Platinum(IV) Complexes with Chelating N-Heterocyclic Carbene Ligands

Jul 8, 2010 - exes in good yields under very mild reaction conditions. All compounds have ... (12) Jung, I. G.; Seo, J.; Lee, S. I.; Choi, S. Y.; Chun...
2 downloads 0 Views 812KB Size
Download PDF
3392

Organometallics 2010, 29, 3392–3396 DOI: 10.1021/om100488s

Platinum(IV) Complexes with Chelating N-Heterocyclic Carbene Ligands Dirk Meyer, Sebastian Ahrens, and Thomas Strassner* Physikalische Organische Chemie, TU Dresden, Bergstrasse 66, 01062 Dresden, Germany Received May 18, 2010

Platinum(II) complexes with one or two chelating bis(NHC) ligands have been oxidized by bromine as well as iodobenzene dichloride to provide the corresponding platinum(IV) carbene complexes in good yields under very mild reaction conditions. All compounds have been fully characterized by 1H and 13C NMR spectroscopy and in three cases also by solid-state structures. The NMR spectra of the novel Pt(IV) complexes show significantly shifted signals compared to their Pt(II) precursor complexes.

Introduction Platinum(II) complexes of N-heterocyclic carbenes (NHC) have attracted considerable attention during the last years, especially complexes with chelating bis(NHC) ligands, which show an increased stability against oxidizing and acidic *Corresponding author. Tel: þ49 351 46338571. Fax: þ49 351 46339679. E-mail: [email protected]. (1) Ahrens, S.; Herdtweck, E.; Goutal, S.; Strassner, T. Eur. J. Inorg. Chem. 2006, 1268. (2) Ahrens, S.; Strassner, T. Inorg. Chim. Acta 2006, 359, 4789. (3) Strassner, T.; Ahrens, S.; Zeller, A. WO 2006058535, 2006. (4) Liu, Q.-X.; Song, H.-B.; Xu, F.-B.; Li, Q.-S.; Zeng, X.-S.; Leng, X.-B.; Zhang, Z.-Z. Polyhedron 2003, 22, 1515. (5) Quezada, C. A.; Garrison, J. C.; Tessier, C. A.; Youngs, W. J. J. Organomet. Chem. 2003, 671, 183. (6) Baker, M. V.; Brown, D. H.; Simpson, P. V.; Skelton, B. W.; White, A. H.; Williams, C. C. J. Organomet. Chem. 2006, 691, 5845. (7) Lillo, V.; Mata, J. A.; Segarra, A. M.; Peris, E.; Fernandez, E. Chem. Commun. 2007, 2184. (8) Strassner, T.; Unger, Y.; Zeller, A. WO 2008000726, 2008. (9) Unger, Y.; Zeller, A.; Ahrens, S.; Strassner, T. Chem. Commun. 2008, 3263. (10) Boydston, A. J.; Rice, J. D.; Sanderson, M. D.; Dykhno, O. L.; Bielawski, C. W. Organometallics 2006, 25, 6087. (11) Hahn, F. E.; Jahnke, M. C.; Pape, T. Organometallics 2006, 25, 5927. (12) Jung, I. G.; Seo, J.; Lee, S. I.; Choi, S. Y.; Chung, Y. K. Organometallics 2006, 25, 4240. (13) Poyatos, M.; Maisse-Francois, A.; Bellemin-Laponnaz, S.; Gade, L. H. Organometallics 2006, 25, 2634. (14) Berthon-Gelloz, G.; Buisine, O.; Briere, J.-F.; Michaud, G.; Sterin, S.; Mignani, G.; Tinant, B.; Declercq, J.-P.; Chapon, D.; Marko, I. E. J. Organomet. Chem. 2005, 690, 6156. (15) Froseth, M.; Netland, K. A.; Romming, C.; Tilset, M. J. Organomet. Chem. 2005, 690, 6125. (16) Bacciu, D.; Cavell, K. J.; Fallis, I. A.; Ooi, L.-l. Angew. Chem., Int. Ed. 2005, 44, 5282. (17) Green, J. C.; Herbert, B. J. Dalton Trans. 2005, 1214. (18) Liu, Q.-X.; Xu, F.-B.; Li, Q.-S.; Song, H.-B.; Zhang, Z.-Z. J. Mol. Struct. 2004, 697, 131. (19) Hasan, M.; Kozhevnikov, I. V.; Siddiqui, M. R. H.; Steiner, A.; Winterton, N. J. Chem. Res., Synop. 2000, 392. (20) Balch, A. L.; Parks, J. E. J. Am. Chem. Soc. 1974, 96, 4114. (21) Frankel, R.; Kniczek, J.; Ponikwar, W.; Noth, H.; Polborn, K.; Fehlhammer, W. P. Inorg. Chim. Acta 2001, 312, 23. (22) Muehlhofer, M.; Strassner, T.; Herdtweck, E.; Herrmann, W. A. J. Organomet. Chem. 2002, 660, 121. pubs.acs.org/Organometallics

Published on Web 07/08/2010

media, therefore tolerating harsher reaction conditions compared to catalysts with phosphine ligands.1-31 In contrast, only a few examples for Pt(IV) carbene complexes32-42 are known and even less for Pt(IV) NHC complexes39-42 (Figure 1). Pt(IV) complexes 1, 2 (R1-R4 = H, Me, Alkyl, Ph, COR, COOR) and 3a-c (X = NMe, O, S) with monodentate NHC ligands are prepared by ligand substitution from Pt(IV) precursors,39-41 while the only examples with a chelating (23) Brissy, D.; Skander, M.; Jullien, H.; Retailleau, P.; Marinetti, A. Org. Lett. 2009, 11, 2137. (24) Hu, J. J.; Li, F.; Hor, T. S. A. Organometallics 2009, 28, 1212. (25) Frankel, R.; Kernbach, U.; Bakola-Christianopoulou, M.; Plaia, U.; Suter, M.; Ponikwar, W.; Noth, H.; Moinet, C.; Fehlhammer, W. P. J. Organomet. Chem. 2001, 617-618, 530. (26) Fantasia, S.; Petersen, J. L.; Jacobsen, H.; Cavallo, L.; Nolan, S. P. Organometallics 2007, 26, 5880. (27) Hasan, M.; Kozhevnikov, I. V.; Siddiqui, M. R. H.; Femoni, C.; Steiner, A.; Winterton, N. Inorg. Chem. 2001, 40, 795. (28) McGuinness, D. S.; Yates, B. F.; Cavell, K. J. Chem. Commun. 2001, 355. (29) McGuinness, D. S.; Cavell, K. J.; Yates, B. F.; Skelton, B. W.; White, A. H. J. Am. Chem. Soc. 2001, 123, 8317. (30) Newman, C. P.; Deeth, R. J.; Clarkson, G. J.; Rourke, J. P. Organometallics 2007, 26, 6225. (31) Meyer, A.; Taige, M. A.; Strassner, T. J. Organomet. Chem. 2009, 694, 1861. (32) Zhang, S.-W.; Takahashi, S. Organometallics 1998, 17, 4757. (33) Rendina, L. M.; Vittal, J. J.; Puddephatt, R. J. Organometallics 1995, 14, 1030. (34) Hartshorn, A. J.; Lappert, M. F.; Turner, K. J. Chem. Soc., Dalton Trans. 1978, 348. (35) Chatt, J.; Richards, R. L.; Royston, G. H. D. J. Chem. Soc., Dalton Trans. 1976, 599. (36) Walker, R.; Muir, K. W. J. Chem. Soc., Dalton Trans. 1975, 272. (37) Chisholm, M. H.; Clark, H. C.; Johns, W. S.; Ward, J. E. H.; Yasufuku, K. Inorg. Chem. 1975, 14, 900. (38) Balch, A. L. J. Organomet. Chem. 1972, 37, C19. (39) Demidov, V. N.; Kukushkin, Y. N.; Vedeneeva, L. N.; Belyaev, A. N. Zh. Obshch. Khim. 1988, 58, 738. (40) Weigand, W.; Nagel, U.; Beck, W. Z. Naturforsch., B: Chem. Sci. 1988, 43, 328. (41) Lindner, R.; Wagner, C.; Steinborn, D. J. Am. Chem. Soc. 2009, 131, 8861. (42) Prokopchuk, E. M.; Puddephatt, R. J. Organometallics 2003, 22, 563. (43) Stahl, S. S.; Labinger, J. A.; Bercaw, J. E. J. Am. Chem. Soc. 1996, 118, 5961. r 2010 American Chemical Society

Article

Organometallics, Vol. 29, No. 15, 2010

3393

Figure 1. Pt(IV) NHC complexes reported by Belyaev (1),39 Beck (2),40 Steinborn (3a-c),41 and Puddephatt (4a, 4b).42 Scheme 1. Synthesis of [Pt(DMMDI)Br4] (8) and [Pt(DMMDI)2Br2]Br2 (9) by Oxidative Addition of Brominea

Table 1. 1H and 13C NMR Signals of Complexes 6-9 (δ in ppm)

NMR signal CH3 N-CH2-N NCHCHN NCHCHN Pt-C

a Reagents and reaction conditions: (a) Pt(acac)2, DMSO, 100 °C, 15 h; (b) Br2, CH2Cl2, -78 °C, 5 min.; (c) Pt(acac)2, NaOAc, DMSO, 60-110 °C, 32 h; (d) Br2, CH2Cl2, -78 °C, 30 min.

NHC ligand (4a, 4b) have been synthesized by oxidative addition of methyl iodide or triflic acid.42 To the best of our knowledge, no Pt(IV) complexes with chelating bis(NHC) ligands have been reported before. We set out to synthesize Pt(IV) NHC complexes as part of our studies on the activation of alkanes by Pd(II) and Pt(II) NHC complexes.2,44 We have shown that platinum(II) bis(NHC) complexes are able to activate the CH bonds in methane,2 and Pt(IV) complexes might be key intermediates in the catalytic methane activation cycle. We therefore studied the oxidation of platinum(II) bis(NHC) complexes and present the first synthesis of stable platinum(IV) bis(NHC) complexes by oxidative addition of bromine or chlorine (from iodobenzene dichloride) at low temperature.

Results and Discussion Oxidation of Platinum(II) Bis(NHC) Complexes by Bromine. The synthesis of Pt(IV) complexes by oxidative addition of (44) Muehlhofer, M.; Strassner, T.; Herrmann, W. A. Angew. Chem., Int. Ed. 2002, 41, 1745. (45) Werner, M.; Wagner, C.; Steinborn, D. J. Organomet. Chem. 2009, 694, 190.

complex 655

complex 8

complex 755

complex 9

1

1

1

1

H

3.84 5.96 6.10 7.31 7.53

13

C

37.6 61.8 120.3 122.5 144.8

H

13

C

4.22 41.0 6.45 62.8 6.85 7.57 122.9 7.63 125.7 118.9

H

3.33 6.45 6.55 7.48 7.76

13

C

36.6 62.6 122.1 123.0 162.8

H

13

C

4.20 38.1 6.83 62.8 6.95 7.77 124.5 7.93 125.5 131.1

bromine has been known for some years,45-53 and it was recently shown that also Au(I) NHC complexes can be oxidized by bromine.54 A similar protocol can also be used for the oxidative addition of bromine to the Pt(II) bis(NHC) complexes [Pt(DMMDI)Br2] (6) and [Pt(DMMDI)2]Br2 (7) (Scheme 1), which were synthesized by reaction of 1,10 -dimethyl-3,30 methylenediimidazolium dibromide ((H2DMMDI)Br2) (5) with platinum(II) acetylacetonate, as previously reported.55 The addition of bromine is achieved in almost quantitative yields at low temperatures of -78 °C. The Pt(IV) NHC complexes [Pt(DMMDI)Br4] (8) and [Pt(DMMDI)2Br2]Br2 (9) are stable toward air and moisture at room temperature. According to TGA measurements (see Supporting Information), reductive elimination of bromine from 8 was observed at temperatures of around 300 °C. The oxidation of the Pt(II) complexes to Pt(IV) complexes also leads to significant changes in the 1H and 13C NMR spectra (Table 1). (46) Crossley, I. R.; Hill, A. F.; Willis, A. C. Organometallics 2008, 27, 312. (47) Jones, R. C.; Skelton, B. W.; Tolhurst, V.-A.; White, A. H.; Wilson, A. J.; Canty, A. J. Polyhedron 2007, 26, 708. (48) Chanda, N.; Sharp, P. R. Organometallics 2007, 26, 3368. (49) Bennett, M. A.; Bhargava, S. K.; Messelhaeuser, J.; Priver, S. H.; Welling, L. L.; Willis, A. C. Dalton Trans. 2007, 3158. (50) Kawakami, D.; Yamashita, M.; Matsunaga, S.; Takaishi, S.; Kajiwara, T.; Miyasaka, H.; Sugiura, K.-i.; Matsuzaki, H.; Okamoto, H.; Wakabayashi, Y.; Sawa, H. Angew. Chem., Int. Ed. 2006, 45, 7214. (51) Appleton, T. G.; Berry, R. D.; Hall, J. R.; Neale, D. W. J. Organomet. Chem. 1988, 342, 399. (52) Vicente, J.; Chicote, M. T.; Martin, J.; Jones, P. G.; Fittschen, C. J. Chem. Soc., Dalton Trans. 1987, 881. (53) Chassot, L.; Von Zelewsky, A. Helv. Chim. Acta 1986, 69, 1855. (54) De Fremont, P.; Singh, R.; Stevens, E. D.; Petersen, J. L.; Nolan, S. P. Organometallics 2007, 26, 1376. (55) Unger, Y.; Zeller, A.; Taige, M. A.; Strassner, T. Dalton Trans. 2009, 4786–4794.

3394

Organometallics, Vol. 29, No. 15, 2010

Meyer et al. Scheme 2. Synthesis of the Pt(IV) Complexes [Pt(DMMDI)Cl4] (13) and [Pt(DMMDI)2Cl2](PF6)2 (14)a

Figure 2. ORTEP plot of complex 9 3 2H2O in the solid state. Thermal ellipsoids are drawn at the 50% probability level. Two solvent molecules (water) have been omitted for clarity. Table 2. Selected Bond Lengths (A˚) and Angles (deg) of [Pt(DMMDI)2Br2]Br2 (9 3 2H2O) and [Pt(DMMDI)2Cl2](PF6)2 (14 3 2DMSO) Pt-Hal Pt-C1 Pt-C6 C1-Pt-C6 Cl-Pt-Hal C6-Pt-Hal

9 3 2H2O

14 3 2DMSO

2.486(2) 2.071(4) 2.079(4) 84.69(13) 87.42(9) 85.93(9)

2.330(1) 2.065(2) 2.072(2) 84.03(7) 87.12(5) 87.16(5)

With the exception of the 13C signals of the carbene carbon atoms, almost all 1H and 13C NMR signals of Pt(IV) complexes are shifted to lower field compared to the corresponding Pt(II) complexes. Obviously the change in oxidation state shows the most pronounced effect at the carbene carbon atoms; their signals are shifted by more than 25 ppm (25.8 ppm 6 vs 8 and 31.7 ppm 7 vs 9) to higher field. Crystals suitable for X-ray diffraction studies were obtained by a slow diffusion of THF into a DMSO solution. From this solution we could isolate crystals of complex 9 3 2H2O (Figure 2). The coordination of two biscarbene ligands and two bromides leads to a slightly distorted, octahedral coordination geometry. The equatorial positions are occupied by the four carbene carbon atoms, the C-Pt bond lengths (2.07 and 2.08 A˚) being slightly elongated compared to the corresponding Pt(II) tetracarbene complexes (2.03 A˚).9,55 The two bromido ligands are coordinated in the axial positions with bond lengths of 2.49 A˚. Similar bond lengths have been reported for Pt(II) biscarbene bromide complexes.22 The two bromide anions of [Pt(DMMDI)2Br2]Br2 (9) are noncoordinating in the crystal lattice around the dicationic complex. Selected bond lengths and angles are given in Table 2. Oxidation of Platinum(II) Bis(NHC) Complexes with Iodobenzene Dichloride. Recently Sanford et al. reported the oxidation of Pt(II) bis(2-phenylpyridine) complexes by iodobenzene dichloride.56 While in their case the major product is the unsymmetrical derivative formed by oxidative cisaddition, oxidation of the Pt(II) tetracarbene complex 12 with iodobenzene dichloride exclusively affords the product of an oxidative trans-addition, [Pt(DMMDI)2Cl2](PF6)2 (14) (Scheme 2). (56) Whitfield, S. R.; Sanford, M. S. Organometallics 2008, 27, 1683.

a Reagents and reaction conditions: (a) Pt(acac)2, DMSO, 100 °C, 19 h; (b) Ph-ICl2, CH2Cl2, rt, 14 h; (c) Pt(acac)2, NaOAc, DMSO, 60-110 °C, 32 h; (d) AgPF6, MeCN, 60 °C, 9 h; (e) Ph-ICl2, CH2Cl2, rt, 14 h.

Figure 3. ORTEP plot of 14 3 2DMSO in the solid state. Thermal ellipsoids are drawn at the 50% probability level. Two solvent molecules (DMSO) have been omitted for clarity.

Starting from the bisimidazolium salt 10 we used the wellestablished route to synthesize the platinum(II) biscarbene complex 11,2 which could easily be oxidized by iodobenzene dichloride to form [Pt(DMMDI)Cl4] (13) in good yields. The two [PtIV(DMMDI))X4] complexes 8 and 13 allow us to study the influence of the chlorido and bromido ligands. As expected, both complexes show similar NMR spectra, which indicates that the change of the oxidation state has a much stronger influence than the halogen ligand. Both complexes also show a comparable stability according to the TGA spectra (see Supporting Information). Unfortunately we have not been able to synthesize the platinum(II) tetracarbene dichloride complex [Pt(DMMDI)2]Cl2. We therefore used the dibromide complex 7 and exchanged the counterions against noncoordinating PF6anions to avoid anion scrambling. We obtained complex 12 in 94% yield, which could be oxidized by iodobenzene dichloride to 14 at room temperature in almost quantitative yield. The symmetrical NMR signal set of 14 indicated that the chlorido ligands are in axial position, which was confirmed by the solid-state structure of 14 3 2DMSO (Figure 3). Except for the Pt-X distance, which is of course shorter for

Article

Organometallics, Vol. 29, No. 15, 2010 Table 3. Selected Bond Lengths and Angles of 13 bond length (A˚)

Pt1-C1 Pt1-C6 Pt1-Cl4 Pt1-Cl3 Pt1-Cl2 Pt1-Cl1

2.006(6) 2.031(6) 2.321(2) 2.330(2) 2.379(2) 2.385(1)

angle (deg) C1-Pt1-C6 C1-Pt1-Cl3 C1-Pt1-Cl4 Cl4-Pt1-Cl3 Cl2-Pt1-Cl1 Cl3-Pt1-Cl1

86.2(2) 91.08(17) 89.96(17) 178.92(6) 86.32(5) 87.07(5)

Figure 4. ORTEP plot of complex 13 in the solid state. Thermal ellipsoids are drawn at the 50% probability level.

the chlorido ligands, bond lengths and angles of 14 are quite similar to those of complex 9 (Table 2). We also could get a solid-state structure of 13 (Figure 4); selected bond lengths and angles are given in Table 3. The distances of the axial chlorido ligands to the metal center are similar to those observed for complex 14 (Pt1-Cl3 2.33 A˚ and Pt1-Cl4 2.32 A˚ in 13 vs Pt1-Cl1 2.33 A˚ in 14). Comparing [Pt(DMMDI)Cl4] (13) (Figure 4) with the corresponding Pt(II) complex [Pt(DMMDI)Cl2] (11), it is interesting to note that the change of the oxidation state does not influence the bond length to the equatorial chlorido ligands (2.38 A˚ in 13 vs 2.37 A˚ in the Pt(II) biscarbene complex 11),2 while the Pt-C distances differ significantly (Pt1-C1 2.01 A˚ and Pt1-C6 2.03 A˚ in 13 vs 1.94 and 1.95 A˚ in the Pt(II) complex 11). The bite angle of the chelating biscarbene ligand (86.2°) in 13 is similar to published values of bis- and tetracarbene ligands.2,9

Conclusion We present the synthesis and structural characterization of the first stable Pt(IV) NHC complexes containing one or two chelating NHC ligands. Oxidation was achieved by bromine and by iodobenzene dichloride. Signals for the carbene carbon atom in the 13C NMR spectra are strongly influenced by the change of the oxidation state at the metal center. X-ray structures confirm the trans-orientation of the oxidatively added bromido and chlorido ligands in the Pt(IV) tetracarbene complexes 9 and 14. Investigation of the oxidative addition of methyl halogenides to Pt(II) complexes is currently under way in our laboratories.

Experimental Section 1 H and 13C NMR spectra were obtained on a Bruker DRX300 at 300.13 and 75.453 MHz, respectively. Elemental analyses were performed by the microanalytical laboratory of our institute using an EuroVektor Euro EA-300 elemental analyzer. TGAs were performed on a NETZSCH STA 409 system. Chemicals

3395

were supplied by Acros, Fluka, and Aldrich. Solvents were dried by standard procedures before use. The bisimidazolium salts 1,10 -dimethyl-3,30 -methylenediimidazolium dibromide (H2(DMMDI)Br2, 5)22 and 1,10 -dimethyl-3,30 -methylenediimidazolium dichloride (H2(DMMDI)Cl2, 10)57 and the platinum(II) complexes dibromido(1,10 -dimethyl-3,30 -methylenediimidazolin-2,20 -ylidene)platinum(II) ([Pt(DMMDI)Br2], 6),55 bis(1,10 dimethyl-3,30 -methylenediimidazolin-2,20 -ylidene)platinum(II) dibromide ([Pt(DMMDI)2]Br2, 7),55 and dichlorido(1,10 -dimethyl3,30 -methylenediimidazolin-2,20 -ylidene)platinum(II) ([Pt(DMMDI)Cl2], 11)2 as well as iodobenzene dichloride58 were prepared according to literature procedures. Tetrabromido(1,10 -dimethyl-3,30 -methylenediimidazolin-2,20 ylidene)platinum(IV), [Pt(DMMDI)Br4], 8. A 2 mL amount of dichloromethane is added to 0.050 g (0.09 mmol) of [Pt(DMMDI)Br2], 6. The suspension is cooled to -78 °C, and 0.030 g (0.19 mmol) of bromine is added dropwise. After stirring at -78 °C for 5 min, the solvent and the excess bromine are removed in vacuo, yielding the solid product (0.063 g, 93%). 1 H NMR (DMSO-d6, 298K, ppm): δ 4.22 (s, 6H, CH3), 6.45 (d, J = 13.4 Hz, 1H, NCH2N), 6.85 (d, J = 13.4 Hz, 1H, NCH2N), 7.57 (d, J = 3.0 Hz, 2H, NCHCHN), 7.63 (d, 3.0 Hz, 2H, NCHCHN). 13C NMR (DMSO-d6, 298 K, ppm): δ 41.0 (CH3), 62.8 (NCH2N), 118.9 (C-Pt), 122.9 (NCHCHN), 125.7 (NCHCHN). Anal. Calcd for C9H12Br4N4Pt: C 15.65; H 1.75; N 8.11. Found: C 15.62; H 1.45; N 7.95. Dibromidobis(1,10 -dimethyl-3,30 -methylenediimidazolin-2,20 ylidene)platinum(IV) dibromide, [Pt(DMMDI)2Br2]Br2, 9. A 2 mL portion of dichloromethane is added to 0.039 g (0.06 mmol) of [Pt(DMMDI)2]Br2, 7. The suspension is cooled to -78 °C, and 0.018 g (0.11 mmol) of bromine is added dropwise. After stirring at -78 °C for 30 min, the solvent and the excess bromine are removed in vacuo, yielding the solid product (0.049 g, 100%). 1 H NMR (DMSO-d6, 298 K, ppm): δ 4.20 (br s, 12H, CH3), 6.83 (d, J = 14.0 Hz, 2H, NCH2N), 6.95 (d, J = 14.0 Hz, 2H, NCH2N), 7.77 (d, J = 2.0 Hz, 4H, NCHCHN), 7.93 (d, 2.0 Hz, 4H, NCHCHN). 13C NMR (DMSO-d6, 298 K, ppm): δ 38.1 (CH3), 62.8 (NCH2N), 124.5 (NCHCHN), 125.5 (NCHCHN), 131.1 (C-Pt). Bis(1,10 -dimethyl-3,30 -methylenediimidazolin-2,20 -ylidene)platinum(II) Bis(hexafluorophosphate), [Pt(DMMDI)2](PF6)2, 12. A 0.200 g (0.28 mmol) sample of [Pt(DMMDI)2]Br2 (7) and 0.157 g (0.62 mmol) of silver hexafluorophosphate are suspended in 10 mL of acetonitrile. The reaction mixture is stirred for 9 h at 60 °C under exclusion of light. After cooling to room temperature the suspension formed is filtered through Celite. The solution is concentrated to 2 mL, and the product is precipitated by addition of 10 mL of diethyl ether. After filtration, the product is washed with diethyl ether, yielding a white powder (0.223 g, 94%). 1 H NMR (DMSO-d6, 298 K, ppm): δ 3.35 (s, 12H, CH3), 6.41 (d, J=13.2 Hz, 2H, NCH2N), 6.48 (d, J=13.2 Hz, 2H, NCH2N), 7.47 (d, J = 2.0 Hz, 4H, NCHCHN), 7.75 (d, 2.0 Hz, 4H, NCHCHN). 13C NMR (DMSO-d6, 298 K, ppm): δ 36.6 (CH3), 62.6 (NCH2N), 122.1 (NCHCHN), 123.0 (NCHCHN), 162.8 (C-Pt). 19F NMR (DMSO-d6, 298 K, ppm): δ -68.85, -71.37. Anal. Calcd for C18H24F12N8P2Pt: C 25.82; H 2.89; N 13.38. Found: C 25.43; H 2.54; N 13.25. Tetrachlorido(1,10 -dimethyl-3,30 -methylenediimidazolin-2,20 ylidene)platinum(IV) [Pt(DMMDI)Cl4], 13. A 0.050 g (0.11 mmol) amount of [Pt(DMMDI)Cl2] (11) is suspended in 10 mL of dichloromethane. After addition of 0.037 g (0.14 mmol) of iodobenzene dichloride, the solution is stirred overnight at room temperature. The solvent is removed in vacuo, and the residue is washed with methanol and THF, yielding the product as a white solid (0.040 g, 71%). (57) Ahrens, S.; Zeller, A.; Taige, M.; Strassner, T. Organometallics 2006, 25, 5409. (58) Zhao, X.-F.; Zhang, C. Synthesis 2007, 551.

3396

Organometallics, Vol. 29, No. 15, 2010

H NMR (DMSO-d6, 298 K, ppm): δ 4.23 (s, 6H, CH3), 6.51 (d, J = 13.3 Hz, 1H, NCH2N), 6.75 (d, J = 13.2 Hz, 1H, NCH2N), 7.64 (d, J = 1.6 Hz, 2H, NCHCHN), 7.73 (d, 1.6 Hz, 2H, NCHCHN). 13C NMR (DMSO-d6, 298 K, ppm): δ 39.0 (CH3), 61.9 (NCH2N), 119.4 (C-Pt), 123.0 (NCHCHN), 125.6 (NCHCHN). Anal. Calcd for C9H12Cl4N4Pt 3 0.15H2O: C 20.96; H 2.40; N 10.86. Found: C 20.49; H 2.01; N 11.36. Dichloridobis(1,10 -dimethyl-3,30 -methylenediimidazolin-2,20 ylidene)platinum(IV) Bis(hexafluorophosphate), [Pt(DMMDI)2Cl2](PF6)2, 14. A 0.044 g (0.06 mmol) portion of [Pt(DMMDI)2](PF6)2 (12) is suspended in 10 mL of dichloromethane. After addition of 0.020 g (0.14 mmol) of iodobenzene dichloride, the solution is stirred overnight at room temperature. The solvent is removed in vacuo, and the residue is washed with methanol and THF, yielding the product as a white solid (0.051 g, 94%). 1 H NMR (DMSO-d6, 298 K, ppm): δ 3.57 (s, 12H, CH3), 6.75 (d, J = 13.8 Hz, 2H, NCH2N), 6.89 (d, J = 13.6 Hz, 2H, NCH2N), 7.74 (d, J = 1.7 Hz, 4H, NCHCHN), 7.92 (d, 1.6 Hz, 4H, NCHCHN). 13C NMR (DMSO-d6, 298 K, ppm): δ 36.9 (CH3), 62.1 (NCH2N), 124.4 (NCHCHN), 125.3 (NCHCHN), 133.3 (C-Pt). Anal. Calcd for C18H24Cl2N8F12P2Pt 3 0.35CH2Cl2: C 23.49; H 2.65; N 11.94. Found: C 23.09; H 2.49; N 12.31. Solid-State Structure Determination of 9, 13, and 14. Crystals were obtained by condensing THF into a saturated DMSO solution of the complexes. Preliminary examination and data collection were carried out on an area detecting system (KappaCCD; Nonius) at the window of a sealed X-ray tube (Nonius, FR590) with graphite-monochromated Mo KR radiation (λ = 0.72073 A˚). The reflections were integrated. Raw data were corrected for Lorentz and polarization and, arising from the scaling procedure, for latent decay. An absorption correction was applied using SADABS.59 After merging, the independent reflections were all used to refine the structure. The structures were solved by a combination of direct methods and difference Fourier synthesis. All non-hydrogen atoms were refined with anisotropic displacement parameters. All hydrogen atoms were placed in calculated positions and refined using the riding model. Full-matrix P least-squares refinements were carried out by minimizing w(Fo2 - Fc2)2. Details of the structure determinations 1

(59) Sheldrick, G. M. SADABS, Version 2.10; University of Goettingen: Goettingen, Germany, 2003.

Meyer et al. are given in the Supporting Information. Neutral atom scattering factors for all atoms and anomalous dispersion corrections for the non-hydrogen atoms were taken from the International Tables for Crystallography.60 All calculations were performed with the SHELXL-9761package and the programs COLLECT,62 DIRAX,63 EVALCCD,64 SIR-92,65 SADABS,59 ORTEP III,66 and PLATON.67 During the refinement of complex 13, one THF solvent molecule becomes apparent in the final difference Fourier maps, but due to its severe disorder, it could not be modeled properly. This problem was solved by using the PLATON calc squeeze procedure.68

Acknowledgment. We are grateful to the “Fonds der Chemischen Industrie” (FCI), the “Evonik-Stiftung“ (D.M.), and the “Konrad-Adenauer-Stiftung” (S.A.) for their support. Supporting Information Available: Crystallographic data for 9, 13, and 14, 13C spectra of 6 and 8 as well as TGA data for 8 and 13. This material is available free of charge via the Internet at http://pubs.acs.org. CCDC-783230 (9), -783232 (13), and -783231 (14) contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from the Cambridge Crystallographic Data Centre via www.ccdc. cam.ac.uk/data_request/cif. (60) Wilson, A. J. C., International Tables for Crystallography; Kluwer Academic Publisher: Dodrecht, The Netherlands, 1992. (61) Sheldrick, G. M. SHELXL-97, Program for the Refinement of Structures; University of Goettingen: Goettingen, Germany, 1997. (62) Data Collection Software for Nonius-kappa CCD devices; Nonius: Delft, The Netherlands, 1997-2000. (63) Duisenberg, A. J. M. J. Appl. Crystallogr. 1992, 25, 92. (64) Duisenberg, A. J. M.; Hooft, R. W. W.; Schreurs, A. M. M.; Kroon, J. J. Appl. Crystallogr. 2000, 33, 893. (65) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A.; Burla, M. C.; Polidori, G.; Camalli, M. J. Appl. Crystallogr. 1994, 27, 435. (66) Burnett, M. N.; Johnson, C. K. ORTEPIII; Oak Ridge National Laboratory: Oak Ridge, TN, 1996. (67) Spek, A. L. PLATON; Utrecht University: Utrecht, The Netherlands, 2001. (68) Spek, A. L. J. Appl. Crystallogr. 2003, 36, 7.