Article pubs.acs.org/Organometallics
Strong Cytotoxicity of Organometallic Platinum Complexes with Alkynyl Ligands Anna Lüning,† Julia Schur,‡ Laura Hamel,‡ Ingo Ott,‡ and Axel Klein*,† †
Department für Chemie, Institut für Anorganische Chemie, Universität zu Köln, Greinstraße 6, D-50939 Köln, Germany Institute of Medicinal and Pharmaceutical Chemistry, Technische Universität Braunschweig, Beethovenstraße 55, D-38106 Braunschweig, Germany
‡
S Supporting Information *
ABSTRACT: The synthesis, spectroscopy, structures, and chemical reactivity of the organometallic complexes [(COD)Pt(CCR)2] and [(COD)Pt(CCR)(R′)] (COD = 1,5-cyclooctadiene, R = Ph, (Me)Ph (2Me, 3Me, or 4Me), (NO2)Ph (2NO2, 3NO2, or 4NO2), (4F)Ph, (4OMe)Ph, 2Py (2-pyridyl); R′ = Me (methyl), Neop (neopentyl = 2,2-dimethyl-1-methyl), NeoSi (neosilyl = trimethylsilylmethyl), Bz (benzyl)) has been explored. The crystal structures reveal square-planar surroundings of the Pt atoms with short Pt−C(alkynyl) bonds (2.7 Å (C···F > 3 Å).27,28 The molecular structures show perfectly square planar surroundings around the Pt atoms for all complexes, with the two centroids X(1) and X(2) representing the olefin ligand (Tables 3 and 4 and Figure 4). In this respect, the COD ligand exhibits a rather invariant bite angle of about 85°, as observed for related COD organo Pt(II) complexes.16−19,29 The alkynyl C−Pt bond is rather short in all complexes (1.3 V or medium-strong reductants with potentials 100 8.3 ± 3.0 10.2 ± 3.5 1.3 ± 0.0 13.5 ± 2.2 9.0 ± 1.7 3.2 ± 1.5 0.2 ± 0.1 4.6 ± 0.2 15.6 ± 5.2 2.9 ± 1.2 2.3 ± 0.7 10.8 ± 3.1 29.0 ± 7.2 0.5 ± 0.3 0.5 ± 0.1 0.1 ± 0.0 0.4 ± 0.1 0.6 ± 0.1 0.4 ± 0.1 0.6 ± 0.2 0.4 ± 0.1 0.3 ± 0.1
2.0 >100 11.2 ± 1.4 9.8 ± 1.0 2.1 ± 0.9 13.2 ± 0.5 10.5 ± 7.9 5.0 ± 0.8 0.3±0.1 4.6 ± 0.5 9.1 ± 3.9 1.6 ± 0.3 1.9 ± 0.6 6.8 ± 1.1 17.6 ± 8.2 0.4 ± 0.2 0.4 ± 0.1 0.1 ± 0.0 0.3 ± 0.0 0.3 ± 0.1 0.2 ± 0.1 0.3 ± 0.2 80 °C) rapid decomposition can be observed (half-lifes ∼0.5 − 1 h). Reaction with Glutathione, Chloride, and Protons. In PrOH/H2O (4/1) the complex [(COD)Pt(Me)(CC(4NO2)Ph)] reacts very slowly with glutathione. When monitoring the reaction by UV−vis absorption spectroscopy, we found only a 1% spectral change after 3 days (figures are given in the Supporting Information). In solutions of higher concentrations using NMR spectroscopy, we observed a traceable amount of a species of composition [(COD)Pt(Me)(L)]n+ after 3 days. The trans 2JPt,H(CH) coupling constant of ∼85 Hz points to a rather weak ligand L, which is either H2O or the glutathione RSH or RNH2 function. A thiolate or carboxylate ligand (deprotonated glutathione) can be ruled out, as the corresponding coupling constants should be around 60− 70 Hz. For example, for the hydroxo complex [(COD)Pt(Me)(OH)] 65 Hz was reported,16 while the reported value for the aqua complex [(COD)Pt(Me)(H2O)]+ of 89 Hz (in the same solvent, CDCl3) supports the assumption that glutathione is the ligand L and not H2O. Additionally, we also observed the decomposition reaction described above, leading to the dialkynyls, COD, and elemental Pt. When adding chloride (as n-Bu4NCl) to a solution of [(COD)Pt(Me)(CC(4NO2)Ph)] in THF or i-PrOH/H2O (1/1), we observed a marked spectroscopic change (UV−vis) only for a 5-fold excess of chloride and a reaction time of 30 min (about 12% loss of absorption at 358 nm). When these solutions were left standing
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for 18 h, approximately half of the complex was decomposed, the main products being [(COD)PtCl2] and [(COD)Pt(Me)Cl] (NMR in CDCl3), as expected. Finally, the same complex was reacted with increasing amounts of protons (from HBF4). Interestingly, proton concentrations corresponding to a pH of 6 to 2 did not lead to marked spectral changes (UV−vis) after standing for 30 min; however, at pH 1 the complex rapidly decomposes. In CDCl3 solution a notable number of unassignable signals appear at pH 1 after 30 min. Correlation spectroscopy led to the characterization of one main species, which seems to be a [(COD)Pt(Me)Y]n+ complex with the Me and Y ligands, leading to a trans 2JPt,H(CH) coupling constant of 36 Hz for Me and 100 Hz for Y, respectively. Again Y must be very weak ligand: e.g., for the acetone complex [(COD)Pt(Me)(acetone)]+ 91 Hz has been reported.16 Thus, while a pH of 1 leads to rapid decomposition of the complex, it is remarkably stable at low to medium H+ concentrations and variable amounts of glutathione or chloride both in organic and in aquatic (water-containing) solutions. Cytotoxicity. In a continuation of our previous work on the cytotoxicity of organoplatinum(II) COD complexes with mixed alkyl/alkynyl ligands [(COD)Pt(Me)(CCR)], we extended our study to platinum COD complexes with phenylalkynyl coligands of the type [(COD)Pt(alkynyl)2] and evaluated their antiproliferative properties in HT-29 colon carcinoma and MCF-7 breast adenocarcinoma cell lines in a comparative manner. Previous studies on platinum COD species had indicated that replacing one chlorido ligand of [(COD)PtCl2] with methyl resulted in a considerable increase in cytotoxic potency.19 Introducing different substituted phenylalkynyl ligands in the position of the chlorido ligand led to species with activities in the range of 0.2−30 μM (Table 8). By replacement of the methyl ligand with a second phenylalkynyl coligand it was possible to obtain symmetric bis-alkynyl 3667
dx.doi.org/10.1021/om400293u | Organometallics 2013, 32, 3662−3672
Organometallics
Article
for the behavior of the complexes in solution. The molecular structures reveal quite strong PtC(alkynyl) bonds, in line with the weakly σ donating but efficiently π accepting nature of the COD ligand. Multinuclear (1H, 13C, 195Pt, and 19F) NMR spectroscopy reveals structures in solution and Pt−ligand bond strengths. The thermal stability in organic solvents, the electrochemical stability, and the reactivity of the complexes in organic or aquatic (water-containing) solution toward the physiologically relevant species glutathione, chloride, and protons were tested. While the thermally activated selftransmetalation of the mixed complexes [(COD)Pt(Me)(C CR)] to [(COD)Pt(CCR)2] and [(COD)Pt(Me)2] was unexpected, the prevailing decomposition of the dialkynyl complexes [(COD)Pt(CCR)2] to dialkynyl RCCCCR, COD, and Pt has been reported before. Nevertheless, the overall stability is quite high. Marked decomposition occurs only at elevated temperatures (>80 °C) or very prolonged times (>3 days). The same is true for the reactivity toward glutathione, Cl−, and H+. Only a very high H+ concentration, corresponding to pH 1, led to rapid decomposition (within 30 min); under less harsh conditions the complexes are quite inert. The cytotoxicity for selected platinum alkynyl COD complexes was determined in HT-29 colon carcinoma and MCF-7 breast adenocarcinoma cell lines and revealed promising activities in the submicromolar range. Taken together with the results of the stability experiments, the increased activity of the dialkynyl derivatives could be related to their higher kinetic reactivity.
platinum complexes with an increased antiproliferative activity in the submicromolar range. The highest activity was observed for the m-methyl-substituted phenylalkynyl complex [(COD)Pt(CC(3Me)Ph)2], which was more than 10-fold active than the platinum anticancer lead compound cisplatin and also more active than its methyl-substituted derivative [(COD)Pt(Me)(CC(3Me)Ph)]. Moreover, we could observe some very interesting properties of this novel class of platinum COD complexes concerning structure−activity relationships (SAR). With a few exceptions the dialkynyl platinum COD complexes were more cytotoxic than the corresponding methyl-substituted derivatives. The more quickly decomposing Pt−alkynyl bond of this type of complex might be more beneficial concerning antiproliferative activity than the stronger bond of the methyl coligand to Pt. In addition, the perpendicular orientation of the CC−aryl group to the Pt coordination plane might be relevant to the higher cytotoxic effect. We also studied substituent effects at different positions (o, m, p) of the aromatic system for nitro and methyl groups. In the case of the methyl group the position at the phenylalkynyl ligand had nearly no influence on the cytotoxic behavior, whereas the p-nitro compound [(COD)Pt(CC(4NO2)Ph)2] was less active than the other nitrosubstituted derivatives. The p-methoxy- and p-fluorine-substituted complexes were also tested and showed comparable activities with IC50 values below 1 μM. Similar results were observed for the pyridine-substituted Pt alkynyl complex [(COD)Pt(CC2Py)2]. The differences in biological activity between platinum complexes of the type [(COD)Pt(CCR)2] and [(COD)Pt(Me)(CCR)] can be attributed to different electronic effects of the substituents and consequently different kinetic reactivities of the complexes and, furthermore, to possible differences in their biodistribution and interaction with biological targets, suggesting more detailed bioactivity studies on selected complexes of these cytotoxic platinum compounds. In a previous study we had reported on alkynyl(phosphane)gold(I) complexes, which triggered antiproliferative as well as antianiogenic effects.39 For these complexes the inhibition of the tumor-relevant enzyme thioredoxin reductase (TrxR) could be confirmed. On the basis of these studies it could be speculated that in addition to DNA, which represents the established target of most anticancer platinum compounds, TrxR might also be a molecular target for the platinum alkynyl species presented here. Further studies that are in progress will address these questions.
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EXPERIMENTAL SECTION
Instrumentation. The NMR spectra were recorded on a Bruker Avance II 300 MHz (1H, 300.13 MHz; 13C, 75.47 MHz; 19F, 282.23 MHz) using a triple-resonance 1H,19F,BB inverse probehead at 300 K. The broad-band coil was tuned to either the carbon or the platinum frequency and the detection coil to the proton frequency, resulting in 90° pulses of 11.9 μs for 13C, 12.5 μs for 195Pt, and 12.4 μs for 1H. The unambiguous assignment of the 1H, 13C, and 195Pt resonances was obtained from 1H TOCSY, 1H COSY, 1H NOESY, gradient selected 1 13 H, C HSQC and HMBC, and gradient selected 1H,195Pt HMBC experiments. All 2D NMR experiments were performed using standard pulse sequences from the Bruker pulse program library. Chemical shifts were relative to TMS for 1H and 13C, CFCl3 for 19F, and Na2[PtCl6] in D2O for 195Pt. The spectral analyses were performed by the Bruker TopSpin 2 software. EI-MS spectra were measured with a Finnigan MAT 900 S instrument. Simulations were performed using ISOPRO 3.0. Elemental analyses were carried out using a Hekatech CHNS EuroEA 3000 Analyzer. IR spectra were measured on a Bruker IFS66νS instrument. Raman spectra were measured using a Bruker FRA106S spectrometer. UV−vis absorption spectra were recorded on a Varian Cary50 Scan spectrophotometer. Electrochemical experiments were carried out in 0.1 M solutions of n-Bu4NPF6 in CH2Cl2 or THF using a three-electrode configuration (glassy-carbon working electrode, Pt counter electrode, Ag/AgCl pseudo reference) and an Autolab PGSTAT30 potentiostat and function generator. The ferrocene/ferrocenium couple served as an internal reference. Crystal Structure Determination. The data collection was performed at T = 173(2) or 293(2) K on a STOE IPDS I diffractometer with Mo Kα radiation (λ = 0.71073 Å) employing the ω−2θ scan technique. The structure was solved by direct methods using SHELX-97 and WinGX,41 and refinement was carried out with SHELXL97 employing full-matrix least-squares methods on F2 42 with Fo2 ≥ 2σ(Fo2) with the results provided in the Supporting Information. All non-hydrogen atoms were treated anisotropically; hydrogen atoms were included by using appropriate riding models. CCDC files 929268 ([(COD)Pt(CC(2Me)Ph)2]), 929269 ([(COD)Pt(CC(3Me)Ph)2]), 929270 ([(COD)Pt(CC(4Me)Ph)2]), 929271 ([(COD)Pt(CC(4F)Ph)2]), 929272 ([(COD)Pt(CC(4OMe)Ph)2]),
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CONCLUSIONS The new organometallic complexes cis-[(COD)Pt(CCR)2] and cis-[(COD)Pt(R′)(CCR)] (COD = 1,5-cyclooctadiene; R = Ph, (Me)Ph (2Me, 3Me, or 4Me), (NO2)Ph (2NO2, 3NO2, or 4NO2) (4F)Ph, (4OMe)Ph, 2Py (2-pyridyl); R′ = Me (methyl), Neop (neopentyl = 2,2-dimethyl-1-methyl), NeoSi (neosilyl = trimethylsilylmethyl), Bz (benzyl)) containing the chelate COD ligand and various alkyl and alkynyl ligands have been synthesized in good to excellent yields. Due to their high tendency to crystallize (without the inclusions of other molecules) they can be perfectly purified. The determined crystal structures reveal square-planar surroundings of the Pt atoms and an almost perpendicular orientation of the CC−aryl group to the Pt coordination plane. Nonattractive π−π stacking and C−H···F intermolecular interactions were observed in the crystal structures but were surely not relevant 3668
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Organometallics
Article
1009, 988, 913, 871, 863, 833, 810, 780 (m), 761, 697 (s): δ(CC− H). EI-MS: 505 [M]+. λmax (THF): 255, 326 nm. [(COD)Pt(CC(2Me)Ph)2]: yield 76 mg (0.142 mmol, 53%). Anal. Calcd for C26H26Pt (533.52): C, 58.53; H, 4.91. Found: C, 58.50; H, 4.88. 1H NMR (δ, CDCl3): 7.37 (m, 2H, o-Ph), 7.16−7.03 (m, 6H, m-Ph, p-Ph), 5.71 (m, 4H, CH COD, 2JPt,H = 45 Hz), 2.59 (m, 8H, CH2 COD, 3JPt,H ≈ 16 Hz), 2.48 (s, 6H, o-CH3). 195Pt,1H HMBC (δ, CDCl3): −3205. IR (KBr, in cm−1): 3087, 3056, 3011 (w): ν(CC−H); 2950, 2922, 2894, 2834 (m): ν(H2C−H) and ν(HC− H); 2116 (s): ν(CC); 1596, 1477 (s): ν(CC(aryl)); 1454, 1427 (s): δ(H2C−H) and δ(HC−H); 989, 952, 862, 833 (m), 763, 717 (s): δ(CC−H). EI-MS: 533 [M]+. λmax (THF): 253, 284, 293, 330 nm. [(COD)Pt(CC(2NO2)Ph)2]: yield 94 mg (0.158 mmol; 59%). Anal. Calcd for C24H20N2O4Pt (595.50): C, 48.41; H, 3.39; N, 4.70. Found: C, 48.50; H, 3.38; N, 4.66. 1H NMR (δ, CDCl3): 7.91 (d, 2H, m-Ph), 7.66 (d, 2H, o-Ph), 7.47 (t, 2H, p-Ph), 7.31 (t, 2H, m-Ph), 5.84 (m, 4H, CH COD, 2JPt,H = 45 Hz), 2.61 (m, 8H, CH2 COD, 3JPt,H ≈ 16 Hz). 195Pt,1H HMBC (δ, CDCl3): −3226. IR (KBr, in cm−1): 3097, 3065, 3023, 3002 (w): ν(CC−H); 2961, 2928, 2889, 2838 (m): ν(H2C−H) and ν(HC−H); 2123 (s): ν(CC); 1599, 1565, 1517 (s): ν (CC(aryl)) and νas(NO2); 1474, 1433 (m): δ(H2C−H) and δ(HC−H); 1340 (s): νs NO2; 1001, 862, 782 (m), 741 (s): δ(CC−H) and ν(C−N); 666 (m): δ(NO2). λmax (THF): 247, 271 (sh), 314, 351 nm. [(COD)Pt(CC(3Me)Ph)2]: yield 98 mg (0.184 mmol, 69%). Anal. Calcd for C26H26Pt (533.52): C, 58.53; H, 4.91. Found: C, 58.48; H, 4.86. 1H NMR (δ, CDCl3): 7.24 (s, 2H, o-Ph), 7.21 (d, 2H, o-Ph), 7.11 (t, 4H, m-Ph), 6.97 (d, 2H, p-Ph), 5.68 (m, 4H, CH COD, 2JPt,H = 46 Hz), 2.57 (m, 8H, CH2 COD, 3JPt,H ≈ 17 Hz), 2.27 (s, 6H, m-CH3). 195Pt,1H HMBC (δ, CD2Cl2): −3219. IR (KBr, in cm−1): 3051, 3033, 3000 (w): ν(CC−H); 2970, 2949 (m), 2916, 2902 (s): ν(H2C−H) and ν(HC−H); 2122 (s): ν(CC); 1596, 1481 (s): ν(CC(aryl)); 1448, 1428 (m): δ(H2C−H) and δ(HC−H); 988, 978, 916, 906, 862 (m), 785, 764, 695 (s): δ(CC−H). λmax (THF): 256, 285, 293, 328 nm. [(COD)Pt(CC(3NO2)Ph)2]: yield 101 mg (0.169 mmol, 63%). Anal. Calcd for C24H20N2O4Pt (595.50): C, 48.41; H, 3.39; N, 4.70. Found: C, 48.38; H, 3.36; N, 4.61. 1H NMR (δ, CDCl3): 8.22 (s, 2H, o-Ph), 8.02 (d, 2H, p-Ph), 7.69 (d, 2H, o-Ph), 7.40 (t, 2H, m-Ph), 5.75 (m, 4H, CH COD, 2JPt,H = 45 Hz), 2.63 (m, 8H, CH2 COD, 3JPt,H ≈ 16 Hz). 195Pt,1H HMBC (δ, CDCl3): −3229. IR (KBr, in cm−1): 3100, 3078, 3024, 3005 (w): ν(CC−H); 2950, 2925, 2891, 2831 (m): ν(H2C−H) and ν(HC−H); 2120, 2144 (s): ν(CC); 1612, 1525 (s): ν(CC(aryl)) and νas(NO2); 1471, 1426 (m): δ(H2C−H) and δ(HC−H); 1350 (s): νs(NO2); 997, 894, 863 (m), 809, 736 (s): δ(CC−H) and ν(C−N); 674 (m): δ(NO2). EI-MS: 595 [M]+. λmax (THF): 252, 319 nm. [(COD)Pt(CC(4Me)Ph)2]: yield 106 mg (1.98 mmol, 74%). Anal. Calcd for C26H26Pt (533.57): C, 58.53; H, 4.91. Found: C, 58.46; H, 4.91. 1H NMR (δ, CD2Cl2): 7.24 (d, 4H, o-Ph), 7.06 (d, 4H, m-Ph), 5.64 (m, 4H, CH COD, 2JPt,H = 45 Hz), 2.57 (m, 8H, CH2 COD, 3JPt,H ≈ 17 Hz), 2.31 (s, 6H, 4-CH3). 195Pt,1H HMBC (δ, CD2Cl2): −3209. 1H NMR (δ, DMF-d7): 7.21 (d, 4H, o-Ph), 7.11 (d, 4H, m-Ph), 5.61 (m, 4H, CH COD, 2JPt,H = 44 Hz), 2.61 (m, 8H, CH2 COD), 2.29 (s, 6H, p-CH3). 195Pt,1H HMBC (δ, DMF-d7): −3227. IR (KBr, in cm−1): 3072, 3049, 3021, 3004 (w): ν(CC−H); 2911, 2894 (s): ν(H2C−H) and ν(HC−H); 2124 (s): ν(CC); 1602 (m), 1505 (s): ν(CC(aryl)); 1438, 1428 (m): δ(H2C−H) and δ(HC−H); 988, 967, 940, 902 (m), 861, 841, 815 (s), 765, 739 (m): δ(CC−H). EI-MS: 533 [M]+. λmax (THF): 257, 286, 296, 332 nm. [(COD)Pt(CC(4NO2)Ph)2]: yield 61 mg (0.102 mmol, 38%). Anal. Calcd for C24H20N2O4Pt (595.50): C, 48.41; H, 3.39; N, 4.70. Found: C, 48.33; H, 3.28; N, 4.61. 1H NMR (δ, CD2Cl2): 8.10 (d, 4H, m-Ph), 7.47 (d, 4H, o-Ph), 5.72 (m, 4H, CH COD, 2JPt,H = 45 Hz), 2.62 (m, 8H, CH2 COD). 195Pt,1H HMBC (δ, CD2Cl2): −3231. IR (KBr, in cm−1): 3112, 3071 (w): ν(CC−H); 2923, 2886 (m): ν(HC−H); 2123 (s): ν(CC); 1589, 1511 (s), 1486 (m): ν(C C(aryl)) and νas(NO2); 1422, 1403, 1383 (m): δ(HC−H); 1341 (s): νs(NO2); 1005 (m): δ(CC−H); 858, 848 (s): δ(CC−H) and
929273 ([(COD)Pt(Me)(CC(4F)Ph)]), and 929274 ([(COD)Pt(Me)(CC(3Me)Ph)]) contain the full crystallographic information. These data can be obtained free of charge at www.ccdc.cam.ac.uk/ conts/retrieving.html or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge, CB2 1EZ U.K (fax, + 44-1223336-033; e-mail,
[email protected]). Cytotoxicity. The antiproliferative activity of platinum alkynyl COD complexes in HT-29 colon carcinoma and MCF-7 breast adenocarcinoma cell lines was determined according to an established procedure.43 In short, the compounds were freshly prepared as stock solutions in dimethylformamide (DMF) and diluted with DMEM cell culture medium supplemented with 50 mg/L and 10% (v/v) fetal calf serum (“medium”) to the desired concentrations (0.1% v/v DMF). The medium containing the test compound in different concentrations was added to 96-well plates, in which the cells had been grown, with 6 replicates. The untreated controls contained the same amount of DMF (0.1% v/v), which does not cause cytotoxic effects. After an incubation period of 72 h for HT-29 cells and 96 h for MCF-7 cells the plates were stained with crystal violet to determine the cell biomass. The IC50 values were calculated as that concentration reducing proliferation of untreated control cells by 50%. Results are expressed as means and error of two to four independent experiments. Stability/Reactivity Investigations. The complexes [(COD)Pt(Me)(CC(4NO2)Ph)], [(COD)Pt(CC(4NO2)Ph)2], [(COD)Pt(Me)(CC(4Me)Ph)], and [(COD)Pt(CC(4Me)Ph)2] were tested for their thermal stability in DMF solution. The compounds were dissolved in DMF or DMF-d7, and time-dependent NMR and UV−vis spectra were recorded. The tests on the complex [(COD)Pt(Me)(CC(4NO2)Ph)] against glutathione were performed in a mixture of i-PrOH and H2O (4/1) (UV−vis) or CDCl3 (for NMR); for the Cl− testing n-Bu4NCl was used in THF or i-PrOH/H2O (1/1) solution for UV−vis or CDCl3 solution for NMR spectroscopic monitoring. HBF4 in THF (UV−vis) or CDCl3 (NMR) solution was used to assess the reactivity toward protons. Materials and Procedures. All preparations were carried out under a dry argon atmosphere using Schlenk techniques. Solvents (CH2Cl2, THF, toluene, diethyl ether, and MeCN) were dried using a MBraun MB SPS-800 solvent purification system. The complexes [(COD)PtCl2], [(COD)Pt(Me)2], and [(COD)Pt(R′)Cl] (R′ = Me, Bz, Neop, or NeoSi) were prepared according to published procedures.19,44 The alkynes HCCR were either purchased from Acros (R = Ph) or Alfa Aesar (R = (3Me)Ph, (4Me)Ph, (4F)Ph) or prepared for R = (4OMe)Ph,45 (2Me)Ph,45 (2NO2)Ph,46 (3NO2)Ph,46 (4NO2)Ph47 following established procedures. The purity of the materials thus obtained was checked by 1H and 13C NMR spectroscopy, MS, and elemental analyses with good to excellent results (in comparison to reported data). All other chemicals were purchased from commercial suppliers and were used without further purification. Synthesis of [(COD)Pt(CCR)2] (R = Ph, (2Me)Ph, (3Me)Ph, (4Me)Ph, (2NO2)Ph, (3NO2)Ph, (4NO2)Ph, (4F)Ph, (4OMe)Ph, 2Py). The compounds were prepared in a variation of the method described for [(COD)Pt(CCPh)2]:48 a suspension of 100 mg (0.267 mmol) of [(COD)PtCl2] in 10 mL of ethanol was maintained at −5 °C, and a freshly prepared mixture of the alkyne (0.587 mmol, 2.2 equiv) and sodium ethoxide (prepared from 14 mg sodium) or 66 mg (0.587 mmol, 2.2 equiv) of potassium tert-butoxide in 5 mL of ethanol were added dropwise with constant stirring. The solutions became darker, and after 1 h the colorless products were filtered off. Recrystallization from CH2Cl2/n-heptane gave the pure products as microcrystalline materials. [(COD)Pt(CCPh)2]: yield 67 mg (0.134 mmol, 50%). Anal. Calcd for C24H22Pt (505.52): C, 57.02; H, 4.39. Found: C, 56.98; H, 4.33. 1H NMR (δ, CD2Cl2): 7.35 (d, 4H, o-Ph), 7.23 (m, 6H, m-Ph, pPh), 5.66 (m, 4H, CH COD, 2JPt,H = 45 Hz), 2.58 (m, 8H, CH2 COD, 3JPt,H ≈ 17 Hz). 195Pt,1H HMBC (δ, CD2Cl2): −3320. IR (KBr, in cm−1): 3074, 3052 (w), 3023, 3008 (m): ν(CCH); 2965, 2943, 2915, 2895 (m): ν(HC−H); 2125 (s): ν(CC); 1638, 1597 (m), 1485, 1475 (s): ν(CC(aryl)); 1451, 1440, 1427 (s): δ(HC−H); 3669
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Organometallics
Article
ν(C−N); 822, 768 (m), 747, 690 (s): δ(CC−H); 638 (m): δ(NO2). λmax (THF): 231, 273, 345 nm. [(COD)Pt(CC(4F)Ph)2]: yield 89 mg (0.164 mmol, 62%). Anal. Calcd for C24H20F2Pt (541.49): C, 53.23; H, 3.72. Found: C, 53.11; H, 3.68. 1H NMR (δ, CD2Cl2): 7.33 (dd, 4H, o-Ph), 6.95 (d, 4H, m-Ph), 5.64 (m, 4H, CH COD, 2JPt,H = 45 Hz), 2.57 (m, 8H, CH2 COD). 195 Pt,1H HMBC (δ, CD2Cl2): −3226. 19F NMR (δ, CD2Cl2): −115. IR (KBr, in cm−1): 3066, 3036, 3027, 3013 (w): ν(CC−H); 2914, 2902 (m): ν(HC−H); 2129 (s): ν(CC); 1594, 1586 (m), 1501 (s): ν(CC(aryl)); 1429, 1400, 1383 (m): δ(HC−H); 1222, 1210 (s): ν(C−F); 995, 865 (m), 839 (s), 812, 769, 746, 693 (m): δ(CC− H); 532, 504 (m): δ(C−F). λmax (THF): 252, 287, 297, 325 nm. [(COD)Pt(CC(4OMe)Ph)2]: yield 79 mg (0.139 mmol, 52%). Anal. Calcd for C26H26O2Pt (565.56): C, 55.22; H, 4.63. Found: C, 55.11; H, 4.68. 1H NMR (δ, CDCl3): 7.34 (m, 4H, o-Ph), 6.77 (m, 4H, m-Ph), 5.67 (m, 4H, CH COD, 2JPt,H = 46 Hz), 3.78 (s, 6H, OCH3), 2.56 (m, 8H, CH2 COD, 3JPt,H ≈ 16 Hz). 195Pt,1H HMBC (δ, CDCl3): −3211. IR (KBr, in cm−1): 3065, 3031 (w), 3000 (m): ν(CC−H); 2954, 2917, 2893, 2833 (m): ν(H2C−H) and ν(HC− H); 2125 (s): ν(CC); 1600 (s), 1505 (s): ν(CC(aryl)); 1462 (s), 1440, 1427, 1411, 1399 (m): δ(H2C−H) and δ(HC−H); 1286, 1244, 1178, 1165, 1033 (s): ν(C−OC); 988, 863, 839, 830 (s), 808, 766 (m), 734, 693 (s): δ(CC−H). λmax (THF): 259, 295, 306, 341 nm. [(COD)Pt(CC2Py)2]: yield 122 mg (0.241 mmol, 90%). Anal. Calcd for C22H20N2Pt (507.49): C, 52.07; H, 3.97; N, 5.52. Found: C, 52.03; H, 3.92; N, 5.50. 1H NMR (δ, CDCl3): 8.49 (d, 2H, 6-Py), 7.54 (dt, 2H, 4-Py), 7.39 (d, 2H, 3-Py), 7.07 (d, 2H, 5-Py), 5.79 (m, 4H, CH COD, 2JPt,H = 45 Hz), 2.58 (m, 8H, CH2 COD, 3JPt,H ≈ 17 Hz). 195 Pt,1H HMBC (δ, CDCl3): −3235. IR (KBr, in cm−1): 3076, 3052 (w): ν(CC−H); 2995, 2974, 2914, 2901 (m): ν(HC−H); 2131 (s): ν(CC); 1583 (s), 1496 (m): ν(CC(aryl)); 1459, 1421 (s), 1391 (m): δ(HC−H); 991 (s) 861, 825 (m), 781, 766 (s), 742 (m): δ(C C−H). EI-MS: 507 [M]+. λmax (THF): 249, 290, 320 nm. Synthesis of [(COD)Pt(Me)(CCR)2] (R = Ph, (2Me)Ph, (3Me)Ph, (4Me)Ph, (2NO2)Ph, (3NO2)Ph, (4NO2)Ph, (4F)Ph, (4OMe)Ph, 2Py). The compounds were prepared in a variation of the method described for [(COD)Pt(CCPh)2]:47 a suspension of 100 mg (0.283 mmol) of [(COD)Pt(Me)Cl] in 10 mL of ethanol was maintained at −5 °C, and a freshly prepared mixture of the alkyne (0.311 mmol, 1.1 equiv) and sodium ethoxide (prepared from 7 mg sodium) or 34 mg (0.311 mmol, 1.1 equiv) of potassium tert-butoxide in 5 mL of ethanol were added dropwise with constant stirring. The solutions became darker, and after 1 h the reaction mixture was evaporated to dryness under reduced pressure. Recrystallization from CH2Cl2/n-heptane of the resulting solid gave the pure microcrystalline products. [(COD)Pt(Me)(CCPh)]: yield 92 mg (0.218 mmol, 77%). Anal. Calcd for C17H20Pt (419.42): C, 48.68; H, 4.81. Found: C, 48.64; H, 4.80. 1H NMR (δ, CD2Cl2): 7.30 (d, 2H, o-Ph), 7.21 (m, 3H, m-Ph, pPh), 5.47 (m, 2H, CH COD(a), 2JPt,H = 36 Hz), 4.92 (m, 2H, CH COD(b), 2JPt,H = 49 Hz), 2.47−2.42 (m, 8H, CH2 COD, 3JPt,H ≈ 10,0 Hz), 0.95 (s, 3H, CH3, 2JPt,H = 77 Hz). 195Pt,1H-HMBC (δ, CD2Cl2): −3209. IR (KBr in cm−1): 3039, 3012, 2991 (w): ν(CC− H); 2928, 2880 (s): ν(H2C−H) and ν(HC−H); 2111 (s): ν(CC); 1596, 1487 (s): ν(CC(aryl)); 1442, 1426 (s), 1395, 1384 (m): δ(H2C−H) and δ(HC−H); 997, 978, 916, 863, 838, 819, 799, 785 (m), 759, 695 (s): δ(CC−H). EI-MS: 419 [M]+. λmax (THF): 251, 261, 308 nm. [(COD)Pt(Me)(CC(2Me)Ph)]: yield 48 mg (0.110 mmol, 39%). Anal. Calcd for C18H22Pt (433.45): C, 49.88; H, 5.12. Found: C, 49.91; H, 5.22. 1H NMR (δ, CDCl3): 7.37 (m, 1H, o-Ph), 7.10 (m, 3H, m-Ph, p-Ph), 5.45 (m, 2H, CH COD(a), 2JPt,H = 34 Hz), 4.93 (m, 2H, CH COD(b), 2JPt,H = 49 Hz), 2.47 (s, 3H, o-CH3), 2.45 (m, 8H, CH2 COD), 1.08 (s, 3H, CH3, 2JPt,H = 77 Hz). 195Pt,1H HMBC (δ, CD2Cl2): −3100. λmax (THF): 250, 310 nm. [(COD)Pt(Me)(CC(2NO2)Ph)]: yield 54 mg (0.116 mmol, 41%). Anal. Calcd for C17H19NO2Pt (464.42): C, 43.97; H, 4.12; N, 3.02. Found: C, 43.91; H, 4.22; N, 3.00. 1H NMR (δ, CDCl3): 7.55− 7.42 (m, 3H, o-Ph, p-Ph), 7.34 (t, 1H, m-Ph), 5.47 (m, 2H, CH COD(a), 2JPt,H = 38 Hz), 5.22 (m, 2H, CH COD(b), 2JPt,H = 48
Hz), 2.45 (m, 8H, CH2 COD), 0.85 (s, 3H, CH3, 2JPt,H = 77 Hz). 195 Pt,1H HMBC (δ, CDCl3): −3054. IR (KBr in cm−1): 3060, 3021 (w): ν(CC−H); 2925, 2885 (s), 2836, 2801 (m): ν(H2C−H) and ν(HC−H); 2118, 2060 (s): ν(CC); 1631, 1608, 1523 (s): ν(C C(aryl)) and νas(NO2); 1475, 1455, 1432 (m): δ(H2C−H) and δ(HC−H); 1340 (s): δs(NO2); 997, 853, 848, 757 (m): δ(CC−H) and ν(C−N); 653 (m): δ(NO2). λmax (THF): 256, 309 (sh), 421 nm. [(COD)Pt(Me)(CC(3Me)Ph)]: yield 80 mg (0.185 mmol, 69%). Anal. Calcd for C18H22Pt (433.45): C, 49.88; H, 5.12. Found: C, 49.79; H, 5.05. 1H NMR (δ, CDCl3): 7.23 (s, 1H, o-Ph), 7.20 (d, 1H, o-Ph), 7.11 (t, 1H, m-Ph), 6.97 (d, 1H, p-Ph), 5.53 (m, 2H, CH COD(a), 2JPt,H = 35 Hz), 4.93 (m, 2H, CH COD(b), 2JPt,H = 49 Hz), 2.45 (m, 8H, CH2 COD), 2.28 (s, 3H, m-CH3), 1.05 (s, 3H, CH3, 2 JPt,H = 77 Hz). 195Pt,1H HMBC (δ, CDCl3): −3106. IR (KBr in cm−1): 3085, 3065, 3042, 3011 (w): ν(CC−H); 2948, 2922 (s), 2875, 2836 (m): ν(H2C−H) and ν(HC−H); 2111 (s): ν(CC); 1596, 1517 (s): ν(CC(aryl)); 1479, 1450, 1428 (s): δ(H2C−H) and δ(HC−H); 982, 917 (s), 860, 820 (m), 784, 757, 694 (s): δ(CC− H). EI-MS: 433 [M]+. λmax (THF): 257, 309 nm. [(COD)Pt(Me)(CC(3NO2)Ph)]: yield 74 mg (0.159 mmol, 56%). Anal. Calcd for C17H19NO2Pt (464.42): C, 43.97; H, 4.12; N, 3.02. Found: C, 43.89; H, 4.08; N, 2.99. 1H NMR (δ, CDCl3): 8.21 (s, 1H, o-Ph), 7.99 (d, 1H, p-Ph), 7.66 (d, 1H, o-Ph), 7.37 (t, 1H, m-Ph), 5.52 (m, 2H, CH COD, 2JPt,H 35 Hz), 5.00 (m, 2H, CH COD, 2JPt,H = 49 Hz), 2.47 (m, 8H, CH2 COD), 1.05 (s, 3H, CH3, 2 JPt,H = 77 Hz). 195Pt,1H HMBC (δ, CDCl3): −3122. IR (KBr in cm−1): 3078 (w): ν(CC−H); 2943, 2926, 2884 (s), 2838 (m): ν(H2C−H) and ν(HC−H); 2111 (s): ν(CC); 1611, 1567, 1526 (s): ν(CC(aryl)) and νas(NO2); 1473, 1428 (m): δ(H2C−H) and δ(HC−H); 1350 (s): δs(NO2); 994, 892, (m), 807, 732 (s): δ(C C−H) and ν(C−N); 673 (m): δ(NO2). EI-MS: 464 [M]+. λmax (THF): 257, 305 nm. [(COD)Pt(Me)(CC(4Me)Ph)]: yield 94 mg (0.221 mmol, 79%). Anal. Calcd for C18H22Pt (433.45): C, 49.88; H, 5.12. Found: C, 49.81; H, 5.12. 1H NMR (δ, CD2Cl2): 7.12 (d, 2H, o-Ph), 7.04 (d, 2H, m-Ph), 5.46 (m, 2H, CH COD(a), 2JPt,H = 37 Hz), 4.91 (m, 2H, CH COD(b), 2JPt,H = 50 Hz), 2.46−2.41 (m, 8H, CH2 COD, 3 JPt,H ≈ 10 Hz), 2.30 (s, 3H, p-CH3), 0.94 (s, 3H, CH3, 2JPt,H = 78 Hz). 195 Pt,1H HMBC (δ, CD2Cl2): −3209. 1H NMR (δ, DMF-d7): 7.18 (d, 2H, o-Ph), 7.09 (d, 2H, m-Ph), 5.40 (m, 2H, CH COD(a), 2JPt,H = 35 Hz), 4.94 (m, 2H, CH COD(b), 2JPt,H = 49 Hz), 2.46 (m, 8H, CH2 COD), 2.28 (s, 3H, 4-CH3), 0.91 (s, 3H, CH3, 2JPt,H = 79 Hz). 195 Pt,1H HMBC (δ, DMF-d7): −3114. IR (KBr in cm−1): 3074, 3049, 3033, 3012 (w): ν(CC−H); 2949, 2882 (s), 2835, 2802 (m): ν(H2C−H) and ν(HC−H); 2113 (s): ν(CC); 1600 (m), 1504 (s): ν(CC(aryl)); 1449, 1426 (s): δ(H2C−H) and δ(HC−H); 998, 978 (s), 942, 896, 860, 839 (m), 816, 784, 759 (s), 730, 706, 687 (m): δ(CC−H). EI-MS: 433 [M]+. λmax (THF): 255, 312 nm. [(COD)Pt(Me)(CC(4NO2)Ph)]: yield 44 mg (0.100 mmol, 33%). Anal. Calcd for C17H19N1O2Pt (464.42): C, 43.97; H, 4.12; N, 3.02. Found: C, 43.95; H, 4.12; N, 3.01. 1H NMR (δ, CD2Cl2): 8.08 (d, 2H, m-Ph), 7.43 (d, 2H, o-Ph), 5.46 (m, 2H, CH COD(a), 2JPt,H = 35 Hz), 5.00 (m, 2H, CH COD(b), 2JPt,H = 50 Hz), 2.46 (m, 8H, CH2 COD), 0.96 (s, 3H, CH3, 2JPt,H = 77 Hz). 195Pt,1H HMBC (δ, CD2Cl2): −3124. 1H NMR (δ, DMF-d7): 8.19 (d, 2H, m-Ph), 7.54 (d, 2H, o-Ph), 5.44 (m, 2H, CH COD(a), 2JPt,H = 36 Hz), 5.08 (m, 2H, CH COD(b), 2JPt,H = 50 Hz), 2.51 (m, 8H, CH2 COD), 0.92 (s, 3H, CH3, 2JPt,H = 78 Hz). 195Pt,1H HMBC (δ, DMF-d7): −3130. IR (KBr in cm−1): 3108, 3068 (w): ν(CC−H); 2924, 2882 (s), 2853, 2835 (m): ν(H2C−H) and ν(HC−H); 2111 (s): ν(CC); 1630, 1588, 1510 (s): ν(CC(aryl)) and νas(NO2); 1450, 1429, 1404, 1381 (m): δ(H2C−H) and δ(HC−H); 1340 (s): δs(NO2); 853, 750, 691 (m): δ(CC−H). λmax (THF): 229, 276, 358, 538 nm. [(COD)Pt(Me)(CC(4F)Ph)]: yield 110 mg (0.238 mmol, 84%). Anal. Calcd for C17H19FPt (437.42): C, 46.68; H, 4.38. Found: C, 46.66; H, 4.41. 1H NMR (δ, CD2Cl2): 7.28 (dd, 2H, o-Ph), 6.93 (dd, 2H, m-Ph), 5.46 (m, 2H, CH COD(a), 2JPt,H = 36 Hz), 4.92 (m, 2H, CH COD(b), 2JPt,H = 50 Hz), 2.44 (m, 8H, CH2 COD), 0.94 (s, 3H, CH3, 2JPt,H = 78 Hz). 195Pt,1H HMBC (δ, CD2Cl2): −3211. 19F 3670
dx.doi.org/10.1021/om400293u | Organometallics 2013, 32, 3662−3672
Organometallics
Article
NMR (δ, CD2Cl2): −116. IR (KBr in cm−1): 3092, 3039, 3008, 2990 (w): ν(CC−H); 2945, 2886 (s), 2835, 2801 (m): ν(H2C−H) and ν(HC−H); 2115 (s): ν(CC); 1597, 1586 (m), 1501 (s): ν(C C(aryl)); 1425, 1398, 1383 (m): δ(H2C−H) and δ(HC−H); 1220, 1201 (s): ν(C−F); 1007, 997, 981, 961, 944, 899, 862 (m), 838, 820, 783, 760, 743 (s), 689 (m): δ(CC−H); 531 (s): δ(C−F). EI-MS: 437 [M]+. λmax (THF): 250, 304 nm. [(COD)Pt(Me)(CC(4OMe)Ph)]: yield 86 mg (0.192 mmol, 68%). Anal. Calcd for C18H22OPt (449.44): C, 48.10; H, 4.93. Found: C, 48.05; H, 4.91. 1H NMR (δ, CDCl3): 7.33 (m, 2H, o-Ph), 6.77 (m, 2H, m-Ph), 5.53 (m, 2H, CH COD(a), 2JPt,H = 35 Hz), 4.91 (m, 2H, CH COD(b), 2JPt,H = 49 Hz), 3.78 (s, 3H, OCH3), 2.44 (m, 8H, CH2 COD), 1.05 (s, 3H, CH3, 2JPt,H = 77 Hz). 195Pt,1H HMBC (δ, CDCl3): −3105. IR (KBr in cm−1): 3033, 3005 (w): ν(CC−H); 2951, 2930, 2882, 2836 (m): ν(H2C−H) and ν(HC−H); 2114 (s): ν(CC); 1598, 1505 (s): ν(CC(aryl)); 1465, 1443, 1428 (m): δ(H2C−H) and δ(HC−H); 1288, 1244, 1167, 1027 (s): ν(C−OC); 996, 980, 862 (m), 835 (s), 763, 732, 695 (m): δ(CC−H). λmax (THF): 257, 318 nm. [(COD)Pt(Me)(CC(2Py)]: yield 71 mg (0.168 mmol, 63%). Anal. Calcd for C16H19NPt (407.39): C, 44.22; H, 4.45; N, 3.44. Found: C, 44.20; H, 4.43; N, 3.42. 1H NMR (δ, CDCl3): 8.49 (d, 1H, 6-Py), 7.52 (dt, 1H, 4-Py), 7.34 (d, 1H, 3-Py), 7.04 (d, 1H, 5-Py), 5.57 (m, 2H, CH COD(a), 2JPt,H = 36 Hz), 4.97 (m, 2H, CH COD(b), 2JPt,H = 49 Hz), 2.44 (m, 8H, CH2 COD, 3JPt,H ≈ 17 Hz), 1.06 (s, 3H, CH3, 2JPt,H = 77 Hz). 195Pt,1H HMBC (δ, CDCl3): −3121. IR (KBr in cm−1): 3069, 3052, 3003 (w): ν(CC−H); 2923, 2878 (s), 2833, 2798 (m): ν(H2C−H) and ν(HC−H); 2100, 2063 (s): ν(CC); 1592, 1550 (s): ν(CC(aryl)); 1465, 1423 (s): δ(H2C− H) and δ(HC−H); 846, 802 (m), 766, 743, 714, 699 (m): δ(CC− H). EI-MS: 407 [M]+ λmax (THF): 251, 296 nm. Synthesis of [(COD)Pt(R′)(CC(4Me)Ph)] (R′ = Bz, Neop, or NeoSi). The compounds were prepared as described for the R′ = Me derivatives starting from 0.28 mmol of the [(COD)Pt(R′)Cl] precursors. [(COD)Pt(Bz)(CC(4Me)Ph)]: yield 115 mg (0.227 mmol, 81%). Anal. Calcd. for C24H26Pt (509.54): C, 56.57; H, 5.14. Found: C, 56.61; H, 5.12. 1H NMR (δ, CD2Cl2): 7.26 (d, 2H, o-PhBz), 7.22 (d, 2H, o-PhCC), 7.14 (d, 2H, m-PhBz), 7.06 (d, 2H, m-PhCC), 6.95 (t, 1H, p-PhBz), 5.51 (m, 2H, =CH COD(a), 2JPt,H = 39 Hz), 4.84 (m, 2H, CH COD(b), 2JPt,H = 47 Hz), 3.20 (s, 2H, CH2Bz, 2JPt,H = 106 Hz) 2.39 (m, 8H, CH2 COD, 3JPt,H ∼ 10 Hz), 2.31 (s, 3H, p-CH3). 195 Pt,1H HMBC (δ, CD2Cl2): −3106. IR (KBr in cm−1): 3069, 3048, 3020, 3001 (w): ν(CC−H); 2962, 2919, 2878, 2831 (m): ν(H2C− H) and ν(HC−H); 2118 (s): ν(CC); 1592 (m), 1504, 1487 (s): ν(CC(aryl)); 1445, 1428 (m): δ(H2C−H) and δ(HC−H); 990, 864 (m), 817, 802, 764, 702 (s): δ(CC−H). EI-MS: 509 [M]+. λmax (THF): 251, 321 nm. [(COD)Pt(Neop)(CC(4Me)Ph)]: yield 116 mg (0.238 mmol, 85%). Anal. Calcd. for C22H30Pt (489.55): C, 53.97; H, 6.18. Found: C, 53.91; H, 6.16. 1H NMR (δ, CDCl3): 7.25 (d, 2H, o-Ph), 7.03 (d, 2H, m-Ph), 5.54 (m, 2H, CH COD(a), 2JPt,H = 32 Hz), 4.87 (m, 2H, CH COD(b), 2JPt,H = 48 Hz), 2.42 (m, 8H, CH2 COD), 2.30 (s, 3H, p-CH3), 1.88 (s, 2H, CH2Neop, 2JPt,H = 87 Hz), 1.14 (s, 9H, C(CH3)3). 195Pt, 1H HMBC (δ, CDCl3): −3102. IR (KBr in cm−1): 3072, 3043, 3021, 3002 (w): ν(CC−H); 2945, 2924, 2883, 2856 (s): ν(H2C−H) and ν(HC−H); 2113 (s): ν(CC); 1607 (m), 1504 (s): ν(CC(aryl)); 1465, 1452, 1428 (s), 1354, 1348 (m): δ(H2C− H) and δ(HC−H); 986, 861 (m), 817 (s), 784, 763 (m): δ(CC− H). EI-MS: 489 [M]+. λmax (THF): 257, 317 nm. [(COD)Pt(NeoSi)(CC(4Me)Ph)]: yield 112 mg (0.221 mmol, 79%). Anal. Calcd. for C21H30PtSi (505.63): C, 49.88; H, 5.98. Found: C, 49.81; H, 5.99. 1H NMR (δ, CDCl3): 7.27 (d, 2H, o-Ph), 7.03 (d, 2H, m-Ph), 5.41 (m, 2H, CH COD(a), 2JPt,H = 38 Hz), 4.93 (m, 2H, CH COD(b), 2JPt,H = 49 Hz), 2.42 (m, 8H, CH2 COD), 2.30 (s, 3H, p-CH3), 1.14 (s, 2H, CH2NeoSi, 2JPt,H = 89 Hz), 0.12 (s, 9H, Si(CH3)3). 195Pt, 1H HMBC (δ, CDCl3): −3056. IR (KBr in cm−1): 3076, 3046, 3026, 3002 (w): ν(CC−H); 2943, 2923, 2889, 2870, 2837 (s): ν(H2C−H) and ν(HC−H); 2123 (s): ν(CC); 1605 (m), 1507 (s): ν(CC(aryl)); 1428 (s): δ(H2C−H) and δ(HC−H); 996,
983, 966 (m), 853, 828, 814 (s), 774, 719 (m): δ(CC−H). EI-MS: 505 [M]+. λmax (THF): 255, 317 nm.
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ASSOCIATED CONTENT
S Supporting Information *
Figures S1−S25, Tables S1−S48, and a CIF file, giving additional electrochemical, spectroscopic, and structural information. This material is available free of charge via the Internet at http://pubs.acs.org.
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS We are indebted to Dr. Ingo Pantenburg and Miss Ingrid Müller for single-crystal XRD measurements, as well as to Dr. Wieland Tyrra for NMR experiments (all at the University of Cologne). We are also grateful for a loan of K2PtCl4 by Johnson Matthey (JM) and for financial support by the Deutsche Forschungsgemeinschaft (projects FOR-630 (I.O.) and KL 1194/11-1 (A.L. and A.K)).
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REFERENCES
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