Coordination properties of organoborate ligands - Steric hindrance around the distal boron center directs the conformation of the dialkylbis(imidazolyl) borate scaffold

Article abstract of DOI:10.1002/ejic.201000629

Alkylmethylbis(imidazolyl)borate ligands, [B(Im^N-Me) ₂(alkyl)Me]^- (L^alkyl; alkyl = methyl and n-butyl), have been synthesized by nucleophilic substitution from the chloride to the corresponding alkyl derivative on the boron center of the chloroborate precursor. In homoleptic complexes of nickel(II) with L^alkyl, [Ni^II(L^alkyl)₂] (1^alkyl), one of the two alkyl groups on the boron atom faces the nickel(II) center to form a C-H···M interaction. In the analogous homoleptic nikel(II) complexes of the hydride, phenyl, and methoxy derivatives 1^X (X = H, Ph, OMe), the boron-attached CH₃ moieties do not turn towards the metal center. Steric repulsion between the methyl substituent on the imidazolyl ligands and the boron-attached methyl group directs the orientation of the alkyl groups on L^alkyl. In the solution state the molecular structures of 1^alkyl observed in the solid state are retained. Mixed-ligand complexes, [Ni^II(L^alkyl)(Tp^iPr2)] (2 ^alkyl), can be synthesized by reaction of [Ni^II(Y)(Tp ^iPr2)] (Y = Cl, NO₃) with L^alkyl through selective ligand metathesis. In 2^Me, one methyl group of L ^Me approaches the nickel center retaining the bent conformation of the two imidazolyl groups. Conversely, the carbon atoms of the boron-attached nBu and Me groups of L^Bu are located away from the nickel center, and the orientation of the two imidazolyl groups is almost coplanar in 2 ^Bu. The structural characteristics of these nickel(II) complexes demonstrate the flexibility of the dialkybis(imidazolyl)borate scaffold. The configuration of the functional groups attached to the boron atom in the organoborate ligands, L^alkyl, is controlled by steric congestion around the boron center. Sterically enforced anagostic C- H···M interactions are observed in [Ni^II(L ^alkyl)₂], where alkyl = Me and nBu. In the mixed-ligand complexes [Ni^II(L^X)(Tp^iPr2)], steric hindrance around the metal center also affects the structure of the dialkylbis(imidazolyl) borate scaffold. Copyright

Full text of DOI:10.1002/ejic.201000629

FULL PAPER
DOI: 10.1002/ejic.201000629
Coordination Properties of Organoborate Ligands – Steric Hindrance Around
the Distal Boron Center Directs the Conformation of the Dialkylbis(imidazolyl)-
borate Scaffold
Shiro Hikichi*[a] Koyu Fujita,[b] Yoshitaka Manabe,[b] Munetaka Akita,[b] Jun Nakazawa,[a]
and Hidehito Komatsuzaki[c]
Keywords: Borates / Ligand effects / Nickel / N ligands / C–H···M interactions
Alkylmethylbis(imidazolyl)borate ligands, [B(ImN–Me)2(alkyl)- groups on Lalkyl. In the solution state the molecular structures
Me]– (Lalkyl; alkyl = methyl and n-butyl), have been synthe-
sized by nucleophilic substitution from the chloride to the
corresponding alkyl derivative on the boron center of the
chloroborate precursor. In homoleptic complexes of nickel(II)
with Lalkyl, [NiII(Lalkyl)2] (1alkyl), one of the two alkyl groups
on the boron atom faces the nickel(II) center to form a C–
H···M interaction. In the analogous homoleptic nikel(II) com-
plexes of the hydride, phenyl, and methoxy derivatives 1X (X
= H, Ph, OMe), the boron-attached CH3 moieties do not turn
towards the metal center. Steric repulsion between the
methyl substituent on the imidazolyl ligands and the boron-
attached methyl group directs the orientation of the alkyl
of 1alkyl observed in the solid state are retained. Mixed-li-
gand complexes, [NiII(Lalkyl)(TpiPr2)] (2alkyl), can be synthe-
sized by reaction of [NiII(Y)(TpiPr2)] (Y = Cl, NO3) with Lalkyl
through selective ligand metathesis. In 2Me, one methyl
group of LMe approaches the nickel center retaining the bent
conformation of the two imidazolyl groups. Conversely, the
carbon atoms of the boron-attached nBu and Me groups of
LBu are located away from the nickel center, and the orienta-
tion of the two imidazolyl groups is almost coplanar in 2Bu
.
The structural characteristics of these nickel(II) complexes
demonstrate the flexibility of the dialkybis(imidazolyl)borate
scaffold.
ward hydrolytic decomposition due to the higher covalency
of the B–C bond compared to the B–N linkage of poly-
(pyrazolyl)borates. Therefore, stepwise substitution of the
borate core is possible, and various ligands such as the
tripodal heteroscorpionate, methylbis(1-methyl-2-imid-
azolyl)[(3,4,5-substituted)-1-pyrazolyl]borate,[3] and a silica-
immobilized ligand,[6] which is a key component of a cata-
lyst mimicking the active site of nonheme metalloenzymes,
can be synthesized by the nucleophilic substitution of the
chlorine atom on the boron center in [B(ImN–Me)2(Cl)Me]–
(LCl).[4] The silica-immobilized ligand contains two boron-
attached alkyl groups, a methyl group and a linear alkyl
chain [i.e., derived from radical coupling of a boron-
attached allyl group with a 3-mercaptopropyl group,
–(CH2)3S(CH2)3Si(OR)3].[6] Therefore, an investigation of
the coordination behavior of alkylmethylbis(imidazolyl) bo-
rate ligands, [B(ImN–Me)2(alkyl)Me]– (Lalkyl), gives us in-
sights into the coordination structure of the active site of
our immobilized catalyst. In this study, Me and nBu deriva-
tives of Lalkyl, [B(ImN–Me)2Me2]– (LMe) and [B(ImN–Me)2-
(nBu)Me]– (LBu), have been synthesized by the reaction of
Introduction
In addition to the metal binding groups of chelating rea-
gents, other ligand components play important roles in the
control of the structural and electronic properties of the
resulting metal complex. For example, the boron centers of
poly(pyrazolyl)borates (“scorpionate” ligands such as TpR
and BpR) act as a carriers of mononegative charge as four-
coordinate borate. In addition, the tetrahedral geometry of
the boron center defines the orientation of the substituent
groups including the pyrazolyl ligands, which affects the
structures of the resulting metal complexes.[1,2]
Recently, a variety of organoborate ligand systems in-
cluding our own bis(imidazolyl)borates have been devel-
oped.[3–8] The most interesting feature of our organoborate
ligand system is the stability of the B–Cimidazolyl linkage to-
[a] Department of Material and Life Chemistry,
Kanagawa University,
3-27-1 Rokkakubashi, Kanagawa-ku, Yokohama 221-8686,
Japan
Fax: +81-45-413-9770
E-mail: hikichi@kanagawa-u.ac.jp
[b] Chemical Resources Laboratory, Tokyo Institute of Technology,
4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
[c] Department of Chemistry and Material Engineering, Ibaraki
National College of Technology,
L
Cl with the corresponding alkyllithium. A series of ligands
has been synthesised, Lalkyl, and, in turn, a series of nicke-
l(II) complexes has been prepared. The coordination prop-
erties of Lalkyl and the analogous ligand LX, including the
closely related phenyl and hydride derivatives (LPh and LH),
866 Nakane, Hitachinaka, Ibaraki 312-8508, Japan
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201000629.
Eur. J. Inorg. Chem. 2010, 5529–5537
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S. Hikichi et al.
FULL PAPER
were compared. Steric congestion around the boron center the nickel(II) complexes with bis(1-pyrazolyl)borates
influences the orientation of the metal-binding imidazolyl (= [B(pzR)2RЈ2]–; RЈ = H, alkyl)[10] and dimethylbis(2-pyr-
groups and noncoordinating groups.
idyl)borate (= [B(py)2Me2]–)[7a] as shown in Figure 1. The
nickel center sits on a crystallographic center of symmetry
and is surrounded by the imidazolyl nitrogen atoms in a
square-planar arrangement. The six-membered Ni–N–C–
Results and Discussion
Synthesis of Dialkylbis(N-methylimidazolyl)borates Lalkyl
As we have reported previously, the reaction of the chlo-
rinated borate compound, LCl, with phenyllithium yields
bis(1-methyl-2-imidazolyl)methylphenylborate, [B(ImN–Me)2-
Me(Ph)]– (LPh).[4] The same procedure has been employed
to prepare the dialkylbis(1-methyl-2-imidazolyl)borate with
methyl (LMe) and n-butyl (LBu) derivatives. The chlorinated
precursor, LCl, is formulated as an HCl adduct of the pro-
tonated form of chloromethylbis(1-methyl-2-imidazolyl)-
borate, and therefore, an excess amount (at least three
equivalents) of alkyllithium is required to obtain Lalkyl
.
The reaction of LCl with tBuLi resulted in the formation
of a hydride-containing borate [B(ImN–Me)2(H)Me]– (LH)
instead of a tBu derivative, i.e. [B(ImN–Me)2(tBu)Me]–, as
shown in Scheme 1. The IR spectrum of LH showed a peak
attributed to the B–H vibration at 2288 cm–1 in addition to
the B–CMe and B–Cimidazolyl vibrations at around
1280 cm–1. Due to the coupling with the boron nucleus, the
1
boron-attached H was not detected in the H NMR spec-
trum. The formation of LH might arise from the action of
LiH which is generated by pyrolysis of tBuLi as well the
bulk and low nucleophilicity of the tBu anion.[9]
Scheme 1. Reaction of LCl with alkyllithium.
Synthesis and Characterization of Homoleptic Nickel(II)
Complexes [NiII(LR)2]
As well as the previously reported LPh and BpR deriva-
tives, Lalkyl may behave as a bidentate ligand. In order to
clarify the coordination behavior, we examined the reaction
of a nickel(II) salt with two equivalents of LX (X = alkyl,
H, Ph) to obtain homoleptic nickel(II) complexes, [NiII-
(LX)2] (1X), containing a stable square planer nickel center.
The desired complexes with Lalkyl (1alkyl) were obtained and
their molecular structures were compared with those of the
LH and LPh derivatives. The overall molecular structures
Figure 1. Molecular structures of (a) 1Me, (b) 1Bu, (c) 1H, and (d)
of the homoleptic complexes, 1X, are similar to those of 1PhЈ. All diagrams are drawn at 30% probability.
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Coordination Properties of Organoborate Ligands
B–C–N ring adopts a boat conformation. However, varying
Although B–H···M interactions are frequently observed
the substituent on the distal boron site influences the coor- in complexes with poly(pyrazolyl)borate ligands, few exam-
dination environment of the nickel center.
ples of agostic C–H···M interactions between the α-CH of
the boron-attached alkyl group and the metal center have
been reported for dialkylbis(pyrazolyl)borate com-
plexes.[2,10–13] Furthermore, enforced agostic C–H···M inter-
actions are observed in complexes with 1,5-cyclooctanediyl-
bis(pyrazolyl)borate (= [B(pz)2(BBN)]–) due to the rigidity
and bulk of the boron-attached bicyclic dialkyl moiety.[13]
In our complexes, 1alkyl, the distances between the nickel
centers and the α-CH atom are longer (H411···Ni; 2.47 Å
in 1Me and 2.63 Å in 1Bu; see Table 1) than those found in
[CoII([B(pz)2(BBN)])2] (H–Co; 2.166 Å).[13] Weak C–H···M
interactions between square-planer d8 metal centers and the
apical hydrogen atoms of alkyl groups can be classified as
“anagostic” interactions in terms of lacking the covalency
of a M–H moiety.[14,15]
Structural Characteristics of Dialkyl Ligands Derivatives
1alkyl
The most unique structural property of the Lalkyl deriva-
tives of 1 is that the hydrogen atom on the α-CH group of
the boron-attached alkyl group lies in the vicinity of the
nickel center. Steric repulsion between the 1-methyl groups
on the imidazolyl groups and the boron-bound methyl
group leads to a small diheadral angle between the two
imidazolyl rings as well as forcing an alkyl (Me or nBu)
group to approach the nickel center due to the tetrahedral
borate geometry. The shapes of the six-membered Ni–N–
C–B–C–N rings exhibit “deep” boat conformations, indi-
cated by somewhat long distances from the nickel and bo-
In contrast, the smaller hydride substituent on the boron
ron centers to the N11–C11–C21–N21 plane consisting of center is placed in the cleft between the two imidazolyl-
the two imidazolyl ligands. A similar structure has been re- attached N-methyl groups in 1H. Similar structures have
ported for the nickel(II) complex with dimethylbis(2-pyr- been observed in the phenyl-containing ligand complexes
idyl)borate, [NiII({B(py)2Me2})2].[7a]
[NiII(LPh)2] (1Ph)[4] and [NiII(LOMe)2] (1OMe, where LOMe is bis-
Table 1. Structural parameters for the homoleptic complex 1X.
Compound
X
1Me
1Bu
1H
1PhЈ
1Ph[a]
1OMe[b]
[NiII({B(py)2Me2})2][c]
Me
Me
nBu
H
Ph
Ph
OMe
Bond length [Å]
Ni–N11
Ni–N21
B–C11
B–C21
B–C31
B–X41
Ni···H
1.887(3)
1.888(3)
1.631(5)
1.637(5)
1.630(5)
1.630(5)
2.4714
1.879(4)
1.893(3)
1.647(7)
1.640(7)
1.616(7)
1.643(7)
2.6334
1.888(9)
1.911(8)
1.592(16)
1.593(15)
1.642(17)
1.36(14)
3.0898
1.887(4)
1.880(4)
1.632(8)
1.638(8)
1.617(8)
1.628(8)
–
1.886(2)
1.896(2)
1.635(3)
1.633(4)
1.625(4)
1.631(3)
3.009
1.892(5)
1.897(4)
1.650(7)
1.641(8)
1.618(7)
1.477(7)
2.911
1.906(2)
1.902(2)
1.638(4)
1.637(4)
1.623(4)
1.639(4)
2.343[a]
Distance from the plane N11–C11–C21–N21 (= N2C2) [Å]
N2C2···Ni
N2C2···B
0.753(4)
0.710(5)
0.757(5)
0.636(7)
0.729(14)
0.541(18)
0.751(6)
0.669(8)
0.828(14)
0.484(16)
0.736(6)
0.595(8)
0.946(1)
0.728(5)
Bond angles [°]
N11–Ni–N21
N11–Ni–N21Ј
89.32(12)
90.68(12)
89.20(16)
90.80(16)
89.5(4)[d]
178.0(4)[d]
90.9(5)[d]
90.2(5)[d]
103.2(10)
110.1(9)
115(4)
112.6(9)
115(4)
101(6)
89.17(19)
90.83(19)
88.48(8)
91.52(8)
89.55(17)
90.45(17)
89.34(9)
90.66(9)
C11–B–C21
C11–B–C31
C11–B–X41
C21–B–C31
C21–B–X41
C31–B–X41
100.9(2)
116.1(3)
107.0(3)
115.9(3)
108.1(3)
108.2(3)
101.8(4)
115.5(4)
106.9(4)
113.6(4)
108.3(4)
110.1(4)
100.9(4)
116.2(5)
108.6(4)
116.2(4)
106.8(4)
107.6(4)
103.9(2)
110.1(2)
109.5(2)
108.0(2)
111.4(2)
113.4(2)
101.8(4)
108.7(4)
110.5(4)
109.9(4)
108.7(4)
116.3(4)
102.7(2)
111.9(3)
110.6(2)
111.6(2)
110.4(2)
109.5(3)
Diheadral angles between two imidazolyl rings (torsion angles of Z1–B–Ni–Z2; Z1 and Z2 denote the center of the imidazolyl ring) [°]
Z1–B–Ni–Z2
118.56
123.60
126.87
121.21
129.91
125.60
114.86
[a] Ref.[4] [b] Ref.[5] [c] Ref.[7a] [d] Space group C2/c.
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S. Hikichi et al.
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(1-methyl-2-imidazolyl)methoxymethylborate, [B(ImN–Me)2- general, the metal-interacting “anagostic” protons are ob-
(OMe)Me]–), which is formed by the reaction of Li·LOiPr served downfield, whereas the typical agostic protons show
with Ni(OAc)2·4H2O in MeOH.[5] The planar phenyl ring upfield shifts.[14,15] Similar downfield shifts of protons of
and the less sterically demanding oxygen atom of the meth- the boron-attached alkyl groups have been observed in
oxy group is located between two imidazolyl-attached N- analogous nickel(II) complexes with dialkylbis(pyrazolyl)-
methyl groups (see Figure 2). In these complexes, the boron- borates, [NiII({B(pz)2(RЈ)2})2] (RЈ = Et, Bu).[10a,13b]
attached methyl groups are not directed towards the nickel
center, and the dihedral angles of the two imidazolyl rings are
larger than those found in 1alkyl as summarized in Table 1.
Figure 2. Comparison of the LXNi moieties. (a) Schematic diagram.
(b) Space filling drawing of the half unit of 1Me and 1Ph viewing
along B–Ni axis.
A structural isomer of the previously reported 1Ph has
also been characterized successfully. In this isomer, 1PhЈ, the
phenyl substituent attached to the boron atom faces
towards the nickel center and the geometry around the
boron atom is similar to that found in 1alkyl, i.e. the boron-
attached methyl group is located between the two N-methyl
groups with relatively small dihedral angles of the two imid-
azolyl rings. The phenyl-facing complex, 1PhЈ, was obtained
by the reaction of LPh and [NiICl(PPh3)3]. Interconversion
behavior between 1Ph and 1PhЈ has not been observed, and
the formation mechanism of 1PhЈ is unclear. However, the
existence of the isomers 1Ph and 1PhЈ suggests a flexible co-
ordination behaviour of LX, and that the rearrangement of
Figure 3. Variable temperature 1H NMR spectra of (a) 1Me and (b)
the boron-attached groups on LX is possible.
1
Bu. Asterisks denote the signals attributed to impurities.
At ambient temperature, 1alkyl shows fluxional behaviour
indicated by broadening of the H NMR signals. Extreme
Solution State Behavior of Lalkyl in Homoleptic Complexes
1
In 1H NMR spectra recorded at –60 °C, the metal-direct- broadening of all signals of 1Me was observed, while the
ing α-CH protons of Me or nBu in 1Me and 1Bu, respec- signal of the boron-attached methyl proton in 1Bu was less
tively, could be discriminated from that of the other boron- broad. This difference reflects the degree of structural flexi-
attached methyl group. The protons of one methyl group bility of Lalkyl. A plausible explanation in the case of 1Me is
(1Me) and the α-methylene of nBu (1Bu) appear at δ = 1.91 that orientation exchange of the two methyl groups might
and 3.07 ppm, respectively, whereas the remaining boron- occur with a butterfly-like flipping motion of the imidazolyl
attached methyl protons are observed at around 0.4 ppm groups on LMe as shown in Scheme 2. Another possible mo-
(Figure 3). Notably, the α-CH protons of the boron-at- tion mechanism is that a ligand-dissociation process occurs
tached alkyl groups in the free ligands were observed at δ = as follows: (i) One of the two imidazolyl ligands dissociates,
0.07 (LMe) and 0.76 (LBu) ppm. These observations clearly (ii) rotation occurs about the retained Ni–N bond, (iii) re-
indicate that the molecular structures of 1alkyl determined coordination of the dissociated imidazolyl ligand occurs. In
by X-ray crystallography are kept in the solution state. In contrast, rearrangement of the boron-attached Me and nBu
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Coordination Properties of Organoborate Ligands
Scheme 2. Possible mechanism for the fluxional behaviour of Lalkyl
.
groups on LBu would be difficult due to large steric hin-
The molecular structures of 2alkyl were determined by X-
drance between the N-Me groups and the β-methylene of ray crystallography (Figure 4 and Table 2). As expected
nBu if the boron-attached methyl group should face the from the high-spin state, the geometry of the nickel(II) cen-
nickel center in 1Bu
.
ters in 2alkyl is square pyramidal supported by five nitrogen
donors from the tridentate TpiPr2 and the bidentate Lalkyl
.
The values of a normalized measure of geometry of the
five-coordinate center τ (τ = 0 for a square pyramid, τ = 1
for a trigonal bipyramid with flat base) indicate that the
geometry of the nickel center in 2Bu is slightly distorted (τ
= 0.050), whereas that in 2Me is close to perfect square py-
ramidal (τ = 0.003). The average Ni–NL bond lengths are
shorter than the Ni–NTp distances in both 2alkyl complexes,
which shows that the Lalkyl ligands are stronger donors
compared to TpiPr2. The nitrile moieties of the solvent mo-
lecules used for crystallization (EtCN for 2Me and MeCN
for 2Bu) did not coordinate to the nickel centers because the
boron-attached alkyl groups covered the sixth coordination
Synthesis and Characterization of Nickel(II) Complexes of
Lalkyl and TpiPr2 [NiII(Lalkyl)(TpiPr2)]
As described above, the α-CH of the alkyl substituents
on Lalkyl lies in the vicinity of the metal center in the homo-
leptic complexes 1alkyl. In this case, no shield surrounding
the nickel center exists. In order to clarify the controlling
factor for the structure of the dialkylbis(imidazolyl)borate
scaffold as well as the capability for C–H···M interactions
in Lalkyl, we examined the effect of steric hindrance around
the metal center, while retaining the interactive site of the
α-CH.
Reaction of the hindered TpiPr2 ligand complexes of nick-
el(II), [NiII(X)(TpiPr2)] [TpiPr2 = hydrotris(3,5-diisoprop-
yl-1-pyrazolyl)borate, X = Cl (3Cl) or NO3 (3NO3)],[16] with
one equiv. of the lithium salt of Lalkyl (generated in situ by
treatment of the protonated Lalkyl with nBuLi) at –80 °C
yielded the desired mixed-ligand complex, [NiII-
(Lalkyl)(TpiPr2)] (2alkyl; alkyl = Me or nBu) (Scheme 3). Ob-
1
servation of the paramagnetically shifted H NMR signals
of the blue-purple products suggested that the nickel(II)
center (d8) adopts a high-spin electronic configuration. No-
tably, the homoleptic complexes, 1alkyl, were formed as by-
products when the solution of the lithium salt of Lalkyl was
added to the solution of TpiPr2 complex at room tempera-
ture. Therefore, the coordination ability of Lalkyl is higher
than that of TpiPr2
.
Figure 4. Molecular structures of (a) 2Me and (b) 2Bu drawn at 30%
probability. Hydrogen atoms except those attached to boron in
TpiPr2 and those of the alkyl groups in Lalkyl are omitted for clarity.
Scheme 3. Synthesis of 2alkyl
.
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S. Hikichi et al.
FULL PAPER
Table 2. Structural parameters for the mixed-ligand complexes 2alkyl
Sterically induced C–H···M interactions are observed in
the LMe complex 2Me as well as the corresponding homo-
leptic complex 1Me. The C–H···Ni distance in 2Me is some-
what longer than that in 1Me and similar to that found for
and 3NO3(NCMe).
complexes
of
[B(pz)2(BBN)]–,
[CoII[B(pz)2(BBN)]-
(TpiPr,4–Br)] (H···Co; 2.61 Å) and [CoII([B(pz)2(BBN)])2]
(H···Co; 2.166 Å).[13] In contrast, no interaction between
the α-CH of the n-butyl group and the nickel center exists
in 2Bu due to steric repulsion between the nickel-surround-
ing iPr groups of TpiPr2 and the sp3-hydrocarbon chain of
the nBu group on LBu. The arrangement of the two imid-
azole groups comes close to coplanar, indicated by the
largest diheadral angle between the two rings (see Table 1
and Table 2). Moreover, the boron-attached carbon atoms
of the Me and nBu groups are located away from the nickel
center. Similar structural characteristics around the boron
center are found in complexes with the acetoxy group-in-
corporated ligand [B(ImN–Me)2(OAc)Me]– (= LOAc).[5] These
differences clearly demonstrate that the structural environ-
ment around the metal center also influences the arrange-
ment of the imidazolyl groups on Lalkyl as well as the alkyl
groups. The sterically enforced C–H···M interaction formed
in our complexes of nickel(II) is weak and comparable to
the crystal packing force.
Complex
2Me
N (LMe
2Bu
N (LBu
3NO3(NCMe)
O (κ2-NO3)
Equatorial donor
)
)
Coordination number
of Ni
5
5
6
τ value[a]
0.003
0.050
0.004[b]
Bond lengths [Å]
Ni–X1
Ni–X2
2.004(4)
2.022(3)
2.013(3)
2.018(3)
2.1311(18)
2.122(2)
Average of Ni–X
2.013
2.016
2.128
Ni–N1
Ni–N2
Ni–N3
2.051(3)
2.094(3)
2.065(3)
2.014(3)
2.115(3)
2.099(3)
2.1085(18)
2.038(2)
2.0316(19)
Average of Ni–NTp
2.070
2.076
2.059
Ni–Dsolv
B1–C111
B1–C121
B1–C131
B1–C141
Ni···Halkyl
–
–
2.196(2)
1.627(6)
1.628(6)
1.633(6)
1.644(6)
2.66(4)
1.617(6)
1.616(6)
1.657(7)
1.661(7)
3.712
–
–
–
–
–
Conclusions
Distance from the plane N111–C111–C121–N121 (= N2C2) [Å]
The coordination properties of alkylmethylbis(imidaz-
olyl)borate ligands, Lalkyl, have been investigated. In its
homoleptic complexes, 1alkyl, one of the two alkyl groups
attached to the boron center faces the nickel(II) center due
to the steric repulsion between the N-methyl groups of the
imidazolyl ligands and the other boron-attached methyl
group. The resulting configuration of the boron-attached
alkyl groups leads to anagostic C–H···Ni interactions. The
molecular structures of 1alkyl are essentially retained in the
solution state, although Lalkyl exhibits fluxional behavior.
In the mixed ligand complexes, 2alkyl, steric hindrance
around the metal center also affects the orientation of the
N2C2···Ni
N2C2···B1
0.601(5)
0.662(6)
0.465(5)
0.080(7)
–
–
Bond angles [°]
X1–Ni–X2
X1–Ni–N1
X1–Ni–N2
X1–Ni–N3
X2–Ni–N1
X2–Ni–N2
X2–Ni–N3
N1–Ni–N2
N1–Ni–N3
N2–Ni–N3
C111–B1–C121
C111–B1–C131
89.51(14) 89.93(11) 60.36(8)
98.00(14) 99.56(12) 96.45(8)
92.31(14) 93.08(11) 103.17(8)
169.26(14) 166.39(13) 162.90(8)
97.82(14) 98.05(13) 96.68(7)
169.10(13) 169.37(13) 163.16(8)
92.79(14) 92.59(11) 102.77(8)
92.57(13) 91.51(12) 88.32(8)
92.08(13) 93.33(12) 87.91(8)
83.52(13) 82.16(11) 93.45(8)
boron-attached alkyl and imidazolyl groups of Lalkyl
.
105.4(3)
115.9(4)
109.4(3)
105.9(4)
[X1–Ni–Dsolv; 83.07(9)]
[X2–Ni–Dsolv; 82.93(8)]
[N1–Ni–Dsolv
179.49(9)]
[N2–Ni–Dsolv; 91.96(8)]
[N3–Ni–Dsolv; 92.50(9)]
In summary, the structure of the dialkylbis(imidazolyl)-
borate scaffold is somewhat flexible and the steric hindrance
around both the boron and metal centers is a dominant
factor for the conformation of the boron-attached func-
tional groups.
;
C111–B1–C141
107.3(4)
109.6(4)
C121–B1–C131
C121–B1–C141
C131–B1–C141
115.0(4)
105.6(4)
107.0(4)
108.8(4)
108.4(4)
114.7(4)
Torsion angles of Z1–B–Ni–Z2
(Z1 and Z2 denote the centers of the imidazolyl rings) [°]
Z1–Ni–B1–Z2 129.87 160.30
–
Experimental Section
[a] τ = (β-α)/60, where α and β denote values of the first and second
largest angles around five-coordinate metal center, respectively. [b]
Upon the calculation of this value, Dsolv is omitted.
Instrumentation: IR measurements were carried out from KBr pel-
lets with JASCO FT/IR-5300 and FT/IR-550 spectrometers. NMR
spectra were recorded at room temperature with JEOL GX-270
(1H; 270 MHz) and EX-400 (1H; 400 MHz and 13C; 100 MHz)
spectrometers. Chemical shifts are reported in ppm downfield from
internal SiMe4. Field desorption (FD) mass spectra were recorded
with a JEOL JMS-700 mass spectrometer.
site (Figure S2). In contrast, the nickel(II) nitrato complex
3
NO3, the starting material of 2Bu, has an MeCN ligand to
form [NiII(κ2-O,OЈ-NO3)(TpiPr2)(NCMe)] [3NO3(NCMe);
Materials and Methods: All solvents used were purified by literature
methods: Et2O and pentane (Na–K alloy), toluene (Na), CH2Cl2,
Figure S1].[17]
5534
www.eurjic.org
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2010, 5529–5537

Coordination Properties of Organoborate Ligands
CHCl3 and MeCN (P2O5), MeOH [Mg(OMe)2] were treated with
appropriate drying agents, distilled, and stored under argon.[18]
Commercially available reagents were of the highest grade and were
used without further purification. All manipulations for the prepa-
ration of catalysts were performed under argon by using glove box
or standard Schlenk techniques. Starting materials for the organo-
borate ligands LR (R = Me, Bu, H), namely the chlorinated borate
compound [B(ImN–Me)2(Cl)Me]– (LCl)[4] and its precursor
[B(ImN–Me)2(OiPr)Me]– (LOiPr),[4] bis(1-methyl-2-imidazolyl)meth-
ylphenylborate [B(ImN–Me)2(Ph)Me]– (LPh),[4] [NiICl(PPh3)3],[19]
and [NiII(Cl)(TpiPr2)] (3Cl)[16] were prepared according to previously
reported procedures.
white H·LH was obtained in 22% yield (159 mg, 0.84 mmol).
C9H15BN4 (190.05; H·LH): calcd. C 56.88, H 7.96, N 29.48; found
C 57.02, H 7.78, N 29.15. IR (KBr): ν = 3133 (s), 2926 (vs, νCH),
˜
2288 (m, νBH), 1568 (s), 1467 (s), 1448 (s), 1412 (m), 1362 (m), 1279
(s, νBC), 1259 (s), 1192 (m), 1092 (s), 1025 (s), 934 (s), 803 (m), 731
(s), 646 (w), 584 (w), 503 (w), 432 (w), 415 (w). 1H NMR (CDCl3):
δ = –0.09 (br., 3 H, Me-B), 3.75 (s, 6 H, Me-N), 6.83 (d, J =
1.57 Hz, 2 H, 5-Him), 7.00 (d, J = 1.57 Hz, 2 H, 4-Him), 14.8 (br.,
1 H, H-N) ppm. 13C{1H} NMR (CDCl3): δ = 3.5 (br., Me-B), 32.9
(q, JCH = 139.1 Hz, Me-N), 120.1 (dd, JCH = 191.0, 2JCH
11.4 Hz, 4-Cim), 120.3 (br., 5-Cim), 154.0 (br., 2-Cim) ppm.
=
[Ni(LMe)2] (1Me): A CH2Cl2 solution (20 mL) of H·LMe (133 mg;
0.65 mmol) was added slowly to a methanol solution (15 mL) of
Ni(OAc)2·4H2O (81 mg; 0.33 mmol). The reaction mixture was
stirred for 1 h before the solvents were removed under vacuum. The
product was extracted into CH2Cl2 (30 mL) to remove any inor-
ganic impurities. After the CH2Cl2 was removed, yellow crystals
of 1Me, suitable for X-ray diffraction analysis, were obtained by
recrystallization from CH3CN/CH2Cl2 (68 mg; 0.15 mmol; 45%
yield). C20H32B2N8Ni (464.84; 1Me): calcd. C 51.68, H 6.94, N
Synthesis of the Compounds
H[B(ImN–Me)2Me2] (H·LMe):The chlorinated borate LCl, generated
in situ from the reaction of Li·LOiPr (4.05 mmol) with anhydrous
HCl (Et2O solution), was suspended in a Et2O/toluene mixture and
chilled to –78 °C. An Et2O solution of methyllithium (1.6 m;
10 mL) was added slowly. The mixture was gradually warmed to
ambient temperature, with continuous stirring for 10 h. The reac-
tion mixture was heated for 8 h, and the volatile solvents were re-
moved under vacuum. The product was washed with H2O and pen-
tane, and then dried under vacuum. This spectroscopically pure
H·LMe was obtained as a white powder (518 mg; 2.54 mmol; 63%
yield). C10H17BN4 (204.08; H·LMe): calcd. C 58.85, H 8.40, N
24.11; found C 51.22, H 6.92, N 24.13. IR (KBr): ν = 3145 (m,
˜
νCH), 3126 (s, νCH), 3117 (s, νCH), 2921 (vs, νCH), 2899 (vs, νCH),
2836 (s, νCH), 2808 (s, νCH), 1668 (w), 1550 (m), 1453 (vs), 1407
(vs), 1387 (s), 1291 (vs, νBC), 1265 (s), 1165 (vs), 1154 (vs), 1084
(m), 1062 (m), 1043 (s), 1024 (s), 987 (s), 960 (s), 844 (w), 835 (w),
829 (w) 816 (w), 745 (s), 731 (vs), 721 (vs), 708 (vs), 696 (vs), 613
(m), 511 (m), 476 (m), 409 (m). 1H NMR (CDCl3): δ = 0.52 (br.,
3 H, Me-B), 1.83 (br., 3 H, Me-B), 3.68 (s, 6 H, Me-N), 6.13 (br.,
2 H, 5-Him), 6.32 (br., 2 H, 4-Him) ppm.
27.45; found C 58.52, H 8.51, N 27.08. IR (KBr): ν = 3513 (vs,
˜
νNH), 3177 (s), 2927 (s, νCH), 2829 (s, νCH), 2050 (w), 1582 (vs),
1470 (vs), 1444 (vs), 1355 (vs), 1309 (m), 1293 (s, νBC), 1273 (s),
1249 (s), 1164 (m), 1110 (vs), 1033 (m), 1003 (vs), 984 (m), 932 (w),
916 (w), 865 (m), 843 (w), 800 (w), 755 (s), 738 (vs), 714 (vs), 695
(s), 682 (m), 613 (w), 496 (m), 463 (m), 427 (w), 409 (w). 1H NMR
(CDCl3): δ = 0.07 (br., 6 H, Me-B), 3.78 (s, 6 H, Me-N), 6.79 (d,
J = 1.5 Hz, 2 H, 5-Him), 6.95 (d, J = 1.5 Hz, 2 H, 4-Him), 13.34
(br., 1 H, H-N) ppm. 13C{1H} NMR (CDCl3): δ = 6.7 (br., Me-B),
[Ni(LBu)2] (1Bu): A CH2Cl2 solution (20 mL) of H·LBu (289 mg;
1.18 mmol) was added dropwise to a methanol solution (15 mL)
of Ni(OAc)2·4H2O (146 mg; 0.59 mmol). The reaction mixture was
stirred overnight, and then the solvents were removed under vac-
uum. The product was extracted into CH2Cl2 (20 mL) to remove
any inorganic impurities. After the removal of CH2Cl2, crystalli-
zation from CH2Cl2/hexane afforded yellow crystals of 1Bu (82 mg;
0.15 mmol; 25% yield). C26H44B2N8Ni (549.00; 1Bu): calcd. C
56.88, H 8.08, N 20.41; found C 56.55, H 8.22, N 20.29. IR (KBr):
35.0 (q, JCH = 139.1 Hz, Me-N), 119.4 (dd, JCH = 190.0, 2JCH
10.4 Hz, 4-Cim), 121.1 (ddq, JCH = 188.9, 2JCH = 13.5, 3JCH
3.1 Hz, 5-Cim), 171.3 (br., 2-Cim) ppm.
=
=
H[B(ImN–Me)2(nBu)Me] (H·LBu): H·LBu was prepared according to
the procedure for H·LMe. Instead of MeLi, a hexane solution of n-
butyllithium (1.5 m; 8 mL) was added to LCl (3.58 mmol). Spectro-
scopically pure H·LBu was obtained as a white powder (670 mg;
2.72 mmol; 76% yield). C13H23BN4 (246.16; H·LBu): calcd. C 63.43,
ν = 3149 (m, νCH), 3121 (s, νCH), 2946 (vs, νCH), 2925 (vs, νCH),
˜
2877 (vs, νCH), 2863 (vs, νCH), 2835 (vs, νCH), 2785 (s, νCH), 1657
(w), 1546 (m), 1452 (vs), 1411 (s), 1388 (m), 1368 (w), 1287 (vs,
νBC), 1203 (m), 1166 (s), 1153 (s), 1085 (m), 1062 (s), 1012 (m), 990
(s), 955 (m), 932 (m), 879 (w), 862 (w) 846 (w), 830 (w), 792 (w),
741 (m), 733 (s), 717 (vs), 699 (s), 643 (w), 626 (w), 512 (w), 425
H 9.42, N 22.76; found C 63.77, H 9.05, N 22.40. IR (KBr): ν =
˜
3413 (vs, νNH), 3140 (s), 3102 (s, νCH), 2909 (vs, νH), 2687 (s), 2007
(m), 1585 (s), 1483 (s), 1444 (s), 1409 (s), 1357 (s), 1292 (s, νBC),
1278 (vs), 1203 (w), 1157 (m), 1115 (vs), 1090 (w), 1053 (m), 1021
(m), 988 (m), 954 (m), 925 (m), 881 (m), 841 (w), 734 (vs), 685 (m),
1
(w), 413 (w), 407 (w). H NMR (CDCl3): δ = 0.43 (s, 3 H, Me-B),
0.96, (J = 7.28 Hz, 3 H, CH3CH2CH2CH2-B), 1.45–1.58 (br., 4 H,
CH3CH2CH2CH2-B), 3.06 (br., 2 H, CH3CH2CH2CH2-B), 3.68 (s,
6 H, Me-N), 5.96 (br., 2 H, 5-Him), 6.29 (br., 2 H, 4-Him) ppm.
1
644 (w), 532 (w), 471 (w), 420 (w), 404 (w). H NMR (CDCl3): δ
= 0.05 (br., 3 H, Me-B), 0.56 (vdq, J = 6.62, 2.58 Hz, 2 H,
CH3CH2CH2CH2-B), 0.70 (t, J = 7.26 Hz, 3 H, CH3CH2CH2CH2-
[Ni(LH)2] (1H): A CH2Cl2 solution (20 mL) of H·LH (54 mg;
0.28 mmol) was added dropwise to a methanol solution (10 mL)
of Ni(OAc)2·4H2O (36 mg; 0.14 mmol). The reaction mixture was
stirred for 1 h, the solvents were removed under vacuum, and the
product was extracted into toluene (20 mL). After removal of the
solvent, crystallization from CH2Cl2/MeCN afforded yellow crys-
tals of 1H (50 mg; 0.11 mmol; 81% yield). C18.5H29B2ClN8Ni
(479.25; 1H·0.5CH2Cl2): calcd. C 46.36, H 6.10, N 23.38; found C
B), ≈ 0.76 (br.,
2 H, CH3CH2CH2CH2-B), 1.07 (dt, 2 H,
CH3CH2CH2CH2-B), 3.78 (s, 6 H, Me-N), 6.78 (d, J = 1.46 Hz, 2
H, 5-Him), 6.95 (d, J = 1.46 Hz, 2 H, 4-Him), 14.5 (br., 1 H, H-N)
ppm. 13C{1H} NMR (CDCl3): δ = 6.0 (br., Me-B), 14.1 [qt, JCH
=
119.5, 2JCH = 3.7 Hz, CH3(CH2)3-B], 24.0 (br., C3H7CH2-B), 26.3
[t, JCH = 125.0 Hz, CH3(CH2)2CH2-B], 31.1 [t, JCH = 117.7 Hz,
CH3(CH2)2CH2-B], 34.9 (q, JCH = 139.7 Hz, Me-N), 119.3 (dd,
JCH = 189.4, 2JCH = 11.0 Hz, 4-Cim), 121.0 (ddq, JCH = 189.4,
2JCH = 14.7, 3JCH = 3.7 Hz, 5-Cim), 171.0 (br., 2-Cim) ppm.
46.86, H 6.44, N 23.90. IR (KBr): ν = 3153 (m, νCH), 3130 (s, νCH),
˜
2927 (vs, νCH), 2910 (vs, νCH), 2818 (s, νCH), 2316 (vs, νBH), 2251
(m), 2120 (m), 1685 (w), 1643 (w), 1545 (m), 1456 (vs), 1398 (s),
1321 (w), 1290 (s, νBC), 1264 (s), 1200 (m), 1156 (vs), 1147 (vs),
1095 (s), 1065 (vs), 1018 (s), 971 (m), 928 (m), 842 (m), 833 (m),
822 (m) 801 (m), 745 (s), 731 (vs), 720 (vs), 703 (vs), 624 (w), 469
H[B(ImN–Me)2(H)Me] (H·LH): H·LH was prepared according to the
procedure for H·LMe. Instead of MeLi, a pentane solution of tert-
butyllithium (1.54 m; 8 mL) was added to LCl (3.86 mmol). Solid
Eur. J. Inorg. Chem. 2010, 5529–5537
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
5535

S. Hikichi et al.
FULL PAPER
(m), 419 (w). H NMR (CDCl3): δ = 1.00 (br., 3 H, Me-B), 3.68 [Ni(LBu)(TpiPr2)] (2Bu): A 1.6 m n-hexane solution of n-butyllithium
1
(s, 6 H, Me-N), 5.91 (br., 2 H, 5-Him), 6.44 (br., 2 H, 4-Him) ppm.
(0.44 mL; 0.70 mmol) was slowly added to a THF solution (10 mL)
of H·LBu (172 mg; 0.70 mmol) at –80 °C. The resulting mixture was
warmed gradually to ambient temperature and stirred for 30 min.
This Li·LMe solution was added dropwise to a THF solution
(10 mL) of [NiII(NO3)(TpiPr2)] (410 mg; 0.70 mmol) at –80 °C. The
reaction mixture was warmed gradually to ambient temperature
and stirred for 2 h. The product was extracted into pentane. Evapo-
ration of the pentane solution followed by recrystallization from
MeCN at –30 °C afforded blue-purple crystalline 2Bu (323 mg;
0.42 mmol; 60% yield). C40H68B2N10Ni (769.35; 2Bu): calcd. C
62.45, H 8.91, N 18.21; found C 62.58, H 8.76, N x18.23. IR (KBr):
[Ni(LPh)2] (1PhЈ): A toluene solution (25 mL) of H·LPh (171 mg;
0.64 mmol) was added dropwise to a methanol solution (20 mL) of
[NiCl(PPh3)3] (572 mg; 0.65 mmol). After the reaction mixture was
stirred overnight, the mixture was allowed to settle for 1 h before
removal of the resultant supernatant by decantation. The residue
was dried under vacuum. Crystallization from CH3CN/THF af-
forded pale yellow crystals of 1PhЈ (60 mg; 0.10 mmol; 32% yield).
C34H44B2N8NiO (661.08; 1PhЈ·THF): calcd. C 61.77, H 6.71, N
16.95; found C 61.55, H 6.50, N 16.93. IR (KBr): ν = 3160 (m,
˜
νCH), 3129 (vs, νCH), 3055 (s, νCH), 2992 (vs, νCH), 2928 (vs, νCH),
2850 (vs, νCH), 2697 (w), 1938 (w), 1860 (w), 1806 (w), 1673 (w),
1648 (w), 1578 (m), 1542 (m), 1481 (s), 1454 (vs), 1404 (s), 1292
(vs), 1286 (vs, νBC), 1154 (vs), 1069 (s), 1032 (m), 1011 (m), 991 (s),
ν = 3123 (w, νCH), 2965 (vs, νCH), 2928 (vs, νCH), 2870 (vs, νCH),
˜
2835 (m, νCH), 2781 (w), 2540 (m, νBH), 1539 (s), 1459 (s), 1429
(m), 1395 (s), 1380 (s), 1362 (s), 1302 (s, νBC), 1282 (s, νBC), 1175
(s), 1143 (m), 1128 (m), 1105 (w), 1053 (s), 992 (m), 953 (m), 941
(m), 902 (w), 879 (w), 842 (w), 823 (m), 791 (s), 762 (m), 717 (s),
1
938 (vs), 901 (s), 837 (w), 777 (s). H NMR (CDCl3): δ = 1.10 (br.,
3 H, Me-B), 4.50 (s, 6 H, Me-N), 5.7–7.5 (br., 9 H, 4- and 5-Him
and Ph) ppm.
1
694 (m), 661 (m). H NMR (C6D6): δ = –10.9, –0.6, 2.7, 6.9, 7.6,
42.5, 61.2 ppm. FD-MS: m/z = 769 [M+], 712 [M – nBu]+.
[Ni(LMe)(TpiPr2)] (2Me): A 1.6 m n-hexane solution of n-butyllithium
(0.19 mL; 0.30 mmol) was slowly added to a THF solution (10 mL)
of H·LMe (62 mg, 0.30 mmol) at –80 °C. The resulting mixture was
warmed gradually to ambient temperature and stirred for 30 min.
This Li·LMe solution was added dropwise to a THF solution
(10 mL) of [NiII(Cl)(TpiPr2)] (172 mg, 0.30 mmol) at –80 °C. The
reaction mixture was warmed gradually to ambient temperature
and stirred for 2 h. The product was extracted into pentane to re-
move LiCl. Evaporation of the pentane solution followed by
recrystallization from EtCN at –30 °C afforded blue-purple crystal-
line 2Me (140 mg; 0.19 mmol; 63% yield). C37H62B2N10Ni (727.27;
X-ray Data Collection and Structural Determinations: Diffraction
measurements of 1Me and 3NO3(NCMe)·2MeCN were performed
with a Rigaku AFC-7R automated four-circle diffractometer. A
molybdenum X-ray source equipped with a graphite mono-
chrometer (Mo-Kα, λ = 0.71069 Å) was used. Data collection was
carried out at room temperature (23 °C). Diffraction measurements
of 1Bu, 1H·CH2Cl2, 1PhЈ·THF, 2Me·2EtCN and 2Bu were made on a
Rigaku RAXIS IV imaging plate area detector with Mo-Kα radia-
tion (λ = 0.71069 Å). Data collection was carried out at –60 °C.
Crystallographic data and the results of refinement are summarized
in Table 3. The structural analyses were performed by Win-GX.[20]
The structures of the complexes were solved by direct methods
using SIR-92[21] (except 2Bu) and SHELXS-86[22] (for 2Bu). The
structures were refined on F2 with full-matrix least-squares meth-
ods using SHELXL-97.[23] All non-hydrogen atoms, except disor-
dered solvent molecules, were refined anisotropically.
2
Me): calcd. C 61.11, H 8.59, N 19.26; found C 60.62, H 8.57, N
19.15. IR (KBr): ν = 3122 (w, νCH), 2966 (vs, νCH), 2927 (vs, νCH),
˜
2867 (vs, νCH), 2835 (m, νCH), 2806 (w), 2536 (m, νBH), 1684 (w),
1537 (s), 1471 (s), 1429 (m), 1395 (s), 1380 (s), 1362 (s), 1303 (s,
νBC), 1284 (s, νBC), 1175 (s), 1143 (m), 1128 (m), 1105 (w), 1051
(s), 1017 (m), 997 (m), 969 (s), 944 (w), 922 (w), 900 (w), 878 (w),
838 (w), 823 (m), 787 (s), 765 (m), 738 (w), 714 (s), 692 (m), 660
1
(m). H NMR (C6D6): δ = –0.2, 2.4, 6.8, 7.6, 45.6, 61.1 ppm. FD-
The hydrogen atoms of the nickel-facing methyl group in 2Me were
refined isotropically. The positions of boron-attached hydrides of
MS: m/z = 727 [M+], 712 [M – Me]+.
Table 3. Summary of crystallographic data.
Compound
1Me
1Bu
1H·CH2Cl2
1PhЈ·THF
2Me·2EtCN
2Bu
3NO3(NCMe)·2MeCN
Formula
Formula weight
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
β [°]
C10H16BNNi0.5 C13H22BNNi0.5 C9.25H15BClN4Ni0.50 C17H22BN4Ni0.5O0.5 C43H72B2N12Ni C40H68B2N10Ni C33H55BN10NiO3
232.43
274.51
257.87
monoclinic
C2/c (#15)
14.732(18)
13.704(4)
14.033(5)
90.00
119.833(18)
90.00
2458(3)
8
330.55
monoclinic
P21/n (#14)
8.393(4)
15.545(3)
13.205(9)
90.00
100.91(6)
90.00
1691.8(15)
4
837.45
769.37
709.39
triclinic
triclinic
monoclinic
P21/c (#14)
13.9089(10)
16.4183(10)
21.8641(19)
90.00
96.6762(4)
90.00
4959.0(6)
4
orthorhombic monoclinic
P212121 (#19) P21/n (#14)
18.5584(6)
18.8638(6)
12.7070(5)
90.00
90.00
90.00
4448.5(3)
4
¯
¯
P1 (#2)
P1 (#2)
8.195(2)
9.800(2)
8.0108(16)
91.83(2)
93.65(2)
112.628(17)
591.5(2)
2
9.5021(18)
10.0621(6)
8.1038(12)
101.409(13)
96.045(12)
103.906(5)
727.67(18)
2
13.732(3)
24.240(3)
12.2315(14)
90.00
98.0130(10)
90.00
γ [°]
V [Å3]
4031.5(11)
4
Z
D (calcd.) [g cm–3
]
1.305
1.253
1.394
1.298
1.122
1.149
1.169
μ(Mo-Kα) [mm–1
No. unique reflections
]
0.844
0.696
1.030
0.614
0.432
0.475
0.524
2717
2900
1825
3197
10428
5620
7096
No. reflections [IϾ2σ(I)] 2646
2595
1809
3195
4869
4231
5576
No. parameters refined
R [IϾ2σ(I)]
R (for all data)
wR [IϾ2σ(I)]
wR (for all data)
GOF
147
175
0.0451
0.0523
0.1150
0.1171
1.125
153
211
576
0.0766
0.1666
0.1778
0.2096
0.970
525
448
0.0494
0.0504
0.1218
0.1221
1.173
0.0843
0.0852
0.2286
0.2292
1.108
0.0396
0.0400
0.1002
0.1002
1.244
0.0420
0.0548
0.1000
0.1042
0.906
0.0436
0.0673
0.1271
0.1338
1.102
5536
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© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2010, 5529–5537

Coordination Properties of Organoborate Ligands
H (in 1H) and TpiPr2 (in 2Me and 2Bu) were refined. Other hydrogen
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L
atoms [except those of the disordered solvent molecules in
1H·CH2Cl2, 1PhЈ·THF, and 3NO3(NCMe)·2MeCN, and the methine
hydrogen atoms of the disordered isopropyl groups in 2Me and 2Bu
]
were added in the riding model with C–H = 0.96 Å (for methyl
groups), 0.98 Å (for methine groups), or 0.93 Å (for aromatic rings)
with Uiso(H) = 1.2Uiso(attached atom).
CCDC-779667 (1Me), CCDC -779668 (1Bu), CCDC -779669
(1H·CH2Cl2), CCDC -779670 (1PhЈ·THF), CCDC -779671
(2Me·2EtCN), CCDC -779672 (2Bu), and CCDC -779673
[3NO3(NCMe)·2MeCN] contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
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Received: June 5, 2010
Published Online: October 29, 2010
Eur. J. Inorg. Chem. 2010, 5529–5537
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
5537