Preparation and crystal structures of a series of titanium(III) 9-BBN hydroborate complexes containing Ti...H agostic interactions

Article abstract of DOI:10.1021/ic050422f

9-BBN hydroborate complexes Ti{(μ-H)₂BC₈H ₁₄}₃(THF)₂ (1), Ti{(μ-H)₂BC ₈H₁₄}₃(OEt₂) (2), and [K(OEt ₂)₄]-[Ti{(μ-H)₂BC₈H ₁₄}₄] (4) were formed from the reaction of TiCl ₄ with K[H₂BC₈H₁₄] in diethyl ether or THF. Ti{(μ-H)₂BC₈H₁₄} ₃(PhNH₂) (3) was isolated from the reaction of 2 with aniline in diethyl ether. In the formation of these complexes, Ti(IV) is reduced to Ti(III). The coordinated diethyl ether in 2 can be displaced by the stronger bases THF and aniline, to form 1 and 3, respectively. All of the compounds were characterized by single-crystal X-ray diffraction analysis. In complex 1, which contains two coordinated THF ligands, the titanium possesses a 17 electron configuration and there is no evidence for agostic interaction. Complexes 2 and 3 contain only one coordinated ether or aniline ligand, and the titanium possesses a 15 electron configuration. In these compounds, a C-H hydrogen on an α carbon on the BC₈H₁₄ unit of a 9-BBN hydroborate ligand forms an agostic interaction with the titanium. Criteria for assessing the existence of agostic interactions are discussed. As the potassium salt, the anion of complex 4 is more stable than the complexes 1-3. Organometallic anions of the type [ML₄]^- for titanium(III) are rare.

Full text of DOI:10.1021/ic050422f

Inorg. Chem. 2005, 44, 4871−4878
Preparation and Crystal Structures of a Series of Titanium(III) 9-BBN
Hydroborate Complexes Containing Ti‚‚‚H Agostic Interactions
Errun Ding, Bin Du, Fu-Chen Liu, Shengming Liu, Edward A. Meyers, and Sheldon G. Shore*
Department of Chemistry, The Ohio State UniVersity, Columbus, Ohio 43210
Received March 21, 2005
9-BBN hydroborate complexes Ti
[Ti -H)2BC8H14 4] (4) were formed from the reaction of TiCl4 with K[H2BC8H14] in diethyl ether or THF.
Ti -H)2BC8H14 3(PhNH2) (3) was isolated from the reaction of 2 with aniline in diethyl ether. In the formation of
{(µ-H)2BC8H14}3(THF)2 (1), Ti{(µ-H)2BC8H14}3(OEt2) (2), and [K(OEt2)4]-
{
(
µ
}
{
(µ
}
these complexes, Ti(IV) is reduced to Ti(III). The coordinated diethyl ether in 2 can be displaced by the stronger
bases THF and aniline, to form 1 and 3, respectively. All of the compounds were characterized by single-crystal
X-ray diffraction analysis. In complex 1, which contains two coordinated THF ligands, the titanium possesses a 17
electron configuration and there is no evidence for agostic interaction. Complexes 2 and 3 contain only one coordinated
ether or aniline ligand, and the titanium possesses a 15 electron configuration. In these compounds, a C
−H hydrogen
on an carbon on the BC8H14 unit of a 9-BBN hydroborate ligand forms an agostic interaction with the titanium.
R
Criteria for assessing the existence of agostic interactions are discussed. As the potassium salt, the anion of
complex 4 is more stable than the complexes 1
−
3. Organometallic anions of the type [ML4]- for titanium(III) are
rare.
Introduction
The molecular structure of Ti(BH4)3 has been determined
by analysis of electron diffraction data6 (Chart 1). This
Interest in transition-metal tetrahydroborate derivatives is
associated with their practical use in synthesis and catalysis
and as models for studying the bonding modes of hydrogen
bridges to metals.1,2 However, hydroborate derivatives of
Ti(III) are few in number, even though metal borohydrides
are known for almost all of the metals throughout the periodic
table.1,3 The first example of a titanium(III) borohydride
complex, [Ti(BH4)3], was reported by Hoekstra and Katz4
in 1949. No¨th reported syntheses of the similar complexes
[Ti(BH4)3Ln (L ) Et2O or THF; n ) 0-2)] in 1976.5
molecule contains three tridentate BH4 groups generating a
structure with C3V symmetry overall, implying 9-fold coor-
dination of the titanium atom and a planar TiB3 skeleton.
Some of the tetrahydroborate titanium compounds that have
been synthesized and characterized structurally by X-ray
(3) Selected papers for transition-metal tetrahydroborates: (a) Knizek, J.;
No¨th, H. J. Organomet. Chem. 2000, 614-615, 168. (b) Fischer, P.
J.; Young, J. V. G.; Ellis, J. E. Angew. Chem., Int. Ed. 2000, 39, 189.
(c) Hafid, A.; Nyassi, A.; Sitzmann, H.; Visseaux, M. Eur. J. Inorg.
Chem. 2000, 2333. (d) Ashworth, N. J.; Conway, S. L. J.; Green, J.
C.; Green, M. L. H. J. Organomet. Chem. 2000, 609, 83. (e) Conway,
S. L. J.; Doerrer, L. H.; Green, M. L. H.; Leech, M. A. Organometallics
2000, 19, 630. (f) Choukroun, R.; Douziech, B.; Dounnadieu, B.
Organometallics 1997, 16, 5517. (g) You, Y.; Wilson, S. R.; Girolami,
G. S. Organometallics 1994, 13, 4655. (h) Csa´sza´r, A.; Hedberg, L.;
Hedberg, K.; Burns, R. C.; Wen, A. T.; McGlinchey, M. J. Inorg.
Chem. 1991, 30, 1371. (i) Jensen, J. A.; Wilson, S. R.; Girolamil, G.
S. J. Am. Soc. Chem. 1988, 110, 4977. (j) Jensen, J. A.; Wilson, S.
R.; Schultz, A. J.; Girolami, G. S. J. Am. Chem. Soc. 1987, 109, 8094.
(k) Broach, R. W.; Chuang, I.; Marks, T. J.; Williams, J. M. Inorg.
Chem. 1983, 22, 1081. (l) Marks, T. J.; Shimp, L. A. Inorg. Chem.
1972, 11, 1542. (m) Plato, V.; Hedberg, K. Inorg. Chem. 1971, 10,
590. (n) Bird, P. H.; Churchill, M. R. Chem. Commun. 1967, 403.
(4) Hoekstra, H. R.; Katz, J. J. J. Am. Chem. Soc. 1949, 71, 2488.
(5) Franz, H. R.; Fusstetter, H.; No¨th, H. Z. Allorg. Chem. Chem. 1976,
427, 97.
* Author to whom correspondence should be addressed. E-mail: shore@
chemistry.ohio-state.edu.
(1) Reviews for transition-metal tetrahydroborates: (a) Markhaev, V. D.
Russ. Chem. ReV. 2000, 69, 727. (b) Bau, R.; Drabnin, M. H. Inorg.
Chim. Acta 1997, 259, 27. (c) Ephritikhine, M. Chem. ReV. 1997, 97,
2193. (d) Xu, Z.; Lin, Z. Coord. Chem. ReV. 1996, 156, 139. (e) Barton,
L.; Srivastava, D. K. In ComprehesiVe Organometallic Chemistry;
Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon Press
Inc.: New York, 1995; pp 275-372. (f) Gilbert, K. B.; Boocock, S.
K.; Shore, S. G. In ComprehesiVe Organometallic Chemistry; Wilkin-
son, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon Press Inc.:
New York, 1982; pp 879-945. (g) Teller, R. G.; Bau, R. Struct.
Bonding 1981, 44, 1. (h) Marks, T. J.; Kolb, J. R. Chem. ReV. 1977,
77, 263. (i) James, B. D.; Wallbridge, M. G. H. Prog. Inorg. Chem.
1970, 11, 99.
(2) (a) Corazza, F.; Florian, C.; Chiesi-Villa, A.; Guastini, C. Inorg. Chem.
1991, 30, 145. (b) Luetkens, M. L.; Huffman, J. C.; Sattelberger, A.
P. J. Am. Chem. Soc. 1985, 107, 3361. (c) Jensen, J. A.; Gerolami, G.
S. J. Chem. Soc., Chem. Commun. 1986, 1160.
(6) (a) Dain, C. J.; Downs, A. J.; Goode, M. J.; Evans, D. G.; Nicholls,
K. T.; Rankin, D. W. H.; Robertson, H. E. J. Chem. Soc., Dalton
Trans. 1991, 967. (b) Dain, C. J.; Downs, A. J.; Rankin, D. W. H.
Angew. Chem., Int. Ed. Engl. 1982, 21, 534.
10.1021/ic050422f CCC: $30.25
Published on Web 06/02/2005
© 2005 American Chemical Society
Inorganic Chemistry, Vol. 44, No. 13, 2005 4871

Ding et al.
Chart 1
can be important for organic, catalytic, and polymeric
chemistry.13
Results and Discussion
I. Formation and Properties of Ti{(µ-H)2BC8H14}3-
(THF)2(1),Ti{(µ-H)2BC8H14}3(OEt2)(2),Ti{(µ-H)2BC8H14}3-
(PhNH2) (3), and [K(OEt2)4][Ti{(µ-H)2BC8H14}4] (4). We
attempted to prepare the 9-BBN hydroborate complex Ti-
{(µ-H)2BC8H14}3 analagous to Ti(BH4)3. Since the 9-BBN
hydroborate anion is only a bidentate ligand with respect to
the formation of Ti-H-B bonds, it was of interest to
determine to what extent the formation of C-H‚‚‚Ti agostic
interactions would compensate for the absence of additional
B-H hydrogen to bind to Ti(III). Our attempts failed.
Apparently, reaction of TiCl3 with K[H2BC8H14] in toluene
does not occur to any significant extent because the solubili-
ties of both reactants are poor. When the coordinating
solvents THF and diethyl ether were employed, the com-
plexes Ti{(µ-H)2BC8H14}3(THF)2 (1) and Ti{(µ-H)2BC8H14}3-
(OEt2) (2) were obtained in 40% and 42% yields from the
reaction of TiCl4 with 4 mol of K[H2BC8H14] in diethyl ether
and THF, respectively (reactions 1 and 2). During the course
of these reactions, the anion [H2BC8H14]- functions as a
bidentate ligand as well as a reducing agent to convert
Ti(IV) to Ti(III). It in turn is oxidized to form a 9-BBN
diffraction are the following: Ti(II), Ti(η2-BH4)2(dmpe)2,3j
Cp*Ti(η2-BH4)((η2-(Me2PCH2)3Si(t-Bu)3g; Ti(III), Ti((η2-
BH4)3(PMe3)2,3i Cp2Ti(η2-BH4)7 More recently, Ellis reported
the first zerovalent titanium borohydride complex, [Ti(CO)4-
(η2-BH4)]-.3b
This laboratory has prepared three classes of organohy-
droborates (five-membered ring, [(µ-H)2BC4H8]-, six-
membered ring, [(µ-H)2BC5H10]-, and 9-BBN, [(µ-H)2-
BC8H14]- ligands) bound to group 4 and group 5 metal
mono(cyclopentadienyl)9 and bis(cyclopentadienyl)10 units
such as Cp*Zr{(µ-H)2BR}3, Cp*Zr(Cl){(µ-H)2BC8H14}2, and
Cp2Ti{(µ-H)2BR}2 (where Cp* ) C5H5 and C5(CH3)5; BR
) BC5H10 and BC8H14). In our continuing studies of
organohydroborate derivatives, we focus here on the prepara-
tion and molecular structures of titanium organohydroborate
complexes that do not contain the cyclopentadienide ligand.
In two of these complexes, R-C-H hydrogens on the BC8H14
unit of the 9-BBN hydroborate ligand form an agostic
interaction with the central titanium metal in the solid state.
Even though organometallic compounds exhibiting agostic
C-H‚‚‚M interactions are known for most d-group elements
including Ti(IV), few complexes of Ti(III) have been
examined. Agostic interactions have attracted considerable
interest since they often lead to C-H activation,11,12 which
diborane, [(C8H14B)(µ-H)] (5), with evolution of H2 gas.
2
(7) Melmed, K. M.; Coucouvanis, D.; Lippard, S. J. Inorg. Chem. 1973,
12, 232.
(8) Herrmann, N. A.; Denk, M.; Scherer, W.; Klingan, F. R. J. Organomet.
Chem. 1993, 444, C21.
(9) Ding, E.; Liu, F.; Liu, S.; Meyers, E. A.; Shore, G. S. Inorg. Chem.
2002, 41, 5329.
(10) (a) Jordan, G. T.; Shore, S. G. Inorg. Chem. 1996, 35, 1087. (b) Jordan,
G. T.; Liu, F.-C.; Shore, S. G. Inorg. Chem. 1997, 36, 5597. (c) Liu,
F.-C.; Liu, J.; Shore, S. G. Inorg. Chem. 1998, 37, 3293. (d) Liu,
F.-C.; Liu, J.; Meyers, E. A.; Shore, S. G. Inorg. Chem. 1999, 38,
2169. (e) Liu, F.-C.; Liu, J.; Meyers, E. A.; Shore, S. G. Inorg. Chem.
1999, 38, 3228. (f) Liu, J.; Meyers, E. A.; Shore, S. G. Inorg. Chem.
1998, 37, 496. (g) Liu, F.-C.; Plecnik, C. E.; Liu, S.; Liu, J.; Meyers,
E. A.; Shore, S. G. J. Organomet. Chem. 2001, 627, 109. (h) Liu,
F.-C.; Liu, J.; Meyers, E. A.; Shore, S. G. J. Am. Chem. Soc. 2000,
122, 6106.
(11) For recent reviews of the agostic interactions, see: (a) Grubbs, R. H.;
Coates, G. W. Acc Chem. Res. 1996, 29, 85. (b) Brookhart, M.; Green,
M. L. H.; Wong, L.-L. Prog. Inorg. Chem. 1988, 36, 1. (c) Ginzhurg,
A. G. Russ. Chem. ReV. 1988, 57, 1175. (d) Brookhart, M.; Green,
M. L. H. J. Organomet. Chem. 1983, 250, 395.
(12) For recent molecular structures of group 4 complexes with hydrogen
interactions, see: (a) Tanski, J. M.; Parkin, G. Organometallics 2002,
21, 587. (b) Jia, L.; Zhao, J.; Ding, E.; Brennessel, W. W.; J. Chem.
Soc., Dalton Trans. 2002, 2608. (c) Sun, Y.; Metz, M.; Stern, C. L.;
Marks, T. J. Organometallics 2000, 19, 1625. (d) Keaton, R. J.;
Jayaratne, K. C.; Fettinger, J. C.; Sita L. R. J. Am. Chem. Soc. 2000,
122, 12909. (e) Chen, Y.-X.; Metz, M. V.; Li, L.; Stern, C. L.; Marks,
T. J. J. Am. Chem. Soc. 1998, 120, 6287. (f) Procopio, L. J.; Carroll,
P. J.; Berry, D. H. J. Am. Chem. Soc. 1994, 116, 177. (g) Fryzuk, M.
D.; Mao, S. S. H. J. Am. Chem. Soc. 1993, 115, 5336. (h) Yang, X.;
Stern, C. L.; Marks, T. J. J. Am. Chem. Soc. 1991, 113, 3623. (i)
Hyla-Kryspin, I.; Gleiter, R.; Kru¨ger, C.; Zwettler R.; Erker, G.
Organometallics 1990, 9, 517.
Complexes 1 and 2 are green solids that are stable at room
temperature in the absence of air. They are soluble in THF,
diethyl ether, and benzene but slowly decompose to [(C8H14B)-
(µ-H)]2 (5) and unidentified products in solution. Reactions
4872 Inorganic Chemistry, Vol. 44, No. 13, 2005

Titanium(III) 9-BBN Hydroborate Complexes
Scheme 1
of TiCl4 with K[H2BC8H14] in 1:2 and 1:3 mole ratios were
performed, but only complex 1 or 2 formed, depending upon
the solvent. The molecular structures, determined by single-
crystal X-ray analyses, clearly showed the presence of an
agostic interaction of one of the R-C-H hydrogens of a
9-BBN hydrobroate ligand with Ti(III) in complex 2. Such
an interaction appears to be absent in complex 1. In complex
1, Ti(III) is associated with 17 valence electrons. In complex
2 the Ti(III) is associated with 15 valence electrons from
the 9-BBN hydroborate and diethyl ether ligands while the
R-C-H hydrogen in the 9-BBN hydrobroate ligand contrib-
utes additional electron density. THF is a stronger Lewis
base than diethyl ether. It apparently provides sufficient
electron density to Ti(III) so that the interaction of Ti(III)
with the R-C-H hydrogen is not required. On the other hand,
the R-C-H interaction with Ti(III) in complex 2 suggests
that its electron-donating ability is competitive with that of
diethyl ether.
Ti(III) in compound 3. To compensate for the electron
deficiency created by replacement of two THF’s of 1 by one
aniline, an agostic interaction occurs between an R-C-H
hydrogen of 9-BBN hydroborate ligand with Ti(III). As
indicated above compounds with Ti(III) agostic interactions
are rare.14
The fact that tetrahydroborate derivatives of transition
metals have been successfully employed for the preparation
of hydrides by symmetrical cleavage of the hydrogen bridge
(Scheme 1)15 prompted us to attempt to obtain titanium hy-
drides for which a very high reactivity might be anticipated.
However, from the reaction of complex 1 or 2 with pure
aniline, we could not identify the product. After the reaction,
a dark green solid was present. It does not dissolve in aniline.
The dark green complex [K(OEt2)4][Ti{(µ-H)2BC8H14}4]
(4) was isolated from a diethyl ether reaction solution of
TiCl4 and K[H2BC8H14] in a 1:5 mole ratio (reaction 4). This
compound is soluble in THF, diethyl ether, and benzene.
Compared with complexes 1-3, complex 4 is more stable
as a solid at room temperature in the absence of air. The
anion of complex 4 appears to be the first example of a
Ti(III) bound to four (µ-H2) bridging ligands.
The reaction of complexes 1 and also 2 with aniline in
reaction ratios varying from 1 mol of complex/mol of aniline
up to 3 mol of aniline in diethyl ether, THF, and also toluene
produced the unanticipated product Ti{(µ-H)2BC8H14}3-
(PhNH2) (3) (reaction 3). Complex 3 is a dark green solid.
It is air- and moisture-sensitive but less thermally sensitive
than the diethyl ether and THF analogues.
11B NMR spectra of all of the Ti(III) complexes could
1
not be observed. The H NMR spectra were very broad
because of their proximity to the paramagnetic Ti(III) center.
Infrared spectra of all the organohydroborate complexes
reported here are similar. All of them show C-H stretches
from 2995 to 2836 cm-1. Extremely weak absorptions from
2654 to 2687 cm-1 are observed in the infrared spectra of 2
and 3, respectively. Although these absorptions are consistent
with the presence of agostic C-H‚‚‚Ti interactions,11 we
believe that they are probably due to a very small amount
of impurity because the bands are so weak, barely above
the baseline, plus the fact that 4 does not contain an agostic
interaction on the basis of X-ray single-crystal analysis.
II. Molecular Structures of Compounds 1-4. The solid-
state structures of complexes 1-4 were determined by single-
The formation of 3 is of interest for several reasons. First
of all, owing to the significant basicity of aniline, it is
surprising that it is does not cleave the hydrogen bridge of
the 9-BBN hydroborate ligand as expected.
Second, while two THF’s or Et2O have been displaced
by aniline from 1 and 2, only one aniline coordinates to
(13) For selected papers for chemistry reactions of group 4 complexes with
hydrogen agostic interactions, see: (a) Beswick, C. L.; Marks, T. J.
J. Am. Chem. Soc. 2000, 122, 10358. (b) Thorshaug, K.; Støvneng, J.
A.; Rytter, E. Macromolecules 2000, 33, 8136. (c) Beswick, C. L.;
Marks, T. J. Organometallics 1999, 18, 2410. (d) Moscardi, G.;
Piemontesi, F.; Resconi, L. Organometallics 1999, 18, 5264. (e)
Thorshaug, K.; Støvneng, J. A.; Rytter, E.; Ystenes, M. Macromol-
ecules 1998, 31, 7149. (f) Gleiter, R.; Hyla-Kryspin, I.; Niu, S.; Q.;
Erker, G. Organometallics 1993, 12, 3828. (g) Prosenc, M. H.; Janiak,
C.; Brintzinger, H. H. Organometallics 1992, 11, 4036. (h) Erker, G.;
Fro¨mberg, W.; Angermund, K.; Schlund, R.; Kru¨ger, C. J. Chem. Soc.,
Chem. Commun. 1986, 372.
(14) Troyanov, S. I.; Mach, K.; Varga, V. Organometallics 1993, 12, 3387.
(15) (a) James, J. D.; Nauda, R. K.; Wallbridge, M. G. H. J. Chem. Soc.,
Chem. Commun. 1966, 849. (b) Gozum, J. E.; Girolaini, G. S. J. Am.
Chem. Soc. 1991, 113, 3829. (c) Wolczanski, P. T.; Bercaw, J. H.
Organometallics 1982, 1, 793.
Inorganic Chemistry, Vol. 44, No. 13, 2005 4873

Ding et al.
Table 1. Crystallographic Data for Ti{(µ-H)2BC8H14}3(THF)2 (1), Ti{(µ-H)2BC8H14}3(OEt2) (2), Ti{(µ-H)2BC8H14}3(PhNH2) (3), and
[K(OEt2)4][Ti{(µ-H)2BC8H14}4] (4)
1
2
3
4
empirical formula
fw
cryst syst
space group
a, Å
C32H64B3O2Ti
561.16
monoclinic
C2/c
17.4241(2)
10.24600(10)
18.5408(2)
90
94.02
90
3301.91(6)
4
1.129
C28H58B3OTi
475.085
orthorhombic
Pbca
20.3535(10)
13.5503(10)
21.6302(10)
90
90
90
5965.5(6)
8
1.094
C60H110B6N2Ti2
1020.16
triclinic
C48H104B4KO4Ti
875.55
monoclinic
P21/n
10.88940(10)
21.3740(2)
24.0977(2)
90
92.82
90
5601.96(9)
4
1.038
P1h
11.0575(10)
11.0868(10)
26.5904(10)
96.897(10)
98.991(10)
107.892(10)
3014.6(4)
2
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
Z
F(calcd), g cm-3
T, K
1.124
150(2)
0.302
0.0419
200(2)
0.285
0.0365
0.0466
200(2)
0.304
0.0405
0.0798
200(2)
0.263
0.0756
0.0997
µ, mm-1
R1a [I > 2.0σ(I)]
wR2b (all data)
0.0645
a R1 ) Σ||Fo| - |Fc||/Σ|Fo|. b wR2 ) {Σw(Fo
Fc )2/Σw(Fo )2}1/2
.
2
-
2
2
Table 2. Bond Lengths (Å) and Angles (deg) for
Ti{(µ-H)2BC8H14}3(THF)2 (1)
Table 4. Bond Lengths (Å) and Angles (deg) for
Ti{(µ-H)2BC8H14}3(PhNH2) (3)
Ti(1)-N(11)
Ti(1)-B(12)
Ti(1)‚‚‚C(115)
Ti(1)-H(1C)
Ti(1)-H(1A)
Ti(1)-H(1F)
B(11)-H(1A)
B(12)-H(1C)
B(13)-H(1E)
C(115)-H(115)
2.2148(17) Ti(1)-B(11)
2.204(2)
2.386(2)
2.15(2)
1.791(19)
1.91(2)
1.87(2)
1.202(19)
1.17(2)
Ti-O(1)
2.1580(9) Ti-O(1A)
2.4337(15) Ti-B(10A)
2.1580(9)
2.4337(15)
1.843(17)
1.819(16)
1.237(16)
0.982(1)
2.414(2)
2.515(2)
1.831(19)
1.87(2)
1.830(19)
1.18(2)
1.243(18)
1.214(19)
1.00(2)
Ti(1)-B(13)
Ti(1)‚‚‚H(115)
Ti(1)-H(1E)
Ti(1)-H(1B)
Ti(1)-H(1D)
B(11)-H(1B)
B(12)-H(1D)
B(13)-H(1F)
Ti-B(10)
Ti-B(20)
Ti-H(2)
2.421(2)
Ti-H(1)
1.857(15) Ti-H(3)
1.197(17) B(10)-H(2)
1.240(16) C(11)-H(11A)
B(10)-H(1)
B(20)-H(3)
O(1)-Ti-O(1A)
O(1)-Ti-B(10A)
O(1A)-Ti-B(10A) 88.74(5)
151.55(5)
88.74(5)
O(1)-Ti-B(10)
O(1)-Ti-B(20)
83.29(5)
104.22(3)
1.217(19)
O(1A)-Ti-B(20) 104.22(3)
B(20)-Ti-B(10A) 106.41(4)
B(10)-Ti-B(10A) 147.18(8)
Ti-B(10)-C(15)
Ti-B(20)-C(25)
H(2)-Ti-H(3)
H(2)-B(10)-H(1)
Ti-B(10)-H(1)
O(1A)-Ti-B(10)
B(20)-Ti-B(10)
Ti-B(10)-C(11)
Ti-B(20)-C(21)
H(1)-Ti-H(3)
H(2)-Ti-H(1)
Ti-B(10)-H(2)
Ti-B(20)-H(3)
83.29(5)
106.41(4)
132.58(10)
125.61(9)
88.1(7)
57.8(7)
48.3(7)
48.3(8)
N-Ti-B(11)
N-Ti-B(13)
Ti(1)-B(11)-C(111) 170.74(16)
Ti(1)-B(12)-C(121) 131.48(14)
Ti(1)-B(13)-C(131) 127.53(15)
B(11)-Ti(1)-B(12)
H(1A)-Ti(1)-H(1B)
H(1C)-Ti(1)-H(1D)
H(1C)-B(12)-H(1D)
102.33(8)
111.28(7)
N-Ti-B(12)
B(11)-Ti(1)-B(13)
Ti(1)-B(11)-C(115)
85.83(7)
117.72(9)
80.26(12)
119.40(9)
125.61(9)
139.7(7)
94.5(11)
47.2(8)
Ti(1)-B(12)-C(125) 120.14(14)
Ti(1)-B(13)-C(135) 123.42(15)
130.29(8)
56.5(8)
58.1(9)
B(13)-Ti(1)-B(12)
H(1E)-Ti(1)-H(1F)
H(1A)-B(11)-H(1B)
H(1E)-B(13)-H(1F)
103.83(8)
59.7(8)
97.8(13)
95.7(13)
96.6(13)
Table 3. Bond Lengths (Å) and Angles (deg) for
Ti{(µ-H)2BC8H14}3(OEt2) (2)
Table 5. Bond Lengths (Å) and Angles (deg) for
[K(OEt2)4][Ti{(µ-H)2BC8H14}4] (4)
Ti(1)-O(1)
Ti(1)-B(2)
2.0912(13) Ti(1)-B(1)
2.417(2) Ti(1)-B(3)
2.217(2)
2.417(2)
Ti-B(10)
Ti-B(30)
Ti-H(1)
2.386(4) Ti-B(20)
2.398(4) Ti-B(40)
2.391(4)
Ti(1)-H(3B)
Ti(1)-H(1B)
Ti(1)-H(2B)
B(1)-H(1A)
B(2)-H(2A)
B(3)-H(3A)
Ti(1)‚‚‚C(15)
C(15)-H(15)
1.879(15) Ti(1)-H(3A)
1.856(16) Ti(1)-H(1A)
1.857(16) Ti(1)-H(2A)
1.176(17) B(1)-H(1B)
1.179(19) B(2)-H(2B)
1.222(17) B(3)-H(3B)
1.833(16)
1.895(18)
1.909(19)
1.180(18)
1.229(16)
1.212(16)
2.192(17)
2.389(4)
1.89(3)
1.85(3)
1.83(4)
1.83(4)
1.18(3)
1.25(3)
1.12(4)
1.19(4)
2.671(3)
2.765(4)
1.87(3)
1.83(4)
1.84(3)
1.89(3)
1.20(3)
1.21(4)
1.20(3)
1.26(4)
Ti-H(2)
Ti-H(3)
Ti-H(4)
Ti-H(5)
Ti-H(7)
Ti-H(6)
Ti-H(8)
B(10)-H(1)
B(20)-H(3)
B(30)-H(5)
B(40)-H(7)
K-O(60)
K-O(65)
B(10)-H(2)
B(20)-H(4)
B(30)-H(6)
B(40)-H(8)
2.561(2)
0.941(9)
Ti(1)‚‚‚H(15)
2.639(4) K-O(50)
O-Ti(1)-B(1)
O-Ti(1)-B(3)
Ti-B(1)-C(11)
Ti-B(2)-C(21)
Ti-B(3)-C(31)
B(1)-Ti(1)-B(3)
H(3B)-Ti(1)-H(3A) 57.2(7)
H(2B)-Ti(1)-H(2A) 58.5(7)
H(2B)-B(2)-H(2A) 99.7(12)
100.87(8)
99.28(7)
169.29(17)
108.45(17)
111.44(13)
126.60(9)
O-Ti(1)-B(2)
B(1)-Ti(1)-B(2)
Ti-B(1)-C(15)
Ti-B(2)-C(25)
Ti-B(3)-C(35)
B(2)-Ti(1)-B(3)
H(1B)-Ti(1)-H(1A) 55.9(7)
H(1B)-B(1)-H(1A) 96.5(12)
H(3B)-B(3)-H(3A) 93.7(11)
108.25(7)
2.686(4) K-O(55)
114.75(9)
82.13(13)
128.54(14)
140.74(15)
104.66(8)
B(10)-Ti-B(40)
B(40)-Ti-B(20)
113.75(14) B(10)-Ti-B(20)
98.83(14) B(10)-Ti-B(30)
116.91(14)
99.37(13)
Ti(1)-B(10)-C(11) 120.5(2)
Ti(1)-B(20)-C(21) 130.0(3)
Ti(1)-B(30)-C(31) 129.5(3)
Ti(1)-B(40)-C(41) 133.7(3)
B(40)-Ti-B(30)
Ti(1)-B(10)-C(15) 131.7(2)
Ti(1)-B(20)-C(25) 122.8(3)
Ti(1)-B(30)-C(35) 125.0(3)
Ti(1)-B(40)-C(45) 118.1(3)
114.87(14) B(20)-Ti-B(30)
114.04(15)
60.8(17)
59.9(16)
98(2)
H(1)-Ti-H(2)
58.3(14)
56.0(17)
101(2)
H(3)-Ti-H(4)
crystal X-ray diffraction analyses. Crystal data are given in
Table 1, and structures are shown in Figures 1-4, while
selected bond distances and angles are reported in Tables
2-5. Table 6 is a summary of Ti‚‚‚Hagostic distances and
Ti-CR-Câ and Ti-B-C angles and where appropriate
dihedral angles.
H(5)-Ti-H(6)
H(7)-Ti-H(8)
H(1)-B(10)-H(2)
H(5)-B(30)-H(6)
H(3)-B(20)-H(4)
H(7)-B(40)-H(8)
96(3)
99(2)
The molecular structure of 1 is shown in Figure 1. The
geometry around the titanium metal center is that of a
distorted trigonal bipyramid with three 9-BBN hydroborate
4874 Inorganic Chemistry, Vol. 44, No. 13, 2005

Titanium(III) 9-BBN Hydroborate Complexes
Figure 2. Molecular structure of Ti{(µ-H)2BC8H14}3(OEt2) (2).
Figure 1. Molecular structure of Ti{(µ-H)2BC8H14}3(THF)2 (1).
B(1)-C(11) (169.29(17)°), Ti-B(2)-C(21) (108.45(17)°),
Ti-B(2)-C(25) (128.54(14)°), Ti-B(3)-C(31) (111.44-
(13)°), and Ti-B(3)-C(35) (140.74(15)°), thereby providing
additional strong evidence for the interaction between the
titanium and H(15). The distorted tetrahedral geometry about
the titanium atom (B(1)-Ti-B(2) ) 114.75(9)°, B(1)-Ti-
B(3) ) 126.60(9)°, B(2)-Ti-B(3) ) 104.66(8)°, O-Ti-
B(1) ) 100.87(8)°, O-Ti-B(2) ) 108.25(7)°, O-Ti-B(3)
) 99.28(7)°) is defined by three 9-BBN hydroborate ligands
and one molecule of diethyl ether (Ti-O ) 2.0912(13) Å).
The average titanium bridge hydrogen bond lengths in 2 is
1.871 Å.
ligands defining the equatorial plane (B(20)-Ti-B(10A)
) 106.41(4)°, B(20)-Ti-B(10) ) 106.41(4)°, B(10)-Ti-
B(10A) ) 147.18(8)°). Two molecules of THF are in
the axial positions trans with respect to each other
(O(1)-Ti-O(1A) ) 151.55(5)°). The coordination geometry
3i
resembles that previously reported for Ti(BH4)3(PMe3)2 .
Complex 1 possesses crystallographically imposed 2-fold
symmetry with the axis passing through Ti and B(20). The
Ti‚‚‚B distances of this complex are very close to each other,
2.421(2) and 2.4337(15) Å. They are slightly longer than
those in a known Ti(III) tetrahydroborate complex: Cp2Ti-
(η2-BH4)7,16 (Ti‚‚‚B ) 2.37(1) Å). Because of the larger size
of Ti(III) versus Ti(IV), the Ti-B distance of complex 1 is
larger than those observed in Ti(IV) tetrahydroborate com-
plexes, [Me3CNCH2CH2NCMe3]Ti(Cl)(BH4)8 (Ti‚‚‚B )
2.175(4) Å) and [Me3CNCH2CH2NCMe3]Ti(BH4)28 (Ti‚‚‚B
) 2.304(3) Å and Ti‚‚‚B ) 2.175(3) Å) and they are shorter
in Ti(II) tetrahydroborate complexes, Cp*Ti(η2-BH4)[η2-
(Me2PCH2)3Si(t-Bu)]3j (Ti‚‚‚B ) 2.445(7) Å) and Ti(BBH4)2-
(dmpe)23j (Ti‚‚‚B ) 2.534(3) Å). The average titanium bridge
hydrogen distance in 1 is 1.840 Å. This is similar to the
corresponding titanium bridge hydrogen distance in the
titanium(III) derivative Cp2Ti(µ-H)2BC8H14}.17
Figure 2 presents the molecular structure of complex 2.
There is an interaction between the C-H hydrogen on one
of the 9-BBN hydroborate ligands and the titanium(III) metal
center. The distance of Ti‚‚‚H(15) is 2.192(17) Å, comparable
to the agostic hydrogen‚‚‚metal distances in known Ti(IV)
complexes.18,19 Compared with d0 transition metal complexes,
agostic hydrogen interactions with d1 transition metals are
rare. This interaction results in a Ti‚‚‚B(1) distance of 2.217-
(2) Å that it is significantly shorter than those of 2.417(2) Å
of Ti‚‚‚B(2) and 2.417(2) Å of Ti‚‚‚B(3), where an agostic
interaction is not involved. Furthermore, the Ti-B(1)-C(15)
angle of 82.13(13)° is much smaller than those angles Ti-
The molecular structure of 3 is shown in Figure 3.
Complex 3 is isostructural and isoelectronic with complex
2; the titanium center adopts a distorted tetrahedral stereo-
chemistry which is similar to that in complex 2 (N-Ti(1)-
B(11)
) 102.33(8)°, N-Ti(1)-B(12) ) 85.83(7)°,
N-Ti(1)-B(13) ) 111.28(7)°, B(11)-Ti(1)-B(13) ) 117.72-
(9)°, B(11)-Ti(1)-B(12) ) 130.29(8)°, B(13)-Ti(1)-B(12)
) 103.83(8)). Ti is bound by three 9-BBN hydroborate
ligands and one molecule of coordinated aniline (Ti(1)-N(1)
) 2.214(8) Å); the Ti-N distance is normal and compares
well with that of the other titanium borohydride complex
(18) Compounds with Ti(IV)-â-H agostic interactions: (a) Koga, N.;
Obara, S.; Morokuma, K.; J. Am. Chem. Soc. 1984, 106, 4625. (b)
Haaland, A.; Scherer, W.; Ruud, K.; McGrady, G. S.; Downs, A. J.;
Swang, O. J. Am. Chem. Soc. 1998, 120, 3762. (c) Scherer, W.;
Hieringer, W.; Spiegler, M.; Sirsch, P.; McGrady, G. S.; Downs, A.
J.; Haaland, A.; Pedersen, B. Chem. Commun. 1998, 2471. (d) Cotton,
F. A.; Petrukhina, M. A. Inorg. Chem. Commun. 1998, 1, 195. (e)
Scherer, W.; Priermeier, T.; Haaland, A.; Volden, H. V.; McGrady,
G. S.; Downs, A. J.; Boese, R.; Blaser, D. Organometallics 1998, 17,
4406. (f) Dawoodi, Z.; Green, M. L. H.; Mtetwa, V. S. B.; Prout, K.
J. Chem. Soc., Commun. 1982, 802. (g) Dawoodi, Z.; Green, M. L.
H.; Mtetwa, V. S. B.; Prout, K.; Schultz, A. J.; Williams, J. M.;
Koetzle, T. F.; J. Chem. Soc., Dalton. Trans. 1986, 1629. (h) Pupi, R.
M., Coalter, J. N.; Petersen, T. L. J. Organomet. Chem. 1995, 497,
17.
(19) Compounds with Ti(IV)-R-H agostic interactions: (a) Dias, A. R.;
Galvao, A. M.; Galvao, A. C.; J. Organomet. Chem. 2001, 632, 157.
(b) Cowley, A. H.; Hair, G. S.; McBurnett, B. G.; Jones, R. A. Chem.
Commun. 1999, 437. (c) Cuenca, T.; Flores, J. C.; Royo, P. Organo-
metallics 1992, 11, 777. (d) Mena, M.; Pellinghell, M. A.; Royo, P.;
Serrano, R.; Tiripicchio, A. J. Chem. Soc., Chem. Commun. 1986,
1118. (e) Dawoodi, Z.; Green, M. L. H.; Mtetwa, V. S. B.; Prout, K.
J. Chem. Soc., Chem. Commun. 1982, 1410.
(16) Mamaeva, G. I.; Hargittai, I.; Spiridonov, V. P. Inorg. Chim. Acta
1977, 25, L123.
(17) Ho, N. N.; Bau, R.; Plecnik, C.; Shore, S. G.; Wang, X.; Schultz, A.
J. J. Organomet. Chem. 2002, 654, 216.
Inorganic Chemistry, Vol. 44, No. 13, 2005 4875

Ding et al.
Figure 4. Molecular structure of the anion of [K(OEt2)4][Ti{(µ-
H)2BC8H14}4] (4).
Figure 3. Molecular structure of Ti{(µ-H)2BC8H14}3(PhNH2) (3).
20
[(Me2Si2N]Ti(py)2(BH4)2 (Ti(1)-N(1) ) 2.214(3) Å,
even of an aliphatic system, can act essentially as a “lone
pair” which can donate to suitable empty metal orbitals;
suitable metal centers are likely to be found for e16-electron
transition metal complexes”.18f Many examples of agostic
interactions are known,11 identified through X-ray and
neutron diffraction, infrared and NMR spectroscopy, and
also, where appropriate, ESR spectroscopy. Such interactions
have also been the subject of theoretical studies.18a-c
Agostic hydrogen-metal interactions can occur over a
continuum of distances. A question of practical value is when
can the approach of a C-H hydrogen to a transition metal
be called an agostic interaction on the basis of structural
evidence? To make an informed decision, we believe that
several criteria must be considered for the existence of an
agostic interaction. These could include a “short” metal-
hydrogen distance, a “short” metal---carbon distance, a
reduced bond angle M-C-C (M-B-C for complexes 2
and 3), and a reduced dihedral angle between the TiH2 and
H2B planes (for complexes 2 and 3) that arise from the C-H
hydrogen interacting with the unsaturated metal. (At a
dihedral angle of 180°, the R-C-H hydrogens of the 9-BBN
hydroborate ligand are farthest from the metal.) Furthermore,
since there is no absolute value for distance or angle, one
must compare these values with related structural features
in the molecule where an agostic interaction is unlikely.
These comparisons are made in the discussions concerned
with structural data given in Tables 2-6.
Ti(1)-N(2)) 2.221(3) Å). Like complex 2, there is a strong
interaction between Ti and the R-hydrogen in one 9-BBN
hydroborate ligand. The Ti(1)-H(115) distance of 2.15(2)
Å is also shorter than that in complex 2 (2.192(17) Å) as
well. The Ti(1)-B(11) distance of 2.204(2) Å in the 9-BBN
hydroborate ligand with R-agostic hydrogen is shorter than
the Ti(1)-B(12) distance of 2.414(2) Å and Ti(1)-B(13)
distance of 2.386(2)Å in the other two 9-BBN hydroborate
ligands with no agostic hydrogen. Like complex 2, the
Ti-B(11)-C(115) angle of 80.26(12)° is much smaller than
the angles of Ti(1)-B(11)-C(111) (170.74(16)°), Ti(1)-
B(12)-C(125) (120.14(14)°), Ti(1)-B(12)-C(121) (131.48-
(14)°), Ti(1)-B(13)-C(131) (127.53(15)°), and Ti-B(13)-
C(135) (123.42(15)°) due to the agostic hydrogen interaction
in complex 3. The average titanium bridge hydrogen bond
length in 3 is 1.850 Å.
The molecular structure consists of [K(OEt2)4][Ti{(µ-
H)2BC8H14}4] (4) as a discrete cation and anion pair. The
organometallic anion [ML4]- for titanium(III) is rare;
however, the Ti(IV) organometallic anions [Ti(CH3)5]- and
[Ti2(CH3)9]- are known.21 The anion [Ti{(µ-H)2BC8H14}4]-,
shown in Figure 4, is composed of four 9-BBN hydroborate
ligands arranged in a slightly distorted tetrahedral fashion
around the titanium atom [B(10)-Ti-B(40) ) 113.17(14)°,
B(10)-Ti-B(20) ) 116.91(14)°, B(40)-Ti-B(20) ) 98.83-
(14)°, B(10)-Ti-B(30) ) 99.37(13)°, B(40)-Ti-B(30) )
114.87(14)°, B(20)-Ti-B(30) ) 114.04(15)°], with each
of the 9-BBN hydroborates functioning as a bidentate ligand,
bound to the titanium ion through two hydrogen bridges as
those in 1-3. The Ti-B distances in this anion are similar
to each other, Ti-B(10) ) 2.386(4) Å, Ti-B(20) ) 2.391-
(4) Å, Ti-B(30) ) 2.398(4) Å, and Ti-B(40) ) 2.389(4)
Å. They are in agreement with those in titanocene organo-
hydroborates, Cp2Ti{(µ-H)2BR2} (R2 ) C4H8, 2.409(4) Å,
C5H10, 2.446(3) Å, and C8H14, 2.428(2) Å).10g
From analyses of structural reports, Green and Brookhart11b,d
suggest that a metal-hydrogen distance no larger than 1.2
times the distance of a normal M-H distance would be
consistent with an agostic interaction. This approxamation
suffers from the fact that terminal M-H bond distances are
dependent upon their environment. Later we suggested that
a distance less than the sum of the metal covalent radius
and the hydrogen van der Waals radius implys an agostic
interaction.9 With a covalent radius of 1.45 Å for Ti and a
van der Waals radius of 1.2 Å22 for H, the limiting distance
III. Agostic Interactions in Complexes 2 and 3. It is
now well-known that “when a transition metal center has a
vacant orbital of suitable energy and direction, C-H groups,
(21) Kleinhenz, S.; Seppelt, K. Chem.sEur. J. 1999, 5, 3573.
(22) Sheldrick, G. M. SHELXTL-97: A Structure Solution and Refinement
Program; University of Go¨tingen: Go¨tingen, Germany, 1998.
(20) Scoles, L.; Grambarotta, S. Inorg. Chim. Acta 1995, 235, 375.
4876 Inorganic Chemistry, Vol. 44, No. 13, 2005

Titanium(III) 9-BBN Hydroborate Complexes
Table 6. Distance of Ti‚‚‚H (Å), Angles of Ti-C-C or Ti-B-C
solution. Single-crystal X-ray diffraction data were collected using
graphite-monochromated Mo KR radiation (λ ) 0.710 73 Å) on a
Nonius KappaCCD diffraction system. Single crystals of 1-4 were
mounted on the tip of a glass fiber coated with Fomblin oil (a
perfluoro polyether, Aldrich). Crystallographic data was collected
at 200 K for 1, 2, and 4 and 150 K for 3. Unit cell parameters
were obtained by indexing the peaks in the first 10 frames and
refined by employing the whole data set. All frames were integrated
and corrected for Lorentz and polarization effects using the Denzo-
SMN package (Nonius BV, 1999).24 All of the structures were
solved by direct methods and refined using the SHELXTL-97
(difference electron density calculation, full-matrix least-squares
refinements) structure solution package.22 For each structure, all
the non-hydrogen atoms were located and refined anisotropically.
There are two independent molecules in the asymmetric unit cell
of 3.
(deg), and Dihedral Angles (deg)
dihedral
angles
of TiH2
and H2B
Ti-C-C
or Ti-B-C
compound
Ti‚‚‚Hagostic
TiIII(BBN)3OEt2 (2)
this work
2.19(2)a
82.13(13)a
127.3a
158.0b
172.3b
124.1a
170.8b
179.8b
3.60b,c
128.53 (14)b
140.73(15)b
80.26(12)a
120.14(14)b
123.42(15)b
88.8a,d
TiIII(BBN)3PhNH2 (3)
this work
2.15(2)a
3.60b,c
[EtTiIV(PH3)H18a
[EtTiIVCl2]+ 18b
2.23a,d
2.06a,d
2.12a,d
2.10a
85.0a,d
TiIV(Cl)3(dmpe)Et18c-f
85.1a,d
84.5(1)a
2.11(8)a
2.06(2)a
2.29a
84.0(4)a
84.57(9)a
85.89(58)a
101.4(2) (Ti-N-C)
Preparation of Ti{(µ-H)2BC8H14}3(THF)2 (1). A solution of
K[H2BC8H14] (324.2 mg, 2.0 mmol) in 50 mL of THF was added
dropwise to a solution of TiCl4 (94.8 mg, 0.5 mmol) in 100 mL of
THF. H2 gas was observed at beginning of the reaction. After the
solution was stirred at room temperature for 12 h, the white solid
(KCl) was removed by filtration and a green product was obtained
after removing the solvent under vacuum, This green solid was
redissolved in ether and kept at -30 °C for crystallization. Green
crystalline Ti{(µ-H)2BC8H14}3(THF)2 was obtained in 40% yield.
IR (KBr): 2983 (w), 2922 (m), 2870 (s), 2836 (m), 1704 (s), 1655
(m), 1297 (m), 1109 (m), 1052 (m, br), 896 (m), 803 (w). Anal.
Calcd for C32H64B3O2Ti: C, 68.49; H, 11.50. Found: C, 68.28; H,
11.82.
CpTiIV(Cl)2[N(iC3H7)2]18h
2.25a
a Agostic interaction. b No agostic interaction. c Average distances of
Ti‚‚‚H. d Calculated.
for an agostic interaction according to our criterion is about
2.6 Å. This “loose” criterion should be supported by angular
criteria discussed above.
Table 6 lists Ti‚‚‚H distances for agostic interactions, bond
angles, and where appropriate dihedral angles for complexes
2 and 3 and several other titanium(III) complexes. It is noted
that for complexes 2 and 3 there is clearly one agostic
interaction for each compound with distances and angles in
good accord with values reported for other complexes in
Table 6. Complexes 2 and 3 also have a Ti‚‚‚H distance that
is well beyond the limit of our critereon for an agostic inter-
action which is also reflected in the relatively large angles.
Preparation of Ti{(µ-H)2BC8H14}3(OEt2) (2). A solution of
K[H2BC8H14] (324.2 mg, 2.0 mmol) in 50 mL of diethyl ether was
added dropwise to a solution of TiCl4 (94.8 mg, 0.5 mmol) in 100
mL of diethyl ether. H2 gas was observed at beginning of the
reaction. After the solution was stirred at room temperature for 12
h, the white solid (KCl) was removed by filtration and a green
product was obtained after removing the solvent under vacuum.
This green solid was redissolved in ether and kept at -30 °C for
crystallization. Green crystalline Ti{(µ-H)2BC8H14}3(OEt2) was
obtained in 42% yield. IR (KBr): 2982 (m), 2953 (m), 2862 (s),
2838 (s), 2661 (w), 2654 (w), 1960 (m), 1956 (m), 1562 (m), 1461
(m), 1356 (s), 1328 (m), 1226 (w), 1107 (m), 1084 (w), 1036 (w),
892 (m), 823 (w). Anal. Calcd for C28H58B3OTi: C, 68.48; H, 11.90.
Found: C, 68.68; H, 12.02.
Experimental Section
General Procedures. All manipulations were carried out on
a standard high-vacuum line or in a drybox under a nitrogen or
argon atmosphere. Diethyl ether, tetrahydrofuran, and toluene were
dried over sodium/benzophenone and freshly distilled prior to
use. Hexane was stirred over concentrated sulfuric acid for 2
days and then decanted and washed with water. Next, the hexane
was stirred over calcium hydride for 6 days, decanted and stirred
over sodium/benzophenone for 5 days, and finally distilled into a
storage bulb containing sodium/benzophenone. Deuterated solvents
were obtained from Cambridge Isotope Laboratories and were
vacuum transferred from a Na/K alloy before use. TiCl4 and
[(C8H14B)(µ-H)]2 (9-BBN dimer) were purchased from Aldrich and
used as received. Potassium hydride (35 wt % dispersion in mineral
oil) was purchased from Aldrich and was washed with hexane prior
to use. K[H2BC8H14]10f,23 was prepared by literature procedures.
NMR spectra were recorded on a Bruker AM-250 NMR spectrom-
eter operating at 250.11 at 303 K, and boron-11 spectra were
externally referenced to BF3OEt2 (δ ) 0.00 ppm). Infrared spectra
were recorded on a Mattson Polaris Fourier transform spectrometer
with 2 cm-1 resolution. Elemental C and H analyses were done by
Galbraith Laboratories, Inc.
Preparation of Ti{(µ-H)2BC8H14}3(PhNH2) (3). A solution of
PhNH2 (46.6 mg, 0.5 mmol) in 10 mL of diethyl ether was added
dropwise to a solution of Ti{(µ-H)2BC8H14}4(OEt2) (245.5 mg, 0.5
mmol) in 10 mL of diethyl ether. After the solution was stirred at
room temperature for 12 h, the white solid (KCl) was removed by
filtration and a green product was obtained after removing the
solvent under vacuum. This green solid was redissolved in
ether and kept at -30 °C for crystallization. Green crystalline
Ti{(µ-H)2BC8H14}3(PhNH2) was obtained in 90% yield. IR (KBr):
2983 (w), 2918 (s), 2876 (s), 2838 (s), 2687 (w), 2654 (w), 1996
(w), 1397 (s), 1286 (m), 1208 (m), 1052 (m), 931 (w), 892 (w),
802 (w). Anal. Calcd for C30H55B3NTi: C, 70.64; H, 10.87.
Found: C, 70.06; H, 11.21.
Preparation of [K(OEt2)4][Ti{(µ-H)2BC8H14}4] (4). A solution
of K[H2BC8H14] (324.2 mg, 2.0 mmol) in 50 mL of diethyl ether
was added dropwise to a solution of TiCl4 (75.9 mg, 0.4 mmol) in
X-ray Structure Determination. Suitable crystals of
Ti{(µ-H)2BC8H14}3(THF)2 (1) were grown from THF solution, and
Ti{(µ-H)2BC8H14}3(OEt2) (2), Ti{(µ-H)2BC8H14}3(PhNH2) (3), and
[K(OEt2)4][Ti{(µ-H)2BC8H14}4] (4) were grown from diethyl ether
(24) Otwinowski, Z.; Minor, W. In Methods in Enzymology; Carter, C.
W., Jr., Sweet, R. M., Eds.; Academic Press: New York, 1997; Vol.
276A, p 307.
(23) (a) Singaram, B.; Cole, T. E.; Brown, H. C. Organometallics 1984,
3, 1520. (b) Ko¨ster, R.; Seidel, G. Inorg. Synth. 1983, 22, 198.
Inorganic Chemistry, Vol. 44, No. 13, 2005 4877

Ding et al.
100 mL of diethyl ether. H2 gas was observed at beginning of the
reaction. After the solution was stirred at room temperature for 12
h, the white solid (KCl) was removed by filtration and a dark green
product was obtained after removing the solvent under vacuum.
This dark green solid was redissolved in ether and kept at -30 °C
for crystallization. Dark green crystalline [Ti{(µ-H)2BC8H14}4]-
[K(OEt2)4] was obtained in 80% yield. IR (KBr): 2995 (m), 2954
(m), 2931 (m, br), 2886 (s), 2836 (m), 2688 (w), 2657 (w), 1573
(m), 1562 (m), 1401 (w), 1308 (w), 1194 (w), 1108 (w), 1077 (w),
890 (m), 825 (w). Anal. Calcd for C48H104B4O4Ti: C, 65.85; H,
11.97. Found: C, 65.68; H, 12.02.
Acknowledgment. This work was supported by the
National Science Foundation through Grant CHE 02-13491.
Supporting Information Available: Detailed X-ray structural
data including a summary of crystallographic parameters, atomic
coordinates, bond distances and angles, anisotropic thermal param-
eters, and H atom coordinates for 1-4 (CIF) and IR spectra for
1-4 (PDF). This material is available free of charge via the Internet
at http://pubs.acs.org.
IC050422F
4878 Inorganic Chemistry, Vol. 44, No. 13, 2005