824, 0.5574 R1 = 0619, wR2 = 1444 R1 = 0719, wR2 = 1502 1.143 1.561/0.875 13 C13H18ClN2Au 434.71 colorless, block 0.320.150.10 223(2) orthorhombic Pnma 12.2392(7) 10.5451(6) 10.8541(6) 90 90 90 1400.87(14) 2.061 M K 10.673 2.527.50 9410 0.4150, 0.1314 R1 = 0.0275, wR2 = 0.0741 R1 = 0.0298, wR2 = 0.0751 1.130 2.198/0.564 149 Appendix Continued… formula fw color, habit cryst size [mm] temp [K] crys syst space group a [Å] b [Å] c [Å]  [deg]  [deg]  [deg] V [Å3] Z Dc [g cm3] radiation used  [mm1]  range [deg] no of unique data max., transmn final R indices [I > 2(I)] R indices (all data) goodness-of-fit on F2 peak/hole [e Å3] 14 C26H36BF4N4Au 688.36 colorless, block 0.30  0.26  0.10 223(2) monoclinic C2/c 39.7851(18) 12.6663(6) 11.6182(5) 90 104.6900(10) 90 5663.4(4) 1.615 M K 5.242 1.6927.50 19857 0.6222, 0.3023 R1 = 0.0304, wR2 = 0.0729 R1 = 0.0402, wR2 = 0.0764 1.045 1.930/0.649 15·CH2Cl2 C26H36N4F4I2BAu·CH2Cl2 1027.09 orange, rod 0.40  0.12  0.10 293(2) orthorhombic Pmc2(1) 10.7779(5) 11.2233(5 15.3725(7) 90 90 90 1859.51(15) 1.834 M K 5.802 1.8127.45 12536 0.5946, 0.2049 R1 = 0.0343, wR2 = 0.0872 R1 = 0.0364, wR2 = 0.0882 1.081 2.109/0.722 18b C29H29I2N2PPd 796.71 yellow, block 0.24  0.08  0.06 223(2) monoclinic P2(1)/n 11.4399(10) 15.6813(14) 16.1726(14) 90 99.776(2) 90 2859.1(4) 1.851 Mo K 2.885 1.8227.50 19912 0.8459, 0.5443 R1 = 0.0521, wR2 = 0.1156 R1 = 0.0652, wR2 = 0.1216 1.075 1.391/1.437 19a C31H25F6O4N2PPd 740.9 colorless, block 0.56  0.36  0.20 223(2) triclinic P-1 9.4768(5) 11.0752(6) 15.6695(9) 107.8900(10) 100.5030(10) 96.7700(10) 1512.08(14) 1.627 Mo K 0.743 1.4027.50 18022 0.8656, 0.6809 R1 = 0.0287, wR2 = 0.0734 R1 = 0.0302, wR2 = 0.0744 1.053 0.792/0.723 150 Appendix Continued… formula fw color, habit cryst size [mm] temp [K] crys syst space group a [Å] b [Å] c [Å]  [deg]  [deg]  [deg] V [Å3] Z Dc [g cm3] radiation used  [mm1]  range [deg] no of unique data max., transmn final R indices [I > 2(I)] R indices (all data) goodness-of-fit on F2 peak/hole [e Å3] 20 C22H28N4Br4Pd2 880.92 orange, block 0.30  0.23  0.16 223(2) monoclinic P2(1)/n 9.5153(16) 11.2069(18) 12.916(2) 90 95.929(4) 90 1369.9(4) 2.136 Mo K 7.164 2.4127.50 9280 0.3936, 0.2224 R1 = 0.0645, wR2 = 0.1771 R1 = 0.1019, wR2 = 0.1968 1.052 2.959/0.993 21 C11H14N2ClAu 406.66 yellow, block 0.30  0.20  0.12 100(2) monoclinic P2(1)/c 8.5290(6) 8.5217(6) 17.3001(11) 90 103.8820(10) 90 1220.67(14) 2.213 Mo K 12.240 2.4327.50 8394 0.3213, 0.1204 R1 = 0.0191, wR2 = 0.0461 R1 = 0.0206, wR2 = 0.0467 1.065 1.301/0.791 22 C17H22N2ClRh 392.73 yellow, block 0.30  0.20  0.06 223(2) triclinic P-1 7.0142(4) 9.5187(6) 12.8813(8) 75.2460(10) 82.9050(10) 74.5310(10) 800.12(8) 1.630 Mo K 1.229 1.6427.50 5717 0.9299, 0.7094 R1 = 0.0336, wR2 = 0.0829 R1 = 0.0358, wR2 = 0.0842 1.065 1.025/0.466 30a C12H13N3Br2Pd 465.47 yellow, block 0.30  0.14  0.10 100(2) monoclinic P2(1)/c 9.4099(17) 12.173(3) 12.280(2) 90 90.10(2) 90 1406.6(5) 2.198 M K 6.985 2.3627.46 9583 0.5418, 2284 R1 = 0243, wR2 = 0573 R1 = 0278, wR2 = 0585 1.054 0.863 /0.336 151 Appendix Continued… formula fw color, habit cryst size [mm] temp [K] crys syst space group a [Å] b [Å] c [Å]  [deg]  [deg]  [deg] V [Å3] Z Dc [g cm3] radiation used  [mm1]  range [deg] no of unique data max., transmn final R indices [I > 2(I)] R indices (all data) goodness-of-fit on F2 peak/hole [e Å3] 30b·CH3CN C13H15N3Br2Pd·CH3CN 520.55 Yellow, block 0.40  0.36  0.08 100(2) monoclinic P2(1)/c 9.8647(10) 11.5490(11) 15.5559(16) 90 94.278(2) 90 1767.3(3) 1.956 M K 5.573 2.0727.49 12205 0.6641, 0.2140 R1 = 0310, wR2 = 0734 R1 = 0376, wR2 = 0752 1.015 1.007/0.650 30c·CH3CN C14H17N3Br2Pd·CH3CN 534.58 yellow, block 0.50  0.30  0.28 223(2) orthorhombic Pca2(1) 25.4587(12) 9.1094(4) 8.3673(4) 90 90 90 1940.49(16) 1.830 M K 5.078 1.6027.49 13010 0.3305, 0.1856 R1 = 0256, wR2 = 0602 R1 = 0281, wR2 = 0610 1.037 0.687/0.522 31b C11H12N2AuCl 404.64 yellow , block 0.60  0.22  0.20 293(2) monoclinic P2(1)/c 20.5207(9) 16.2535(8) 13.8301(7) 90 101.6150(10) 90 4518.3(4) 16 2.379 M K 13.227 1.0127.50 31895 0.1773, 0.0465 R1 = 0.0471, wR2 = 0.1184 R1 = 0561, wR2 = 1221 1.106 6.497/3.756 31c C12H14N2AuCl 418.67 Yellow, rod 0.40  0.24  0.22 100(2) orthorhombic Pccn 8.6092(4) 15.5589(7) 17.7188(8) 90 90 90 2373.43(19) 2.343 12.594 2.3027.49 15852 0.1682, 0.0813 R1 = 0.0293, wR2 = 0.0770 R1 = 0320, wR2 = 0783 1.095 2.726/0.767 152 Appendix Continued… formula fw color, habit cryst size [mm] temp [K] crys syst space group a [Å] b [Å] c [Å]  [deg]  [deg]  [deg] V [Å3] Z Dc [g cm3] radiation used  [mm1]  range [deg] no of unique data max., transmn final R indices [I > 2(I)] R indices (all data) goodness-of-fit on F2 peak/hole [e Å3] 32b C11H12N2AuBr 449.10 colorless, block 0.64  0.12  0.10 223(2) orthorhombic Pca2(1) 17.9194(13) 8.1817(6) 7.9629(6) 90 90 90 1167.45(15) 2.555 M K 15.991 2.2727.49 7831 0.2977, 0.0348 R1 = 0.0411, wR2 = 0.0874 R1 = 0.0466, wR2 = 0901 1.105 1.572/2.685 33a C10H10Br3N2Au 594.90 orange , block 0.24  0.24  0.10 100(2) triclinic P-1 8.0993(7) 10.9408(10) 15.8960(15) 91.062(2) 104.643(2) 101.034(2) 1334.3(2) 2.961 M K 19.983 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Pd1-S2 2. 35 19(18), Pd2-S1 2. 35 02( 17), Pd2-S2 2. 36 73( 16); C1-Pd1-C 12 92. 4 (2) , C 23- Pd2-C34 94.1 (3) , C1-Pd1-S1 90. 42( 16), C 12- Pd1S2 93 .24 (18), C 23- Pd2-S1 88 .10( 6), C34-Pd2-S2 94. 03( 19), C1-Pd1-S2 174 .27 (17),... Benzimidazolin- 2- ylidene Imidazolidin -2- ylidene Topology unsaturated, aromatic benzannulated, aromatic saturated, nonaromatic (C2) [ppm] 21 1- 22 1 22 3 - 23 2 23 8 -24 5 Angle N1-C2-N3 [] 101 .2( 2) -1 02 .2( 2) 1 03 .5(1) -104 .3( 1)... = 29 c n = Br N Au Cl N n 31 a n = 31 b n = 31 c n = N Au Br N n 32 a n = 32 b n = 32 c n = N Au Br N Br n 33 a n = 33 b n = 33 c n = X List of tables List of Tables Table 3. 1 Selected bond lengths and