Rapid Entry to Functionalized Boratabenzene Complexes through

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Rapid Entry to Functionalized Boratabenzene Complexes through Metal-Induced Hydroboration at the Anionic 1-H-Boratabenzene Ligand Yuanyuan Yuan,† Xiufang Wang,† Yuxue Li,† Liyan Fan,‡ Xin Xu,† Yaofeng Chen,*,† Guangyu Li,† and Wei Xia† †

State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Road, Shanghai 200032, People's Republic of China ‡ Department of Chemistry, Tongji University, 1239 Siping Road, Shanghai 200092, People's Republic of China

bS Supporting Information ABSTRACT: The hydroboration of alkenes, alkynes, imines, and carbodiimides using the anionic 1-H-boratabenzene ligand bound to rare-earth (RE = Y, Lu), transition (Zr and Rh), and main-group (Li) metals is reported. This hydroboration is metal ion dependent; in the case of 1-H-boratabenzene transition metal complexes, the reactivity follows the trend RE > Zr > Rh. Hydroboration with 1-H-boratabenzene rare-earth metal complexes works well for a range of unsaturated substrates, including 1-hexene, allyl propyl ether, allyl ether, 3-hexyne, benzylidene-n-propylamine, and N,N0 -diisopropylcarbodiimide, thus generating a series of new alkyl-, alkenyl-, amino-, or amidino-functionalized boratabenzene rare-earth metal complexes in high yields. The reactions are highly anti-Markovnikov selective, and the mechanism has been investigated by deuterium-labeling experiments. In comparison, a 1-H-boratabenzene Zr complex reacts with benzylidene-n-propylamine and N,N0 -diisopropylcarbodiimide, and a 1-H-boratabenzene Rh complex reacts with N,N0 -diisopropylcarbodiimide. In contrast, the 1-H-boratabenzene lithium salt reacts only with the activated substrate benzylidene-n-propylamine at elevated temperature to give the corresponding hydroboration product. Boratabenzene Y complexes undergo ligand redistribution with Rh chlorides to give boratabenzene Rh complexes. Studies of the novel monoanionic amidino-boratabenzene ligand by X-ray diffraction and DFT calculations have revealed interesting structural features.

’ INTRODUCTION Hydroboration, the addition of the BH bond across an unsaturated moiety, is a clean and highly stereospecific reaction and has become a valuable synthetic technique in organic chemistry.1 Hydroboration reactions at organic ancillary ligands on metal complexes to give new metal complexes, however, remain underdeveloped. Erker and co-workers reported the hydroboration of pendant alkenyl arms of group 4 metallocenes with HB(C6F5)2 or BH3 3 THF,2 and Schumann and co-workers reported the hydroboration of pendant alkenyl arms of rare-earth metallocenes with 9-BBN.3 The examples of the hydroboration of unsaturated substrates with boron-containing ligands of metal complexes are even sparser, and to our knowledge, all examples dealt with activated substrates. Parker and co-workers presented the addition of ketones, aldehydes, and CO2 across a BH bond in bis(pyrazolyl)hydroboration zinc complexes;4 Herberhold, Yan, and others showed that the reaction of late transition metal carboranes with methyl acetylene monocarboxylate gives B(3,6)-substituted carborane derivatives;5 Hawthorhe and coworkers disclosed an interesting metal-promoted insertion of 1-butyl acrylate across a BH bond of an exopolyhedral r 2011 American Chemical Society

nido-rhodacarborane, but this reaction is not possible with simple alkenes (e.g., 1-hexene).6 Boratabenzene is a heterocyclic, 6π-electron aromatic anion that has been introduced into organometallic chemistry as an isoelectronic analogue of the well-known cyclopentadienide anion (Cp) (Chart 1).7 Certain metal complexes bearing boratabenzenes show excellent catalytic activities, in particular, for olefin polymerization.8 It was also found that the catalytic behavior of boratabenzene metal complexes is greatly influenced by the boron substituent.8a,c Of the various boratabenzene frameworks, 1-H-boratabenzene is special due to the presence of a reactive BH bond, as compared to the analogous CH bond on the ubiquitous Cp ligand.9 We were intrigued by the possibility that this increased reactivity could be utilized for rapid functionalization of complexes potentially useful in catalytic transformations. Reported herein is the hydroboration of alkene, alkyne, imine, and carbodiimide with 1-H-boratabenzene metal (rare-earth, Zr, Rh, Li) Received: May 13, 2011 Published: July 19, 2011 4330

dx.doi.org/10.1021/om200396k | Organometallics 2011, 30, 4330–4341

Organometallics complexes to form new boratabenzene complexes. Most fascinatingly, 1-H-boratabenzene rare-earth metal complexes even work well for the hydroboration of unactivated, simple alkenes.

’ RESULTS AND DISCUSSION Hydroboration with 1-H-Boratabenzene Rare-Earth Metal Complexes. Divalent and trivalent rare-earth metal borota-

benzene complexes and their reactivities have been recently reported.10 In this study, we initially examined the hydroboration of alkene, alkyne, imine, and carbodiimide substrates with 1-Hboratabenzene rare-earth metal complexes. Yttrium complex [C5H5BH]2YCl (1) was prepared in 71% yield via a metathesis reaction of [C5H5BH]Li with anhydrous YCl3 in toluene. The complex was characterized by NMR (1H, 13C, 11B) spectroscopy and elemental analysis. Chart 1. 6π-Electron Aromatic Anions: Boratabenzene and Cp

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The hydroboration of 1-hexene with 1 in toluene at 75 °C gave the corresponding hydroboration product [C5H5B(CH2)5CH3]2YCl (2) in 89% yield (Scheme 1). As observed in usual olefin hydroboration reactions,11 this hydroboration reaction is also highly anti-Markovnikov selective. The scope of the reactivity was then investigated. In the case of cyclopentadienyl metal complexes, the introduction of functional groups to the substituents on the cyclopentadienyl ring can bring in interesting properties.12 Therefore, the reaction of 1 with an olefin containing an ether functional group, allyl propyl ether, was carried out. This reaction proceeded efficiently at 75 °C and gave the corresponding hydroboration product [C5H5B(CH2)3O(CH2)2CH3]2YCl (3) in 78% yield. Unlike the CH3(CH2)5substituted complex 2, which displays sharp 1H NMR signals for 2-/6-H and 3-/5-H on the boratabenzene ring at room temperature, those of the CH3(CH2)2O(CH2)3-substituted complex 3 are broad at room temperature and become sharp on warming to higher temperature, suggesting a fluxional process involving reversible coordination of the ether functionality on the metal ion. Having succeeded in the reaction of 1 with allyl propyl ether, we extended the substrate to bisallyl ether, which contains two olefin groups. The addition of 1 equiv of the substrate to 1 provides ansa-boratabenzene yttrium complex [C5H5B(CH2)3O(CH2)3BC5H5]YCl (4), resulting from double BH bond additions to the same molecule. Monitoring of the reaction by 1H NMR spectroscopy revealed that 1 reacted with allyl ether to generate the monoaddition product [C5H5B(CH2)3OCH2CHdCH2][C5H5BH]YCl (m) first and then proceeded to

Scheme 1. Hydroboration of Alkene, Alkyne, Imine, and Carbodiimide with 1

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Scheme 2. Hydroboration of Alkene and Carbodiimide with 9

Figure 1. 1H NMR and 2D NMR spectra of 3 and 3-D.

slowly undergo a second intramolecular hydroboration reaction to give the ansa-boratabenzene yttrium complex 4. m also reacts with the allyl ether to afford [C5H5B(CH2)3OCH2CHdCH2]2YCl (5), which is an interesting complex offering the possibility for further functionalization at the olefin moiety. By controlling the molar ratio of 1 to allyl ether to 1:0.9, the monoaddition product m can be obtained as a major product. When m was heated in toluene at 75 °C, the ansa-boratabenzene yttrium complex 4 was isolated in 79% yield. To prepare [C5H5B(CH2)3OCH2CHdCH2]2YCl (5) selectively, a large excess of allyl ether should be used. The reaction of 1 with 10 equiv of allyl ether gave 5 in 77% yield. All complexes 2 to 5 are the anti-Markovnikov products. A deuterium-labeling experiment was performed to provide additional evidence for the hydroboration involving the BH bond in 1. The deuterated parent complex [C5H5BD]2YCl (1-D) was synthesized by the reaction of [C5H5BD]Li with YCl3, followed by the reaction with allyl propyl ether to give the deuterated product [C5H5B(CH2CHDCH2)O(CH2)2CH3]2YCl (3-D). The 1H NMR spectrum has a signal for the H at the γ position to boron in 3-D as a doublet, whereas in the nondeuterated product 3 the same resonance appears as a triplet (Figure 1). Furthermore, the H at the β position relative to boron in 3-D integrates for one, compared to the integration value of two in 3. The 2D NMR spectrum of 3-D in C6H6 was also recorded with C6D6 as an internal standard, showing a signal at 1.77 ppm. These results confirm that one hydrogen at the β position originates from the BH of 1, as expected for the anti-Markovnikov selective hydroboration. The reaction of 1 with alkyne was also investigated. When 3-hexyne is added to 1 at room temperature, the alkenylsubstituted complex [C5H5BC(C2H5)dCH(C2H5)]2YCl (6) was isolated in 72% yield. The addition of the BH bond of the boratabenzene complex across the CtC bond of alkyne is noteworthy, for its potential use for the synthesis of boroncontaining conjugated molecules, which have interesting optoelectronic properties.13 Benzylidene-n-propylamine also reacted

with 1 at 75 °C to give the amino-substituted boratabenzene complex [C5H5BN(nPr)CH2Ph]2YCl (7) in 94% yield. Hydroboration of the carbodiimide, which contains an NdCdN unit, with 1 gave the boratabenzene yttrium chloride [C5H5BN(iPr)CHN(iPr)][C5H5BH]YCl (8) in 90% yield (Scheme 2). The addition of 2 equiv of N,N0 -diisopropylcarbodiimide to 1 did not yield the complex [C5H5BN(iPr)CHN(iPr)]2YCl, even after a week, which can be attributed to the steric bulk of the [C5H5BN(iPr)CHN(iPr)] ligand. The 1H NMR spectrum of 8 shows two sets of boratabenzene signals, one for [C5H5BH] and the other for [C5H5BN(iPr)CHN(iPr)]. The NCHN signal appears as a doublet with a JYH coupling constant of 3.2 Hz due to the YH coupling, indicating an interaction between the amidinate fragment and the Y ion. The 11B NMR spectrum shows two singlets at 36.9 and 34.0 ppm, respectively. It is noteworthy that the reaction of the carbodiimide with 1 is very different from that with Cp3Y, which gives a functionalized Cp ligand with an amidinate fragment linked to the aromatic ring through the CC bond via the addition of a YCp bond to carbodiimide.14 It is also noteworthy that the reaction of the carbodiimide with the lithio-ortho-carborane shows an insertion of carbodiimide into the LiC bond.15 To examine if other 1-H-boratabenzene rare-earth metal complexes could undergo a hydroboration reaction, [C5H5BH]2LuCl (9) was prepared via a metathesis reaction of [C5H5BH]Li with anhydrous LuCl3 in toluene in 87% yield. The choice of the lutetium complex is mainly due to its diamagnetic properties, which are useful for acquiring 1H NMR spectra and for the monitoring of the reactions. The hydroboration of two typical substrates, 1-hexene and N,N0 -diisopropylcarbodiimide, with 9 was tested. Reaction of 1-hexene and N,N0 diisopropylcarbodiimide with 9 afforded the corresponding complexes [C5H5B(CH2)5CH3]2LuCl (10) and [C5H5BN(iPr)CHN(iPr)][C5H5BH]LuCl (11) in 94% and 87% yields, respectively (Scheme 2). Hydroboration with 1-H-Boratabenzene Lithium, Zirconium, and Rhodium Complexes. [C5H5BH]2ZrCl2 (12) was prepared via a metathesis reaction of [C5H5BH]Li with ZrCl4 in ether in 93% yield. [C5H5BH]Rh(PPh3)2 (13) and [C5H5BH]Rh(COD) (14) were prepared by ligand redistributions of [C5H5BH]2YCl (1) with Rh(PPh3)3Cl and [Rh(COD)Cl]2 in toluene in 81% and 83% yields, respectively (Scheme 3). Complexes 1214 were characterized by NMR (1H, 13C, 11B, 31 P) spectroscopy and elemental analysis. 4332


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Scheme 3. Synthesis of 13 and 14

Scheme 4. Synthesis of 18 and 19

[C5H5BH]Li did not yield any product with 1-hexene, 3-hexyne, benzylidene-n-propylamine, and N,N0 -diisopropylcarbodiimide in C6D6 at room temperature or 75 °C, as monitored using 1 H NMR spectroscopy. No reaction was observed in a mixture of C6D6/THF-d8 (v/v = 5:1), where [C5H5BH]Li is soluble, at room temperature; [C5H5BH]Li reacted with benzylidene-npropylamine only at elevated temperature (75 °C) to give the hydroboration product [C5H5BN(nPr)CH2Ph]Li (15). Zirconium complex 12 did not react with 1-hexene and 3-hexyne at room temperature or 75 °C. On the other hand, 12 readily reacted with benzylidene-n-propylamine to give the hydroboration product [C5H5BN(nPr)CH2Ph]2ZrCl2 (16) in 90% yield and with N,N0 -diisopropylcarbodiimide to give an unidentified mixture. The reactivity of rhodium complexes 13 and 14 toward 1-hexene, 3-hexyne, benzylidene-n-propylamine, and N,N0 -diisopropylcarbodiimide was also investigated. Complex 13 reacted with N,N0 -diisopropylcarbodiimide only at 75 °C to afford the hydroboration product [C5H5BN(iPr)CHN(iPr)]Rh(PPh3)2 (17); the reaction is highly selective but slow, and a long reaction time (two weeks) was required to achieve a high conversion. Rhodium complex 14 did not react with any of these test substrates at room temperature or at 75 °C. Therefore, the reactivity of the 1-H-boratabenzene transition metal complexes decreases in the following order: 1(Y) > 12(Zr) > 13(Rh) > 14(Rh), showing the hydroboration at the 1-H-boratabenzene ligand is sensitive to the electronic property of the metal complex. 1-Alkyl- (or 1-alkenyl-) functionalized boratabenzene rhodium complexes could not be synthesized via the hydroboration with 1-H-boratabenzene rhodium complexes. However the highly efficient hydroboration with 1-H-boratabenzene rare-earth metal

Figure 2. ORTEP drawing of 1. Thermal ellipsoids are set at 30% probability; hydrogen atoms are omitted for clarity. Selected bond distances [Å] and angles [deg]: Y1B1 2.837(6), Y1C1 2.750(6), Y1C2 2.710(6), Y1C3 2.674(6), Y1C4 2.695(6), Y1C5 2.730(6), Y1B2 2.850(6), Y1C6 2.735(6), Y1C7 2.689(6), Y1C8 2.692(6), Y1C9 2.710(6), Y1C10 2.721(6), Y1Cl1 2.6810(16), Y1Cl2 2.6738(14), Cl1Y1Cl2 79.92(5), Y1Cl1 Y1A 100.08(5).

complexes followed by the boratabenzene ligand redistribution provides a synthetic pathway to these complexes. Reactions of the yttrium complexes, 2 and 6, with [Rh(COD)Cl]2 in toluene gave [C5H5B(CH2)5CH3]Rh(COD) (18) and [C5H5BC(C2H5)d CH(C2H5)]Rh(COD) (19) in 83% and 84% yields, respectively (Scheme 4). Complexes 18 and 19 were characterized by NMR (1H, 13C, 11B) spectroscopy and elemental analysis. Structural Characterization of Complexes 1, 4, and 1214. Complexes 1, 4, and 717 are solid, while 2, 3, 5, 6, 18, and 19 are oils. Single crystals of 1, 4, 8, 13, and 14 were grown from toluene solutions, and those of 12 were grown from a hexane/ toluene solution. The crystals of these complexes were characterized using X-ray diffraction. Similar to [C5H5]2YCl,16 1 exists as a centrosymmetric dimer with yttrium ions Y(1) and Y(1A) linked by two bridging chloride ions (Figure 2). The boratabenzene rings [B(1),C(15)] and [B(2),C(610)] are nearly planar within 0.025 and 0.052 Å deviations, respectively, and with the B atoms deviating the most to the side opposite the metal center. The CC bond lengths of the boratabenzene rings in 1 are almost the same, and the average value (1.38 Å) is close to that in [C5H5]2YCl (1.37 Å); however, the average YC distance in the former complex is significantly longer than that in the latter, 2.71 Å versus 2.60 Å. Slippage of the Y ion away from the B atom results in long YB distances (2.84 and 2.85 Å) and a η5 coordination mode. The ansa-boratabenzene complex 4 exists as a monomer, and the O atom on the bridge coordinates to the Y ion with a distance of 2.32 Å (Figure 3). The average YC distance in 4, 2.73 Å, is close to that in 1, 2.71 Å; however, the YCl bond length in 4 is significantly shorter than that in 1, 2.54 Å versus 2.67 Å. In 12, inspection of the distance from the Zr ion to the boratabenzene rings ([B(1),C(15)] and [B(2), C(610)]) shows that the ZrB distances are significantly longer, indicating a slippage of the Zr ion away from the B atom and toward the C3(or C5) atom to give an η5 coordination mode as observed in 1 (Figure 4). The average ZrC distance is significantly longer than that in [C5H5]2ZrCl2,17 2.59 Å versus 2.43 Å. There are two independent molecules in the unit cell of 13; one is shown in Figure 5. Different from that in 1 and 12, the boratabenzene ligand is η6 coordinated. The RhC distances 4333


Organometallics

Figure 3. ORTEP drawing of 4. Thermal ellipsoids are set at 30% probability; hydrogen atoms are omitted for clarity. Selected bond distances [Å] and angles [deg]: YB1 2.842(10), YC1 2.757(11), YC2 2.690(11), YC3 2.680(8), YC4 2.713(12), YC5 2.744(10), YB2 2.811(11), YC6 2.760(9), YC7 2.712(9), YC8 2.706(10), YC9 2.725(14), YC10 2.703(12), YCl 2.545(3), YO 2.321(5), B1C11 1.64(4), B2C16 1.647(10).

Figure 4. ORTEP drawing of 12. Thermal ellipsoids are set at 30% probability; hydrogen atoms are omitted for clarity. Selected bond distances [Å] and angles [deg]: ZrB1 2.803 (13), ZrC1 2.585(12), ZrC2 2.579(10), ZrC3 2.558(11), ZrC4 2.620 (10), ZrC5 2.679 (9), ZrB2 2.757 (5), ZrC6 2.618(4), ZrC7 2.588(4), ZrC8 2.538(4), ZrC9 2.575(4), ZrC10 2.626 (4), ZrCl1 2.422(10), ZrCl2 2.424(11).

range from 2.245(5) to 2.366(5) Å, and the RhB distances are 2.287(5) and 2.344(6) Å for the two independent molecules, respectively. The PPh3 ligands coordinate to the Rh ion with distances of 2.2288(11) to 2.2572(11) Å. In 14, the boratabenzene ligand is also η6 coordinated with RhC bond lengths of 2.221(12) to 2.295(11) Å and the RhB bond lengths of 2.277(12) Å (Figure 6). The COD ligand is η2,η2 coordinated with RhC bond lengths of 2.102(6) to 2.134(5) Å. Crystal Structures of the Amidino-boratabenzene Yttrium Complex (8) and Theoretical Calculation of the Monoanionic Amidino-boratabenzene Ligand. Boratabenzenes are a type of heterocyclic, six-electron, monoanionic ligand. Amidinates are a type of heteroallylic, four-electron, monoanionic ligand.18 Both are important ancillary ligands for metal complexes, the former usually acting as π donors in η6 (or η5) coordination mode, while the latter generally adopt a bidentate, σ,σ0 -bonded fashion. A large number of metal complexes bearing either boratabenzenes or amidinates have been reported.

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Figure 5. ORTEP drawing of 13. Thermal ellipsoids are set at 30% probability; hydrogen atoms are omitted for clarity. Selected bond distances [Å] and angles [deg]: Rh1B1 2.287(5), Rh1C1 2.366(5), Rh1C2 2.345(5), Rh1C3 2.290(5), Rh1C4 2.340(5), Rh1C5 2.311(5), Rh1P1 2.229(11), Rh1P2 2.257(11).

Figure 6. ORTEP drawing of 14. Thermal ellipsoids are set at 30% probability,; hydrogen atoms are omitted for clarity. Selected bond distances [Å] and angles [deg]: RhB1 2.277(12), RhC1 2.295(11), RhC2 2.300(12), RhC3 2.278(15), RhC4 2.260(16), RhC5 2.259(13), RhC6 2.102(6), RhC7 2.134(5), RhC10 2.107(5), RhC11 2.126(6).

The hydroboration of carbodiimide with the 1-H-boratabenzene ligand combines the above two monoanionic ligands into a novel amidino-boratabenzene monoanionic ligand, which has not been reported before. In the amidino-boratabenzene yttrium complex (8) (Figure 7), the amidino-boratabenzene ligand coordinates to the metal ion through both the amidinate and boratabenzene fragments, showing a similar constrained geometry to that observed for the famous Cp-type ligands [C5R4SiMe2N(tBu)]2 (R = Me, H)19 and its boratabenzene analogue [4-(SiMe2N(tBu))C5H5BN(iPr)]2.20 However, the amidino-boratabenzene ligand is monoanionic, while [C5R4SiMe2N(tBu)]2 and [4-(SiMe2N(tBu))C5H5BN(iPr)]2 ligands are dianionic. The amidinate fragment displays a delocalized electronic frame, the C11N1 and C11N2 bond lengths (1.34 and 1.28 Å) are intermediate between those of typical single and double bonds, and the C12, N1, C11, N2, and C15 atoms are coplanar. 4334


Organometallics Interestingly, this plane is perpendicular to the boratabenzene ring with a dihedral angle of 85°, thus offering a minimum overlap

Figure 7. ORTEP drawing of 8. Thermal ellipsoids are set at 30% probability; hydrogen atoms are omitted for clarity. Selected bond distances [Å] and angles [deg]: Y1B1 2.779(9), Y1C1 2.758(9), Y1C2 2.826(8), Y1C3 2.855(8), Y1C4 2.864(8), Y1C5 2.801(8), Y1B2 2.884(9), Y1C6 2.837(9), Y1C7 2.799(10), Y1C8 2.757(9), Y1C9 2.759(9), Y1C10 2.808(9), Y1N2 2.477(6), Y1Cl1 2.665(2), Y1Cl2 2.851(2), B1N1 1.505(11), N1C11 1.341(10), N2C11 1.283(10).

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between the π orbitals of the amidinate and those of the boratabenzene. The distances from the Y ion to N2 and C11 atoms of the amidinate fragment, 2.48 and 3.40 Å, are significantly longer than those of the reported Y amidinate analogues (2.302.36 and 2.752.85 Å).21 The amidinate fragment links the boratabenzene fragment through the N1 atom with a NB bond length of 1.50 Å, which is longer than those in [C5H5BNEt2]2YCl (1.39 and 1.41 Å).10d The bonding mode of the boratabenzene fragment is interesting; the B atom is closer to the Y ion than to the C3 atom, 2.78 Å versus 2.85 Å, and the boratabenzene ring can be best described as η6 coordination. This observation is different from most of the reported boratabenzene early transition metal complexes, where the metal ions slip away from the B atoms and the metalB bond lengths are longer than the metalC(ring) bond lengths.7c Actually, this kind of bonding mode is close to that of the neutral borabenzenemetal interaction we previously reported,10c which shows a short YbB distance. Furthermore, the average YC(15) distance (2.82 Å) in 8 is longer than that in [C5H5BNEt2]2YCl (2.69 Å).10d On the other hand, the [C5H5BH] ligand displays a normal η5 coordination mode like that in 1, and the YB2 separation is long (2.88 Å). To obtain a better understanding of the nature of the monoanionic amidino-boratabenzene ligand [C5H5BN(iPr)CHN(iPr)] (C) in 8, density functional theory (DFT) studies were carried

Figure 8. Optimized neutral borabenzene A (R = NHMe2), monoanionic boratabenzene B (R = NMe2), monoanionic amidino-boratabenzene C (R = N(iPr)CHN(iPr)), and complex 8. The NBO charges on the R groups (CR) and the borabenzene or boratabenzene fragments (CB) and selected bond lengths [Å] (bold) with bond orders (italic) are shown. Calculated at the B3LYP/6-311++G**/SDD level. 4335


Organometallics out and compared to the neutral borabenzene analogue C5H5BrNHMe2 (A) and the monoanionic boratabenzene [C5H5B-NMe2] (B) (Figure 8). DFT22 studies were performed with the Gaussian03 program23 using the B3LYP24 method, and the 6-311++G** basis set was used for C, H, N, Cl, and B and the SDD basis set with effective core potential25 was used for Y. The atomic charges and Wiberg bond order were calculated by NBO natural bonding analysis.26 The structure of 8 obtained by X-ray diffraction was used as the initial structure to do the optimization. The results show that the amidinate fragment carries a more negative charge than the boratabenzene fragment in C, 0.555 versus 0.445. The charge on the boratabenzene fragment falls in between those of the neutral boratabenzene ligand A (0.351) and the monoanionic boratabenzene B (0.558). Furthermore, the BN bond length and bond order of C (1.549 Å, 0.68) also are intermediate between those of A (1.603 Å, 0.59) and B (1.487 Å, 0.84). These calculations are consistent with the structural features observed in the solid-state structure of 8, which indicates that the boratabenzene fragment of the amidino-boratabenzene shows some neutral borabenzene character, and to some degree, it can be described as a hybrid between anionic boratabenzene and neutral borabenzene. The negative charges on the amidinate and the boratabenzene fragments in 8 decreased by 0.217 and 0.304, respectively. Whereas the charge donation from the boratabenzene fragment of C to the metal center is less than that of the [C5H5BH] ligand (0.379), the total charge donation of the whole amidinoboratabenzene ligand (0.521) is much larger than that of the [C5H5BH] ligand. The orbital analysis of 8 shows that the πb1 and πa2 orbitals of the boratabenzene fragment overlap with the dzx and dxy orbitals of the metal and that the σ orbital on N2 of the amidinate fragment overlaps with the dz2 orbital of the metal (see Supporting Information Figure S-1). In summary, the hydroboration of a range of unsaturated substrates with metal-bound 1-H-boratabenzene has been used to access a series of new boratabenzene metal complexes. This hydroboration reaction is unusual since the 1-H-boratabenzene ligand is an aromatic anion. It is fascinating that it works well for unactivated simple alkenes in the case of 1-H-boratabenzene rare-earth metal complexes. In contrast to most reported examples showing the influence of the ancillary ligands on the reactivity of the metal ion, the difference in the reactivity of the 1-H-boratabenzene metal complexes observed herein demonstrates the effect of the metal ion on the reactivity of their ancillary ligands. This finding provides a new strategy to synthesize a variety of boratabenzene metal complexes and ultimately initiates other studies aiming at the transformation of boroncontaining metal complexes via the hydroboration pathway. The 1-H-boratabenzene late transition metal complex exhibits low hydroboration reactivity. However the highly efficient hydroboration with 1-H-boratabenzene rare-earth metal complexes followed by the boratabenzene ligand redistribution provides an operational synthetic pathway to the target late-metal complexes.

’ EXPERIMENTAL SECTION General Methods. All operations were carried out under an atmosphere of argon using Schlenk techniques or in a nitrogen-filled glovebox. Ethyl ether was distilled from Na-benzophenone ketyl. Toluene, hexane, C6D6, and THF-d8 were dried over Na/K alloy, distilled under vacuum, and stored in the glovebox. CDCl3 was degassed and dried over 4 Å molecular sieves. [C5H5BH]Li27 was prepared by a

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method similar to that reported by Fu, but using the reactant C5H5BNEt328 instead of C5H5BPMe3; the advantage of this modification was to avoid the use of the expensive and malodorous PMe3. 1-Hexene, allyl propyl ether, allyl ether, and 3-hexyne were dried over CaH2 and distilled under vacuum. N,N0 -Diisopropylcarbodiimide was purchased from Aldrich and dried over 4 Å molecular sieves. Benzylidene-n-propylamine was prepared according to the literature29 and dried over 4 Å molecular sieves. 1H NMR and 13C NMR spectra were recorded on a Varian Mercury 300 or 400 MHz spectrometer at 300 or 400 MHz and 75 or 100 MHz, respectively. 31P NMR spectra were recorded on a Varian 400 MHz spectrometer at 162 MHz. 11B NMR and 89 Y NMR spectra were recorded on a Bruker DXP 400 MHz spectrometer at 128 and 19.6 MHz, respectively. All chemical shifts were reported in δ units with reference to the residual solvent resonance of the deuterated solvents for proton and carbon chemical shifts, to external BF3 3 OEt2 for boron chemical shifts, and to 3.0 M YCl3 in D2O for yttrium chemical shifts. Elemental analysis was performed by Analytical Laboratory of Shanghai Institute of Organic Chemistry. [C5H5BH]2YCl (1). [C5H5BH]Li (281 mg, 3.35 mmol) and YCl3 (323 mg, 1.65 mmol) were mixed in 60 mL of toluene, and the reaction mixture was stirred for 3 days at 110 °C. The precipitate was removed by centrifugation and the clear, pale yellow solution was concentrated to give 1 as a pale yellow crystalline solid (327 mg, 71% yield). Single crystals suitable for X-ray diffraction analysis were obtained from a toluene solution. 1H NMR (300 MHz, C6D6, 25 °C): δ 7.37 (dd, JHH = 9.3 Hz, JHH = 7.5 Hz, 4H, 3-/5-H), 7.10 (ddd, JHH = 9.9 Hz, JHH(B) = 4.5 Hz, JHH = 1.5 Hz, 4H, 2-/6-H), 6.78 (tt, JHH = 7.2 Hz, JHH = 1.5 Hz, 2H, 4-H), 5.506.60 (bs, 2H, BH). 13C NMR (75 MHz, CDCl3, 25 °C): δ 141.3, 134.0, 116.2. 11B NMR (128 MHz, CDCl3, 25 °C): δ 37.3. 89Y NMR spectrum of 1 was not obtained due to the low solubility of the complex. Anal. Calcd (%) for C10H12B2ClY: C, 43.18; H, 4.35. Found: C, 43.11; H, 4.67. [C5H5B(CH2)5CH3]2YCl (2). A toluene solution of 1-hexene (453 mg, 5.38 mmol in 2 mL of toluene) was added to 1 (150 mg, 0.539 mmol) in 4 mL of toluene. After stirring for 4 days at 75 °C, the reaction mixture was filtered. Evaporation of the orange filtrate in vacuo left an orange oil, which was extracted with 3 2 mL of hexane. Removal of the solvent of the extract gave 2 as an orange oil (215 mg, 89% yield). 1 H NMR (400 MHz, C6D6, 25 °C): δ 7.44 (dd, JHH = 10.4 Hz, JHH = 7.2 Hz, 4H, 3-/5-H), 7.00 (d, JHH = 9.6 Hz, 4H, 2-/6-H), 6.20 (t, JHH = 7.2 Hz, 2H, 4-H), 1.801.72 (m, 4H, B(CH2)5CH3), 1.601.53 (m, 8H, B(CH2)5CH3), 1.501.37 (m, 8H, B(CH2)5CH3), 0.97 (t, JHH = 7.2 Hz, 6H, B(CH2)5CH3). 13C NMR (100 MHz, C6D6, 25 °C): δ 141.8, 133.4, 112.2, 33.3, 32.5, 28.0, 23.2, 22.5, 14.5. 11B NMR (128 MHz, C6D6, 25 °C): δ 46.9. 89Y NMR (19.6 MHz, C6D6, 25 °C): δ 21.4. Anal. Calcd (%) for C22H36B2ClY: C, 59.18; H, 8.13. Found: C, 57.99; H, 8.61. [C5H5B(CH2)3O(CH2)2CH3]2YCl (3). A toluene solution of allyl propyl ether (81.3 mg, 0.812 mmol in 2 mL of toluene) was added to 1 (103 mg, 0.370 mmol) in 3 mL of toluene. After stirring for 18 h at 75 °C, the reaction mixture was filtered. Evaporation of the yellow filtrate in vacuo left a yellow oil, which was washed with 4 0.5 mL of cold hexane and dried in vacuo to give 3 as a yellow oil (138 mg, 78% yield). 1H NMR (400 MHz, C6D6, 25 °C): δ 7.47 (bs, 4H, 3-/5-H), 6.70 (bd, JHH = 9.6 Hz, 4H, 2-/6-H), 6.30 (t, JHH = 7.2 Hz, 2H, 4-H), 3.34 (bs, 4H, OCH2CH2CH3), 3.30 (t, JHH = 5.8 Hz, 4H, BCH2CH2CH2O), 1.81 (bs, 4H, BCH2CH2CH2O), 1.501.40 (m, 8H, BCH2CH2CH2O and OCH2CH2CH3), 0.76 (t, JHH = 7.2 Hz, 6H, OCH2CH2CH3). 13C NMR (100 MHz, C6D6, 25 °C): δ 140.2 (bs), 130.2 (bs), 111.7, 75.3, 74.4, 27.7, 22.2, 18.6, 10.2. 11B NMR (128 MHz, C6D6, 25 °C): δ 41.8. 89 Y NMR (19.6 MHz, C6D6, 25 °C): δ 18.2. Anal. Calcd (%) for C22H36B2ClO2Y: C, 55.22; H, 7.58. Found: C, 54.84; H, 8.16. [C5H5B(CH2)3O(CH2)3BC5H5]YCl (4). A toluene solution of allyl ether (44 mg, 0.448 mmol in 1 mL of toluene) was added to 1 (140 mg, 4336


Organometallics 0.503 mmol) in 4.5 mL of toluene. After stirring for 3 days at room temperature, the reaction mixture was filtered. Evaporation of the yellow filtrate in vacuo left an orange oil, which was dissolved in 4 mL of toluene. The toluene solution was stirred for 4 days at 75 °C and then filtered. The volatiles of the yellow filtrate were removed in vacuo to give a yellow residue. The residue was washed with 3 1.5 mL of hexane and dried in vacuo to afford 4 as a yellow solid (140 mg, 79% yield). Single crystals suitable for X-ray diffraction analysis were obtained from a toluene solution. 1H NMR (400 MHz, C6D6, 25 °C): δ 7.81 (t, JHH = 8.4 Hz, 2H, 3-/5-H), 7.25 (t, JHH = 8.4 Hz, 2H, 3-/5-H), 6.93 (d, JHH = 10.8 Hz, 2H, 2-/6-H), 6.39 (d, JHH = 10.0 Hz, 2H, 2-/6-H), 6.24 (t, JHH = 7.0 Hz, 2H, 4-H), 3.563.50 (m, 2H, BCH2CH2CHH0 O), 3.01 (dt, JHH = 12.4 Hz, JHH = 4.0 Hz, 2H, BCH2CH2CHH0 O), 1.521.45 (m, 4H, BCH2CH2CH2O), 1.431.36 (m, 2H, BCHH0 CH2CH2O), 1.231.16 (m, 2H, BCHH0 CH2CH2O). 13C NMR (100 MHz, C6D6, 25 °C): δ 144.1, 139.5, 133.3, 129.9, 110.5, 74.9, 24.5, 17.0. 11 B NMR (128 MHz, C6D6, 25 °C): δ 40.1. 89Y NMR spectrum of 4 was not obtained due to the low solubility of the complex. Anal. Calcd (%) for C16H22B2ClOY: C, 51.07; H, 5.89. Found: C, 52.14; H, 6.00. [C5H5B(CH2)3OCH2CHdCH2]2YCl (5). A toluene solution of allyl ether (256 mg, 2.61 mmol in 1 mL of toluene) was added to 1 (73 mg, 0.262 mmol) in 2 mL of toluene. After stirring for 37 h at room temperature, the reaction mixture was filtered. Evaporation of the filtrate in vacuo left an orange oil, which was washed with 4 0.5 mL of cold hexane and dried in vacuo to gave 5 as an orange oil (95 mg, 77% yield). 1 H NMR (400 MHz, C6D6, 25 °C): δ 7.48 (bs, 4H, 3-/5-H), 6.72 (bd, JHH = 10.0 Hz, 4H, 2-/6-H), 6.29 (tt, JHH = 7.2 Hz, JHH = 1.6 Hz, 2H, 4-H), 5.825.72 (m, 2H, OCH2CHCH2), 5.11 (dd, 2H, JHH = 17.2 Hz, JHH = 1.6 Hz, OCH2CHCHH0 ), 5.01 (d, 2H, JHH = 10.4 Hz, OCH2CHCHH0 ), 3.93 (bs, 4H, OCH2CHCH2), 3.32(t, 4H, JHH = 5.6 Hz, BCH2CH2CH2O), 1.81 (bs, 4H, BCH2CH2CH2O), 1.44 (t, JHH = 7.6 Hz, 4H, BCH2CH2CH2O). 13C NMR (100 MHz, C6D6, 25 °C): δ 141.6, 133.5, 130.6, 118.9, 111.8, 74.6, 73.8, 27.6, 18.6. 11B NMR (128 MHz, C6D6, 25 °C): δ 41.8. 89Y NMR (19.6 MHz, C6D6, 25 °C): δ 15.9. 1H NMR spectrum indicates the product is about 95% pure. [C5H5BC(C2H5)dCH(C2H5)]2YCl (6). A toluene solution of 3-hexyne (65 mg, 0.791 mmol in 1 mL of toluene) was added to 1 (100 mg, 0.359 mmol) in 3 mL of toluene. After stirring for 5 days at room temperature, the reaction mixture was filtered. Evaporation of the filtrate in vacuo left a yellow oil, which was extracted with 3 1.5 mL of hexane. Removal of the solvent of the extract gave 6 as a yellow oil (114 mg, 72% yield). 1H NMR (400 MHz, C6D6, 25 °C): δ 7.51 (dd, JHH = 10.4 Hz, JHH = 7.2 Hz, 4H, 3-/5-H), 7.17 (d, JHH = 9.6 Hz, 4H, 2-/ 6-H), 6.44 (t, JHH = 7.2 Hz, 2H, BC(C2H5)CH(C2H5)), 6.32 (tt, JHH = 6.8 Hz, JHH = 1.6 Hz, 2H, 4-H), 2.66 (q, JHH = 7.5 Hz, 4H, BC(CH2CH3)CH(C2H5)), 2.36 (m, JHH = 7.4 Hz, 4H, BC(C2H5)CH(CH2CH3)), 1.24 (t, JHH = 7.4 Hz, 6H, BC(CH2CH3)CH(C2H5)), 1.17 (t, JHH = 7.6 Hz, 6H, BC(C2H5)CH(CH2CH3)). 13C NMR (100 MHz, C6D6, 25 °C): δ 145.6, 141.8, 140.7, 130.7, 112.5, 23.4, 22.3, 15.5, 14.8. 11B NMR (128 MHz, C6D6, 25 °C): δ 39.3. 89 Y NMR (19.6 MHz, C6D6, 25 °C): δ 24.6. Anal. Calcd (%) for C22H32B2ClY: C, 59.72; H 7.29. Found: C, 59.44; H, 7.50. [C5H5BN(nPr)CH2Ph]2YCl (7). A toluene solution of benzylidenen-propylamine (107 mg, 0.727 mmol in 2 mL of toluene) was added to 1 (101 mg, 0.363 mmol) in 2 mL of toluene. After stirring for 2 days at 75 °C, the reaction mixture was filtered. Evaporation of the filtrate in vacuo gave 7 as an orange solid (195 mg, 94% yield). Some 1H and 13C NMR signals of the complex are broad at 25 °C and become sharp at 75 °C. 1H NMR (400 MHz, C6D6, 25 °C): δ 7.48 (bs, 2H, 3-/5-H), 7.33 (bs, 6H, 3-/5-H and o-H(Ph)), 7.22 (t, JHH = 6.8 Hz, 4H, m-H(Ph)), 7.10 (t, JHH = 6.8 Hz, 2H, p-H(Ph)), 6.405.80 (m, 6H, 2-/6-H and 4-H), 4.63 (m, 2H, CHH0 Ph), 4.22 (bs, 2H, CHH0 Ph), 3.34 (bs, 2H, NCHH0 CH2CH3), 3.07 (bs, 2H, NCHH0 CH2CH3), 1.60 (bs, 2H, NCH2CHH0 CH3), 1.50 (bs, 2H, NCH2CHH0 CH3), 0.83 (bs,

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6H, CH3). 1H NMR (400 MHz, C6D6, 75 °C): δ 7.41 (bs, 4H, 3-/ 5-H), 7.35 (d, JHH = 7.2 Hz, 4H, o-H(Ph)), 7.22 (t, JHH = 6.8 Hz, 4H, m-H(Ph)), 7.10 (t, JHH = 7.2 Hz, 2H, p-H(Ph)), 6.22 (bd, JHH = 8.8 Hz, 4H, 2-/6-H), 5.96 (t, JHH = 6.8 Hz, 2H, 4-H) 4.47 (bs, 4H, CH2Ph), 3.24 (bs, 4H, NCH2CH2CH3), 1.59 (q, JHH = 7.2 Hz, 4H, NCH2CH2CH3), 0.87 (t, JHH = 7.6 Hz, 6H, CH3). 13C NMR (100 MHz, C6D6, 25 °C): δ (ppm) 143.2(m), 142.3(m), 128.6, 127.6, 126.8, 116.8(m), 102.0, 53.0, 51.9(m), 23.3, 11.9. 13C NMR (100 MHz, C6D6, 75 °C): δ 143.1, 142.3, 128.5, 127.8, 126.8, 117.5, 102.4, 53.4, 51.9, 23.4, 11.8. 11B NMR (128 MHz, C6D6, 25 °C): δ 35.1. 11B NMR (128 MHz, C6D6, 75 °C): δ 33.6. 89Y NMR (19.6 MHz, C6D6, 25 °C): δ 4.1. Anal. Calcd (%) for C30H38B2ClN2Y: C, 62.93; H, 6.69; N, 4.89. Found: C, 62.60; H, 6.87; N, 4.67. [C5H5BN(iPr)CHN(iPr)][C5H5BH]YCl (8). A toluene solution of N,N0 -diisopropylcarbodiimide (27 mg, 0.214 mmol in 1 mL of toluene) was added to 1 (59 mg, 0.212 mmol) in 2 mL of toluene. After stirring for 2 days at room temperature, the reaction mixture was filtered. Evaporation of the yellow filtrate in vacuo left a yellow oil, to which 3 mL of hexane was added to give 8 as a pale yellow solid. Concentration of the mother liquor afforded a second crop of 8; thus 78 mg of 8 was obtained in total (90% yield). Single crystals suitable for X-ray diffraction analysis were obtained from a toluene solution. 1H NMR (400 MHz, C6D6, 25 °C): δ 7.64 (ddd, JHH = 10.4 Hz, JHH = 7.2 Hz, JHH = 1.6 Hz, 1H, 3-/5-H(NBring)), 7.57 (m, 2H, 3-/5-H(HBring)), 7.52 (m, 1H, 3-/ 5-H(NBring)), 7.20 (d, JYH = 3.2 Hz, 1H, NCHN), 7.187.14 (m, 1H, 2-/6-H(HBring)), 7.137.08 (m, 1H, 2-/6-H(HBring)), 6.68 (ddd, JHH = 10.4 Hz, JHH = 2.8 Hz, JHH = 1.2 Hz, 1H, 2-/6-H(NBring)), 6.67 (tt, JHH = 7.0 Hz, JHH = 1.6 Hz, 1H, 4-H(HBring)), 6.37 (tt, JHH = 7.0 Hz, JHH = 1.6 Hz, 1H, 4-H(NBring)), 6.35 (ddd, JHH = 10.0 Hz, JHH = 2.8 Hz, JHH = 1.2 Hz, 1H, 2-/6-H(NBring)), 5.206.20 (bs, 1H, BH), 3.68 (sept, JHH = 6.8 Hz, 1H, BNCH(CH3)2), 3.04 (sept, JHH = 6.8 Hz, 1H, CHNCH(CH3)2), 1.04 (d, JHH = 6.8 Hz, 3H, BNCH(CH3)2), 1.00 (d, JHH = 6.8 Hz, 3H, BNCH(CH3)2), 0.88 (d, JHH = 6.8 Hz, 3H, CHNCH(CH3)2), 0.86 (d, JHH = 6.4 Hz, 3H, CHNCH(CH3)2). 13C NMR (100 MHz, C6D6, 25 °C): δ 164.4, 142.4, 140.9, 139.5, 138.8, 133.4(bs), 132.7(bs), 131.4(bs), 127.2(bs), 115.6, 112.8, 52.1, 51.1, 24.5, 24.2, 23.9, 22.0. 11 B NMR (128 MHz, C6D6, 25 °C): δ 36.9, 34.0. 89Y NMR (19.6 MHz, C6D6, 25 °C): δ 12.3. Anal. Calcd (%) for C17H26B2ClN2Y: C, 50.49; H, 6.48; N, 6.93. Found: C, 50.28; H, 6.48; N, 7.03. [C5H5BH]2LuCl (9). Following the procedure described for 1. Reaction of anhydrous LuCl3 (168 mg, 0.596 mmol) and [C5H5BH]Li (100 mg, 1.19 mmol) in 30 mL of toluene gave 9 as a pale yellow, crystalline solid (190 mg, 87% yield). 1H NMR (400 MHz, C6D6, 25 °C): δ 7.34 (dd, JHH = 9.2 Hz, JHH = 7.6 Hz, 4H, 3-/5-H), 6.98 (ddd, JHH = 10.4 Hz, JHH(B) = 4.8 Hz, JHH = 1.6 Hz, 4H, 2-/6-H), 6.87 (tt, JHH = 7.2 Hz, JHH = 1.6 Hz, 2H, 4-H). 13C NMR (75 MHz, CDCl3, 25 °C): δ 141.4, 131.8, 115.0. 11B NMR (128 MHz, CDCl3, 25 °C): δ 37.1. Anal. Calcd (%) for C10H12B2ClLu: C, 32.97; H, 3.32. Found: C, 33.46; H, 3.90. [C5H5B(CH2)5CH3]2LuCl (10). Following the procedure described for 2. Reaction of 9 (80 mg, 0.220 mmol) and 1-hexene (370 mg, 4.40 mmol) in 4 mL of toluene for 8 days at 75 °C gave 7 as an orange oil (110 mg, 94% yield). 1H NMR (400 MHz, C6D6, 25 °C): δ 7.46 (dd, JHH = 10.0 Hz, JHH = 7.2 Hz, 4H, 3-/5-H), 7.01 (d, JHH = 9.6 Hz, 4H, 2-/6-H), 6.19 (t, JHH = 7.2 Hz, 2H, 4-H), 1.851.79 (m, 4H, B(CH2)5CH3), 1.661.58 (m, 8H, B(CH2)5CH3), 1.541.40 (m, 8H, B(CH2)5CH3), 0.98 (t, JHH = 7.2 Hz, 6H, B(CH2)5CH3). 13C NMR (75 MHz, C6D6, 25 °C): δ 142.2, 132.1, 110.5, 33.3, 32.5, 28.0, 23.3, 22.6, 14.5. 11B NMR (128 MHz, C6D6, 25 °C): δ 45.3. Anal. Calcd (%) for C22H36B2ClLu: C, 49.62; H, 6.81. Found: C, 48.99; H, 7.04. [C5H5BN(iPr)CHN(iPr)][C5H5BH]LuCl (11). Following the procedure described for 8, reaction of 9 (117 mg, 0.321 mmol) and N,N0 diisopropylcarbodiimide (41 mg, 0.325 mmol) in 4 mL of toluene for 4337


Organometallics 4 days at room temperature gave 11 as a pale yellow solid (137 mg, 87% yield). 1H NMR (400 MHz, C6D6, 25 °C): δ 7.65 (ddd, JHH = 10.4 Hz, JHH = 7.2 Hz, JHH = 1.6 Hz, 1H, 3-/5-H(NBring)), 7.60 (ddd, JHH = 10.4 Hz, JHH = 7.2 Hz, JHH = 1.6 Hz, 1H, 3-/5-H(NBring)), 7.52 (m, 2H, 3-/5-H(HBring)), 7.26 (s, 1H, NCHN), 7.117.08 (m, 1H, 2-/ 6-H(HBring)), 7.047.01 (m, 1H, 2-/6-H(HBring)), 6.63 (ddd, JHH = 10.4 Hz, JHH = 2.8 Hz, JHH = 1.2 Hz, 1H, 2-/6-H(NBring)), 6.61 (tt, JHH = 7.2 Hz, JHH = 1.6 Hz, 1H, 4-H(HBring)), 6.38 (tt, JHH = 7.2 Hz, JHH = 1.6 Hz, 1H, 4-H(NBring)), 6.33 (ddd, JHH = 10.4 Hz, JHH = 2.8 Hz, JHH = 1.2 Hz, 1H, 2-/6-H(NBring)), 3.73 (sept, JHH = 6.8 Hz, 1H, CH(CH3)2), 3.02 (sept, JHH = 6.8 Hz, 1H, CH(CH3)2), 1.04 (d, JHH = 6.8 Hz, 3H, CH(CH3)2), 1.00 (d, JHH = 6.8 Hz, 3H, CH(CH3)2), 0.88 (d, JHH = 6.8 Hz, 3H, CH(CH3)2), 0.85 (d, JHH = 6.4 Hz, 3H, CH(CH3)2). 13C NMR (100 MHz, C6D6, 25 °C): δ 164.7, 142.6, 141.7, 139.5, 139.1, 131.4(bs), 126.2(bs), 114.5, 111.9, 52.1, 51.4, 24.4, 24.2, 23.8, 21.8. 11B NMR (128 MHz, C6D6, 25 °C): δ 36.2, 33.6. Anal. Calcd (%) for C17H26B2ClLuN2: C, 41.63; H, 5.34; N, 5.71. Found: C, 41.56; H, 5.36; N, 5.63. [C5H5BH]2ZrCl2 (12). A 20 mL amount of ether was added into a mixture of [C5H5BH]Li (100 mg, 1.19 mmol) and ZrCl4 (139 mg, 0.596 mmol) at 70 °C. After stirring for 3 h at 70 °C, the reaction mixture was gradually warmed to room temperature. Evaporation of the brown filtrate in vacuo left a brown solid, which was extracted with 7 3 mL of hexane/toluene (v/v = 4:1). Removal of the solvent of the extract gave 1 as a yellow solid (175 mg, 93% yield). 1H NMR (400 MHz, C6D6, 25 °C): δ 7.30 (t, JHH = 8.4 Hz, 4H, 3-/5-H), 6.416.36 (m, 6H, 2-/6-H and 4-H). 13C NMR (100 MHz, C6D6, 25 °C): δ 147.7, 129.3 (bs), 115.9. 11B NMR (128 MHz, C6D6, 25 °C): δ 37.5. Anal. Calcd (%) for C10H12B2Cl2Zr: C, 38.01; H, 3.83. Found: C, 37.81; H, 4.28. [C5H5BH]Rh(PPh3)2 (13). Rh(PPh3)3Cl (266 mg, 0.287 mmol) and [C5H5BH]2YCl (1) (40 mg, 0.144 mmol) were mixed in 15 mL of toluene. After the reaction mixture was stirred at room temperature for 12 h, the dark red mixture was filtered, and the residue was extracted with 3 mL of toluene. The combined solution was concentrated to approximately 1 mL and cooled to 35 °C to give 13 as a red, crystalline solid. Concentration of the mother liquor afforded a second crop of 13. A total of 164 mg of 13 was obtained (81% yield). 1H NMR (400 MHz, C6D6, 25 °C): δ 7.65 (m, 12H, m-H(Ph)), 7.13 (m, toluene), 7.02 (m, toluene), 6.91 (m, 18H, o-H(Ph) and p-H(Ph)), 6.13 (dd, JHH = 8.6 Hz, JHH = 6.0 Hz, 2H, 3-/5-H), 5.89 (dd, JHH = 8.6 Hz, JHH(B) = 3.2 Hz, 2H, 2-/6-H), 4.20 (bs, 1H, B-H), 4.08 (t, JHH = 6.0 Hz, 1H, 4-H), 2.11 (s, toluene). 13C NMR (100 MHz, C6D6, 25 °C): δ 139.2 (d, JPC(Ph) = 21.2 Hz), 138.9 (d, JPC(Ph) = 21.0 Hz), 137.9 (s, toluene), 134.7 (d, JPC(Ph) = 6.2 Hz), 134.6 (d, JPC(Ph) = 6.1 Hz), 129.3 (toluene), 128.8 (s, C(Ph)), 128.6 (toluene), 127.4 (d, JPC(Ph) = 5.0 Hz), 127.3 (d, JPC(Ph) = 5.0 Hz), 125.7 (toluene), 111.1 (s), 108.5 (d, JRhC = 2.3 Hz), 86.9 (d, JRhC = 3.7 Hz), 21.5 (CH3-toluene). 31P NMR (162 MHz, C6D6, 25 °C): δ 51(d, JPRh = 213 Hz). 11B NMR (128 MHz, C6D6, 25 °C): δ 14.9. Anal. Calcd (%) for C41H36BP2Rh 3 0.5 toluene: C, 71.22; H, 5.37. Found: C, 70.80; H, 5.58. [C5H5BH]Rh(COD) (14). [Rh(COD)Cl]2 (89 mg, 0.180 mmol) and [C5H5BH]2YCl (1) (52 mg, 0.187 mmol) were mixed in 10 mL of toluene. After the reaction mixture was stirred at room temperature for 12 h, the red mixture was filtered, and the residue was extracted with 3 mL of toluene. Removal of the solvent in vacuo gave 14 as an orange, crystalline solid (89 mg, 83% yield). 1H NMR (400 MHz, C6D6, 25 °C): δ 5.96 (m, 4H, 2-/6-H, and 3-/5-H), 4.52 (m, 1H, 4-H), 4.15 (m, 4H, CH2CHCHCH2), 1.97 (m, 4H, CH2CHCHCH2), 1.77 (m, 4H, CH2CHCHCH2). 13C NMR (100 MHz, C6D6, 25 °C): δ 109.1 (d, JRhC = 2.7 Hz), 108.2 (bs), 87.9 (d, JRhC = 3.5 Hz), 67.8 (d, JRhC = 12.8 Hz, CH2CHCHCH2), 32.2 (s, CH2CHCHCH2). 11B NMR (128 MHz, C6D6, 25 °C): δ 17.2. Anal. Calcd (%) for C13H18BRh: C, 54.22; H, 6.30. Found: C, 54.13; H, 6.14.

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[C5H5BN(nPr)CH2Ph]Li (15). A toluene solution of benzylidene-npropylamine (79 mg, 0.537 mmol in 5 mL of toluene) was added to [C5H5BH]Li (45 mg, 0.537 mmol) in 1 mL of THF. After stirring for 8 days at 75 °C, the reaction mixture was filtered. Evaporation of the filtrate in vacuo gave a pale yellow oil, which was washed with 4 3 mL of hexane and dried in vacuo to give a mixture of 15 (∼85%) and [C5H5BH]Li (∼15%) (86 mg). [C5H5BH]Li could not be completely consumed even with a long reaction time and an excess of benzylidene-npropylamine. Attempts to separate 15 from [C5H5BH]Li failed due to their similar solubility. 1H NMR (400 MHz, THF-d8, 25 °C): δ 7.29 (d, JHH = 7.6 Hz, 2H, o-H(Ph)), 7.15 (t, JHH = 7.4 Hz, 2H, 3-/5-H), 7.02 (m, 3H, m-H(Ph) and p-H(Ph)), 5.65 (d, JHH = 9.6 Hz, 2H, 2-/ 6-H), 5.47 (t, JHH = 6.6 Hz, 1H, 4-H), 4.27 (s, 2H, CH2Ph), 2.97 (t, JHH = 7.4 Hz, 2H, NCH2CH2CH3), 1.46 (sext, JHH = 7.6 Hz, 2H, NCH2CH2CH3), 0.81 (t, JHH = 7.2 Hz, 3H, NCH2CH2CH3). 13C NMR (100 MHz, THF-d8, 25 °C): δ 145.9, 134.6, 128.4, 128.2, 126.0, 110.7 (br), 99.7, 53.9, 52.3, 23.4, 12.2. 11B NMR (128 MHz, THF-d8, 25 °C): δ 31.7. [C5H5BN(nPr)CH2Ph]2ZrCl2 (16). Following the procedure described for 7, reaction of 12 (62 mg, 0.196 mmol) and benzylidene-npropylamine (58 mg, 0.394 mmol) in 2 mL of toluene for 2 days at 75 °C gave 16 as an orange solid (108 mg, 90% yield). 1H NMR (400 MHz, C6D6, 25 °C): δ 7.247.16 (m, 8H, 3-/5-H and o-H(Ph)), 7.08 (t, JHH = 6.4 Hz, 4H, m-H(Ph)), 7.10 (td, JHH = 6.4 Hz, JHH = 2 Hz, 2H, p-H(Ph)), 5.87 (t, JHH = 6.4 Hz, 2H, 4-H), 5.76 (dd, JHH = 11.6 Hz, JHH = 3.2 Hz, 1H, 2-/6-H), 5.65 (dd, JHH = 12 Hz, JHH = 2.4 Hz, 1H, 2-/6-H), 5.50 (dd, JHH = 11.2 Hz, JHH = 3.2 Hz, 1H, 2-/6-H), 5.39 (dd, JHH = 12 Hz, JHH = 2.8 Hz, 1H, 2-/6-H), 4.46 (d, JHH = 16.8 Hz, 2H, CHH0 Ph), 4.44 (d, JHH = 16 Hz, 2H, CHH0 Ph), 4.02 (d, JHH = 15.6 Hz, 2H, CHH0 Ph), 3.98 (d, JHH = 15.2 Hz, 2H, CHH0 Ph), 3.09 (m, 2H, NCH2CH2CH3), 2.91 (m, 2H, NCH2CH2CH3), 1.42 (m, 4H, NCH2CH2CH3), 0.73 (t, JHH = 6.8 Hz, 6H, CH3), 0.71 (t, JHH = 6.4 Hz, 6H, CH3). 13C NMR (75 MHz, C6D6, 25 °C): δ 145.7, 144.4, 141.2, 128.6, 127.0, 101.3, 101.2, 52.4, 51.1, 51.0, 23.1, 23.0, 11.7. 11B NMR (128 MHz, C6D6, 25 °C): δ 32.7. Anal. Calcd (%) for C30H38B2Cl2N2Zr: C, 59.03; H, 6.27; N, 4.59. Found: C, 59.36; H, 6.53; N, 4.44. [C5H5BN(iPr)CHN(iPr)]Rh(PPh3)2 (17). [C5H5BH]Rh(PPh3)2 (13) (51 mg, 0.0720 mmol) and N,N0 -diisopropylcarbodiimide (94 mg, 0.740 mmol) were mixed in 2 mL of toluene. After stirring for 15 days at 75 °C, the reaction mixture was filtered. Evaporation of the filtrate in vacuo gave a red oil, to which hexane was added and evaporated to afford 17 as a red solid (57 mg, 92% yield). 1H NMR (400 MHz, C6D6, 25 °C): δ 7.87 (s, 1H, NCHN), 7.63 (m, 10H, m-H(Ph)), 7.42 (m, 2H, m-H(Ph)), 7.04 (m, 3H, o-H(Ph) and p-H(Ph)), 6.93 (m, 15H, o-H(Ph) and p -H(Ph)), 5.81 (dd, JHH = 9.3 Hz, JHH = 6.0 Hz, 2H, 3-/ 5-H), 4.85 (d, JHH = 6.0 Hz, 2H, 2-/6-H), 4.32 (t, JHH = 6.0 Hz, 1H, 4-H), 4.27 (sept, JHH = 6.9 Hz, 1H, CH(CH3)2), 3.18 (sept, JHH = 6.3 Hz, 1H, CH(CH3)2), 1.54 (d, JHH = 6.9 Hz, 6H,CH(CH3)2), 1.31 (d, JHH = 6.3 Hz, 6H,CH(CH3)2), 1.24 (m, hexane), 0.89 (t, hexane). 13C NMR (100 MHz, C6D6, 25 °C): δ 151.9 (s, NCHN), 138.6 (d, JPC(Ph) = 20.6 Hz), 138.4 (d, JPC(Ph) = 20.9 Hz), 134.7 (d, JPC(Ph) = 6.4 Hz), 134.6 (d, JPC(Ph) = 5.5 Hz), 128.9 (s, C(Ph)), 127.4 (d, JPC(Ph) = 5.0 Hz), 127.3 (d, JPC(Ph) = 4.1 Hz), 108.7 (d, JRhC = 3.8 Hz), 92.8 (s), 83.1 (d, JRhC = 2.7 Hz), 58.0 (s, CHMe2), 47.6 (s, CHMe2), 32.0 (s, hexane), 26.4 (s, CH(CH3)2), 23.1 (s, hexane), 20.9 (s, CH(CH3)2), 14.4 (s, hexane). 31P NMR (162 MHz, C6D6, 25 °C): δ 51.8 (d, JPRh = 212.5 Hz). 11B NMR (128 MHz, C6D6, 25 °C): δ 25.2. Anal. Calcd (%) for C48H50BN2P2Rh 3 0.25 hexane: C, 69.77; H, 6.33; N, 3.29. Found: C, 69.73; H, 6.23; N, 3.26. [C5H5B(CH2)5CH3]Rh(COD) (18). Following the procedure described for 14, reaction of 2 (56 mg, 0.125 mmol) and [Rh(COD)Cl]2 (62 mg, 0.126 mmol) gave 18 as a yellow oil (77 mg, 83% yield). 1 H NMR (400 MHz, C6D6, 25 °C): δ 5.96 (dd, JHH = 8.6 Hz, JHH = 5.8 Hz, 2H, 3-/5-H), 5.60 (dd, JHH = 9.4 Hz, JHH = 1.0 Hz, 4338


Organometallics

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Table 1. Crystallographic Data and Refinement for 1, 4, 8, and 1214 1

4

8

formula

C20H24B4Cl2Y2

C16H22B2ClOY

C34H52B4Cl2N4Y2

fw

556.35

376.32

808.76

color

colorless

yellow

colorless

cryst syst

monoclinic

orthorhombic

triclinic

space group

P2(1)/c

Fdd2

P1

a, Å

11.800(1)

20.557(3)

8.906(2)

b, Å

8.507(1)

23.076(3)

9.858(2)

c, Å R, deg

12.356(1) 90.00

14.575(2) 90.00

11.773(3) 88.879(5)

β, deg

111.903(2)

90.00

71.535(4)

γ, deg

90.00

90.00

76.056(4)

V, Å3

1150.8(2)

6913.9(2)

949.6(4)

Z

2

16

1

Dcalcd, g/cm3

1.606

1.446

1.414

F(000)

552

3072

416

θ range, deg no. of reflns collected

2.98 to 26.00 6074

1.76 to 25.49 9133

1.83 to 25.49 4938

no. of unique reflns

2256

2300

3454

no. of obsd reflns (I > 2σ(I))

1777

1697

2695

no. of params

136

245

216

goodness of fit

1.098

1.009

1.048

final R, Rw (I > 2σ(I))

0.0584, 0.1451

0.0529, 0.1122

0.0734, 0.2149

ΔFmax,min/e Å3

1.505, 1.136

0.988, 0.446

1.174, 1.157

12

13

14

formula

C10H12B2Cl2Zr

C44.50H40BP2Rh

C13H18BRh

fw

315.94

750.43

287.99

color

yellow

red

yellow

cryst.syst

orthorhombic

triclinic

monoclinic

space group

P2(1)2(1)2(1)

P1

P2(1)/c

a, Å

7.069(1)

10.738(1)

8.254(1)

b, Å

11.120(1)

18.228(1)

13.355(1)

c, Å R, deg

15.586(1) 90.00

19.411(1) 85.753(1)

11.090(1) 90.00

β, deg

90.00

75.266(1)

106.965(1)

γ, deg

90.00

88.749(1)

90.00

V, Å3

1225.4(2)

3664.2(5)

1169.3(2)

Z

4

4

4

Dcalcd, g/cm3

1.713

1.360

1.636

F(000)

624

1548

584

θ range, deg no. of reflns collected

2.25 to 27.00 7221

1.12 to 26.00 20236

2.45 to 27.00 6770

no. of unique reflns

2649

14 141

2539

no. of obsd reflns (I > 2σ(I))

2524

10 275

2173

no.of params

198

827

166

goodness of fit

0.903

1.000

1.159

final R, Rw (I > 2σ(I))

0.0316, 0.0752

0.0482, 0.1237

0.0405, 0.1055

ΔFmax,min, e Å3

0.585, 0.308

1.412, 0.557

0.616, 0.938

2H, 2-/6-H), 4.51 (tt, JHH = 5.8 Hz, JHH = 1.0 Hz, 1H, 4-H), 3.98 (bs, 4H, CH2CHCHCH2), 2.04 (m, 4H, CH2CHCHCH2), 1.82 (m, 4H, CH2CHCHCH2), 1.74 (m, 2H, B(CH2)5CH3), 1.58 (m, 2H, B(CH2)5CH3), 1.41 (m, 4H, B(CH2)5CH3), 1.17 (m, 2H, B(CH2)5CH3), 0.94 (t, JHH = 7.2 Hz, 3H, B(CH2)5CH3). 13C NMR (100 MHz, C6D6, 25 °C): δ 108.9 (d, JRhC = 2.7 Hz), 105.5 (bs), 86.5

(d, JRhC = 3.7 Hz), 68.3 (d, JRhC = 12.5 Hz, CH2CHCHCH2), 33.5 (s), 32.6 (s), 32.3 (s), 32.2 (s), 28.6 (s), 23.3 (s), 14.6 (s). 11B NMR (128 MHz, C6D6, 25 °C): δ 24.9. Anal. Calcd (%) for C19H30BRh: C, 61.32; H, 8.13. Found: C, 61.65; H, 8.08. [C5H5BC(C2H5)dCH(C2H5)]Rh (COD) (19). Following the procedure described for 14, reaction of 6 (76 mg, 0.172 mmol) and 4339


Organometallics [Rh(COD)Cl]2 (85 mg, 0.172 mmol) gave 19 as a yellow oil (107 mg, 84% yield). 1H NMR (400 MHz, C6D6, 25 °C): δ 6.13 (t, JHH = 6.8 Hz, 1H, BC(C2H5)CH(C2H5)), 5.98 (dd, JHH = 9.0 Hz, JHH = 5.8 Hz, 2H, 3-/5-H), 5.75 (dd, JHH = 9.4 Hz, JHH = 1.0 Hz, 2H, 2-/6-H), 4.60 (tt, JHH = 5.8 Hz, JHH = 1.0 Hz, 1H, 4-H), 3.93 (bs, 4H, CH2CHCHCH2), 2.50 (q, JHH = 7.6 Hz, 2H, BC(CH2CH3)CH(C2H5)), 2.28 (dq, JHH = 7.6 Hz, JHH = 7.2 Hz, 2H, BC(C2H5)CH(CH2CH3)), 2.04 (m, 4H, CH2CHCHCH2), 1.82 (m, 4H, CH2CHCHCH2), 1.25 (t, JHH = 7.4 Hz, 3H, BC(CH2CH3)CH(C2H5)), 1.08 (t, JHH = 7.6 Hz, 3H, BC(C2H5)CH(CH2CH3)). 13C NMR (100 MHz, C6D6, 25 °C): δ 138.5 (s, BC(C2H5)CH(C2H5)), 109.0 (d, JRhC = 3.0 Hz), 102.8 (bs), 86.9 (d, JRhC = 3.8 Hz), 69.2 (d, JRhC = 13.2 Hz, CH2CHCHCH2), 32.2 (s), 24.0 (s), 22.2 (s), 15.6 (s), 15.3 (s). 11B NMR (128 MHz, C6D6, 25 °C): δ 21.2. Anal. Calcd (%) for C19H28BRh: C, 61.65; H, 7.62. Found: C, 61.72; H, 7.98. X-ray Crystallography. Suitable single crystals of 1, 4, 8, and 1214 were sealed in thin-walled glass capillaries, and data collection was performed at 20 °C on a Bruker SMART diffractometer with graphite-monochromated Mo KR radiation (λ = 0.71073 Å). The SMART program package was used to determine the unit-cell parameters. The absorption correction was applied using SADABS. The structures were solved by direct methods and refined on F2 by fullmatrix least-squares techniques with anisotropic thermal parameters for non-hydrogen atoms. Hydrogen atoms were refined isotropically at calculated positions without further refinement of the parameters. All calculations were carried out using the SHELXL-97 program. The software used is listed in ref 30. Crystallographic data and refinement for 1, 4, 8, and 1214 are listed in Table 1.

’ ASSOCIATED CONTENT

bS

Supporting Information. Some DFT calculation results, NMR (1H, 13C, 11B, 31P, 89Y) spectra of the complexes, the full list of authors for ref 23, and CIF files giving X-ray crystallographic data for complexes 1, 4, 8, and 1214. This material is available free of charge via the Internet at http://pubs.acs.org.

’ AUTHOR INFORMATION Corresponding Author

*E-mail: [email protected]. Fax: (+86)21-64166128.

’ ACKNOWLEDGMENT This work was supported by the National Natural Science Foundation of China (Grant No. 20672134), the State Key Basic Research & Development Program (Grant No. 2011CB808705), Shanghai Municipal Committee of Science and Technology (10DJ1400104), and Chinese Academy of Sciences. We thank Profs. Eugene Y.-X. Chen (Colorado State University) and Guillermo C. Bazan (University of California, Santa Barbara) for the editorial help. ’ REFERENCES (1) (a) Brown, H. C. Hydroboration; Wiley-Interscience: New York, 1962. (b) Pelter, A.; Smith, K.; Brown, H. C. Borane Reagents; Academic Press: New York, 1988. (c) Burgess, K.; Ohlmeyer, M. J. Chem. Rev. 1991, 91, 1179. (2) (a) Kunz, D.; Erker, G.; Fr€ohlich, R.; Kehr, G. Eur. J. Inorg. Chem. 2000, 409. (b) Paradies, J.; Greger, I.; Kehr, G.; Bergander, K.; Fr€ohlich, R. Angew. Chem., Int. Ed. 2006, 45, 7630. (3) Schumann, H.; Heim, A.; Demtschuk, J.; M€uhle, S. H. Organometallics 2003, 22, 118.

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