- Email: [email protected]
Photochemical reactions of cyclic cyclopentadienyldicarbonyliron silyl complexes
Journal of Organometallic Chemistry 813 (2016) 61e70
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry journal homepage: www.elsevier.com/locate/jorganchem
Photochemical reactions of cyclic cyclopentadienyldicarbonyliron silyl complexes Bolin Zhu*, Tian Wang, Yuan Li, Ruichen Sun, Shaonan Wu, Bin Wang Tianjin Key Laboratory of Structure and Performance for Functional Molecules, Key Laboratory of Inorganic-Organic Hybrid Functional Materials Chemistry, Ministry of Education, College of Chemistry, Tianjin Normal University, Tianjin 300387, People's Republic of China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 29 November 2015 Received in revised form 24 February 2016 Accepted 10 April 2016 Available online 12 April 2016
Photolysis of the cyclic cyclopentadienyldicarbonyliron silyl (CpFeeSi) complex [(SiMe2)(h5-C5H4) Fe(CO)2]2 (1) in toluene under N2 results in the SiMe2-bridged complex [(h5-C5H4)2(SiMe2)]Fe2(CO)2(mCO)2 (4), the same reaction in the presence of trace amounts of air affords the SiMe2OSiMe2-bridged complex [(h5-C5H4)2(SiMe2OSiMe2)]Fe2(CO)2(m-CO)2 (5). Photolysis of 1 in the presence of HER3 (E ¼ Si, Ge, Sn) or H2SiPh2 results in the loss of CO and the oxidative addition of the HeE bond to form the corresponding products [(SiMe2)(h5-C5H4)Fe(CO)(ER3)H]2 (7a-e) and [SiMe2(h5-C5H4)Fe(CO)2][SiMe2(h5C5H4)Fe(CO)(SnPh3)H] (8d). Photolysis of the other cyclic CpFeeSi complex (CMe2)(h5-C5H3)(h5,h1-C5H3) [(SiMe2)Fe(CO)2][Fe(CO)2] (2) in the presence of HER3 (ER3 ¼ SiMePh2, GeEt3) forms the corresponding products (h5,h5:h1-C5H4CMe2C5H3SiMe2)[Fe(CO)2(ER3)][Fe(CO)2] (9a-b), which involves cleavage of a FeeC bond. However, Photolysis of 2 with H2SiPh2 affords not only the product 10, the analogue of 9, but also the singly-bridged dicyclopentadienyl diiron complex [(h5-C5H4)(h5-C5H3(SiHMe2))(CMe2)] Fe2(CO)2(m-CO)2 (11), which contains a FeeFe bond. Plausible mechanisms for the formation of the different types of products are proposed. Molecular structures of 7a, 7c, 7d, 8d, 9a, and 11 were determined by X-ray diffraction. © 2016 Elsevier B.V. All rights reserved.
Keywords: Photoreaction FeeSi Oxidative addition of EeH bond (E ¼ Si, Ge, Sn) X-ray diffraction
1. Introduction The cyclopentadienyldicarbonyliron silyl complex (h5-C5R5) Fe(CO)2SiMe3 (R ¼ H or Me) (Chart 1) has attracted considerable interest. Related research is mainly concentrated on the following five aspects: (i) photo-induced oxidative addition of HSiR3 (E ¼ Me, or Et) [1], (ii) photoreaction with H2ER2 or H3ER (E ¼ Si, or Ge) to give m-ER2 or EHR bridged diiron complexes [2e9], (iii) baseinduced metal-to-ring migration of the silyl group [10e14], (iv) ligand exchange reaction [15], (v) and as a catalyst to activate the CeCN bond in acetonitrile [16,17]. In this paper, we focused on two cyclic cyclopentadienyldicarbonyliron silyl (CpFeeSi) complexes, the analogues of (h5-C5R5)Fe(CO)2SiMe3. One is the complex [(SiMe2)(h5-C5H4)Fe(CO)2]2 (1) (Chart 1), which contains two FeeSi units in its cyclic structure. It was first reported by Zhou's group in 1993 and was generated from the thermal rearrangement of the disilane-bridged bis(cyclopentadienyl)tetracarbonyldiiron complex [(h5-C5H4)2(SiMe2SiMe2)]Fe2(CO)2(m-CO)2 (3) (Scheme 1) [18]. The
* Corresponding author. E-mail address: [email protected] (B. Zhu). http://dx.doi.org/10.1016/j.jorganchem.2016.04.006 0022-328X/© 2016 Elsevier B.V. All rights reserved.
other is the complex (CMe2)(h5-C5H3)(h5,h1-C5H3)[(SiMe2)Fe(CO)2] [Fe(CO)2] (2), which contains one FeeSi unit. It was produced by the thermal reaction of the doubly-bridged dicyclopentadienes (C5H4(CMe2))(C5H4(SiMe2)) with Fe(CO)5 [19]. With respect to the “classic” complex (h5-C5R5)Fe(CO)2SiMe3, these two cyclic complexes are air-stable yellow crystalline solids, which are easy to synthesize, handle and store in the long term. These advantages could make them reactivity analogues for the parent complex (h5C5R5)Fe(CO)2SiMe3. In order to compare the reactivity of 1, 2 and (h5-C5R5)Fe(CO)2SiMe3 and to help understand the mechanisms of similar reactions, herein, we report herein our findings on the photochemical reaction of 1, and the photolysis of 1 and 2 in the presence of HER3 (E ¼ Si, Ge, or Sn) and H2SiPh2.
2. Results and discussion 2.1. Photochemistry of 1 Vollhardt et al. have reported an intriguing photo-thermal reversible system which has a potential application as an efficient solar-thermal energy storage device: the diruthenium complex
62
B. Zhu et al. / Journal of Organometallic Chemistry 813 (2016) 61e70
Chart 1. Several types of cyclopentadienyldicarbonyliron silyl complexes.
Scheme 1. Photolysis of 1 under N2 or trace amounts of air.
FvRu2(CO)4 (Fv ¼ h5:h5-bicyclopentadienyl) undergoes rapid isomerization under irradiation to the high-energy complex (m2h1:h5-cyclopentadienyl)2Ru2(CO)4, and the latter reverts to the original one upon heating with an energy release (Scheme 2) [20e23]. Here, the CpFeeSi complex 1 was generated from the thermal rearrangement of complex 3, and we were therefore curious about the photo reversibility of 1. UV irradiation (l ¼ 365 nm) of a solution of 1 in toluene under N2 at 0 C for 10 h produced one identifiable product [(h5-C5H4)2(SiMe2)]Fe2(CO)2(mCO)2 (4) in low yield (17%), a SiMe2-bridged bis(cyclopentadienyl) diiron complex (Scheme 1). Much longer irradiation time did not increase the yield of the product, instead, it led to the serious decomposition of the starting material 1. Unfortunately, complex 1 did not convert to the expected diiron complex 3 to form a photothermal reversible cycle under our current conditions. The formation of 4 indicates that a SiMe2 moiety is cleaved from 1, and then a structural transformation occurs. In hope of trapping this SiMe2 moiety, a toluene solution of 1 and ten-fold excess of hydrosilane (HER3), the silylene-trapping agent, was irradiated under the similar conditions, unfortunately, no the silylene-trapped product
Scheme 2. Photoisomerization of fulvalene(tetracarbonyl)diruthenium.
was detected [24,25]. Instead, the oxidative addition of HeE bond on Fe atoms occurred, and formed the product [(SiMe2)(h5-C5H4) Fe(CO)(ER3)H]2 (see below). A similar expulsion of SiR2 species was reported by Pannell in the photolysis of disilyl iron complex (h5C5H5)Fe(CO)2(SiMe2SiR3) (R ¼ Ph, Me) [26]. When the same reaction was run in the presence of trace amounts of air, surprisingly, complex 1 captured an oxygen during the photo transformation to give SiMe2OSiMe2-bridged bis(cyclopentadienyl) diiron complex 5 in high yield (91%). The mechanism for the conversion of 1 to 5 is unclear. Presumably, trace amounts of air serve as the source of the oxygen atom for the construction of the SiMe2OSiMe2 bridge [27]. In order to determine if complex 5 undergoes a thermal rearrangement reaction, a xylene solution of 5 was refluxed for 30 h. This afforded an unexpected disiloxane-bridged ferrocene Fe[(h5C5H4)SiMe2]2O (6) product in moderate yield (56%) (Scheme 1). Previously, complex 6 was prepared via reaction of 1,10 -dilithioferrocene with dichlorodisiloxane, or via hydrolysis of 1,10 -bis(chlorodimethylsilyl)ferrocene [28,29]. 2.2. Photochemistry of 1 in the presence of HER3 (E ¼ Si, Ge, Sn) or H2SiPh2 Wrighton et al. have reported that photolysis of Cp*Fe(CO)2SiMe3 in the presence of HSiR3 results in the loss of CO and the oxidative addition of HSiR3 to form trans-Cp*Fe(CO)(SiMe3)(SiR3)H, unfortunately, the product was not isolated [1]. Later on, similar complexes CpFe(CO)(SiMe2Ph)2H and CpFe(CO)(SiEt3)(SiMe2Ph)H were synthesized by Nakazawa et al. from the corresponding silyl(pyridine)iron complexes with HSiPhMe2, and also fully characterized [30,31]. By analogy with the reactions of CpFe(CO)2SiMe3,
B. Zhu et al. / Journal of Organometallic Chemistry 813 (2016) 61e70
a series of photoreactions of 1 with HER3 (ER3 ¼ SiMePh2, SiMe2Ph, GeEt3, and SnPh3) were performed. UV photolysis of 1 and excess HER3 in toluene under N2 at 0 C for 2e4 h resulted in the corresponding products [(SiMe2)(h5-C5H4)Fe(CO)(ER3)H]2 (7a-d, 25e53% yields) (Scheme 3), in which oxidative addition of the EeH bond in HER3 occurred at both iron centers. The reaction of 1 with HSnPh3 also afforded product 8d, in which only one iron center was involved the oxidative addition of the SneH bond. In addition, irradiation of 1 with excess H2SiPh2 produced the similar compound 7e through SieH bond oxidative addition. This result is different from the photoreaction of the parent complex Cp*Fe(CO)2SiMe3 with H2SiR2, which generally gave m-SiR2 bridged diiron complexes [6]. This indicates that complex 1 tends to retain its stable six-membered ring structure during the reaction. A plausible mechanism for the formation of 7a-e involves the loss of CO from each iron center in 1 under UV irradiation to give a 16ee unsaturated species, which is followed by oxidative addition of a EeH bond to each metal center. All products were isolated by silica gel column chromatography and well characterized by 1H NMR, IR, and elemental analysis. The structures of 7a, 7c, 7d, and 8d were also confirmed by the single-crystal X-ray diffraction. In the presence of 1 atm CO, a solution of 7a in toluene reacted (45 C, 2 h) to form the original complex 1 (95% yield) and HSiMePh2 (Scheme 4). This is the reverse reaction of the photocatalyzed oxidative addition of the EeH bond described above; a plausible pathway involves reductive elimination of HSiMePh2 followed by CO uptake. 2.3. Molecular structures of 7a, 7c, 7d, and 8d X-ray structural determinations of 7a, 7c and 7d (Figs. 1e3) show their structures to be very similar to one another, all of them have a perfect Ci symmetry, and the six-membered ring FeeSieCeFeeSieC constituting the molecular framework adopts a stable chair conformation, like its parent complex 1. This may account for the robustness of the cyclic system, which remains unchanged throughout the transformation. The metal atoms exhibit a fourlegged piano-stool geometry, the carbonyl and hydrogen on silicon adopt a trans arrangement. The FeeSi bond distance (2.330(2) Å in 7a, 2.3053(7) Å in 7c, 2.339(2) Å in 7d) compares very well with the data (2.315(2) Å) for 1 [18]. The molecular structure of 8d is shown in Fig. 4. It has an asymmetric structure. The six-membered ring Fe(1)eSi(1)eC(8)e Fe(2)eSi(2)eC(1) of the molecular framework also adopts a stable chair conformation. The two cyclopentadienyl rings are almost parallel, as indicated by the small dihedral angle of 1.1. One iron atom exhibits a three-legged piano-stool geometry, with two carbonyls and one silyl group attached. The other iron atom exhibits a
63
four-legged piano-stool geometry, with one carbonyl, one silyl, one hydro and one SnPh3 group attached. The two FeeSi bond distances (2.303(3) Å and 2.325(2) Å) are close to each other, and also consistent with the data (2.315(2) Å) for 1 [18] 2.4. Photochemistry of 2 in the presence of HER3 (ER3 ¼ SiMePh2, GeEt3) or H2SiPh2 Compared to complex 1, complex 2 has an unsymmetrical structure, in which one iron atom is coordinated with a cyclopentadienyl ring in h5 fashion, and the other iron atom is coordinated with two cyclopentadienyl ligands in h5 and h1 fashion at the same time. To understand the reactivity of the two different metal centers, photolysis of 2 in the presence of HER3 (ER3 ¼ SiMePh2, GeEt3) was studied. UV irradiation of 2 and excess HER3 in toluene under N2 at 0 C for 2 h resulted in the corresponding products (h5,h5:h1-C5H4CMe2C5H3SiMe2)[Fe(CO)2(ER3)][Fe(CO)2] (9a-b, 30e42% yields) (Scheme 5). The NMR spectra of 9a-b exhibit seven resonances for the two Cp rings (they display unique ABC and ABCD splitting patterns), two signals for the C(CH3)2 methyl groups and two signals for the Si(CH3)2 methyl groups in the ranges of d 1.53e1.31 and 0.67e0.51, respectively. The IR spectra of 9a-b show the expected four strong n(CO) absorptions (2003, 1979, 1935, 1917 cm1 for 9a, 2001, 1979, 1943, 1923 cm1 for 9b), which correspond to the four terminal CO ligands. The structure of 9a (Fig. 5) was conclusively established by an X-ray crystallographic analysis. Two different iron units Fe(CO)2(SiMePh2) and Fe(CO)2(SiMe2) are both coordinated to the corresponding cyclopentadienyl ring in h5 fashion. The six-membered ring C(1)eC(2)eC(13)eC(8)e Fe(2)eSi(1) constituting the molecular framework adopts a twist boat conformation. Obviously, an FeeC bond in 2 is broken in the course of forming 9a-b, while the fragment (h5-Cp)Fe(CO)2(SiMe2) stays unchanged. The reason that the (h5-Cp)(h1-Cp)Fe(CO)2 fragment in 2 preferentially takes part in the reaction may be due to a decrease in ring strain in products 9a-b arising from the ringopening reaction. A plausible mechanism for the formation of 9a-b is tentatively proposed in Scheme 6. First, a CO is lost from 2 under UV irradiation to give a 16e unsaturated iron species (A); this is followed by oxidative addition of the EH bond in HER3 to form B. In the next step, elimination of Cp and H from B results in intermediate C. Finally, recoordination of CO in C forms the final product 9a-b. Photolysis of 2 and excess H2SiPh2 in toluene under the same conditions affords not only the product (h5,h5:h1-C5H4CMe2C5H3SiMe2)[Fe(CO)2(SiHPh2)][Fe(CO)2] (10), the analogue of 9a-b, but also the singly-bridged dicyclopentadienyl diiron complex [(h5C5H4)(h5-C5H3(SiHMe2))(CMe2)]Fe2(CO)2(m-CO)2 (11), which contains a FeeFe bond. (Scheme 7). The NMR spectrum of 11 exhibits
Scheme 3. Photoreactions of 1 in the presence of HER3 (E ¼ Si, Ge, Sn) or H2SiPh2.
64
B. Zhu et al. / Journal of Organometallic Chemistry 813 (2016) 61e70
Scheme 4. Thermal reaction of 7a under CO (1 atm).
Fig. 1. Thermal ellipsoid drawing of [SiMe2(h5-C5H4)Fe(CO)(SiMePh2)H]2 (7a) showing the labeling scheme and 30% probability ellipsoids. Hydrogens are partly omitted for clarity. Selected bond lengths (Å) and angles (deg): Fe(1)eSi(1) 2.330(2), Fe(1)eSi(2) 2.340(2), Fe(1)eC(18) 1.718(7), C(4)Si(1A) 1.894(6), Fe(1)Cp(centroid) 1.716, :Fe(1A)Si(1A)C(4) 110.44(18), :Si(1A)C(4)eFe(1) 132.5(3), :C(4)eFe(1)Si(1) 99.72(16), :Si(1)eFe(1)C(18) 82.8(2), :Si(1)eFe(1)Si(2) 114.28(7), :Fe(1)eC(18)O(1) 178.4(6), :CpCp fold angle 0.
six resonances for seven inequivalent protons on two Cp rings (two proton peaks overlap), two signals for the C(CH3)2 methyl groups and two signals for the Si(CH3)2 methyl groups at d 1.52, 1.46 and 0.64, 0.30, respectively, and one multiplet at d 4.94 corresponding to the SieH. The IR spectrum of 11 shows n(CO) absorptions at 2021, 1991, and 1773 cm1, indicating the presence of both terminal and bridging CO ligands. A single-crystal X-ray structural determination of 11 shows in Fig. 6. The FeeFe bond distance in 11 (2.465(1) Å) is slightly shorter than that (2.484(6) Å) in its parent complex [(h5C5H4)2CMe2]Fe2(CO)2(m-CO)2, which is consistent with its smaller dihedral angle (:CpCp 107.0 ) than that (109.3 or 109.6 ) in the latter [32]. There is only a small twist around the FeeFe axis; this is reflected by the torsion angles :Cp(centroid)Fe(1)eFe(2) Cp(centroid) (1.5 ) and :C(14)eFe(1)Fe(2)eC(17) (0.7 ). Based on the proposed mechanism described above, it is easy to understand the formation of complex 10. We considered that 11 could be obtained from a further intramolecular SieH bond activation in 10. Therefore the photolysis of 10 in toluene was carried out and indeed yielded product 11 (71%). Although the formation of 11 involves the loss of the SiPh2 moiety from 10, no SiPh2-containing product was separated by column chromatography. On the
basis of our results, a plausible mechanism for the formation of 11 is tentatively proposed in Scheme 8. First, a CO is lost from 10 under UV irradiation to give a 16e unsaturated iron species (A); this is followed by oxidative addition of an adjacent SieH bond on the SiHPh2 group to form B. In the next step, elimination of SiMe2 and H from B results in intermediate C. Finally, C undergoes desilylation (SiPh2) to form the final product 11. Similar destannylation was observed in our previous report on the photolysis of EMe2[(h5C5H4)Fe(CO)2]2SnMe2 (E ¼ C or Si), an analogue of C, which gave the corresponding diiron product [(h5-C5H4)2EMe2]Fe2(CO)2(m-CO)2 [33,34]. Attempts to isolate intermediate C were unsuccessful, which might be due to the instability of the FeeSieFe unit in C. The similar dimethylgermyl compound [(h5-C5H5)Fe(CO)2]2GeMe2 was extremely instable even upon standing in the dark, decomposing to [(h5-C5H5)Fe(CO)2]2 [35]. In order to further support our proposed mechanism, a labeling experiment was carried out to track the two SieH protons in H2SiPh2. Photolysis of 2 and excess D2SiPh2 in toluene generated the corresponding FeeFe-bonded complex [(h5C5H3D)(h5-C5H3(SiDMe2))(CMe2)]Fe2(CO)2(m-CO)2 (11-d2), which is evident in the presence of the same peaks as for 11 in the 1H NMR spectrum, except for the two peaks assigned to the SieH proton and
B. Zhu et al. / Journal of Organometallic Chemistry 813 (2016) 61e70
65
Fig. 2. Thermal ellipsoid drawing of [SiMe2(h5-C5H4)Fe(CO)(GeEt3)H]2 (7c) showing the labeling scheme and 30% probability ellipsoids. Hydrogens are partly omitted for clarity. Selected bond lengths (Å) and angles (deg): Fe(1)Si(1A) 2.3053(7), Fe(1)eGe(1) 2.4207(5), Fe(1)eC(8) 1.721(2), C(1)eSi(1) 1.888(2), Fe(1)Cp(centroid) 1.708, :Fe(1A)Si(1)eC(1) 110.47(7), :Si(1)eC(1)Fe(1) 132.38(11), :C(1)eFe(1)Si(1A) 99.59(6), :Si(1A)Fe(1)eC(8) 86.06(8), :Si(1A)Fe(1)eGe(1) 114.48(2), :Fe(1)eC(8)O(1) 177.5(2), :CpCp fold angle 0.
Fig. 3. Thermal ellipsoid drawing of [SiMe2(h5-C5H4)Fe(CO)(SnPh3)H]2 (7d) showing the labeling scheme and 30% probability ellipsoids. Hydrogens are partly omitted for clarity. Selected bond lengths (Å) and angles (deg): Fe(1)eSi(1) 2.3393(15), Fe(1)eSn(1) 2.5532(9), Fe(1)eC(1) 2.104(4), Fe(1)eC(24) 1.723(6), C(1)Si(1A) 1.893(5), Fe(1)Cp(centroid) 1.720, :Fe(1A)Si(1A)C(1) 111.47(14), :Si(1A)C(1)eFe(1) 132.4(2), :C(1)eFe(1)Si(1) 99.21(13), :Si(1)eFe(1)C(24) 83.20(17), :Si(1)eFe(1)Sn(1) 112.18(4), :Fe(1) eC(24)O(1) 177.2(5), :CpCp fold angle 0.
one proton on the Cp ring (see the supporting information). 3. Conclusions Photolysis of the cyclic CpFeeSi complex [(SiMe2)(h5-C5H4) Fe(CO)2]2 (1) under N2 or trace amounts of air affords the SiMe2bridged complex [(h5-C5H4)2(SiMe2)]Fe2(CO)2(m-CO)2 (4) or the SiMe2OSiMe2-bridged complex [(h5-C5H4)2(SiMe2OSiMe2)] Fe2(CO)2(m-CO)2 (5) respectively, but not the expected complex
[(h5-C5H4)2(SiMe2SiMe2)]Fe2(CO)2(m-CO)2 (3). So the expected photo-thermal reversible cycle between 1 and 3 was not achieved under our conditions. Photolysis of 1 with HER3 (E ¼ Si, Ge, Sn) or H2SiPh2 results in the corresponding oxidative addition products [(SiMe2)(h5-C5H4)Fe(CO)(ER3)H]2 (7a-e) and [SiMe2(h5-C5H4) Fe(CO)2][SiMe2(h5-C5H4)Fe(CO)(SnPh3)H] (8d), which shows that 1 exhibits a reactivity that is similar to that of its parent complex (h5C5Me5)Fe(CO)2SiMe3. Photolysis of the other cyclic CpFeeSi complex (CMe2)(h5-C5H3)(h5,h1-C5H3)[(SiMe2)Fe(CO)2][Fe(CO)2] (2)
66
B. Zhu et al. / Journal of Organometallic Chemistry 813 (2016) 61e70
were carried out at room temperature with a water-jacketed 500 W high-pressure Hg lamp (lmax ¼ 365 nm) as the UV source. The irradiation was conducted in a quartz tube, which was placed adjacent to the lamp, or in 5 mm quartz NMR tubes. Complexes 1 and 2 were prepared by the literature methods [18,19]. 4.2. Photolysis of 1 in toluene under N2 A solution of 1 (47 mg, 0.10 mmol) in toluene (10 mL) was bubbled with N2 for 10 min and then irradiated for 10 h. During this time the solution turned from yellow to red. After removal of the solvent, the residue was chromatographed on a neutral alumina column. Elution with petroleum ether/CH2Cl2 (2:1) gave a red band, which afforded 4 (7 mg, 17% yield) as dark red crystals. Product 4 was confirmed by comparison of 1H NMR and IR spectra with those of authentic sample prepared according to the published procedure [36]. 4.3. Photolysis of 1 in toluene under trace amounts of air
Fig. 4. Thermal ellipsoid drawing of [SiMe2(h5-C5H4)Fe(CO)2][SiMe2(h5-C5H4) Fe(CO)(SnPh3)H] (8d) showing the labeling scheme and 30% probability ellipsoids. Hydrogens are partly omitted for clarity. Selected bond lengths (Å) and angles (deg): Fe(1)eSi(1) 2.325(2), Fe(1)eSn(1) 2.5540(12), Fe(1)eC(1) 2.097(7), Fe(1)eC(33) 1.701(8), C(1)eSi(2) 1.881(8), Fe(2)eSi(2) 2.303(3), Fe(2)eC(8) 2.095(7), C(8)eSi(1) 1.892(8), Fe(1)Cp(centroid) 1.725, Fe(2)Cp(centroid) 1.710, :Fe(1)eSi(1)C(8) 111.4(2), :Si(1)eC(8)Fe(2) 132.3(4), :C(8)eFe(2)Si(2) 99.1(2), :Fe(2)eSi(2)C(1) 111.6(2), :Si(2)eC(1)Fe(1) 132.4(4), :C(1)eFe(1)Si(1) 99.0(2), :Si(1)eFe(1) C(33) 82.8(2), :Si(1)eFe(1)Sn(1) 113.08(7), :Fe(1)eC(33)O(1) 176.2(7), :CpCp fold angle 1.1.
A solution of 1 (47 mg, 0.10 mmol) in toluene (10 mL) was bubbled with N2 for 10 min; then 1 mL of air was injected, followed by irradiation for 3 h. During this time the solution turned from yellow to red. Using the same separation method described above, a red band gave 5 (44 mg, 91% yield) as dark red crystals. Product 5 was confirmed by comparison of its 1H NMR and IR spectra with those of an authentic sample prepared according to the published procedure [37]. 4.4. Thermal reaction of 5 in xylene A solution of 5 (48 mg, 0.10 mmol) in xylene (10 mL) was refluxed for 30 h. Using the same separation method described above, a yellow band gave 6 (18 mg, 56% yield) as yellow crystals. Product 6 was confirmed by comparison of its 1H NMR and IR spectra with those of an authentic sample prepared according to the published procedure [25]. 4.5. Photolysis of 1 with HSiMePh2
4. Experimental
A solution of 1 (47 mg, 0.10 mmol) and excess HSiMePh2 (198 mg, 1.0 mmol) in toluene (10 mL) was bubbled with N2 for 10 min and then irradiated for 2 h. After removal of the solvent, the residue was chromatographed on an silica gel column. Elution with petroleum ether gave a pale yellow band, which afforded 7a (37 mg, 46% yield) as colorless crystals. 7a, 1H NMR (400 MHz, CDCl3): d ¼ 7.70 (m, 4H, PheH), 7.56 (m, 4H, PheH), 7.38 (m, 6H, PheH), 7.28 (m, 4H, PheH), 5.09 (m, 2H, CpH), 4.88 (m, 2H, CpH), 4.83 (m, 2H, CpH), 3.69 (m, 2H, CpH), 0.97 (s, 6H, SieMe), 0.72 (s, 6H, SieMe), 0.14 (s, 6H, SieMe), 13.33 (s, 2H, FeeH) ppm. 13C{1H} NMR (100 MHz, CDCl3): d ¼ 214.64 (CO), 144.51, 143.73, 134.75, 134.34, 128.52, 128.35, 127.81, 127.71 (Ph), 100.11, 93.78, 90.05, 86.34, 86.29 (Cp), 9.76, 8.50, 7.24 (SieMe) ppm. IR: n ¼ 1935(s) (nCO), 1926(s) (nCO) cm1. C42H48Fe2O2Si4 (808.87): calcd. C 62.37, H 5.98; found C 62.54, H 5.75.
4.1. General considerations
4.6. Photolysis of 1 with HSiMe2Ph
Schlenk and vacuum line techniques were employed for all manipulations. Toluene and xylene were distilled from sodium and benzophenone under nitrogen prior to use. NMR spectra were recorded on a Bruker AV400 instrument at room temperature with TMS as internal standard. IR spectra were recorded as KBr disks on a Nicolet 560 ESP FTIR spectrometer. Elemental analyses were performed on a PerkineElmer 240C analyzer. Photochemical reactions
A solution of 1 (47 mg, 0.10 mmol) and excess HSiMe2Ph (136 mg, 1.0 mmol) in toluene (10 mL) was bubbled with N2 for 10 min and then irradiated for 4 h. Using the same separation method described above, a pale yellow band afforded 7b (36 mg, 53% yield) as colorless crystals. 7b, 1H NMR (400 MHz, CDCl3): d ¼ 7.62 (m, 4H, PheH), 7.35 (m, 6H, PheH), 4.98 (m, 2H, CpH), 4.76 (m, 4H, CpH), 3.73 (m, 2H, CpH), 0.81 (s, 6H, SieMe), 0.58 (s,
Scheme 5. Photoreactions of 2 in the presence of HER3 (E ¼ Si, Ge).
with HER3 (ER3 ¼ SiMePh2, GeEt3) forms the corresponding products (h5,h5:h1-C5H4CMe2C5H3SiMe2)[Fe(CO)2(ER3)][Fe(CO)2] (9a-b), which involves cleavage of the FeeC bond, while the CpFeeSi unit stays unchanged. Photolysis of 2 with H2SiPh2 affords a singlybridged dicyclopentadienyl diiron complex [(h5-C5H4)(h5C5H3(SiHMe2))(CMe2)]Fe2(CO)2(m-CO)2 (11), which contains a FeeFe bond. A plausible mechanism involving two oxidative additions of H2SiPh2 to the two iron centers is proposed.
B. Zhu et al. / Journal of Organometallic Chemistry 813 (2016) 61e70
67
Fig. 5. Thermal ellipsoid drawing of (h5,h5:h1-C5H4CMe2C5H3SiMe2)[Fe(CO)2(SiMePh2)][Fe(CO)2] (9a) showing the labeling scheme and 30% probability ellipsoids. Hydrogens are partly omitted for clarity. Selected bond lengths (Å) and angles (deg): Fe(1)eSi(2) 2.3314(10), Fe(2)eSi(1) 2.3172(11), Si(1)eC(1) 1.892(3), Fe(1)Cp(centroid) 1.727, Fe(2) Cp(centroid) 1.716, :C(1)eC(2)C(13) 125.9(3), :C(2)eC(13)C(8) 113.2(3), :C(13)eC(8)Fe(2) 138.9(2), :C(8)eFe(2)Si(1) 87.54(9), :Fe(2)eSi(1)C(1) 109.92(11), :Si(1) eC(1)C(2) 126.1(2), :CpCp fold angle 94.3.
6H, SieMe), 0.57 (s, 6H, SieMe), 0.20 (s, 6H, SieMe), 13.48 (s, 2H, FeeH) ppm. 13C{1H} NMR (100 MHz, CDCl3): d ¼ 214.60 (CO), 147.08, 133.06, 128.19, 127.86 (Ph), 99.38, 93.45, 89.93, 86.94, 85.23 (Cp), 10.24, 8.57, 8.11, 7.25 (SieMe) ppm. IR: n ¼ 1920(s) (nCO) cm1. C32H44Fe2O2Si4 (684.73): calcd. C 56.13, H 6.48; found C 56.20, H 6.37. 4.7. Photolysis of 1 with HGeEt3 A solution of 1 (47 mg, 0.10 mmol) and excess HGeEt3 (161 mg, 1.0 mmol) in toluene (10 mL) was bubbled with N2 for 10 min and then irradiated for 3 h. Using the same separation method described above, a pale yellow band afforded 7c (25 mg, 34% yield) as colorless crystals. 7c, 1H NMR (400 MHz, CDCl3): d ¼ 5.05 (m, 4H, CpH), 4.82 (m, 2H, CpH), 3.99 (m, 2H, CpH), 1.12 (m, 30H, GeEt), 0.66 (s, 6H, SieMe), 0.25 (s, 6H, SieMe), 13.46 (s, 2H, FeeH) ppm. IR: n ¼ 1917(s) (nCO), 1909(s) (nCO) cm1. C28H52Fe2Ge2O2Si2 (733.84): calcd. C 45.83, H 7.14; found C 46.05, H 7.02.
Scheme 6. A plausible pathway for formation of complexes 9a-b.
4.8. Photolysis of 1 with HSnPh3 A solution of 1 (47 mg, 0.10 mmol) and excess HSnPh3 (351 mg, 1.0 mmol) in toluene (10 mL) was bubbled with N2 for 10 min and
Scheme 7. Photoreaction of 2 in the presence of H2SiPh2.
68
B. Zhu et al. / Journal of Organometallic Chemistry 813 (2016) 61e70
SieMe), 12.92 (s, 2H, FeeH) ppm. IR: n ¼ 1923(s) (nCO) cm1. C52H52Fe2O2Si2Sn2 (1114.27): calcd. C 56.05, H 4.70; found C 56.18, H 4.55. 8d, 1H NMR (400 MHz, CDCl3): d ¼ 7.61 (m, 5H, PheH), 7.34 (m, 10H, PheH), 5.20 (m, 1H, CpH), 5.17 (m, 1H, CpH), 5.09 (m, 1H, CpH), 5.06 (m, 1H, CpH), 4.92 (m, 1H, CpH), 4.87 (m, 1H, CpH), 4.74 (m, 1H, CpH), 4.02 (m, 1H, CpH), 0.62 (s, 3H, SieMe), 0.51 (s, 3H, SieMe), 0.36 (s, 3H, SieMe), 0.07 (s, 3H, SieMe), 12.91 (s, 1H, FeeH) ppm. IR: n ¼ 1988(s) (nCO), 1944(s) (nCO), 1913(s) (nCO) cm1. C35H36Fe2O3Si2Sn (791.24): calcd. C 53.13, H 4.59; found C 53.22, H 4.71. 4.9. Photolysis of 1 with H2SiPh2 A solution of 1 (47 mg, 0.10 mmol) and excess H2SiPh2 (184 mg, 1.0 mmol) in toluene (10 mL) was bubbled with N2 for 10 min and then irradiated for 5 h. Using the same separation method described above, one pale yellow band afforded 7e (24 mg, 31% yield) as colorless crystals. 7e, 1H NMR (400 MHz, CDCl3): d ¼ 7.69 (m, 8H, PheH), 7.32 (m, 12H, PheH), 5.83 (s, 2H, SieH), 4.98 (m, 2H, CpH), 4.95 (m, 4H, CpH), 4.01 (m, 2H, CpH), 0.45 (s, 6H, SieMe), 0.12 (s, 6H, SieMe), 13.22 (s, 2H, FeeH) ppm. 13C{1H} NMR (100 MHz, CDCl3): d ¼ 213.46 (CO), 141.87, 141.28, 134.95, 134.82, 134.76, 128.89, 128.80, 128.01, 127.97 (Ph), 99.53, 93.19, 88.65, 88.26, 86.45 (Cp), 8.88, 8.35 (SieMe) ppm. IR: n ¼ 1930(s) (nCO) cm1. C40H44Fe2O2Si4 (780.82): calcd. C 61.53, H 5.68; found C 61.75, H 5.52. Fig. 6. Thermal ellipsoid drawing of [(h5-C5H4)(h5-C5H3(SiHMe2))(CMe2)]Fe2(CO)2(mCO)2 (11) showing the labeling scheme and 30% probability ellipsoids. Hydrogens are partly omitted for clarity. Selected bond lengths (Å) and angles (deg): Fe(1)eFe(2) 2.465(1), C(1)eC(6) 1.515(5), C(6)eC(9) 1.532(5), C(10)eSi(1) 1.873(4), C(18)eSi(1) 1.852(4), C(19)eSi(1) 1.857(4), Fe(1)Cp(centroid) 1.729, Fe(2)Cp(centroid) 1.727, :C(1)eC(6)C(9) 109.6(3), :C(7)eC(6)C(8) 106.9(3), :C(18)eSi(1)C(19) 109.6(2), :Fe(1)eC(15)Fe(2) 80.45(14), :Fe(1)eC(16)Fe(2) 80.09(13), :C(14)eFe(1)Fe(2) eC(17) 0.7(2), :Cp(centroid)Fe(1)eFe(2)Cp(centroid) 1.5, :CpCp fold angle 107.0.
4.10. Photolysis of 2 with HSiMePh2 A solution of 2 (45 mg, 0.10 mmol) and excess HSiMePh2 (100 mg, 0.50 mmol) in toluene (10 mL) was bubbled with N2 for 10 min and then irradiated for 2 h. Using the same separation method described above, one pale yellow band afforded 9a (27 mg, 42% yield) as colorless crystals. 9a, 1H NMR (400 MHz, CDCl3): d ¼ 7.61 (m, 4H, PheH), 7.33 (m, 6H, PheH), 5.25 (m, 1H, CpH), 5.09 (m, 1H, CpH), 4.90 (m, 1H, CpH), 4.61 (m, 2H, CpH), 4.19 (m, 1H, CpH), 4.08 (m, 1H, CpH), 1.47 (s, 3H, CeMe), 1.31 (s, 3H, CeMe), 0.88 (s, 3H, SieMe), 0.66 (s, 3H, SieMe), 0.51 (s, 3H, SieMe) ppm. 13C{1H} NMR (100 MHz, CDCl3): d ¼ 215.62, 215.11, 214.34 (CO), 144.28, 143.91, 134.47, 134.29, 128.31, 128.25, 128.09, 127.69, 124.55, 111.73 (Ph), 95.81, 91.14, 83.26, 83.14, 81.94, 81.01, 80.67, 80.08 (Cp), 33.90, 33.20, 32.78 (CMe2), 9.43, 7.17, 5.16 (SieMe) ppm. IR: n ¼ 2003(s) (nCO), 1979(s) (nCO), 1935(s) (nCO), 1917(s) (nCO) cm1. C32H32Fe2O4Si2$CH2Cl2 (733.39): calcd. C 54.05, H 4.67; found C 53.92, H 4.43. 4.11. Photolysis of 2 with HSiMePh2
Scheme 8. A plausible pathway for formation of complex 11.
then irradiated for 4 h. Using the same separation method described above, two pale yellow bands afforded 7d (28 mg, 25% yield) and 8d (13 mg, 17% yield) as colorless crystals, respectively. 7d, 1H NMR (400 MHz, CDCl3): d ¼ 7.61 (m, 10H, PheH), 7.35 (m, 20H, PheH), 5.22 (m, 2H, CpH), 5.14 (m, 2H, CpH), 4.90 (m, 2H, CpH), 3.87 (m, 2H, CpH), 0.76 (s, 6H, SieMe), 0.22 (s, 6H,
A solution of 2 (45 mg, 0.10 mmol) and excess HGeEt3 (80 mg, 0.50 mmol) in toluene (10 mL) was bubbled with N2 for 10 min and then irradiated for 2 h. Using the same separation method described above, one pale yellow band afforded 9b (18 mg, 30% yield) as colorless crystals. 9b, 1H NMR (400 MHz, CDCl3): d ¼ 5.33 (m, 1H, CpH), 5.09 (m, 1H, CpH), 4.89 (m, 1H, CpH), 4.83 (m, 1H, CpH), 4.64 (m, 1H, CpH), 4.40 (m, 1H, CpH), 4.35 (m, 1H, CpH), 1.53 (s, 3H, CeMe), 1.37 (s, 3H, CeMe), 1.10 (m, 15H, GeEt), 0.67 (s, 3H, SieMe), 0.54 (s, 3H, SieMe) ppm. IR: n ¼ 2001(s) (nCO), 1979(s) (nCO), 1943(s) (nCO), 1923(s) (nCO) cm1. C25H34Fe2GeO4Si (733.39): calcd. C 49.15, H 5.61; found C 49.36, H 5.57. 4.12. Photolysis of 2 with H2SiPh2 A solution of 2 (45 mg, 0.10 mmol) and excess H2SiPh2 (92 mg, 0.50 mmol) in toluene (10 mL) was bubbled with N2 for 10 min and then irradiated for 2 h. Using the same separation method
B. Zhu et al. / Journal of Organometallic Chemistry 813 (2016) 61e70
69
Table 1 Crystal data and summary of X-ray data collection for 7a, 7c, 7d and 8d.
Empirical formula Fw T [K] Crystal system Space group a [] b [] c [] a [ ] b [ ] g [ ] V [3] Z Dcalc [g,cm3] m [mm1] F(000) Crystal size [mm] Max. 2q [ ] Reflections collected Independent reflns/Rint No. of parameters GOF on F2 R1, wR2 [I > 2s(I)] R1, wR2 (all data) largest diff peak and hole (e Å3)
7a
7c
7d
8d
C42H48Fe2O2Si4 808.86 173(2) Triclinic P1 17.4633(15) 15.8206(14) 15.4938(14) 90 112.041(2) 90 3967.8(6) 4 1.354 0.887 1696 0.18 0.17 0.15 50.02 22639 6991/0.1143 457 1.025 0.0630, 0.1360 0.1293, 0.1689 1.307, 0.610
C28H52Fe2Ge2O2Si2 733.76 173(2) Monoclinic P21/c 14.917(3) 8.6112(17) 14.262(3) 90 116.326(3) 90 1642.0(6) 2 1.484 2.775 760 0.18 0.17 0.15 50.02 9136 2890/0.0295 168 1.039 0.0223, 0.0536 0.0253, 0.0550 0.594, 0.381
C52H52Fe2O2Si2Sn2 1114.20 296(2) Monoclinic P2(1)/n 9.261(3) 14.433(4) 18.238(5) 90 96.145(5) 90 2423.8(12) 2 1.527 1.693 1120 0.18 0.15 0.14 50.02 12253 4264/0.0581 273 1.008 0.0384, 0.0614 0.0827, 0.0732 0.362, 0.413
C35H36Fe2O3Si2Sn 791.21 296(2) Monoclinic P21/c 12.623(4) 14.535(5) 19.259(7) 90 103.268(7) 90 3439(2) 4 1.528 1.655 1600 0.18 0.17 0.15 50.02 19420 6039/0.0976 392 1.013 0.0507, 0.0894 0.1167, 0.1114 0.989, 0.599
Table 2 Crystal data and summary of X-ray data collection for 9a and 11.
Empirical formula Fw T [K] Crystal system Space group a [] b [] c [] a [ ] b [ ] g [ ] V [3] Z Dcalc [g,cm3] m [mm1] F(000) Crystal size [mm] Max. 2q [ ] Reflections collected Independent reflns/Rint No. of parameters GOF on F2 R1, wR2 [I > 2s(I)] R1, wR2 (all data) largest diff peak and hole (e Å3)
9a
11
C33H34Cl2Fe2O4Si2 733.38 173(2) Triclinic P1 11.2675(7) 11.7030(8) 13.0182(8) 106.4390(10) 96.8380(10) 94.7660(10) 1622.40(18) 2 1.501 1.169 756 0.18 0.17 0.15 50.02 9446 5698/0.0241 393 1.005 0.0439, 0.1028 0.0524, 0.1086 1.092, 0.656
C19H20Fe2O4Si 452.14 296(2) Triclinic P1 8.948(4) 9.819(5) 11.917(6) 94.798(8) 92.750(7) 107.209(8) 993.8(8) 2 1.511 1.540 464 0.18 0.14 0.13 50.02 5181 3486/0.0165 239 1.046 0.0370, 0.0873 0.0483, 0.0944 0.298, 0.279
described above, one pale yellow band afforded 10 (17 mg, 27% yield) as colorless crystals, then one red band afforded 11 (7 mg, 15% yield) as dark red crystals. 10, 1H NMR (400 MHz, CDCl3): d ¼ 7.68 (m, 4H, PheH), 7.33 (m, 6H, PheH), 5.60 (m, 1H, SieH), 5.29 (m, 1H, CpH), 5.09 (m, 1H, CpH), 4.90 (m, 1H, CpH), 4.67 (m, 1H, CpH), 4.61 (m, 1H, CpH), 4.34 (m, 1H, CpH), 4.26 (m, 1H, CpH), 1.49 (s, 3H, CeMe), 1.34 (s, 3H, CeMe), 0.66 (s, 3H, SieMe), 0.53 (s, 3H, SieMe) ppm. IR: n ¼ 2002(s) (nCO), 1978(s) (nCO), 1933(s) (nCO), 1915(s) (nCO) cm1. C31H30Fe2O4Si2 (634.44): calcd. C 58.69, H 4.77; found C 58.83, H 4.68. 11, 1H NMR (400 MHz, CDCl3): d ¼ 5.36 (m, 2H, CpH), 5.32 (m, 1H, CpH), 5.16 (m, 2H, CpH), 5.12 (m, 1H, CpH), 5.02 (m, 1H, CpH), 4.94 (m, 1H, SieH), 1.52 (s, 3H, CeMe),
1.46 (s, 3H, CeMe), 0.64 (d, 3H, J ¼ 3.6 Hz, SieMe), 0.30 (d, 3H, J ¼ 3.6 Hz, SieMe) ppm. 13C{1H} NMR (100 MHz, CDCl3): d ¼ 112.20, 108.74, 97.22, 93.73, 91.60, 90.63, 88.62, 83.92, 82.01, 81.97 (Cp), 33.55, 30.34, 29.70 (CMe2), 1.07, 3.55 (SieMe) ppm, the CO resonance was not observed. IR: n ¼ 2026(s) (nCO), 1991(s) (nCO), 1773(s) (nCO) cm1. C19H20Fe2O4Si (452.14): calcd. C 50.47, H 4.46; found C 50.41, H 4.34. 4.13. Crystallographic studies Single crystals of complexes 7a, 7c, 7d, 8d, 9a, and 11 suitable for X-ray diffraction were obtained by crystallization from n-hexane/ CH2Cl2 (1:1). Data collection was performed on a Bruker SMART 1000, using graphite-monochromated Mo Ka radiation (ue2q scans, l ¼ 0.71073 Å). Semiempirical absorption corrections were applied for all complexes. The structures were solved by direct methods and refined by full-matrix least squares. All calculations were using the SHELXTL-97 program system. The crystal data and summary of X-ray data collection are presented in Tables 1 and 2. Acknowledgments This work was financially supported by the National Natural Science Foundation of China (21572160 and 21102101), the Natural Science Foundation of Tianjin (14JCYBJC20300), and the Program for Innovative Research Team in University of Tianjin (TD12-5038). Appendix A. Supplementary data Supplementary data related to this article can be found at http:// dx.doi.org/10.1016/j.jorganchem.2016.04.006. References [1] C.L. Randolph, M.S. Wrighton, J. Am. Chem. Soc. 108 (1986) 3366e3374. [2] L.-S. Luh, Y.-S. Wen, H. Tobita, H. Ogino, Bull. Chem. Soc. Jpn. 71 (1998) 2865e2871. [3] L.-S. Luh, Y.-S. Wen, H. Tobita, H. Ogino, Bull. Chem. Soc. Jpn. 70 (1997) 2193e2200. [4] A. El-Maradny, H. Tobita, H. Ogino, Organometallics 15 (1996) 4954e4958.
70
B. Zhu et al. / Journal of Organometallic Chemistry 813 (2016) 61e70
[5] A. El-Maradny, H. Tobita, H. Ogino, Chem. Lett. (1996) 83e84. [6] H. Tobita, H. Izumi, S. Ohnuki, M.C. Ellerby, M. Kikuchi, S. Inomata, H. Ogino, J. Am. Chem. Soc. 117 (1995) 7013e7014. [7] Y. Kawano, K. Sugawara, H. Tobita, H. Ogino, Chem. Lett. (1994) 293e296. [8] Y. Kawano, H. Tobita, H. Ogino, Organometallics 11 (1992) 499e500. [9] Y. Kawano, H. Tobita, H. Ogino, J. Organomet. Chem. 428 (1992) 125e143. [10] H.K. Sharma, A.J. Metta-Magana, K.H. Pannell, Organometallics 32 (2013) 6218e6225. [11] S.R. Berryhill, G.L. Clevenger, F.Y. Burdurlu, Organometallics 4 (1985) 1509e1515. [12] G. Thum, W. Ries, D. Greissinger, W. Malisch, J. Organomet. Chem. 252 (1983) C67eC72. [13] S.R. Berryhill, B. Sharenow, J. Organomet. Chem. 221 (1981) 143e146. [14] T. Munguia, Z.A. Bakir, F. Cervantus-Lee, A. Metta-Magana, K.H. Pannell, Organometallics 28 (2009) 5777e5782. [15] R.B. King, K.H. Pannell, Inorg. Chem. 7 (1968) 1510e1513. [16] H. Nakazawa, M. Itazaki, K. Kamata, K. Ueda, Chem. Asian J. 2 (2007) 882e888. [17] H. Nakazawa, T. Kawasaki, K. Miyoshi, C.H. Suresh, N. Koga, Organometallics 23 (2004) 117e126. [18] H. Sun, S. Xu, X. Zhou, H. Wang, R. Wang, X. Yao, J. Organomet. Chem. 444 (1993) C41eC43. [19] B. Wang, B. Zhu, J. Zhang, S. Xu, X. Zhou, L. Weng, Organometallics 22 (2003) 5543e5555. [20] M.R. Harpham, S.C. Nguyen, Z. Hou, J.C. Grossman, C.B. Harris, M.W. Mara, A.B. Stickrath, Y. Kanai, A.M. Kolpak, D. Lee, D.-J. Liu, J.P. Lomont, K. MothPoulsen, N. Vinokurov, L.X. Chen, K.P.C. Vollhardt, Angew. Chem. Int. Ed. 51 (2012) 7692e7696. [21] Y. Kanai, V. Srinivasan, S.K. Meier, K.P.C. Vollhardt, J.C. Grossman, Angew.
Chem. Int. Ed. 49 (2010) 8926e8929. Miljani [22] B. Zhu, O.S. c, K.P.C. Vollhardt, M.J. West, Synthesis (2005) 3373e3379. [23] R. Boese, J.K. Cammack, A.J. Matzger, K. Pflug, W.B. Tolman, K.P.C. Vollhardt, T.W. Weidman, J. Am. Chem. Soc. 119 (1997) 6757e6773 (and references therein). [24] K.H. Pannell, M.-C. Brun, H. Sharma, K. Jones, S. Sharma, Organometallics 13 (1994) 1075e1077. [25] H. Tobita, K. Ueno, H. Ogino, Bull. Chem. Soc. Jpn. 61 (1988) 2797e2804. [26] K.H. Pannell, J. Cervantes, C. Hernandez, J. Cassias, S. Vincenti, Organometallics 5 (1986) 1056e1057. [27] M.V. Ovchinnikov, A.M. Ellern, I.A. Guzei, R.J. Angelici, Inorg. Chem. 40 (2001) 7014e7019. [28] M. Amako, J. Schinkel, M.A. Brook, M.J. McGlinchey, J.F. Britten, Organometallics 24 (2005) 1533e1543. [29] Ch Hartinger, T.H. Brehmer, G. Giester, M. Galanski, A.A. Nazarov, S.M. Luther, B.K. Keppler, Inorg. Chim. Acta 328 (2002) 237e240 (and references therein). [30] M. Itazaki, K. Ueda, H. Nakazawa, Angew. Chem. Int. Ed. 48 (2009) 3313e3316. [31] M. Itazaki, M. Kamitani, K. Ueda, H. Nakazawa, Organometallics 28 (2009) 3601e3603. [32] W. van den Berg, J.A.M.T.C. Cromsigt, W.P. Bosman, J.M.M. Smits, R. de Gelder, A.W. Gal, J. Heck, J. Organomet. Chem. 524 (1996) 281e284. [33] B. Zhu, Y. Li, Y. Chen, W. Shi, Organometallics 31 (2012) 3035e3042. [34] B. Zhu, X. Hao, J. Organomet. Chem. 735 (2013) 52e57. [35] R.C. Job, M.D. Curtis, Inorg. Chem. 13 (1973) 2514e2519. [36] P.A. Wegner, V.A. Uski, R.P. Kiester, S. Dabestani, V.W. Day, J. Am. Chem. Soc. 99 (1977) 4846e4848. n, I. Cuadrado, J.R. Masaguer, J. Losada, J. Chem. Soc. Dalton Trans. [37] M. Mora (1988) 833e838.
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry journal homepage: www.elsevier.com/locate/jorganchem
Photochemical reactions of cyclic cyclopentadienyldicarbonyliron silyl complexes Bolin Zhu*, Tian Wang, Yuan Li, Ruichen Sun, Shaonan Wu, Bin Wang Tianjin Key Laboratory of Structure and Performance for Functional Molecules, Key Laboratory of Inorganic-Organic Hybrid Functional Materials Chemistry, Ministry of Education, College of Chemistry, Tianjin Normal University, Tianjin 300387, People's Republic of China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 29 November 2015 Received in revised form 24 February 2016 Accepted 10 April 2016 Available online 12 April 2016
Photolysis of the cyclic cyclopentadienyldicarbonyliron silyl (CpFeeSi) complex [(SiMe2)(h5-C5H4) Fe(CO)2]2 (1) in toluene under N2 results in the SiMe2-bridged complex [(h5-C5H4)2(SiMe2)]Fe2(CO)2(mCO)2 (4), the same reaction in the presence of trace amounts of air affords the SiMe2OSiMe2-bridged complex [(h5-C5H4)2(SiMe2OSiMe2)]Fe2(CO)2(m-CO)2 (5). Photolysis of 1 in the presence of HER3 (E ¼ Si, Ge, Sn) or H2SiPh2 results in the loss of CO and the oxidative addition of the HeE bond to form the corresponding products [(SiMe2)(h5-C5H4)Fe(CO)(ER3)H]2 (7a-e) and [SiMe2(h5-C5H4)Fe(CO)2][SiMe2(h5C5H4)Fe(CO)(SnPh3)H] (8d). Photolysis of the other cyclic CpFeeSi complex (CMe2)(h5-C5H3)(h5,h1-C5H3) [(SiMe2)Fe(CO)2][Fe(CO)2] (2) in the presence of HER3 (ER3 ¼ SiMePh2, GeEt3) forms the corresponding products (h5,h5:h1-C5H4CMe2C5H3SiMe2)[Fe(CO)2(ER3)][Fe(CO)2] (9a-b), which involves cleavage of a FeeC bond. However, Photolysis of 2 with H2SiPh2 affords not only the product 10, the analogue of 9, but also the singly-bridged dicyclopentadienyl diiron complex [(h5-C5H4)(h5-C5H3(SiHMe2))(CMe2)] Fe2(CO)2(m-CO)2 (11), which contains a FeeFe bond. Plausible mechanisms for the formation of the different types of products are proposed. Molecular structures of 7a, 7c, 7d, 8d, 9a, and 11 were determined by X-ray diffraction. © 2016 Elsevier B.V. All rights reserved.
Keywords: Photoreaction FeeSi Oxidative addition of EeH bond (E ¼ Si, Ge, Sn) X-ray diffraction
1. Introduction The cyclopentadienyldicarbonyliron silyl complex (h5-C5R5) Fe(CO)2SiMe3 (R ¼ H or Me) (Chart 1) has attracted considerable interest. Related research is mainly concentrated on the following five aspects: (i) photo-induced oxidative addition of HSiR3 (E ¼ Me, or Et) [1], (ii) photoreaction with H2ER2 or H3ER (E ¼ Si, or Ge) to give m-ER2 or EHR bridged diiron complexes [2e9], (iii) baseinduced metal-to-ring migration of the silyl group [10e14], (iv) ligand exchange reaction [15], (v) and as a catalyst to activate the CeCN bond in acetonitrile [16,17]. In this paper, we focused on two cyclic cyclopentadienyldicarbonyliron silyl (CpFeeSi) complexes, the analogues of (h5-C5R5)Fe(CO)2SiMe3. One is the complex [(SiMe2)(h5-C5H4)Fe(CO)2]2 (1) (Chart 1), which contains two FeeSi units in its cyclic structure. It was first reported by Zhou's group in 1993 and was generated from the thermal rearrangement of the disilane-bridged bis(cyclopentadienyl)tetracarbonyldiiron complex [(h5-C5H4)2(SiMe2SiMe2)]Fe2(CO)2(m-CO)2 (3) (Scheme 1) [18]. The
* Corresponding author. E-mail address: [email protected] (B. Zhu). http://dx.doi.org/10.1016/j.jorganchem.2016.04.006 0022-328X/© 2016 Elsevier B.V. All rights reserved.
other is the complex (CMe2)(h5-C5H3)(h5,h1-C5H3)[(SiMe2)Fe(CO)2] [Fe(CO)2] (2), which contains one FeeSi unit. It was produced by the thermal reaction of the doubly-bridged dicyclopentadienes (C5H4(CMe2))(C5H4(SiMe2)) with Fe(CO)5 [19]. With respect to the “classic” complex (h5-C5R5)Fe(CO)2SiMe3, these two cyclic complexes are air-stable yellow crystalline solids, which are easy to synthesize, handle and store in the long term. These advantages could make them reactivity analogues for the parent complex (h5C5R5)Fe(CO)2SiMe3. In order to compare the reactivity of 1, 2 and (h5-C5R5)Fe(CO)2SiMe3 and to help understand the mechanisms of similar reactions, herein, we report herein our findings on the photochemical reaction of 1, and the photolysis of 1 and 2 in the presence of HER3 (E ¼ Si, Ge, or Sn) and H2SiPh2.
2. Results and discussion 2.1. Photochemistry of 1 Vollhardt et al. have reported an intriguing photo-thermal reversible system which has a potential application as an efficient solar-thermal energy storage device: the diruthenium complex
62
B. Zhu et al. / Journal of Organometallic Chemistry 813 (2016) 61e70
Chart 1. Several types of cyclopentadienyldicarbonyliron silyl complexes.
Scheme 1. Photolysis of 1 under N2 or trace amounts of air.
FvRu2(CO)4 (Fv ¼ h5:h5-bicyclopentadienyl) undergoes rapid isomerization under irradiation to the high-energy complex (m2h1:h5-cyclopentadienyl)2Ru2(CO)4, and the latter reverts to the original one upon heating with an energy release (Scheme 2) [20e23]. Here, the CpFeeSi complex 1 was generated from the thermal rearrangement of complex 3, and we were therefore curious about the photo reversibility of 1. UV irradiation (l ¼ 365 nm) of a solution of 1 in toluene under N2 at 0 C for 10 h produced one identifiable product [(h5-C5H4)2(SiMe2)]Fe2(CO)2(mCO)2 (4) in low yield (17%), a SiMe2-bridged bis(cyclopentadienyl) diiron complex (Scheme 1). Much longer irradiation time did not increase the yield of the product, instead, it led to the serious decomposition of the starting material 1. Unfortunately, complex 1 did not convert to the expected diiron complex 3 to form a photothermal reversible cycle under our current conditions. The formation of 4 indicates that a SiMe2 moiety is cleaved from 1, and then a structural transformation occurs. In hope of trapping this SiMe2 moiety, a toluene solution of 1 and ten-fold excess of hydrosilane (HER3), the silylene-trapping agent, was irradiated under the similar conditions, unfortunately, no the silylene-trapped product
Scheme 2. Photoisomerization of fulvalene(tetracarbonyl)diruthenium.
was detected [24,25]. Instead, the oxidative addition of HeE bond on Fe atoms occurred, and formed the product [(SiMe2)(h5-C5H4) Fe(CO)(ER3)H]2 (see below). A similar expulsion of SiR2 species was reported by Pannell in the photolysis of disilyl iron complex (h5C5H5)Fe(CO)2(SiMe2SiR3) (R ¼ Ph, Me) [26]. When the same reaction was run in the presence of trace amounts of air, surprisingly, complex 1 captured an oxygen during the photo transformation to give SiMe2OSiMe2-bridged bis(cyclopentadienyl) diiron complex 5 in high yield (91%). The mechanism for the conversion of 1 to 5 is unclear. Presumably, trace amounts of air serve as the source of the oxygen atom for the construction of the SiMe2OSiMe2 bridge [27]. In order to determine if complex 5 undergoes a thermal rearrangement reaction, a xylene solution of 5 was refluxed for 30 h. This afforded an unexpected disiloxane-bridged ferrocene Fe[(h5C5H4)SiMe2]2O (6) product in moderate yield (56%) (Scheme 1). Previously, complex 6 was prepared via reaction of 1,10 -dilithioferrocene with dichlorodisiloxane, or via hydrolysis of 1,10 -bis(chlorodimethylsilyl)ferrocene [28,29]. 2.2. Photochemistry of 1 in the presence of HER3 (E ¼ Si, Ge, Sn) or H2SiPh2 Wrighton et al. have reported that photolysis of Cp*Fe(CO)2SiMe3 in the presence of HSiR3 results in the loss of CO and the oxidative addition of HSiR3 to form trans-Cp*Fe(CO)(SiMe3)(SiR3)H, unfortunately, the product was not isolated [1]. Later on, similar complexes CpFe(CO)(SiMe2Ph)2H and CpFe(CO)(SiEt3)(SiMe2Ph)H were synthesized by Nakazawa et al. from the corresponding silyl(pyridine)iron complexes with HSiPhMe2, and also fully characterized [30,31]. By analogy with the reactions of CpFe(CO)2SiMe3,
B. Zhu et al. / Journal of Organometallic Chemistry 813 (2016) 61e70
a series of photoreactions of 1 with HER3 (ER3 ¼ SiMePh2, SiMe2Ph, GeEt3, and SnPh3) were performed. UV photolysis of 1 and excess HER3 in toluene under N2 at 0 C for 2e4 h resulted in the corresponding products [(SiMe2)(h5-C5H4)Fe(CO)(ER3)H]2 (7a-d, 25e53% yields) (Scheme 3), in which oxidative addition of the EeH bond in HER3 occurred at both iron centers. The reaction of 1 with HSnPh3 also afforded product 8d, in which only one iron center was involved the oxidative addition of the SneH bond. In addition, irradiation of 1 with excess H2SiPh2 produced the similar compound 7e through SieH bond oxidative addition. This result is different from the photoreaction of the parent complex Cp*Fe(CO)2SiMe3 with H2SiR2, which generally gave m-SiR2 bridged diiron complexes [6]. This indicates that complex 1 tends to retain its stable six-membered ring structure during the reaction. A plausible mechanism for the formation of 7a-e involves the loss of CO from each iron center in 1 under UV irradiation to give a 16ee unsaturated species, which is followed by oxidative addition of a EeH bond to each metal center. All products were isolated by silica gel column chromatography and well characterized by 1H NMR, IR, and elemental analysis. The structures of 7a, 7c, 7d, and 8d were also confirmed by the single-crystal X-ray diffraction. In the presence of 1 atm CO, a solution of 7a in toluene reacted (45 C, 2 h) to form the original complex 1 (95% yield) and HSiMePh2 (Scheme 4). This is the reverse reaction of the photocatalyzed oxidative addition of the EeH bond described above; a plausible pathway involves reductive elimination of HSiMePh2 followed by CO uptake. 2.3. Molecular structures of 7a, 7c, 7d, and 8d X-ray structural determinations of 7a, 7c and 7d (Figs. 1e3) show their structures to be very similar to one another, all of them have a perfect Ci symmetry, and the six-membered ring FeeSieCeFeeSieC constituting the molecular framework adopts a stable chair conformation, like its parent complex 1. This may account for the robustness of the cyclic system, which remains unchanged throughout the transformation. The metal atoms exhibit a fourlegged piano-stool geometry, the carbonyl and hydrogen on silicon adopt a trans arrangement. The FeeSi bond distance (2.330(2) Å in 7a, 2.3053(7) Å in 7c, 2.339(2) Å in 7d) compares very well with the data (2.315(2) Å) for 1 [18]. The molecular structure of 8d is shown in Fig. 4. It has an asymmetric structure. The six-membered ring Fe(1)eSi(1)eC(8)e Fe(2)eSi(2)eC(1) of the molecular framework also adopts a stable chair conformation. The two cyclopentadienyl rings are almost parallel, as indicated by the small dihedral angle of 1.1. One iron atom exhibits a three-legged piano-stool geometry, with two carbonyls and one silyl group attached. The other iron atom exhibits a
63
four-legged piano-stool geometry, with one carbonyl, one silyl, one hydro and one SnPh3 group attached. The two FeeSi bond distances (2.303(3) Å and 2.325(2) Å) are close to each other, and also consistent with the data (2.315(2) Å) for 1 [18] 2.4. Photochemistry of 2 in the presence of HER3 (ER3 ¼ SiMePh2, GeEt3) or H2SiPh2 Compared to complex 1, complex 2 has an unsymmetrical structure, in which one iron atom is coordinated with a cyclopentadienyl ring in h5 fashion, and the other iron atom is coordinated with two cyclopentadienyl ligands in h5 and h1 fashion at the same time. To understand the reactivity of the two different metal centers, photolysis of 2 in the presence of HER3 (ER3 ¼ SiMePh2, GeEt3) was studied. UV irradiation of 2 and excess HER3 in toluene under N2 at 0 C for 2 h resulted in the corresponding products (h5,h5:h1-C5H4CMe2C5H3SiMe2)[Fe(CO)2(ER3)][Fe(CO)2] (9a-b, 30e42% yields) (Scheme 5). The NMR spectra of 9a-b exhibit seven resonances for the two Cp rings (they display unique ABC and ABCD splitting patterns), two signals for the C(CH3)2 methyl groups and two signals for the Si(CH3)2 methyl groups in the ranges of d 1.53e1.31 and 0.67e0.51, respectively. The IR spectra of 9a-b show the expected four strong n(CO) absorptions (2003, 1979, 1935, 1917 cm1 for 9a, 2001, 1979, 1943, 1923 cm1 for 9b), which correspond to the four terminal CO ligands. The structure of 9a (Fig. 5) was conclusively established by an X-ray crystallographic analysis. Two different iron units Fe(CO)2(SiMePh2) and Fe(CO)2(SiMe2) are both coordinated to the corresponding cyclopentadienyl ring in h5 fashion. The six-membered ring C(1)eC(2)eC(13)eC(8)e Fe(2)eSi(1) constituting the molecular framework adopts a twist boat conformation. Obviously, an FeeC bond in 2 is broken in the course of forming 9a-b, while the fragment (h5-Cp)Fe(CO)2(SiMe2) stays unchanged. The reason that the (h5-Cp)(h1-Cp)Fe(CO)2 fragment in 2 preferentially takes part in the reaction may be due to a decrease in ring strain in products 9a-b arising from the ringopening reaction. A plausible mechanism for the formation of 9a-b is tentatively proposed in Scheme 6. First, a CO is lost from 2 under UV irradiation to give a 16e unsaturated iron species (A); this is followed by oxidative addition of the EH bond in HER3 to form B. In the next step, elimination of Cp and H from B results in intermediate C. Finally, recoordination of CO in C forms the final product 9a-b. Photolysis of 2 and excess H2SiPh2 in toluene under the same conditions affords not only the product (h5,h5:h1-C5H4CMe2C5H3SiMe2)[Fe(CO)2(SiHPh2)][Fe(CO)2] (10), the analogue of 9a-b, but also the singly-bridged dicyclopentadienyl diiron complex [(h5C5H4)(h5-C5H3(SiHMe2))(CMe2)]Fe2(CO)2(m-CO)2 (11), which contains a FeeFe bond. (Scheme 7). The NMR spectrum of 11 exhibits
Scheme 3. Photoreactions of 1 in the presence of HER3 (E ¼ Si, Ge, Sn) or H2SiPh2.
64
B. Zhu et al. / Journal of Organometallic Chemistry 813 (2016) 61e70
Scheme 4. Thermal reaction of 7a under CO (1 atm).
Fig. 1. Thermal ellipsoid drawing of [SiMe2(h5-C5H4)Fe(CO)(SiMePh2)H]2 (7a) showing the labeling scheme and 30% probability ellipsoids. Hydrogens are partly omitted for clarity. Selected bond lengths (Å) and angles (deg): Fe(1)eSi(1) 2.330(2), Fe(1)eSi(2) 2.340(2), Fe(1)eC(18) 1.718(7), C(4)Si(1A) 1.894(6), Fe(1)Cp(centroid) 1.716, :Fe(1A)Si(1A)C(4) 110.44(18), :Si(1A)C(4)eFe(1) 132.5(3), :C(4)eFe(1)Si(1) 99.72(16), :Si(1)eFe(1)C(18) 82.8(2), :Si(1)eFe(1)Si(2) 114.28(7), :Fe(1)eC(18)O(1) 178.4(6), :CpCp fold angle 0.
six resonances for seven inequivalent protons on two Cp rings (two proton peaks overlap), two signals for the C(CH3)2 methyl groups and two signals for the Si(CH3)2 methyl groups at d 1.52, 1.46 and 0.64, 0.30, respectively, and one multiplet at d 4.94 corresponding to the SieH. The IR spectrum of 11 shows n(CO) absorptions at 2021, 1991, and 1773 cm1, indicating the presence of both terminal and bridging CO ligands. A single-crystal X-ray structural determination of 11 shows in Fig. 6. The FeeFe bond distance in 11 (2.465(1) Å) is slightly shorter than that (2.484(6) Å) in its parent complex [(h5C5H4)2CMe2]Fe2(CO)2(m-CO)2, which is consistent with its smaller dihedral angle (:CpCp 107.0 ) than that (109.3 or 109.6 ) in the latter [32]. There is only a small twist around the FeeFe axis; this is reflected by the torsion angles :Cp(centroid)Fe(1)eFe(2) Cp(centroid) (1.5 ) and :C(14)eFe(1)Fe(2)eC(17) (0.7 ). Based on the proposed mechanism described above, it is easy to understand the formation of complex 10. We considered that 11 could be obtained from a further intramolecular SieH bond activation in 10. Therefore the photolysis of 10 in toluene was carried out and indeed yielded product 11 (71%). Although the formation of 11 involves the loss of the SiPh2 moiety from 10, no SiPh2-containing product was separated by column chromatography. On the
basis of our results, a plausible mechanism for the formation of 11 is tentatively proposed in Scheme 8. First, a CO is lost from 10 under UV irradiation to give a 16e unsaturated iron species (A); this is followed by oxidative addition of an adjacent SieH bond on the SiHPh2 group to form B. In the next step, elimination of SiMe2 and H from B results in intermediate C. Finally, C undergoes desilylation (SiPh2) to form the final product 11. Similar destannylation was observed in our previous report on the photolysis of EMe2[(h5C5H4)Fe(CO)2]2SnMe2 (E ¼ C or Si), an analogue of C, which gave the corresponding diiron product [(h5-C5H4)2EMe2]Fe2(CO)2(m-CO)2 [33,34]. Attempts to isolate intermediate C were unsuccessful, which might be due to the instability of the FeeSieFe unit in C. The similar dimethylgermyl compound [(h5-C5H5)Fe(CO)2]2GeMe2 was extremely instable even upon standing in the dark, decomposing to [(h5-C5H5)Fe(CO)2]2 [35]. In order to further support our proposed mechanism, a labeling experiment was carried out to track the two SieH protons in H2SiPh2. Photolysis of 2 and excess D2SiPh2 in toluene generated the corresponding FeeFe-bonded complex [(h5C5H3D)(h5-C5H3(SiDMe2))(CMe2)]Fe2(CO)2(m-CO)2 (11-d2), which is evident in the presence of the same peaks as for 11 in the 1H NMR spectrum, except for the two peaks assigned to the SieH proton and
B. Zhu et al. / Journal of Organometallic Chemistry 813 (2016) 61e70
65
Fig. 2. Thermal ellipsoid drawing of [SiMe2(h5-C5H4)Fe(CO)(GeEt3)H]2 (7c) showing the labeling scheme and 30% probability ellipsoids. Hydrogens are partly omitted for clarity. Selected bond lengths (Å) and angles (deg): Fe(1)Si(1A) 2.3053(7), Fe(1)eGe(1) 2.4207(5), Fe(1)eC(8) 1.721(2), C(1)eSi(1) 1.888(2), Fe(1)Cp(centroid) 1.708, :Fe(1A)Si(1)eC(1) 110.47(7), :Si(1)eC(1)Fe(1) 132.38(11), :C(1)eFe(1)Si(1A) 99.59(6), :Si(1A)Fe(1)eC(8) 86.06(8), :Si(1A)Fe(1)eGe(1) 114.48(2), :Fe(1)eC(8)O(1) 177.5(2), :CpCp fold angle 0.
Fig. 3. Thermal ellipsoid drawing of [SiMe2(h5-C5H4)Fe(CO)(SnPh3)H]2 (7d) showing the labeling scheme and 30% probability ellipsoids. Hydrogens are partly omitted for clarity. Selected bond lengths (Å) and angles (deg): Fe(1)eSi(1) 2.3393(15), Fe(1)eSn(1) 2.5532(9), Fe(1)eC(1) 2.104(4), Fe(1)eC(24) 1.723(6), C(1)Si(1A) 1.893(5), Fe(1)Cp(centroid) 1.720, :Fe(1A)Si(1A)C(1) 111.47(14), :Si(1A)C(1)eFe(1) 132.4(2), :C(1)eFe(1)Si(1) 99.21(13), :Si(1)eFe(1)C(24) 83.20(17), :Si(1)eFe(1)Sn(1) 112.18(4), :Fe(1) eC(24)O(1) 177.2(5), :CpCp fold angle 0.
one proton on the Cp ring (see the supporting information). 3. Conclusions Photolysis of the cyclic CpFeeSi complex [(SiMe2)(h5-C5H4) Fe(CO)2]2 (1) under N2 or trace amounts of air affords the SiMe2bridged complex [(h5-C5H4)2(SiMe2)]Fe2(CO)2(m-CO)2 (4) or the SiMe2OSiMe2-bridged complex [(h5-C5H4)2(SiMe2OSiMe2)] Fe2(CO)2(m-CO)2 (5) respectively, but not the expected complex
[(h5-C5H4)2(SiMe2SiMe2)]Fe2(CO)2(m-CO)2 (3). So the expected photo-thermal reversible cycle between 1 and 3 was not achieved under our conditions. Photolysis of 1 with HER3 (E ¼ Si, Ge, Sn) or H2SiPh2 results in the corresponding oxidative addition products [(SiMe2)(h5-C5H4)Fe(CO)(ER3)H]2 (7a-e) and [SiMe2(h5-C5H4) Fe(CO)2][SiMe2(h5-C5H4)Fe(CO)(SnPh3)H] (8d), which shows that 1 exhibits a reactivity that is similar to that of its parent complex (h5C5Me5)Fe(CO)2SiMe3. Photolysis of the other cyclic CpFeeSi complex (CMe2)(h5-C5H3)(h5,h1-C5H3)[(SiMe2)Fe(CO)2][Fe(CO)2] (2)
66
B. Zhu et al. / Journal of Organometallic Chemistry 813 (2016) 61e70
were carried out at room temperature with a water-jacketed 500 W high-pressure Hg lamp (lmax ¼ 365 nm) as the UV source. The irradiation was conducted in a quartz tube, which was placed adjacent to the lamp, or in 5 mm quartz NMR tubes. Complexes 1 and 2 were prepared by the literature methods [18,19]. 4.2. Photolysis of 1 in toluene under N2 A solution of 1 (47 mg, 0.10 mmol) in toluene (10 mL) was bubbled with N2 for 10 min and then irradiated for 10 h. During this time the solution turned from yellow to red. After removal of the solvent, the residue was chromatographed on a neutral alumina column. Elution with petroleum ether/CH2Cl2 (2:1) gave a red band, which afforded 4 (7 mg, 17% yield) as dark red crystals. Product 4 was confirmed by comparison of 1H NMR and IR spectra with those of authentic sample prepared according to the published procedure [36]. 4.3. Photolysis of 1 in toluene under trace amounts of air
Fig. 4. Thermal ellipsoid drawing of [SiMe2(h5-C5H4)Fe(CO)2][SiMe2(h5-C5H4) Fe(CO)(SnPh3)H] (8d) showing the labeling scheme and 30% probability ellipsoids. Hydrogens are partly omitted for clarity. Selected bond lengths (Å) and angles (deg): Fe(1)eSi(1) 2.325(2), Fe(1)eSn(1) 2.5540(12), Fe(1)eC(1) 2.097(7), Fe(1)eC(33) 1.701(8), C(1)eSi(2) 1.881(8), Fe(2)eSi(2) 2.303(3), Fe(2)eC(8) 2.095(7), C(8)eSi(1) 1.892(8), Fe(1)Cp(centroid) 1.725, Fe(2)Cp(centroid) 1.710, :Fe(1)eSi(1)C(8) 111.4(2), :Si(1)eC(8)Fe(2) 132.3(4), :C(8)eFe(2)Si(2) 99.1(2), :Fe(2)eSi(2)C(1) 111.6(2), :Si(2)eC(1)Fe(1) 132.4(4), :C(1)eFe(1)Si(1) 99.0(2), :Si(1)eFe(1) C(33) 82.8(2), :Si(1)eFe(1)Sn(1) 113.08(7), :Fe(1)eC(33)O(1) 176.2(7), :CpCp fold angle 1.1.
A solution of 1 (47 mg, 0.10 mmol) in toluene (10 mL) was bubbled with N2 for 10 min; then 1 mL of air was injected, followed by irradiation for 3 h. During this time the solution turned from yellow to red. Using the same separation method described above, a red band gave 5 (44 mg, 91% yield) as dark red crystals. Product 5 was confirmed by comparison of its 1H NMR and IR spectra with those of an authentic sample prepared according to the published procedure [37]. 4.4. Thermal reaction of 5 in xylene A solution of 5 (48 mg, 0.10 mmol) in xylene (10 mL) was refluxed for 30 h. Using the same separation method described above, a yellow band gave 6 (18 mg, 56% yield) as yellow crystals. Product 6 was confirmed by comparison of its 1H NMR and IR spectra with those of an authentic sample prepared according to the published procedure [25]. 4.5. Photolysis of 1 with HSiMePh2
4. Experimental
A solution of 1 (47 mg, 0.10 mmol) and excess HSiMePh2 (198 mg, 1.0 mmol) in toluene (10 mL) was bubbled with N2 for 10 min and then irradiated for 2 h. After removal of the solvent, the residue was chromatographed on an silica gel column. Elution with petroleum ether gave a pale yellow band, which afforded 7a (37 mg, 46% yield) as colorless crystals. 7a, 1H NMR (400 MHz, CDCl3): d ¼ 7.70 (m, 4H, PheH), 7.56 (m, 4H, PheH), 7.38 (m, 6H, PheH), 7.28 (m, 4H, PheH), 5.09 (m, 2H, CpH), 4.88 (m, 2H, CpH), 4.83 (m, 2H, CpH), 3.69 (m, 2H, CpH), 0.97 (s, 6H, SieMe), 0.72 (s, 6H, SieMe), 0.14 (s, 6H, SieMe), 13.33 (s, 2H, FeeH) ppm. 13C{1H} NMR (100 MHz, CDCl3): d ¼ 214.64 (CO), 144.51, 143.73, 134.75, 134.34, 128.52, 128.35, 127.81, 127.71 (Ph), 100.11, 93.78, 90.05, 86.34, 86.29 (Cp), 9.76, 8.50, 7.24 (SieMe) ppm. IR: n ¼ 1935(s) (nCO), 1926(s) (nCO) cm1. C42H48Fe2O2Si4 (808.87): calcd. C 62.37, H 5.98; found C 62.54, H 5.75.
4.1. General considerations
4.6. Photolysis of 1 with HSiMe2Ph
Schlenk and vacuum line techniques were employed for all manipulations. Toluene and xylene were distilled from sodium and benzophenone under nitrogen prior to use. NMR spectra were recorded on a Bruker AV400 instrument at room temperature with TMS as internal standard. IR spectra were recorded as KBr disks on a Nicolet 560 ESP FTIR spectrometer. Elemental analyses were performed on a PerkineElmer 240C analyzer. Photochemical reactions
A solution of 1 (47 mg, 0.10 mmol) and excess HSiMe2Ph (136 mg, 1.0 mmol) in toluene (10 mL) was bubbled with N2 for 10 min and then irradiated for 4 h. Using the same separation method described above, a pale yellow band afforded 7b (36 mg, 53% yield) as colorless crystals. 7b, 1H NMR (400 MHz, CDCl3): d ¼ 7.62 (m, 4H, PheH), 7.35 (m, 6H, PheH), 4.98 (m, 2H, CpH), 4.76 (m, 4H, CpH), 3.73 (m, 2H, CpH), 0.81 (s, 6H, SieMe), 0.58 (s,
Scheme 5. Photoreactions of 2 in the presence of HER3 (E ¼ Si, Ge).
with HER3 (ER3 ¼ SiMePh2, GeEt3) forms the corresponding products (h5,h5:h1-C5H4CMe2C5H3SiMe2)[Fe(CO)2(ER3)][Fe(CO)2] (9a-b), which involves cleavage of the FeeC bond, while the CpFeeSi unit stays unchanged. Photolysis of 2 with H2SiPh2 affords a singlybridged dicyclopentadienyl diiron complex [(h5-C5H4)(h5C5H3(SiHMe2))(CMe2)]Fe2(CO)2(m-CO)2 (11), which contains a FeeFe bond. A plausible mechanism involving two oxidative additions of H2SiPh2 to the two iron centers is proposed.
B. Zhu et al. / Journal of Organometallic Chemistry 813 (2016) 61e70
67
Fig. 5. Thermal ellipsoid drawing of (h5,h5:h1-C5H4CMe2C5H3SiMe2)[Fe(CO)2(SiMePh2)][Fe(CO)2] (9a) showing the labeling scheme and 30% probability ellipsoids. Hydrogens are partly omitted for clarity. Selected bond lengths (Å) and angles (deg): Fe(1)eSi(2) 2.3314(10), Fe(2)eSi(1) 2.3172(11), Si(1)eC(1) 1.892(3), Fe(1)Cp(centroid) 1.727, Fe(2) Cp(centroid) 1.716, :C(1)eC(2)C(13) 125.9(3), :C(2)eC(13)C(8) 113.2(3), :C(13)eC(8)Fe(2) 138.9(2), :C(8)eFe(2)Si(1) 87.54(9), :Fe(2)eSi(1)C(1) 109.92(11), :Si(1) eC(1)C(2) 126.1(2), :CpCp fold angle 94.3.
6H, SieMe), 0.57 (s, 6H, SieMe), 0.20 (s, 6H, SieMe), 13.48 (s, 2H, FeeH) ppm. 13C{1H} NMR (100 MHz, CDCl3): d ¼ 214.60 (CO), 147.08, 133.06, 128.19, 127.86 (Ph), 99.38, 93.45, 89.93, 86.94, 85.23 (Cp), 10.24, 8.57, 8.11, 7.25 (SieMe) ppm. IR: n ¼ 1920(s) (nCO) cm1. C32H44Fe2O2Si4 (684.73): calcd. C 56.13, H 6.48; found C 56.20, H 6.37. 4.7. Photolysis of 1 with HGeEt3 A solution of 1 (47 mg, 0.10 mmol) and excess HGeEt3 (161 mg, 1.0 mmol) in toluene (10 mL) was bubbled with N2 for 10 min and then irradiated for 3 h. Using the same separation method described above, a pale yellow band afforded 7c (25 mg, 34% yield) as colorless crystals. 7c, 1H NMR (400 MHz, CDCl3): d ¼ 5.05 (m, 4H, CpH), 4.82 (m, 2H, CpH), 3.99 (m, 2H, CpH), 1.12 (m, 30H, GeEt), 0.66 (s, 6H, SieMe), 0.25 (s, 6H, SieMe), 13.46 (s, 2H, FeeH) ppm. IR: n ¼ 1917(s) (nCO), 1909(s) (nCO) cm1. C28H52Fe2Ge2O2Si2 (733.84): calcd. C 45.83, H 7.14; found C 46.05, H 7.02.
Scheme 6. A plausible pathway for formation of complexes 9a-b.
4.8. Photolysis of 1 with HSnPh3 A solution of 1 (47 mg, 0.10 mmol) and excess HSnPh3 (351 mg, 1.0 mmol) in toluene (10 mL) was bubbled with N2 for 10 min and
Scheme 7. Photoreaction of 2 in the presence of H2SiPh2.
68
B. Zhu et al. / Journal of Organometallic Chemistry 813 (2016) 61e70
SieMe), 12.92 (s, 2H, FeeH) ppm. IR: n ¼ 1923(s) (nCO) cm1. C52H52Fe2O2Si2Sn2 (1114.27): calcd. C 56.05, H 4.70; found C 56.18, H 4.55. 8d, 1H NMR (400 MHz, CDCl3): d ¼ 7.61 (m, 5H, PheH), 7.34 (m, 10H, PheH), 5.20 (m, 1H, CpH), 5.17 (m, 1H, CpH), 5.09 (m, 1H, CpH), 5.06 (m, 1H, CpH), 4.92 (m, 1H, CpH), 4.87 (m, 1H, CpH), 4.74 (m, 1H, CpH), 4.02 (m, 1H, CpH), 0.62 (s, 3H, SieMe), 0.51 (s, 3H, SieMe), 0.36 (s, 3H, SieMe), 0.07 (s, 3H, SieMe), 12.91 (s, 1H, FeeH) ppm. IR: n ¼ 1988(s) (nCO), 1944(s) (nCO), 1913(s) (nCO) cm1. C35H36Fe2O3Si2Sn (791.24): calcd. C 53.13, H 4.59; found C 53.22, H 4.71. 4.9. Photolysis of 1 with H2SiPh2 A solution of 1 (47 mg, 0.10 mmol) and excess H2SiPh2 (184 mg, 1.0 mmol) in toluene (10 mL) was bubbled with N2 for 10 min and then irradiated for 5 h. Using the same separation method described above, one pale yellow band afforded 7e (24 mg, 31% yield) as colorless crystals. 7e, 1H NMR (400 MHz, CDCl3): d ¼ 7.69 (m, 8H, PheH), 7.32 (m, 12H, PheH), 5.83 (s, 2H, SieH), 4.98 (m, 2H, CpH), 4.95 (m, 4H, CpH), 4.01 (m, 2H, CpH), 0.45 (s, 6H, SieMe), 0.12 (s, 6H, SieMe), 13.22 (s, 2H, FeeH) ppm. 13C{1H} NMR (100 MHz, CDCl3): d ¼ 213.46 (CO), 141.87, 141.28, 134.95, 134.82, 134.76, 128.89, 128.80, 128.01, 127.97 (Ph), 99.53, 93.19, 88.65, 88.26, 86.45 (Cp), 8.88, 8.35 (SieMe) ppm. IR: n ¼ 1930(s) (nCO) cm1. C40H44Fe2O2Si4 (780.82): calcd. C 61.53, H 5.68; found C 61.75, H 5.52. Fig. 6. Thermal ellipsoid drawing of [(h5-C5H4)(h5-C5H3(SiHMe2))(CMe2)]Fe2(CO)2(mCO)2 (11) showing the labeling scheme and 30% probability ellipsoids. Hydrogens are partly omitted for clarity. Selected bond lengths (Å) and angles (deg): Fe(1)eFe(2) 2.465(1), C(1)eC(6) 1.515(5), C(6)eC(9) 1.532(5), C(10)eSi(1) 1.873(4), C(18)eSi(1) 1.852(4), C(19)eSi(1) 1.857(4), Fe(1)Cp(centroid) 1.729, Fe(2)Cp(centroid) 1.727, :C(1)eC(6)C(9) 109.6(3), :C(7)eC(6)C(8) 106.9(3), :C(18)eSi(1)C(19) 109.6(2), :Fe(1)eC(15)Fe(2) 80.45(14), :Fe(1)eC(16)Fe(2) 80.09(13), :C(14)eFe(1)Fe(2) eC(17) 0.7(2), :Cp(centroid)Fe(1)eFe(2)Cp(centroid) 1.5, :CpCp fold angle 107.0.
4.10. Photolysis of 2 with HSiMePh2 A solution of 2 (45 mg, 0.10 mmol) and excess HSiMePh2 (100 mg, 0.50 mmol) in toluene (10 mL) was bubbled with N2 for 10 min and then irradiated for 2 h. Using the same separation method described above, one pale yellow band afforded 9a (27 mg, 42% yield) as colorless crystals. 9a, 1H NMR (400 MHz, CDCl3): d ¼ 7.61 (m, 4H, PheH), 7.33 (m, 6H, PheH), 5.25 (m, 1H, CpH), 5.09 (m, 1H, CpH), 4.90 (m, 1H, CpH), 4.61 (m, 2H, CpH), 4.19 (m, 1H, CpH), 4.08 (m, 1H, CpH), 1.47 (s, 3H, CeMe), 1.31 (s, 3H, CeMe), 0.88 (s, 3H, SieMe), 0.66 (s, 3H, SieMe), 0.51 (s, 3H, SieMe) ppm. 13C{1H} NMR (100 MHz, CDCl3): d ¼ 215.62, 215.11, 214.34 (CO), 144.28, 143.91, 134.47, 134.29, 128.31, 128.25, 128.09, 127.69, 124.55, 111.73 (Ph), 95.81, 91.14, 83.26, 83.14, 81.94, 81.01, 80.67, 80.08 (Cp), 33.90, 33.20, 32.78 (CMe2), 9.43, 7.17, 5.16 (SieMe) ppm. IR: n ¼ 2003(s) (nCO), 1979(s) (nCO), 1935(s) (nCO), 1917(s) (nCO) cm1. C32H32Fe2O4Si2$CH2Cl2 (733.39): calcd. C 54.05, H 4.67; found C 53.92, H 4.43. 4.11. Photolysis of 2 with HSiMePh2
Scheme 8. A plausible pathway for formation of complex 11.
then irradiated for 4 h. Using the same separation method described above, two pale yellow bands afforded 7d (28 mg, 25% yield) and 8d (13 mg, 17% yield) as colorless crystals, respectively. 7d, 1H NMR (400 MHz, CDCl3): d ¼ 7.61 (m, 10H, PheH), 7.35 (m, 20H, PheH), 5.22 (m, 2H, CpH), 5.14 (m, 2H, CpH), 4.90 (m, 2H, CpH), 3.87 (m, 2H, CpH), 0.76 (s, 6H, SieMe), 0.22 (s, 6H,
A solution of 2 (45 mg, 0.10 mmol) and excess HGeEt3 (80 mg, 0.50 mmol) in toluene (10 mL) was bubbled with N2 for 10 min and then irradiated for 2 h. Using the same separation method described above, one pale yellow band afforded 9b (18 mg, 30% yield) as colorless crystals. 9b, 1H NMR (400 MHz, CDCl3): d ¼ 5.33 (m, 1H, CpH), 5.09 (m, 1H, CpH), 4.89 (m, 1H, CpH), 4.83 (m, 1H, CpH), 4.64 (m, 1H, CpH), 4.40 (m, 1H, CpH), 4.35 (m, 1H, CpH), 1.53 (s, 3H, CeMe), 1.37 (s, 3H, CeMe), 1.10 (m, 15H, GeEt), 0.67 (s, 3H, SieMe), 0.54 (s, 3H, SieMe) ppm. IR: n ¼ 2001(s) (nCO), 1979(s) (nCO), 1943(s) (nCO), 1923(s) (nCO) cm1. C25H34Fe2GeO4Si (733.39): calcd. C 49.15, H 5.61; found C 49.36, H 5.57. 4.12. Photolysis of 2 with H2SiPh2 A solution of 2 (45 mg, 0.10 mmol) and excess H2SiPh2 (92 mg, 0.50 mmol) in toluene (10 mL) was bubbled with N2 for 10 min and then irradiated for 2 h. Using the same separation method
B. Zhu et al. / Journal of Organometallic Chemistry 813 (2016) 61e70
69
Table 1 Crystal data and summary of X-ray data collection for 7a, 7c, 7d and 8d.
Empirical formula Fw T [K] Crystal system Space group a [] b [] c [] a [ ] b [ ] g [ ] V [3] Z Dcalc [g,cm3] m [mm1] F(000) Crystal size [mm] Max. 2q [ ] Reflections collected Independent reflns/Rint No. of parameters GOF on F2 R1, wR2 [I > 2s(I)] R1, wR2 (all data) largest diff peak and hole (e Å3)
7a
7c
7d
8d
C42H48Fe2O2Si4 808.86 173(2) Triclinic P1 17.4633(15) 15.8206(14) 15.4938(14) 90 112.041(2) 90 3967.8(6) 4 1.354 0.887 1696 0.18 0.17 0.15 50.02 22639 6991/0.1143 457 1.025 0.0630, 0.1360 0.1293, 0.1689 1.307, 0.610
C28H52Fe2Ge2O2Si2 733.76 173(2) Monoclinic P21/c 14.917(3) 8.6112(17) 14.262(3) 90 116.326(3) 90 1642.0(6) 2 1.484 2.775 760 0.18 0.17 0.15 50.02 9136 2890/0.0295 168 1.039 0.0223, 0.0536 0.0253, 0.0550 0.594, 0.381
C52H52Fe2O2Si2Sn2 1114.20 296(2) Monoclinic P2(1)/n 9.261(3) 14.433(4) 18.238(5) 90 96.145(5) 90 2423.8(12) 2 1.527 1.693 1120 0.18 0.15 0.14 50.02 12253 4264/0.0581 273 1.008 0.0384, 0.0614 0.0827, 0.0732 0.362, 0.413
C35H36Fe2O3Si2Sn 791.21 296(2) Monoclinic P21/c 12.623(4) 14.535(5) 19.259(7) 90 103.268(7) 90 3439(2) 4 1.528 1.655 1600 0.18 0.17 0.15 50.02 19420 6039/0.0976 392 1.013 0.0507, 0.0894 0.1167, 0.1114 0.989, 0.599
Table 2 Crystal data and summary of X-ray data collection for 9a and 11.
Empirical formula Fw T [K] Crystal system Space group a [] b [] c [] a [ ] b [ ] g [ ] V [3] Z Dcalc [g,cm3] m [mm1] F(000) Crystal size [mm] Max. 2q [ ] Reflections collected Independent reflns/Rint No. of parameters GOF on F2 R1, wR2 [I > 2s(I)] R1, wR2 (all data) largest diff peak and hole (e Å3)
9a
11
C33H34Cl2Fe2O4Si2 733.38 173(2) Triclinic P1 11.2675(7) 11.7030(8) 13.0182(8) 106.4390(10) 96.8380(10) 94.7660(10) 1622.40(18) 2 1.501 1.169 756 0.18 0.17 0.15 50.02 9446 5698/0.0241 393 1.005 0.0439, 0.1028 0.0524, 0.1086 1.092, 0.656
C19H20Fe2O4Si 452.14 296(2) Triclinic P1 8.948(4) 9.819(5) 11.917(6) 94.798(8) 92.750(7) 107.209(8) 993.8(8) 2 1.511 1.540 464 0.18 0.14 0.13 50.02 5181 3486/0.0165 239 1.046 0.0370, 0.0873 0.0483, 0.0944 0.298, 0.279
described above, one pale yellow band afforded 10 (17 mg, 27% yield) as colorless crystals, then one red band afforded 11 (7 mg, 15% yield) as dark red crystals. 10, 1H NMR (400 MHz, CDCl3): d ¼ 7.68 (m, 4H, PheH), 7.33 (m, 6H, PheH), 5.60 (m, 1H, SieH), 5.29 (m, 1H, CpH), 5.09 (m, 1H, CpH), 4.90 (m, 1H, CpH), 4.67 (m, 1H, CpH), 4.61 (m, 1H, CpH), 4.34 (m, 1H, CpH), 4.26 (m, 1H, CpH), 1.49 (s, 3H, CeMe), 1.34 (s, 3H, CeMe), 0.66 (s, 3H, SieMe), 0.53 (s, 3H, SieMe) ppm. IR: n ¼ 2002(s) (nCO), 1978(s) (nCO), 1933(s) (nCO), 1915(s) (nCO) cm1. C31H30Fe2O4Si2 (634.44): calcd. C 58.69, H 4.77; found C 58.83, H 4.68. 11, 1H NMR (400 MHz, CDCl3): d ¼ 5.36 (m, 2H, CpH), 5.32 (m, 1H, CpH), 5.16 (m, 2H, CpH), 5.12 (m, 1H, CpH), 5.02 (m, 1H, CpH), 4.94 (m, 1H, SieH), 1.52 (s, 3H, CeMe),
1.46 (s, 3H, CeMe), 0.64 (d, 3H, J ¼ 3.6 Hz, SieMe), 0.30 (d, 3H, J ¼ 3.6 Hz, SieMe) ppm. 13C{1H} NMR (100 MHz, CDCl3): d ¼ 112.20, 108.74, 97.22, 93.73, 91.60, 90.63, 88.62, 83.92, 82.01, 81.97 (Cp), 33.55, 30.34, 29.70 (CMe2), 1.07, 3.55 (SieMe) ppm, the CO resonance was not observed. IR: n ¼ 2026(s) (nCO), 1991(s) (nCO), 1773(s) (nCO) cm1. C19H20Fe2O4Si (452.14): calcd. C 50.47, H 4.46; found C 50.41, H 4.34. 4.13. Crystallographic studies Single crystals of complexes 7a, 7c, 7d, 8d, 9a, and 11 suitable for X-ray diffraction were obtained by crystallization from n-hexane/ CH2Cl2 (1:1). Data collection was performed on a Bruker SMART 1000, using graphite-monochromated Mo Ka radiation (ue2q scans, l ¼ 0.71073 Å). Semiempirical absorption corrections were applied for all complexes. The structures were solved by direct methods and refined by full-matrix least squares. All calculations were using the SHELXTL-97 program system. The crystal data and summary of X-ray data collection are presented in Tables 1 and 2. Acknowledgments This work was financially supported by the National Natural Science Foundation of China (21572160 and 21102101), the Natural Science Foundation of Tianjin (14JCYBJC20300), and the Program for Innovative Research Team in University of Tianjin (TD12-5038). Appendix A. Supplementary data Supplementary data related to this article can be found at http:// dx.doi.org/10.1016/j.jorganchem.2016.04.006. References [1] C.L. Randolph, M.S. Wrighton, J. Am. Chem. Soc. 108 (1986) 3366e3374. [2] L.-S. Luh, Y.-S. Wen, H. Tobita, H. Ogino, Bull. Chem. Soc. Jpn. 71 (1998) 2865e2871. [3] L.-S. Luh, Y.-S. Wen, H. Tobita, H. Ogino, Bull. Chem. Soc. Jpn. 70 (1997) 2193e2200. [4] A. El-Maradny, H. Tobita, H. Ogino, Organometallics 15 (1996) 4954e4958.
70
B. Zhu et al. / Journal of Organometallic Chemistry 813 (2016) 61e70
[5] A. El-Maradny, H. Tobita, H. Ogino, Chem. Lett. (1996) 83e84. [6] H. Tobita, H. Izumi, S. Ohnuki, M.C. Ellerby, M. Kikuchi, S. Inomata, H. Ogino, J. Am. Chem. Soc. 117 (1995) 7013e7014. [7] Y. Kawano, K. Sugawara, H. Tobita, H. Ogino, Chem. Lett. (1994) 293e296. [8] Y. Kawano, H. Tobita, H. Ogino, Organometallics 11 (1992) 499e500. [9] Y. Kawano, H. Tobita, H. Ogino, J. Organomet. Chem. 428 (1992) 125e143. [10] H.K. Sharma, A.J. Metta-Magana, K.H. Pannell, Organometallics 32 (2013) 6218e6225. [11] S.R. Berryhill, G.L. Clevenger, F.Y. Burdurlu, Organometallics 4 (1985) 1509e1515. [12] G. Thum, W. Ries, D. Greissinger, W. Malisch, J. Organomet. Chem. 252 (1983) C67eC72. [13] S.R. Berryhill, B. Sharenow, J. Organomet. Chem. 221 (1981) 143e146. [14] T. Munguia, Z.A. Bakir, F. Cervantus-Lee, A. Metta-Magana, K.H. Pannell, Organometallics 28 (2009) 5777e5782. [15] R.B. King, K.H. Pannell, Inorg. Chem. 7 (1968) 1510e1513. [16] H. Nakazawa, M. Itazaki, K. Kamata, K. Ueda, Chem. Asian J. 2 (2007) 882e888. [17] H. Nakazawa, T. Kawasaki, K. Miyoshi, C.H. Suresh, N. Koga, Organometallics 23 (2004) 117e126. [18] H. Sun, S. Xu, X. Zhou, H. Wang, R. Wang, X. Yao, J. Organomet. Chem. 444 (1993) C41eC43. [19] B. Wang, B. Zhu, J. Zhang, S. Xu, X. Zhou, L. Weng, Organometallics 22 (2003) 5543e5555. [20] M.R. Harpham, S.C. Nguyen, Z. Hou, J.C. Grossman, C.B. Harris, M.W. Mara, A.B. Stickrath, Y. Kanai, A.M. Kolpak, D. Lee, D.-J. Liu, J.P. Lomont, K. MothPoulsen, N. Vinokurov, L.X. Chen, K.P.C. Vollhardt, Angew. Chem. Int. Ed. 51 (2012) 7692e7696. [21] Y. Kanai, V. Srinivasan, S.K. Meier, K.P.C. Vollhardt, J.C. Grossman, Angew.
Chem. Int. Ed. 49 (2010) 8926e8929. Miljani [22] B. Zhu, O.S. c, K.P.C. Vollhardt, M.J. West, Synthesis (2005) 3373e3379. [23] R. Boese, J.K. Cammack, A.J. Matzger, K. Pflug, W.B. Tolman, K.P.C. Vollhardt, T.W. Weidman, J. Am. Chem. Soc. 119 (1997) 6757e6773 (and references therein). [24] K.H. Pannell, M.-C. Brun, H. Sharma, K. Jones, S. Sharma, Organometallics 13 (1994) 1075e1077. [25] H. Tobita, K. Ueno, H. Ogino, Bull. Chem. Soc. Jpn. 61 (1988) 2797e2804. [26] K.H. Pannell, J. Cervantes, C. Hernandez, J. Cassias, S. Vincenti, Organometallics 5 (1986) 1056e1057. [27] M.V. Ovchinnikov, A.M. Ellern, I.A. Guzei, R.J. Angelici, Inorg. Chem. 40 (2001) 7014e7019. [28] M. Amako, J. Schinkel, M.A. Brook, M.J. McGlinchey, J.F. Britten, Organometallics 24 (2005) 1533e1543. [29] Ch Hartinger, T.H. Brehmer, G. Giester, M. Galanski, A.A. Nazarov, S.M. Luther, B.K. Keppler, Inorg. Chim. Acta 328 (2002) 237e240 (and references therein). [30] M. Itazaki, K. Ueda, H. Nakazawa, Angew. Chem. Int. Ed. 48 (2009) 3313e3316. [31] M. Itazaki, M. Kamitani, K. Ueda, H. Nakazawa, Organometallics 28 (2009) 3601e3603. [32] W. van den Berg, J.A.M.T.C. Cromsigt, W.P. Bosman, J.M.M. Smits, R. de Gelder, A.W. Gal, J. Heck, J. Organomet. Chem. 524 (1996) 281e284. [33] B. Zhu, Y. Li, Y. Chen, W. Shi, Organometallics 31 (2012) 3035e3042. [34] B. Zhu, X. Hao, J. Organomet. Chem. 735 (2013) 52e57. [35] R.C. Job, M.D. Curtis, Inorg. Chem. 13 (1973) 2514e2519. [36] P.A. Wegner, V.A. Uski, R.P. Kiester, S. Dabestani, V.W. Day, J. Am. Chem. Soc. 99 (1977) 4846e4848. n, I. Cuadrado, J.R. Masaguer, J. Losada, J. Chem. Soc. Dalton Trans. [37] M. Mora (1988) 833e838.