Effect of solvent on reactions of Cp2Zr{(μ-H)2BHR}2 and Cp2ZrH{(μ-H)2BHR} (R = CH3, Ph) with B(C6F5)3

Article abstract of DOI:10.1016/j.jorganchem.2007.02.031

The effect that a solvent has on reactions of Cp₂Zr{(μ-H)₂BHR}₂ and Cp₂ZrH{(μ-H)₂BHR} (R = CH₃, Ph) with B(C₆F₅)₃ has been studied. From the reaction in benzene the metathesis product Cp₂Zr{(μ-H)₂B(C₆F₅)₂}₂, 2, was isolated. In the case of diethyl ether, different hydride abstraction products, including [Cp₂Zr(OEt₂){(μ-H)₂BHPh}][HB(C₆F₅)₃], 3, [Cp₂Zr(OEt₂){(μ-H)₂BHCH₃}][HB(C₆F₅)₃], 4, [Cp₂Zr(OEt₂){(μ-H)₂BH₂}][HB(C₆F₅)₃], 5, and [Cp₂Zr(OEt)(OEt₂)][HB(C₆F₅)₃], 6, were isolated depending on the starting zirconocene complex. The diethyl ether molecules of 3-6 are weakly coordinated to Zr and displaced in THF solution. Isolation of 3 and 4 is attributed to their fast precipitation from the reaction mixture, which prevented further reactions from occurring. In addition to the hydride abstraction, a hydride metathesis was also involved in the formation of 5. Time-elapsed ¹¹B NMR studies indicate that 3 and 4 are the intermediates on the pathway to 5 and 6. The molecular structures of 2-6 were determined by single-crystal X-ray diffraction.

Full text of DOI:10.1016/j.jorganchem.2007.02.031

Journal of Organometallic Chemistry 692 (2007) 2375–2384
www.elsevier.com/locate/jorganchem
Effect of solvent on reactions of Cp2Zr{(l-H)2BHR}2 and
Cp2ZrH{(l-H)2BHR} (R = CH3, Ph) with B(C6F5)3
a,
a
b
b
Fu-Chen Liu *, Shou-Chon Chen , Gene-Hsian Lee , Shie-Ming Peng
a
Department of Chemistry, National Dong Hwa University, Hualien 974, Taiwan, ROC
b
Department of Chemistry, National Taiwan University, Taipei 106, Taiwan, ROC
Received 4 November 2006; received in revised form 5 February 2007; accepted 9 February 2007
Available online 25 February 2007
Abstract
The effect that a solvent has on reactions of Cp2Zr{(l-H)2BHR}2 and Cp2ZrH{(l-H)2BHR} (R = CH3, Ph) with B(C6F5)3 has been
studied. From the reaction in benzene the metathesis product Cp2Zr{(l-H)2B(C6F5)2}2, 2, was isolated. In the case of diethyl ether, dif-
ferent hydride abstraction products, including [Cp2Zr(OEt2){(l-H)2BHPh}][HB(C6F5)3], 3, [Cp2Zr(OEt2){(l-H)2BHCH3}][HB(C6F5)3],
4, [Cp2Zr(OEt2){(l-H)2BH2}][HB(C6F5)3], 5, and [Cp2Zr(OEt)(OEt2)][HB(C6F5)3], 6, were isolated depending on the starting zircono-
cene complex. The diethyl ether molecules of 3–6 are weakly coordinated to Zr and displaced in THF solution. Isolation of 3 and 4
is attributed to their fast precipitation from the reaction mixture, which prevented further reactions from occurring. In addition to
the hydride abstraction, a hydride metathesis was also involved in the formation of 5. Time-elapsed 11B NMR studies indicate that 3
and 4 are the intermediates on the pathway to 5 and 6. The molecular structures of 2–6 were determined by single-crystal X-ray
diffraction.
ꢀ 2007 Elsevier B.V. All rights reserved.
Keywords: Organotrihydroborate; Metathesis; Hydride abstraction
1. Introduction
by B(C6F5)3 results in the ionic compound ½Cpꢂ2ZrHꢀ-
½HBðC6F5Þ3ꢀ [4]. Several examples of hydride abstraction
from metallocene cyclic organodihydroborates using
B(C6F5)3 have been reported by Shore and co-workers.
These reactions have been shown to be solvent-dependent,
with different products being isolated from non-coordinat-
ing and coordinating solvents. In the case of toluene, a
non-coordinating solvent, B(C6F5)3 removed the hydride
from Cp2ZrH{(l-H)2BR} (R = C4H8, C5H10) yielding a
single hydrogen-bridged compound [(l-H){Cp2Zr(l-
H)2BR}2][HB(C6F5)3]. From diethyl ether, a coordinating
solvent, the ethoxy-substituted compound [Cp2Zr(OE-
t2)(OEt)][HB(C6F5)3] was isolated [5]. On the other hand,
reactions of titanium compounds Cp2Ti{(l-H)2BR}
(R = C4H8, C5H10, C8H14) with B(C6F5)3 furnished a
metathesis product Cp2Ti{(l-H)2B(C6F5)2} in toluene
and the ionic compound [Cp2Ti(OEt2)2][HB(C6F5)3] in
ether [6]. A more complicated result was obtained when
Cp2Nb{(l-H)2BR} (R = C4H8, C5H10, C8H14) was reacted
Recently there has been an increased interest in thþe prep-
aration of metallocene cations of the ½Cp02MRꢀ type
(Cp0 = C5H5, C5Me5; M = Zr, Ti), due to their catalytic
activity in Ziegler–Natta olefin polymerization [1].
Although in rare cases these 14eꢁ cationic species have
been isolated, preþparaꢁtion of THF adducts of ionic com-
pounds ½Cp02MRꢀ ½Xꢀ (X = BPh4, BR(C6F5)3) is much
more common [2]. The catalytic ability of [Cp2ZrR(THF)]+
has been studied [3]. In addition to the alkyl carbanion
abstraction to form a cation, the Lewis acid B(C6F5)3 can
also abstract a terminal hydride from a metallocene
hydride or a bridging hydrogen M–H–B from a metallo-
cene organohydroborate complex. Marks and co-workers
showed that abstraction of a hydride from CpꢂZrH2
2
*
Corresponding author. Tel.: +886 3 8633601; fax: +886 3 8633570.
E-mail address: fcliu@mail.ndhu.edu.tw (F.-C. Liu).
0022-328X/$ - see front matter ꢀ 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.02.031

2376
F.-C. Liu et al. / Journal of Organometallic Chemistry 692 (2007) 2375–2384
with B(C6F5)3. In toluene the ionic compound [Cp2Nb(l-
H)(g5-g1-C5H4)Nb(g5-g1-C5H4)2Nb{(l-H)(g5-g1-C5H4B-
(C6F5)2)}][HB(C6F5)3] formed, however, the neutral
compound CpNb(B(C6F5){(l-H)(g5-C5H4B(C6F5)2)}) was
obtained from the reaction in ether [7]. It has been reported
in our recent study that several group 4 metallocene organ-
otrihydroborate compounds display properties different
from those of their cyclic organodihydroborate analogs
[8]. For the purpose of further comparison of the metallo-
cene organodihydroborate and the organotrihydroborate
complexes, we were interested in reactions of complexes
of the latter type with B(C6F5)3. In this contribution, we
report on the recent results obtained from the studies
of reactions of Cp2Zr{(l-H)2BHR}2 and Cp2ZrH{(l-
H)2BHR} (R = CH3, Ph) with B(C6F5)3 in both benzene
and diethyl ether.
required in the case of zirconium hydride compounds
Cp2ZrH{(l-H)2BHR}. Under these conditions, 2 is a
major product along with several unidentified species,
which are soluble in benzene and characterized by singlet
signals in 11B NMR. Compound 2 has been previously
prepared by Piers and co-workers [10] from the reaction
of Cp2Zr(CH3)2 with HB(C6F5)2 in benzene. Overall, our
data obtained for 2 are consistent with those reported
by Piers, except for the IR data displaying an additional
strong absorption band at 1475 cmꢁ1 in KBr compared
with the literature spectrum acquired in Nujol. This dis-
crepancy could be explained taking into account that
Nujol itself has a strong broad absorption band at
1460 cmꢁ1
.
Competing reactions took place when Cp2Zr{(l-
H)2BHR}2 and Cp2ZrH{(l-H)2BHR} (R = CH3, Ph)
were mixed with B(C6F5)3 in diethyl ether. [Cp2Zr-
(OEt2){(l-H)2BHPh}][HB(C6F5)3], 3, [Cp2Zr(OEt2){(l-
H)2BHCH3}][HB(C6F5)3], 4, [Cp2Zr(OEt2){(l-H)2BH2}]-
[HB(C6F5)3], 5, and [Cp2Zr(OEt)(OEt2)][HB(C6F5)3], 6,
were the major products resulting from the hydride
abstraction (Scheme 2). Thus, B(C6F5)3 removed the termi-
nal hydride from Cp2ZrH{(l-H)2BHPh} producing com-
pound 3 (path a). A similar product, compound 4, was
isolated according to path b. In contrast, reactions of
Cp2Zr{(l-H)2BHPh}2 and Cp2ZrH{(l-H)2BHCH3} with
B(C6F5)3 produced compounds 5 (path c) and 6 (path d),
respectively. Compound 6, which is also a major by-prod-
uct of reactions shown in paths a–c, can be isolated from
reactions of Cp2Zr(l-H)2BHR}2 (R = CH3, Ph) and
Cp2ZrH(l-H)2BHPh} with two-fold excess of B(C6F5)3 in
diethyl ether, as described in the experimental section.
The role of excess B(C6F5)3 is to accelerate the formation
of 6, since compound 6 becomes a major product of reac-
tions shown in paths a and b at prolonged stirring. These
cationic species were isolated using crystallization. Crystals
of 3 and 4 are slightly soluble in ether; however, those of 5
and 6 are practically insoluble.
2. Results and discussion
2.1. Formation and properties of Cp2ZrH{(l-H)2BHCH3}
(1), Cp2Zr{(l-H)2B(C6F5)2}2 (2), [Cp2Zr(OEt2){(l-H)2
BHPh}][HB(C6F5)3] (3), [Cp2Zr(OEt2){(l-H)2-
BHCH3}][HB(C6F5)3] (4), [Cp2Zr(OEt2){(l-H)2-
BH2}][HB(C6F5)3] (5), and [Cp2Zr(OEt)
(OEt2)][HB(C6F5)3] (6)
Previously compound Cp2ZrH{(l-H)2BHCH3}, 1, has
been prepared in low yield through the reaction of
Cp2ZrCl2 with excess amount of LiBH3CH3 followed by
sublimation [9]. NMR studies from our group have shown
that 1 is a product of Cp2Zr{(l-H)2BHCH3}2 decomposi-
tion [8], however, it is not practical to use this as a method
for a large scale preparation of 1. Thus, compound 1 was
prepared from the reaction of Cp2Zr{(l-H)2BHCH3}2 with
N(C2H5)3 in ether according to Eq. (1). The ease of the by-
product CH3BH2 Æ N(C2H5)3 removal under a dynamic
vacuum and the high isolated yield of 1 are the distinct
advantages of this method.
H
H
B
H
H
H
CH3
Zr
ether
Zr
N(C2H5)3
+
.
+
CH3BH2 N(C2H5)3
ð1Þ
H
H
H
B
H
H
B
CH3
CH3
1
The reactions of either Cp2Zr{(l-H)2BHR}2 or
Cp2ZrH{(l-H)2BHR} (R = CH3, Ph) with B(C6F5)3 in
benzene yielded compound Cp2Zr{(l-H)2B(C6F5)2}2, 2
according to Scheme 1. Two equivalents of B(C6F5)3 were
used in the case of bis(organohydroborate) compounds
Cp2Zr{(l-H)2BHR}2, however, 3 equiv. of B(C6F5)3 were
Using d8-THF as a solvent to acquire the 1H NMR spec-
tra of compounds 3–5 resulted in displacement of the coor-
dinated ether molecules by those of the deuterated solvent.
Two broad signals corresponding to the hydrogens on
boron atoms were observed. Thus, the terminal hydrogen
of the anion appeared at 3.74 ppm for each compound,

F.-C. Liu et al. / Journal of Organometallic Chemistry 692 (2007) 2375–2384
2377
H
H
B
H
H
H
H
Ph
Zr
Zr
2 B(C6F5)3
benzene
H
H
H
H
3 B(C6F5)3
benzene
B
B
C6F5
C6F5
H
Ph
Ph
B
H
H
Zr
H
C6F5
B
2 B(C6F5)3
benzene
3 B(C6F5)3
benzene
C6F5
H
H
H
H
B
H
H
Zr
2
CH3
Zr
H
H
B
H
H
B
CH3
CH3
Scheme 1.
b
B(C6F5)3
H
H
B
ether
H
H
CH3
Zr
H
+
H
B
H
H
B
H
CH3
HB(C6F5)3
Zr
CH3
OC4H10
4
H
+
H
B
OC2H5
H
Zr
CH3
HB(C6F5)3
B(C6F5)3
ether
Zr
d
OC4H10
H
B(C6F5)3
ether
6
a
H
H
H
+
HB(C6F5)3
B
H
H
Ph
B
Zr
H
Ph
Zr
H
OC4H10
3
H
+
c
H
H
B
H
B(C6F5)3
ether
B
H
H
H
Ph
H
Zr
Zr
HB(C6F5)3
OC4H10
H
H
B
5
Ph
Scheme 2.
as previously reported for 6 [5a]. In contrast, for the cat-
ionic part the chemical shift depends on the substituent
on the boron atom. Thus, the cationic borohydride signals
for 3–5 appear at 1.20, 0.65, and 0.85 ppm, respectively.
Due to the fast exchange of bridging and terminal hydro-
gen atoms on the NMR timescale, only one cationic boro-
hydride signal was observed for each complex. Two boron
signals, a broad quartet and a doublet, were observed in
the 11B NMR spectra of 3–5. The doublet appearing at
about ꢁ26 ppm (JB–H = 93 Hz) was assigned to the anion
[HB(C6F5)3]ꢁ. The boron chemical shifts of cations of
3–5 and their THF coordinated analogs are listed in Table
1. The chemical shifts of [Cp2Zr(OEt2){(l-H)2BH2}]+ was
recorded during the reaction. In THF the coordinated
ether was replaced by THF resulting in [Cp2Zr(THF){(l-
H)2BHR}]+ cations. Although a boron chemical shift
could differ slightly from one solvent to another, Table 1
indicates that all of the THF-coordinated compounds dis-
play upfield chemical shifts compared with their ether-
coordinated counterparts. Since THF is a stronger electron

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F.-C. Liu et al. / Journal of Organometallic Chemistry 692 (2007) 2375–2384
Table 1
The boron chemical shift (ppm) of the cation in (3)–(5) and their THF
coordinated analogs
[Cp2Zr(OEt2){(l-H)2BHR}]+ [Cp2Zr(THF){(l-H)2-
in ether
BHR}]+ in THF
R = Ph
13.75
11.90
(3)
R = CH3 15.77
(4)
13.34
2.08
R = H (5)
4.33
donor than ether, it provides more electron density to the
metal. Thus, the electron deficiency of the metal is allevi-
ated resulting in the increased electron density on the
boron atom and an upfield boron chemical shift.
Formation of 5 involves both a hydride abstraction and
a hydride metathesis reaction. The time-elapsed 11B NMR
study of the reaction of Cp2Zr{(l-H)2BHPh}2 with
B(C6F5)3 (Supplementary material Fig. S5) suggests com-
pound 3 is the intermediate of the reaction. As time
elapsed, colorless crystals of [Cp2Zr(OEt2){(l-H)2BH2}]-
[HB(C6F5)3] began to form while compound 3 gradually
disappeared. The reaction occurred in a stepwise fashion.
In the first step, Cp2Zr{(l-H)2BHPh}2 reacted with
B(C6F5)3 to produce compound 3 and the organodiborane
‘‘(BH2Ph)2’’. Consequent metathesis reaction of this
organodiborane or a product related to it with compound
3 produced compound 5 and triphenylborane B(C6H5)3.
Formation of 5 is unique as the outcome of this type has
never been observed in reactions of B(C6F5)3 with other
organohydroborate complexes. In contrast, the reverse
process, alkyl metathesis, has been reported by Schlesinger
[11] and Marks [12] in their preparations of organohydrob-
orate uranium complexes.
Fig. 1. Molecular structure of Cp2Zr{(l-H)2B(C6F5)2} Æ OC4H10 showing
30% probability thermal ellipsoids.
2.2. Molecular structures
The molecular structures of 2–6 were determined by sin-
gle-crystal X-ray diffraction analysis. The crystals of 2 iso-
lated from an ether solution contain the solvent of
crystallization. The cell parameters obtained for 2 are
slightly different from those reported by Piers and co-work-
ers [10a] for the compound isolated from a benzene solu-
tion. Two molecules of 2 with slightly different bond
distances and angles were found in the unit cell, and one
of them is shown in Fig. 1. Comparison of their bond dis-
tances and angles with those for 2 isolated from benzene is
presented in Table 2. Although the Zr–B distances
˚
(2.652(3) and 2.658(3) A) for 2 isolated in this work are
Compound 6 has been prepared from the reaction of
Cp2ZrH{(l-H)2BR} (R = C4H8, C5H10) with B(C6F5)3
[5]. A mechanism has been proposed for this reaction
[13], however, no detailed NMR study has been performed.
The time-elapsed 11B NMR study of the reaction of
Cp2ZrH{(l-H)2BHCH3} with B(C6F5)3 (Supplementary
material Fig. S6) suggests compound 4 is an intermediate
in this reaction. Compound 4 formed in the beginning of
the reaction. As time elapsed, compound 4 disappeared
and crystals of compound 6 formed gradually inside the
NMR tube. This result confirms the mechanism proposed
previously [13].
slightly shorter than that reported in literature (2.696(10)
and 2.679(10) A) [10a], compound 2 still has the longest
reported Zr–H–B bond distance. Zr–H and B–H distances
as well as the related bond angles reported here are more
precise due to the fact that it was possible to locate and
refine the bridging hydrogens of 2.
˚
The molecular structures of cations of compounds 3–5
are shown in Figs. 2–4. The corresponding crystallographic
data, selected bond distances and bond angles are given in
Tables 3–6. The molecular structure of 6 has been reported
[5], the crystallographic data are included in the Supple-
mentary material. The coordination geometries around zir-
conium atoms of 3–5 are the same and can be described
best as distorted tetrahedrons. At the corners of a tetrahe-
dron are the centers of two Cp rings, an oxygen atom, and
a boron atom connected to the zirconium atom through
two bridging hydrogens. For compound 4 two independent
molecules were found in the unit cell. These two molecules
have slightly different bond distances and angles, and only
one molecular structure is presented. The hydrogens bound
to the boron atoms were located and refined isotropically.
The time-elapsed 11B NMR studies suggest that com-
pounds 3 and 4 are intermediates on the pathway to 5
and 6. The key point to their successful isolation from reac-
tions illustrated in Scheme 2 is their fast precipitation from
the reaction mixtures, which prevents further reactions
from occurring. However, under the conditions of reac-
tions illustrated in paths c and d, compounds 3 and 4 did
not precipitated immediately as they were forming, thus
providing an opportunity for isolation of 5 and 6 due to
further transformations.
˚
The Zr–B distances are 2.561(5) A in 3, 2.514(12) and

F.-C. Liu et al. / Journal of Organometallic Chemistry 692 (2007) 2375–2384
2379
Table 2
˚
Selected interatomic distances (A) and bond angles (ꢁ) for Cp2Zr{(l-
H)2B(C6F5)2}2 Æ C6H6 and Cp2Zr{(l-H)2B(C6F5)2}2 Æ OC4H10 (2)
Cp2Zr{(l-H)2-
B(C6F5)2}2 Æ C6H6
Cp2Zr{(l-H)2-
B(C6F5)2}2 Æ OC4H10
a
(20)
(200)
Zr–Hbridge
2.043
2.054
2.12(2)
2.12(2)
2.12(2)
2.14(2)
2.177
1.991
B–Hbridge
1.234
1.193
1.19(2)
1.17(2)
1.17(2)
1.13(2)
1.295
1.243
Zr–B
2.696(10)
2.679(10)
1.63(1)
1.60(1)
1.61(1)
1.62(1)
50.30
54.19
91.65
97.32
113.5(7)
113.2(7)
2.652(3)
2.658(3)
B(1)–C(7)
1.620(3)
1.608(4)
1.607(3)
1.611(4)
Fig. 3. Molecular structure of the cation in [Cp2Zr(OEt2){(l-
H)2BHCH3}][HB(C6F5)3] (4), showing 30% probability thermal ellipsoids.
H
bridge–Zr–Hbridge
bridge–B–Hbridge
51.2(9)
49.3(9)
H
101.9(17)
112.4(2)
101.8(17)
112.6(2)
C(1)–B(1)–C(7)
a
From Ref. [10a].
Fig. 4. Molecular structure of the cation in [Cp2Zr(OEt2){(l-
H)2BH2}][HB(C6F5)3] (5), showing 30% probability thermal ellipsoids.
[(C5H4Me)2Zr(THF){(l-H)2BH2}]+ (2.54(1) A, 2.55(1) A)
[15] is more crowded than that in 5 and displays a longer
˚
˚
˚
Zr–B distance. The Zr–O distances are 2.263(3) A in 3,
2.243(5) and 2.261(5) A in 4, and 2.253(5) A in 5.
˚
˚
Fig. 2. Molecular structure of the cation in [Cp2Zr(OEt2){(l-
H)2BHPh}][HB(C6F5)3] (3), showing 30% probability thermal ellipsoids.
These Zr–O distances are longer than those found in
[Cp2Zr(CH3)(THF)]+ (2.122(14) A) [16], [(C5H4Me)2-
˚
Zr(THF){(l-H)2BH2}]+ (2.239(5), 2.231(6) A) [15],
˚
+
[Cp2Zr(OBut)(THF)]+ (2.200(4) A) [17], [Cp2ZrCl(OEt2)]
˚
˚
˚
2.575(12) A in 4, and 2.531(13) A in 5. Compared with the
+
˚
˚
Zr–B distances of the neutral alkylborate complexes found
(2.211(3) A) [14], [Cp2Zr(OEt)(OEt2)] (2.209(8) A) [5a],
˚
˚
in the range of 2.538–2.696 A [8,14], these cationic Zr–B
and the sum of the corresponding covalent radii (2.16 A)
distances are either shorter than, or falling into the above
range for neutral compounds closer to its lower limit.
The cationic character alone can not account for these
short distances. Although the average Zr–B distance found
in 4 is shorter than that found in Cp2ZrH{(l-H)2BHCH3}
[18]. This result is consistent with a weak coordinating abil-
ity of ether observed in the NMR study, where THF was
found to be capable of displacing all coordinated ether
molecules from the Zr inner coordination sphere. In these
ether-coordinated cations, the ether ligand is oriented
almost in the plane defined by boron, zirconium and oxy-
gen atom of the ether molecule. The C–O–C angles of the
ether ligand are similar to each other and falling in the
range of 112.1–113.0ꢁ.
˚
(2.558(4) A) [9], the Zr–B distance in 3 is longer than
that found in the corresponding zirconium hydride
˚
Cp2ZrH{(l-H)2BHPh} (2.538(11) A) [14]. Indeed, the
steric effect also have to be considered. The cation

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F.-C. Liu et al. / Journal of Organometallic Chemistry 692 (2007) 2375–2384
Table 3
Crystallographic data
for Cp2Zr{(l-H)2B(C6F5)2}2 Æ OC4H10
(2), [Cp2Zr(OEt2){(l-H)2BHPh}][HB(C6F5)3]
(3),
[Cp2Zr(OEt2){(l-H)2-
BHCH3}][HB(C6F5)3] (4), and [Cp2Zr(OEt2){(l-H)2BH2}][HB(C6F5)3] (5)
Empirical formula
Fw
C
989.41
38H24B2F20OZr
C38H29B2F15OZr
899.45
C33H27B2F15OZr
837.39
C32H25B2F15Ozr
823.36
T (K)
150(1)
150(1)
150(1)
150(1)
Crystal system
Space group
Monoclinic
C2/c
23.0148(12)
17.9319(9)
20.7311(10)
Monoclinic
P21/c
11.8403(5)
13.0180(6)
23.8777(10)
Triclinic
Monoclinic
P21/n
12.6640(5)
20.7530(8)
12.8779(5)
ꢀ
P1
˚
a (A)
12.7385(6)
12.8112(5)
20.6137(8)
91.360(1)
91.497(1)
102.673(1)
3279.5(2)
4
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
114.033(1)
95.873(1)
104.117(1)
3)
˚
V (A
7814.0(7)
8
1.682
0.40 · 0.40 · 0.30
MoKa (0.71073)
1.49–27.50
ꢁ29 6 h 6 29,
ꢁ23 6 k 6 23,
ꢁ19 6 l 6 26
31341
3661.1(3)
4
1.632
0.25 · 0.20 · 0.20
MoKa (0.71073)
1.71–27.50
ꢁ15 6 h 6 15,
ꢁ16 6 k 6 16,
ꢁ31 6 l 6 30
35145
3282.3(2)
4
1.666
0.25 · 0.10 · 0.10
MoKa (0.71073)
1.90–25.00
ꢁ15 6 h 6 15,
ꢁ23 6 k 6 24,
ꢁ15 6 l 6 15
26618
Z
qcalcd (g/cm3)
Crystal size (mm)
1.696
0.12 · 0.10 · 0.10
MoKa (0.71073)
0.99–25.00
ꢁ15 6 h 6 15,
ꢁ15 6 k 6 15,
ꢁ24 6 l 6 24
29441
˚
Radiation (k, A)
2h Limits (ꢁ)
Index ranges
Reflections collected
Unique reflections
8970
8397
11543
5769
Unique reflections [I > 2.0r(I)]
Completeness to h (%)
3920
100.0
0.409
1800
100.0
0.409
1672
100.0
0.449
1640
100.0
0.447
l (mmꢁ1
)
Maximum/minimum transmissions
Data/restraints/parameters
0.9227, 0.9047
8397/0/526
0.0700
0.1545
0.0723
0.9566, 0.8964
5769/0/470
0.0972
0.1911
0.0842
8970/0/572
0.0403
0.1061
0.0335
1.033
11543/4/953
0.0890
0.1548
0.0951
1.106
a
R1 [I > 2.0r(I)]
b
wR2 (all data)
Rint
GOF on F2
1.117
1.264
P
P
a
R1 = iFoi ꢁ jFci/ iFoj.
P
P
2
2 1=2
b
wR2 ¼ f wðF 2o ꢁ F c2Þ = wðF 2oÞ g
.
3. Experimental
tions were carried out on a Nonius KappaCCD diffractom-
eter with graphite monochromated MoKa radiation
˚
3.1. General procedures
(k = 0.71073 A) at 150(1) K. Cell parameters were retrieved
and refined using DENZO-SMN [20] software on all reflections.
Data reduction was performed using the DENZO-SMN [20]
software. An empirical absorption correction was based
on the symmetry-equivalent reflections and was applied
to the data using the SORTAV [21] program. Structure anal-
ysis was performed using SHELXTL program on a personal
computer. Structures were solved using the SHELXS-97 [22]
program and refined using SHELXL-97 [23] program by
full-matrix least-squares on F2 values. All non-hydrogen
atoms were refined anisotropically. Hydrogen atoms
attached to the borons were located from the d-Fourier
map and refined isotropically. Hydrogen atoms attached
to the carbons were fixed at calculated positions and
refined using a riding mode. Detailed crystallographic data
are listed in Table 3.
All manipulations were carried out on a standard high
vacuum line or in a drybox under the atmosphere of nitro-
gen. Unless noted otherwise, reagents were used as obtained
from the commercial suppliers. The solvents were dried and
freshly distilled prior to use. Cp2Zr{(l-H)2BHCH3}2 [8],
Cp2Zr{(l-H)2BHPh}2 Æ (1/2 toluene) [14], and Cp2ZrH{(l-
H)2BHPh} [14] were prepared according to the literature
methods. Elemental analyses were recorded on a Hitachi
270–30 spectrometer. Proton spectra (d(TMS) 0.00 ppm)
were recorded on a Bruker Avance DPX300 spectrometer
operating at 300.132 MHz. 11B spectra (externally refer-
enced to BF3 Æ OEt2 (d 0.00 ppm)) were recorded on a Var-
ian Unity Inova 600 operating at 192.481 MHz, or on a
Bruker Avance DPX300 spectrometer operating at
96.294 MHz. Infrared spectra were recorded on a Jasco
FT/IR-460 Plus spectrometer with 2 cmꢁ1 resolution.
3.3. Preparation of complexes
3.2. X-ray crystal structure determination
3.3.1. Cp2ZrH{(l-H)2BHCH3} (1)
Cp2Zr{(l-H)2BHCH3}2 (922.1 mg, 3.3 mmol) and
about 15 mL of diethyl ether were added into a flask. After
degassing, a 0.46 mL (3.3 mmol) of N(C2H5)3 was trans-
Suitable single crystals were mounted and sealed inside
glass fibers under nitrogen. Crystallographic data collec-

F.-C. Liu et al. / Journal of Organometallic Chemistry 692 (2007) 2375–2384
2381
Table 4
Table 6
˚
˚
Selected interatomic distances (A) and bond angles (ꢁ) for
[Cp2Zr(OEt2){(l-H)2BHPh}][HB(C6F5)3] (3)
Selected interatomic distances (A) and bond angles (ꢁ) for
[Cp2Zr(OEt2){(l-H)2BH2}][HB(C6F5)3] (5)
Bond lengths
Bond lengths
av Zr–C(7-11)a
av Zr–C(12-16)a
Zr–B(1)
2.49 [1]
2.497 [4]
2.561(5)
2.263(3)
1.92(4)
Zr–H(1B)
2.10(5)
1.13(5)
1.20(5)
1.28(4)
av Zr–C(1–5)a
av Zr–C(6-10)a
Zr–B(1)
2.48 [1]
2.50 [1]
2.531(13)
2.253(5)
1.86(10)
Zr–H(1B)
2.00(10)
1.04(10)
1.17(10)
1.24(10)
1.29(10)
B(1)–H(1C)
B(1)–H(1B)
B(1)–H(1A)
B(1)–H(1D)
B(1)–H(1B)
B(1)–H(1C)
B(1)–H(1A)
Zr–O(1)
Zr–H(1A)
Zr–O(1)
Zr–H(1A)
Angles
Angles
H(1A)–Zr–H(1B)
H(1C)–B(1)–H(1B)
H(1C)–B(1)–H(1A)
H(1B)–B(1)–H(1A)
H(1C)–B(1)–C(1)
a
55.3(19)
114(3)
108(3)
98(3)
H(1B)–B(1)–C(1)
H(1A)–B(1)–C(1)
C(19)–O(1)–C(17)
C(19)–O(1)–Zr
111(2)
110(2)
112.1(3)
119.3(2)
125.4(2)
H(1A)–Zr–H(1B)
H(1D)–B(1)–H(1B)
H(1D)–B(1)–H(1C)
H(1B)–B(1)–H(1C)
H(1D)–B(1)–H(1A)
a
56(4)
H(1B)–B(1)–H(1A)
H(1C)–B(1)–H(1A)
C(11)–O(1)–C(13)
C(11)–O(1)–Zr
95(6)
104(6)
113.0(6)
120.7(5)
123.7(5)
122(8)
124(7)
105(7)
101(7)
114(3)
C(17)–O(1)–Zr
C(13)–O(1)–Zr
The standard derivation (rl) for the average bond length of Zr–C is
The standard derivation (rl) for the average bond length of Zr–C is
calculated according to the equations [19]
calculated according to the equations [19]
hli ¼ Rmlm=m;
rl ¼ ½Rmðlm ꢁ hliÞ =ðmðm ꢁ 1ÞÞꢀ
hli ¼ Rmlm=m;
rl ¼ ½Rmðlm ꢁ hliÞ =ðmðm ꢁ 1ÞÞꢀ
2
1=2
2
1=2
;
;
where Ælæ is the mean length, lm is the length of the mth bond, and m is the
number of bonds.
where Ælæ is the mean length, lm is the length of the mth bond, and m is the
number of bonds.
Table 5
under a dynamic vacuum, and the resulting white solid
was redissolved in ether and kept at ꢁ35 ꢁC until crystalli-
zation occurred. Isolation of crystalline material resulted in
696.0 mg of Cp2ZrH{(l-H)2BHCH3} (84% yield) [9].
˚
Selected interatomic distances (A) and bond angles (ꢁ) for
[Cp2Zr(OEt2){(l-H)2BHCH3}][HB(C6F5)3] (4)
Bond lengths
av Zr(1)–C(6–10)a
av Zr(1)–C(11–15)a
Zr(1)–B(1)
2.47 [1]
2.48 [1]
2.514(12)
2.243(5)
1.95(8)
1.97(8)
1.13(9)
1.17(8)
1.27(8)
av Zr(2)–C(21–25)a
av Zr(2)–C(26–30)a
Zr(2)–B(2)
2.479 [7]
2.47 [1]
2.575(12)
2.261(5)
1.92(9)
1.95(9)
1.19(9)
1.201(10)
1.204(11)
3.3.2. Cp2Zr{(l-H)2B(C6F5)2}2 Æ (C6H6) (2)
Zr(1)–O(1)
Zr(2)–O(2)
Zr(1)–H(1A)
Zr(1)–H(1B)
B(1)–H(1B)
B(1)–H(1A)
B(1)–H(1C)
Zr(2)–H(2A)
Zr(2)–H(2B)
B(2)–H(2C)
B(2)–H(2A)
B(2)–H(2B)
Method 1. In a drybox Cp2Zr{(l-H)2BHCH3}2 (141.7 mg,
0.5 mmol) and B(C6F5)3 (516.0 mg, 1.0 mmol)
were placed into a flask. The flask was evacu-
ated, and approximately 20 mL of benzene
was transferred into the flask at ꢁ78 ꢁC. The
flask was gradually warmed to room tempera-
ture and kept at room temperature overnight.
Fine crystals of Cp2Zr{(l-H)2B(C6F5)2}2 Æ
(C6H6) [10] formed. The solution was removed,
and the crystals were washed with two portions
of 5 mL of benzene and dried under vacuum.
The title compound was isolated as fine crystals
(320.0 mg, 64% yield).
Method 2. Using Cp2Zr{(l-H)2BHPh}2 Æ (1/2 toluene)
(225.0 mg, 0.50 mmol), B(C6F5)3 (511.2 mg,
1.0 mmol) and 25 mL of benzene in a proce-
dure similar to the one described in method
1 furnished 260.0 mg (52% yield) of fine crys-
tals of the title compound.
Angles
H(1A)–Zr(1)–H(1B)
H(1B)–B(1)–H(1A)
H(1B)–B(1)–H(1C)
H(1A)–B(1)–H(1C)
H(1B)–B(1)–C(1)
H(1A)–B(1)–C(1)
H(1C)–B(1)–C(1)
H(1A)–Zr(1)–O(1)
H(1B)–Zr(1)–O(1)
C(4)–O(1)–C(2)
C(4)–O(1)–Zr(1)
C(2)–O(1)–Zr(1)
a
53(3)
98(6)
98(6)
H(2A)–Zr(2)–H(2B)
H(2C)–B(2)–H(2A)
H(2C)–B(2)–H(2B)
H(2A)–B(2)–H(2B)
H(2C)–B(2)–C(16)
H(2A)–B(2)–C(16)
H(2B)–B(2)–C(16)
H(2A)–Zr(2)–O(2)
H(2B)–Zr(2)–O(2)
C(19)–O(2)–C(17)
C(19)–O(2)–Zr(2)
C(17)–O(2)–Zr(2)
51.4(15)
92(6)
96(6)
89(6)
132(5)
100(5)
113(4)
122(4)
121(4)
72(2)
123(3)
112.6(7)
125.7(5)
119.9(5)
126(5)
111(5)
125.3(11)
74.4(13)
112.7(5)
123.5(4)
121.8(4)
The standard derivation (rl) for the average bond length of Zr–C is
calculated according to the equations [19]
hli ¼ Rmlm=m;
rl ¼ ½Rmðlm ꢁ hliÞ =ðmðm ꢁ 1ÞÞꢀ
2
1=2
Method 3. Using Cp2ZrH{(l-H)2BHCH3} (84.0 mg, 0.33
mmol), B(C6F5)3 (510.0 mg, 1.0 mmol) and
10 mL of benzene in a procedure similar to
;
where Ælæ is the mean length, lm is the length of the mth bond, and m is the
number of bonds.
the one described in method
1 yielded
160.0 mg (49% yield) of fine crystals of the title
compound.
ferred into the flask at ꢁ78 ꢁC. The flask was gradually
warmed to room temperature resulting in a clear solution.
After stirring for 4 h, the volatile species were removed
Method 4. Using Cp2ZrH{(l-H)2BHPh} (157.0 mg, 0.5
mmol), B(C6F5)3 (770.0 mg, 1.5 mmol) and
10 mL of benzene in a procedure similar to

2382
F.-C. Liu et al. / Journal of Organometallic Chemistry 692 (2007) 2375–2384
the one described in method 1 afforded
THF): d 6.70 (s, 10H, Cp), 3.75 (br, q, 1H, HB), 3.39 (q,
4H, ether), 1.12 (t, 6H, ether), 0.47 (br, q, JH–H = 3.9 Hz,
3H, CH3), and 0.65 ppm (br, 3H, H3B). IR(KBr):
3118(w), 2983(w), 2943(w), 2904(vw), 2870(vw), 2420(w),
2360(w), 2337(w), 2287(vw), 2027(vw), 1957(vw),
1874(vw), 1639(m), 1603(vw), 1554(vw), 1510(s), 1464(vs),
1412(w), 1392(w), 1377(m), 1302(vw), 1273(m), 1219(vw),
1188(vw), 1113(m), 1103(m), 1068(m), 1016(w), 991(w),
966(s), 908(w), 881(vw), 827(m), 789(vw), 764(m),
725(vw), 660(w), 648(w), 602(vw), 567(vw), and
409(w) cmꢁ1. Anal. Calc. for C33H27B2F15OZr: C, 47.33;
H, 3.25. Found: C, 46.94; H, 3.31%.
234.0 mg (47% yield) of fine crystals of the title
compound. 11B NMR (benzene): d ꢁ13.4 ppm
1
(t, JB–H = 64 Hz). H NMR (C6D6): d 5.38 (s,
10H, Cp), 0.40 ppm (br, q, 4H, l-H).
IR(KBr): 3130(br, vw), 2357(br, vw),
2318(br, vw), 2183(br, w), 2112(br, w),
2027(br, vw), 1643(m), 1514(s), 1475(vs),
1379(vw), 1333(w), 1288(m), 1261(m),
1112(m), 1097(m), 1012(vw), 989(vw),
955(m), 920(vw), 885(w), 858(vw), 827(m),
756(vw), 720(vw), 687(w), 625(vw), 606(vw),
563(vw) cmꢁ1. C40H20B2F20Zr: C, 48.36; H,
2.03. Found: C, 48.44; H, 2.03%.
3.3.5. [Cp2Zr(OEt2){(l-H)2BH2}][HB(C6F5)3] (5)
Using Cp2Zr{(l-H)2BHPh}2 Æ (1/2 toluene) (225.0 mg,
0.50 mmol), B(C6F5)3 (256.0 mg,0.50 mmol) and 15 mL of
diethyl ether in a procedure is similar to the one describing
the preparation of 4 afforded 360.0 mg (87.4% yield) of the
title compound as colorless crystals. 11B NMR (THF): d
2.08 (br, quintet), ꢁ26.00 ppm (d, JB–H = 92 Hz). 11B
NMR (ether): d 4.33 (br), ꢁ25.14 ppm (d, JB–H = 90 Hz).
1H NMR (d8-THF): d 6.71 (s, 10H, Cp), 3.72 (br, q, 1H,
HB), 3.39 (q, 4H, ether), 1.12 (t, 6H, ether), 0.85 ppm
(br, 3H, H3B). IR(KBr): 3119(br, w), 2986(vw), 2486(w),
2426(m), 2376(w), 2270(vw), 2141(w), 2071(vw), 1954(w),
1639(m), 1603(vw), 1549(vw), 1510(s), 1460(vs), 1392
(w), 1377(w), 1344(m), 1317(w), 1273(m), 1184(vw),
1134(m), 1114(m), 1103(m), 1070(m), 1014(m), 991
(w), 966(s), 906(w), 881(vw), 831(m), 796(vw), 762(m),
725(vw), 658(w), 650(w), 603(vw), 569(vw), 518(vw),
3.3.3. [Cp2Zr(OEt2){(l-H)2BHPh}][HB(C6F5)3] (3)
In a drybox a 50 mL flask was charged with 101.7 mg
(0.32 mmol) of Cp2ZrH{(l-H)2BHPh} and 166.2 mg
(0.32 mmol) of B(C6F5)3. The flask was evacuated, and
about 10 mL of the diethyl ether was condensed into it at
ꢁ78 ꢁC. The flask was warmed to room temperature fol-
lowed by stirring of the reaction mixture for 4 h. A white
solid was obtained after removal of the solvent. The solid
was redissolved in diethyl ether and layered with hexane.
The title compound was obtained as colorless crystals
(190 mg, 66% yield). 11B NMR (d8-THF): d 11.90 (br),
ꢁ26.16 ppm (d, JB–H = 93 Hz). 11B NMR (ether): d 13.75
1
(br), ꢁ25.43 ppm (d, JB–H = 90 Hz). H NMR (d8-THF):
d 7.39–7.20 (m, 5H, Ph), 6.70 (s, 10H, Cp), 3.74 (br, q,
1H, HB), 3.39 (q, 4H, ether), 1.20 (br, 3H, H3B),
1.12 ppm (t, 6H, ether). IR(KBr): 3072(vw), 3033
(vw), 2999(vw), 2976(w), 2931(w), 2900(w), 2870(w),
2816(vw), 2345(s), 2220(w), 2195(s), 2148(vw), 1942(vs),
1840(vs), 1736(vw), 1639(vw), 1483(s), 1450(w), 1417
(w), 1383(vw), 1369(vw), 1340(vw), 1288(vw), 1234(vw),
1188(w), 1122(s), 1028(vw), 947(m), 935(w), 858(w),
796(vw), 637(vw), 611(vw), 578(vw), 565(vw), 517
(w), 494(vw), 472(vw), 409(vw) cmꢁ1. Anal. Calc. for
C38H29B2F15OZr: C, 50.74; H, 3.25. Found: C, 50.60; H,
3.24%.
469(vw), 446(vw), 423(vw) cmꢁ1
.
Anal. Calc. for
C32H25B2F15OZr: C, 46.58; H, 3.06. Found: C, 46.49; H,
3.01%.
3.3.6. NMR study of the reaction of Cp2Zr{(l-H)2-
BHPh}2 Æ (1/2 toluene) with B(C6F5)3 in diethyl ether
Cp2Zr{(l-H)2BHPh}2 Æ (1/2
toluene)
(10.0 mg,
0.022 mmol) and B(C6F5)3 (11.4 mg, 0.022 mmol) were
placed into an NMR tube. After degassing, the diethyl
ether was transferred into the tube, and the tube was
sealed. After warming it to room temperature a clear solu-
tion formed that was monitored by 11B NMR.
3.3.4. [Cp2Zr(OEt2){(l-H)2BHCH3}][HB(C6F5)3] (4)
Cp2Zr{(l-H)2BHCH3}2 (140.2 mg, 0.5 mmol) and
B(C6F5)3 (257.0 mg, 0.5 mmol) were placed into a reaction
flask. The flask was evacuated, and about 10 mL of diethyl
ether was transferred into the flask at ꢁ78 ꢁC. The solution
was gradually warmed to room temperature and stirred
until it became clear. Crystals of [Cp2Zr(OEt2){(l-
H)2BHCH3}][HB(C6F5)3] grew slowly from this solution.
After standing at room temperature overnight, the ether
solution was removed, and the crystals were washed twice
with 10 mL portions of cold ether and dried under vacuum.
The title compound was obtained as colorless crystals
(290.0 mg, 69.3% yield). 11B NMR (THF): d 13.34 (br),
ꢁ26.57 ppm (d, JB–H = 93 Hz). 11B NMR (ether): d 15.77
(br, q), ꢁ25.36 ppm (d, JB–H = 90 Hz). 1H NMR (d8-
3.3.7. Blank experiment: [Cp2Zr(OC4H10){(l-H)2-
BHPh}][HB(C6F5)3] and Cp2Zr{(l-H)2BHPh}2 Æ (1/2
toluene) in diethyl ether
A
reaction flask was charged with 50.0 mg of
[Cp2Zr(OEt2){(l-H)2BHPh}][HB(C6F5)3] and 10.1 mg of
Cp2Zr{(l-H)2BHPh}2 Æ (1/2 toluene). After degassing,
about 5 mL of diethyl ether was transferred into the flask
at ꢁ78 ꢁC. The flask was warmed to room temperature fol-
lowed by stirring for 30 h. The solvent was removed, and
the resulting solid was dissolved in THF. The 11B NMR
of the solution was acquired. The starting material
Cp2Zr{(l-H)2BHPh}2 and a partial decomposition of
[Cp2Zr(OEt2){(l-H)2BHPh}][HB(C6F5)3] with formation
of [Cp2Zr(OEt)(OEt2)][HB(C6F5)3] were observed, how-

F.-C. Liu et al. / Journal of Organometallic Chemistry 692 (2007) 2375–2384
2383
ever, the characteristic signal of the cation [Cp2Zr(OEt2)-
Acknowledgment
{(l-H)2BH2}]+ was not found.
This work was supported by the National Science Coun-
cil of the ROC through Grant NSC 94-2113-M-259-007.
3.3.8. Preparation of [Cp2Zr(OEt)(OEt2)][HB(C6F5)3]
(6)
Appendix A. Supplementary material
Method 1. In a drybox a reaction flask was charged with
225.0 mg of Cp2Zr{(l-H)2BHPh}2 Æ (1/2 tolu-
ene) (0.5 mmol) and 514.0 mg of B(C6F5)3
(1.0 mmol). The flask was evacuated, and
about 10 mL of diethyl ether was transferred
into the flask at ꢁ78 ꢁC. The flask was gradu-
ally warmed to room temperature, and the
reaction mixture was stirred until a clear solu-
tion was formed. In the drybox the solvent
was allowed to evaporate slowly from the
solution at room temperature yielding
307.0 mg (72% yield) of crystalline title
compound.
CCDC 624286, 624285, 624289, 624287, and 624288,
contain the supplementary crystallographic data for 2, 3,
4, 5, and 6. The data can be obtained free of charge via
htpp://www.ccdc.cam.ac.uk/conts/retrieving.html, or from
the Cambridge Crystallographic Data Centre, 12 Union
Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-
033; or e-mail: deposit@ccdc.cam.ac.uk. Supplementary
data associated with this article can be found, in the online
version, at doi:10.1016/j.jorganchem.2007.02.031.
References
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Metal-Alkyl Complexes, In: Advances in Organometallic Chemistry,
32, Academic Press, New York, 1991, p. 325;
Method 2. Cp2Zr{(l-H)2BHCH3}2 (70.0 mg, 0.25 mmol),
256.0 mg (0.5 mmol) of B(C6F5)3, and 10 mL
of diethyl ether transferred into the flask at
ꢁ78 ꢁC were allowed to warm up to room
temperature resulting in a clear solution. The
solution was stood aside at room temperature
overnight for crystallization. The crystals were
filtered off and washed twice with 3 mL por-
tions of diethyl ether. A total of 95.0 mg of
(b) H. Sinn, W. Kaminsky, Adv. Organomet. Chem. 18 (1980) 99;
(c) A.S. Guram, R.F. Jordan, Cationic Organozirconium and
Organohafnium Complexes, in: E.W. Abel, F.G.A. Stone, G.
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crystals was obtained. By 11B and H NMR
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Method 3. Cp2ZrH{(l-H)2BHCH3}
(126.2 mg,
0.5
mmol), B(C6F5)3 (256.0 mg, 0.5 mmol) and
10 mL of diethyl ether were used. The proce-
dure was similar to the one described in method
1. After standing at room temperature over-
night, the solution turned pink. This solution
was concentrated and kept at ꢁ35 ꢁC
for crystallization. Pink-colored crystals
(130 mg, 30.5%) were isolated. 11B NMR
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