MIC) Heterodicarbenes as

Article pubs.acs.org/IC

Bridged N‑Heterocyclic/Mesoionic (NHC/MIC) Heterodicarbenes as Ligands for Transition Metal Complexes Daniel Mendoza-Espinosa,*,†,§ Alejandro Alvarez-Hernández,‡ Deyanira Angeles-Beltrán,† Guillermo E. Negrón-Silva,*,† Oscar R. Suárez-Castillo,‡ and José M. Vásquez-Pérez§ †

Departamento de Ciencias Básicas, Universidad Autónoma Metropolitana-Azcapotzalco, Avenida San Pablo No. 180, Ciudad de México 02200, México ‡ ́ Area Académica de Química, Universidad Autónoma del Estado de Hidalgo, Carretera Pachuca-Tulancingo Km. 4.5, Mineral de la Reforma, Hidalgo 42090, México § CONACYT, Á rea Académica de Química, Universidad Autónoma del Estado de Hidalgo, Carretera Pachuca-Tulancingo Km. 4.5, Mineral de la Reforma, Hidalgo 42090, México S Supporting Information *

ABSTRACT: Following a copper catalyzed alkyne azide cycloaddition (CuAAC) and N-alkylation protocols, we report the preparation of a hybrid N-heterocyclic/ mesoionic [NHC(H+)-MIC(H+)][2I]2− salt (1) in high yields. The treatment of salt 1 with Cu2O and KI yields a second hybrid NHC/MIC proligand featuring a tetraiodocuprate anion [NHC(H+)-MIC(H+)][Cu2I4]2− (2). Through selective deprotonation and metalation, both salts 1 and 2 can generate either the chelate heterodicarbene complexes (3) with the rare [NHC·(M)·MIC]+[MX2]− general formula (M = PdII, RhI) or NHC-anchored/pendent triazolium species (4) [NHC·(M)-MIC(H+)]. If the triazolium moiety of type 4 complexes is deprotonated with KHMDS in the presence of a second metal center, a series of heterobimetallic complexes of the type [NHC·(M)-MIC·(M′)] (5) are achieved. Interestingly, the reaction of salt 2 with KHMDS yields the bimetallic copper heterodicarbene (6) which can be a useful transfer reagent for the preparation of type 3 complexes. A variety of synthetic routes for the preparation of complexes 3−5 and their full characterization in solution and in the solid state will be discussed.

■

INTRODUCTION Ever since the pivotal discovery of Arduengo in 1991,1 the use of N-heterocyclic carbenes (NHCs) has risen tremendously, especially in areas such as homogeneous catalysis and organometallic chemistry.2 The broad interest in NHCs and related species has led to several variations of these ligands as a consequence of their ready structural modifications.3 Particularly, polydentated ligands containing at least one NHC donor group have attracted a great deal of attention in the past decade.4 Depending on the donor strength of the NHC-associated functional group, the generation of metal complexes with a dangling functionality or chelating hybrid ligands may be accessible. While this research field is clearly dominated by NHCs featuring phosphino or amino functionalities, the more recent design of heterodicarbene ligands containing different NHC fragments has led to the preparation of metal complexes with various coordination and electronic environments.5 In line with our research interests in the design of backbone functionalized NHCs, we envisaged the synthesis of hybrid ligands featuring a strongly σ-donor mesoionic triazol-5-ylidene (MIC) linked with a classical NHC. The combination of the different donor strengths of each carbene together with the flexibility of the new ligands could provide an adjustable © XXXX American Chemical Society

platform for metal complexes with improved properties when compared to symmetrical NHCs. Herein, we disclose the facile synthesis of two bridged imidazolium/triazolium salts, namely, [NHC(H+)-MIC(H+)][2I]2− (1) and [NHC(H+)-MIC(H+)][Cu2I4]2− (2). The selective metalation of the azolium fragments in 1 and 2 allows for the preparation of chelated NHC/MIC complexes of the type [NHC·(M)·MIC]+[MX2]− (3) and NHC-anchored/ pendent triazolium species [NHC·(M)-MIC(H+)] (4) (M = PdII, RhI). The subsequent metalation of the triazolium moiety of complexes 4 generates a series of heterobimetallic complexes of the type [NHC·(M)-MIC·(M′)] (5) in high yields. Interestingly, the reaction of salt 2 with KHMDS produces a bimetallic copper heterodicarbene (6) which proves useful as transfer reagent for the one-step preparation of chelated complexes 3. Finally, we will discuss the base choice and metal stoichiometry in the various synthetic routes for the preparation of 3−5 along with their full characterization. Received: November 17, 2016

A

DOI: 10.1021/acs.inorgchem.6b02778 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry

■

RESULTS AND DISCUSSION The preparation of hybrid salt [NHC(H+)-MIC(H+)][2I]2− (1) was performed according to Scheme 1. The first synthetic

coordinated by iodine atoms with a relative close Cu1−Cu2 contact of 2.594(9) Å. The overall dimeric [Cu2I4]2− anion resides in a plane with the Cu−I bond distances following the known trend of analogue systems displaying shorter terminal (2.49 Å) than bridging bond distances (2.58 Å).7 As the copper oxide methodology proved unsuccesful for deprotonating the C(H+) azolium positions of proligand 1, we examined the use of KHMDS (2.5 equiv) in the presence of 1 equiv of [Pd(allyl)Cl]2 and [Rh(COD)Cl]2 to achieve fully metalated species. As depicted in Scheme 3, the one-pot

Scheme 1. Synthesis of Hybrid Salt 1

step involved the copper catalyzed cycloaddition (CuAAC) of precursor A with mesityl azide in acetonitrile followed by bromine exchange with potassium iodide. The subsequent treatment of precursor B with excess methyl iodide provided the expected imidazolium/triazolium salt 1 after induced precipitation with diethyl ether. Pure product was isolated in 51% yield after recrystallization of the crude material with acetonitrile/diethyl ether. The formation of the dicationic product was easily monitored in the 1H NMR spectrum by the appearance of a new signal at ca. 4.5 ppm indicating methylation of the triazolyl moiety and the emergence of the acidic triazolium C(H+) proton located at 9.32 ppm. The initial exploration of the coordination capabilities of salt 1 was established by its treatment with Cu2O and KI (Scheme 2), following a slightly modified protocol reported by Cazin et

Scheme 3. Synthesis of Carbene Metal Complexes 3−5

Scheme 2. Synthesis of Tetraiodo Cuprate Hybrid Salt 2

treatment of salt 1 proceeds cleanly, delivering the chelate complexes of type [NHC·(M)·MIC]+[MX2]− (3) in high yields (84−87%). Remarkably, the same metalation strategy can be applied to hybrid salt 2, although the yields of the chelated complexes are slightly lower (73−82%) when compared to those obtained with precursor 1. The formation of complexes 3a,b was confirmed in 1H NMR by the absence of the two azolium peaks (above 9 ppm) and in 13 C NMR by the presence of two carbene peaks at 162.3 (MICPd) and 175.8 (NHC-Pd) for complex 3a and two doublets at 166.2 (J = 48.0 Hz, MIC-Rh) and 179.1 (J = 52.0 Hz, NHCRh) for complex 3b. Both complexes are air stable and display good solubility in halogenated solvents and toluene. Single crystals of complex 3a were obtained from a THF/ MeCN/hexanes mixture, and the molecular structure is depicted in Figure 2. Complex 3a crystallizes in the orthorhombic Pbca space group with the heterodicarbene

al.6 The 1H NMR spectrum of the reaction crude showed a small amount ( 2σ(I)] R (all data) wR2 [I > 2σ(I)] wR2 (all data) GOF

2

3a

C25H31Cu2I4N5 1036.23 monoclinic P21/n 293(2) 12.4170(5) 16.4991(6) 16.1653(7) 90 95.651(4) 90 3295.7(2) 4 2.088 5.059 53 236 0.621 4539 0.0221 0.0298 0.0449 0.0628 0.0699 1.012

C32H41Cl2I2N5Pd2 1033.20 orthorhombic Pbca 293(2) 21.6108(8) 13.2513(6) 26.3273(12) 90 90 90 7539.4(6) 8 1.820 2.762 109 660 0.829 5005 0.0235 0.0653 0.0922 0.1607 0.1904 1.144

ligand 1 was performed with the DFTB+15 software at the DFTB-SCC level of theory, and local optimizations were performed with the Gaussian 09 software16 at the density functional (DFT) level of theory. For DFT calculations, the local (0% HF exchange) meta-GGA MN12L functional of Thrular17 in combination with the double-ζ Def2-SVP18 basis set for nonmetal atoms, and LANL2DZ19 basis set (and pseudopotential) for Pd and Rh atoms, were used. All optimized geometries were characterized with frequency analysis to confirm that they are minima in the potential energy surface. All four complexes were calculated as singlets (M = 1), modeling ionic complexes as D


Article

Inorganic Chemistry

124.2 (Car), 125.0 (Car), 129.8 (CHar), 130.0 (CHar), 131.4 (CHimid), 131.6 (CHimid), 133.5 (Car), 134.7 (Car), 134.8 (Car), 138.7 (CHtriazolium), 138.8 (Ctz), 141.0 (Car), 142.5 (CHimidazolium). FT-IR/ ATR νmax cm−1: 3018 m, 2980 m, 2941 m, 2791 w, 2801 m, 1587 vs, 1478 vs, 1407 m, 1377 m, 1229 m, 1170 vs, 1081 w, 1006 m, 856 w, 789 w. Found: C, 29.12; H, 3.01; N, 6.57. Calcd for C25H31Cu2I4N5: C, 28.98; H, 3.02; N, 6.76. Synthesis of NHC-MIC Bimetallic Complexes 3a and 3b. Method A. The hybrid salt 1 (0.5 mmol), KHMDS (1.25 mmol), and the appropriate dimeric metal precursor [M]2 (0.5 mmol) were charged in a Schlenk flask. THF (10 mL) was added, and the reaction mixture was stirred at −78 °C for 12 h. The final suspension was filtered via cannula and the solution dried under vacuum. The residue was washed with hexanes (2 × 5 mL) and diethyl ether (2 × 5 mL), and dried to yield the crude product. Pure 3a or 3b was obtained after recrystallization from THF/MeCN/hexanes in 84% (0.21 mmol) and 87% (0.22 mmol) yield, respectively. Method B. Cuprate salt 2 (0.5 mmol), KHMDS (1.25 mmol), and the appropriate dimeric metal precursor [M]2 (0.5 mmol) were charged in a Schlenk flask. THF (10 mL) was added, and the reaction mixture was stirred at −78 °C for 12 h. The final suspension was filtered via cannula and the solution dried under vacuum. The residue was washed with hexanes (2 × 5 mL) and dried to yield the crude product. Pure 3a or 3b was obtained after recrystallization from THF/ MeCN/hexanes in 73% (0.18 mmol) and 82% (0.21 mmol) yield, respectively. Complex 3a. Mp = 171−173 °C. 1H NMR (CDCl3, 400 MHz): δ = 1.92 (s, 6H, Ar−CH3), 1.94 (s, 6H, Ar−CH3), 2.33 (s, 3H, Ar−CH3), 2.36 (s, 3H, Ar−CH3), 3.09 (d, J = 12.0 Hz, 4H, CH(CH2)2), 4.39 (d, J = 8.0 Hz, 4H, CH(CH2)2), 4.59 (pent, 2H, CH(CH2)2), 4.70 (s, 3H, NCH3), 6.03 (d, J = 16.0 Hz, 1H, CH2), 6.32 (d, J = 16.0 Hz, 1H, CH2), 6.93 (s, 1H, CHar), 6.94 (s, 1H, CHar), 6.97 (s, 1H, CHar), 6.98 (s, 1H, CHimid), 6.99 (s, 1H, CHar), 8.29 (s, 1H, CHimid). 13C NMR (CDCl3, 100.6 MHz): δ = 17.6 (ArCH3), 17.7 (ArCH3), 17.9 (ArCH3), 21.1 (ArCH3), 21.2 (CH(CH2)2), 39.6 (CH2), 55.6 (CH(CH2)2), 59.0 CH(CH2)2, 67.4 (NCH3), 109.0 (Car), 118.0 (Car), 121.4 (CHar), 124.5 (CHar), 124.6 (Car), 128.3 (Car), 128.9 (CHar), 129.0 (CHar), 134.5 (CHimid), 134.8 (CHimid), 135.2 (CHar), 135.5 (CHar), 136.2 (Car), 137.4 (Car), 139.2 (Ctz), 140.4 (Car), 162.3 (MIC−Pd), 175.8 (NHC−Pd). FT-IR/ATR νmax cm−1: 3009 m, 2899 m, 2847 m, 2844 w, 2826 w, 1601 m, 1556 vs, 1547 vs, 1512 m, 1436 m, 1425 w, 1411 m, 1215 m, 1147 m, 987 m, 896 w, 801 w. Found: C, 35.49 H, 3.51 N, 6.16. Calcd for C31H39N5I3Pd2: C, 34.63; H, 3.66; N, 6.51. Complex 3b. Mp = 157−159 °C. 1H NMR (CDCl3, 400 MHz): δ = 0.85−0.90 (m, 6H, CH2, COD), 1.70−1.86 (m, 6H, CH2, COD), 1.87−1.91 (m, 6H, CH2, COD), 2.05 (s, 6H, Ar−CH3), 2.14 (s, 6H, Ar−CH3), 2.36 (s, 3H, Ar−CH3), 2.39 (s, 3H, Ar−CH3), 3.92−3.96 (m, 2H, CH, COD), 4.64 (s, 3H, NCH3), 4.89−5.15 (m, 2H, CH, COD), 6.08 (bs, 2H, CH2), 6.78 (s, 1H, CHimid), 6.98 (s, 2H, CHar), 7.01 (s, 2H, CHar), 8.34 (s, 1H, CHimid). 13C NMR (CDCl3, 100.6 MHz): δ = 14.1 (CH2COD), 18.3 (ArCH3), 21.0 (ArCH3), 21.1 (ArCH3), 22.7 (ArCH3), 29.7 (CH2COD), 31.0 (CH2COD), 39.2 (CH2), 46.2 (CH2COD), 71.2 (NCH3), 72.4 (CHCOD), 87.0 (CHCOD), 122.7 (Car), 123.4 (Car), 128.3 (CHar), 128.6 (CHar), 129.0 (Car), 134.6 (CHimid), 135.0 (CHimid), 135.1 (CHar), 136.1 (Car), 139.0 (Car), 139.5 (Ctz), 140.3 (Car), 166.2 (d, J = 48.0 Hz, MIC−Rh), 179.1 (d, J = 52.0 Hz, NHC−Rh). FT-IR/ATR νmax cm−1: 3134 m, 3012 m, 2968 m, 2844 w, 2838 w, 1571 m, 1568 vs, 1520 m, 1497 w, 1466 m, 1425 m, 1411 vs, 1387 m, 1236 m, 1147 m, 987 w, 892 w. Found: C, 41.29 H, 4.17 N, 6.02. Calcd for C41H53N5I3Rh2: C, 40.95; H, 4.44; N, 5.82. Synthesis of NHC-Pd/Pendent Triazolium Complex 4a. Method A. Hybrid salt 1 (131 mg, 0.2 mmol), potassium hexamethydisilazane (KHMDS, 18.0 mg, 0.09 mmol), and allylpalladium chloride dimer (18 mg, 0.05 mmol) were charged in a Schlenk flask purged with nitrogen. Dry THF (7 mL) was added at −78 °C, and the reaction mixture was stirred for 16 h while it reached room temperature. The reaction mixture was filtered via cannula, and the solution was evaporated under vacuum. The residue was extracted with 10 mL of dichloromethane (DCM) and vacuum-dried to yield the crude

cations without explicit inclusion of the counterion. In total two to four different conformations of each complex were calculated, and only the most stable (lowest Gibbs free energy at 298.15 K) of each complex is reported (see SI). Synthesis of Intermediate B. Copper sulfate pentahydrate (100 mg, 0.40 mmol) and sodium ascorbate (120 mg, 0.61 mmol) were charged in a pressure tube, suspended in acetonitrile (7 mL), and stirred for 20 min at 60 °C. Alkyne 1 (122 mg, 0.40 mmol) was added as solid, and the resulting suspension was stirred for 1 h. Mesityl azide (65 mg, 0.40 mmol) was dissolved in a small volume of acetonitrile (2 mL), added to the reaction mixture, and stirred for 48 h at 80 °C. The final green suspension was filtered over Celite and evaporated under reduced pressure. The residue was extracted with 50 mL of a mixture of acetone/dichloromethane (2:1), filtered over Celite, and concentrated under vacuum. The residue was dissolved in acetone (20 mL), and KI was added (0.80 mmol). The mixture was stirred at room temperature for 16 h, filtered over Celite, and dried under vacuum. The final residue was washed with diethyl ether (2 × 30 mL) and dried thoroughly to provide the title compound as a beige solid in 68% yield (0.27 mmol, 125 mg). 1H NMR (DMSO-d6, 400 MHz): δ = 1.89 (s, 6H, Ar−CH3), 2.01 (s, 6H, Ar−CH3), 2.34 (s, 6H, Ar−CH3), 5.77 (s, 2H, CH2), 7.12 (s, 2H, CHar), 7.16 (s, 2H, CHar), 7.98 (s, 1H, CHimid), 8.13 (s, 1H, CHimid), 8.51 (s, 1H, CHtriazole), 9.60 (s, 1H, CHimidazolium). 13 C NMR (DMSO-d6, 100.6 MHz): δ = 17.22 (ArCH3), 17.25 (ArCH3), 21.0 (ArCH3), 21.1 (ArCH3), 44.9 (CH2), 123.9 (Car), 124.7 (Car), 126.9 (Car), 129.4 (CHar), 129.7 (CHar), 131.7 (CHtz), 133.6 (Car), 134.7 (CHimid), 134.9 (CHimid), 138.3 (Ctz), 140.2 (Car), 140.8 (Car), 141.2 (Cimidazolium). FT-IR/ATR νmax cm−1: 3038 w, 2954 m, 2923 m, 2852 m, 1722 vs, 1596 m, 1586 w, 1489 m, 1456 m, 1408 w, 1377 w, 1318 m, 1292 m, 1201 m, 1029 vs, 991 w. Found: C, 55.98; H, 5.41; N, 13.27. Calcd for C24H28IN5: C, 56.15; H, 5.50; N, 13.64. Synthesis of Hybrid Salt 1. Methyl iodide (1.86 mL, 30.0 mmol) was added to a 7 mL acetonitrile solution of salt B (513 mg, 1.0 mmol), and the resulting clear solution was refluxed for 72 h. After the reaction mixture reached room temperature, diethyl ether was added until a precipitate was formed. The solid was collected by filtration and washed thoroughly with cold diethyl ether. Pure product as colorless crystals was obtained in 59% yield (387 mg, 0.59 mmol) after recrystallization with acetonitrile/diethyl ether (1:3). Mp = 193−195 °C. 1H NMR (DMSO-d6, 400 MHz): δ = 2.05 (s, 6H, Ar−CH3), 2.06 (s, 6H, Ar−CH3), 2.35 (s, 3H, Ar−CH3), 2.37 (s, 3H, Ar−CH3), 4.51 (s, 3H, NCH3), 6.03 (s, 2H, CH2), 7.18 (s, 2H, CHar), 7.23 (s, 2H, CHar), 8.08 (s, 1H, CHimid), 8.22 (s, 1H, CHimid), 9.32 (s, 1H, CHtriazolium), 9.60 (s, 1H, CHimidazolium). 13C NMR (DMSO-d6, 100.6 MHz): δ = 17.2 (ArCH3), 17.5 (ArCH3), 21.0 (ArCH3), 21.1 (ArCH3), 41.9 (CH2), 65.3 (NCH3), 124.2 (Car), 125.0 (Car), 129.8 (CHar), 130.0 (CHar), 131.4 (CHimid), 131.5 (CHimid), 133.4 (Car), 134.7 (Car), 134.8 (CHar), 138.8 (CHtriazolium), 138.9 (Ctz), 141.0 (Car), 142.6 (CHimidazolium). FT-IR/ATR νmax cm−1: 3040 m, 2930 m, 2914 w, 2871 w, 2826 m, 1596 vs, 1490 vs, 1459 m, 1407 m, 1329 vs, 1225 m, 1171 m, 1063 w, 1012 w, 789 w. Found: C, 46.01; H, 4.91; N, 10.34. Calcd for C25H31N5I2: C, 45.82; H, 4.77; N, 10.69. Synthesis of Tetraiodocuprate Salt 2. A mixture of the solid salt 1 (655 mg, 1.0 mmol), Cu2O (0.172 mg, 1.2 mmol), and KI (332 mg, 2.0 mmol) was added to a pressure tube under air. Acetonitrile (10 mL) was added to the reaction mixture, and the resulting suspension was refluxed at 80 °C for 16 h (Scheme 3). After the reaction mixture cooled down to room temperature, filtration of the insoluble material via cannula yielded a yellowish supernatant that was further precipitated by the addition of copious amounts of diethyl ether. The resulting brown solid was washed three times with 20 mL portions of diethyl ether, and the pure product is obtained after recrystallization from acetonitrile/Et2O (2:1) as yellow solid in 67% yield (694 mg, 0.67 mmol). Mp = 237−239 °C. 1H NMR (DMSO-d6, 400 MHz): δ = 2.06 (s, 6H, Ar−CH3), 2.07 (s, 6H, Ar−CH3), 2.34 (s, 3H, Ar−CH3), 2.37 (s, 3H, Ar−CH3), 4.54 (s, 3H, NCH3), 6.09 (s, 2H, CH2), 7.18 (s, 2H, CHar), 7.23 (s, 2H, CHar), 8.08 (s, 1H, CHimid), 8.25 (s, 1H, CHimid), 9.35 (s, 1H, CHtriazolium), 9.64 (s, 1H, CHimidazolium). 13C NMR (DMSO-d6, 100.6 MHz): δ = 17.4 (ArCH3), 17.6 (ArCH3), 21.1 (ArCH3), 21.2 (ArCH3), 42.1 (CH2), E


Article

Inorganic Chemistry

(Car), 134.9 (Car), 135.0 (CHar), 136.1 (Car), 139.1 (CHtriazolium), 142.3 (Ctz), 142.5 (Car), 185.4 (d, J = 50.9 Hz, RhC). FT-IR/ATR νmax cm−1: 3012 m, 2992 m, 2941 m, 2902 m, 2826 w, 1590 m, 1556 vs, 1502 m, 1472 m, 1436 w, 1425 w, 1351 m, 1189 m, 1147 m, 973 m, 896 w. Found: C, 45.38 H, 4.52; N, 8.50. Calcd for C33H42N5I2Rh: C, 45.80; H, 4.89; N, 8.09. Synthesis of Heterobimetallic NHC-MIC Complexes 5. The proper monometallic NHC-complex of type 4 (0.25 mmol), KHMDS (0.51 mmol), and the metal precursor [M]2 (0.125 mmol) were charged in a Schlenk flask. THF (10 mL) was added at −78 °C, and the reaction was stirred for 16 h, while it reached room temperature. The reaction mixture was filtered via cannula, and the solution was evaporated under vacuum. The residue was extracted with 5 mL of dichloromethane (DCM) and vacuum-dried to yield the crude product. Pure complex 5a or 5b was obtained in 83% (0.21 mmol) and 92% (0.23 mmol) yield, respectively, after precipitation using a mixture of DCM/ hexanes. Complex 5a. Mp = 129−131 °C. 1H NMR (CDCl3, 400 MHz): δ = 1.21−1.24 (m, 2H, CH2, COD), 1.60 (s, 6H, Ar−CH3), 1.61 (s, 6H, Ar−CH3), 1.72−1.75 (m, 2H, CH2, COD), 1.89 (s, 3H, Ar−CH3), 1.92 (s, 3H, Ar−CH3), 2.10−2.13 (m, 2H, CH2, COD), 2.31−2.33 (m, 2H, CH2, COD), 2.95 (br s, 1H, CH(CH2)2), 3.42−3.45 (m, 2H, CH, COD), 4.11 (s, 3H, NCH3), 4.27 (br s, 1H, CH(CH2)2), 6.68 (br, 1H, CH(CH2)2), 5.10 (d, J = 12.0 Hz, 1H, CH2), 5.14−5.16 (m, 1H, CH, COD), 5.20−5.22 (m, 1H, CH, COD), 5.71−5.75 (br, 1H, CH(CH2)2), 6.04 (d, J = 12.0 Hz, 1H, CH2), 7.37 (s, 2H, CHar), 7.39 (s, 2H, CHar), 7.53 (s, 1H, CHimid), 7.56 (s, 1H, CHimid). 13C NMR (CDCl3, 100.6 MHz): δ = 17.8 (ArCH3), 18.3 (ArCH3), 21.2 (ArCH3), 21.3 (ArCH3), 29.9 (CH2COD), 30.6 (CH2COD), 31.1 (CH2COD), 32.6 (CH2COD), 33.8 (CH(CH2)2), 37.7 (CH2), 54.3 (CH(CH2)2), 58.8 (CH(CH2)2), 67.9 (NCH3), 71.9 (CHCOD), 75.1 (CHCOD), 96.4 (CHCOD), 96.6 (CHCOD), 115.6 (Car), 122.9 (CHar), 129.8 (CHar), 130.7 (CHar), 131.5 (CHar), 134.1 (CHimid), 135.5 (CHimid), 135.56 (Car), 140.1 (Ctz), 140.2 (Car), 163.9 (d, J = 45.0 Hz, MIC−Rh), 177.9 (NHC−Pd). FT-IR/ATR νmax cm−1: 3104 m, 3000 w, 2978 m, 2840 m, 2831 m, 1565 vs, 1561 vs, 1533 m, 1497 m, 1466 w, 1425 w, 1411 m, 1387 m, 1236 w, 1147 w, 987 m, 799 m. Found: C, 42.46; H, 4.34; N, 7.15. Calcd for C36H46N5I2PdRh: C, 42.73; H, 4.58; N, 6.92. Complex 5b. Mp = 118−120 °C. 1H NMR (CDCl3, 400 MHz): δ = 0.88−0.91 (m, 2H, CH2, COD), 1.51 (s, 6H, Ar−CH3), 1.55 (s, 6H, Ar−CH3), 1.80 (s, 3H, Ar−CH3), 1.83 (s, 3H, Ar−CH3), 2.11−2.15 (m, 4H, CH2, COD), 2.32−2.34 (m, 2H, CH2, COD), 2.35−2.37 (m, 2H, CH2, COD), 2.63 (br, 2H, CH(CH2)2), 2.97 (br, 1H, CH, COD), 3.45−3.47 (m, 1H, CH, COD), 4.10 (s, 3H, NCH3), 4.32 (br, 2H, CH(CH2)2), 5.24 (m, 1H, CH, COD), 5.78 (br, 1H, CH(CH2)2), 6.26 (d, J = 12.0 Hz, 1H, CH2), 6.29 (d, J = 12.0 Hz, 1H, CH2), 7.39 (s, 2H, CHar), 7.42 (s, 2H, CHar), 7.56 (s, 1H, CHimid), 7.58 (s, 1H, CHimid). 13 C NMR (CDCl3, 100.6 MHz): δ = 17.8 (ArCH3), 18.2 (ArCH3), 20.9 (ArCH3), 21.3 (ArCH3), 36.1 (CH2COD), 36.7 (CH2COD), 37.2 (CH2COD), 39.9 (CH2COD), 38.8 (CH(CH2)2), 44.0 (CH2), 57.5 (CH(CH2)2), 65.0 (CH(CH2)2), 73.4 (NCH3), 78.2 (CHCOD), 81.1 (CHCOD), 102.5 (CHCOD), 102.9 (CHCOD), 109.3 (Car), 115.2 (Car), 135.4 (CHar), 136.0 (CHar), 137.7 (CHar), 139.92 (CHar), 137.94(CHimid), 140.2(CHimid), 141.7 (Ctz), 145.9 (Car), 166.2 (MIC−Pd), 180.4 (d, J = 45.0 Hz, NHC−Rh). FT-IR/ATR νmax cm−1: 3117 m, 2976 m, 2872 m, 2867 w, 1590 m, 1568 m, 1535 w, 1489 vs, 1466 m, 1427 m, 1411 w, 1392 m, 1236 w, 1176 m, 965 m, 923 m. Found: C, 42.97 H, 4.82 N, 6.65. Calcd for C36H46N5I2PdRh: C, 42.73; H, 4.58; N, 6.92. Synthesis of NHC-MIC Bimetallic Copper Complex 6. Cuprate salt 2 (104 mg, 0.1 mmol) and potassium tert-butoxide (28 mg, 0.25 mmol) were charged in a Schlenk flask purged with nitrogen. Dry THF (7 mL) was added at −78 °C, and the reaction mixture was stirred for 6 h while it reached room temperature (Scheme 4). The reaction mixture was filtered via cannula, and the solution was evaporated under vacuum. The residue was extracted with 10 mL of dichloromethane (DCM) and vacuum-dried to yield the crude product. Pure complex 6 was obtained in 91% (71 mg, 0.091 mmol) after precipitation from a mixture of DCM/hexanes. Mp =

product. Pure 4a was obtained in 69% yield (99 mg, 0.124 mmol) as the last fraction (yellow) of the chromatographic column separation in silica gel using a polar mixture of DCM/acetone (2:1) as eluent. Method B. The cuprate salt 2 (208 mg, 0.2 mmol), potassium hexamethydisilazane (KHMDS, 18.0 mg, 0.09 mmol), and allylpalladium chloride dimer (18 mg, 0.05 mmol) were charged in a Schlenk flask purged with nitrogen. Dry THF (7 mL) was added at −78 °C, and the reaction mixture was stirred for 16 h while it reached room temperature. The reaction mixture was filtered via cannula, and the solution was evaporated under vacuum. The residue was extracted with 10 mL of dichloromethane (DCM) and vacuum-dried to yield the crude product. Pure 4a was obtained in 53% yield (78 mg, 0.095 mmol) as the last fraction (yellow) of the chromatographic column separation in silica gel using a polar mixture of DCM/acetone (2:1) as eluent. Mp = 178−180 °C. 1H NMR (CDCl3, 400 MHz): δ = 2.14 (s, 6H, Ar−CH3), 2.19 (s, 6H, Ar−CH3), 2.35 (s, 3H, Ar−CH3), 2.39 (s, 3H, Ar−CH3), 3.04 (d, J = 4.7 Hz, 2H, CH(CH2)2), 3.25 (br, 1H, CH(CH2)2), 4.12 (br, 1H, CH(CH2)2), 4.47 (s, 3H, NCH3), 5.09 (pent, 1H, CH(CH2)2), 6.02 (d, J = 16.0 Hz, 1H, CH2), 6.12 (d, J = 16.0 Hz, 1H, CH2), 7.05 (s, 2H, CHar), 7.08 (s, 2H, CHar), 7.72 (s, 1H, CHimid), 7.86 (s, 1H, CHimid), 8.86 (s, 1H, CHtriazolium). 13C NMR (CDCl3, 100.6 MHz): δ = 17.4 (ArCH3), 22.6 (ArCH3), 23.0 (ArCH3), 23.8 (ArCH3), 25.6 (CH(CH2)2), 38.8 (CH2), 45.1 (CH(CH2)2), 50.7 (CH(CH2)2), 73.4 (NCH3), 115.5 (Car), 122.6 (Car), 124.2 (Car), 128.3 (CHar), 128.8 (CHar), 129.0 (CHar), 129.3 (Car), 129.8 (Car), 130.5 (CHar), 130.8 (CHimid), 131.2 (CHimid), 134.8 (CHar), 135.1 (CHar), 135.4 (CHtriazolium), 135.9 (Ctz), 139.5 (Car), 183.5 (NHC−Pd). FT-IR/ATR νmax cm−1: 3112 m, 2977 w, 2970 m, 2892 m, 2876 w, 1597 m, 1492 vs, 1459 vs, 1412 m, 1405 m, 1351 w, 1200 w, 1171 m, 1063 m, 997 w, 876 m, 743 m. Found: C, 41.49 H, 4.31; N, 8.34. Calcd for C28H35N5I2Pd: C, 41.94; H, 4.40; N, 8.73. Synthesis of NHC-Rh/Pendent Triazolium Complex 4b. Method A. Hybrid salt 1 (132 mg, 0.2 mmol), potassium hexamethydisilazane (KHMDS, 18.0 mg, 0.09 mmol), and chloro(1,5-cyclooctadiene)rhodium(I) dimer (25 mg, 0.05 mmol) were charged in a Schlenk flask purged with nitrogen. Dry THF (7 mL) was added at −78 °C, and the reaction mixture was stirred for 16 h while it reached room temperature. The reaction mixture was filtered via cannula, and the solution was evaporated under vacuum. The residue was extracted with 10 mL of dichloromethane (DCM) and vacuum-dried to yield the crude product. Pure 4b was obtained in 74% yield (114 mg, 0.133 mmol) as the last fraction (yellow) of the chromatographic column separation in silica gel using a polar mixture of DCM/acetone (2:1) as eluent. Method B. The cuprate salt 2 (208 mg, 0.2 mmol), potassium hexamethydisilazane (KHMDS, 18.0 mg, 0.09 mmol), and chloro(1,5cyclooctadiene)rhodium(I) dimer (25 mg, 0.05 mmol) were charged in a Schlenk flask purged with nitrogen. Dry THF (7 mL) was added at −78 °C, and the reaction mixture was stirred for 16 h while it reached room temperature. The reaction mixture was filtered via cannula, and the solution was evaporated under vacuum. The residue was extracted with 10 mL of dichloromethane (DCM) and vacuumdried to yield the crude product. Pure 4b was obtained in 49% yield (76 mg, 0.088 mmol) as the last fraction (yellow) of the chromatographic column separation in silica gel using a polar mixture of DCM/acetone (2:1) as eluent. Mp = 192−194 °C. 1H NMR (CDCl3, 400 MHz): δ = 1.12−1.14 (m, 2H, CH2, COD), 1.26−1.29 (m, 2H, CH2, COD), 1.43−1.46 (m, 2H, CH2, COD), 1.72−1.72 (m, 4H, CH2, COD), 1.97 (s, 6H, ArCH3), 2.00 (s, 6H, ArCH3), 2.19 (s, 3H, ArCH3), 2.21 (s, 3H, ArCH3), 3.12−3.14 (m, 1H, CH, COD), 3.57−3.61 (m, 1H, CH, COD), 4.84−4.90 (m, 2H, CH, COD), 5.65 (d, J = 16.0 Hz, 1H, CH2), 6.74 (s, 1H, CHar), 6.75 (s, 1H, CHar), 6.86 (s, 1H, CHar), 6.88 (s, 1H, CHar), 7.06 (d, J = 16.0 Hz, 1H, CH2), 7.53 (s, 1H, CHimid), 7.75 (s, 1H, CHimid), 8.97 (s, 1H, CHtriazolium). 13C NMR (CDCl3, 100.6 MHz): δ = 17.2 (CH2COD), 20.2 (ArCH3), 20.3 (ArCH3), 20.8 (ArCH3), 27.5 (ArCH3), 29.4 (ArCH3), 30.1 (ArCH3), 33.6 (CH2COD), 38.3 (CH2), 45.0 (CH2COD), 52.8 (CH2COD), 67.6 (NCH3), 71.7 (CHCOD), 72.3 (CHCOD), 72.4 (CHCOD), 96.4 (CHCOD), 121.0 (Car), 126.1 (Car), 128.4 (CHar), 129.5 (CHar), 129.6 (CHar), 131.0 (CHimid), 131.8 (CHimid), 134.3 F


Article

Inorganic Chemistry 164−166 °C. 1H NMR (DMSO-d6, 400 MHz): δ = 2.02 (s, 6H, Ar− CH3), 2.05 (s, 6H, Ar−CH3), 2.35 (s, 3H, Ar−CH3), 2.37 (s, 3H, Ar− CH3), 4.58 (s, 3H, NCH3), 5.58 (s, 2H, CH2), 6.98 (s, 2H, CHar), 7.00 (m, 1H, CHimid), 7.25 (s, 2H, CHar), 7.82 (d, J = 1.4 Hz, 1H, CHimid). 13 C NMR (DMSO-d6, 100.6 MHz): δ = 17.8 (ArCH3), 18.2 (ArCH3), 21.1 (ArCH3), 21.2 (ArCH3), 38.7 (CH2), 44.9 (NCH3), 122.8 (Car), 128.3 (CHar), 129.5 (CHar), 129.7 (CHar), 134.0 (Car), 134.4 (CHimid), 134.5 (CHimid), 135.1 (CHar), 139.9 (Car), 141.0 (Ctz), 141.8 (Car), 173.6 (MIC−Cu), 182.8 (NHC−Cu). FT-IR/ATR νmax cm−1: 3009 m, 2946 m, 2957 w, 2933 m, 2888 m, 1600 vs, 1512 m, 1499 vs, 1407 m, 1391 m, 1308 m, 1229 vs, 1170 m, 1081 w, 1035 m, 889 m, 765 w. Found: C, 38.70; H, 3.43; N, 8.52. Calcd for C25H29Cu2I2N5: C, 38.47; H, 3.75; N, 8.97. Synthesis of NHC-MIC Bimetallic Complexes 3a and 3b via Copper Transmetalation. Bimetallic copper complex 6 (0.25 mmol) and the dimeric metal precursor [M]2 (0.25 mmol) were charged in a Schlenk flask. DCM (5 mL) was added, and the reaction mixture was stirred at 40 °C for 8 h. The suspension was filtered via cannula and the solution dried under vacuum. The residue was washed with hexanes (2 × 5 mL) and dried to yield the crude product. Pure 3a or 3b was obtained after recrystallization from THF/MeCN/hexanes in 86% (0.21 mmol) and 79% (0.20 mmol) yield, respectively.

■

(b) Pugh, D.; Danopoulos, A. A. Metal Complexes with Pincer-Type Ligands Incorporating N-Heterocyclic Carbene Functionalities. Coord. Chem. Rev. 2007, 251, 610. (c) Liddle, S. T.; Edworthy, I. S.; Arnold, P. L. Anionic Tethered N-Heterocyclic Carbene Chemistry. Chem. Soc. Rev. 2007, 36, 1732. (d) Normand, A. T.; Cavell, K. J. DonorFunctionalised N-Heterocyclic Carbene Complexes of Group 9 and 10 Metals in Catalysis: Trends and Directions. Eur. J. Inorg. Chem. 2008, 2008, 2781. (e) John, A.; Ghosh, P. Fascinating Frontiers of N/Ofunctionalized N-heterocyclic Carbene Chemistry: from Chemical Catalysis to Biomedical Applications. Dalton Trans. 2010, 39, 7183. (f) Bierenstiel, M.; Cross, E. D. Sulfur-functionalized N-Heterocyclic Carbenes and their Transition Metal Complexes. Coord. Chem. Rev. 2011, 255, 574. (g) Fliedel, C.; Braunstein, P. Recent Advances in Sfunctionalized N-Heterocyclic Carbene Ligands: From the Synthesis of Azolium Salts and Metal Complexes to Applications. J. Organomet. Chem. 2014, 751, 286. (5) (a) Aznarez, F.; Miguel, P. J. S.; Tan, T. T. Y.; Hahn, F. E. Preparation of Rhodium(III) Di-NHC Chelate Complexes Featuring Two Different NHC Donors via a Mild NaOAC-Assisted C-H Activation. Organometallics 2016, 35, 410. (b) Aznarez, F.; Iglesias, M.; Hepp, A.; Veit, B.; Miguel, P. J. S.; Oro, L. A.; Jin, G.-X.; Hahn, E. F. Iridium(III) Complexes Bearing Chelating Bis-NHC Ligands and Their Application in the Ctalytic Reduction of Amines. Eur. J. Inorg. Chem. 2016, 2016, 4598. (c) Zamora, M. T.; Ferguson, M. J.; McDonald, R.; Cowie, M. Unsymmetrical Dicarbenes Based on NHeterocyclic/Mesoionic Carbene Frameworks: A Stepwise Metalation Strategy for the Generation of a Dicarbene-Bridged Mixed-Metal Pd/ Rh Complex. Organometallics 2012, 31, 5463. (d) Sluijter, S. N.; Elsevier, C. J. Synthesis and Reactivity of Heteroditopic Dicarbene Rhodium(I) and Iridium(I) Complexes Bearing Chelating 1,2,3Triazolylidene−Imidazolylidene Ligands. Organometallics 2014, 33, 6389. (e) Yuan, D.; Huynh, H. V. Hetero-dicarbene Complexes of Palladium(II): Syntheses and Catalytic Activities. Organometallics 2014, 33, 6033. (f) Hollering, M.; Albrecht, M.; Kühn, F. E. Bonding and Catalytic Application of Ruthenium N-Heterocyclic Carbene Complexes Featuring Triazole, Triazolylidene, and Imidazolylidene Ligands. Organometallics 2016, 35, 2980. (g) Schick, S.; Pape, T.; Hahn, F. E. Coordination Chemistry of Bidentate Bis(NHC) Ligands with Two Different NHC Donors. Organometallics 2014, 33, 4035. (h) Wang, W.; Zhao, L.; Lv, H.; Zhang, G.; Xia, C.; Hahn, F. E.; Li, F. Modular “Click” Preparation of Bifunctional Polymeric Heterometallic Catalysts. Angew. Chem., Int. Ed. 2016, 55, 7665. (6) (a) Bidal, Y. D.; Santoro, O.; Melaimi, M.; Cordes, D. B.; Slawin, A. M. Z.; Bertrand, G.; Cazin, C. S. J. Generalization of the Copper to Late-Transition-Metal Transmetallation to Carbenes Beyond NHeterocyclic Carbenes. Chem. - Eur. J. 2016, 22, 9404. (b) Bidal, Y. D.; Lesieur, M.; Melaimi, M.; Cordes, D. B.; Slawin, A. M. Z.; Bertrand, G.; Cazin, C. S. J. A Simple Access to Transition Metal Cyclopropenylidene Complexes. Chem. Commun. 2015, 51, 4778. (7) (a) Pfitzner, A.; Schmitz, D. Two New Modifications of [P(C6H5)4]2[Cu2I4]. Z. Anorg. Allg. Chem. 1997, 623, 1555. (b) Jagner, S.; Helgesson, G. On the Coordination Number of the Metal in Crystalline Halogenocuprates(I) and Halogenoargentates(I). Adv. Inorg. Chem. 1991, 37, 1. (8) Mendoza-Espinosa, D.; González-Olvera, R.; Negrón-Silva, G. E.; Á ngeles-Beltran, D.; Suárez-Castillo, O. R.; Santillan, R.; AlvarezHernandez, A. Phenoxy-Linked Mesoionic Triazol-5-ylidenes as Platforms for Multinuclear Transition Metal Complexes. Organometallics 2015, 34, 4529. (9) (a) Melaimi, M.; Soleilhavoup, M.; Bertrand, G. Stable Cyclic Carbenes and Related Species Beyond Diaminocarbenes. Angew. Chem., Int. Ed. 2010, 49, 8810. (b) Crabtree, R. H. Abnormal, Mesoionic and Remote N-heterocyclic Carbene Complexes. Coord. Chem. Rev. 2013, 257, 755. (c) Krüger, A.; Albrecht, M. Abnormal Nheterocyclic Carbenes: More than Just Exceptionally Strong Donor Ligands. Aust. J. Chem. 2011, 64, 1113. (d) Schuster, O.; Yang, L.; Raubenheimer, H. G.; Albrecht, M. Beyond Conventional NHeterocyclic Carbenes: Abnormal, Remote, and Other Classes of NHC Ligands with Reduced Heteroatom Stabilization. Chem. Rev.

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.6b02778. Crystallographic information for 2 and 5a (CIF) Sample 1H and 13C NMR spectra of new compounds (PDF)

■

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. *E-mail: [email protected]. ORCID

Daniel Mendoza-Espinosa: 0000-0001-9170-588X Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS We are grateful to the CONACYT (Project 181488) and PRODEP (UAM-PTC-475) for financial support. D.M.-E., G.E.N.-S., D.A.-B., and A.A.-H. wish to acknowledge the SNI for the distinction and the stipend received.

■

REFERENCES

(1) Arduengo, A. J.; Harlow, R. L.; Kline, M. A Stable Crystalline Carbene. J. Am. Chem. Soc. 1991, 113, 361. (2) (a) N-Heterocyclic Carbenes in Transition Metal Catalysis and Organocatalysis; Cazin, C. S. J., Ed.; Springer: Berlin, 2011. (b) Hopkinson, M. N.; Richter, C.; Schedler, M.; Glorius, F. An Overview of N-Heterocyclic Carbenes. Nature 2014, 510, 485. (c) NHeterocyclic Carbenes: Effective Tools for Organometallic Synthesis; Nolan, S. P., Ed.; Wiley-VHC: Weinheim, Germany, 2014. (3) (a) N-Heterocyclic Carbenes in Synthesis; Nolan, S. P., Ed.; WileyVHC: Weinheim, Germany, 2006. (b) Benitez, D.; Shapiro, N. D.; Tkatchouk, E.; Wang, Y.; Goddard, W. A., III.; Toste, F. D. A Bonding Model for Gold(I) Carbene Complexes. Nat. Chem. 2009, 1, 482. (c) Díez-González, S.; Marion, N.; Nolan, S. P. N-Heterocyclic Carbenes in Late Transition Metal Catalysis. Chem. Rev. 2009, 109, 3612. (4) (a) Hahn, F. E.; Jahnke, M. C. Heterocyclic Carbenes: Synthesis and Coordination Chemistry. Angew. Chem., Int. Ed. 2008, 47, 3122. G


Article

Inorganic Chemistry 2009, 109, 3445. (e) Mendoza-Espinosa, D.; Osornio, C.; NegrónSilva, G. E.; González-Olvera, R.; Santillan, R. Versatile O- and Sfunctionalized 1,2,3-Triazoliums: Ionic Liquids for the Baylis−Hillman Reaction and Ligand Precursors for Stable MIC-transition Metal Complexes. New J. Chem. 2015, 39, 1587. (10) Furst, M. R. L.; Cazin, C. S. J. Copper N-heterocyclic Carbene (NHC) Complexes as Carbene Transfer Reagents. Chem. Commun. 2010, 46, 6924. (11) He, Y.; Lv, M.-F.; Cai, C. A Simple Procedure for PolymerSupported N-Heterocyclic Carbene Silver Complex via Click Chemistry: An efficient and Recyclable Catalyst for the One-pot Synthesis of propargylamines. Dalton Trans 2012, 41, 12428. (12) Warsink, S.; Drost, R. M.; Lutz, M.; Spek, A. L.; Elsevier, C. J. Modular Synthesis of Bidentate Triazolyl-Functionalized N-heterocyclic Carbenes and their Palladium complexes. Organometallics 2010, 29, 3109. (13) (a) Mendoza-Espinosa, D.; Negrón-Silva, G.; Lomas-Romero, L.; Gutiérrez-Carrillo, A.; Soto-Castro, D. Multicomponent Synthesis of Mono-, Bis-, and Tris-1,2,3-Triazoles Supported by Hydroxy Benzene Scaffolds. Synthesis 2013, 45, 2431−2437. (b) MendozaEspinosa, D.; Negrón-Silva, G.; Lomas-Romero, L.; Gutiérrez-Carrillo, A.; Santillán, R. Facile One-Pot Synthesis of of 1,2,3-Triazoles Featuring Oxygen, Nitrogen and Sulfur Pendant Arms. Synth. Commun. 2014, 44, 807−817. (14) Sheldrick, G. M. SHELXS-97, Program for Crystal Structure Solution and Refinement; Institut Für Anorganishe Chemie: Göttingen, Germany, 1998. (15) Aradi, B.; Hourahine, B.; Frauenheim, T. DFTB+, a Sparse Matrix-Based Implementation of the DFTB Method. J. Phys. Chem. A 2007, 111, 5678. (16) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, J. A.; Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin, K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.; Millam, J. M.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.; Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, Ö .; Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J. Gaussian 09, Revision C.01; Gaussian Inc.: Wallingford, CT, 2010. (17) Peverati, R.; Truhlar, D. G. An improved and broadly accurate local approximation to the exchange−correlation density functional: The MN12-L functional for electronic structure calculations in chemistry and physics. Phys. Chem. Chem. Phys. 2012, 14, 13171. (18) Weigend, F.; Ahlrichs, R. Balanced basis sets of split valence, triple zeta valence and quadruple zeta valence quality for H to Rn: Design and assessment of accuracy. Phys. Chem. Chem. Phys. 2005, 7, 3297. (19) (a) Hay, P. J.; Wadt, W. R. J. Chem. Phys. 1985, 82, 270. (b) Hay, P. J.; Wadt, W. R. J. Chem. Phys. 1985, 82, 284. (c) Hay, P. J.; Wadt, W. R. J. Chem. Phys. 1985, 82, 299.

H


MIC) Heterodicarbenes as

Recommend Documents