ARTICLE pubs.acs.org/Organometallics
Reactivity of [Zn2Cp*2] toward Transition-Metal Complexes: Synthesis and Characterization of [Cp*M(ZnCp*)3] (M = Ni, Pd, Pt) Timo Bollermann,† Kerstin Freitag,† Christian Gemel,† R€udiger W. Seidel,‡ and Roland A. Fischer*,† †
Anorganische Chemie II - Organometallics & Materials and ‡Lehrstuhl f€ur Analytische Chemie, Ruhr-Universit€at Bochum, 44780 Bochum, Germany
bS Supporting Information ABSTRACT: Substitution reactions of labile d10 metal starting complexes with [Zn2Cp*2] (Cp* = pentamethylcyclopentadienyl) are presented. The treatment of [M(cod)2] (M = Ni, Pt; cod =1,5-cyclooctadiene) with stoichiometric amounts of [Zn2Cp*2] results in the formation of [Cp*M(ZnCp*)3] (M = Ni (1), Pt (2)) with the release of 1,3-cyclooctadiene. In addition to Cp* transfer reactions from zinc(I) to the transition-metal centers, the formation of compounds 1 and 2 results via redox chemical pathways: namely, the oxidation of M(0) to M(I) and the reduction of 1 equiv of Zn(I) to Zn(0). The Pd homologue [Cp*Pd(ZnCp*)3] (3) is obtained as a byproduct in the reaction of [Pd(CH3)2(tmeda)] (tmeda = N,N,N0 ,N0 tetramethylethane-1,2-diamine) with [Zn2Cp*2]. Herein, various side reactions and competing redox chemical processes are involved, including the formation of [Pd(ZnCp*)4(ZnMe)4] as well as [Pd(ZnCp*)4(ZnMe)2(Zn{tmeda})]. Compounds 13 have been fully characterized by single-crystal X-ray diffraction, 1H and 13C NMR spectroscopy, IR spectroscopy, and liquid injection field desorption ionization mass spectrometry (LIFDI-MS).
T
he stabilization of elements in unusually low oxidation states presents an interesting and challenging area of research. Generally, the concepts used for this purpose focus on the right choice of ligand environments in terms of electronic and steric properties. Robinson's group, for example, uses N-heterocyclic carbenes in the synthesis of compounds with the general formula [LEEL] (E = B(H), Si, As; L = C{N(2,6-iPr2-C6H3)CH}2, C{N(2,4,6-Me3C6H2)CH}2), which are readily accessible by the reduction of the acidbase adducts (NHC)ECln with KC8.14 Following Robinson's synthetic pathway, the Jones group prepared the analogous NHCstabilized digermene by reduction with a Mg(I) dimer.5 Another stabilizing class of ligands consists of β-diketiminates, which have been used, for example, in the synthesis of [Mg2(DippNacnac)2] (DippNacnac = CH{(CMe)(2,6-iPr2C6H3N)}2) with a MgIMgI core.6,7 In 2004 Carmona's group reported [Zn2Cp*2], the first molecular compound with an unsupported Zn(I)Zn(I) covalent bond.810 The isolation of this compound initiated considerable interest, and a first series of results on the chemistry of [Zn2Cp*2] was consequently reported. Most of the publications focus on theoretical and structural investigations as well as the formation of adducts or derivative structures: e.g., preparation of [Zn2(Mesnacnac)2] and [Zn2TpMe2] (Mesnacnac = HC{C(Me)N(2,4,6-Me3C6H2)}2, TpMe2 = tris(3,5-dimethylpyrazolyl)hydridoborate).8,1115 Recently we reported on the first reactions of [Zn2Cp*2] with transition-metal complexes: namely, the reactions of [M(GaCp*)4] (M = Pd, Pt) with [Zn2Cp*2]. The products of these reactions are the compounds [(Pd,Pt)(GaCp*)a(ZnCp*)4a(ZnZnCp*)4a] (a = 0, 2), containing the unusual r 2011 American Chemical Society
one-electron ligand {ZnZnCp*} with a fully intact, trapped ZnZn bond (formally assigned as a mixed-valence moiety).16 Interestingly, a similar reaction of non-GaCp*-containing precursors, [M(cod)2] (M = Ni, Pt), with stoichiometric amounts of [Zn2Cp*2] under suitable conditions yields the analogous M(0) compounds [M(ZnCp*)2(ZnZnCp*)2] (M = Ni, Pt).17 In this paper, we report on our ongoing efforts to elucidate the reactivity patterns of [Zn2Cp*2] with reactive transition-metal precursors. The focus of this work lies on the conditions required to achieve selective Cp* transfer reactions between [Zn2Cp*2] and d10 transition-metal precursors combined with trapping the Cp*M species by ZnCp*, leading to piano-stool type complexes of the general formula [Cp*M(ZnCp*)3] (M = Ni (1), Pt (2), Pd (3)).
’ RESULTS AND DISCUSSION The treatment of [M(cod)2] (M = Ni, Pt; cod =1,5cyclooctadiene) with 2 equiv of [Zn2Cp*2] (Cp* = pentamethylcyclopentadienyl) in toluene at 80 °C over a period of 3 h leads to the formation of the stable 18-valence-electron complex [Cp*M(ZnCp*)3] (ZnCp* is counted as a 1-electron ligand), as an orange (1) or yellow (2) powder, in reproducible isolated yields of around 50% (Scheme 1). Both reactions follow the same scheme: release of 1,3-cyclooctadiene from [M(cod)2] (as determined by 1H NMR spectroscopy in C6D6) Received: May 23, 2011 Published: July 08, 2011 4123
dx.doi.org/10.1021/om200430t | Organometallics 2011, 30, 4123–4127
Organometallics
ARTICLE
Scheme 1. Synthesis of Compounds 13
Table 1. NMR Spectroscopic Data of 13 Measured in C6D6 (1 and 2) and CD2Cl2 (3) 1
13
H NMR (room temp)
C NMR
ZnCp* (s, 45H) MCp* (s, 15H) ZnC5Me5, ZnC5Me5 MC5Me5, MC5Me5 Compound 1 2.17
1.90
2.18
2.14
2.08
2.17
11.98, 111.68
13.29, 97.98
Compound 2 11.69, 110.46
13.08, 102.04
Compound 3 11.51, 110.86
13.37, 106.21
and Zn(I)Zn(I) bond cleavage as well as a Cp* transfer from the {ZnCp*} fragments to the transition metals. This reaction sequence apparently involves a (formal) redox reaction, in which 1 equiv of [Zn2Cp*2] oxidizes the transition metals M(0) to M(I), while Zn(I) itself is reduced. Indeed, the formation of an insoluble gray solid, presumably metallic zinc, is observed in the course of the reaction. Interestingly, this course of the reaction depends on the applied molar ratios of the reactants. In the presence of an excess of [Zn2Cp*2] (8 equiv), the formation of metal-rich molecules [M(ZnCp*)4(ZnZnCp*)4] (M = Ni, Pt) is observed, which will be discussed elsewhere.17 The treatment of [PdMe2(tmeda)] (tmeda = N,N,N0 ,N0 tetramethylethane-1,2-diamine) with 4 equiv of [Zn2Cp*2] in toluene at 55 °C yields a product mixture of [Cp*Pd(ZnCp*)3] (3), [Pd(ZnCp*)4(ZnMe)2(Zn{tmeda})],18 and [Pd(ZnCp*)4(ZnMe)4]19 (Scheme 1). Obviously, a variety of competing reaction pathways have to be taken into account when [Zn2Cp*2] is combined with substitution-labile M(II) complexes such as [PdMe2(tmeda)]. However, the isolation of 3 is made possible by extraction of the crude product with n-hexane, recrystallization, and manual separation of the crystals with the aid of an optical microscope. Subsequent recrystallization of this crystal collection from a toluene/n-hexane mixture at 30 °C yields pure 3. A detailed description of the selective synthesis and characterization of [Pd(ZnCp*)4(ZnMe)2(Zn{tmeda})] will be reported elsewhere. Note, however, that this latter compound contains the quite unusual species {Zn(tmeda)}, which is trapped at the Pd(0) center as a two -electron Zn(0) ligand.18 Compounds 13 are readily soluble in common organic solvents such as toluene, benzene, and n-hexane. They can be stored for several weeks under an inert-gas atmosphere at 30 °C without showing signs of decomposition. The 1H and 13 C NMR measurements show the expected pattern of signals for
Figure 1. Molecular structure of 1 in the crystal. Displacement ellipsoids are drawn at the 50% probability level. The disorder of a Cp* ligand and hydrogen atoms are omitted for clarity. Selected interatomic distances (Å) and angles (deg) for 1: Ni1Zn1 = 2.289(1), Ni1Zn2 = 2.300(1), Ni1Zn3 = 2.295(1), Zn1Cp*centroid = 1.99, Zn2Cp*centroid = 2.04, Zn3Cp*centroid = 2.07, Ni1Cp*centroid = 1.73; Zn1Ni1Zn2 = 80.95(3), Zn1Ni1Zn3 = 82.26(4), Zn2Ni1Zn3 = 80.36(4), Zn1Ni1Cp*centroid = 128.6, Zn2Ni1Cp*centroid = 133.5, Zn3 NiCp*centroid = 131.8, Cp*centroidZn1Ni1 = 165.2, Cp*centroid Zn2Ni1 = 159.5, Cp*centroidZn3Ni1 = 158.9. Selected interatomic distances (Å) and angles (deg) for 2: Pt1Zn1 = 2.40, Pt1Zn2 = 2.380(2), Pt1Zn3 = 2.377(2), Pt1Cp*centroid = 1.96, Zn1Cp*centr = 2.00, Zn2Cp*centroid = 1.98, Zn3Cp*centroid = 2.03; Zn1Pt1Zn2 = 82.61(8), Zn1Pt1Zn3 = 82.3, Zn2Pt1Zn3 = 81.13(8), Pt1 Zn1Cp*centroid = 158.7, Pt1Zn2Cp*centroid = 163.9, Pt1Zn3 Cp*centroid = 150.0, Zn1Pt1Cp*centroid = 130.2, Zn2Pt1Cp*centroid = 133.1, Zn3Pt1Cp*centroid = 128.8. Selected interatomic distances (Å) and angles (deg) for 3: Pd1Zn1 = 2.379(1), Pd1Zn2 = 2.384(1), Pd1Zn3 = 2.368(1), Pd1Cp*centroid = 1.98, Zn1Cp*centroid = 1.99, Zn2--Cp*centroid = 1.99, Zn3Cp*centroid = 1.97; Zn1Pd1Zn2 = 77.01(4), Zn1Pd1Zn3 = 80.68(4), Zn2Pd1Zn3 = 78.10(4), Cp*centroidPd1Zn1 = 135.1, Cp*centroidPd1Zn2 = 135.2, Cp*centroid Pd1Zn3 = 128.6, Cp*centroidZn1Pd1 = 156.7, Cp*centroid Zn2Pd1 = 156.1, Cp*centroidZn3Pd1 = 163.4. The corresponding structural data of 2 and 3 are provided in the Supporting Information.
equivalent ZnCp* ligands and the MCp* group (M = Ni, Pd, Pt) in a ratio of 3:1 (see Table 1 for detailed NMR spectroscopic data). Liquid injection field desorption ionization mass spectrometry (LIFDI-MS) shows molecular ion peaks for 13 [M].+ at m/z 794 (1), 932 (2), and 842 (3), respectively. An additional signal for [M Cp*]+ is observed for 2 (m/z 797) and 3 (m/z 709). The FTIR spectra of compounds 13 show typical absorptions 4124
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Organometallics of the Cp* units in the range of 28003000 cm1 (2944, 2876, 2832 cm1 (1); 2941, 2879, 2833 cm1 (2); 2973, 2868, 2831 cm1 (3)) and are quite comparable to those of other Cp*-containing compounds.20,21 It should be noted that, due to the high sensitivity of compounds 13, no satisfactory elemental analyses could be obtained. However, the purity of all compounds has been checked by NMR spectroscopy. 1H NMR spectra are given in the Supporting Information of this article (Figures S10S12). Single-crystals of 13 suitable for X-ray diffraction studies were obtained by slow cooling of saturated toluene solutions (1, 2) or a toluene/n-hexane mixture (3) down to 30 °C. Unfortunately only low-quality crystals of compound 2 could be obtained. However, the single-crystal X-ray analysis unambiguously confirmed the proposed connectivity of the atoms in 2. Compounds 13 crystallize in the triclinic space group P1 with Z = 2 for 1 and 3. The crystal structure of 2 contains six formula units per unit cell; the asymmetric unit comprises three independent molecules. Figure 1 shows the molecular structure of 1, which is discussed as the representative example for all compounds (see the Supporting Information, Figures S1 and S2 (2) and Figure S3 (3)). The structure is best described as a pseudo-tetrahedral piano-stool structure. A similar structure has also been observed in the cationic parts of isoelectronic, 18-valence-electron complexes [Cp*M(GaCp*)3]m+ (M = Fe, m = 1; M = Co, m = 2) which highlights the analogy of the 1-electron ZnCp* with the 2-electron GaCp* ligands.22 Zinc and gallium are neighbors in the periodic table and feature very similar bonding properties in terms of electronegativity and metallic and covalent radii.22 The Pt complex 2 may be viewed as analogous to the well-known textbook complexes [CpPt(CH3)3] and [Cp*Pt(CH3)3].23,24 The two 1-electron ligands CH3 and ZnCp* are formally isolobal. Interestingly, however, the respective methyl complexes of Ni and Pd are not stable and are unknown so far. The ZnMZn bond angles in 13 are nearly equal, ranging from 80.36(4)° (Zn2Ni1Zn3) to 82.26(4)° (Zn1Ni1Zn3) in 1, 81.13(8)° (Zn2Pt1Zn3) to 82.61(8)° (Zn1Pt1Zn2) in 2, and 77.01(4)° (Zn1 Pd1Zn2) to 80.68(4)° (Zn1Pd1Zn3) in 3. In addition, the Cp*centroidMZn angles show average values of 131.3° (1), 130.7° (2), and 133.0° (3). As frequently observed in ECp* (E = Ga, Zn)-containing compounds, the Cp*centroidZnM angles display strong deviations from linearity (average values: 161.2° (1), 157.6° (2), and 158.7° (3)), which indicates the steric crowding and the soft and flexible binding properties of Cp* in order to adjust to the situation.20,22,25 The MCp*centroid bond distances are well within the range of other MCp* complexes.2630 Compounds containing MZnR moieties are rather rare (R = organic group), and the comparison of MZn bond lengths is difficult and may be not particularly meaningful without detailed support from theoretical calculations. Nevertheless, we want to point out that the average value of 2.30 Å for the NiZnCp* bond lengths in 1 is significantly shorter than the NiZn bonds in other more or less related Ni/Zn complexes: e.g., [Ni(ZnCp*)4(ZnZnCp*)4]17 (ϕ = 2.35 Å for NiZnCp* and ϕ = 2.35 Å for NiZnZnCp*), [Ni(ZnCp*)4(ZnMe)4]19 (2.351(1)2.371(1) Å for NiZnCp* and 2.313(1)2.330(1) Å for NiZnMe), and [Cp6Ni2Zn4]31,32 (2.398(2) Å) as well as [Zn4Ni2(C5H5)4(C5Me5)2] (2.370(3)2.450(3) Å). To the best of our knowledge, the NiZnCp* bond lengths of 1 are the shortest NiZn interatomic distances reported so far. Also, the average PtZn distance (ϕ = 2.38 Å) in 2 is again shorter than the PtZnR (R = Cp*, Me) bonds in [Pt(ZnCp*)4(ZnMe)4]19
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(2.441(1)2.459(1) Å for PtZnCp* and 2.402(1)2.467(1) Å for PtZnMe) or [Pt(GaCp*)2(ZnCp*)2(ZnZnCp*)2]16 (2.4152(16) Å for PtZnCp* and ϕ = 2.39 Å for PtZnZnCp*). Finally, the PdZn bond lengths (ϕ = 2.38 Å) in 3 are also shorter than those in other PdZn complexes such as [Pd(GaCp*)2(ZnCp*)2(ZnZnCp*)2]16 (2.448(1) Å for PdZnCp* and 2.375(1)2.379(1) Å for PdZnZnCp*), [Pd(ZnCp*)4(ZnMe)2(Zn{tmeda})]18 (ϕ = 2.47 Å for PdZnCp*, ϕ = 2.39 Å for PdZnMe, 2.389(1) Å for PdZn(tmeda)), and [Pd(ZnCp*)4(ZnMe)4]19 (2.447(1)2.459(1) Å); however, they are rather similar to the PdZn distance found in [(FPNP)PdZn Pd(FPNP)]33 (2.372(1)2.379(1) Å; FPNP = bis(4-fluoro2-(diisopropylphosphino)phenyl)amine. The ZnCp*centroid distances of 13 (average values: 2.03 Å (1), 2.00 Å (2), and 1.98 Å (3)) are distinctly longer than in other ZnCp*-containing compounds such as [Zn2Cp*2] (1.94 Å), [Ni(ZnCp*)4(ZnZnCp*)4]17 (1.95 Å for {ZnZnCp*} and 1.95 Å for {ZnCp*}), [Ni(ZnCp*)4(ZnMe)4]19 (1.96 Å), [Pt(ZnCp*)4(ZnMe)4]19 (1.94 Å), [Pt(ZnCp*)4(ZnEt)4]19 (1.93 Å), and [Pd(GaCp*)2(ZnCp*)2(ZnZnCp*)2] (1.95 Å).16 The ZnCp* contact may be taken as an indication of small variations of partial charge at the Zn center, as has been well established for the related GaCp* contacts in complexes [LnM(GaCp*)] of various kinds. However, as mentioned above, the steric crowding of three facial ZnCp* ligands may also affect the average ZnCp* distances.
’ CONCLUSIONS Reactions of the substitution-labile group 10 metal starting complexes [M(cod)2] (M = Ni, Pt) with stoichiometric amounts [Zn2Cp*2] under moderate conditions lead to the formation of stable 18-valence-electron complexes [Cp*M(ZnCp*)3] (M = Ni (1), Pt (2)). These complexes adopt a pseudo-tetrahedral piano-stool structure. The overall reaction sequence includes several reaction steps: (a) complete substitution of the olefin ligands (loss of 1,3-cyclooctadiene), (b) homolytic splitting of the ZnZn bond, (c) Cp* transfer from a {ZnCp*} fragment to the d10 metal combined with deposition of Zn(0), and (d) trapping of {ZnCp*} ligands at the metal center. Furthermore, [Cp*Pd(ZnCp*)3] (3) can be obtained as a product when [PdMe2(tmeda)] is treated with [Zn2Cp*2]. The preparation of compounds 13 demonstrates the possibility of using [Zn2Cp*2] as a selective reagent for combined Cp* and ZnCp* transfer in the organometallic chemistry of transition metals in low oxidation states. The new compounds [Cp*M(ZnCp*)3] (M = Ni (1), Pt (2), Pd (3)) may be interesting as novel Cp*M transfer reagents in metathesis reactions by using ZnCp* as the leaving group (Cp*M is suggested to be the nucleophile and ZnCp* is likely to behave as the electrophilic part). ’ EXPERIMENTAL SECTION General Remarks. All manipulations were carried out under an atmosphere of purified argon using standard Schlenk and glovebox techniques. n-Hexane and toluene were dried using an mBraun Solvent Purification System. The final H2O content of all solvents used was checked by Karl Fischer titrations and did not exceed 5 ppm. [Ni(cod)2],34 [Pt(cod)2],35 [PdMe2(tmeda)],36 and [Zn2Cp*2]8 were prepared according to literature methods. NMR spectra were recorded on a Bruker Avance DPX-250 spectrometer (1H, 250.1 MHz; 13C, 62.9 MHz) in C6D6 and CD2Cl2 at 298 K unless stated otherwise. Chemical shifts are given relative to TMS and were referenced to the residual 4125
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Organometallics solvent peaks as internal standards. The X-ray diffraction intensities were collected on an Oxford Xcalibur 2 diffractometer with a Sapphire2 CCD. The crystals were coated with a perfluoropolyether, picked up with a glass fiber, and immediately mounted in the nitrogen cold gas stream of the diffractometer. The crystal structures were solved by direct methods using SHELXS-97 and refined with SHELXL-97.37 CCDC 826615 (1), 826616 (2), and 826617 (3) 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. FT-IR spectra were measured in an ATR setup with a Bruker Alpha FTIR spectrometer under an inert-gas atmosphere in a glovebox. Mass spectrometry was measured with a JEOL AccuTOF GCv instrument: ionization method, liquid injection field desorption ionization (LIFDI; special ionization cell obtained from Linden CMS GmbH, Leeste, Germany; http://www.linden-cms.de); solvent, toluene. Syntheses. [Cp*Ni(ZnCp*)3] (1). [Ni(cod)2]2 (0.150 g, 0.607 mmol) and [Zn2Cp*2] (0.460 g, 1.275 mmol) in toluene (5 mL) were stirred at 80 °C for 3 h. The solvent was removed in vacuo, and the residue was washed four times with 3 mL of n-hexane and dried in vacuo to give an orange solid. Recrystallization of the crude product by cooling a saturated solution in toluene (3 mL) of 1 to 30 °C gave orange single crystals. Yield: 0.304 g (63%). 1H NMR (δ1H, C6D6): 1.90 (s, 15H, NiC5Me5), 2.17 (s, 45H, ZnC5Me5). 13C{1H} NMR (δ13C{1H}, C6D6): 11.98 (ZnC5Me5), 13.29 (NiC5Me5), 97.98 (NiC5Me5), 111.68 (ZnC5Me5). IR (ATR, cm1): 2944 (w), 2876 (s), 2832 (s), 2700 (w), 1421 (s), 1364 (s), 1233 (w), 1014 (s), 789 (w), 722 (w), 585 (s). MS (LIFDI, toluene): m/z 794 [M].+. [Cp*Pt(ZnCp*)3] (2). [Pt(cod)2]2 (0.106 g, 0.258 mmol) and [Zn2Cp*2] (0.233 g, 0.541 mmol) in toluene (5 mL) were stirred at 100 °C for 1.5 h. The solvent was removed in vacuo, and the residue was washed with n-hexane (5 mL) and dried in vacuo to give a yellow solid. Recrystallization of the crude product by cooling a saturated toluene solution (3 mL) of 2 to 30 °C gave yellow single crystals. Yield: 0.115 g (48%). 1H NMR (δ1H, C6D6): 2.14 (s, 15H, PtC5Me5), 2.18 (s, 45H, ZnC5Me5). 13C{1H} NMR (δ13C{1H}, C6D6): 11.69 (ZnC5Me5), 13.08 (PtC5Me5), 102.04 (PtC5Me5), 110.46 (ZnC5Me5). IR (ATR, cm1): 2941 (w), 2879 (m), 2833 (m), 1425 (w), 1364 (m), 1223 (s), 1115 (m), 975 (s), 788 (w), 738 (w), 721 (w), 688 (w), 643 (w), 583 (w), 523 (w), 409 (w). MS (LIFDI, toluene): m/z 932 [M].+, 797 [M Cp*]+. [Cp*Pd(ZnCp*)3] (3). [PdMe2(tmeda)] (0.060 g, 0.237 mmol) and [Zn2Cp*2] (0.390 mg, 0.974 mmol) were dissolved in toluene (6 mL), resulting in a deep red solution. The mixture was stirred for 1 h at 55 °C. The solvent was reduced in vacuo, and the yellow-orange residue was extracted three times with 3 mL of n-hexane. The first 3 mL of the filtrate was discarded to remove [Pd(ZnCp*)4(ZnMe)4]. The following 6 mL of the filtrate was collected, and the solvent was removed in vacuo. The orange powder was dried in vacuo to yield nearly pure 3. Recrystallization of the crude product in a mixture of toluene and n-hexane (3 mL/2 mL) at 30 °C overnight gave orange single crystals. Small impurities of [Pd(ZnCp*)4(ZnMe)2(Zn{tmeda})] can be easily removed by manual separation of the crystals in the glovebox under an inert-gas atmosphere. Yield: 0.065 g (33%). 1H NMR (δ1H, CD2Cl2): 2.08 (s, 45H, ZnC5Me5), 2.17 (s, 15H, PdC5Me5). 13C{1H} NMR (δ13C{1H}, CD2Cl2): 11.51 (ZnC5Me5), 13.37 (PdC5Me5), 106.21 (PdC5Me5), 110.86 (ZnC5Me5). IR (ATR, cm1): 2973 (w), 2868 (m), 2831 (m), 1447 (m), 1425 (m), 1406 (m), 1363 (m), 1277 (w), 1250 (w), 1152 (w), 1088 (w), 1037 (m), 1019 (w), 940 (w), 886 (w), 861 (w), 850 (w), 786 (s), 756 (w), 722 (w), 689 (w), 629 (m), 583 (w), 523 (w), 469 (w), 459 (w), 444 (w), 425 (w), 412 (w). MS (LIFDI, toluene): m/z 842 [M].+, 709 [M Cp*]+.
’ ASSOCIATED CONTENT
bS
Supporting Information. Text, figures, tables, and CIF files giving crystallographic data and details of the refinement and
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IR and NMR spectra for 13. This material is available free of charge via the Internet at http://pubs.acs.org.
’ AUTHOR INFORMATION Corresponding Author
*E-mail: roland.fi
[email protected]. Fax (+49)234 321 4174.
’ ACKNOWLEDGMENT This work was funded by the German Research Foundation (Fi-502/23-1). T.B. is grateful for a Ph.D. scholarship provided by the Fonds der Chemischen Industrie and for the support of the Ruhr University Research School (http://www.research-school. rub.de/). We thank the Linden CMS GmbH and S. Bendix (Ruhr University Bochum) for support in mass spectrometry. ’ REFERENCES (1) Wang, Y.; Xie, Y.; Wei, P.; King, R. B.; Schaefer, H. F., III; Schleyer, P. v. R.; Robinson, G. H. Science 2008, 321, 1069–1071. (2) Wang, Y.; Quillian, B.; Wei, P.; Wannere, C. S.; Xie, Y.; King, R. B.; Schaefer, H. F., III; Schleyer, P. v. R.; Robinson, G. H. J. Am. Chem. Soc. 2007, 129, 12412–12413. (3) Abraham, M. Y.; Wang, Y.; Xie, Y.; Wei, P.; Schaefer, H. F., III; Schleyer, P. v. R.; Robinson, G. H. Chem. Eur. J. 2010, 16, 432–435. (4) Wang, Y.; Quillian, B.; Wei, P.; Xie, Y.; Wannere, C. S.; King, R. B.; Schaefer, H. F., III; Schleyer, P. v. R.; Robinson, G. H. J. Am. Chem. Soc. 2008, 130, 3298–3299. (5) Sidiropoulos, A.; Jones, C.; Stasch, A.; Klein, S.; Frenking, G. Angew. Chem., Int. Ed. 2009, 48, 9701–9704. (6) Green, S. P.; Jones, C.; Stasch, A. Angew. Chem., Int. Ed. 2008, 47, 9079–9083. (7) Green, S. P.; Jones, C.; Stasch, A. Science 2007, 318, 1754–1757. (8) del Rio, D.; Galindo, A.; Resa, I.; Carmona, E. Angew. Chem., Int. Ed. 2005, 44, 1244–1247. (9) Grirrane, A.; Resa, I.; Rodriguez, A.; Carmona, E.; Alvarez, E.; Gutierrez-Puebla, E.; Monge, A.; Galindo, A.; Del Rio, D.; Andersen, R. A. J. Am. Chem. Soc. 2007, 129, 693–703. (10) Resa, I.; Carmona, E.; Gutierrez-Puebla, E.; Monge, A. Science 2004, 306, 411. (11) Schulz, S.; Schuchmann, D.; Westphal, U.; Bolte, M. Organometallics 2009, 28, 1590–1592. (12) Schulz, S.; Schuchmann, D.; Krossing, I.; Himmel, D.; Blaeser, D.; Boese, R. Angew. Chem., Int. Ed. 2009, 48, 5748–5751. (13) Schuchmann, D.; Westphal, U.; Schulz, S.; Florke, U.; Blaser, D.; Boese, R. Angew. Chem., Int. Ed. 2009, 48, 807–810. (14) Gondzik, S.; Blaeser, D.; Woelper, C.; Schulz, S. Chem. Eur. J. 2010, 16, 13599–13602. (15) Carrasco, M.; Peloso, R.; Rodriguez, A.; Alvarez, E.; Maya, C.; Carmona, E. Chem. Eur. J. 2010, 16, 9754–9757. (16) Bollermann, T.; Freitag, K.; Gemel, C.; Seidel, R. W.; von Hopffgarten, M.; Frenking, G.; Fischer, R. A. Angew. Chem., Int. Ed. 2011, 50, 772–776. (17) Bollermann, T.; Freitag, K.; Gemel, C.; Seidel, R. W.; von Hopffgarten, M.; Frenking, G.; Fischer, R. A. Manuscript in preparation. (18) Bollermann, T.; Freitag, K.; Gemel, C.; Seidel, R. W.; von Hopffgarten, M.; Frenking, G.; Fischer, R. A. Manuscript in preparation. (19) Cadenbach, T.; Bollermann, T.; Gemel, C.; Tombul, M.; Fernandez, I.; van Hopffgarten, M.; Frenking, G.; Fischer, R. A. J. Am. Chem. Soc. 2009, 131, 16063–16077. (20) Jutzi, P.; Neumann, B.; Schebaum, L. O.; Stammler, A.; Stammler, H.-G. Organometallics 1999, 18, 4462–4464. (21) Bollermann, T.; Cadenbach, T.; Gemel, C.; Freitag, K.; Molon, M.; Gwildies, V.; Fischer, R. A. Inorg. Chem. 2011, 50, 5808–5814. 4126
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