Synthesis, structural characterization, reactivity, and thermal stability of [η5:σ-Me2C(C5H4)(C 2B10H10)]Ti(R)(NMe2)

Article abstract of DOI:10.1021/ic0604664

Reaction of [η:⁵σ-Me₂C(C₅H ₄)(C₂B₁₀H₁₀)]TiCl(NMe₂) (1) with 1 equiv of PhCH₂K, MeMgBr, or Me₃SiCH ₂Li gave corresponding organotitanium alkyl complexes [η: ⁵σ-Me₂C(C₅H₄)(C ₂B₁₀H₁₀)]Ti(R)(NMe₂) (R = CH ₂Ph (2), CH₂SiMe₃ (4), or Me (5)) in good yields. Treatment of 1 with 1 equiv of n-BuLi afforded the decomposition product {[η:⁵σ-Me₂C(C₅H₄)(C ₂B₁₀H₁₀)]Ti}₂(μ-NMe)(μ: σ-CH₂NMe) (3). Complex 5 slowly decomposed to generate a mixed-valence dinuclear species {[η:⁵σ-Me ₂C(C₅H₄)(C₂B₁₀H ₁₀)]Ti}₂(μ-NMe₂)(μ:σ-CH ₂NMe) (6). Complex 1 reacted with 1 equiv of PhNCO or 2,6-Me ₂C₆H₃NC to afford the corresponding monoinsertion product [η:⁵σ-Me₂C(C ₅H₄)(C₂B₁₀H₁₀)]Ti(Cl) [η²-OC(NMe₂)NPh] (7) or [η:⁵σ- Me₂C(C₅H₄)(C₂B₁₀H ₁₀)]Ti(Cl)[η²-C(NMe₂)=N(2,6-Me ₂C₆H₃)] (8). Reaction of 4 or 5 with 1 equiv of R′NC gave the titanium η²-iminoacyl complexes [η: ⁵σ-Me₂C(C₅H₄)(C ₂B₁₀H₁₀)]Ti(NMe₂)[η²- C(R)=N(R′)] (R = CH₂SiMe₃, R′ = 2,6-Me ₂C₆H₃ (9) or ^tBu (10); R = Me, R′ = 2,6-Me₂C₆H₃ (11) or ^tBu (12)). The results indicated that the unsaturated molecules inserted into the Ti-N bond only in the absence of the Ti-C(alkyl) bond and that the Ti-C(cage) bond remained intact. All complexes were fully characterized by various spectroscopic techniques and elemental analyses. Molecular structures of 2, 3, 6-8, and 10-12 were further confirmed by single-crystal X-ray analyses.

Full text of DOI:10.1021/ic0604664

Inorg. Chem. 2006, 45, 5675−5683
Synthesis, Structural Characterization, Reactivity, and Thermal Stability
of [η5
-Me2C(C5H4)(C2B10H10)]Ti(R)(NMe2)
:σ
Hong Wang, Yaorong Wang, Hoi-Shan Chan, and Zuowei Xie*
Department of Chemistry and Center of NoVel Functional Molecules, The Chinese UniVersity of
Hong Kong, Shatin, New Territories, Hong Kong, China
Received March 20, 2006
Reaction of [η 5
corresponding organotitanium alkyl complexes [η 5
SiMe3 (4), or Me (5)) in good yields. Treatment of 1 with 1 equiv of n-BuLi afforded the decomposition product
-Me2C(C5H4)(C2B10H10)]Ti 2 µ-NMe)( -CH2NMe) (3). Complex 5 slowly decomposed to generate a mixed-
valence dinuclear species -Me2C(C5H4)(C2B10H10)]Ti 2 µ-NMe2)( -CH2NMe) (6). Complex 1 reacted with 1
equiv of PhNCO or 2,6-Me2C6H3NC to afford the corresponding monoinsertion product [η 5
-Me2C(C5H4)(C2B10H10)]-
Ti(Cl)[ -Me2C(C5H4)(C2B10H10)]Ti(Cl)[
2-OC(NMe2)NPh] (7) or [η 5
or 5 with 1 equiv of R NC gave the titanium
2-iminoacyl complexes [η 5
C(R) N(R )] (R CH2SiMe3, R′ ) 2,6-Me2C6H3 (9) or Bu (10); R
The results indicated that the unsaturated molecules inserted into the Ti
C(alkyl) bond and that the Ti C(cage) bond remained intact. All complexes were fully characterized by various
:
σ
-Me2C(C5H4)(C2B10H10)]TiCl(NMe2) (1) with 1 equiv of PhCH2K, MeMgBr, or Me3SiCH2Li gave
-Me2C(C5H4)(C2B10H10)]Ti(R)(NMe2) (R CH2Ph (2), CH2-
:
σ
)
{[
η 5
:
σ
}
σ
(
µ:σ
{[
η 5
:
}
(
µ:σ
:
σ
η
:
σ
η
2-C(NMe2)dN(2,6-Me2C6H3)] (8). Reaction of 4
′
η
:
σ
-Me2C(C5H4)(C2B10H10)]Ti(NMe2)[η2
-
t
t
d
′
)
)
Me, R′ ) 2,6-Me2C6H3 (11) or Bu (12)).
−N bond only in the absence of the Ti−
−
spectroscopic techniques and elemental analyses. Molecular structures of 2, 3, 6−8, and 10−12 were further confirmed
by single-crystal X-ray analyses.
Introduction
(C9H6)(C2B10H10)]Zr(NMe2)2 indicated that the unsaturated
molecules inserted exclusively into the Zr-N bond and the
Zr-C(cage) bond remained intact. Such a preference of the
Zr-N over Zr-C insertion was suggested to most likely be
governed by steric factors.4 This is a very rare example,5
because the insertion into M-N bonds would be possible
only if no alkyl substituents are present.6
On the other hand, [η5:σ-Me2C(C5H4)(C2B10H10)]2Zr was
reported to catalyze the polymerization of MMA (methyl
methacrylate) in the absence of any cocatalyst through the
action of the nucleophilic cage atom.7 Complexes [η5:σ-
Me2C(C5H4)(C2B10H10)]M(η5-C5Me5)Cl (M ) Ti, Zr) were
active catalysts for ethylene polymerization in the presence
Our previous work showed that group 4 metal complexes
of the types [η5:σ-Me2A(C5H4)(C2B10H10)]M(NR2)2, [η:5σ-
Me2A(C9H6)(C2B10H10)]M(NR2)2,1 and [η5:σ-iPr2NA′(C9H6)-
(C2B10H10)]M(NR2)22 (A ) C, Si; A′ ) B, P; M ) group 4
metals; R ) Me, Et) were active catalysts for ethylene
polymerization upon activation with MAO (methylalumox-
+
ane).3 The active species were suggested to be L2MCH3
(L2 ) linked cyclopentadienyl-carboranyl ligands) cations
containing both M-C(cage) and M-CH3 bonds. A question
subsequently arises as to whether the M-C(cage) bond is
active in polymerization. Reactivity studies on [η5:σ-Me2C-
* To whom correspondence should be addressed. Fax: (852) 26035057.
Tel: (852) 26096269. E-mail: zxie@cuhk.edu.hk.
(1) Wang, H.; Wang, Y.; Li, H.-W.; Xie, Z.Organometallics 2001, 20,
5110.
(2) (a) Zi, G.; Li, H.-W.; Xie, Z. Organometallics 2002, 21, 3850. (b)
Wang, H.; Chan, H.-S.; Okuda, J.; Xie, Z. Organometallics 2005, 24,
3118.
(6) (a) Sanchez-Nieves, J.; Royo, P.; Pellinghelli, M. A.; Tiripicchio, A.
Organometallics 2000, 19, 3161. (b) Thirupathi, N.; Yap, G. P. A.;
Richeson, D. S. Organometallics 2000, 19, 2573. (c) Broder, C. K.;
Goeta, A. E.; Howard, J. A. K.; Hughes, A. K.; Johnson, A. L.; Malget,
J. M.; Wade, K. J. Chem. Soc., Dalton Trans. 2000, 3526. (d) Wu, Z.
Z.; Diminnie, J. B.; Xue, Z. L. Organometallics 1999, 18, 1002. (e)
Zanella, P.; Brianese, N.; Casellato, U.; Ossola, F.; Porchia, M.;
Rossetto, G.; Graziani, R. J. Chem. Soc., Dalton Trans. 1987, 2039.
(f) Chisholm, M. H.; Hammond, C. E.; Ho, D.; Huffman, J. C. J. Am.
Chem. Soc. 1986, 108, 7860. (g) Cano, J.; Sudupe, M.; Royo, P.;
Mosquera, M. E. G. Organometallics 2005, 24, 2424.
(3) Xie, Z. Coord. Chem. ReV. 2006, 250, 259.
(4) Wang, H.; Li, H.-W.; Xie, Z. Organometallics 2003, 22, 4522.
(5) For another example of a preference for insertion into the M-N bond,
see: Amor, F.; Sa´nchez-Nieves, J.; Royo, P.; Jacobsen, H.; Blacque,
O.; Berke, H.; Lanfranchi, M.; Pellinghelli, M. A.; Tiripicchio, A.
Eur. J. Inorg. Chem. 2002, 2810.
(7) Hong, E.; Kim, Y.; Do, Y. Organometallics 1998, 17, 2933.
10.1021/ic0604664 CCC: $33.50
Published on Web 06/08/2006
© 2006 American Chemical Society
Inorganic Chemistry, Vol. 45, No. 14, 2006 5675

Wang et al.
6.08 (m, 1H, C5H4), 5.39 (m, 1H, C5H4), 5.25 (m, 2H, C5H4), 3.04
(s, 6H, N(CH3)2), 2.42 (d, 2J ) 8.5 Hz, 1H, CH2C6H5), 2.10 (d, 2J
) 8.5 Hz, 1H, CH2C6H5), 1.27 (s, 3H, (CH3)2C), 1.17 (s, 3H,
(CH3)2C). 13C NMR (benzene-d6): δ 150.3, 148.7, 129.6, 129.4,
126.0, 125.2 (CH2C6H5), 123.3, 118.9, 118.7, 115.0, 113.1 (C5H4),
102.5, 92.4 (cage C), 66.2 (CH2C6H5), 47.5 (N(CH3)2), 42.6, 32.1,
31.6 ((CH3)2C). 11B NMR (benzene-d6): δ -3.2 (2B), -6.4 (2B),
-9.8 (4B), -12.9 (2B). IR (KBr, cm-1): ν 2589 (s) (BH). Anal.
Calcd for C19H33B10NTi: C, 52.89; H, 7.71; N, 3.25. Found: C,
52.60; H, 7.71; N, 3.50.
of MMAO (modified methylalumoxane). Possible involve-
ment of the activation of the M-C(cage) σ bond was
suggested.8
The above results prompted us to investigate the relative
reactivity of M-C(alkyl), M-C(cage), and M-N bonds
toward unsaturated molecules. The most convenient route
for preparing such a model complex containing four different
ligands is to convert one of the NMe2 groups in [η5:σ-Me2C-
(C5H4)(C2B10H10)]M(NMe2)2 into an alkyl unit. Controlled
methylation9 or chlorination1 of zirconium amides was not
successful using Me3Al or Me3SiCl as reagents. For the
smaller Ti analogue, however, controlled chlorination was
achieved. [η5:σ-Me2C(C5H4)(C2B10H10)]TiCl(NMe2) was con-
veniently prepared in 65% yield by treatment of [η5:σ-Me2C-
(C5H4)(C2B10H10)]Ti(NMe2)2 with excess Me3SiCl in tolu-
ene.1 This was subsequently converted into its alkyl derivatives,
which offered a unique opportunity to observe the direct
competition among Ti-C(alkyl), Ti-N, and Ti-C(cage)
bonds in the migratory insertion with unsaturated molecules.
The Ti-alkyl complexes were thermally unstable, leading
to the formation of interesting dinuclear species. We report
in this article the synthesis, structural characterization,
thermal stability, and reactivity of [η5:σ-Me2C(C5H4)-
(C2B10H10)]TiR(NMe2).
Preparation of {[η5:σ-Me2C(C5H4)(C2B10H10)]Ti}2(µ-NMe)-
(µ:σ-NMeCH2)‚2C6H5CH3 (3‚2C6H5CH3). A 1.6 M solution of
n-BuLi in hexane (0.4 mL, 0.6 mmol) was slowly added to a THF
(15 mL) solution of 1 (226 mg, 0.6 mmol) at -78 °C. The reaction
mixture was slowly warmed to room temperature and stirred for 3
h. The color of the solution changed gradually from red to dark
blue. After the solvents were removed, the residue was extracted
with toluene (10 mL × 3). The toluene solutions were combined
and concentrated to about 5 mL. Complex 3 was isolated as dark
red crystals after this dark blue solution stood at room temperature
for 3 days (188 mg, 37%). 1H NMR (benzene-d6): δ 7.13 (m, 4H,
CH3C6H5), 7.02 (m, 6H, CH3C6H5), 6.67 (m, 2H, C5H4), 6.58 (m,
2H, C5H4), 6.23 (m, 2H, C5H4), 5.17 (m, 2H, C5H4), 3.54 (br s,
2
2
6H, NCH3), 3.02 (d, J ) 7.0 Hz, 1H, NCH2), 2.19 (d, J ) 7.0
Hz, 1H, NCH2), 2.01 (s, 6H, CH3C6H5), 1.41 (s, 6H, (CH3)2C),
1.21 (s, 6H, (CH3)2C). 13C NMR (benzene-d6): δ 137.9, 129.3,
125.6 (CH3C6H5), 120.1, 115.2, 113.3, 112.5, 111.2 (C5H4), 67.9
(NCH3), 65.9 (NCH2), 31.9, 25.8, 23.0 ((CH3)2C), 21.4 (CH3C6H5);
the cage carbons were not observed. 11B NMR (benzene-d6): δ
-3.7 (2B), -4.2 (2B), -6.6 (2B), -9.0 (4B), -11.1 (4B), -13.3
(6B). IR (KBr, cm-1): ν 2565 (s) (BH). Anal. Calcd for
C30H57B20N2Ti2 (3 + toluene): C, 47.55; H, 7.58; N, 3.70. Found:
C, 47.40; H, 7.30; N, 3.50.
Experimental Section
General Procedures. All experiments were performed under an
atmosphere of dry dinitrogen with the rigid exclusion of air and
moisture using standard Schlenk or cannula techniques, or in a
glovebox. All organic solvents were freshly distilled from sodium
benzophenone ketyl immediately prior to use. [η5:σ-Me2C(C5H4)-
(C2B10H10)]TiCl(NMe2) (1)1 and PhCH2K10 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 Perkin-Elmer 1600 Fourier transform spectrometer.
1H and 13C NMR spectra were recorded on a Bruker DPX 300
spectrometer at 300 and 75 MHz, respectively. 11B 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 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 Shanghai Institute of Organic Chemistry, CAS, China.
Preparation of [η5:σ-Me2C(C5H4)(C2B10H10)]Ti(CH2SiMe3)-
(NMe2) (4). A 1.0 M solution of Me3SiCH2Li in hexane (0.5 mL,
0.5 mmol) was added dropwise to a toluene (10 mL) solution of 1
(187 mg, 0.5 mmol) with stirring at -30 °C, and the mixture was
stirred at room temperature for 3 h. After the solvents were removed,
the residue was extracted with n-hexane (20 mL x 2). The n-hexane
solutions were combined and concentrated to about 10 mL.
Complex 4 was isolated as an orange solid after this solution stood
1
at -30 °C for 1 day (160 mg, 75%). H NMR (benzene-d6): δ
6.30 (m, 1H, C5H4), 6.02 (m, 1H, C5H4), 5.31 (m, 1H, C5H4), 5.26
2
(m, 1H, C5H4), 3.12 (s, 6H, N(CH3)2), 2.11 (d, J ) 9.0 Hz, 1H,
2
CH2Si(CH3)3), 1.74 (d, J ) 9.0 Hz, 1H, CH2Si(CH3)3), 1.35 (s,
3H, (CH3)2C), 1.23 (s, 3H, (CH3)2C), 0.11 (s, 9H, CH2Si(CH3)3).
13C NMR (benzene-d6): δ 147.8, 116.3, 114.3, 111.9, 111.3 (C5H4),
102.2, 90.9 (cage C), 65.8 (CH2Si(CH3)3), 47.6 (N(CH3)2), 42.1,
31.8, 31.7 ((CH3)2C), 2.80 (CH2Si(CH3)3). 11B NMR (benzene-
d6): δ -0.8 (2B), -4.1 (2B), -7.6 (4B), -10.7 (2B). IR (KBr,
cm-1): ν 2574 (vs) (BH). Anal. Calcd for C16H37B10NSiTi: C,
44.95; H, 8.72; N, 3.28. Found: C, 44.60; H, 8.81; N, 3.23.
Preparation of [η5:σ-Me2C(C5H4)(C2B10H10)]Ti(CH3)(NMe2)
(5). A 3.0 M solution of CH3MgBr in diethyl ether (0.33 mL, 1.0
mmol) was added dropwise to a toluene (15 mL) solution of 1 (375
mg, 1.0 mmol) with stirring at -30 °C, followed by the identical
procedure reported for 4 to give 5 as a yellow solid (213 mg, 60%).
1H NMR (benzene-d6): δ 6.25 (m, 1H, C5H4), 5.58 (m, 1H, C5H4),
5.29 (m, 1H, C5H4), 5.19 (m, 1H, C5H4), 3.03 (s, 6H, N(CH3)2),
1.33 (s, 3H, (CH3)2C), 1.22 (s, 3H, (CH3)2C), 0.71 (s, 3H, CH3).
13C NMR (benzene-d6): δ 147.3, 116.9, 113.6, 111.3, 109.7 (C5H4),
103.6, 102.1 (cage C), 47.6 (CH3), 45.7 (N(CH3)2), 42.2, 31.8, 31.3
((CH3)2C). 11B NMR (benzene-d6): δ -2.4 (2B), -6.1 (2B), -9.5
Preparation of [η5:σ-Me2C(C5H4)(C2B10H10)]Ti(CH2Ph)-
(NMe2) (2). A THF (10 mL) solution of PhCH2K (117 mg, 0.9
mmol) was added dropwise to a THF (10 mL) solution of 1 (337
mg, 0.9 mmol) at -78 °C. The reaction mixture was slowly warmed
to room temperature and stirred overnight. After the solvent was
removed, the residue was extracted with toluene (5 mL × 3). The
toluene solutions were combined and concentrated to about 5 mL
and n-hexane (5 mL) was added. Complex 2 was isolated as red
crystals after this solution stood at -30 °C for 3 days (210 mg,
1
54%). H NMR (benzene-d6): δ 7.10 (m, 2H, CH2C6H5), 6.90 (t,
J ) 7.2 Hz, 1H, CH2C6H5), 6.76 (d, J ) 7.2 Hz, 2H, CH2C6H5),
(8) Han, Y.; Hong, E.; Kim, Y.; Lee, M. H.; Kim, J.; Hwang, J.-W.; Do,
Y. J. Organomet. Chem. 2003, 679, 48.
(9) Wang, Y.; Wang, H.; Wang, H.; Chan, H.-S.; Xie, Z. J. Orgamomet.
Chem. 2003, 683, 39.
(10) Manfred, S.; Juergen. H. Angew. Chem., Int. Ed. 1973, 12, 508.
5676 Inorganic Chemistry, Vol. 45, No. 14, 2006

[η5:σ-Me2C(C5H4)(C2B10H10)]Ti(R)(NMe2)
(4B), -12.6 (2B). IR (KBr, cm-1): ν 2577 (s) (BH). Satisfactory
elemental analyses were not obtained because of the thermal
decomposition of 5 during shipment.
C6H3(CH3)2), 1.57 (s, 3H, (CH3)2C), 1.41 (s, 3H, (CH3)2C), -0.25
(s, 9H, CH
2Si(CH3)3). 13C NMR (benzene-d6): δ 244.2 (ArNd
CCH2Si(CH3)3), 144.8, 131.1, 129.1, 128.8, 128.0, 125.7 (C6H3-
(CH3)2), 148.0, 111.9, 110.0, 109.2, 107.6 (C5H4), 102.6 (cage C),
49.2 (CH2Si(CH3)3), 47.1 (N(CH3)2) 41.5, 32.5, 32.1 ((CH3)2C),
21.1, 18.9 (C6H3(CH3)2), -1.0 (CH2Si(CH3)3). 11B NMR (benzene-
d6): δ -2.8 (2B), -5.2 (3B), -8.8 (5B). IR (KBr, cm-1): ν 2585
(vs) (BH), 1562 (s) (CdN). Anal. Calcd for C25H46B10N2SiTi: C,
53.74; H, 8.30; N, 5.01. Found: C, 53.53; H, 8.35; N, 4.83.
Preparation of {[η5:σ-Me2C(C5H4)(C2B10H10)]Ti}2(µ-NMe2)-
(µ:σ-NMeCH2)‚2THF (6‚2THF). Complex 5 (177 mg, 0.5 mmol)
was dissolved in a warm toluene (15 mL). The color of the solution
turned from yellow to dark blue overnight. Removal of the solvents
gave a dark blue solid. Recrystallization from THF/toluene at room
temperature afforded 6‚2THF as dark green crystals (124 mg, 30%).
1H NMR (pyridine-d5): δ 3.57 (br s), 1.42 (br s) (THF), plus many
broad, unresolved peaks. 13C NMR (pyridine-d5): δ 65.2, 25.7
(THF), plus many broad, unresolved peaks. 11B NMR (pyridine-
d5): δ -2.7 (6B), -5.9 (6B), -9.2 (8B). IR (KBr, cm-1): ν 2584
(vs) (BH). Anal. Calcd for C32H67B20N2O2Ti2 (6 + 2THF): C,
46.65; H, 8.20; N, 3.40. Found: C, 46.32; H, 7.97; N, 3.54.
Preparation of [η5:σ-Me2C(C5H4)(C2B10H10)]Ti(Cl)[η2-OC-
(NMe2)NPh] (7). A toluene (10 mL) solution of phenyl isocyanate
(60 mg, 0.5 mmol) was added to a toluene (10 mL) solution of 1
(187 mg, 0.5 mmol) at 0 °C, and the mixture was stirred overnight
at room temperature. The precipitate was collected by filtration and
redissolved in hot THF (10 mL). Complex 7 was isolated as orange
crystals after this solution stood at room temperature for 3 days
Preparation of [η5:σ-Me2C(C5H4)(C2B10H10)]Ti(NMe2)[η2-
C(CH2SiMe3)dNtBu]‚2/3C6H5CH3 (10‚2/3 toluene). This com-
pound was prepared as orange crystals from the reaction of 4 (213
mg, 0.5 mmol) with t-butyl isocyanide (41 mg, 0.5 mmol) in toluene
(15 mL) using the same procedure reported for 9; yield: 134 mg
1
(47%). H NMR (benzene-d6): δ 7.05 (m, 3H, C6H5CH3), 6.00
(m, 1H, C5H4), 5.47 (m, 1H, C5H4), 5.23 (m, 1H, C5H4), 5.05 (m,
2
1H, C5H4), 3.23 (d, J ) 9.0 Hz, 1H, CH2Si(CH3)3), 3.16 (s, 6H,
2
N(CH3)2), 2.68 (d, J ) 9.0 Hz, 1H, CH2Si(CH3)3), 2.05 (s, 2H,
C6H5CH3), 1.56 (s, 3H, (CH3)2C), 1.49 (s, 3H, (CH3)2C), 0.95 (s,
9H, C(CH3)3), 0.11 (s, 9H, CH2Si(CH3)3). 13C NMR (benzene-d6):
δ 236.6 (tBuNdCCH2Si(CH3)3), 137.5, 129.5, 126.5, 124.5 (C6H5-
CH3), 150.3, 111.5, 108.3, 107.4, 103.9 (C5H4), 101.4 (cage C),
60.4 (C(CH3)3), 49.2 (CH2Si(CH3)3), 46.8 (N(CH3)2), 41.9, 32.9,
32.7 ((CH3)2C), 29.5 (C(CH3)3), 23.0 (C6H5CH3), 1.1 (CH2Si(CH3)3.
11B NMR (benzene-d6): δ -3.2 (2B), -5.9 (3B), -9.5 (3B), -10.8
(2B). IR (KBr, cm-1): ν 2574 (vs) (BH), 1622 (m) (CdN). Anal.
Calcd for C21H46B10N2SiTi (10): C, 49.39; H, 9.08; N, 5.49.
Found: C, 49.44; H, 8.91; N, 5.38.
1
(160 mg, 65%). H NMR (pyridine-d5): δ 7.42 (m, 2H, C6H5),
7.29 (t, J ) 6.9 Hz, 1H, C6H5), 7.03 (d, J ) 6.3 Hz, 2H, C6H5),
6.99 (m, 1H, C5H4), 6.79 (m, 1H, C5H4), 6.17 (m, 1H, C5H4), 5.99
(m, 1H, C5H4), 2.87 (s, 6H, N(CH3)2), 1.70 (s, 3H, (CH3)2C), 1.58
(s, 3H, (CH3)2C). 13C NMR (pyridine-d5): δ 165.9 (NCO), 146.2,
128.2, 128.0, 124.7, 123.6, 121.7 (C6H5), 154.9, 120.0, 117.2, 112.3
(C5H4), 102.8 (cage C), 42.3 (N(CH3)2), 35.7, 31.4, 31.3 ((CH3)2C).
11B NMR (pyridine-d5): δ -4.7 (2B), -8.3 (4B), -10.4 (4B). IR
(KBr, cm-1): ν 2576 (vs) (BH), 1596 (vs) (NCO). Anal. Calcd for
C19H31B10ClN2OTi: C, 46.11; H, 6.31; N, 5.66. Found: C, 46.45;
H, 6.13; N, 5.68.
Preparation of [η5:σ-Me2C(C5H4)(C2B10H10)]Ti(Cl)[η2-C(N-
Me2)dN(C6H3Me2-2,6)] (8). A toluene (10 mL) solution of 2,6-
dimethylphenyl isocyanide (66 mg, 0.5 mmol) was added to a
toluene (15 mL) solution of 1 (187 mg, 0.5 mmol) with stirring at
room temperature. The resulting solution was refluxed for 2 days
and then concentrated to about 10 mL. Complex 8 was isolated as
yellow crystals after this solution stood at room temperature for 1
day (152 mg, 60%). 1H NMR (benzene-d6): δ 6.80 (m, 3H, C6H3-
(CH3)2), 6.45 (m, 1H, C5H4), 5.98 (m, 1H, C5H4), 5.59 (m, 1H,
C5H4), 5.29 (m, 1H, C5H4), 2.99 (s, 3H, N(CH3)2), 1.95 (s, 3H,
N(CH3)2), 1.90 (s, 3H, C6H3(CH3)2), 1.66 (s, 3H, C6H3(CH3)2), 1.39
(s, 3H, (CH3)2C), 1.26 (s, 3H, (CH3)2C).13C NMR (benzene-d6): δ
206.8 (ArNdCN(CH3)2), 149.8, 132.6, 130.4, 126.9 (C6H3(CH3)2),
154.9, 118.3, 116.7, 113.5, 111.8 (C5H4), 108.3, 102.7 (cage C),
44.1, 36.9 (N(CH3)2), 41.7, 31.9, 31.4 ((CH3)2C), 18.9, 18.5 (C6H3-
(CH3)2). 11B NMR (benzene-d6): δ -4.1 (3B), -8.1 (2B), -10.6
(3B), -12.6 (1B), -13.9 (1B). IR (KBr, cm-1): ν 2569 (vs) (BH),
1622 (s) (CdN). Anal. Calcd for C21H35B10ClN2Ti: C, 49.75; H,
6.96; N, 5.53. Found: C, 49.51; H, 6.97; N, 5.46.
Preparation of [η5:σ-Me2C(C5H4)(C2B10H10)]Ti(NMe2)[η2-
C(CH3)dN(C6H3Me2-2,6)]‚C6H5CH3 (11‚toluene). This com-
pound was prepared as orange crystals from the reaction of 5 (177
mg, 0.5 mmol) with 2,6-dimethylphenyl isocyanide (66 mg, 0.5
mmol) in toluene (15 mL) using the same procedure reported for
1
9; yield: 202 mg (70%). H NMR (benzene-d6): δ 6.90 (m, 8H,
aromatic), 6.03 (m, 1H, C5H4), 5.54 (m, 1H, C5H4), 5.24 (m, 1H,
C5H4), 5.16 (m, 1H, C5H4), 2.81 (s, 6H, N(CH3)2), 2.05 (s, 3H,
C6H5CH3), 1.84 (s, 3H, CH3), 1.82 (s, 3H, C6H3(CH3)2), 1.65 (s,
3H, C6H3(CH3)2), 1.55 (s, 3H, (CH3)2C), 1.42 (s, 3H, (CH3)2C).
13C NMR (benzene-d6): δ 245.0 (ArNdCCH3), 149.6, 144.6, 131.1,
129.9, 129.2, 127.7, 126.5 (C6H3(CH3)2 + C6H5CH3), 111.8, 109.6,
107.5, 102.9, 101.8 (C5H4), 49.2 (N(CH3)2), 41.8, 32.5, 32.1
((CH3)2C), 22.3 (CH3), 22.2, 18.7 (C6H3(CH3)2 + C6H5CH3); the
cage carbons were not observed. 11B NMR (benzene-d6): δ -2.9
(2B), -5.6 (2B), -9.2 (4B), -10.9 (2B). IR (KBr, cm-1): ν 2584
(vs) (BH), 1597 (s) (CdN). Anal. Calcd for C29H46B10N2Ti (11 +
toluene): C, 60.19; H, 8.01; N, 4.84. Found: C, 60.36; H, 7.96;
N, 4.81.
Preparation of [η5:σ-Me2C(C5H4)(C2B10H10)]Ti(NMe2)[η2-
C(CH3)dNtBu] (12). This compound was prepared as orange
crystals from the reaction of 5 (177 mg, 0.5 mmol) with t-butyl
isocyanide (41 mg, 0.5 mmol) in toluene (15 mL) using the same
procedure reported for 9; yield: 142 mg (65%). 1H NMR (benzene-
d6): δ 5.91 (m, 1H, C5H4), 5.47 (m, 1H, C5H4), 4.84 (m, 1H, C5H4),
4.80 (m, 1H, C5H4), 2.99 (s, 6H, N(CH3)2), 2.34 (s, 3H, CH3), 1.50
(s, 3H, (CH3)2C), 1.41 (s, 3H, (CH3)2C), 0.88 (s, 9H, C(CH3)3).
13C NMR (benzene-d6): δ 238.9 (tBuNdCCH3), 150.6, 110.8,
108.9, 107.1, 102.9 (C5H4), 103.3, 100.8 (cage C), 60.5 (C(CH3)3),
51.9 (N(CH3)2), 42.1, 33.1, 31.4 ((CH3)2C), 28.7 (C(CH3)3), 19.5
(CH3). 11B NMR (benzene-d6): δ -3.6 (2B), -5.6 (1B), -6.5 (1B),
-9.8 (5B), -11.7 (1B). IR (KBr, cm-1): ν 2572 (vs) (BH), 1635
(m) (CdN). Anal. Calcd for C18H38B10N2Ti: C, 49.30; H, 8.73;
N, 6.39. Found: C, 49.32; H, 8.63; N, 6.27.
Preparation of [η5:σ-Me2C(C5H4)(C2B10H10)]Ti(NMe2)[η2-
C(CH2SiMe3)dN(C6H3Me2-2,6)] (9). A toluene (10 mL) solution
of 2,6-dimethylphenyl isocyanide (66 mg, 0.5 mmol) was slowly
added to a toluene (10 mL) solution of 4 (213 mg, 0.5 mmol) at 0
°C. The resulting solution was stirred at room temperature for 6 h
and then concentrated to 10 mL. The clear solution stood at -30
1
°C for 2 days to afford 9 as a yellow solid (173 mg, 62%). H
NMR (benzene-d6): δ 7.00 (m, 3H, C6H3(CH3)2), 6.11 (m, 1H,
C5H4), 5.51 (m, 2H, C5H4), 5.03 (m, 1H, C5H4), 2.85 (s, 6H,
2
N(CH3)2), 2.55 (d, J ) 9.0 Hz, 1H, CH2Si(CH3)3), 2.11 (s, 3H,
C6H3(CH3)2), 1.85 (d, 2J ) 9.0 Hz, 1H, CH2Si(CH3)3), 1.62 (s, 3H,
Inorganic Chemistry, Vol. 45, No. 14, 2006 5677

Wang et al.
Table 1. Crystal Data and Summary of Data Collection and
Refinement for 2, 3, 6, and 7
Table 2. Crystal Data and Summary of Data Collection and
Refinement for 8 and 10-12
2
3‚2C6H5CH3
6‚2THF
7
8
10‚2/3C6H5CH3 11‚C6H5CH3
12
formula
C
19H33B10NTi C37H64B20N2-
C
32H67B20N2-
C
19H31B10ClN2-
formula
C
21H35B10
ClN2Ti
cryst size (mm) 0.30 × 0.20 0.40 × 0.30
-
C
77H154B30
-
C
29H46B10N2-
Ti
C
18H38B10N2-
Ti
Ti2
O2Ti2
OTi
N6Si3Ti3
cryst size
(mm3)
fw
cryst syst
space group
a (Å)
0.50 × 0.30
× 0.20
0.80 × 0.30 0.60 × 0.50 0.40 × 0.30
× 0.20 × 0.30 × 0.20
848.9 823.9 494.9
monoclinic
P21/n
20.823(3)
11.980(2)
21.382(3)
119.14(1)
4658.6(10)
4
0.20 × 0.15 0.30 × 0.20
× 0.10 × 0.10
578.7 438.5
monoclinic
P21
10.614(1)
19.818(2)
16.727(2)
90
106.87(1)
90
3367.1(5)
4
1.142
0.71073
2.5-50.0
0.277
× 0.10
506.9
monoclinic triclinic
× 0.20
431.5
fw
1716.3
monoclinic
P21/c
monoclinic
C2/c
monoclinic
P21/n
cryst syst
space group
a (Å)
b (Å)
c (Å)
monoclinic
P21/n
9.952(1)
12.559(1)
20.798(1)
90
102.80(1)
90
2534.7(3)
4
P21/c
P1h
23.563(5)
18.323(4)
17.636(4)
107.07(3)
7279.0(3)
12
16.862(1)
18.266(1)
15.437(1)
98.66(1)
4700.5(5)
4
14.314(1)
12,667(1)
14.937(1)
111.58(1)
2518.6(3)
4
14.167(1)
13.801(1)
13.747(1)
90
96.06(1)
90
15.436(1)
16.349(1)
21.805(2)
92.25(1)
108.67(1)
98.42(1)
5134.8(6)
2
b (Å)
c (Å)
â (deg)
V (Å3)
Z
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
D
calcd (Mg/m3) 1.181
1.210
1.164
1.305
2672.7(3)
4
λ, Mo KR (Å) 0.71073
0.71073
2.2-50.0
0.374
1776
8225
0.71073
4.0-50.0
0.372
1732
4144
0.71073
3.4-50.0
0.463
1024
3292
2θ range (deg) 2.9-51.3
D
calcd (Mg/m3) 1.260
1.110
1.149
µ (mm-1
F(000)
)
0.360
2712
5174
λ, Mo KR (Å) 0.71073
0.71073
2.0-50.0
0.304
1832
18006
0.71073
3.8-56.0
0.347
928
6097
2θ range (deg) 2.9-56.1
no. of obsd
reflns
no. of params 838
refined
GOF
R1
µ, mm-1
F(000)
no. of obsd
reflns
0.435
1056
6451
1224
9955
550
281
307
1.061
0.051
0.136
0.871
0.071
0.152
1.012
0.087
0.249
1.002
0.067
0.158
no. of params
refined
GOF
R1
wR2
316
1072
758
280
wR2
0.933
0.067
0.142
0.997
0.062
0.166
0.963
0.061
0.137
0.911
0.059
0.143
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 at 293 K on either a Bruker SMART
1000 CCD diffractometer using Mo-KR radiation for 3, 8, 10,
and 12 or an MSC/Rigaku RAXIS-IIC imaging plate using Mo-
KR radiation from a Rigaku rotating-anode X-ray generator
operating at 50 KV and 90 mA for 2, 6, 7, and 11. An empirical
absorption correction was applied using the SADABS program11a
for CCD data or by correlation of symmetry-equivalent reflections
using the ABSCOR program for IP data.11b 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 the SHELXTL
program package.12a For the noncentrosymmetric structure of 11,
the appropriate enantiomorph was chosen by refining Flack’s
parameter x toward zero.12b All hydrogen atoms were geometrically
fixed using the riding model. There were three crystallographically
independent molecules in the unit cells of 2 and 10 and two
independent molecules in the unit cell of 11. In addition, the
following solvated molecules were found in the unit cells of
different structures: two toluene molecules in 3, 10, and 11 and
two THF molecules in 6. Thus, each molecule of 10 shared two-
thirds of a toluene molecule in the unit cell. Crystal data and details
of data collection and structure refinements are given in Tables 1
and 2. Selected bond distances and angles are compiled in Table
3. Further details are included in the Supporting Information.
corresponding titanium alkyl complexes [η5:σ-Me2C(C5H4)-
(C2B10H10)]TiR(NMe2) (R ) CH2Ph (2), CH2SiMe3 (4), CH3
(5)) in good yields (Scheme 1). The H NMR spectra of 2,
1
4, and 5 showed the common features of several multiplets
of Cp protons, two singlets of the Me2C linkage protons,
and one singlet of the NMe2 group. In addition, two doublets
2
at 2.42 and 2.10 ppm with J ) 8.5 Hz assignable to the
methylene protons of the benzyl in 2, two doublets at 2.11
and 1.74 ppm with 2J ) 9.0 Hz attributable to the methylene
protons of the Ti-CH2SiMe3 in 4, and one singlet at 0.71
ppm corresponding to the Ti-Me methyl protons in 5 were
also observed in the 1H NMR spectra. Their 11B NMR spectra
all exhibited a 2:2:4:2 pattern.
The solid-state structure of 2 was confirmed by single-
crystal X-ray analyses. Its representative structure is shown
in Figure 1. The Ti atom is η5-bound to the five-membered
ring of the cyclopentadienyl and σ-bound to a carborane cage
carbon atom, an amido group, and a benzyl unit in a
distorted-tetrahedral geometry. The average Ti-C(benzyl)
distance of 2.106(2) Å and the Ti-C-C(aryl) angle of 129.1-
(3)° are close to the corresponding values of 2.134(1) Å and
127.2(7)° in (TCP)Ti(CH2Ph)2 (TCP ) tetramethylcyclo-
pentadienyl-4-methyl phenolate),13 2.162(1) Å and 124.3-
(1)° in {η5-C5H3-1,3-[SiMe2(η1-ΝtBu)]2}Ti(CH2Ph),14 and
2.147(5) Å in (Pri2-2,6-ArO)2Ti(η2-tBuNCCH2Ph)(CH2Ph).15
The average Ti-C(ring) distance of 2.349(3) Å, Ti-C(cage)
distance of 2.189(3) Å, and Ti-N(1) distance of 1.873(2) Å
are very comparable to the corresponding values of 2.341-
(2), 2.179(2), and 1.862(2) Å, respectively, observed in 11
Results
Alkylation of [η5:σ-Me2C(C5H4)(C2B10H10)]TiCl(NMe2).
Treatment of [η5:σ-Me2C(C5H4)(C2B10H10)]TiCl(NMe2) (1)
with 1 equiv of alkylating reagents such as PhCH2K, Me3-
SiCH2Li, and CH3MgBr resulted in the isolation of the
(11) (a) Sheldrick, G. M. SADABS: Program for Empirical Absorption
Correction of Area Detector Data. University of Go¨ttingen: Germany,
1996. (b) Higashi, T. ABSCOR - An Empirical Absorption Correction
Based on Fourier Coefficient Fitting; Rigaku Corp.: Tokyo, 1995.
(12) (a) Sheldrick, G. M. SHELXTL 5.10 for Windows NT: Structure
Determination Software Programs; Bruker Analytical X-ray systems,
Inc.: Madison, WI, 1997. (b) Flack, H. D. Acta Crystallogr., Sect. A
1983, 39, 876.
(13) Chen, Y.-X.; Fu, P.-F.; Stern, C.; Marks, T. J. Organometallics 1997,
16, 5958.
(14) Cano, J.; Royo, P.; Jacobsen, H.; Blacque, O.; Berke, H.; Herdtweck,
E. Eur. J. Inorg. Chem. 2003, 2463.
(15) Chamberlain, L. R.; Durfee, L. D.; Fanwick, P. E.; Kobriger, L.;
Latesky, S. L.; McMullen, A. K.; Rothwell, I. P.; Folting, K.; Huffman,
J. C.; Streib, W. E.; Wang, R. J. Am. Chem. Soc. 1987, 109, 390.
5678 Inorganic Chemistry, Vol. 45, No. 14, 2006

[η5:σ-Me2C(C5H4)(C2B10H10)]Ti(R)(NMe2)
Table 3. Selected Bond Distances (Å) and Angles (deg)
2a
3
6
7
8
10a
11a
12
avg Ti-C(ring)
Ti-C(cage)
Ti-C(alkyl)
Ti-Cl
Ti-N(NMe2)
Ti-N(CdN)
CdN
2.349(3)
2.189(3)
2.106(2)
2.343(1)
2.219(1)
2.169(1)
2.337(1)
2.254(1)
2.097(1)
2.344(5)
2.242(5)
2.376(5)
2.197(5)
2.370(1)
2.259(1)
2.392(1)
2.241(1)
2.366(4)
2.251(3)
2.256(2)
2.305(2)
1.873(2)
2.081(1)
2.131(1)
1.908(1)
2.044(1)
1.256(1)
1.868(1)
2.156(1)
1.278(1)
1.913(3)
2.033(3)
1.256(4)
2.086(4)
1.317(7)
1.955(4)
1.303(6)
C(ring)-C-C(cage)
109.2(3)
107.0
109.0(1)
105.8
108.8(1)
104.8
108.7(4)
103.6
108.6(4)
104.0
109.7(1)
104.0
108.8(3)
105.4
108.7(3)
104.0
cent-Ti-C(cage)b
a Average values of several crystallographically independent molecules in the unit cell. b cent ) the centroid of the five-membered ring of the
cyclopentadienyl.
Scheme 1
Figure 1. Molecular structure of [η5:σ-Me2C(C5H4)(C2B10H10)]Ti(CH2-
Ph)(NMe2) (2) (all hydrogen atoms are omitted for clarity).
Figure 2. Molecular structure of {[η5:σ-Me2C(C5H4)(C2B10H10)]Ti}2(µ-
NMe2)(µ:σ-NMeCH2) (6) (the solvated THF molecules, the second set of
the disordered C(11) and C(12) atoms, and all hydrogen atoms are omitted
for clarity).
Complex 6 is a centrosymmetric dinuclear molecule, in
which a crystallographically imposed C2 axis passes through
and those found in [η5:σ-Me2C(C5H4)(C2B10H10)]Ti(NR2)2.1,3
the N(1) and N(1′) atoms, thus prohibiting differentiation of
Compound 5 was not very thermally stable. Its toluene
the two Ti atoms. The C(11) and C(12) atoms are disordered
solution gradually turned from red to blue overnight at room
over two sets of positions with 0.5:0.5 occupancy. As shown
temperature, from which a dark blue solid was isolated. Re-
in Table 3, the average Ti-C(ring) distance of 2.337(1) Å
and Ti-C(cage) distance of 2.254(1) Å are very close to
those in 2. The Ti(1)-C(11) distance of 2.097(1) Å is
comparable to the corresponding values observed in other
azatitanacyclic complexes,17 for example, 2.150(2) Å in (Pri2-
2,6-ArO)2Ti[η2-tBuNC(CH2Ph)2],17a 2.262(3) Å in (Ph2-2,6-
ArO)2Ti(η2-tBuNCC4Et4),17b and 2.076(4) Å in CpTi[CpFe-
(η5-C5H3CH2NMe2)][CpFe{η5-C5H3CH2NCH2(Me)}].17c The
N-C distances (1.432(1)/1.450(1)/1.453(1) Å) are represen-
tative of single bond distances.17 The Ti‚‚‚Ti separation of
crystallization from THF gave dinuclear complex {[η5:σ-
Me2C(C5H4)(C2B10H10)]Ti}2(µ-NMe2)(µ:σ-NMeCH2)‚2T-
HF (6‚2THF) as dark green crystals in 30% yield (Scheme
1). It was a paramagnetic species, and the 1H and 13C NMR
did not give much useful information. Its 11B NMR spectrum
exhibited a 3:3:4 pattern. The green color and paramagnetic
nature of 6 suggested that it may contain Ti(III) ion.16 Its
molecular structure was ultimately established by single-
crystal X-ray diffraction study and is shown in Figure 2.
(16) For examples of dinuclear paramagnetic titanium(III) complexes,
see: (a) Hosmane, N. S.; Wang, Y.; Zhang, H.; Lu, K.-J.; Maguire, J.
A.; Gray, T. G.; Brooks, K. A.; Waldho¨r, E.; Kaim, W.; Kremer, R.
K. Organometallics 1997, 16, 1365. (b) Samuel, E.; Harrod, J. F.;
Gourier, D.; Dromzee, Y.; Robert, F.; Jeannin, Y. Inorg. Chem. 1992,
31, 3252.
(17) (a) Durfee, L. D.; Hill, J. E.; Fanwick, P. E.; Rothwell, I. P.
Organometallics 1990, 9, 75. (b) Hill, J. E.; Balaich, G.; Fanwick, P.
E.; Rothwell, I. P. Organometallics 1993, 12, 2911. (c) Hitchcock, P.
B.; Hughes, D. L.; Leigh, G. J.; Sanders, J. R.; de Souza, J. S. J.
Chem. Soc., Dalton Trans. 1999, 1161.
Inorganic Chemistry, Vol. 45, No. 14, 2006 5679

Wang et al.
Scheme 2
Figure 3. Molecular structure of {[η5:σ-Me2C(C5H4)(C2B10H10)]Ti}2(µ-
NMe)(µ:σ-NMeCH2) (3) (the solvated toluene molecules and all hydrogen
atoms are omitted for clarity).
2.898(1) Å can be compared to the 2.707(1) Å in {[(Me3-
Si)3C5H2]TiCl(µ-O)}2O,18a 2.931(3) Å in {[(Me3SiNCH2-
CH2)2NSiMe3]Ti(µ-H)}2,18b and 2.942(2) Å in [{CyNC(H)-
NCy}2Ti(µ-Cl)]2 (Cy ) cyclohexyl).18c In view of the
molecular structure of 6 and its dark green color and
paramagnetic nature,16 it is best described as a mixed-valence
Ti(IV)-Ti(III) dinuclear complex.
the Ti-N(amido) ones (1.981(1)/2.180(1) Å). The Ti(1)-
C(11) distance of 2.169(1) Å is very comparable to the
corresponding values observed in 6 and other azatitanacyclic
complexes.17 The N-C distances (1.403(1)-1.425(1) Å) fall
in the range 1.41-1.47 Å normally found in azatitanacyclic
complexes.17 The Ti‚‚‚Ti separation of 2.868(1) Å can be
compared to that of 2.898(1) Å observed in 6 and those
(2.707-2.942 Å) found in other dinuclear titanium com-
plexes.18
To gain some insight into the formation of 6, we carried
out the reaction of 1 with 1 equiv of n-BuLi under the same
reaction condition as that for 5. The results showed that the
color of the reaction mixture changed from red to dark blue
upon the reaction temperature being increased from -78 °C
to room temperature. These observations were the same as
those displayed by a toluene solution of 5 at room temper-
ature. From this dark blue solution, {[η5:σ-Me2C(C5H4)-
(C2B10H10)]Ti}2(µ-NMe)(µ:σ-NMeCH2)‚2C6H5CH3 (3‚2C6H5-
CH3) was isolated as dark red crystals in 37% yield (Scheme
1). Concentration of the mother liquor gave a dark blue solid,
The reaction pathways for the formation of 3 and 6 are
not clear. They may involve the intermediates [η5:σ-Me2C-
(C5H4)(C2B10H10)]TiR(NMe2), which undergo thermal de-
composition to generate 3, 6, and other unidentified species.
Reaction of [η5:σ-Me2C(C5H4)(C2B10H10)]Ti(Cl)(NMe2)
with PhNCO and RNC. Complex 1 contains both the Ti-
C(cage) and Ti-N bonds, which offers an opportunity to
study the relative activity of Ti-N/Ti-C(cage) bonds toward
unsaturated molecules. Reaction of 1 with 1 equiv of PhNCO
or 2,6-Me2C6H3NC gave the monoinsertion product [η5:σ-
Me2C(C5H4)(C2B10H10)]Ti(Cl)[η2-OC(NMe2)NPh] (7) in 65%
yield or [η5:σ-Me2C(C5H4)(C2B10H10)]Ti(Cl)[η2-C(NMe2)d
N(C6H3Me2-2,6)] (8) in 60% yield (Scheme 2). These results
showed that the unsaturated molecules inserted exclusively
into the Ti-N and the Ti-C(cage) bonds remained intact.
1
which was a paramagnetic species, as indicated by the H
NMR. Many attempts to isolate a pure species from the
mother liquor failed.
1
The H NMR of 3 confirmed its diamagnetic nature, in
which four multiplets in the range 5.17-6.67 ppm attribut-
able to the Cp protons, one broad singlet at 3.54 ppm
assignable to the methyl protons of the two NMe groups,
1
2
Their H NMR spectra all showed four multiplets corre-
two doublets at 3.02 and 2.19 ppm with J ) 7.0 Hz
sponding to the Cp protons and two singlets attributable to
the linkage Me2C unit. In contrast to the one singlet exhibited
by NMe2 group in the H NMR spectrum of 7, that of 8
corresponding to the methylene protons of the NCH2 unit,
and two singlets of the Me2C protons were observed. Its 11
NMR spectrum showed a 1:1:1:2:2:3 pattern.
B
1
showed two inequivalent methyl resonances at 2.99 and 1.95
ppm for the NMe2 group and two singlets for two methyl
groups on the phenyl ring due to the hindered rotation around
the C-N(CH3)2 and N-C(aryl) bonds. The unique NCO
resonance at 165.9 ppm and N-CdN resonance at 206.8
ppm were observed in the 13C NMR spectra of 7 and 8,
respectively.
Figure 4 shows the solid-state structure of complex 7. The
geometry of the [η5:σ-Me2C(C5H4)(C2B10H10)]Ti fragment
is almost identical with that observed in complex 1.1 The
structural parameters of the η2-OC(NMe2)NPh moiety indi-
cate some electron delocalization over the O(1)-C(21)-N(2)
atoms, which has been observed in [η5:σ-Me2Si(C9H6)-
(C2B10H10)]Zr[η2-OC(NMe2)NPh]2.4
The solid-state structure of 3 was further confirmed by
single-crystal X-ray analyses and is shown in Figure 3. It is
a dinuclear complex in which two Ti atoms have different
coordination environments. The structural motif of [η5:σ-
Me2C(C5H4)(C2B10H10)]Ti(η2-CH2NMe) found in 6 is also
observed in 3. Another bridging unit between the two Ti
atoms is the imido group NMe, rather than the amido group
NMe2 observed in 6. Therefore, the formal oxidation state
for both Ti atoms in 3 is +4. As expected, the Ti-N(imido)
distances (1.869(1)/1.949(1) Å) are generally shorter than
(18) (a) Okuda, J.; Herdtweck, E. Inorg. Chem. 1991, 30, 1516. (b) Love,
J. B.; Clark, H. C. S.; Cloke, F. G. N.; Green, J. C.; Hitchcock, P. B.
J. Am. Chem. Soc. 1999, 121, 6843. (c) Hao, S.; Feghali, K.;
Gambarotta, S. Inorg. Chem. 1997, 36, 1745.
5680 Inorganic Chemistry, Vol. 45, No. 14, 2006

[η5:σ-Me2C(C5H4)(C2B10H10)]Ti(R)(NMe2)
Scheme 3
Figure 4. Molecular structure of [η5:σ-Me2C(C5H4)(C2B10H10)]Ti(Cl)-
[η2-OC(NMe2)NPh] (7) (all hydrogen atoms are omitted for clarity).
2
and 2.55 in 9 and δ ) 2.68 and 3.23 in 10, with J ) 9.0
Hz, compared to those at δ ) 1.74 and 2.11 observed in
parent complex 4. The other notable characteristic of the
NMR spectra was the 13C chemical shift of the iminoacyl
carbon of the η2-(Me3SiCH2)CdNR′ group, δ ) 244.2 in 9
and 236.6 in 10. Unlike in 8, only one singlet of NMe2
1
resonance was observed in the H NMR spectra of both 9
and 10, suggesting that the Ti-N bond remained intact. In
addition, complexes 9 and 10 showed characteristic ν(Cd
N) stretching vibrations15,20 at about 1562 and 1622 cm-1 in
their solid-state IR spectra.
The isolation of 9 and 10 indicated that R′NC inserted
into the Ti-CH2SiMe3 bond rather than the Ti-N bond. To
explore the generality of these reactions, we also examined
the reactivity of [η5:σ-Me2C(C5H4)(C2B10H10)]Ti(CH3)-
(NMe2) (5). Treatment of 5 with 1 equiv of R′NC at room
temperature gave the monoinsertion products [η5:σ-Me2C-
(C5H4)(C2B10H10)]Ti(NMe2)[η2-CMedN(R′)] (R′ ) 2,6-
Figure 5. Molecular structure of [η5:σ-Me2C(C5H4)(C2B10H10)]Ti(Cl)-
[η2-C(NMe2)dN(C6H3Me2-2,6)] (8) (all hydrogen atoms are omitted for
clarity).
The molecular structure of 8 is shown in Figure 5. The
average Ti-C(ring), Ti-C(cage), and Ti-Cl distances are
similar to those observed in 7, as indicated in Table 3. The
Ti-C(29) and Ti-N(1) distances (2.061(5) and 1.995(4) Å,
respectively) are comparable to the reported Ti-C(sp2) and
Ti-N(sp2) bond lengths,15,19 which indicates that the imi-
nocarbamoyl ligand in 8 is coordinated to the metal center
in a η2 fashion. The very similar C(29)-N(1) (1.303(6) Å)
and C(29)-N(2) (1.318(6) Å) distances, together with the
planar geometry of the N(2) atom, reveal the delocalized
partial multiple bonds through the NdC-NMe2 fragment,
t
Me2C6H3 (11), Bu (12)) in about 65% yield (Scheme 3).
The spectroscopic characteristics found in 9 and 10 were all
observed in 11 and 12. These results again showed that R′NC
inserted exclusively into the Ti-CH3 bond.
The proton resonance of the methyl unit (δ ) 1.84 in 11
and δ ) 2.34 in 12) was downfield-shifted compared to their
precursor 5 (δ ) 0.71). The characteristic η2-iminoacyl
carbon resonance was found at 245.0 ppm for 11 and 238.9
ppm for 12. Complexes 11 and 12 showed characteristic
ν(CdN) stretching vibrations at about 1597 and 1635 cm-1.
The molecular structures of 10-12 were confirmed by
single-crystal X-ray analyses and are shown in Figures 6-8,
respectively. The Ti atom is η5-bound to the five-membered
ring of the cyclopentadienyl, σ-bound to a cage carbon atom
and a NMe2 group, and η2-bound to the iminoacyl group in
a distorted-tetrahedral geometry if the iminoacyl is taken as
occupying a single coordination site. Selected bond distances
and angles are compiled in Table 3, which are comparable
to the corresponding values reported for organotitanium
iminoacyl complexes.15,21,22 The molecular structures further
confirm the migration of a CH3 or CH2SiMe3 group from
the Ti atom to the RNC carbon atom, resulting in the
formation of titanium iminoacyl complexes with typical Cd
1
which is consistent with the H NMR results.
Reactions of [η5:σ-Me2C(C5H4)(C2B10H10)]TiR(NMe2)
with R′NC. The previous section showed that isocyanides
inserted exclusively into the Ti-N bond and that the Ti-
C(cage) bond remained intact. Complexes 4 and 5 offer a
unique opportunity to observe the direct competition between
alkyl and amido groups in the migration step. Treatment of
4 with 1 equiv of R′NC afforded the monoinsertion products
[η5:σ-Me2C(C5H4)(C2B10H10)]Ti(NMe2)[η2-C(CH2SiMe3)d
t
N(R′)] (R′ ) 2,6-Me2C6H3 (9), Bu (10)) in good yields
(Scheme 3). In the 1H NMR spectra, the insertion of
isocyanides into the Ti-CH2SiMe3 bond was found to result
in a downfield shift of the R-protons attached to the initial
alkyl complexes.15,19 The AB pattern for the methylene
protons of the CH2SiMe3 group was observed at δ ) 1.85
(20) Durfee, L. D.; Rothwell, I. P. Chem. ReV. 1988, 88, 1059.
(21) Thorn, M. G.; Fanwick, P. E.; Rothwell, I. P. Organometallics 1999,
18, 4442.
(22) Martins, A. M.; Ascenso, J. R.; de Azevedo, C. G.; Dias, A. R.; Duarte,
M. T.; da Silva, J. F.; Veiros, L. F.; Rodrigues, S. S. Organometallics
2003, 22, 4218.
(19) (a) Galakhov, M.; Go´mez-Sal, P.; Martin, A.; Mena, M.; Ye´lamos,
C. Eur. J. Inorg. Chem. 1998, 1319. (b) Chamberlain, L. R.; Durfee,
L. D.; Fanwick, P. E.; Kobriger, L. M.; Latesky, S. L.; McMullen, A.
K.; Steffey, B. D.; Rothwell, I. P.; Folting, K.; Huffman, J. C. J. Am.
Chem. Soc. 1987, 109, 6068.
Inorganic Chemistry, Vol. 45, No. 14, 2006 5681

Wang et al.
Scheme 4
insertions may be proceeded by the coordination of the
isocyanide and further migration of either the amido or alkyl
group to the electrophilic isocyanide carbon atom to form
the corresponding iminocarbamoyl or iminoacyl complexes.22
What factors control the migration? One argument is the
relative bond strengths. It has been documented that the
preference of Ti-C(alkyl) over Ti-N insertion is governed
by the relative bond strengths. The insertion into the weaker
Ti-C(alkyl) bond leads to a faster reaction and a more-stable
final product.22 In view of the similar Ti-C(cage) and Ti-
C(alkyl) distances (shown in Table 3) (i.e., both Ti-C bonds
have similar bond strengths), a question is why the Ti-
C(cage) bond is inert toward unsaturated molecules. One of
the reasons may be because of the low mobility and steric
bulkiness of the carboranyl unit.4,23 Another argument is
frontier orbital controlled insertion. It was used to explain
the direct insertion of 2.6-Me2C6H3NC into the Ta-NMe2
rather than the Ta-Me bond in (η5-C5Me5)Ta(dNtBu)-
(NMe2)Me.5 This argument is made on the basis of the attack
of the lone pair of the amido group in the HOMO (π-bonding
orbital) on the π* LUMO of the isocyanide molecules as
the major orbital transformation of the process (Scheme 4).
It may be a joint action of all factors mentioned above, which
results in the inertness of the Ti-C(cage) bond toward
unsaturated molecules.
Figure 6. Molecular structure of [η5:σ-Me2C(C5H4)(C2B10H10)]Ti(NMe2)[η2-
C(CH2SiMe3)dNtBu] (10) (the solvated toluene molecule and all hydrogen
atoms are omitted for clarity).
Figure 7. Molecular structure of [η5:σ-Me2C(C5H4)(C2B10H10)]Ti(NMe2)-
[η2-C(CH3)dN(C6H5Me2-2,6)] (11) (the solvated toluene molecule and all
hydrogen atoms are omitted for clarity).
Conclusion
The chloro ligand in [η5:σ-Me2C(C5H4)(C2B10H10)]TiCl-
(NMe2) (1) was easily substituted by alkyl groups via
alkylation reactions to give the corresponding chiral titanium
complexes. The thermal stability of these titanium alkyls is
dependent on the nature of the alkyl unit. For example,
titanium methyl complex 5 is isolable, whereas the titanium
butyl one is thermally very unstable. Both of the complexes
underwent thermal decomposition to give a mixture of
products from which two dinuclear titanium complexes were
isolated and structurally characterized.
Figure 8. Molecular structure of [η5:σ-Me2C(C5H4)(C2B10H10)]Ti(NMe2)-
[η2-C(CH3)dNtBu] (12) (all hydrogen atoms are omitted for clarity).
t
Reactions of R′NC (R′ ) Bu, 2,6-Me2C6H3) with [η5:σ-
N bond distances of 1.256(1) Å in 10, 1.278(1) Å in 11, and
1.256(4) Å in 12.
Me2C(C5H4)(C2B10H10)]TiCl(NMe2) or [η5:σ-Me2C(C5H4)-
(C2B10H10)]TiR(NMe2) (R ) Me, CH2SiMe3) were examined
in order to investigate the relative reactivity of Ti-C/Ti-N
bonds. The experimental results indicate that the insertion
of isocyanides into the Ti-C(alkyl) bond is preferred over
the Ti-N bond, whereas the Ti-C(cage) one remains intact
in all reactions although the bond strengths of the Ti-
Discussion
The above experimental results clearly show that the
unsaturated molecules insert into the Ti-N bond only in the
absence of the Ti-C(alkyl) bonds and that the Ti-C(cage)
bond remains intact, i.e., the relative reactivity follows the
trend: Ti-C(alkyl) > Ti-N > Ti-C(cage). The migratory
(23) Deng, L.; Chan, H.-S.; Xie, Z. J. Am. Chem. Soc. 2005, 127, 13774.
5682 Inorganic Chemistry, Vol. 45, No. 14, 2006

[η5:σ-Me2C(C5H4)(C2B10H10)]Ti(R)(NMe2)
C(alkyl) and Ti-C(cage) bonds are similar. The preferential
insertion of isocyanides into the Ti-C(alkyl) bond rather
than the Ti-N bond is governed by the relative bond
strengths of Ti-C and Ti-N. On the other hand, a joint
operation of steric factors and frontier orbital arguments may
result in the inertness of the Ti-C(cage) bond toward
unsaturated molecules.
Administration Region (Project 403103) and a Strategic
Investments Scheme administrated by The Chinese Univer-
sity of Hong Kong.
Supporting Information Available: Crystallographic data in
CIF format for 2, 3, 6-8, and 10-12. This material is available
free of charge via the Internet at http://pubs.acs.org.
Acknowledgment. This work was supported by a grant
IC0604664
from the Research Grants Council of The Hong Kong Special
Inorganic Chemistry, Vol. 45, No. 14, 2006 5683