Synthesis and Structural Characterization of Lithium and Titanium

Jun 10, 2016 - ... Kindai University, 3-4-1 Kowakae, Higashi-Osaka, Osaka 577-8502, Japan ... Department of Chemistry, Tokyo Institute of Technology, ...
0 downloads 0 Views 3MB Size
Download PDF
Article pubs.acs.org/IC

Synthesis and Structural Characterization of Lithium and Titanium Complexes Bearing a Bulky Aryloxide Ligand Based on a Rigid FusedRing s‑Hydrindacene Skeleton Shoya Kanazawa,† Taishi Ohira,† Shun Goda,† Naoki Hayakawa,† Tomoharu Tanikawa,† Daisuke Hashizume,‡ Yutaka Ishida,§ Hiroyuki Kawaguchi,§,∥ and Tsukasa Matsuo*,†,∥ †

Department of Applied Chemistry, Faculty of Science and Engineering, Kindai University, 3-4-1 Kowakae, Higashi-Osaka, Osaka 577-8502, Japan ‡ Materials Characterization Support Unit, RIKEN Center for Emergent Matter Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan § Department of Chemistry, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551, Japan ∥ Japan Science and Technology Agency, ACT-C, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan S Supporting Information *

ABSTRACT: The bulky aryl alcohols, (Rind)OH (1) [Rind = EMind (a) and Eind (b)], based on the rigid fused-ring 1,1,3,3,5,5,7,7-octa-R-substituted s-hydrindacene skeleton were prepared by the reaction of (Rind)Li with nitrobenzene followed by protonation. The treatment of 1 with nBuLi affords the lithium aryloxide dimers [(Rind)OLi(THF)]2 (2) or trimers [(Rind)OLi]3 (3), depending on the employed solvents (THF = tetrahydrofuran). The salt metathesis reaction of [(EMind)OLi(THF)]2 (2a) with TiCl4(THF)2 leads to the formation of the mononuclear diamagnetic mono- and bis(aryloxide) Ti(IV) complexes, [(EMind)O]TiCl3(THF) (4a) and [(EMind)O]2TiCl2 (5a). We also isolated a trace amount of the tris(aryloxide) Ti(IV) complex, [(EMind)O]3TiCl (6a). The reaction between 2a and TiCl3(THF)3 resulted in the isolation of the mononuclear paramagnetic mono- and bis(aryloxide) Ti(III) complexes, [(EMind)O]TiCl2(THF)2 (7a) and [(EMind)O]2TiCl(THF)2 (8a). The discrete monomeric structures of the titanium complexes 4a, 5a, 6a, 7a, and 8a were determined by X-ray crystallography.

■

INTRODUCTION

Over the years, considerable efforts have been directed toward studying the synthesis and versatile reactivities of metal aryloxide complexes.1 The replacement of the well-studied cyclopentadienyl-based ligands by the aryloxide-based ligands may provide many opportunities to explore a variety of molecular transformations, as represented by the polymerization reaction of olefins with a structurally well-defined postmetallocene catalyst.2 The aryloxide complexes of transition metals exhibit rather high reactivities attributable to their coordinatively unsaturated nature, which sometimes cause serious side reactions such as ligand disproportionation. To overcome this problem and promote the further stabilization of a low-coordinate metal center, two approaches are mainly employed; one is the installation of sterically bulky monodentate ligands,1b and the other is to make use of the chelating effect with covalently linked multidentate ligands.1c Figure 1 shows the three types of bulky monodentate aryloxide ligands, which are classified by the ease of rotation around the C−C bond between the ortho-carbon atom of the © XXXX American Chemical Society

Figure 1. Three types of bulky aryloxide ligands: 2,6-di-R-substituted aryloxide ligands (A), 2,6-bis(2,6-dialkylphenyl)aryloxide ligands (B), and octa-R-substituted fused-ring aryloxide ligands (C).

central phenol ring and the substituent carbon atom. In the case of the 2,6-di-R-substituted aryloxide ligands (A), the free rotation about the C−C bond is possible in principle. The tertbutyl or phenyl groups have been widely exploited as the ortho R-substituents, but their transition metal complexes have a propensity to experience cyclometalation via an intramolecular Received: April 5, 2016

A

DOI: 10.1021/acs.inorgchem.6b00762 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry

EMind-based aryloxide ligand, (EMind)O−, with Ti(IV) and Ti(III) ions.

C−H bond activation.3 The introduction of a rigid adamantyl group at the ortho position can provide potentially more robust aryloxides as ancillary ligands.4 Recently, the diphenylmethyl group has also been employed in the design of a bulky monodentate aryloxide ligand.5 For the 2,6-bis(2,6-dialkylphenyl)aryloxides, the hindered rotation about the C−C bond is caused by the ortho-substituted biphenyl portion (B).6 In these bulky meta-terphenyl-based aryloxide ligands, an almost orthogonal arrangement of the flanking rings can effectively produce a cavity suitable for the reactive metal center, thus lowering the probability of any intramolecular quenching reactions. In recent years, several group 6 metal alkylidene complexes incorporating the bulky terphenyl-based aryloxide ligand have shown an excellent ability to act as catalysts for olefin metathesis reactions.7 In this context, the utilizations of the 2,6-bis(2,5-R2-pyrrolyl)aryloxides (R = isopropyl and phenyl) have also been investigated.8 We anticipated that the f reeze rotation about the C−C bond in the fused-ring aryloxide systems would provide an adequate space that can maintain the highly reactive species (C). Recently, we focused on the development of a series of bulky 1,1,3,3,5,5,7,7-octa-R-substituted s-hydridacen-4-yl groups, called the “Rind” groups (Chart 1).9 The readily available

■

RESULTS AND DISCUSSION Ligand Synthesis. As shown in Scheme 1, the Rind-based phenols, (Rind)OH (1), were prepared by the Power’s method.6a,b The bulky aryl bromide, (Rind)Br,9 reacted with n BuLi in tetrahydrofuran (THF) to give the bulky aryllithium, (Rind)Li. The subsequent addition of nitrobenzene (PhNO2) followed by protonation with methanol (MeOH) led to the formation of a mixture containing the phenols 1 and (Rind)H, which were separated by silica gel column chromatography. The less bulky EMind- and the bulky Eind-based phenols, (EMind)OH (1a) and (Eind)OH (1b), were isolated as colorless solids in 57% and 43% yield, respectively. Previously, we obtained 1a by a similar synthetic procedure but using bis(trimethylsilyl)peroxide (Me3SiOOSiMe3)13 as the oxygen source in 47% yield.11e The Rind-based phenols 1 were characterized by spectroscopic methods. In the 1H NMR spectra of 1 in C6D6, the hydroxyl proton appears at 4.37 (1a) and 4.33 (1b) ppm. The resonance for the para proton of the phenol ring is also observed at 6.42 (1a) and 6.47 (1b) ppm. In the IR spectra (KBr, pellet), the O−H stretching frequencies are found at 3605 (sharp) and 3438 (broad) (1a), and 3560 (sharp) and 3423 (broad) (1b) cm−1. Figure 2 shows the dimeric molecular arrangements of 1 via intermolecular hydrogen bonds in the crystals determined by an X-ray crystal structure analysis. While the two less bulky EMind groups are parallel to each other around a crystallographic inversion center (Figure 2a), the two bulky Eind groups are mutually twisted (Figure 2b). The O···O atomic distance is observed to be 2.758(2) (1a) and 2.887(2) (1b) Å. Thus, the bulky Eind groups with longer ethyl side chains have a preference to produce the twisted arrangement with a relatively long O···O distance to avoid steric repulsion between the substituents. A related dimer formation was also observed in the crystal of 2,6-bis(2,4,6-trimethylphenyl)phenol with the O···O distance of 2.823(3) Å.6b In contrast, extremely bulky phenol derivatives, 2,6-bis(2,6-diisopropylphenyl)phenol,6a 2,6bis(2,4,6-triisopropylphenyl)phenol, 6 a and 2,6-bis(diphenylmethyl)-4-methylphenol,5 were reported to have a monomeric structure in the crystals. Lithium Aryloxide Complexes. As shown in Scheme 2, the Rind-based phenols 1 smoothly reacted with nBuLi in THF to produce the corresponding lithium derivatives. After the reaction mixture was evaporated to dryness, the residue was washed with hexane or pentane to afford a white powder of the lithium aryloxide complexes, [(EMind)OLi(THF)]2 (2a) and [(Eind)OLi(THF)]2 (2b), in 89% and 88% yields, respectively.

Chart 1. Ligands (Rind)O−

Rind groups have several advantages over the existing bulky aryl groups, as represented by the versatility and size-controllability by the introduction of a variety of R-substituents at the four benzylic positions in the rigid s-hydrindacenyl skeleton. We have already found that the Rind groups can stabilize some reactive species of the main group elements as well as transition metals.10−12 For example, recently we reported the synthesis of a size-selected gold cluster, Au41[S(Eind)]12,12b and a redoxactive [Fe4S4]3+ cluster, [Fe4S4{S(Eind)}4]−,12c using a bulky Rind-based thiol, (Eind)SH. In this paper, we report the synthesis of the bulky phenol derivatives based on the fused-ring Rind groups, (EMind)OH (R1 = Et, R2 = Me) and (Eind)OH (R1 = R2 = Et) (Chart 1), and their lithium salts, and the complexation properties of the Scheme 1. Synthesis of (Rind)OH

B

DOI: 10.1021/acs.inorgchem.6b00762 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry

Figure 2. Dimeric structures of (a) (EMind)OH (1a) and (b) (Eind)OH (1b). The thermal ellipsoids are shown at 50% probability level.

Scheme 2. Synthesis of Dimers of Lithium Aryloxides

Figure 3. (a) Dimeric structure of [(EMind)OLi(Et2O)]2 (2a′). The thermal ellipsoids are shown at 50% probability level. All hydrogen atoms are omitted for clarity. Selected bond distances (Å) and angles (deg): Li1−O1 = 1.819(6), Li1−O1′ = 1.885(6), Li1−O2 = 1.923(6), C1−O1−Li1 = 151.8(3), C1−O1−Li1′ = 123.2(2), Li1−O1−Li1′ = 84.2(3), O1−Li1−O1′ = 95.8(3), O1−Li1−O2 = 122.2(3), O1′−Li1−O2 = 140.7(3). (b) Space-filling model of [(EMind)OLi(Et2O)]2 (2a′): purple, lithium; red, oxygen; gray, carbon; white, hydrogen.

The 1H NMR spectra of 2 in C6D6 showed the aromatic proton signal at 6.20 (2a) and 6.23 (2b) ppm with no appearance of the hydroxyl proton signal. In the 7Li NMR spectra of 2, one resonance appeared at 3.48 (2a) and 3.12 (2b) ppm. The molecular structures of the lithium salts 2 were confirmed by an X-ray crystal structure analysis. Although the refinements were unsatisfactory due to the poor quality of the crystals, preliminary X-ray studies showed that both 2a and 2b assume dimeric structures in the solid state. We also performed an X-ray crystallographic study of [(EMind)OLi(Et2O)]2 (2a′) to obtain a more exact structure, which was prepared by the reaction of 1a with nBuLi in Et2O in 77% yield. As shown in Figure 3, the dimer 2a′ is placed on a crystallographic center of inversion at the center of the Li2O2 core. Each lithium atom has a trigonal planar geometry, whose coordination sphere is completed by one Et2O molecule; the sum of the bond angles around the lithium atom is 358.7°. The two lithium ions asymmetrically bridge the two aryloxide ligands with the bond distances of Li−O1 = 1.819(6) and Li−O1′ = 1.885(6) Å. An

analogous dimeric structure was found in the crystal of the lithium salt of 2,6-di-tert-butyl-4-methylphenoxide, [(2,6-tBu-4Me-C6H2)OLi(Et2O)]2.14 It is noted that 2a′ is dissolved in THF to form 2a by a ligand exchange reaction while maintaining the dimeric structure. We also examined the deprotonation reaction of 1 with n BuLi in hexane from which the cyclic trimers, [(Rind)OLi]3 (3), were obtained as colorless solids in 95% (3a) and 94% (3b) yields (Scheme 3). The 7Li NMR spectra of 3 in C6D6 showed a relatively broad signal at 4.08 (3a) and 3.56 (3b) ppm, which are downfield shifted compared to those of the dimers [3.48 (2a) and 3.12 (2b) ppm], probably due to the noncoordination of the ethereal solvents to the lithium ion. Thus, the trimeric structures of 3 observed in the solid state are maintained in C6D6 on the NMR time scale, unless THF is added to the solution. Although the X-ray diffraction analysis of 3b was not sufficient with a high R value (R = 0.1643) due to the poor crystallinity, the formation of a cyclic trimer was determined, as C

DOI: 10.1021/acs.inorgchem.6b00762 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry

mainly two diamagnetic Ti(IV) species, reasonably assignable to the mono- and bis(aryloxide) complexes. We also investigated the tube reaction between the bulky Eind-based lithium salt 2b and TiCl4(THF)2, resulting in similar 1H NMR spectral profiles due to the mono- and bis(aryloxide) Ti(IV) complexes. On the basis of these NMR tube experiments, the two Ti(IV) complexes were synthesized by the addition of a half molar amount or an equimolar amount of 2a to TiCl4(THF)2 in benzene at room temperature (Scheme 4). After removal of any

Scheme 3. Synthesis of Cyclic Trimers of Lithium Aryloxides

Scheme 4. Synthesis of Titanium(IV) Complexes

depicted in Figure 4. The central Li3O3 core displays a distorted six-membered ring structure, which is surrounded by the three Eind groups meshed together like a molecular gear. The lithium atoms adopt a bent two-coordinate geometry. The O−Li−O angles [122.6(5)−131.0(5)°] are greater than the Li−O−Li angles [105.9(4)−115.8(4)°]. Titanium(IV) Aryloxide Complexes. To elucidate the coordination behavior of the Rind-based monodentate aryloxides, we set out to investigate the transmetalation reaction of the lithium salts 2 with titanium chlorides. First, we performed an NMR tube scale reaction of the less bulky EMind-based 2a with TiCl4(THF)2 in C6D6 at room temperature. The progress of the reaction was monitored by 1 H NMR spectroscopy, indicative of the successive formation of

Figure 4. Trimeric structure of [(Eind)OLi]3 (3b); (a) top view, (b) side view. The thermal ellipsoids are shown at 50% probability level. All hydrogen atoms and a disordered carbon atom of the ethyl group are omitted for clarity. Selected bond distances (Å) and angles (deg): Li1−O1 = 1.809(8), Li1−O2 = 1.844(8), Li2−O2 = 1.783(8), Li2−O3 = 1.770(8), Li3−O1 = 1.814(9), Li3−O3 = 1.837(9), C1−O1−Li1 = 127.1(4), C1− O1−Li3 = 127.0(4), C29−O2−Li1 = 109.1(4), C29−O2−Li2 = 135.7(4), C57−O3−Li2 = 140.7(4), C57−O3−Li3 = 101.3(3), Li1−O1−Li3 = 105.9(4), Li1−O2−Li2 = 114.2(4), Li2−O3−Li3 = 115.8(4), O1−Li1−O2 = 131.0(5), O2−Li2−O3 = 122.6(5), O1−Li3−O3 = 129.8(5). Spacefilling models of [(Eind)OLi]3 (3b); (c) top view, (d) side view: purple, lithium; red, oxygen; gray, carbon; white, hydrogen. D

DOI: 10.1021/acs.inorgchem.6b00762 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry insoluble materials by filtration, the filtrate was evaporated to dryness, and the resulting residue was recrystallized from hexane to afford the dark red crystals of [(EMind)O]TiCl3(THF) (4a) and orange crystals of [(EMind)O]2TiCl2 (5a) in 87% and 76% yields, respectively. On the basis of the NMR and elemental analysis data, while the mono(aryloxide) complex 4a is stabilized by the coordination of one molecule of THF, no THF molecule is coordinated to the Ti(IV) center in the bis(aryloxide) complex 5a due to the steric congestion of the two bulky aryloxide ligands. The molecular structures of 4a and 5a were clearly determined by X-ray crystallography (Figures 5 and 6). The

177.31(10)°. The aryloxide ligand (O1) and the two chlorine atoms (Cl1 and Cl1*) form the equatorial plane; the sum of the bond angles around the titanium atom (∑eq) is 357.48° [O1−Ti1−Cl1 = 120.54(2) and Cl1−Ti1−Cl1′ = 116.40(4)°]. The Ti1−O1 distance of 1.753(2) Å is in the range of those for the typical Ti(IV) aryloxides.1 The Ti1−O1−C1 angle of 174.34(19)° shows an almost linear arrangement, indicative of strong Ti−O(aryloxide) π-bonding interactions. For 5a, the monomeric Ti(IV) center is coordinated by the two aryloxides and the two chlorides in a distorted tetrahedral geometry. The O1−Ti1−O2 angle of 111.64(7)° is larger than the Cl1−Ti1−Cl2 angle of 104.27(3)° due to the steric repulsion between the two bulky aryloxide ligands. The Ti−O− C angles are close to linear [Ti1−O1−C1 = 175.71(13) and Ti1−O2−C25 = 168.66(14)]. While the Ti−O bond lengths in 5a [Ti1−O1 = 1.7599(14) and Ti1−O2 = 1.7621(15) Å] are similar to that in 4a [Ti1−O1 = 1.753(2) Å], the Ti−Cl bond lengths in 5a [Ti1−Cl1 = 2.2110(6) and Ti1−Cl2 = 2.2310(7) Å] are somewhat shorter than those in 4a [Ti1−Cl1 = 2.2413(7) and Ti1−Cl2 = 2.2551(13) Å]. These structural features may be ascribed to the delicate balance between the steric congestion of the bulky aryloxide ligands and the coordination number of the titanium and/or the crystal packing configuration. We also performed the reaction of TiCl4(THF)2 with an excess amount of 2a (ca. 4.2 equiv) in toluene at 70 °C for 6 d, from which a trace amount of the tris(aryloxide) complex, [(EMind)O]3TiCl (6a), was isolated as yellowish-orange crystals, but in an impure form. Nevertheless, the formulation of 6a was confirmed by an X-ray diffraction analysis. Although the refinement of accurate metric parameters could not be obtained because of a relatively high R value (R = 0.1190), the coordination geometry of the complex is evident. As shown in Figure 7, the Ti(IV) atom lies in a distorted tetrahedral manner, producing an EMind-meshed molecular screw with the axis passing through the Ti−Cl bond.

Figure 5. Molecular structure of [(EMind)O]TiCl3(THF) (4a). The thermal ellipsoids are shown at 50% probability level. All hydrogen atoms and Cl2*, O2*, C14*, C15*, and C17* atoms are omitted for clarity. Selected bond distances (Å) and angles (deg): Ti1−Cl1 = 2.2413(7), Ti1−Cl2 = 2.2551(13), Ti1−O1 = 1.753(2), Ti1−O2 = 2.148(3), Cl1−Ti1−Cl1′ = 116.40(4), Cl1−Ti1−Cl2 = 89.67(8), Cl1−Ti1−Cl2* = 99.00(9), Cl1−Ti1−O1 = 120.54(2), Cl1−Ti1−O2 = 78.64(11), Cl1−Ti1−O2* = 90.22(11), Cl2−Ti1−O1 = 97.08(8), Cl2−Ti1−O2 = 167.51(15), Cl2−Ti1−O2* = 177.31(10), O1−Ti1− O2 = 85.31(10), Ti1−O1−C1 = 174.34(19).

Figure 6. Molecular structure of [(EMind)O]2TiCl2 (5a). The thermal ellipsoids are shown at 50% probability level. All hydrogen atoms are omitted for clarity. Selected bond distances (Å) and angles (deg): Ti1−Cl1 = 2.2110(6), Ti1−Cl2 = 2.2310(7), Ti1−O1 = 1.7599(14), Ti1−O2 = 1.7621(15), Cl1−Ti1−Cl2 = 104.27(3), Cl1− Ti1−O1 = 108.11(5), Cl1−Ti1−O2 = 110.88(5), Cl2−Ti1−O1 = 113.37(5), Cl2−Ti1−O2 = 108.34(5), O1−Ti1−O2 = 111.64(7), Ti1−O1−C1 = 175.71(13), Ti1−O2−C25 = 168.66(14). Figure 7. Molecular structure of [(EMind)O]3TiCl (6a). The thermal ellipsoids are shown at 50% probability level. All hydrogen atoms and disordered carbon atoms of the ethyl groups are omitted for clarity. Selected bond distances (Å) and angles (deg): Ti1−Cl1 = 2.2459(13), Ti1−O1 = 1.792(2), Ti1−O2 = 1.782(3), Ti1−O3 = 1.780(3), Cl1− Ti1−O1 = 107.59(9), Cl1−Ti1−O2 = 106.44(11), Cl1−Ti1−O3 = 105.42(10), O1−Ti1−O2 = 111.75(14), O1−Ti1−O3 = 114.02(12), O2−Ti1−O3 = 111.07(12), Ti1−O1−C1 = 161.0(2), Ti1−O2−C25 = 163.1(3), Ti1−O3−C49 = 168.3(2).

discrete molecule of 4a has a mirror plane of symmetry (containing Ti1, O1, C1, C7, and C16 atoms) perpendicular to the aromatic ring. The Ti(IV) ion adopts a slightly distorted trigonal bipyramidal geometry (τ = 0.78 and 0.95),15 where the one chlorine atom (Cl2 or Cl2*) and the coordinated THF molecule (O2 or O2*) occupy the axial positions with the Cl2−Ti1−O2 and Cl2−Ti1−O2* angle of 167.51(15) and E

DOI: 10.1021/acs.inorgchem.6b00762 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry Scheme 5. Synthesis of Titanium(III) Complexes

Titanium(III) Aryloxide Complexes. We also examined the salt metathesis reactions between 2a and TiCl3(THF)3 in THF, as shown in Scheme 5. Depending on the stoichiometric ratio of the reactants, the mononuclear mono- and bis(aryloxide) Ti(III) complexes, [(EMind)O]TiCl2(THF)2 (7a) and [(EMind)O]2TiCl(THF)2 (8a), were obtained as light green and blue crystals in 51% and 77% yields, respectively. These Ti(III) complexes can also be prepared by the reductive treatment of the corresponding Ti(IV) complexes 4a and 5a in THF. The resulting Ti(III) complexes showed a paramagnetic behavior. The effective magnetic moment (μeff) values at 300 K were estimated to be 1.57 (7a) and 1.62 (8a) μB (Evans method),21 comparable to the spin-only value of 1.73 μB for the Ti(III) (S = 1/2) species. The formulations were eventually confirmed by X-ray structural studies (Figures 8 and 9). The X-ray diffraction analysis of 7a shows the presence of two crystallographically independent molecules of the mononuclear complex in the unit cell (molecules A and B). Because

Figure 9. Molecular structure of [(EMind)O]2TiCl(THF)2 (8a) (molecule A). The thermal ellipsoids are shown at 50% probability level. All hydrogen atoms and solvent molecules (benzene) are omitted for clarity. Selected bond distances (Å) and angles (deg): Ti1−Cl1 = 2.3429(11), Ti1−O1 = 1.869(2), Ti1−O2 = 1.871(2), Ti1−O3 = 2.150(3), Ti1−O4 = 2.140(3), Cl1−Ti1−O1 = 103.01(8), Cl1−Ti1−O2 = 105.81(8), Cl1−Ti1−O3 = 93.61(8), Cl1−Ti1−O4 = 92.82(8), O1−Ti1−O2 = 151.17(11), O1−Ti1−O3 = 88.75(10), O1−Ti1−O4 = 89.47(10), O2−Ti1−O3 = 90.34(11), O2−Ti1−O4 = 88.23(10), O3−Ti1−O4 = 173.56(10), Ti1−O1−C1 = 173.9(2), Ti1−O2−C25 = 177.6(2).

the two molecules are structurally similar, some structural features are mentioned only for molecule A (Figure 8). The coordination geometry of the Ti(III) ion is trigonal bipyramidal (τ = 0.88), with the equatorial plane for the aryloxide ligand (O1) and the two chlorine atoms (Cl1 and Cl2) and with the two THF molecules (O2 and O3) at the axial positions with the O2−Ti1−O3 angle of 177.3(3)°. The Ti−O(aryloxide) length [Ti1−O1 = 1.792(6) Å] and the Ti−Cl lengths [Ti1− Cl1 = 2.304(3) and Ti1−Cl2 = 2.309(3) Å] in 7a are longer than those observed in the Ti(IV) complexes (4a, 5a, and 6a) due to the larger ionic radius of Ti(III) compared to Ti(IV). The Ti−O−C(aryloxide) angle was found to be almost linear [Ti1−O1−C1 = 179.1(5)°]. For 8a, an asymmetrical unit consists of two crystallographically independent monomers (molecules A and B). Since their structures are only slightly different with the orientations of the peripheral ethyl side chains, some structural features are

Figure 8. Molecular structure of [(EMind)O]TiCl2(THF)2 (7a) (molecule A). The thermal ellipsoids are shown at 50% probability level. All hydrogen atoms and disordered carbon atoms of THF are omitted for clarity. Selected bond distances (Å) and angles (deg): Ti1−Cl1 = 2.304(3), Ti1−Cl2 = 2.309(3), Ti1−O1 = 1.792(6), Ti1− O2 = 2.128(7), Ti1−O3 = 2.111(6), Cl1−Ti1−Cl2 = 113.09(14), Cl1−Ti1−O1 = 124.23(19), Cl1−Ti1−O2 = 89.86(19), Cl1−Ti1− O3 = 89.27(19), Cl2−Ti1−O1 = 122.7(2), Cl2−Ti1−O2 = 88.7(2), Cl2−Ti1−O3 = 89.30(17), O1−Ti1−O2 = 92.5(3), O1−Ti1−O3 = 90.1(2), O2−Ti1−O3 = 177.3(3). Ti1−O1−C1 = 179.1(5). F

DOI: 10.1021/acs.inorgchem.6b00762 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry

susceptibility was measured by the Evans method21 using a JEOL ECS400 spectrometer in C6D6 at 298 K. Synthesis of (EMind)OH (1a). To a solution of (EMind)Br (5.01 g, 12.4 mmol) in THF (30 mL) was dropwise added nBuLi (2.6 M in hexane, 9.5 mL, 24.7 mmol) at −78 °C. The mixture was stirred and allowed to warm to 0 °C. PhNO2 (3.8 mL, 37.0 mmol) was added to the resulting solution of (EMind)Li at −80 °C. After it stirred at the same temperature for 30 min, the reaction mixture was quenched with MeOH (30 mL) and then 3 M HCl aq (6 mL). The resulting mixture was extracted with Et2O, and the organic layer was dried over Na2SO4. After filtration and removal of the solvent, the residue was purified by silica gel column chromatography using hexane as the eluent to give 1a as a colorless solid (2.42 g, 7.06 mmol, 57%). Analytical data were identical to the reported values.11e 1H NMR (C6D6) δ 0.84 (t, J = 7.3 Hz, 12 H, CH2CH3), 1.43 (s, 12 H, CH3), 1.55−1.64 (m, 8 H, CH2CH3), 1.79 (s, 4 H, CH2), 4.37 (s, 1 H, OH), 6.42 (s, 1 H, ArH). IR (KBr pellet, cm−1) 3605, 3438, 2962, 2939, 2923, 2873, 2854, 1618, 1578, 1460, 1421, 1377, 1219, 1130. Synthesis of (Eind)OH (1b). To a solution of (Eind)Br (10.0 g, 21.7 mmol) in THF (150 mL) was dropwise added nBuLi (2.6 M in hexane, 16.7 mL, 43.4 mmol) at −78 °C. The mixture was stirred and allowed to warm to 0 °C. PhNO2 (6.7 mL, 65.0 mmol) was added to the resulting solution of (Eind)Li at −80 °C. After it stirred at the same temperature for 30 min, the reaction mixture was quenched with MeOH (35 mL) and then 3 M HCl aq (6 mL). The resulting mixture was extracted with Et2O, and the organic layer was dried over Na2SO4. After filtration and removal of the solvent, the residue was purified by silica gel column chromatography using hexane as the eluent to give 1b as a colorless solid (3.71 g, 9.31 mmol, 43%): mp 109−110 °C. 1H NMR (C6D6) δ 0.88 (t × 2, J = 7.3 Hz, 24 H, CH2CH3), 1.55−1.72 (m, 8 H, CH2CH3), 1.76−1.81 (m, 8 H, CH2CH3), 1.76 (s, 4 H, CH2), 4.33 (s, 1 H, OH), 6.47 (s, 1 H, ArH); 13C NMR(C6D6) δ 9.3, 9.6, 32.5, 33.1, 43.4, 49.0, 50.3, 111.9, 131.7, 149.5, 151.2. IR (KBr pellet, cm−1) 3560, 3423, 2957, 2932, 2919, 2874, 2853, 1619, 1578, 1466, 1460, 1378, 1200, 1120. Anal. Calcd for C28H46O: C, 84.36; H, 11.63. Found: C, 84.37; H, 11.72%. Synthesis of [(EMind)OLi(THF)]2 (2a). To a solution of 1a (1.00 g, 2.92 mmol) in THF (20 mL) was dropwise added nBuLi (2.6 M in hexane, 1.2 mL, 3.12 mmol) at 0 °C. The mixture was allowed to warm to room temperature and evaporated to dryness. To the residue was added hexane (10 mL) that formed a white suspension, from which the supernatant was removed. The residue was dried to give 2a as a colorless solid (1.09 g, 1.30 mmol, 89%). 1H NMR (C6D6) δ 0.99 (t, J = 7.3 Hz, 24 H, CH2CH3), 1.07 (br.s, 8 H, THF), 1.76 (s, 24 H, CH3), 1.76−1.82 (m, 16 H, CH2CH3), 2.03 (s, 8 H, CH2), 3.24 (br.s, 8 H, THF), 6.20 (s, 2 H, ArH); 7Li NMR (C6D6) δ 3.48; 13C NMR(C6D6) δ 9.8, 25.0, 30.8, 34.5, 43.1, 49.7, 52.9, 68.4, 104.7, 136.9, 148.8, 161.4. Anal. Calcd for C56H90Li2O4: C, 79.96; H, 10.78. Found: C, 80.03; H, 10.28%. Synthesis of [(Eind)OLi(THF)]2 (2b). To a solution of 1b (2.01 g, 5.04 mmol) in THF (20 mL) was dropwise added nBuLi (2.6 M in hexane, 2.1 mL, 5.46 mmol) at 0 °C. The mixture was allowed to warm to room temperature and evaporated to dryness. To the residue was added pentane (10 mL) that formed a white suspension, from which the supernatant was removed. The residue was dried to give 2b as a colorless solid (2.11 g, 2.21 mmol, 88%). 1H NMR (C6D6) δ 1.02 (m, 24 H, CH2CH3), 1.19 (br.s, 8 H, THF), 1.76−1.84 (m, 16 H, CH2CH3), 2.03−2.07 (m, 16 H, CH2CH3), 1.93 (s, 8 H, CH2), 3.36 (br.s, 8 H, THF), 6.23 (s, 2 H, ArH); 7Li NMR (C6D6) δ 3.12; 13C NMR(C6D6) δ 9.9, 10.7, 25.1, 32.4, 34.1, 41.8, 48.7, 51.2, 68.9, 105.4, 134.1, 150.3, 161.8. Anal. Calcd for C64H106Li2O4: C, 80.63; H, 11.21. Found: C, 79.92; H, 10.58%. Synthesis of [(EMind)OLi(Et2O)]2 (2a′). To a solution of 1a (1.00 g, 2.92 mmol) in Et2O (20 mL) was dropwise added nBuLi (2.6 M in hexane, 2.0 mL, 3.2 mmol) at 0 °C. The mixture was allowed to warm to room temperature and evaporated to dryness. To the residue was added hexane (30 mL) that formed a white suspension, from which the supernatant was removed. The residue was dried to give 2a′ as a colorless solid (0.96 g, 1.13 mmol, 77%). 1H NMR (C6D6) δ 0.74 (t, 12 H, Et2O), 0.96 (t, J = 7.3 Hz, 24 H, CH2CH3), 1.71 (s, 24 H, CH3),

mentioned only for molecule A (Figure 9). The geometry about the Ti(III) ion may be best described as highly distorted square pyramidal (τ = 0.37) with the basal plane occupied by the two aryloxides (O1 and O2) and the two coordinated THF molecules, and the apical position by the chlorine atom. The Ti−O(aryloxide) and Ti−Cl lengths [Ti1−O1 = 1.869(2) and Ti1−O2 = 1.871(2), and Ti1−Cl1 = 2.3429(11) Å] in 8a tend to be longer than that observed in 7a [Ti1−O1 = 1.792(6) and, Ti1−Cl1 = 2.304(3) and Ti1−Cl2 = 2.309(3) Å], presumably due to the steric hindrance induced by the two bulky aryloxide ligands. The Ti−O−C(aryloxide) angles have an almost linear geometry [Ti1−O1−C1 = 173.9(2) and Ti1−O2−C25 = 177.6(2)°].

■

CONCLUSIONS In this study, we have designed and developed new sterically bulky aryloxide ligands, (Rind)O−, based on a fused-ring octaR-substituted s-hydridacene skeleton. The coordination properties of (Rind)O− have been demonstrated with lithium and titanium ions. While the lithium salts exhibit the dimeric and trimeric nature in the crystals, a series of diamagnetic Ti(IV) and paramagnetic Ti(III) complexes can be isolated as discrete mononuclear molecules, whose structures have been clearly determined by a single-crystal X-ray diffraction analysis. The introduction of a rigid Rind-based monodentate aryloxide, (Rind)O−, may more effectively stabilize a coordinatively unsaturated, highly reactive metal center over the existing bulky aryloxide ligands, thereby providing an exciting opportunity to explore various chemical transformations such as activation of small inorganic molecules. Further studies on the reactivity of the titanium complexes described here as well as other transition metal complexes incorporating the bulky (Rind)O− ligands are now in progress.

■

EXPERIMENTAL SECTION

General Considerations. All manipulations of the air- and/or moisture-sensitive compounds were performed either using standard Schlenk-line techniques or in a glovebox under an inert atmosphere of argon. Anhydrous hexane, benzene, toluene, diethyl ether (Et2O), and THF were dried by passage through columns of activated alumina and supported copper catalyst supplied by Hansen & Co, Ltd. Deuterated benzene (benzene-d6, C6D6) was dried and degassed over a potassium mirror in vacuo prior to use. 4-Bromo-1,1,7,7-tetraethyl-3,3,5,5tetramethyl-s-hydrindacene, (EMind)Br, and 4-bromo-1,1,3,3,5,5,7,7octaethyl-s-hydrindacene, (Eind)Br, were synthesized according to literature methods.9 All other chemicals and gases were used as received. Thin layer chromatography (TLC) was performed on plates coated with 0.25 nm thick Silica Gel 60 F-254 (Merck Ltd). Column chromatography was performed using Kieselgel 60 (70−230 mesh; Merck). Nuclear magnetic resonance (NMR) measurements were performed using a JEOL ECS-400 spectrometer (399.8 MHz for 1H, 155.4 MHz for 7Li, and 100.5 MHz for 13C). Chemical shifts (δ) are given by definition as dimensionless numbers and determined with respect to the residual solvent for 1H (residual C6D5H in C6D6: 1H(δ) = 7.15), external LiCl in D2O for 7Li (7Li(δ) = 0.0), and residual solvent for 13C (C6D6: 13C(δ) = 128.0). The absolute values of the coupling constants are given in Hertz (Hz) regardless of their signs. Multiplicities are abbreviated as singlet (s), doublet (d), triplet (t), quartet (q), multiplet (m), and broad (br). Elemental analyses (C and H) were performed at the Materials Characterization Support Unit of the RIKEN Center for Emergent Matter Science (CEMS), and Tokyo Institute of Technology using an Elementar vario MICRO cube apparatus. Melting points (mp) were determined by a Stanford Research Systems OptiMelt instrument. The solution state magnetic G

DOI: 10.1021/acs.inorgchem.6b00762 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry

2 d, the color of the solution changed to dark green. After the insoluble materials were removed by filtration, the solvent was evaporated to dryness. The residue was recrystallized from a mixture of hexane and THF to afford 8a as blue crystals (832 mg, 0.914 mmol, 77%): mp ≈ 170 °C (dec). Anal. Calcd for C56H90ClO4Ti: C, 73.86; H, 9.96. Found: C, 72.86; H, 9.54%. μeff (Evans method, C6D6, 298 K): 1.62 μ B. X-ray Crystallography. The single crystals suitable for X-ray diffraction were obtained from hexane for 1a, 1b, 3b as colorless blocks, 4a as dark red blocks, 5a as orange blocks, and 6a as yellowishorange blocks, from a mixture of hexane and THF for 7a as green crystals, from a mixture of hexane and Et2O for 2a′ as colorless blocks, and from benzene for 8a as blue blocks. The single crystals were immersed in oil (Immersion Oil, type B: Code 1248, Cargille Laboratories, Inc) and mounted on a RIGAKU AFC-8 diffractometer with a Saturn70 CCD detector for 1b and 7a and a Rigaku AFC-10 diffractometer with a Saturn724+ CCD detector for 1a, 2a′, 3b, 4a, 5a, 6a, and 8a. The diffraction data were collected using Mo Kα radiation (λ = 0.710 73 Å), which was monochromated and focused by a curved graphite monochromator. The specimens were cooled at 90 K for 1b, at 100 K for 1a, 2a′, 3b, 4a, 5a, 6a, and 8a, and at 200 K for 7a in a cold nitrogen stream during the measurements. The integration and scaling of the diffraction data were performed using the programs of CrystalClear.16 Lorentzpolarization and absorption corrections were also performed. The structures were solved by a direct method with the programs of SIR200417 for 1a, 1b, 2a′, 3b, 5a, 7a, and 8a, SIR201118 for 4a and 6a, and refined on F2 by a full-matrix least-squares method using the programs of SHELXL-9719 and SHELEXL-2014.20 Anisotropic atomic displacement parameters were applied to all the non-hydrogen atoms. The hydrogen atoms, except for the OH groups, were placed at calculated positions and refined by applying riding models. The OH hydrogen atoms were located on difference Fourier maps and isotropically refined. Crystal Data for 1a. C24H38O, M = 342.56, crystal size 0.26 × 0.22 × 0.10 mm, monoclinic, space group P21/n (No. 14), a = 10.552(3), b = 18.441(4), c = 11.967(3) Å, β = 115.735(3)°, V = 2097.7(9) Å3, Z = 4, Dx = 1.085 g cm−3, μ(Mo Kα) = 0.063 mm−1, 15 285 reflections collected, 4044 unique reflections, and 238 refined parameters. The final R(F) value was 0.0608 [I > 2σ(I)]. The final wR(F2) value was 0.1256 (all data). The goodness-of-fit on F2 was 1.113. Crystal Data for 1b. C28H46O, M = 398.65, crystal size 0.31 × 0.18 × 0.07 mm, monoclinic, space group C2/c (No. 15), a = 19.295(2), b = 7.9904(10), c = 31.829(4) Å, β = 92.287(3)°, V = 4903.2(11) Å3, Z = 8, Dx = 1.080 g cm−3, μ(Mo Kα) = 0.063 mm−1, 12 145 reflections collected, 5588 unique reflections, and 263 refined parameters. The final R(F) value was 0.0594 [I > 2σ(I)]. The final wR(F2) value was 0.1495 (all data). The goodness-of-fit on F2 was 1.055. Crystal Data for 2a′. C56H94Li2O4, M = 845.24, crystal size 0.20 × 0.11 × 0.06 mm, triclinic, space group P1̅ (No. 2), a = 10.167(6), b = 11.431(8), c = 12.675(9) Å, α = 85.36(4), β = 80.92(4), γ = 68.61(3)°, V = 1354.0(16) Å3, Z = 1, Dx = 1.037 g cm−3, μ(Mo Kα) = 0.062 mm−1, 20 637 reflections collected, 5610 unique reflections, and 290 refined parameters. The final R(F) value was 0.0988 [I > 2σ(I)]. The final wR(F2) value was 0.2032 (all data). The goodness-of-fit on F2 was 1.147. Crystal Data for 3b. C84H135Li3O3, M = 1213.73, crystal size 0.22 × 0.22 × 0.15 mm, monoclinic, space group C2/c (No. 15), a = 38.929(10), b = 12.248(3), c = 33.721(8) Å, β = 108.362(4)°, V = 15259(6) Å3, Z = 8, Dx = 1.057 g cm−3, μ(Mo Kα) = 0.061 mm−1, 119 190 reflections collected, 17 499 unique reflections, and 823 refined parameters. The final R(F) value was 0.1643 [I > 2σ(I)]. The final wR(F2) value was 0.3236 (all data). The goodness-of-fit on F2 was 1.388. Crystal Data for 4a. C28H45Cl3O2Ti, M = 567.89, crystal size 0.15 × 0.10 × 0.07 mm, monoclinic, space group P21/m (No. 11), a = 7.7043(12), b = 17.212(3), c = 11.7704(19) Å, β = 109.117(3)°, V = 1474.8(4) Å3, Z = 2, Dx = 1.279 g cm−3, μ(Mo Kα) = 0.584 mm−1, 29 288 reflections collected, 3453 unique reflections, and 191 refined parameters. The final R(F) value was 0.0504 [I > 2σ(I)]. The final

1.73−1.77 (m, 16 H, CH2CH3), 1.99 (s, 8 H, CH2), 3.10 (t, 8 H, Et2O), 6.15 (s, 2 H, ArH); 7Li NMR (C6D6) δ 3.32; 13C NMR(C6D6) δ 9.8, 14.1, 31.2, 34.6, 43.0, 49.6, 52.6, 65.0, 104.8, 136.7, 148.9, 161.3. Synthesis of [(EMind)OLi]3 (3a). To a solution of 1a (1.00 g, 2.91 mmol) in hexane (20 mL) was dropwise added nBuLi (2.6 M in hexane, 1.2 mL, 3.12 mmol) at 0 °C. The mixture was allowed to warm to room temperature and evaporated to dryness. To the residue was added hexane (10 mL) that formed a white suspension, from which the supernatant was removed. The residue was dried to give 3a as a colorless solid (0.97 g, 0.92 mmol, 95%). 1H NMR (C6D6) δ 0.88 (br.s, 36 H, CH2CH3), 1.54 (s, 36 H, CH3), 1.76−1.82 (m, 16 H, CH2CH3), 2.03 (s, 12 H, CH2), 6.25 (s, 3 H, ArH); 7Li NMR (C6D6) δ 4.08 (br); 13C NMR(C6D6) δ 9.6, 31.3, 33.8, 42.1, 49.4, 52.7, 107.5, 137.1. 150.0, 158.0. Synthesis of [(Eind)OLi]3 (3b). To a solution of 1b (1.95 g, 4.88 mmol) in hexane (70 mL) was dropwise added nBuLi (2.6 M in hexane, 2.1 mL, 5.46 mmol) at 0 °C. The mixture was allowed to warm to room temperature and evaporated to dryness. To the residue was added hexane (20 mL) that formed a white suspension, from which the supernatant was removed. The residue was dried to give 3b as a colorless solid (1.86 g, 1.53 mmol, 94%). 1H NMR (C6D6) δ 0.99 (t, J = 7.3 Hz, 36 H, CH2CH3), 1.54 (s, 36 H, CH3), 1.76−1.82 (m, 16 H, CH2CH3), 2.03 (s, 12 H, CH2), 6.25 (s, 3 H, ArH); 7Li NMR (C6D6) δ 3.56 (br); 13C NMR(C6D6) δ 9.7, 10.2, 33.7, 34.0, 42.1, 48.6, 50.9, 108.2, 134.4, 151.1, 159.1. Synthesis of [(EMind)O]TiCl3(THF) (4a). A 50 mL Schlenk flask was charged with TiCl4(THF)2 (174 mg, 0.521 mmol), 2a (240 mg, 0.285 mmol), and benzene (10 mL). When it was stirred overnight at room temperature, the color of the solution changed to dark red-brown. After the insoluble materials were removed by filtration, the solvent was evaporated to dryness. The residue was recrystallized from hexane to afford 4a as dark red crystals (258 mg, 0.454 mmol, 87%): mp 128− 131 °C (dec). 1H NMR (C6D6) δ 0.78 (t, J = 7.3 Hz, 12 H, CH2CH3), 1.33 (s, 12 H, CH3), 1.25−1.37 (br.s, 4 H, THF), 1.43−1.61 (m, 8 H, CH2CH3), 1.83 (s, 4 H, CH2), 3.64−3.67 (br.s, 4 H, THF), 6.58 (s, 1 H, ArH); 13C NMR(C6D6) δ 9.4, 25.5, 31.3, 33.3, 43.9, 49.6, 53.5, 71.7, 118.4, 139.5, 150.8, 171.6. Anal. Calcd for C28H45Cl3O2Ti: C, 59.22; H, 7.99. Found: C, 59.49; H, 7.98%. Synthesis of [(EMind)O]2TiCl2 (5a). A 50 mL Schlenk flask was charged with TiCl4(THF)2 (178 mg, 0.533 mmol), 2a (499 mg, 0.593 mmol), and benzene (10 mL). When it was stirred overnight at room temperature, the color of the solution changed to orange. After the insoluble materials were removed by filtration, the solvent was evaporated to dryness. The residue was recrystallized from hexane to afford 5a as orange crystals (361 mg, 0.450 mmol, 76%): mp 156−162 °C (dec). 1H NMR (C6D6) δ 0.76 (t, J = 7.3 Hz, 24 H, CH2CH3), 1.51−1.54 (m, 16 H, CH2CH3), 1.73 (s, 24 H, CH3), 1.75 (s, 8 H, CH2), 6.58 (s, 2 H, ArH); 13C NMR(C6D6) δ 9.4, 31.2, 33.8, 43.8, 49.8, 52.6, 116.9, 139.2, 150.7, 166.3. Anal. Calcd for C48H74Cl2O2Ti: C, 71.90; H, 9.30. Found: C, 71.76; H, 8.91%. Synthesis of [(EMind)O]3TiCl (6a). A 50 mL Schlenk flask was charged with TiCl4(THF)2 (49.0 mg, 0.148 mmol), 2a (187 mg, 0.630 mmol), and toluene (3 mL). When it was stirred at 70 °C for 6 d, the color of the solution changed to orange. After the insoluble materials were removed by filtration, the solvent was evaporated to dryness. The residue was recrystallized from hexane to afford a trace amount of 6a as yellow-orange crystals. Synthesis of [(EMind)O]TiCl2(THF)2 (7a). A 50 mL Schlenk flask was charged with TiCl3(THF)3 (438 mg, 1.18 mmol), 2a (495 mg, 0.588 mmol), and THF (4 mL). When it was stirred at room temperature for 2 d, the color of the solution changed to dark green. After the insoluble materials were removed by filtration, the solvent was evaporated to dryness. The residue was recrystallized from a mixture of hexane and THF to afford 7a as light green crystals (365 mg, 0.604 mmol, 51%): mp ≈ 92 °C (dec). Anal. Calcd for C32H53Cl2O3Ti: C, 63.58; H, 8.84. Found: C, 63.04; H, 8.82%. μeff (Evans method, C6D6, 298 K): 1.57 μB. Synthesis of [(EMind)O]2TiCl(THF)2 (8a). A 50 mL Schlenk flask was charged with TiCl3(THF)3 (441 mg, 1.19 mmol), 2a (1.02 g, 1.21 mmol), and THF (4 mL). When it was stirred at room temperature for H

DOI: 10.1021/acs.inorgchem.6b00762 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry wR(F2) value was 0.1081 (all data). The goodness-of-fit on F2 was 1.087. Crystal Data for 5a. C48H74Cl2O2Ti, M = 801.92, crystal size 0.23 × 0.13 × 0.11 mm, monoclinic, space group P21/n (No. 14), a = 10.5148(12), b = 14.6106(18), c = 29.947(4) Å, β = 91.7150(17)°, V = 4598.7(10) Å3, Z = 4, Dx = 1.158 g cm−3, μ(Mo Kα) = 0.337 mm−1, 74 453 reflections collected, 10 546 unique reflections, and 494 refined parameters. The final R(F) value was 0.0586 [I > 2σ(I)]. The final wR(F2) value was 0.1241 (all data). The goodness-of-fit on F2 was 1.145. Crystal Data for 6a. C72H111ClO3Ti, M = 1107.95, crystal size 0.25 × 0.19 × 0.13 mm, monoclinic, space group P21/n (No. 14), a = 10.802(2), b = 24.288(5), c = 25.511(5) Å, β = 98.010(3)°, V = 6628(2) Å3, Z = 4, Dx = 1.110 g cm−3, μ(Mo Kα) = 0.213 mm−1, 29 973 reflections collected, 15 177 unique reflections, and 752 refined parameters. The final R(F) value was 0.1190 [I > 2σ(I)]. The final wR(F2) value was 0.2377 (all data). The goodness-of-fit on F2 was 1.249. Crystal Data for 7a. C32H53Cl2O3Ti, M = 604.54, crystal size 0.18 × 0.16 × 0.14 mm, orthorhombic, space group Pca21 (No. 29), a = 22.037(17), b = 12.339(9), c = 23.767(18) Å, V = 6463(8) Å3, Z = 8, Dx = 1.243 g cm−3, μ(Mo Kα) = 0.460 mm−1, 32 040 reflections collected, 11 304 unique reflections, and 728 refined parameters. The final R(F) value was 0.0778 [I > 2σ(I)]. The final wR(F2) value was 0.2134 (all data). The goodness-of-fit on F2 was 1.047. Crystal Data for 8a. C62H96ClO4Ti, M = 988.73, crystal size 0.40 × 0.21 × 0.15 mm, triclinic, space group P1̅ (No. 2), a = 15.451(2), b = 16.269(2), c = 24.655(3) Å, α = 90.592(3), β = 90.993(3), γ = 112.104(4)°, V = 5740.2(14) Å3, Z = 4, Dx = 1.144 g cm−3, μ(Mo Kα) = 0.240 mm−1, 56 550 reflections collected, 24 183 unique reflections, and 1307 refined parameters. The final R(F) value was 0.0852 [I > 2σ(I)]. The final wR(F2) value was 0.2975 (all data). The goodness-offit on F2 was 1.078.

■

Scientific Research (B) (No. 15H03788). This study was also partially supported by the MEXT-Supported Program for the Strategic Research Foundation at Private Universities 2014− 2018 subsidy from MEXT and Kindai Univ. We are grateful to the RIKEN Materials Characterization Support Unit for the elemental analyses of the samples synthesized in this study.

■

(1) For reviews, see: (a) Bradley, D. C.; Rothwell, I. P.; Singh, A. Alkoxo and Aryloxo Derivatives of Metals; Academic Press: San Diego, CA, 2001. (b) Power, P. P. J. Organomet. Chem. 2004, 689, 3904. (c) Kawaguchi, H.; Matsuo, T. J. Organomet. Chem. 2004, 689, 4228. (d) Matsuo, T.; Kawaguchi, H. Chem. Lett. 2004, 33, 640. (e) Boyle, T. J.; Ottley, L. A. M. Chem. Rev. 2008, 108, 1896. (2) For examples, see: (a) Aihara, H.; Matsuo, T.; Kawaguchi, H. Chem. Commun. 2003, 2204. (b) Ishii, A.; Toda, T.; Nakata, N.; Matsuo, T. J. Am. Chem. Soc. 2009, 131, 13566. (c) Toda, T.; Nakata, N.; Matsuo, T.; Ishii, A. J. Organomet. Chem. 2011, 696, 1258. (d) Nakata, N.; Toda, T.; Matsuo, T.; Ishii, A. Inorg. Chem. 2012, 51, 274. (e) Toda, T.; Nakata, N.; Matsuo, T.; Ishii, A. ACS Catal. 2013, 3, 1764. (f) Nakata, N.; Toda, T.; Matsuo, T.; Ishii, A. Macromolecules 2013, 46, 6758. (g) Toda, T.; Nakata, N.; Matsuo, T.; Ishii, A. RSC Adv. 2015, 5, 88826. (3) (a) Rothwell, I. P. Acc. Chem. Res. 1988, 21, 153. (b) Steffey, B. D.; Chamberlain, L. R.; Chesnut, R. W.; Chebi, D. E.; Fanwick, P. E.; Rothwell, I. P. Organometallics 1989, 8, 1419. (c) Vilardo, J. S.; Lockwood, M. A.; Hanson, L. G.; Clark, J. R.; Parkin, B. C.; Fanwick, P. E.; Rothwell, I. P. J. Chem. Soc., Dalton Trans. 1997, 3353. (d) Thorn, M. G.; Etheridge, Z. C.; Fanwick, P. E.; Rothwell, I. P. J. Organomet. Chem. 1999, 591, 148. (e) Lentz, M. R.; Fanwick, P. E.; Rothwell, I. P. Organometallics 2003, 22, 2259. (4) (a) Watanabe, T.; Ishida, Y.; Matsuo, T.; Kawaguchi, H. Dalton Trans. 2010, 39, 484. (b) Hatanaka, T.; Miyake, R.; Ishida, Y.; Kawaguchi, H. J. Organomet. Chem. 2011, 696, 4046. (c) Peryshkov, D. V.; Forrest, W. P.; Schrock, R. R.; Smith, S. J.; Müller, P. Organometallics 2013, 32, 5256. (d) Kurogi, T.; Ishida, Y.; Hatanaka, T.; Kawaguchi, H. Dalton Trans. 2013, 42, 7510. (e) Conley, M. P.; Forrest, W. P.; Mougel, V.; Copéret, C.; Schrock, R. R. Angew. Chem., Int. Ed. 2014, 53, 14221. (5) (a) Searles, K.; Tran, B. L.; Pink, M.; Chen, C.-H.; Mindiola, D. J. Inorg. Chem. 2013, 52, 11126. (b) Searles, K.; Pinter, B.; Chen, C.-H.; Mindiola, D. J. Organometallics 2014, 33, 4192. (c) Searles, K.; Keijzer, K.; Chen, C.-H.; Baik, M.-H.; Mindiola, D. J. Chem. Commun. 2014, 50, 6267. (d) Searles, K.; Carroll, P. J.; Chen, C.-H.; Pink, M.; Mindiola. Chem. Commun. 2015, 51, 3526. (e) Searles, K.; Carroll, P. J.; Mindiola, D. J. Organometallics 2015, 34, 4641. (6) (a) Stanciu, C.; Olmstead, M. M.; Phillips, A. D.; Stender, M.; Power, P. P. Eur. J. Inorg. Chem. 2003, 2003, 3495. (b) Dickie, D. A.; MacIntosh, I. S.; Ino, D. D.; He, Q.; Labeodan, O. A.; Jennings, M. C.; Schatte, G.; Walsby, C. J.; Clyburne, J. A. C. Can. J. Chem. 2008, 86, 20. (c) Ni, C.; Power, P. P. Chem. Commun. 2009, 5543. (7) (a) Flook, M. M.; Jiang, A. J.; Schrock, R. R.; Müller, P.; Hoveyda, A. H. J. Am. Chem. Soc. 2009, 131, 7962. (b) Flook, M. M.; Gerber, L. C. H.; Debelouchina, G. T.; Schrock, R. R. Macromolecules 2010, 43, 7515. (c) Jiang, A. J.; Zhao, Y.; Schrock, R. R.; Hoveyda, A. H. J. Am. Chem. Soc. 2009, 131, 16630. (d) Marinescu, S. C.; Schrock, R. R.; Müller, P.; Takase, M. K.; Hoveyda, A. H. Organometallics 2011, 30, 1780. (e) Yuan, J.; Schrock, R. R.; Müller, P.; Axtell, J. C.; Dobereiner, G. E. Organometallics 2012, 31, 4650. (f) Schrock, R. R. Dalton Trans. 2011, 40, 7484. (g) Jeong, H.; Kozera, D. J.; Schrock, R. R.; Smith, S. J.; Zhang, J.; Ren, N.; Hillmyer, M. A. Organometallics 2013, 32, 4843. (i) Schowner, R.; Frey, W.; Buchmeiser, M. R. J. Am. Chem. Soc. 2015, 137, 6188. (8) Reithofer, M. R.; Dobereiner, G. E.; Schrock, R. R.; Müller, P. Organometallics 2013, 32, 2489. (9) Matsuo, T.; Suzuki, K.; Fukawa, T.; Li, B.; Ito, M.; Shoji, Y.; Otani, T.; Li, L.; Kobayashi, M.; Hachiya, M.; Tahara, Y.; Hashizume,

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.6b00762. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www. ccdc.ac.uk/data_request. Crstallographic details for (1a) CCDC 1469096 (CIF) Crstallographic details for (1b) CCDC 1469098 (CIF) Crstallographic details for (2a′) CCDC 1472084 (CIF) Crstallographic details for (3b) CCDC 1469100 (CIF) Crstallographic details for (4a) CCDC 1469101 (CIF) Crstallographic details for (5a) CCDC 1469108 (CIF) Crstallographic details for (6a) CCDC 1469102 (CIF) Crstallographic details for (7a) CCDC 1472085 (CIF) Crstallographic details for (8a) CCDC 1469104 (CIF)

■

REFERENCES

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Author Contributions

The manuscript was written through contributions of all the authors. Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS We thank the Ministry of Education, Culture, Sports, Science, and Technology of Japan for Scientific Research on Innovative Areas “Stimuli-responsive Chemical Species for the Creation of Functional Molecules” [No. 2408] (No. 24109003) and I

DOI: 10.1021/acs.inorgchem.6b00762 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry D.; Fukunaga, T.; Fukazawa, A.; Li, Y.; Tsuji, H.; Tamao, K. Bull. Chem. Soc. Jpn. 2011, 84, 1178. (10) For reviews, see: (a) Matsuo, T.; Li, B.; Tamao, K. C. R. Chim. 2010, 13, 1104. (b) Matsuo, T.; Kobayashi, M.; Tamao, K. Dalton Trans. 2010, 39, 9203. (c) Matsuo, T.; Tamao, K. Bull. Chem. Soc. Jpn. 2015, 88, 1201. (11) Main group elements, see: (a) Li, B.; Matsuo, T.; Hashizume, D.; Fueno, H.; Tanaka, K.; Tamao, K. J. Am. Chem. Soc. 2009, 131, 13222. (b) Shoji, Y.; Matsuo, T.; Hashizume, D.; Fueno, H.; Tanaka, K.; Tamao, K. J. Am. Chem. Soc. 2010, 132, 8258. (c) Kobayashi, M.; Matsuo, T.; Fukunaga, T.; Hashizume, D.; Fueno, H.; Tanaka, K.; Tamao, K. J. Am. Chem. Soc. 2010, 132, 15162. (d) Suzuki, K.; Matsuo, T.; Hashizume, D.; Fueno, H.; Tanaka, K.; Tamao, K. Science 2011, 331, 1306. (e) Hachiya, M.; Ito, M.; Matsuo, T.; Hashizume, D.; Fueno, H.; Tanaka, K.; Tamao, K. Org. Lett. 2011, 13, 2666. (f) Shoji, Y.; Matsuo, T.; Hashizume, D.; Gutmann, G. J.; Fueno, H.; Tanaka, K.; Tamao, K. J. Am. Chem. Soc. 2011, 133, 11058. (g) Suzuki, K.; Matsuo, T.; Hashizume, D.; Tamao, K. J. Am. Chem. Soc. 2011, 133, 19710. (h) Li, L.; Fukawa, T.; Matsuo, T.; Hashizume, D.; Fueno, H.; Tanaka, K.; Tamao, K. Nat. Chem. 2012, 4, 361. (i) Kobayashi, M.; Hayakawa, N.; Nakabayashi, K.; Matsuo, T.; Hashizume, D.; Fueno, H.; Tanaka, K.; Tamao, K. Chem. Lett. 2014, 43, 432. (j) Li, B.; Tsujimoto, S.; Li, Y.; Tsuji, H.; Tamao, K.; Hashizume, D.; Matsuo, T. Heteroat. Chem. 2014, 25, 612. (k) Shoji, Y.; Kaneda, S.; Fueno, H.; Tanaka, K.; Tamao, K.; Hashizume, D.; Matsuo, T. Chem. Lett. 2014, 43, 1587. (l) Agou, T.; Hayakawa, N.; Sasamori, T.; Matsuo, T.; Hashizume, D.; Tokitoh, N. Chem. - Eur. J. 2014, 20, 9246. (m) Li, L.; Matsuo, T.; Hashizume, D.; Fueno, H.; Tanaka, K.; Tamao, K. J. Am. Chem. Soc. 2015, 137, 15026. (n) Kobayashi, M.; Hayakawa, N.; Matsuo, T.; Li, B.; Fukunaga, T.; Hashizume, D.; Fueno, H.; Tanaka, K.; Tamao, K. J. Am. Chem. Soc. 2016, 138, 758. (o) Hayakawa, N.; Morimoto, T.; Takagi, A.; Tanikawa, T.; Hashizume, D.; Matsuo, T. Chem. Lett. 2016, 45, 409. (12) Transition metals, see: (a) Ito, M.; Hashizume, D.; Fukunaga, T.; Matsuo, T.; Tamao, K. J. Am. Chem. Soc. 2009, 131, 18024. (b) Nishigaki, J.; Tsunoyama, R.; Tsunoyama, H.; Ichikuni, N.; Yamazoe, S.; Negishi, Y.; Ito, M.; Matsuo, T.; Tamao, K.; Tsukuda, T. J. Am. Chem. Soc. 2012, 134, 14295. (c) Tanifuji, K.; Yamada, N.; Tajima, T.; Sasamori, T.; Tokitoh, N.; Matsuo, T.; Tamao, K.; Ohki, Y.; Tatsumi, K. Inorg. Chem. 2014, 53, 4000. (d) Goda, S.; Nikai, M.; Ito, M.; Hashizume, D.; Tamao, K.; Okazawa, A.; Kojima, N.; Fueno, H.; Tanaka, K.; Kobayashi, Y.; Matsuo, T. Chem. Lett. 2016, 45, 634− 636. (13) Taddei, M.; Ricci, A. Synthesis 1986, 1986, 633. (14) Cetinkaya, B.; Gumrukcu, I.; Lappert, M. F.; Atwood, J. L.; Shakir, R. J. Am. Chem. Soc. 1980, 102, 2086. (15) Addison, A. W.; Rao, T. N.; Reedijk, J.; van Rijn, J.; Verschoor, G. C. J. Chem. Soc., Dalton Trans. 1984, 1349. (16) CrystalClear; Rigaku/MSC, Inc: The Woodlands, TX, 2005. (17) SIR2004: Burla, M. C.; Caliandro, R.; Camalli, M.; Carrozzini, B.; Cascarano, G. L.; De Caro, L.; Giacovazzo, C.; Spagna, R. J. Appl. Crystallogr. 2005, 38, 381. (18) SIR2011: Burla, M. C.; Caliandro, R.; Camalli, M.; Carrozzini, B.; Cascarano, G. L.; Giacovazzo, C.; Mallamo, M.; Mazzone, A.; Polidori, G.; Spagna, R. J. Appl. Crystallogr. 2012, 45, 357. (19) Sheldrick, G. M. Acta Crystallogr., Sect. A: Found. Crystallogr. 2008, 64, 112. (20) Sheldrick, G. M. Acta Crystallogr., Sect. C: Struct. Chem. 2015, 71, 3. (21) (a) Evans, D. F. J. Chem. Soc. 1959, 2003. (b) Bain, G. A.; Berry, J. F. J. Chem. Educ. 2008, 85, 532.

J

DOI: 10.1021/acs.inorgchem.6b00762 Inorg. Chem. XXXX, XXX, XXX−XXX