Article pubs.acs.org/Organometallics
Reactivity of Traditional Metal−Carbon (Alkyl) versus Nontraditional Metal−Carbon (Cage) Bonds in Organo-Rare-Earth Metal Complexes [η5:σ-(C9H6)(C2B10H10)]Ln(CH2C6H4‑o‑NMe2)(THF)2 Jingying Yang† and Zuowei Xie*,†,‡ †
Department of Chemistry and Center of Novel Functional Molecules, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China ‡ State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin, China S Supporting Information *
ABSTRACT: Equimolar reaction of 1-indenyl-1,2-carborane with Ln(CH2C6H4-o-NMe2)3 in THF gave highly constrainedgeometry complexes [η5:σ-(C9H6)C2B10H10]Ln(CH2C6H4-oNMe2)(THF)2 (Ln = Y (1a), Gd (1b), Dy (1c)). They reacted with RNCNR or 2,6-Me2C6H3NCS to generate the Ln−Calkyl insertion products [η5:σ-(C9H6)C2B10H10]Ln[η2-(RN)2C(CH2C6H4-o-NMe2)](THF) (R = TMS, Ln = Y (2a), Gd (2b); R = tBu, Ln = Y (3a)) or [η 5 :σ(C9H6)C2B10H10]Dy[η2-(2,6-Me2C6H3)NC(CH2C6H4-o-NMe2)S](THF)2 (4c). Treatment of 2a with 1 equiv of R′NC NR′ to give the Y−Ccage insertion complexes [η5:σ-(C9H6){N(R′)C(NR′)}C2B10H10]Y[η2-{(TMS)N}2C(CH2C6H4-oNMe2)] (R′ = Cy (5a), iPr (6a)). Similarly, unsaturated compounds Ph2CCO and Py2CO (Py = 2-pyridyl) also inserted into the Y−Ccage bond in 2a to yield [η5:σ-(C9H6){OC(CPh2)}C2B10H10]Y[η2-{(TMS)N}2C(CH2C6H4-o-NMe2)] (7a) and [η5:σ-(C9H6){OC(Py)2}C2B10H10]Y[η2-{(TMS)N)}2C(CH2C6H4-o-NMe2)](THF) (8a), respectively. In sharp contrast to the earlier reports that the nontraditional metal−Ccage σ bonds in metal−carboranyl complexes are generally inert toward electrophiles, the insertion of unsaturated molecules into the Y−Ccage σ bond in 2a represents the first example of this type of reactions. These results shed some light on how to activate the nontraditional metal−carbon (cage) bonds in metal−carboranyl complexes. All new complexes were characterized by spectroscopic techniques and elemental analyses. Some were further confirmed by single-crystal X-ray analyses.
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[η5:σ-(C9H6)C2B10H10]Ln(CH2C6H4-o-NMe2)(THF)2 with a Ln−Ccage−Ccage angle of around 90° would be reactive toward unsaturated molecules.5 Our results show, for the first time, that the Ln−Ccage bonds in these complexes indeed undergo insertion reaction with unsaturated molecules, although they are less reactive than those of Ln−Calkyl bonds. These findings are reported in this article.
INTRODUCTION The construction and transformation of metal−carbon (M−C) bonds constitute the central themes of organometallic chemistry. Most of the work in this field has focused on traditional M−C bonds involving tetravalent carbon, and relatively little attention has been paid to the chemistry of nontraditional metal−carbon (M−Ccage) bonds, in which the carbon is hypervalent. Our previous work has shown that the M−Ccage bonds in transition-metal−carboranyl complexes are generally inert toward electrophiles1 and, hence, significantly different from traditional M−C bonds. This lack of reactivity can be ascribed to steric effect imposed by the carboranyl moiety.1,2 To overcome such steric problem and to activate M− Ccage bonds, a series of metal−carboryne complexes bearing a three-membered metallacyclopropane ring are prepared since a more open coordination sphere around the metal and ring strain can enhance the reactivity of M−Ccage bonds.3 In fact, nickel−carboryne, (η2-C2B10H10)Ni(PPh3)2, can react with alkynes or alkenes to give the cycloaddition or coupling products.4 These results clearly indicate that the aforementioned strategy can turn on the reactivity of the M−Ccage bonds. In this connection, we wondered if the Ln−Ccage bonds in highly constrained-geometry organo-rare-earth complexes © XXXX American Chemical Society
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RESULTS AND DISCUSSION Complex [η 5 :σ-(C 9 H 6 )C 2 B 10 H 10 ]Y(CH 2 C 6 H 4 -o-NMe 2 )(THF)2 (1a) was prepared according to the method developed in our laboratory.5 Similarly, [η5:σ-(C9H6)C2B10H10]Ln(CH2C6H4-o-NMe2)(THF)2 (Ln = Gd (1b), Dy (1c)) were synthesized by treatment of 1-C9H7-1,2-C2B10H116 with 1 equiv of Ln(CH2C6H4-o-NMe2)3 in THF in 61−77% yields (Scheme 1). These complexes contain two types of Ln−C σ bonds: traditional Ln−Calkyl and nontraditional Ln−Ccage, which offer a good model for the study of relative reactivities. Special Issue: Mike Lappert Memorial Issue Received: November 29, 2014
A
DOI: 10.1021/om501212e Organometallics XXXX, XXX, XXX−XXX
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Organometallics Scheme 1
Figure 1. Molecular structure of [η5:σ-(C9H6)C2B10H10]Y[η2{(TMS)N}2C(CH2C6H4-o-NMe2)](THF) (2a).
Reaction of 1a or 1b with 1 equiv of bis(trimethylsilyl)carbodiimide in refluxing toluene gave, after recrystallization from toluene/THF, the Ln−Calkyl insertion products [η5:σ(C9H6)C2B10H10]Ln[η2-{(TMS)N}2C(CH2C6H4-o-NMe2)](THF) (Ln = Y (2a), Gd (2b)) as pale yellow crystals in 71% or 43% isolated yield, respectively. Under the same reaction condition, 1a reacted with 1 equiv of di-tert-butylcarbodiimide to afford [η5:σ-(C9H6)C2B10H10]Y[η2-(tBuN)2C(CH2C6H4-oNMe2)](THF) (3a) as pale yellow crystals in 81% isolated yield. In a similar manner, treatment of 1c with 1 equiv of 2,6dimethylphenyl isothiocyanate in toluene generated [η5:σ(C 9 H 6 )C 2 B 10 H 10 ]Dy[η 2 -N(2,6-Me 2 C 6 H 3 )C(CH 2 C 6 H 4 -oNMe2)S](THF)2 (4c) as pale yellow crystals in 49% yield (Scheme 1). These results show that unsaturated molecules can insert into the Ln−Calkyl σ bond to give the monoinsertion products, suggesting that the Ln−Calkyl bond is more reactive than the Ln−Ccage one. Such results are consistent with our earlier observations in the reaction chemistry of metal− carboranyl complexes.1,2 The main feature of the 1H NMR spectra of the diamagnetic complexes 2a/3a in comparison with that of 1a was the appearance of resonances of TMS in 2a and tBu in 3a, as well as the chemical shifts of the benzyl protons that were shifted from 1.71 to 1.84 ppm in 1a to 3.70−3.96 ppm in 2a/3a. The characteristic peak of the sp2 C atom of the newly formed amidinato group was observed at 183.5 ppm in 3a and 176.8 ppm in 4a, respectively. The 11B NMR spectrum of 2a showed a 2:2:6 pattern, and that of 3a exhibited a 2:2:3:2:1 pattern, which is significantly different from that of the 1:1:8 pattern in 1a. Complexes 2b and 4c did not offer useful NMR information due to their paramagnetic properties. In addition, 1b, 1c, 2a, 2b, 3a, and 4c were also characterized by elemental analyses. Figures 1 and 2 show single-crystal X-ray structures of 2a and 3a. In both structures, the Y atom is η2-bonded to the amidinato group, η5-bonded to the indenyl ligand, σ-bonded to the cage carbon, and coordinated to one THF in a four-legged
Figure 2. Molecular structure of [η5:σ-(C9H6)C2B10H10]Y[η2-(tBuN)2C(CH2C6H4-o-NMe2)](THF) (3a).
piano stool geometry. The selected bond distances and angles are compiled in Table 1 for comparison. The average Y−N distances of 2.311(2) Å in 2a and 2.295(2) Å in 3a are comparable to that of 3.391(5) Å in TpMe2Y[η2-(iPrN)2C(CH2Ph)](NHPh) (TpMe2 = tris(3,5-dimethyl(pyrazolyl)borate) and 3.349(3) Å in TpMe2Y[η2-(iPrN)2C(CH2Ph)](NHAr).7 The average Y−Cring (indenyl group) distances of 2.736(3) Å in 2a and 2.733(3) Å in 3a are close to that of 2.74(1) Å in [η5:σ-(C9H6)C2B10H10]Y(CH2C6H4-o-NMe2)(DME) (1a′)5 and comparable to those observed in this family of complexes.8 The Y−Ccage distances of 2.571(3) Å in 2a and 2.587(3) Å in 3a are also comparable to that of 2.61(1) Å in 1a′,5 2.641(8) Å in [{η2:σ-(C9H6)(C2B10H10)}Y(THF)2(μ−μ)2K(THF)2]2,5 and 2.538(3) Å in [η5:σ-iPr2NP(C9H6)(C2B10H10)]2Y[Li(THF)(DME)2].9 On the other hand, the Y−Ccage−Ccage angles of 91.7(2)° in 2a and 88.9(2)° in 3a are very close to that of 91.4(5)° in 1a′, which are significantly smaller than that of 120° normally observed in this type of complexes.1,3,5 Such an unusually small angle strongly indicates that these complexes have a highly constrained geometry. As revealed by single-crystal X-ray analyses, complex 4c adopts a similar geometry to that of 2a and 3a, in which the Dy atom is η2-bonded to the NCS group, η5-bonded to an indenyl group, σ-bonded to the cage carbon atom, and coordinated by two THF molecules (Figure 3). The Dy−Ccage−Ccage angle of 91.1(6)° is very close to those found in 2a and 3a. B
DOI: 10.1021/om501212e Organometallics XXXX, XXX, XXX−XXX
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Organometallics Table 1. Selected Bond Lengths (Å) and Angles (deg) in 1a′, 2a, 3a, 4c, 5a, and 8aa 1a′
2a
3a
4c
5a
8a
Y
Y
Y
Dy
Y
Y
Ln−Ccage Ln−X Ccage−Cring Ccage−Ccage Ln−N
2.74(1) 2.88(1) 2.79(1) 2.79(1) 2.65(1) 2.62(1) 2.61(1) 2.38(1) (X = C) 1.50(1) 1.72(1) 2.587(8)
2.736(3) 2.598(3) 2.627(3) 2.771(3) 2.890(3) 2.797(3) 2.571(3)
2.733(3) 2.572(3) 2.656(3) 2.815(3) 2.891(3) 2.731(3) 2.587(3)
Ln−Ccage−Ccage Cring−Ccage−Ccage
91.4(5) 109.9(7)
1.493(4) 1.716(4) 2.313(2) 2.308(2) 91.71(2) 110.1(2)
1.480(4) 1.748(4) 2.289(2) 2.300(2) 88.9(2) 110.1(2)
2.714(12) 2.585(11) 2.631(11) 2.746(12) 2.859(12) 2.751(12) 2.621(12) 2.761(3) (X = S) 1.487(16) 1.729(16) 2.448(9)
(Ln) av Ln−Cring Ln−Cring
a
91.1(6) 109.6(9)
2.667(2) 2.656(2) 2.673(2) 2.706(2) 2.635(2) 2.665(2)
2.785(5) 2.766(5) 2.864(5) 2.852(5) 2.738(5) 2.705(5)
2.226(19) (X = N) 1.448(3) 1.704(3) 2.305(2) 2.315(2)
2.127(3) (X = O) 1.481(7) 1.776(7) 2.401(4) 2.441(4)
117.0(2)
126.9(5)
1a′ = [η5:σ-(C9H6)C2B10H10]Y(CH2C6H4-o-NMe2)(DME) (see ref 5).
Scheme 2
Figure 3. Molecular structure of [η5:σ-(C9H6)C2B10H10]Dy[η2-(2,6Me2C6H3)NC(CH2C6H4-o-NMe2)S](THF)2 (4c).
It is believed that unusually small Ln−Ccage−Ccage angles of around 90° observed in the monoinsertion products 2−4 can create angle strain and open up the coordination sphere of the central metal atom, promoting the reaction of a Ln−Ccage σ bond in these molecules with unsaturated species. Subsequently, treatment of 2a with 1 equiv of CyNC NCy (Cy = cyclohexyl) or iPrNCNiPr in THF gave the Y−Ccage insertion products [η5:σ-(C9H6){N(R)C(NR)}C2B10H10]Y[η2-{(TMS)N}2C(CH2C6H4-o-NMe2)] (R = Cy (5a), iPr (6a)) in 50−78% isolated yields. Under similar reaction conditions, reaction of 2a with 1 equiv of Ph2CC O or Py 2 CO (Py = 2-pyridyl) also afforded the corresponding Y−Ccage insertion complex [η5:σ-(C9H6){OC(CPh2)}C2B10H10]Y[η2-{(TMS)N}2C(CH2C6H4-o-NMe2)] (7a) in 56% yield or [η5:σ-(C9H6){OC(C5H4N)2}C2B10H10]Y[η2-{(TMS)N}2C(CH2C6H4-o-NMe2)] (8a) in 38% yield, respectively (Scheme 2). It was noteworthy that 2a did not react with bis(trimethylsilyl)carbodiimide even under forced reaction conditions because of steric reasons. The 1H NMR spectra of 5−8 showed clearly the presence of the inserted molecules. Their 13C NMR spectra displayed the newly formed unique NCN carbon at 190.0 ppm in 5a and 185.4 ppm in 6a, a unique OCC carbon at 156.2 ppm in 7a, and the quaternary O-CPy2 carbon at 99.9 ppm in 8a. The 11B
NMR spectra exhibited a pattern of 2:2:2:4 for 5a, 2:4:4 for 6a, 2:2:2:4 for 7a, and 4:6 for 8a, respectively. The molecular structures of 5a and 8a were confirmed by single-crystal X-ray analyses and are shown in Figures 4 and 5, respectively. The Y atom in 5a is η5-bound to an indenyl ligand, η2-bound to an amidinato moiety, and σ-bound to a nitrogen atom in a three-legged piano stool geometry. The Y−N(1)/ N(2) distances of 2.305(2)/2.315(2) Å are much longer than the Y−N(4) distance of 2.226(2) Å. The latter is a typical Y− N(amido) bond.8 As a result, the N(4)−C(42) distance of 1.406(3) Å is significantly longer than the N(5)−C(42) distance of 1.267(3) Å, suggesting that the newly formed amidinato is not a delocalized unit. The Y atom in 8a adopts a five-legged piano stool geometry by coordinating to an η5-indenyl, an η2-amidinato, two oxygen atoms, and one nitrogen atom from the pyridyl group. As the coordination number of the Y atom is increased in 8a, the C
DOI: 10.1021/om501212e Organometallics XXXX, XXX, XXX−XXX
Organometallics
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EXPERIMENTAL SECTION
General Procedures. All experiments were performed under an atmosphere of dry argon with the rigid exclusion of air and moisture using standard Schlenk or cannula techniques, or in a glovebox. All solvents were distilled from sodium benzophenone ketyl immediately prior to use. Complex Ln(CH2C6H4-o-NMe2)3,10 1-indenyl-1,2carborane,6 and [η5:σ-(C9H6)C2B10H10]Y(CH2C6H4-o-NMe2)(THF)2 (1a)5 were prepared according to literature methods. All other chemicals were purchased from Aldrich Chemical Co. and used as received unless otherwise noted. Infrared spectra were obtained from KBr pellets prepared in the glovebox on a PerkinElmer 1600 Fourier transform spectrometer. 1H NMR spectra were recorded on a Varian Inova 400 spectrometer at 400 MHz. The 13C NMR spectra were recorded on a Varian Inova 400 spectrometer at 100 MHz. The 11B NMR spectra were recorded on a Varian Inova 400 spectrometer at 128 MHz. All chemical shifts were reported in δ units with reference to the residual protons and carbons of the deuterated solvents for proton and carbon chemical shifts and to external BF3·OEt2 (0.00 ppm) for boron chemical shifts. Elemental analyses were performed by MEDAC Ltd., U.K., or the Shanghai Institute of Organic Chemistry, CAS, China. Preparation of [η5:σ-(C9H6)C2B10H10]Gd(CH2C6H4-o-NMe2)(THF)2 (1b). A THF solution (10 mL) of 1-indene-1,2-carborane (258 mg, 1.0 mmol) was slowly added to a THF solution (5 mL) of Gd(CH2C6H4-o-NMe2)3 (560 mg, 1.0 mmol) at room temperature, and the reaction mixture was stirred at room temperature for 24 h. The clear red solution was concentrated to 3 mL, to which was added n-hexane (15 mL). Complex 1b was obtained as a pale yellow solid after this solution stood at room temperature overnight (534 mg, 77%). Anal. Calcd for C26H40B10GdNO1.5 (1b − 0.5THF): C, 47.61; H, 6.15; N, 2.14. Found: C, 47.76; H, 6.52; N, 1.95. Preparation of [η5:σ-(C9H6)C2B10H10]Dy(CH2C6H4-o-NMe2)(THF)2 (1c). This complex was prepared as a light yellow solid from Dy(CH2C6H4-o-NMe2)3 (565 mg, 1.0 mmol) and 1-indene-1,2carborane (258 mg, 1.0 mmol) using procedures identical to those reported for 1a: yield 425 mg (61%). Anal. Calcd for C24H36B10DyNO (1c − THF): C, 46.11; H, 5.80; N, 2.24. Found: C, 46.15; H, 5.55; N, 1.99. Preparation of [η5:σ-(C9H6)C2B10H10]Y[η2-{(TMS)N}2C(CH2C6H4-oNMe2)](THF) (2a). To a toluene (20 mL) solution of 1a (160 mg, 0.26 mmol) was slowly added TMSNCNTMS (49 mg, 0.26 mmol) at room temperature, and the reaction mixture was heated to reflux at 110 °C for 2 h. The resulting clear yellow solution was concentrated under vacuum to about 2 mL and stood at −30 °C. The precipitate was collected and redissolved in THF (5 mL). Complex 2a was obtained as colorless crystals after the solution stood at room temperature for 2 days (136 mg, 71%). 1H NMR (400 MHz, benzened6): δ 8.27 (d, J = 8.0 Hz, 1H), 7.43 (d, J = 8.0 Hz, 1H), 7.25 (d, J = 7.0 Hz, 1H), 7.12 (m, 2H), 7.03 (d, J = 3.6 Hz, 1H), 6.90 (t, J = 8.0 Hz, 2H), 6.81 (t, J = 8.0 Hz, 1H), 6.49 (d, J = 3.6 Hz, 1H) (aromatic H), 3.85 (d, J = 16.0 Hz, 1H) (CHH), 3.70 (d, J = 16.0 Hz, 1H) (CHH), 3.16 (m, 4H) (THF), 2.36 (s, 6H) (N(CH3)2), 1.07 (m, 4H) (THF), −0.02 (s, 18H) (TMS). 13C{1H} NMR (100 MHz, benzened6): δ 183.5 (NCN), 152.5, 130.8, 130.0, 129.3, 128.6, 127.4, 125.7, 124.1, 123.8, 123.4, 123.3, 123.1, 122.2, 119.7 (aromatic C), 98.6, 98.2 (cage C), 44.1 (N(CH3)2), 41.7 (CH2), 71.0, 25.2 (THF), 2.34 (TMS) 11 1 B{ H} NMR (128 MHz, benzene-d6): δ 1.3 (2B), 2.3 (2B), 6.2 (6B). IR (KBr, cm −1 ): ν 2574 (vs) (B−H). Anal. Calcd for C31H54B10N3OSi2Y (2a): C, 50.45; H, 7.38; N, 5.69. Found: C, 50.51; H, 7.12; N, 5.40. Preparation of [η5:σ-(C9H6)C2B10H10]Gd[η2-{(TMS)N}2C(CH2C6H4-oNMe2)](THF) (2b). This complex was prepared as a light yellow solid from 1b (235 mg, 0.34 mmol) and TMSNCNTMS (65 mg, 0.34 mmol) using procedures identical to those reported for 2a: yield 118 mg (43%). IR (KBr, cm−1): ν 2574 (vs) (B−H). Anal. Calcd for C31H54B10GdN3OSi2 (2b): C, 46.18; H, 6.75; N, 5.21. Found: C, 46.39; H, 7.03; N, 5.19. Preparation of [η5:σ-(C9H6)C2B10H10]Y[η2-(tBuN)2C(CH2C6H4-oNMe2)](THF) (3a). This complex was prepared as a white solid from 1a (80 mg, 0.13 mmol) and tBuNCNtBu (21 mg, 0.13 mmol)
Figure 4. Molecular structure of 5a.
Figure 5. Molecular structure of 8a (the coordinated THF is represented by lines for clarity).
corresponding bond distances around the Y atom are generally longer than those in 2a and 5a (Table 1).
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CONCLUSION Acid−base reaction of 1-indenyl-1,2-carborane with Ln(CH2C6H4-o-NMe2)3 in THF afforded highly constrainedgeometry complexes [η5:σ-(C9H6)C2B10H10]Ln(CH2C6H4-oNMe2)(THF)2 that bear two types of Ln−C σ bonds, Ln− Calkyl and Ln−Ccage. Reactivity studies show that both are reactive toward unsaturated molecules, though the Ln−Calkyl σ bond is more reactive than the corresponding Ln−Ccage one due to steric reasons.1,2 In view of the earlier observations that nontraditional metal−carbon bonds in metal−carboranyl complexes are generally inert toward eletrophiles,3 current results are of particular interest and demonstrate a way to activate nontraditional M−Ccage σ bonds in metal−carboranyl complexes. Such activation is achieved by creating angle strain and opening up the coordination sphere of the central metal atom, which would shed some light on the activation of nontraditional metal−carbon bonds. D
DOI: 10.1021/om501212e Organometallics XXXX, XXX, XXX−XXX
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Organometallics
Hz, 2H), 7.10 (m, 2H), 7.04 (t, J = 7.6 Hz, 2H), 6.98 (t, J = 8.0 Hz, 2H), 6.90 (m, 2H), 6.75 (d, J = 3.6 Hz, 2H) (aromatic H), 4.11 (br s, 2H) (CH2), 2.59 (s, 6H, N(CH3)2), −0.05 (s, 18H, TMS). 13C{1H} NMR (100 MHz, pyridine-d5): δ 185.2 (NCN), 156.2 (OC), 153.0, 146.2, 145.7, 134.1, 132.3, 132.0, 131.8, 129.9, 129.2, 128.7, 127.3, 125.3, 120.0, 119.8, 119.4, 119.3, 117.1 (aromatic C), 71.0 (cage C), 44.2 (N(CH3)2), 43.2 (CH2), 2.6 (TMS). 11B{1H} NMR (128 MHz, pyridine-d5): δ 0.5 (2B), −2.8 (2B), −6.3 (2B), −10.0 (4B). IR (KBr, cm−1): ν 2590 (vs) (B−H). Anal. Calcd for C41H56B10N3OSi2Y (7a): C, 57.26; H, 6.56; N, 4.89. Found: C, 57.59; H, 6.38; N, 4.37. Preparation of [η5:σ-(C9H6){OC(Py)2}]C2B10H10]Y[η2-{(TMS)N}2C(CH2C6H4-o-NMe2)](THF) (8a). To a THF solution of 2a (103 mg, 0.14 mmol) was added Py2CO (26 mg, 0.14 mmol) at −30 °C, and the reaction mixture was stirred at room temperature overnight. The resulting clear red solution was concentrated under vacuum to about 2 mL. Complex 8a was obtained as red crystals after the solution stood at room temperature for a week (49 mg, 38%). 1H NMR (400 MHz, pyridine-d5): δ 9.95 (d, J = 8.0 Hz, 2H), 8.96 (d, J = 8.0 Hz, 2H), 8.59 (d, J = 8.0 Hz, 1H), 8.33 (d, J = 8.0 Hz, 1H), 7.99 (t, J = 8.0 Hz, 1H), 7.80 (d, J = 8.0 Hz, 1H), 7.55 (m, 2H), 7.24 (m, 3H), 7.12 (m, 3H), 6.85 (d, J = 3.0 Hz, 2H), (aromatic H), 3.83 (d, J = 16.0 Hz, 1H), 3.70 (d, J = 16.0 Hz, 1H) (CH2), 3.20 (m, 4H) (THF), 2.48 (s, 6H, N(CH3)2), 1.05 (m, 4H) (THF), 0.51 (s, 9H), −0.87 (s, 9H) (TMS). 13 C{1H} NMR (100 MHz, pyridine-d5): δ 181.2 (NCN), 170.4, 165.1, 152.7, 147.1, 146.3, 138.3, 136.3, 133.7, 130.2, 129.4, 128.7, 128.5, 128.3, 128.0, 127.6, 126.4, 125.8, 125.0, 124.2, 124.0, 123.1, 123.0, 122.8, 122.2, 121.5, 120.0 (aromatic C), 99.9 (C-O), 89.0, 88.8 (cage C), 44.0 (N(CH3)2), 43.2 (CH2), 4.5, 1.7 (TMS), 67.8, 25.8 (THF). 11 1 B{ H} NMR (128 MHz, pyridine-d5): δ −3.6 (4B), −11.2 (6B). IR (KBr, cm−1): ν 2563 (vs) (B−H). Anal. Calcd for C42H62B10N5O2Si2Y (8a): C, 54.70; H, 6.78; N, 7.59. Found: C, 54.79; H, 6.54; N, 7.11. X-ray Structure Determination. All single crystals were immersed in Paraton-N oil and sealed under N2 in thin-walled glass capillaries. Data were collected on a Bruker SMART 1000 CCD diffractometer using Mo Kα radiation. An empirical absorption correction was applied using the SADABS program.11 All structures were solved by direct methods and subsequent Fourier difference techniques and refined anisotropically for all non-hydrogen atoms by full-matrix least-squares calculations on F2 using SHELXTL.12 The hydrogen atoms were geometrically fixed using the riding model. Crystal data and details of data collection and structure refinements are included in the Supporting Information.
using procedures identical to those reported for 2a: yield 74 mg (81%). 1H NMR (400 MHz, benzene-d6): δ 8.29 (d, J = 8.6 Hz, 1H), 7.54 (d, J = 8.2 Hz, 1H), 7.05 (d, J = 3.6 Hz, 2H), 6.94 (m, 6H) (aromatic H), 3.95 (d, J = 16.0 Hz, 1H) (CHH), 3.87 (d, J = 16.0 Hz, 1H) (CHH), 3.40 (m, 4H) (THF), 2.40 (s, 6H) (N(CH3)2), 1.18 (m, 4H) (THF), 1.07 (m, 9H) (tBu), 0.68 (m, 9H) (tBu). 13C{1H} NMR (100 MHz, benzene-d6): δ 176.8 (NCN), 152.0, 132.7, 130.4, 126.8, 123.1, 122.8, 122.0, 119.7 (aromatic C), 100.0, 99.7 (cage C), 80.43 (NCMe3), 70.6 (THF), 44.1 (N(CH3)2), 25.3 (THF), 22.5, 23.1 ((CH3)3). 11B{1H} NMR (128 MHz, benzene-d6): δ 0.0 (2B), −3.9 (2B), −8.0 (3B), −11.4 (2B), −17.3 (1B). IR (KBr, cm−1): ν 2569 (vs) (B−H). Anal. Calcd for C31H50B10N3O0.5Y (3a − 0.5THF): C, 55.59; H, 7.52; N, 6.27. Found: C, 55.82; H, 7.66; N, 6.57. Preparation of [η5:σ-(C9H6)C2B10H10]Dy[η2-N(2,6-Me2C6H3)C(CH2C6H4-o-NMe2)S](THF)2 (4c). To a toluene (10 mL) solution of 1c (89 mg, 0.13 mmol) was added 2,6-Me2C6H3NCS (21 mg, 0.13 mmol) at room temperature, and the reaction mixture was heated to reflux at 110 °C for 10 min. The resulting clear orange solution was concentrated under vacuum to about 2 mL and stood at −30 °C. The precipitate was collected and redissolved in 5 mL of THF. Complex 4c was obtained as colorless crystals after the solution stood at −30 °C for a week (55 mg, 49%). IR (KBr, cm−1): ν 2573 (vs) (B−H). Anal. Calcd for C33H45B10DyN2OS (4c − THF): C, 50.27; H, 5.75; N, 3.55. Found: C, 50.15; H, 5.55; N, 3.89. Preparation of [η5:σ-(C9H6){N(Cy)C(NCy)}C2B10H10]Y[η2-[{TMS)N}2C(CH2C6H4-o-NMe2)] (5a). To a THF solution of 2a (103 mg, 0.14 mmol) was added CyNCNCy (29 mg, 0.14 mmol) at −30°, and the reaction mixture was stirred at room temperature overnight. The resulting clear red solution was concentrated under vacuum to about 2 mL and stood at −30 °C for a week. Complex 5a was collected as red crystals (61 mg, 50%). 1H NMR (400 MHz, pyridine-d5): δ 8.53 (d, J = 6.8 Hz, 1H), 7.76 (d, J = 7.2 Hz, 1H), 7.50 (d, J = 7.2 Hz, 2H), 7.32 (t, J = 7.2 Hz, 1H), 7.23 (t, J = 7.2 Hz, 2H), 7.16 (t, J = 6.8 Hz, 1H), 6.94 (d, J = 5.4 Hz, 2H) (aromatic H), 4.60 (m, 2H) (NCH), 4.17 (d, J = 16.0 Hz, 1H), 4.10 (d, J = 16.0 Hz, 1H) (CH2), 2.57 (s, 6H) (N(CH3)2), 2.08 (br s, 2H), 1.94 (m, 2H), 1.53 (m, 5H), 1.40 (m, 5H), 0.90 (m, 6H) (Cy), 0.00 (s, 18H) (TMS). 13C{1H} NMR (100 MHz, pyridine-d5): δ 190.0 (NCN), 174.9 (NCN), 145.9, 145.4, 140.7, 137.1, 132.4, 131.5, 131.3, 129.4, 128.9, 128.3, 124.8, 122.4, 122.0, 120.50, 120.2 (aromatic C), 70.2 (cage C), 54.8, 37.7, 36.4, 26.0, 25.9 (Cy), 44.11 (N(CH3)2), 43.1 (CH2), 2.2 (TMS). 11B{1H} NMR (128 MHz, pyridine-d5): δ 3.1 (2B), −5.8 (2B), −11.0 (4B), −29.0 (2B). IR (KBr, cm−1): ν 2561 (vs) (B−H). Anal. Calcd for C40H68B10N5Si2Y (5a): C, 55.08; H, 7.86; N, 8.03. Found: C, 55.20; H, 8.06; N, 7.92. Preparation of [η5:σ-(C9H6){N(iPr)C(NiPr)}C2B10H10]Y[η2-{(TMS)N}2C(CH2C6H4-o-NMe2)] (6a). This complex was prepared from 2a (103 mg, 0.14 mmol) and iPrNCNiPr (18 mg, 0.14 mmol) using the procedures identical to those reported for 5a: yield 87 mg (78%). 1 H NMR (400 MHz, pyridine-d5): δ 8.48 (d, J = 7.6 Hz, 2H), 7.83 (t, J = 7.6 Hz, 2H), 7.51 (d, J = 7.6 Hz, 2H), 7.33 (t, J = 7.6 Hz, 2H), 7.00 (d, J = 3.4 Hz, 2H) (aromatic H), 4.16 (br s, 2H) (CH2), 3.90 (m, 2H) (NCH(CH3)2), 2.61 (s, 6H) (N(CH3)2), 0.73 (d, J = 6.4 Hz, 6H), 0.62 (d, J = 6.4 Hz, 6H) (NCH(CH3)2), 0.05 (s, 18H) (TMS). 13 C{1H} NMR (100 MHz, pyridine-d5): δ 184.7 (NCN), 185.4 (NCN), 153.11, 132.5, 131.9, 129.4, 129.3, 128.7, 128.2, 124.0, 120.0, 120.1, 118.8, 118.7, 117.8, 117.0, 108.0, 107.7 (aromatic C), 72.5 (cage C), 49.01 (NCHMe2), 44.2 (N(CH3)2), 43.2 (CH2), 26.2, 26.0 (NCH(CH3)2), 2.5 (TMS). 11B{1H} NMR (128 MHz, pyridine-d5): δ −1.3 (2B), −10.1 (4B), −12.1 (4B). IR (KBr, cm−1): ν 2557 (vs) (B− H). Anal. Calcd for C34H60B10N5Si2Y (6a): C, 51.56; H, 7.64; N, 8.84. Found: C, 51.38; H, 7.78; N, 8.47. Preparation of [η5:σ-(C9H6){OC(CPh2)}C2B10H10]Y[η2-{(TMS)N}2C(CH2C6H4-o-NMe2))] (7a). To a THF solution of 2a (103 mg, 0.14 mmol) was added Ph2CCO (28 mg, 0.14 mmol) at −30 °C, and the reaction mixture was stirred at room temperature overnight. The resulting clear red solution was concentrated under vacuum to about 2 mL. Complex 7a was obtained as red crystals after this solution stood at −30 °C for 48 h (67 mg, 56%). 1H NMR (400 MHz, pyridine-d5): δ 8.24 (d, J = 7.6 Hz, 1H), 7.73 (d, J = 7.6 Hz, 1H), 7.61 (d, J = 7.2 Hz, 2H), 7.44 (d, J = 8.0 Hz, 2H), 7.30 (d, J = 8.0 Hz, 2H), 7.24 (t, J = 7.6
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ASSOCIATED CONTENT
S Supporting Information *
Crystallographic data in CIF format for 2a, 3a, 4c, 5a, and 8a. This material is available free of charge via the Internet at http://pubs.acs.org.
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS The work described in this paper was supported by grants from the Research Grants Council of the Hong Kong Special Administration Region (Project No. CUHK7/CRF/12G and 14306114) and State Key Laboratory of Elemento-Organic Chemistry, Nankai University (Project No. 201321). We thank Ms. Hoi-Shan Chan for single-crystal X-ray analyses.
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DEDICATION Dedicated to the memory of Professor Mike Lappert, a pioneer in organometallic chemistry E
DOI: 10.1021/om501212e Organometallics XXXX, XXX, XXX−XXX
Article
Organometallics
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REFERENCES
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DOI: 10.1021/om501212e Organometallics XXXX, XXX, XXX−XXX
