Insertion of alkynes into the heterocycle of (η5-pentaalkyl-2,3-dihydro-1,3-diborolyl)(η5 -pentamethylcyclopentadienyl)ruthenium: Formation and characterization of 4-borataborepine ruthenium complexes

Article abstract of DOI:10.1016/j.jorganchem.2009.01.025

The violet ruthenium complex [(η⁵-C₅Me₅)Ru(η⁵ -C₃B₂Me₄R¹)] (2a, R¹ = Me) reacts with terminal alkynes R²C{triple bond, long}CH to give yellow 4-b

Full text of DOI:10.1016/j.jorganchem.2009.01.025

Journal of Organometallic Chemistry 694 (2009) 1884–1889
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Insertion of alkynes into the heterocycle of (
g
5-pentaalkyl-2,3-dihydro-1,3-diborlyl)
(
g
5-pentamethylcyclopentadienyl)ruthenium: Formation and characterization
of 4-borataborepine ruthenium complexes
Yong Nie a,b, Hubert Wadepohl a, Chunhua Hu c, Thomas Oeser d, Walter Siebert a,
*
a Anorganisch-Chemisches Institut der Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
b School of Chemistry and Chemical Engineering, University of Jinan, 106 Jiwei Road, 250022 Jinan, PR China
c Institut für Anorganische Chemie, RWTH Aachen, Professor Pirlet Strasse 1, 5205Aachen, Germany
d Organisch-Chemisches Institut der Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
a r t i c l e i n f o
a b s t r a c t
The violet ruthenium complex [(g g
5-C5Me5)Ru( 5-C3B2Me4R1)] (2a, R1 = Me) reacts with terminal alkynes
Article history:
R2C„CH to give yellow 4-borataborepine compounds [( 5-C5Me5)Ru{ 7-(MeC)3(R1B)2(R2C2H)}] (4c,
g g
Received 25 November 2008
Accepted 16 January 2009
Available online 22 January 2009
R
1 = Me, R2 = Ph; 4d, R1 = Me, R2 = SiMe3; 4e, R1 = Me, R2 = H). The insertion of alkynes into the folded
C3B2 heterocycle of 2a causes some steric hindrance, which yields with elimination of the distant bor-
anediyl group the corresponding boratabenzene complexes 5 as byproducts. The analogous reactions
with internal alkynes R2C„CR2 proceed slowly and afford predominantly the boratabenzene complexes
Dedicated to Prof. Christoph Elschenbroich
on the occasion of his 70th birthday.
[(g g
5-C5Me5)Ru{ 6-(MeC)3(MeB)(R2C)2}] (5f, R2 = Et, 5g, R2 = p-tolyl), respectively. In the latter case, three
byproducts are formed: methylboronic acid and 1,2,3,4-tetra-p-tolyl-1,3-butadiene (9) due to hydrolysis
Keywords:
Boron
Heterocycle
Ring expansion
Ruthenium
of the postulated 2,3,4,5-tetra-p-tolyl-1-methylborole (10) and unexpectedly, the cationic triple-decker
complex [{(g l,g
5-C5Me5)Ru}2{ 7-(MeC)3(MeB)2(CH)2}]Cl (11) having two separated CH groups. The
new compounds were characterized by NMR, MS, and single-crystal X-ray studies of 4c, 5f, 9 and 11.
Ó 2009 Elsevier B.V. All rights reserved.
Sandwich complexes
1. Introduction
(angle < 20°) [3–4]. Phosphanes also form donor–acceptor com-
plexes 2 ꢀ PH2R (R = H, Ph), whereas t-butylphosphaalkyne P„C-
There has been considerable interest in electron-poor organo-
metallic compounds of the iron triad having fewer than 18 valence
electrons (VE). We have reported on formally 16 VE (
CMe3 is incorporated into 2a yielding a ruthenaphosphacarborane,
however, it is not known which of the isomers was formed [4].
Here we report on the reactivity of 2a toward terminal acetylenes
leading with insertion into the heterocycle to yield derivatives of
g
5-pentaalkyl-
2,3-dihydro-1,3-diborolyl)(
g
5-pentamethylcyclopentadienyl)iron
complexes 1 [1,2] and its violet ruthenium analogs 2 [3,4] (e.g. 2a:
R1 = Me). The unusual structural feature of the green iron complex
1 is the severe folding along the Bꢀ ꢀ ꢀB vector of the heterocycle
(g g
7-4-borata-borepine)( 5-pentamethylcyclopentadienyl)ruthenium
complexes 4, while with internal acetylenes boratabenzene com-
plexes are obtained. A preliminary account on the formation of 4
[8] as well as the investigation of its stacking with cationic metal
complex fragments to triple-decker complexes [11] have been
published.
(folding angle
a = 41.3°) causing a very short Fe–C2 bonding
(1.899 Å), as a result of the interaction of the combination of high-
lying (B–C) orbitals and the dxz orbital of iron. This bonding is
r
markedly different from other known 1,3-diborolyl sandwich struc-
tures. By spectroscopy, the violet ruthenium analogs 2 were as-
sumed to have a similar bonding situation [5–7], which was
recently confirmed by an X-ray diffraction study of 2b
(R1 = CH2SiMe3; folding along the Bꢀ ꢀ ꢀB vector:
a = 40.7°) [8–10]
and by the detailed electronic structure of 2 (DFT with the B3LYP
Ru
Fe
CO
R1
Ru
B
i-Pr
i-Pr
B
functional and extended triple-zeta basis sets) [10].
The ruthenium center of 2 reacts with donor ligands to yield
yellow complexes (e.g. 3) having reduced folding in the heterocycle
B
Et
B
B
R1
B
Et
R1
R1
3
1
2
* Corresponding author. Tel.: +49 6221 548485; fax: +49 6221 545609.
E-mail address: walter.siebert@urz.uni-heidelberg.de (W. Siebert).
0022-328X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2009.01.025

Y. Nie et al. / Journal of Organometallic Chemistry 694 (2009) 1884–1889
1885
2. Results and discussion
C18 C19
C21
C17
2.1. Formation of 4-borataborepineruthenium complexes 4c–e
C20
Reactions of 18 VE decamethyl-1,3-diboraruthenocene (2a)
with terminal alkynes (Scheme 1) in hexane lead to the yellow
complexes 4, which are characterized by NMR and MS data. (Sec-
tion 4) The 11B NMR spectra show broad signals at lower field
(d = 26–29 ppm, while that for 2a is at 21.7 ppm. In the EI mass
spectra the molecular ions at m/z = M+ exhibits a high stability
regarding a loss of the alkyne. However, signals at m/z = [MꢁBMe]+
indicate that the elimination of boranediyl leads to Cp*Ru(borata-
benzene) complexes 5. As byproducts the trimers of alkynes are
identified by MS. The molecular structures of 4a,b [8], and 4c have
been studied by single-crystal X-ray diffraction analyses which
confirm the presence of the sandwich complexes with 4-borata-
borepine ligands. The insertion of the alkyne into one of the equiv-
alent boron–carbon bonds of 2 yields enantiomers found in the
crystal structures.
Ru1
C10
C8
C9
B2
C2
C3
C5
C4
C1
C7
B1
C6
Fig. 1. Molecular structure of 4c. Hydrogen atoms have been omitted for clarity.
Selected bond lengths [Å] and angles [°]: Ru–Cp* 2.184(2)–2.196(2), Ru–B1
2.446(3), Ru–C1 2.310(2), Ru–C2 2.333(2), Ru–B2 2.456(3), Ru–C3 2.311(2), Ru–
C4 2.244(2), Ru–C5 2.319(2), B1–C1 1.524(3), C1–C2 1.412(3), B2–C2 1.525(4), B2–
C3 1.513(4), C3–C4 1.413(3), C4–C5 1.417(3), B1–C5 1.519(3); C5–B1–C1 124.2(2),
C2–C1–B1 129.4(2), C1–C2–B2 128.9(2), C3–B2–C2 124.5(2), C4–C3–B2 129.7(2),
C3–C4–C5 130.1(2), C4–C5–B1 129.6(2).
The seven-membered rings in 4a–c exhibit a reduced folding
along the Bꢀ ꢀ ꢀB vector (
almost parallel to the Cp* rings. The bonding between Ru center
and the large C5B2 ring causes the -atoms of its substituents more
or less to tilt toward the metal atom with the exception of -car-
a = 12, 26 and 15°, respectively), they are
a
a
bon at the boron atoms tilting in the opposite direction. Within
the seven-membered ring, the B–C bond lengths are between
1.513 and 1.545 Å, which indicates short B–C bonds. The C–C
bonds are very similar (1.409–1.417 Å). In 4b the Ru–B distances
of 2.527 and 2.542 Å are significantly elongated compared to those
in 4a (2.429 and 2.443 Å) and 4c, showing the influence of the
bulky Me3SiCH2 groups in 4b. The Ru–C bond distances in 4b vary
within a range of 2.203–2.345 Å, with Ru–C4 being the shortest to
the C5B2 ring (see Fig. 1).
The reactions of 2a with trimethylsilylacetylene and ethyne
(Scheme 1) give the yellow 4-borataborepine complexes 4d and
4e, respectively, and by MS studies the corresponding borataben-
zene complexes 5d and 5e as well as tris(trimethylsilyl)benzene
are detected as byproducts. The 1H NMR spectrum of compound
4e exhibits two doublets at d = 5.54, 4.56 ppm, which indicates
the two CH moieties remained adjacent in the 4-borataborepine
complex. An X-ray diffraction study of 4e confirms the incorpora-
tion of ethyne, however, the seven-membered ring is found to be
disordered. In an unexpected triple-decker complex cation the
bridging 4-borataborepine ligand contains two separate methyli-
dyne groups (see below).
when in contact with air. The donor function of the 4-boratabore-
pines may be conveniently divided into ene (2e) and allyl anion
(4e), separated by two boron atoms. The short boron–carbon bond
lengths in 4 indicate that the p2 and p4 systems are electronically
connected via the pz orbitals of boron atoms. Thus the 4-borata-
borepine ligand is electronically related to the tropylium ion
C7Hþ and the neutral borepine [12,13], respectively. Complexes 4
7
are isomers of the bis(6-boratabenzene)ruthenium complexes 6
[14] and structural analogs of (
tatrienyl)chromium [15].
g g
5-cyclopentadienyl)( 7-cyclohep-
The driving force for the fast alkyne insertion into the folded
heterocycle of complexes 2 is the formation of the 6 electron 4-
p
borataborepine ligand in the 18 VE complexes 4. It is assumed that
the alkyne coordinates weakly to the Ru atom, the substituent of
the alkyne being located near one of the boron atoms. Insertion
reactions of ethyne into one of the boratabenzene rings of bis(bora-
tabenzene)zirconium [16] and -titanium [17] complexes yield
compounds 7 and 8 having an 8a-H-4-boratanaphthalene and a
boratacyclooctatetraene as ligand, respectively.
In general, the yellow 4-borataborepine-ruthenium complexes
4 presented here are relatively stable in the solid state at ambient
temperatures. In solution they decompose slowly to give the corre-
sponding boratabenzene complexes 5, which is found to be faster
_
B R
B
R
R
B
Ti
Ru
Zr
B
R
R
B
B
R
6
7
8
R2C2H
Ru
Ru
B
Ru
+
R1
hexane
B
H
H
R1
2.2. Boratabenzene ruthenium complex 5f
B
B
B
R2
R1
R1
R1
R2
5
4
To study the formation of boratabenzene complexes 5a,b, the
stability of 4b in solution was monitored by 11B NMR. During a per-
iod of several weeks a weak signal at d = 16 ppm increased, indicat-
ing the formation of the boratabenzene complex 5b. The steric
influence of the substituents of R2C2 was tested in the reaction of
2a with bulky acetylenes. With 3-hexyne (Scheme 2) the borata-
benzene complex 5f is obtained and identified by 11B NMR
(d = 16.8 ppm), HR-MS, and by an X-ray diffraction study. Steric
2
2
a
c
d
e
b
4, 5
R1
Me Me Me R1
CH2SiMe3
Bn
Me
Bn
Ph SiMe3
H
R2
Scheme 1. Formation of borataborepine- and boratabenzene-ruthenium
complexes.

1886
Y. Nie et al. / Journal of Organometallic Chemistry 694 (2009) 1884–1889
+
Cl-
R2C2
C2Et2
- [:B-Me]
Ru
B
Ru
2a
Ru
B
or
Ru
+
[
]
10
+
Ru
2a
THF
H
B
(R = p-tolyl)
Et
Et
R
Et
B
B
B
B
Et
Et
Et
H
R
4f
5f
5f'
Ru
5g
11
Scheme 2. Formation of the boratabenzene complex 5f.
R
R
R
R
H
R
H O
2
2
H
R
B
R
MeB(OH)2
+
R
9
Me
10
Scheme 3. Reaction of 2a with di-p-tolylacetylene yields boratabenzene complex
5g, the triple-decker 11 and the intermediate borole 10, which hydrolyzed to give
the butadiene derivative 9 and MeB(OH)2.
corresponding boracyclopropene. During the reaction or work-up
(extraction/crystallization in CH2Cl2) hydrolysis [19] of 10 with
adventitious water resulted in the formation of 9 and methylboronic
acid. The HR-MS data of the yellow crystals indicated the novel
triple-decker cationic species 11 which was confirmed by an
X-ray structure analysis. The bridging seven-membered ligand
unexpectedly contained two CH groups separated by a CMe moiety
(Fig. 3). At this point attempts to illuminate its formation were not
successful.
The crystal structure is comprised of layers of triple-decker cat-
ions on the one hand, and hydrogen bonded dimers of methylboron-
ic acid and chloride anions, respectively, on the other. The cation 11
has crystallographic mirror symmetry with the mirror plane bisect-
ing the borataborepine and pentamethylcyclopentadienyl ligands.
In contrast to the seven-membered rings in 4, the borataborepine li-
gand in 11 is planar, with the largest deviation being 0.01 Å. The
three ring ligands are essentially coplanar (interplane angle ꢂ 1°),
and the Ruꢀ ꢀ ꢀRu distance is 3.34 Å, which is similar to the recently
characterized cationic triple-decker complexes with a bridging
Fig. 2. Molecular structure of 5f, hydrogen atoms have been omitted for clarity.
Selected bond lengths [Å]: Ru1–Cp* 2.171(3)–2.181(3), Ru1–C11 2.256(3), Ru1–C12
2.262(3), Ru1–C13 2.262(3), Ru1–C14 2.220(3), Ru1–C15 2.232(3), Ru1–B16
2.257(3), C11–C12 1.436(4), C12–C13 1.468(4), C13–C14 1.469(4), C14–C15
1.436(4), C15–B16 1.458(4), C11–B16 1.470(4).
requirements in the anticipated peralkylated complex 4f cause a
fast elimination of one methylboranediyl moiety [:B–Me], whereas
4a,b eliminate the [:B–R1] unit slowly in solution. Of the possible
isomers only 5f with the boron atom adjacent to the inserted
C2Et2 is isolated. The boratabenzene ring is essentially planar (tor-
sion angle C13–C14–C15–B16: ꢁ1.3°) as in reported borataben-
zene complexes [18]. The bond lengths of C11–B16/C15–B16
[1.470(4) and 1.458(4) Å, respectively] and C12–C13/C13–C14
[1.468(4) and 1.469(4) Å, respectively] are slightly longer that
those of C11–C12/C14–C15 [1.436(4) and 1.436(4) Å, respectively]
and the Ru–C13/Ru–B16 bond distances [2.262(3) and 2.257(3) Å,
respectively] are comparable with those of the other Ru–C dis-
tances within the boratabenzene ring [2.220(3)–2.262(3) Å]. This
indicates that the boratabenzene ring in 5f is disordered at the
B16/C13 symmetrically equivalent positions (see Fig. 2).
2.3. Unexpected formation of the triple-decker 11 with a bridging C5B2
ligand
To further investigate the influence of the steric requirements on
the formation of the boratabenzene complexes the reaction of 2a
and di-p-tolylacetylene (Scheme 3, 1:1 molar ratio) was carried
out. The insertion of the bulky acetylene proceeds slowly, yielding
a red THF solution. After removal of the solvent the red-brown res-
idue is extracted with toluene leaving a yellow residue (ca. 10 mg).
The oily extract was found to be a mixture of the boratabenzene
complex 5g (identified by 11B NMR and HR EI-MS) and 1,2,3,4-tet-
ra-p-tolyl-1,3-butadiene (9) (identified by an X-ray diffraction anal-
ysis). Its formation may have occurred as a result of the elimination
of [:BMe] from the expected 4g and its reaction with di-p-tolylacet-
ylene leading to 2,3,4,5-tetra-p-tolyl-1-methyl-borole 10 via the
Fig. 3. Molecular structure of the triple-decker cation 11. Hydrogen atoms are
omitted for clarity. Selected bond lengths [Å] and angles [°]: C1–C2, 1.408(4); B1–
C2, 1.527(5); B1–C3, 1.530(5); C3–C3a, 1.417(6); Ru1/Ru2–C1, 2.363(5)/2.382(5);
Ru1/Ru2–C2, 2.340(3)/2.329(3); Ru1/Ru2–B1, 2.405(3)/2.413(3); Ru1/Ru2–C3,
2.418(3)/2.423(3),
Ru1–C(Cp*),
2.150(4)ꢀ ꢀ ꢀ2.162(3);
Ru2–C(Cp*),
2.156(3)ꢀ ꢀ ꢀ2.158(4); C2–C1–C2a, 125.8(4); C1–C2–B1, 133.5(3); C2–B1–C3,
124.1(3); B1–C3–C3a, 129.6(2).

Y. Nie et al. / Journal of Organometallic Chemistry 694 (2009) 1884–1889
1887
borataborepine ligand [11] obtained by stacking experiments of the
two @CMe moieties n.o. EI-MS: m/z (%) = 471 [M+] (30), 446
1H3611B2102Ru:
12
sandwich [(
g
5-C5Me5)Ru{
g
7-(MeC)4(MeB)2(CH)}] with cationic
[M+ꢁBCH3 + 1] (100). HR-MS: m/z calcd. for
C
26
Cp*M complex fragments. Interestingly, the anion Clꢁ bridges two
dimeric MeB(OH)2 molecules, forming an infinite chain by hydrogen
bonding (O–Hꢀ ꢀ ꢀO, O–Hꢀ ꢀ ꢀCl).
472.2048, found: 472.2049, D = 0.1 mmu. EI-MS for 5c: m/z
(%) = 446 [M+] (100). HR-MS: m/z calcd for
446.1719, found: 446.1739, = 2.0 mmu.
C
25
1H3311B102Ru:
12
D
Compound 11 is the first structurally characterized triple-deck-
er complex having the borataborepine ring as bridging ligand [9].
An early example of an analogous triple-decker from the reaction
of CpCo(C2H4)2 with 1,4-dimethyl-2,3-diethyl-1,4-diboracyclohep-
ta-2-ene [20] was identified by MS data as [bis(cyclopentadienyl-
cobalt)C5B2] triple-decker complex [21].
4.2. (g
5-Pentamethylcyclopentadienyl)( 7-1,2,3,4,5-pentamethyl-7-
g
trimethylsilyl-4-borataborepine)ruthenium (4d)
A solution of trimethylsilylacetylene (43 mg, 0.44 mmol) in
hexane (10 mL) was added to a solution of 2a (140 mg, 0.38 mmol)
in hexane (10 mL) at ꢁ60 °C. No immediate color change was ob-
served, and the mixture was warmed to r.t., during which time
the solution turned from violet to brown and finally yellow and a
small amount of precipitate appeared. After filtration, the yellow
filtrate was dried in vacuo to give a yellow solid, identified to be
a mixture of 4d and 5d (byproduct), recrystallization in CH2Cl2 at
r.t. gave crystalline 4d, mp 110–120 °C (160 mg, 89%). The EI-MS
of the yellow precipitate (ca. 10 mg) did not provide clear informa-
tion. 1H NMR (CD2Cl2): d = 5.82 (s, 1H; allyl), 1.97 (s, 3H; BCCH3CH),
1.89 (s, 6H; @CCH3), 1.54 (s, 15H; C5(CH3)5), 0.74 (s, 3H; BCH3), 0.60
(s, 3H; BCH3), 0.11 (s, 18H; SiMe3) ppm; 11B NMR (CD2Cl2): d = 28.1
(br.) ppm; 13C NMR (CD2Cl2): d = 115.7 (allyl moiety, center car-
bon), 86.5 (C5(CH3)5), 27.9 (BCCH3CH), 21.7, 21.3 (@CCH3), 9.8
(C5(CH3)5), 0.7 (SiMe3) ppm. Signals for boron-bound carbon atoms
of the allyl moiety n.o.; 29Si NMR (CD2Cl2, 39.7 MHz): d = ꢁ21.7. EI-
MS: m/z (%) = 467 [4d+] (42), 394 [4d+ꢁSiMe3] (100), 379
3. Conclusion
The unique bonding properties of the decamethyl-1,3-diboraru-
thenocene (2a) allow the insertion of alkynes into its folded C3B2
ligand to yield 18 VE 4-borataborepine ruthenium complexes 4.
The anion of the C5B2 heterocycle functions as 6e donor. Steric
crowding of the inserted alkynes causes elimination of one bor-
anediyl group with the formation of boratabenzene complexes 5,
which are directly obtained in the reaction with disubstituted
acetylenes. The insertion of ethyne occurs into one of the two
equivalent boron–carbon bonds of the B–C–B group is confirmed
by an X-ray structure analysis of 4e, however, its seven-membered
ring is distorted. The slow reaction of di-p-tolylacetylene with 2a
leads to the expected boratabencene complex and a yellow product
in minute amount. Its X-ray diffraction data indicates the forma-
tion of the cationic triple-decker 11 which surprisingly contains
two separated CH groups. Hydrolysis of the postulated tetra-p-to-
lyl-1-methyl-borole (10) leads to the tetra-p-tolyl-butadiene 9 and
methylboronic acid, identified by X-ray structure analyses; the lat-
ter formed with the chloride anion of the triple-decker cation 11 an
infinite chain.
[4d+ꢁSiMe3ꢁMe] (39); 442 [5d+] (100), 427 [5d+ꢁCH3] (22), 369
[5d+ꢁSiMe3] (39). HR-MS: m/z calcd for
C
23
1H4028Si11B2102Ru:
12
468.2129, found: 468.2133,
D
= 0.4 mmu; m/z calcd. for
C
22
1H3711B28Si 102Ru: 442.1801, found: 442.1802,
D = 0.1 mmu.
12
For 5d: in a CH2Cl2 solution at r.t. 4d slowly transformed into 5d.
1H NMR (CD2Cl2): d = 4.90 (s, 1H; aromatic), 1.95 (s, 3H; BCCH3),
1.64 (s, 15H; C5(CH3)5), 1.58 (s, 6H; BCCH3), 0.42 (s, 3H; BCH3),
0.08 (s, 18H; SiMe3) ppm; 11B NMR (CD2Cl2): d = 17.5 (br.) ppm;
13C NMR (CD2Cl2): d = 109.4, 101.5, 95.3, 87.7 (boratabenzene ring
carbon atoms), 85.9 (C5(CH3)5), 19.6 (BCCH3), 16.2 (BCCCH3), 10.1
(C5(CH3)5), 0.7 (SiMe3) ppm. Signals for the other carbon atoms n.o.
4. Experimental
General. All reactions and manipulations were performed in dry
glassware under argon or nitrogen using standard Schlenk tech-
niques. Unless otherwise stated, solvents were dried, distilled, and
saturated with nitrogen. NMR spectra were recorded on a Bruker
DRX 200 spectrometer (1H: 200.13 MHz, 11B: 64.21 MHz, 13C:
50.32 MHz) in CDCl3 and CD2Cl2 as solvents. Et2O ꢀ BF3 was used as
external standard for 11B NMR. As internal references for 1H and
13C NMR, the signals of the deuterated solvents were used, the shifts
were calculated relative to TMS and given in ppm. MS: ZAB-2F VH
Micromass CTD and JEOL MS Station JMS 700 spectrometers.
4.3. (g
5-Pentamethylcyclopentadienyl)(
g
7-1,2,3,4,5-pentamethyl-4-
borataborepine)ruthenium (4e)
Acetylene was bubbled into
a
solution of 2a (143 mg,
0.39 mmol) in hexane (10 mL) at ꢁ60 °C. In a few seconds the solu-
tion turned from violet to yellow with the formation of a small
amount of precipitate. It was stirred at that temperature for
15 min. and then warmed to r.t. and filtered. The yellow filtrate
was dried in vacuo to give a yellow solid, which was identified to
be a mixture of 4e and 5e (byproduct). Recrystallization in CH2Cl2
at r.t. gave yellow crystals of 4e, mp 136–138 °C (130 mg, 86%). The
yellow residue (ca. 15 mg) was dissolved in minimum CH2Cl2 at
r.t., and yellow crystals were grown and identified by EI-MS to
be the boratabenzene complex 5e. The cell parameter determina-
tion indicated that it was different from 4e, however, the quality
of the crystal was not good enough for further determination. 1H
NMR (CD2Cl2): d = 5.54 (d, 2J(H,H) = 10.4 Hz, 1H; CH), 4.56 (d,
2J(H,H) = 10.6 Hz, 1H; CH), 1.97 (s, 3H; BCCH3), 1.90 (s, 3H, @CCH3),
1.89 (s, 3H, @CCH3), 1.58 (s, 15H; C5(CH3)5), 0.71 (s, 3H; BCH3),
0.68(s, 3H; BCH3) ppm. 11B NMR (CD2Cl2): d = 26.0 (br.) ppm. 13C
NMR (CD2Cl2): d = 115.1 (CH, allyl moiety), 86.8 (C5(CH3)5), 26.9
(BCCH3CH), 22.0, 20.8 (BC@CCH3), 9.2 (C5(CH3)5) ppm. Signals for
boron-bound ring carbon atoms n.o. EI-MS: m/z (%) = 395 [M+]
4.1. (g g
5-Pentamethylcyclopentadienyl)( 7-1,2,3,4,5-pentamethyl-7-
phenyl-4-borata-borepine)ruthenium (4c)
A solution of phenylacetylene (65 mg, 0.64 mmol) in hexane
(5 mL) was added to a violet solution of 2a (180 mg, 0.49 mmol)
in hexane (10 mL) at ꢁ60 °C. Within 10 min. the reaction mixture
turned to an orange red solution. It was warmed to r.t. and filtered
to give a yellow precipitate and a yellow filtrate. The filtrate was
dried in vacuo to yield a yellow solid, and recrystallization in
CH2Cl2 at r.t. gave yellow crystals of 4c (164 mg, 71%). The yellow
precipitate (ca. 15 mg) was identified by EI-MS to be the borata-
benzene complex 5c. 1H NMR (CDCl3): d = 7.19–7.42 (m, 5H; Ph),
5.80 (s, 1H; allyl), 2.04 (s, 3H; @CCH3), 2.02 (s, 3H; @CCH3), 1.97
(s, 3H; BCCH3CH), 1.53 (s, 15H; C5(CH3)5), 0.68 (s, 3H; BCH3),
0.62(s, 3H; BCH3) ppm. 11B NMR (CDCl3): d = 26 (br.) ppm. 13C
NMR (CDCl3): d = 130.8, 129.7, 126.9, 124.8 (Ph), 114.9, (allyl moi-
ety, center carbon), 86.5 (C5(CH3)5), 21.7 (BCCH3CH), 9.7 (C5(CH3)5)
ppm. Signals for boron-bound carbon atoms of the allyl, BCH3 and
(100), 355 [M+ꢁBCH3ꢁCH2] (74). HR-MS: m/z calcd. for
C
20
1H3211B2102Ru: 396.1733, found: 396.1747,
D = 1.4 mmu.
12
12
HR-MS of 5e: m/z calcd. for
370.1428, = 2.2 mmu.
C
1H2911B102Ru: 370.1406, found:
19
D

1888
Y. Nie et al. / Journal of Organometallic Chemistry 694 (2009) 1884–1889
Table 1
X-ray data and refinement details for 4c, 5f, 9 and 11.
4c
5f
9
11
Empirical formula
Formula weight
T (K)
Crystal system
Space group
a (Å)
C26H36B2Ru
471.24
120(2)
Monoclinic
P21/n
10.145(2)
14.508(3)
16.007(3)
90
102.198(3)
90
2302.9(7)
4
C23H37BRu
C32H30
414.56
100(2)
Monoclinic
C2/c
20.8374(16)
5.7266(5)
20.2349(16)
90
101.081(2)
90
2369.6(3)
4
0.065
C32H57B4ClO4Ru2
786.61
100(2)
Monoclinic
P21/m
10.2105(5)
16.7306(8)
10.9882(6)
90
106.754(1)
90
1797.4(2)
2
425.41
200(2)
Triclinic
ꢀ
P1
7.6752(9)
8.928(1)
16.051(2)
92.905(2)
93.060(2)
104.370(2)
1061.6(2)
2
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
V (Å3)
Z
l
(Mo K
a
) (mmꢁ1
)
0.690
0.74
0.948
Crystal size (mm)
Hmax (°)
0.44 ꢃ 0.24 ꢃ 0.18
0.28 ꢃ 0.11 ꢃ 0.05
0.15 ꢃ 0.15 ꢃ 0.10
0.20 ꢃ 0.13 ꢃ 0.05
28.3
26.4
30.5
32.0
Index ranges h, k, l
Reflections collected
Reflections unique [R(int)
No. of parameters
GOF
ꢁ13/13, ꢁ16/19, ꢁ21/21
22869
5744 (0.0388)
272
ꢁ9/8, ꢁ11/11, ꢁ20/20
6546
4077 (0.0193)
237
ꢁ29/28, 0/8, 0/28
10445
3612 (0.0410)
176
ꢁ15/14, 0/24, 0/16
31708
6348 (0.0599)
217
]
1.04
1.09
1.02
1.03
R(F) [Fo > 4
wR(F2) (all reflections)
Residual electron density (e Åꢁ3
r
(Fo)]
0.0311
0.0805
0.86/ꢁ0.33
0.031
0.0823
0.48/ꢁ0.31
0.0542
0.1567
0.40/ꢁ0.31
0.040
0.1039
1.94/ꢁ2.24
)
4.4. (
g
5-Pentamethylcyclopentadienyl)(
g
6-1,2,3,4-tetramethyl-5,6-
The yellow filtrate was dried to give a yellow oil (160 mg, the sig-
nal in the 11B NMR spectrum at d = 31.5 ppm gradually disappeared
and new peaks appeared at d = 14.6 (5g) and ca. ꢁ0.1 ppm). In addi-
tion, 1,2,3,4-tetra-p-tolyl-1,3-butadiene (9) was identified by an X-
ray diffraction analysis after recrystallization from CH2Cl2 at r.t.. 5g:
diethylboratabenzene) ruthenium (5f)
A solution of 3-hexyne (75 mg, 0.91 mmol) in hexane (10 mL)
was added to a solution of 2a (179 mg, 0.49 mmol) in hexane
(6 mL) at ꢁ60 °C. The mixture was warmed to r.t. and stirred for
additional 2 h, no clear color change was observed. The solution
was cooled to ꢁ50 °C and another portion of 3-hexyne (80 mg,
0.98 mmol) was added, warmed up and stirred overnight, during
which time it became a light red solution. The solution was dried
in vacuo to give a yellow brown oily residue, and recrystallization
in CH2Cl2 at r.t. gave crystalline 5f (180 mg, 87%). 1H NMR
(C6D6): d = 2.25 (m, 4H; CH2), 1.9 (m, 4H; CH2), 1.75 (s, 6H, BCCH3),
1.65 (s, 3H, CCH3), 1.45 (s, 15H; C5(CH3)5), 0.80 (s, 3H; BCH3) ppm;
11B NMR (C6D6): d = 16.4 (br.) ppm. 13C NMR (C6D6): d = 86.3
(C5(CH3)5), 25.0 (BCCH3), 17.4, 16.4, 15.4, 15.0, 14.8 (Et and
EtCCH3), 9.5 (C5(CH3)5) ppm. Signals for the boratabenzene ring
11B NMR (d = 14.6 ppm); EI-MS: m/z (%) = 549 [M+] (100). HR-MS:
12
m/z calcd. for
= ꢁ0.7 mmu.
C
33
1H4111B102Ru: 550.2345, found: 550.2338,
D
4.6. X-ray crystallography
Intensity data were collected at low temperature on Bruker
Apex (4c, 5f) and Bruker AXS Smart 1000 CCD diffractometers
(9, 11) (Mo Ka radiation, k = 0.71073 Å, graphite monochromator).
Data were corrected for air and detector absorption, Lorentz and
polarization effects, [22] absorption by the crystal was treated
with a semiempirical multiscan method [23,24]. The structures
were solved by conventional direct methods [25,26] and refined
by full-matrix least squares methods based on F2 against all un-
ique reflections.[26,27] All non-hydrogen atoms were given aniso-
tropic displacement parameters. Hydrogen atoms were generally
input at calculated positions and refined with a riding model.
Most hydrogen atoms in 9 (except those of the methyl groups)
were taken from difference Fourier syntheses and refined (see
Table 1).
carbon n.o. EI-MS: m/z (%) = 425 [M+] (100), 410 [M+ꢁCH3] (12),
395 [M+ꢁ2CH3] (15). HR-MS: m/z calcd for
C
1H3711B2102Ru:
23
12
426.2031, found: 426.2023,
D
= ꢁ0.8 mmu.
4.5. Reaction of 2a with di-p-tolylacetylene
A solution of di-p-tolylacetylene (78 mg, 0.38 mmol) in THF
(5 mL) was added to a solution of 2a (140 mg, 0.38 mmol) in
hexane/THF (4 + 3 mL) at ꢁ50 °C. The mixture was warmed to
r.t. and stirred overnight (no color change could be observed,
11B NMR: d = 31.5 ppm), and then for additional 2 d. The resulting
deep red solution was dried, and the dark oily residue was ex-
tracted with dry toluene and filtered. The yellow residue isolated
(ca. 10 mg) was recrystallized from CH2Cl2 at r.t. to give crystal-
line 11.
5. Supplementary material
CCDC 704900, 256654, 704901 and 704902 contain the supple-
mentary crystallographic data for 4c, 5f, 9 and 11. These data can
be obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
11: HR-MS (EI): m/z (%) = 633.1968 [M+] (100). Calcd. for
C
30
1H4711B2102Ru2: 633.1952. Replacement of the ring CH groups
12
Acknowledgements
by either two oxygen atoms or one CH by one oxygen atom has the
following formulae (calcd. formula weight):
Ru2 (639.1693);
son has helped the X-ray crystallographic analysis to assign the
two CH groups, since the alternative assignments did not find suit-
able HR-MS peaks within experimental error.
12
102
C
28
1H4511B216O2
1H4611B216O102Ru2 (636.1822). This compari-
12
This work was supported by the Deutsche Forschungsgemein-
schaft. We thank Prof. Dr. U. Englert for arranging X-ray diffraction
analyses in Aachen and Prof. Dr. L.H. Gade for generous support.
Y.N. acknowledges the University of Jinan for support.
C
29

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