Syntheses and characterization of new (pyrazolato)(pyrazole) rutheniums with κ3-polypyrazolylborates: Halogeno-anion binding through the tris(pyrazole) moiety

Article abstract of DOI:10.1016/j.ica.2005.08.005

(Polypyrazolylborato)(benzonitrile) ruthenium(II) complexes [RuCl{BR(pz)₃}(PhCN)₂] (R = pz, H; pz = pyrazol-1-yl), prepared from trans-[RuCl₂(PhCN)₄] and K[BR(pz) ₃], were allowed to react with potassium 3,5-dimethyl-substituted polypyrazolylborate salt K[BH(3,5-Me₂pz)₃], and gave (pyrazolato)(pyrazole) species of [Ru{BR(pz)₃}(3,5-Me ₂pz)(3,5-Me₂pzH)₂] {R = pz (1), H (2)}, respectively. Upon protonation with HBF₄ (Et₂O), the species 1 was converted to a fairly stable tris(pyrazole) derivative [Ru{B(pz)₄}(3,5-Me₂pzH)₃]BF₄ (3), which worked as a novel halogeno-anion receptor. Moreover, the complex [RuCl₂(PhCN)₄] was treated with K[BH(3,5-Me ₂-4-Brpz)₃] in the presence of 3,5-dimethyl-4- bromopyrazole, 3,5-Me₂-4-BrpzH, to afford [Ru{BH(3,5-Me ₂-4-Brpz)₃}(3,5-Me₂-4-Brpz)(3,5-Me ₂-4-BrpzH)₂] and [Ru{BH(3,5-Me₂-4-Brpz) ₃}(3,5-Me₂-4-Brpz)(3,5-Me₂-4-BrpzH)(PhCN)]. Single-crystal X-ray structural analyses were carried out for 1, 3 ? CHCl₃, [Ru{B(pz)₄}(3,5-Me₂pzH) ₂(OH₂)]O₃SC₆H₄CH ₃ ? CH₃OH, and [RuCl{B(pz)₄}(3,5-Me ₂pzH)₂] ? CHCl₃.

Full text of DOI:10.1016/j.ica.2005.08.005

Inorganica Chimica Acta 359 (2006) 990–997
www.elsevier.com/locate/ica
Syntheses and characterization of new (pyrazolato)(pyrazole)
rutheniums with j3-polypyrazolylborates: Halogeno-anion
binding through the tris(pyrazole) moiety
*
Masayoshi Onishi , Mamoru Yamaguchi, Shiho Kumagae,
1
Hiroyuki Kawano , Yasuhiro Arikawa
Department of Applied Chemistry, Faculty of Engineering, Nagasaki University, Nagasaki 852-8521, Japan
Received 7 July 2005; accepted 14 August 2005
Available online 26 September 2005
Ruthenium and Osmium Chemistry Topical Issue
Abstract
(Polypyrazolylborato)(benzonitrile) ruthenium(II) complexes [RuCl{BR(pz)3}(PhCN)2] (R = pz, H; pz = pyrazol-1-yl), prepared from
trans-[RuCl2(PhCN)4] and K[BR(pz)3], were allowed to react with potassium 3,5-dimethyl-substituted polypyrazolylborate salt K[BH(3,5-
Me2pz)3], and gave (pyrazolato)(pyrazole) species of [Ru{BR(pz)3}(3,5-Me2pz)(3,5-Me2pzH)2] {R = pz (1), H (2)}, respectively. Upon pro-
tonation with HBF4 (Et2O), the species 1 was converted to a fairly stable tris(pyrazole) derivative [Ru{B(pz)4}(3,5-Me2pzH)3]BF4 (3), which
worked as a novel halogeno-anion receptor. Moreover, the complex [RuCl2(PhCN)4] was treated with K[BH(3,5-Me2-4-Brpz)3] in the pres-
ence of 3,5-dimethyl-4-bromopyrazole, 3,5-Me2-4-BrpzH, to afford [Ru{BH(3,5-Me2-4-Brpz)3}(3,5-Me2-4-Brpz)(3,5-Me2-4-BrpzH)2] and
[Ru{BH(3,5-Me2-4-Brpz)3}(3,5-Me2-4-Brpz)(3,5-Me2-4-BrpzH)(PhCN)]. Single-crystal X-ray structural analyses were carried out for 1,
3 Æ CHCl3, [Ru{B(pz)4}(3,5-Me2pzH)2(OH2)]O3SC6H4CH3 Æ CH3OH, and [RuCl{B(pz)4}(3,5-Me2pzH)2] Æ CHCl3.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Ruthenium; Polypyrazolylborate; Halogeno anion receptor; Pyrazole; Supramolecule
1. Introduction
Polypyrazolylborate anions [BR(pz)3]ꢀ (pz = pyrazol-1-
yl) have been used as versatile supporting ligands for a
wide range of transition- and rare earth-metal complexes
Abbreviations used in this paper: The group 3,5-Y2pz represents a
pyrazol-1-yl group with Y substituents at its 3- and 5-positions; The 3,5-
[1]. Wide-spread considerable attention paid to the anionic
tridentate j3-BR(pz)3 coordination stems probably from
their comparison with the well-known g5-cyclopentadienyl
family [1a–3]. As part of our objectives in developing new
(j3-polypyrazolylborato)ruthenium chemistry [4], we have
prepared some half-sandwich-type complexes, involving
[RuCl{BR(pz)3}(PhCN)2] and [RuCl2{BR(pz)3}(NO)]
(R = pz, H). Stable half-sandwich rutheniums with mono
(j3-polypyrazolylborate) contain mostly some auxiliary li-
gands with competent capabilities in stabilization of the
complexes, such as organo nitrile and nitrosyl ligands in
Y2-4-Xpz indicates additional substitution of X at the 4-position of the
3,5-disubstituted group. Their neutral pyrazole molecules are expressed as
3,5-Y2pzH and 3,5-Y2-4-XpzH, respectively. General expression of
tridentate polypyrazolylborate ligands and their substituted ones, ligating
triply via 2-N nitrogen atoms of the groups, are abbreviated simply as
BR(pz)3 and BR(pz*)3, respectively, and those in other coordination
modes are shown in appropriately specified forms, such as j2-N,N0-
BR(pz)3 for the bidentately coordinated BR(pz)3 via two pyrazolyl
nitrogen atoms.
*
Corresponding author. Fax: +81 95 819 2684.
E-mail address: onishi@net.nagasaki-u.ac.jp (M. Onishi).
Present address: Kogakuin University, 2665-1 Nakano, Hachioji,
1
Tokyo 192-0015, Japan.
0020-1693/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2005.08.005

M. Onishi et al. / Inorganica Chimica Acta 359 (2006) 990–997
991
3-Me substituents, but separated yellowish green powdery
products were found to be (pyrazolato)(pyrazole) species
[Ru{BR(pz)3}(3,5-Me2pz)(3,5-Me2pzH)2] (1) and (2) with
pz and H as R, respectively. Coordination structure of 1
was crystallographically disclosed (Fig. 1). Bond cleavages
between boron and 1-N nitrogen atoms in polypyrazolyl-
borate anions have been observed in the course of their
reactions with some transition- and rare earth-metal com-
pounds [4c,11,12]. In solution state, each NMR spectrum
of these products showed spectroscopic equivalence of
three metal-linking pz groups in the BR(pz)3 moiety and
also of one 3,5-Me2pz and two 3,5-Me2pzH ligands, indi-
cating that two NH protons in the (3,5-Me2pz)(3,5-
Me2pzH)2 part are moving fast on the three non-ligating
nitrogen atoms (Fig. 2(a)).
Chart 1.
our cases [4] and tertiary phosphines, carbonyl, p-arene
aromatics, and many types of polydentate chelate ligands
described in the literatures [1]. As examples without these
competent auxiliary ligands, in contrast to the well-
known halo(g5-pentamethylcyclopentadienyl)rutheniums
[Ru(Cp*)Xn]m (X = Cl, Br, I) [3], the corresponding ha-
lo(j3-polypyrazolylborato)ruthenium analogs have not
been afforded so far. Moreover, it also seems to be note-
worthy that only a few ruthenium complexes have been
described, with polypyrazolylborates substituted at 3-posi-
tions of their metal-linking pyrazolyl groups [4c–6], in spite
of many researches [1,7] of modified electro- and stereo-
chemical properties of analogous polypyrazolylborato
complexes with other metal ions. In this paper, we report
the syntheses and characterization of a few (pyrazo-
lato)(pyrazole) ruthenium(II) complexes with j3-poly-
pyrazolylborate systems, BR(pz)3 (R = pz, H) and
BH(3,5-Me2-4-Brpz)3 [8], and also halogeno-anion trap-
ping function [9] of a tris(pyrazole) derivative with the
B(pz)4 system (See Chart 1).
(Pyrazolato)bis(pyrazole)ruthenium moieties in solution
state were presumed to retain a trigonal prism-like confor-
mation compelled by intra-molecular hydrogen bonding
between pyrazolato and pyrazole ligands (Fig. 2(a)). This
motivated us to the study of protonation and deprotona-
tion properties of the moieties as a proton pool. Treatment
of the complex 1 in CDCl3 with an equimolar quantity of
1
HBF4 (Et2O) changed two H NMR signals of the pyraz-
olyl methyl groups at d 2.46 and 0.77 to those at d 2.54
and 1.16, respectively. Significant lower-field shift of the
latter signal is especially noteworthy, and was probably
associated with the NH-neighboring 5-Me protons in the
2. Results and discussion
2.1. Formation of (pyrazolato)(pyrazole)rutheniums and
halogeno-anion incorporation with the tris(pyrazole) moiety
Reactions of the benzonitrile complex trans-
[RuCl2(PhCN)4] with an equimolar quantity of unsubsti-
tuted polypyrazolylborate salts, K[BR(pz)3] (R = pz, H),
in refluxing dichloromethane afforded half-sandwich
species of [RuCl{BR(pz)3}(PhCN)2] [4]. As preliminarily
communicated [10], these half-sandwich species have been
converted to hetero sandwich derivatives [Ru{BR(pz)3}
{BR0(pz0)3}] by further treatment with other poly-
pyrazolylborate anions BR0(pz0)3 free from substitution
at the 3-position of the pz0 group, and the sandwich
complexes have demonstrated their utility in the evaluation
of electrochemical properties of the respective poly-
pyrazolylborato ligands.
Fig. 1. ORTEP drawing of 1 with 30% probability thermal ellipsoids and
atom labels only for important atoms. Hydrogen atoms are omitted for
clarity, except NH protons. Selected bond lengths and inter-atomic
distances (A): Ru–N(1) 2.041(3), Ru–N(3) 2.048(4), Ru–N(7) 2.125(4),
Ru–N(9) 2.120(3), Ru–B 3.126(5), N(8)–N(10) 2.707(4), N(10)–N(10*)
3.411(6).
˚
As one extension, the half-sandwich complexes
[RuCl{BR(pz)3}(PhCN)2] were treated with an equimolar
amount of K[BH(3,5-Me2pz)3] for the preparation of the
sandwiches [Ru{BR(pz)3}{BH(3,5-Me2pz)3}] retaining
Fig. 2. (Pyrazolato)(pyrazole) and its related derivative species of ruthe-
nium. (a) (pyrazolato)bis(pyrazole) species; (b) tris(pyrazole) species;
(c) chloride anion incorporated species.

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M. Onishi et al. / Inorganica Chimica Acta 359 (2006) 990–997
Ru(3,5-Me2pzH)3 moiety of the mono-protonated species
[Ru{B(pz)4}(3,5-Me2pzH)3]BF4 (3). A broad signal at d
10.4 was observed with 3H integral, assignable to NH pro-
tons of the moiety. In addition, orange crystals of
3 Æ CHCl3 were precipitated and confirmed to be the
mono-protonated species 3 as formulated above, by a sin-
gle-crystal X-ray structural analysis (Fig. 3). When further
treatment of 3 was performed with another equimolar
amount of HBF4 (Et2O), we could not isolate any gener-
Structure of 4 was crystallographically characterized as
shown in Fig. 4, and confirmed dissociation of one
3,5-Me2pzH molecule. Moreover, it is noted that deproto-
nation experiments of 1 and 2 were attempted by use of
[NEt4]OH (CH3OH) in a molar ratio of 1/1, but obvious
results were not attained satisfactorily.
Concerning the fairly stable complex 3 (Fig. 2(b)),
tris(pyrazole)ruthenium moiety with three NH protons
led us to the study of its halogeno anion binding function-
ality [9,13]. Phosphonium salts [PPh4]X (X = Cl, Br, I)
were added to dichloromethane and deuterated chloroform
solutions of 3, and some precipitates of moderately insolu-
ble [PPh4]BF4 were removed for liquid-state spectroscopic
observation. Fig. 5 exhibits IR spectral change by the in-
crease in the quantity of the added [PPh4]Cl, in the region
of ca. 2550–4000 cmꢀ1. Upon the successive increase in the
[PPh4]Cl quantity by the increment of 1/4 mole relative to
3, IR absorption band at 3226 cmꢀ1 grew strong, and the
band at 3424 cmꢀ1 was decreased to disappear finally.
The former band was the m(NH) for the tris(pyrazole)ruthe-
nium moiety with three NH parts holding up the chloride
anion through NHꢁ ꢁ ꢁClꢀ hydrogen-bonding (Fig. 2(c)),
and the latter band was attributed to the one for the moiety
without the anion binding. Addition of only equimolar
quantity of [PPh4]Cl was enough for apparently complete
conversion from 3 to ‘‘{(pz)B(pz)3}Ru(3,5-Me2pzH)3Cl’’,
demonstrating a high affinity for the chloride incorporation.
1
ated species in a pure state, but H NMR signals (CDCl3)
of the uncoordinated pz ring protons in the B(pz)4 ligand
changed from a set of d 6.76, 8.11, and 8.32 to a new one
of d 7.14, 8.48, and 8.97. Remarkable lower-field shifts of
these signals probably indicated additional protonation
of the 2-N nitrogen in the uncoordinated pz group. Addi-
tion of more quantities of HBF4 (Et2O) gave rise to decom-
position of the B(pz)4 fragment, probably generating some
(pyrazole)ruthenium species on the basis of 1H NMR
spectra.
As for similar mono-protonation of the BH(pz)3 ana-
1
logue 2, the corresponding methyl signals in its H NMR
spectra (CDCl3) showed only slight shifts from d 2.53
and 0.74 to d 2.49 and 0.88, respectively, and the 11B
NMR doublet (JBH = 79 Hz) at d ꢀ22.3 for the BH part
disappeared apparently. In this case, the corresponding
tris(pyrazole) species was not generated, and these findings
were probably associated with other reaction proceedings
of HBF4 (Et2O) with the BH part, rather than protonation
of the pyrazolato ligand 3,5-Me2pz to form the expected
tris(pyrazole) moiety.
On the other hand, the complex 1 was also treated with
an equimolar amount of p-toluenesulfonic acid monohy-
drate (TsOH Æ H2O) in place of HBF4 (Et2O), and crystal-
lization of the reaction mixture gave orange-colored
crystals of [Ru{B(pz)4}(3,5-Me2pzH)2(OH2)]OTs (4).
Fig. 3. ORTEP drawing of molecular cationic part of 3 Æ CHCl3 with 30%
probability thermal ellipsoids and atom labels only for important atoms.
Hydrogen atoms are omitted for clarity, except NH protons. Selected
Fig. 4. ORTEP drawing of molecular cationic part of 4 Æ CH3OH with
30% probability thermal ellipsoids and atom labels only for important
atoms. Hydrogen atoms are omitted for clarity, except NH protons.
˚
˚
bond lengths and inter-atomic distances (A): Ru–N(1) 2.045(6), Ru–N(3)
Selected bond lengths and inter-atomic distances (A): Ru–N(1) 2.007(4),
2.052(6), Ru–N(5) 2.047(7), Ru–N(9) 2.126(6), Ru–N(11) 2.150(7), Ru–
N(13) 2.131(6), Ru–B(1) 3.153(9), N(10)–N(12) 3.48(1), N(10)–N(14)
3.07(1), N(12)–N(14) 3.57(1).
Ru–N(3) 2.044(4), Ru–N(5) 2.038(4), Ru–N(9) 2.108(4), Ru–N(11)
2.111(4), Ru–O(1) 2.159(3), Ru–B 3.121(6), N(10)–O(1) 3.026(5), N(12)–
O(1) 3.002(5).

M. Onishi et al. / Inorganica Chimica Acta 359 (2006) 990–997
993
longed standing of the solution to precipitate the species
‘‘{(pz)B(pz)3}Ru(3,5-Me2pzH)3Cl’’, some crystals were
deposited, but were found to be only its decomposed prod-
uct [RuCl{B(pz)4}(3,5-Me2pzH)2] (5) with a chloroform
molecule. Fig. 6 shows the crystal structure of 5, which
was probably supported by the intra-molecular hydrogen
bonding [15] between the chloride ligand and two acidic
NH protons of the ligating 3,5-Me2pzH molecules retained.
˚
Their inter atomic distances were 2.49(8) and 2.69(8) A.
2.2. (Pyrazolato)(pyrazole) ruthenium complexes with the
substituted j3-polypyrazolylborato system BH(3,5-Me2-4-
Brpz)3
Syntheses of (j3-polypyrazolylborato) complexes,
substituted at the 3-position in their metal-linking pyraz-
olyl groups, have been performed for tuning electro- and
stereo-chemical properties of the reaction fields built up
on the central metal ions [1a,7], but to our knowledge,
for ruthenium there are only a few examples, involving
[RuH{BH(3-iPr-4-Brpz)3}(cod)],
[Ru{BH(3,5-iPr2pz)3}
(py)(OH2)2]OTf, and [Ru(Cp){BH(3,5-Me2pz)3}] [5]. In
our reactions of [RuCl2(PhCN)4] with potassium 3,5-di-
methyl-substituted polypyrazolylborate K[BH(3,5-Me2-
pz)3], we have not isolated any assignable products except
the free pyrazole (i.e., 3,5-Me2pzH). On the other hand,
similar reactions with its 4-bromo-substituted salt
K[BH(3,5-Me2-4-Brpz)3] [8c], in the presence of the pyra-
zole (3,5-Me2-4-BrpzH), gave two (pyrazolato)(pyrazole)
Fig. 5. IR spectral change of 3 in CDCl3 by the increase in the [PPh4]Cl
quantities added (a) complex 3; (b) 3 with 1/4 mole of [PPh4]Cl; (c) 3 with
2/4 mole of [PPh4]Cl; (d) 3 with 3/4 mole of [PPh4]Cl; (e) 3 with 4/4 mole
of [PPh4]Cl.
Although IR spectral change has not been regarded as a
reliable signal for halogeno anion sensing [14], Fig. 5 dis-
plays the extent of captured chloride anion distinctly.
Moreover, addition of [PPh4]X (X = Br, I) in CDCl3
brought about new IR band growth at 3258 and
3261 cmꢀ1, respectively, certifying analogous binding to-
ward these Xꢀ anions. Incorporation of halogeno anions
1
would also be supported by H NMR signal shifts of the
methyl groups in the (3,5-Me2pzH)3 moiety; the signals
were observed at d 2.57 and 0.62 for Clꢀ, d 2.54 and 0.81
for Brꢀ, and d 2.52 and 0.97 for Iꢀ, respectively. It is noted
that a mixture of 1 with the equimolar HCl (Et2O) demon-
strated the same IR and NMR signal patterns as those ob-
tained by treatment of 3 with [PPh4]Cl. Thus, the present
system is a new example for the halogeno anion incorpora-
tion with the tris(pyrazole) moieties, additionally to the
preceding examples; ‘‘{HB(3,5-Me2pz)3}Pb(3,5-Me2pzH)3-
Cl’’ [13a], ‘‘[{HB(3-tBupzH)3}Cl]AlCl4’’ [13b], and ‘‘fac-
[Re(CO)3(pzH)3]Cl’’ [14].
In order to reveal the structural characteristics of the
tris(pyrazole) frame with captured halogeno anions
through its three NH parts, we attempted to grow their sin-
gle crystals for X-ray structural analyses. For example, the
complex 3 was mixed with [PPh4]Cl in chloroform, fol-
lowed by slow introduction of n-hexane vapor. After pro-
Fig. 6. ORTEP drawing of molecular cationic part of 5 Æ CHCl3 with 30%
probability thermal ellipsoids and atom labels only for important atoms.
Hydrogen atoms are omitted for clarity, except NH protons. Selected
bond lengths and inter-atomic distances (A): Ru–N(1) 2.069(4), Ru–N(3)
2.045(4), Ru–N(5) 2.023(4), Ru–N(9) 2.103(4), Ru–N(11) 2.107(4), Ru–
Cl(1) 2.451(1), Ru–B 3.120(5), N(10)–Cl(1) 3.243(5), N(12)–Cl(1) 3.282(5).
˚

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M. Onishi et al. / Inorganica Chimica Acta 359 (2006) 990–997
products, which were spectroscopically characterized as
[Ru{BH(3,5-Me2-4-Brpz)3}(3,5-Me2-4-Brpz)(3,5-Me2-4-Brp-
zH)2] (6) and [Ru{BH(3,5-Me2-4-Brpz)3}(3,5-Me2-4-
Brpz)(3,5-Me2-4-BrpzH)(PhCN)] (7). These new products
retain 3-Me-substituents on the metal-linking pyrazolyl
groups in the (j3-polypyrazolylborato) ruthenium moiety
‘‘Ru{BH(3,5-Me2-4-Brpz)3}’’, similarly to our previously
reported complex [RuCl2{BH(3,5-Me2pz)3(NO)}] [4c]. In
case of the reactions without addition of 3,5-Me2-4-BrpzH,
quantities of the (pyrazolato)bis(pyrazole) complex 6 were
small (less than 4% yields), and the (pyrazolato)(pyra-
by the Centre for Instrumental Analyses of Nagasaki
University.
3.2. Reactions of [RuCl{BR(pz)3}(PhCN)2] and
K[BH(3,5-Me2pz)3] to give [Ru{BR(pz)3}(3,5-Me2pz)
(3,5-Me2pzH)2] (1)
In
refluxing
benzene,
the
complex
[RuCl{B(pz)4}(PhCN)2] (110 mg, 0.18 mmol) was treated
with K[BH(3,5-Me2pz)3] (90 mg, 0.27 mmol) for 2 days.
On silica-gel column chromatography, the fraction eluted
by dichloromethane/diethyl ether (10/1) was collected to
give yellowish green powder of [Ru{B(pz)4}(3,5-
Me2pz)(3,5-Me2pzH)2] (1) (30 mg, 0.045 mmol) in 25%
yield.
zole)(benzonitrile)
7
was the sole major product,
infrequently accompanied by generation of a bis(benzonit-
rile) species of [RuCl{BH(3,5-Me2-4-Brpz)3}(PhCN)2] (8)
in significantly lower yields. These j3-BH(3,5-Me2-4-Brpz)3
half-sandwich rutheniums with the 3-Me-substituents in
their metal-linking pyrazolyl groups have readily replace-
able coexistent ligands, i.e., pyrazole, pyrazolato, and
benzonitrile, and in comparison with the BR(pz)3
complexes 1 and 2, their chemical reactivity studies are
further in progress.
Mp.; 210–225 ꢁC. 1H NMR (CDCl3); d 0.77 (s, 9H,
CH3), 2.46 (s, 9H, CH3), 5.70 (s, 3H, 4-H of 3,5-Me2pz),
6.08 (dd, J = 1.8 and 2.2, 3H, pz), 6.64 (dd, J = 1.5 and
2.2, 1H, pz), 6.96 (bs, 3H, pz), 7.90 (d, J = 2.5, 3H, pz),
8.01 (bs, 1H, pz), 8.19 (d, J = 2.2, 1H, pz). 11B NMR
(CDCl3); d ꢀ18.3 (s). MS (FAB); 669 for [M + 1]+. Anal.
Calc. for C27H35BN14Ru: C, 48.58; H, 5.28; N, 29.38,
Found: C, 48.30; H, 5.44; N, 29.20%.
2.3. Conclusion
Similar reaction of [RuCl{BH(pz)3}(PhCN)2] was per-
formed to afford yellowish green [Ru{BH(pz)3}(3,5-
Me2pz)(3,5-Me2pzH)2] (2) in 49% yield. Mp.; 176–194 ꢁC.
IR (KBr); 2476 cmꢀ1 for m(BH). 1H NMR (CDCl3); d
0.74 (s, 9H, CH3), 2.53 (s, 9H, CH3), 5.63 (s, 3H, 4-H of
3,5-Me2pz), 6.03 (dd, J = 2.0 and 2.4, 3H, pz), 6.83 (bs,
3H, pz), 7.76 (d, J = 2.4, 3H, pz), 13.5 (bs, 2H, NH). 11B
NMR (CDCl3); d ꢀ22.3 (d, J = 79). MS (FAB); 602 for
M+. Anal. Calc. for C24H33BN12Ru: C, 47.93; H, 5.53;
N, 27.94. Found: C, 47.78; H, 5.76; N, 27.85%.
(Pyrazolato)(pyrazole) ruthenium(II) complexes with j3-
polypyrazolylborates were separated, which involve
[Ru{BR(pz)3}(3,5-Me2pz)(3,5-Me2pzH)2] {R = pz (1),
H (2)}, [Ru{BH(3,5-Me2-4-Brpz)3}(3,5-Me2-4-Brpz)(3,5-
Me2-4-BrpzH)2] (6), and [Ru{BH(3,5-Me2-4-Brpz)3}
(3,5-Me2-4-Brpz)(3,5-Me2-4-BrpzH)(PhCN)] (7). More-
over, the derived tris(pyrazole) complex of [Ru{B(pz)4}
(3,5-Me2pzH)3]BF4 (3) was found to work as a novel halo-
geno-anion receptor. Single-crystal X-ray structural analy-
ses were carried out for 1, 3 Æ CHCl3, [Ru{B(pz)4}
(3,5-Me2pzH)2(OH2)]O3SC6H4CH3 Æ CH3OH (4 Æ CH3OH),
and [RuCl{B(pz)4}(3,5-Me2pzH)2] Æ CHCl3 (5 Æ CHCl3).
3.3. Preparation of [Ru{B(pz)4}(3,5-Me2pzH)3]BF4 (3)
from 1 and its further protonation
3. Experimental
To the dichloromethane solution of [Ru{B(pz)4}(3,5-
Me2pz)(3,5-Me2pzH)2] (16 mg, 0.023 mmol), diethyl ether
solution (50%) of HBF4 (3.4 ml, 0.023 mmol) was injected.
After 10 min stirring and solvent evaporation under vac-
uum, recrystallization of the residue from dichloromethane
and diethyl ether gave orange powder of [Ru{B(pz)4}(3,5-
Me2pzH)3]BF4 (3) (14 mg, 0.018 mmol) in ca. 75% yield.
1H NMR(CDCl3); d 1.16 (s, 9H, CH3), 2.54 (s, 9H,
CH3), 5.88 (s, 3H, 4-H of 3,5-Me2pz), 6.15 (bs, 3H, pz),
6.62 (bs, 3H, pz), 6.76 (bs, 1H, pz), 7.77 (bs, 3H, pz),
8.11 (bs, 1H, pz), 8.32 (bs, 1H, pz), 10.4 (bs, 3H, NH).
11B NMR (CDCl3); d ꢀ18.4 (s, B(pz)4), ꢀ19.2 (s, BF4).
MS (FAB); 669 for [M(cationic part)]+. Anal. Calc. for
C27H36B2F4N14Ru Æ 0.5CH2Cl2: C, 41.40; H, 4.67; N,
24.58. Found: C, 41.08; H, 4.95; N, 24.32%.
3.1. General procedures
Starting materials, such as potassium polypyrazolyl
borate salts [8] and trans-[RuCl2(PhCN)4] [16], were pre-
pared according to the literature methods. Solvents were
dried and distilled over appropriate drying agents. All
other reagents were purchased and used without further
purification. Under dry oxygen-free nitrogen atmosphere,
reactions were performed with using Schlenk flasks,
whereas column-chromatographic separations and han-
dling the starting materials and the products in solid state
were performed in air. Infrared (IR) spectra were recorded
on a JASCO FT-IR 420 spectrometer. NMR spectra were
obtained on a JEOL model JNM GX-400 spectrometer,
operating at 400 MHz (1H) and 128 MHz (11B) by the
use of tetramethylsilane as an internal standard and tri-
methyl borate as an external one, respectively. Elemental
analyses were performed on a Yanaco MT-3 CHN Cordre
The complex 1 in a NMR tube (CDCl3) was treated with
twofold moles of HBF4 (Et2O), and the NMR spectra
showed additional protonation of the uncoordinated pyraz-
olyl group in the B(pz)4 ligand. However, isolation of the
1
generated species was not succeeded. H NMR(CDCl3); d

M. Onishi et al. / Inorganica Chimica Acta 359 (2006) 990–997
995
1.44 (s, 9H, CH3), 2.43 (s, 9H, CH3), 5.91 (s, 3H, 4-H of 3,5-
Me2pz), 6.26 (bs, 3H, pz), 6.71 (bs, 3H, pz), 7.14 (bs, 1H,
pz), 7.55 (bs, 3H, pz), 8.48 (bs, 1H, pz), 8.97 (bs, 1H, pz),
10.0 (bs, 4H, NH). 11B NMR (CDCl3); d ꢀ18.4 (s,
B(pz)4), ꢀ19.6 (s, BF4).
C29H29BBr3ClN8Ru Æ CH2Cl2: C, 37.47; H, 3.25; N,
11.65. Found: C, 37.15; H, 3.79; N, 11.64%.
3.6. Single-crystal X-ray structural determinations
Crystallographic data are summarized in Table 1. Single
crystals for X-ray structural analyses were obtained as fol-
lows: [Ru{B(pz)4}(3,5-Me2pz)(3,5-Me2pzH)2] (1) by serene
built-up of two solvent layers, i.e., Et2O and 1-containing
CH2Cl2 layers in test tubes; [Ru{B(pz)4}(3,5-Me2pzH)3]
BF4 Æ CHCl3 (3 Æ CHCl3) by vapor diffusion of n-hexane
into 3-containing CHCl3 solution; [Ru{B(pz)4}(3,5-Me2pz-
H)2(OH2)]OTs Æ CH3OH (4 Æ CH3OH) by vapor diffusion
of Et2O and n-hexane into 1-containing CH2Cl2 solution
with equimolar p-toluenesulfonic acid monohydrate and
small amount of CH3OH; and [RuCl{B(pz)4}(3,5-Me2pz-
H)2] Æ CHCl3 (5 Æ CHCl3) by slow vapor diffusion of n-hex-
ane into 3-containing CHCl3 solution with equimolar
amount of [PPh4]Cl. These single-crystals were sealed in
glass capillaries, and X-ray diffraction observations were
carried out at 23 ꢁC on an automated Rigaku AFC-7S dif-
fractometer by using graphite-monochromated Mo Ka
3.4. Halogeno-anion incorporation with the tris(pyrazole)
species [Ru{B(pz)4}(3,5-Me2pzH)3]+
The complex 1 in dichloromethane was treated with
HBF4 (Et2O) in an equimolar quantity to produce 3. After
10 min stirring and evaporation in vacuo, the residue was
dissolved in CDCl3 and combined with the phosphonium
halides [Ph4P]X (X = Cl, Br, I) in prescribed quantities.
NMR and IR spectroscopic measurements were performed
for these solutions.
3.5. Reactions of K[BH(3,5-Me2-4-Brpz)3] with trans-
[RuCl2(PhCN)4]
The (benzonitrile) ruthenium(II) [RuCl2(PhCN)4]
(200 mg, 0.34 mmol) was treated with K[BH(3,5-Me2-4-
Brpz)3] (450 mg, 0.79 mmol) in benzene and the mixture
was heated with 3,5-Me2-4-BrpzH (300 mg, 1.71 mmol) un-
der reflux overnight. Benzene-extracted material was chro-
matographed on a silica-gel column, and benzene elution
gave off-white powder of [Ru{BH(3,5-Me2-4-Brpz)3}(3,5-
Me2-4-Brpz)(3,5-Me2-4-BrpzH)2] (6) (95 mg, 0.082 mmol)
in a 24% yield.
˚
(k = 0.7107 A) radiation.
For 1, diffraction intensity data were collected with the
four-circle goniometer and a NaI scintillation counter
[11b]: scan type, x–2h; scan width in x (deg, ꢁ),
0.68 + 0.30 tanh; scan rate in x (deg/min), 16.0.
For the remaining crystals, 3 Æ CHCl3, 4 Æ CH3OH, and
5 Æ CHCl3, intensity data were obtained on a MSC/ADSC
Quantum CCD area detector coupled with the AFC-7S dif-
fractometer. Seven preliminary data frames were measured
at 0.5ꢁ increments of x, in order to assess the crystal qual-
ity and preliminary unit cell parameters. The intensity
images were obtained with x scans of 0.5ꢁ interval per
frame for a duration of 35 s. The frame data were inte-
grated using an MSC d*TREK program package, and the
data sets were corrected for absorption using a REQAB
program.
1
Mp.; 155–165 ꢁC. IR (KBr); 2525 cmꢀ1 for m(BH). H
NMR (CDCl3); d 0.81 (s, 9H, CH3), 0.95 (s, 9H, CH3),
2.42 (s, 9H, CH3), 2.52 (s, 9H, CH3). MS (FAB); 1160
for M+. Anal. Calc for C30H39BBr6N12Ru: C, 31.09; H,
3.39; N, 14.50. Found: C, 31.36; H, 3.34; N, 13.96%.
Moreover, the benzene elution also afforded the
(pyrazolato)(pyrazole)(benzonitrile) complex [Ru{BH(3,5-
Me2-4-Brpz)3}(3,5-Me2-4-Brpz)(3,5-Me2-4-BrpzH)(PhCN)]
(7) (134 mg, 0.12 mmol) as yellow microcrystals in 36%
yield. Mp.; 150–160 ꢁC. IR (KBr); 2523 cmꢀ1 for m(BH),
The crystal structures were solved by direct methods
(SIR-92) [17] for 1, 3 Æ CHCl3, 4 Æ CH3OH, and by
heavy-atom Patterson method (DIR DIF 94 PATTY)
[18] for 5 Æ CHCl3, respectively, and further expanded
using Fourier techniques. The structures were refined
through full-matrix least squares method on F2 by the
Rigaku TEXSAN crystallographic package [19]. All
non-hydrogen atoms were refined anisotropically. Hydro-
gen atoms were placed at calculated positions with C–H
1
2217 for m(CN). H NMR (CDCl3); d 0.95 (s, 6H, CH3),
1.02 (s, 3H, CH3), 1.79 (s, 6H, CH3), 2.39 (s, 6H, CH3),
2.46 (s, 6H, CH3), 2.52 (s, 3H, CH3), 7.4–7.6 (c, 5H, Ph).
MS (FAB); 1087 for M+. Anal. Calc. for
C32H37BBr5N11Ru: C, 35.35; H, 3.43; N, 14.17. Found:
C, 35.63; H, 3.47; N, 13.88%.
Reactions in refluxing benzene without coexistence of
free pyrazole were undergone to give 7 and 6 in 43% and
2% yields, respectively, whereas analogous reactions in
dichloromethane and chromatographic separation with a
dichloromethane and diethyl ether solvent mixture (5/1)
infrequently afforded a brown bis(benzonitrile) species of
[RuCl{BH(3,5-Me2-4-Brpz)3}(PhCN)2] (8) additionally in
significantly low yields. IR (KBr); 2526 cmꢀ1 for m(BH),
˚
distance of 0.97 A, except NH hydrogens in ligating
pyrazoles of 1, 4 Æ CH3OH, and 5 Æ CHCl3, which were
located on the basis of the difference Fourier map and
refined isotropically. Four protons were not placed,
involving incorporated CHCl3 proton in 3 Æ CHCl3 and
OH protons of ligating OH2 and incorporated CH3OH
molecules in 4 Æ CH3OH. In addition, 2-N nitrogen
(N(6)) and 5-C carbon (C(8)) in the uncoordinated
pyrazolyl group of 1 were disordered with occupancy
factors of 0.5/0.5.
1
2220 for m(CN). H NMR (CDCl3); d 2.41 (bs, 9H, CH3),
2.55 (s, 3H, CH3), 2.74 (s, 6H, CH3), 7.48 (t, J = 7.5, 4H,
m-Ph), 7.59 (t, J = 7.4, 2H, p-Ph), 7.68 (d, J = 7.4, 4H,
o-Ph). MS (FAB); 878 for M+. Anal. Calc. for

996
M. Onishi et al. / Inorganica Chimica Acta 359 (2006) 990–997
Table 1
Crystal and structure refinement data
1g
3 Æ CHCl3
4 Æ CH3OH
5 Æ CHCl3
Empirical formula
Fw
C27H35N14BRu
667.55
C28H37N14B2Cl3F4Ru
874.74
C30H41N12BO5SRu
793.67
C23H29N12BCl4Ru
727.25
Crystal system
Space group
Color
orthorhombic
Pnma (# 62)
green
triclinic
triclinic
triclinic
ꢀ
ꢀ
ꢀ
P1 ð#2Þ
P1 ð#2Þ
P1 ð#2Þ
orange
orange
orange
Crystal size (mm)
Lattice parameters
0.15 · 0.15 · 0.30
0.40 · 0.30 · 0.15
0.35 · 0.20 · 0.10
0.40 · 0.20 · 0.15
˚
a (A)
26.196(4)
14.410(2)
8.019(3)
9.126 (3)
12.924 (4)
17.066 (6)
77.187 (6)
79.092 (3)
83.527 (3)
1922.0 (10)
2
11.433(1)
12.0351(8)
14.876(2)
80.872(3)
71.365(2)
72.341(1)
1843.8(3)
2
10.102(3)
10.851(2)
14.881(5)
78.156(5)
88.910(2)
75.264(1)
1543.0(8)
2
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
V (A )
3027(2)
4
1.465
5.62
Z value
qcalc (g/cm3)
1.511
6.78
1.429
5.37
1.565
8.91
l (Mo Ka) (cmꢀ1
)
Structure solution
direct method (SIR-92)
direct method (SIR-92)
8133
8095
409
0.101
0.197
0.245
1.69
direct methods (SIR-92)
7854
7802
459
0.056
0.102
0.131
1.40
Patterson methods (DIR DIF 94 Æ PATTY)
Number of unique reflections
Number of observationsa
Number of variables
3620
3619
230
0.038
0.068
0.090
1.31
6609
6586
378
0.059
0.109
0.151
1.07
b,c
R1
Rd
Rwe
Goodness-of-fit Sf
a
All data.
b
I > 2.0r(I).
P
P
c
d
e
f
R1 = iFoj ꢀ jFci/ jFoj.
P
P
R ¼ ðF 2o ꢀ F 2c Þ= F 2o.
P
P
2
2 1=2
Rw ¼ ½ wðF 2o ꢀ F c2Þ = wðF 2oÞ ꢂ
.
P
S ¼ ½ wðjF oj ꢀ jF cjÞ =ðNo ꢀ NvÞꢂ1=2, where No and Nv denote the number of observations and variables.
2
g
Scan type, x–2h; scan width in x (deg, ꢁ), 0.68 + 0.30 tanh; scan rate in x (deg/min), 16.0. See Section 3 in the text.
Acknowledgements
data associated with this article can be found, in the online
version, at doi:10.1016/j.ica.2005.08.005.
This work was supported by Grant-in-Aid for Scientific
Research on Priority Areas (No. 16033101, ‘‘Reaction
Control of Dynamic Complexes’’) from the Ministry of
Education, Culture, Sports, Science and Technology, Ja-
pan. The authors thank Emeritus Professor Katsuma Hir-
aki of this Department and Dr. Kazuto Ikemoto of
Mitsubishi Gas Chemical Company, Inc. (Tokyo), for their
useful suggestions. Technical assistance by Ms. Junko
Nagaoka, Ms. Yumi Kondoh, and Mr. Yuh-suke Itoh is
highly appreciated.
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