Ruthenium-capping of di- and tetraethynylbiphenyls

Article abstract of DOI:10.1002/1099-0682(200109)2001:9<2305::AID-EJIC2305>3.0.CO;2-T

The di- and tetraalkynyl biphenyls 3 and 5 have been synthesized from the tetrabromo derivative 1 by using Pd-catalyzed cross-coupling reactions. The reaction of 3 or 5 with cis-[RuCl₂(dppe)₂] (8) affords vinylidene ruthenium complexes, which were deprotonated with Et₃N to give the terminal σ-alkynylruthenium derivatives 9-12. The reaction of 3 or 5 with [Ru(CO)ClH(PPh₃)₃] (13) gave the corresponding di-σ-alkenyl ruthenium complexes 14 and 15.

Full text of DOI:10.1002/1099-0682(200109)2001:9<2305::AID-EJIC2305>3.0.CO;2-T

FULL PAPER
Ruthenium-Capping of Di- and Tetraethynylbiphenyls
[a]
[a]
[a]
[b]
´
Berta Gomez-Lor, Amelia Santos,* Marta Ruiz, and Antonio M. Echavarren*
Keywords: Ruthenium / Vinylidene complexes / Hydrido complexes / Alkynes
The di- and tetraalkynyl biphenyls 3 and 5 have been syn-
plexes, which were deprotonated with Et3N to give the ter-
thesized from the tetrabromo derivative 1 by using Pd-cata- minal σ-alkynylruthenium derivatives 9−12. The reaction of
lyzed cross-coupling reactions. The reaction of 3 or 5 with 3 or 5 with [Ru(CO)ClH(PPh3)3] (13) gave the corresponding
cis-[RuCl2(dppe)2] (8) affords vinylidene ruthenium com-
di-σ-alkenyl ruthenium complexes 14 and 15.
Introduction
Carbon-rich organometallics containing rigid conjugated
branches have attracted great attention, since they are po-
tentially useful for building carbon-rich networks,[1] or-
ganometallic polymers[2] and π-conjugated polymetallic sys-
tems,[3] which can all find applications in material science.
Of special interest are the σ-alkynyl complexes, since they
allow electronic communication between coordinated metal
centers through the CϵC bonds in the π-conjugated sys-
tems. Indeed, a number of alkynyl complexes have been de-
signed for use in nonlinear optics[4] and as liquid crystals.[5]
Polyethynylated complexes may form organometallic poly-
mers in which the metal binds two ethynyl groups.[4b,5c,6]
Polymetallic compounds with -(CϵC)n- or polyethynylben-
zene bridges have also been studied.[3,4b,4c,5c,7] Other di- or
trimetallic alkynyl complexes have been prepared from ethy-
nyl ferrocene.[8] Additionally, alkynyl derivatives have given
rise to mixed-valence systems,[9] and organometallic macro-
cycles[10] have also been prepared.
The assembly of carbon-rich two- or three dimensional
nanomaterials from ethynylated scaffolds has also attracted
great attention.[11,12] Major achievements in this field are
the preparation of tetraethynylmethane (I),[13] tetraethynyle-
thene,[14] hexaethynylbenzene,[15] and π-metal complexes of
tetraethynylcyclobutadiene,[16] and pentaethynylcyclopenta-
diene.[17] Tetraethynylallene (II), topologically related to the
tetraalkyne I, still remains an elusive target. The biphenyls
III[18] and IV, which display the four alkynes in a flexible
elongated tetrahedral arrangement, could offer a potential
alternative to I and II (Scheme 1).
Scheme 1
Herein we report the synthesis of alkynes 3 and 5 as new
potential building blocks for the construction of carbon-
rich networks,[19] and their reactions with the ruthenium
complexes cis-[RuCl2(dppe)2] (8) [dppe ϭ 1,2-bis(diphenyl)-
phosphanylethane] and [Ru(CO)ClH(PPh3)3] (13), which
afford mono- and di-alkynyl and di-alkenyl ruthenium com-
plexes, respectively, in good yields.[20]
Results and Discussion
Synthesis of Di- and Tetraalkynylbiphenyls
The synthesis of alkynes 3 and 5 was based on palladium-
catalyzed transformations as the key steps. The tetrabromo
diester 1 was readily obtained from 2,2Ј-biphenol by brom-
ination with excess bromine in methanol at 23 °C,[21] fol-
lowed by acylation with pivalic anhydride (95% overall
yield). Thus, Sonogashira coupling[22] of tetrabromo dipiv-
alate ester (1) with excess trimethylsilylacetylene
{[PdCl2(PPh3)2] and CuI catalysts (20 mol % each), Et3N,
70 °C, 48 h] led to 2 (89% yield). No further coupling be-
tween 2 and trimethylsilylacetylene took place through the
more hindered o-bromides by using this coupling proced-
ure, even under severe conditions (Scheme 2).
[a]
Instituto de Ciencia de Materiales de Madrid, CSIC,
Cantoblanco, 28049 Madrid, Spain
E-mail: amelia.santos@icmm.csic.es
[b]
´
´
´
Departamento de Quımica Organica, Universidad Autonoma
de Madrid,
Cantoblanco, 28049 Madrid, Spain
Fax: (internat.) ϩ34-91/397-3966
E-mail: anton.echavarren@uam.es
Eur. J. Inorg. Chem. 2001, 2305Ϫ2310
WILEY-VCH Verlag GmbH, 69451 Weinheim, 2001
1434Ϫ1948/01/0909Ϫ2305 $ 17.50ϩ.50/0
2305

´
B. Gomez-Lor, A. Santos, M. Ruiz, A. M. Echavarren
FULL PAPER
Scheme 3. a: NaOH, MeOH, 23 °C, 18 h (80%); b: [Pd(PPh3)4] (20
mol %), CuI (20 mol %), pyrrolidine, 23 °C, 3 h (83%)
Scheme 2. a: [PdCl2(PPh3)2] (20 mol %), CuI (20 mol %), Et3N, 70
°C, 48 h (89%); b: K2CO3, MeOH, 23 °C, 30 min. (90%); c:
[Pd(PPh3)4] (20 mol %), toluene, reflux, 4 h (90%); d: K2CO3,
MeOH, 23 °C, 30 min. (95%); e: [Pd(PPh3)4] (20 mol %), toluene,
reflux, 4 h (92%)
version of the starting alkynes into a mixture of two ruth-
enium complexes. On the basis of the spectroscopic data
and literature precedent,[25Ϫ27] these products were tentat-
ively assigned as the monovinylidene and η2-alkyne ruth-
enium complexes. Thus, the IR spectra show relatively in-
tense bands in the range 1625Ϫ1630 cmϪ1, characteristic of
the vinylidene ruthenium complexes. However, the 1H
NMR spectra were complex, suggesting that isomeric (η2-
alkyne)ruthenium complexes were also present in solution.
These complexes decompose readily in the presence of dis-
solved oxygen or water to furnish the carbonyl complex
[Ru(CO)Cl(dppe)2]PF6 almost quantitatively. This ruth-
However, by using the Stille coupling[23] the four brom-
ides could be efficiently replaced by alkynyl substituents in
a single step. Thus, coupling of 1 with (trimethylsilylethynyl)-
tributylstannane[24] in the presence of [Pd(PPh3)4] as cata-
lyst gave the tetraalkynyl derivative 4 (90% yield) as a stable
colorless oil. The biphenyl 4 was also obtained by the coup-
ling of dibromide 2 with (trimethylsilylethynyl)tributylstan-
nane under the same conditions (92% yield). The terminal
alkynes 3 and 5 could be obtained by standard deprotection
of the TMS groups with K2CO3 in MeOH in 90 and 95%
yields, respectively. The pivaloyl groups of 5 could be effici-
ently removed under stronger basic conditions [NaOH,
MeOH, 23 °C, 18 h, 80%] to yield the biphenol 6. This com-
pound could undergo self-condensation by copper- or pal-
ladium-catalyzed alkyneϪalkyne coupling to furnish three
dimensional polymers bearing hydrophilic cavities.
While alkynes 3 and 5 are stable compounds that can be
stored under ordinary conditions, alkyne 6 undergoes slow
decomposition as a solid. However, it can be easily manip-
ulated and stored in the dark without significant decom-
position. The potential utility of these tetraethynylbiphenyls
as tectons for the building of more complex structures relies
upon their ability to couple with appropriate electrophiles.
Thus, the coupling of 5 with iodobenzene (4 equiv.) af-
forded 7 [Pd(PPh3)4 and CuI (20 mol % each), pyrrolidine,
23 °C, 3 h, 83%; Scheme 3].
1
enium(II) complex was characterized by IR and H NMR
spectroscopy and by the determination of the crystal struc-
ture.[28,29] Similar transformations of vinylidene- or allenyli-
dene complexes into their carbonyl derivatives have been
reported previously.[30]
The crude mixtures containing the monovinylidene and
η2-alkyne isomers were readily deprotonated with Et3N in
CH2Cl2 at room temperature to give the corresponding
monoalkynyl complexes 9 (72%) and 10 (74%), respectively.
Similarly, reaction of 3 and 5 with two equivalents of cis-
[RuCl2(dppe)2] (8) and four equivalents of KPF6 for seven
days at room temperature, followed by deprotonation, fur-
nished the dialkynyl ruthenium complexes 11 (72%) and 12
(85%) (Scheme 4).
Crystals of complexes 11 and 12 could be obtained, al-
though the crystal structure determination could not be
performed due to their decomposition by the X-rays. The
IR spectra of all these alkynyl complexes are very similar
and show very strong ν(CϵC) bands around 2050 cmϪ1. In
the 13C NMR spectrum of 12 the quintet at δ ϭ 127.9
Synthesis of Ruthenium Alkynyl Complexes
The reactions of alkynes 3 and 5 with one equivalent of (2JPC ϭ 16 Hz) was assigned to the alkynyl carbon which is
cis-[RuCl2(dppe)2] (8) and two equivalents of KPF6 in α to Ru, thus demonstrating a trans-configuration of the
CH2Cl2 at room temperature for four days led to the con- chloro- and ethynyl ligands.
2306
Eur. J. Inorg. Chem. 2001, 2305Ϫ2310

Ruthenium-Capping of Di- and Tetraethynylbiphenyls
FULL PAPER
using Pd-catalyzed cross-coupling reactions as well as their
derivatization with ruthenium complexes to afford stable al-
kynyl and alkenyl complexes. The reaction of the terminal
ϪCϵCH groups of 3 and 5 with cis-[RuCl2(dppe)2] (8), fol-
lowed by deprotonation of these mixtures with Et3N, leads
to the terminal σ-alkynylruthenium derivatives. Reaction of
3 and 5 with the ruthenium hydride [Ru(CO)ClH(PPh3)2]
(13) gave the corresponding di-σ-alkenyl complexes. The di-
ruthenium complexes 12 and 15 bear two free terminal al-
kyne groups, which could be further metallated to form het-
erometallic complexes. Further work in this area is in pro-
gress.
Experimental Section
General: Infrared spectra were recorded at the ICMM on a Nicolet
20 SXC FT-IR spectrophotometer, using KBr disks. The NMR de-
terminations were carried out on a Bruker AC-200 (or a Bruker
AMX-300) apparatus at 23 °C. Mass spectra were performed at
the SIdI (UAM), using the fast cesium-ion bombardment (liquid
secondary ion mass spectrometry, LSIMS) or EI-MS techniques.
Only the most significant IR frequencies and MS fragmentations
are given. Elemental analyses were performed at the ICMM or SIdI
(UAM). Differential thermal analysis (DTA) curves were obtained
at the ICMM, using a Stanton STA 781 analyzer. All reactions
were performed under a nitrogen atmosphere, using Schlenk tech-
niques and the solvents were deoxygenated and dried by standard
methods.
Cyclic voltammetric measurements were carried out at the Univer-
´
sidad Complutense de Madrid (Departamento de Quımica Inor-
´
´
ganica I, Facultad de Ciencias Quımicas) on an Autolab apparatus
equipped with a PSTA 10 potentiostat, using a three-electrode cell
with platinum wire as working and auxiliary electrodes and Ag/
AgCl electrode as a reference with a solution of the complex (10Ϫ3
mol/dm3) in dichloromethane containing [Nbu4][BF4] (0.2 mol/
dm3) as the base electrolyte, at a scan rate of 200 mV sϪ1. Values
are referred to an Ag/AgCl electrode and ferrocene was used as
internal standard.
Scheme 4
A cyclic voltammetric study of complex 12 showed a
single quasi-reversible redox wave for both ruthenium sys-
tems [E1/2 versus Cp2Feϩ/Cp2Fe: ϩ 0.72 V (∆Ep ϭ 63 mV)].
This unique oxidation wave shows that the dialkynyl com-
plex 12 is capable of providing two electrons at the same
potential and that the bridge between the ethynylated
phenyl rings of the biphenyl system does not allow signific-
ant communication between the ruthenium centers.
The complexes [PdCl2(PPh3)2], [Pd(PPh3)4],[32] cis-[RuCl2(dppe)2]
(8),[33] and [RuHCl(CO)(PPh3)3] (13)[34] were prepared by known
procedures.
3,5,3Ј,5Ј-Tetrabromobiphenyl-2,2Ј-diyl Dipivalate (1): A solution of
3,3Ј,5,5Ј-tetrabromo-2,2Ј-dihydroxybiphenyl (2.00 g, 4.0 mmol) in
pyridine (50 mL) and pivalic anhydride (4.0 mL, 19.7 mmol) was
heated under refluxing conditions for 2 h. After being cooled to
room temperature, the mixture was diluted with water and ex-
tracted with EtOAc. The organic layer was washed with aqueous
HCl (10%), dried (Na2SO4) and the solvent was evaporated to yield
Synthesis of Ruthenium Alkenyl Complexes
The reaction of alkynes 3 and 5 with two equivalents of
[Ru(CO)HCl(PPh3)3] (13) in CH2Cl2 at room temperature
gave rise to the red dialkenyl complexes 14 (92%) and 15
(91%). As expected,[31] the hydroruthenation proceeds in a
3
cis fashion, as demonstrated by a trans J(1H-1H) coupling
1
1 (2.60 g, 97%) as a beige solid: m.p. 115 °C. Ϫ H NMR (CDCl3,
of 13.7Ϫ14 Hz. Although the pentacoordinated Ru centers
300 MHz): δ ϭ 1.13 (s, 18 H), 7.34 (s, 2 H), 7.78 (s, 1 H), 7.79 (s,
of these complexes are less sterically hindered than those of 1 H). Ϫ 13C NMR (CDCl3, 75.5 MHz): δ ϭ 26.7, 39.1, 118.2,
119.00, 132.5, 132.6, 135.8, 145.5, 174.9. Ϫ EI-MS: m/z (%) ϭ 666
(0.5) [Mϩ], 582 (5), 498 (8), 417 (4), 339 (1), 311 (3), 85 (43), 57
(100). Ϫ C22H22Br4O4 (670.03): calcd. C 39.44, H 3.31; found C
39.40, H 3.15.
9Ϫ12, a tetrametallated derivative could not be obtained by
reaction of alkyne 5 with four equivalents of hydride 13.
Conclusions
3,3Ј-Dibromo-5,5Ј-bis(trimethylsilylethynyl)biphenyl-2,2Ј-diyl Dipiv-
alate (2): A mixture of 1 (500 mg, 0.74 mmol), trimethylsilylace-
tylene (0.42 mL, 3 mmol), [PdCl2(PPh3)2] (103 mg, 0.148 mmol),
We have described the synthesis of the di- and tetraalky-
nyl biphenyls 3 and 5 from the tetrabromo derivative 1 by and CuI (56 mg, 0.30 mmol) in Et3N (25 mL) was stirred at 23 °C
Eur. J. Inorg. Chem. 2001, 2305Ϫ2310 2307

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B. Gomez-Lor, A. Santos, M. Ruiz, A. M. Echavarren
FULL PAPER
for 12 h. The mixture was diluted with CH2Cl2, washed with H2O, 1H NMR (200 MHz, CDCl3): δ ϭ 3.01 (s, 2 H), 3.49 (2 H), 7.43
dried and the solvents evaporated. The residue was chromato-
(d, J ϭ 2.0 Hz, 2 H), 7.59 (d, J ϭ 2.0 Hz, 2 H). Ϫ 13C NMR
(75 MHz, CDCl3): δ ϭ 76.7, 77.4, 82.1, 84.8, 109.9, 114.7, 123.5,
graphed (hexane/EtOAc, 4:1) to give 2 as a colorless oil (466 mg,
1
89%). Ϫ H NMR (CDCl3, 300 MHz): δ ϭ 0.23 (s, 9 H), 0.25 (s, 136.0, 136.2, 154.7. Ϫ EI-MS: m/z (%) ϭ 282 (100) [Mϩ], 253 (23),
9 H), 1.12 (s, 18 H), 7.30 (s, 1 H), 7.31 (s, 1 H), 7.70 (s, 1 H), 7.71 224 (32).
(s, 1 H). Ϫ 13C NMR (CDCl3, 75.5 MHz): δ ϭ Ϫ0.2, 26.7, 39.1,
3,3Ј,5,5Ј-Tetra(phenylethynyl)biphenyl-2,2Ј-diyl Dipivalate (7):
A
96. 6, 102.0, 116.9, 122.4, 133.4, 131.61, 136.2, 146.2, 175.2. Ϫ EI-
MS: m/z (%) ϭ 702 (2) [Mϩ], 618 (14), 534 (13), 519 (5), 439 (8),
179 (7), 85 (11), 73 (12) 57 (100). Ϫ C32H40Br2O4Si2 (704.64): calcd.
C 54.54, H 5.72; found C 54.88, H 6.11.
mixture of 5 (41 mg, 0.1 mmol), [Pd(PPh3)4] (23 mg, 0.02 mmol),
iodobenzene (60 µL, 0.53 mmol), and CuI (4 mg, 0.02 mmol) in
pyrrolidine (5 mL) was stirred at 23 °C for 3 h. The mixture was
diluted with CH2Cl2, washed with H2O, dried and the solvents
evaporated. The residue was chromatographed (hexane/EtOAc, 9:1)
3,3Ј-Dibromo-5,5Ј-diethynylbiphenyl-2,2Ј-diyl Dipivalate (3): A mix-
ture of 2 (466 mg, 0.66 mmol) and K2CO3 (182 mg, 1.3 mmol) in a
mixture of CH2Cl2 (2 mL), MeOH (10 mL), and H2O (0.5 mL) was
stirred at 23 °C for 30 min. The mixture was diluted with CH2Cl2,
washed with H2O, aqueous HCl (10%), dried (Na2SO4) and the
solvents evaporated to yield 3 as a colorless oil (332 mg, 90%).
Recrystallization (Et2O/hexane, 1:1) gave 3 as a white solid, m.p.
121Ϫ123 °C. Ϫ IR (KBr): ν˜ ϭ 3262 s ν(ϵCH), 2104 w ν(CϵC),
1
to give 7 as a colorless oil (62 mg, 83%). Ϫ H NMR (200 MHz,
CDCl3): δ ϭ 1.17 (s, 18 H), 7.78 (d, J ϭ 2.1 Hz, 2 H), 7.39Ϫ7.27
(m, 12 H), 7.55Ϫ7.45 (m, 10 H). Ϫ 13C NMR (75 MHz, CDCl3):
δ ϭ 26.9, 39.1, 83.7, 87.5, 90.4, 94.2, 118.8, 121.3, 122.7, 122.8,
128.4, 128.5, 128.7, 130.8, 131.6, 131.7, 133.8, 135.9, 148.9, 175.6.
Ϫ EI-MS: m/z (%) ϭ 754 (8) [Mϩ], 670 (25), 586 (62), 57 (100). Ϫ
HRMS calcd. for C54H42O4: 754.3083; found 754.3054.
1
1748 vs ν(CϭO). Ϫ H NMR (CDCl3, 300 MHz): δ ϭ 1.11 (s, 18
H), 3.12 (s, 2 H), 7.33 (s, 1 H), 7.73 (s, 1 H), 7.74 (s, 1 H), 7.75 (s,
1 H). Ϫ 13C NMR (CDCl3, 75.5 MHz): δ ϭ 26.7, 39.0, 79.2, 80.8,
117.1, 121.3, 131.6, 133.5, 136.5, 146.6, 174.7. Ϫ EI-MS: m/z (%) ϭ
558 (0.1) [Mϩ], 474 (80), 389 (0.1), 309 (0.2), 231 (2), 85 (21), 57
(100). Ϫ C26H24Br2O4 (560.28): calcd. C 55.74, H 4.32; found C
56.58, H 4.77.
Synthesis of the Monosubstituted Alkynyl Complex 9: A solution of
alkyne 3 (29 mg, 0.052 mmol), cis-[RuCl2(dppe)2] (8) (50 mg,
0.052 mmol), and KPF6 (18.96 mg, 0.103 mmol) in CH2Cl2 (5 mL)
was stirred for 4 days at room temperature. The intermediate vi-
nylidene complex could be isolated by trituration with hexane as a
˜
brown-beige powder (75 mg, 88%). Ϫ IR (KBr): ν ϭ 3274 w
ν(ϵCH), 1750 ms ν(CϭO), 2110 vw ν(CϵCH), 1620 ms ν(ϭCϭ
C), 836 vs ν(PF6). Ϫ H NMR (CDCl3, 300 MHz): δ ϭ 1.07, (s, 9
3,3Ј,5,5Ј-Tetrakis(trimethylsilylethynyl)biphenyl-2,2Ј-diyl Dipivalate
(4): A mixture of 1 (134 mg, 0.2 mmol), [Pd(PPh3)4] (46 mg,
0.04 mmol) and (trimethylsilyl)ethynyltributylstannane (470 mg,
1.2 mmol) in toluene (10 mL) was heated under refluxing condi-
tions for 4 h. After being cooled to room temperature, the mixture
was diluted with CH2Cl2, washed with water and a saturated solu-
tion of KF, dried (Na2SO4) and the solvents evaporated. The res-
idue was chromatographed (hexane/EtOAc, 9:1) to give 4 as a col-
orless oil (133 mg, 90%). Ϫ 1H NMR (CDCl3, 300 MHz): δ ϭ 0.21
(s, 18 H), 0.23 (s, 18 H), 1.13 (s, 18 H), 7.30 (s, 1 H), 7.31 (s, 1 H),
7.61 (s, 1 H), 7.62 (s, 1 H). Ϫ 13C NMR (CDCl3, 75.5 MHz): δ ϭ
Ϫ0.2, 26.8, 38.9, 95.4, 98.7, 99.8, 102.8, 118.5, 120.9, 130.3, 134.3,
136.7, 149.2, 175.2. Ϫ EI-MS: m/z (%) ϭ 738 (36) [Mϩ], 654 (100),
570 (28), 481 (4), 467 (13), 57 (25). Ϫ C42H58O4Si4·0.5H2O
(748.26): calcd. C 67.42, H 7.95; found C 67.41; 8.18.
1
H), 1.17 (s, 9 H), 2.60Ϫ3.05 (m, 8 H), 3.11 (s, 1 H), 3.12 (br. s, 1
H), 6.85Ϫ7.55 (m, 43 H), 7.68 (br. s, 1 H) (minor signals of an
η2-alkyne complex were also observed); Ϫ C78H72Br2ClF6O4P5Ru
(1638.61): calcd. C 57.17, H 4.43; found C 57.11, H 4.48. An excess
of Et3N (0.05 mL, 0.35 mmol) was added to the brownish-yellow
solution containing the vinylidene complex and the resulting solu-
tion was stirred for 1 h at 23 °C. After addition of CH2Cl2 (15 mL),
this yellow solution was washed with water (3 ϫ). After the usual
extractive workup, the solvent was partially evaporated. Addition
of hexane led to a yellow precipitate, which was filtered off to give
9 (55 mg, 72%). Ϫ IR (KBr): ν˜ ϭ 3298 w ν(ϵCH), 2110 vw
ν(CϵCH), 2054
s ν(CϵC), ν(CϭO). Ϫ
1H NMR (CDCl3,
300 MHz): δ ϭ 1.14 (s, 9 H), 1.16 (s, 9 H), 2.66 (br. s, 8 H), 3.17
(s, 1 H), 6.22 (br. s, 1 H), 6.64 (br. s, 1 H), 6.84Ϫ7.49 (m, 33 H),
7.51 (br. s, 8 H), 7.75 (s, 1 H). Ϫ 31P{1H} NMR (121.5 MHz,
CDCl3): δ ϭ 49.55 (s). Ϫ C78H71Br2ClO4P4Ru·0.5H2O (1501.63):
calcd. C 62.39, H 4.83; found C 62.44, H 4.89.
3,3Ј,5,5Ј-Tetraethynylbiphenyl-2,2Ј-diyl Dipivalate (5): A mixture of
4 (139 mg, 0.118 mmol) and K2CO3 (33 mg, 0.24 mmol) in a mix-
ture of CH2Cl2 (1 mL), MeOH (5 mL), and H2O (0.3 mL) was
stirred at 23 °C for 30 min. The mixture was diluted with CH2Cl2,
washed with H2O and aqueous HCl (10%), dried (Na2SO4) and the
solvents evaporated to give 5 (77 mg, 95%) as a white solid: m.p.
Formation of trans-[Ru(CO)Cl(dppe)2]PF6 from Biphenyl 3 and
Ruthenium Complex 8: A solution of alkyne 3 (26 mg, 0.05 mmol),
cis-[RuCl2(dppe)2] (8) (89 mg, 0.10 mmol), and KPF6 (34 mg,
0.20 mmol) in CH2Cl2 (5 mL) was stirred for 7 days at 23 °C until
no free alkyne was detectable by TLC. The mixture was filtered
and the filtrate was partially evaporated. Addition of hexane led to
precipitation of a solid, which was filtered off and washed with
hexane to give a beige powder (140 mg, quantitative yield). This
solid was suspended in CH2Cl2 (2 mL) and hexane (10 mL), and
was then stirred in air at 23 °C for 3 h. The solvents were evapor-
ated and the greenish-brown solid was triturated with Et2O and
filtered off to give a greenish-beige powder. To eliminate residual
˜
125 °C. Ϫ IR (KBr): ν ϭ 3306 ms, 3279 sh ν(ϵCH), 2165 w, 2135
w ν(CϵC), 1750 vs ν(CϭO). Ϫ 1H NMR (CDCl3, 300 MHz): δ ϭ
1.11 (s, 18 H), 3.08 (s, 2 H), 3.21 (s, 2 H), 7.37 (d, J ϭ 2.0 Hz, 2
H), 7.66 (d, J ϭ 2.0 Hz, 2 H). Ϫ 13C NMR (CDCl3, 75.5 MHz):
δ ϭ 26.7, 38.9, 77.6, 78.5, 81.4, 82.6, 117.7, 120.1, 130.4, 134.8,
136.9, 150.1, 175.3. Ϫ FAB-MS: m/z (%) ϭ 450 (15) [Mϩ], 366 (47),
282 (87), 253 (11), 224 (15), 85 (9), 57 (100). Ϫ C30H26O4·0.5H2O
(459.53): calcd. C 78.41, H 5.92; found C 78.87, H 5.97.
2,2Ј-Dihydroxy-3,3Ј,5,5Ј-tetra(ethynyl)biphenyl (6): A mixture of 5
(10 mg, 0.022 mmol) and NaOH (6 mg, 0.15 mmol) in a mixture of vinylidene, the crude product was dissolved in CH2Cl2 (5 mL) and
MeOH (2 mL), and H2O (0.1 mL) was stirred at 23 °C for 18 hours. treated with Et3N (0.1 mL) at 23 °C. The solution was washed with
The mixture was diluted with CH2Cl2, washed with H2O and aque-
water (3 ϫ) and, after the usual extractive workup, the residue was
ous HCl (10%), dried (Na2SO4) and the solvents evaporated to give filtered through basic alumina. Partial evaporation of the solvent
6 (5 mg, 80%) as a white solid: (decomposes without melting; the and addition of hexane gave trans-[Ru(CO)Cl(dppe)2]PF6 as gray-
DTA curve shows two exothermic peaks at 115 °C and 196 °C). Ϫ
white crystals (98 mg, 59%) and the dialkynyl complex 9 (20 mg,
2308
Eur. J. Inorg. Chem. 2001, 2305Ϫ2310

Ruthenium-Capping of Di- and Tetraethynylbiphenyls
FULL PAPER
11%) as yellow crystals, which were separated by fractional crystal-
lization.
H), 7.10Ϫ7.22 (m, 16 H), 7.36 (br. s, 32 H). Ϫ 13C NMR (CDCl3,
75.5 MHz): δ ϭ 26.8, 30.6, 38.8, 79.4 (s, CϵCH), 80.0 (s, CϵCH,
111.2, 115.5 (s, RuϪCϵC), 126.9 (br. s), 127.3 (br. s), 127.9 (quint.,
˜
trans-[Ru(CO)Cl(dppe)2]PF6: IR (KBr): ν ϭ 1946 vs ν(CϭO), 837
vs ν(PF6). Ϫ 1H NMR (CDCl3, 300 MHz): δ ϭ 2.66 (m, 4 H), 2.92 2JPC ϭ 16 Hz, CϵCϪRu), 128.4, 128.9 (br. s), 130.5, 131.8, 133.9,
(m, 4 H), 6.95Ϫ7.50 (m). Ϫ C53H48ClF6OP5Ru (1106.3): calcd. C 134.5 (br. s), 135.2, 135.8 (q, J ϭ 22.7 Hz, dppe), 145.2, 175.5. Ϫ
57.54, H 4.37; found C 57.51, H 4.40.
31P{1H} NMR (121.5 MHz, CDCl3): δ ϭ 49.89 (s). Ϫ FAB-MS:
m/z (%) ϭ 2315.1 (6) [Mϩ], 1917 (4), 1381 (2), 957 (9), 933 (19), 897
(100), 685 (16.). Ϫ C134H120Cl2O4P8Ru2·1.5H2O (2342.25): calcd. C
68.71, H 5.28; found C 68.69, H 5.30. The intermediate divinylid-
ene could be isolated as above as a beige powder: IR (KBr): ν˜ ϭ
3285 m ν(ϵCH), 2110 vw ν(CϵCH), 1757 ms ν(CϭO), 1628 s ν(ϭ
CϭC), 843 vs ν(PF6). Ϫ C134H122Cl2F12O4P10Ru (2607.2): 61.73,
H 4.72; found C 62.61, H 5.15.
Synthesis of the Monosubstituted Alkynyl Complex 10: Alkyne 5
(23 mg, 0.052 mmol) was treated as above to give 10 as a yellow
˜
powder (52 mg, 74%). Ϫ IR (KBr): ν ϭ 3282 ms ν(ϵCH), 2110 vw
1
ν(CϵCH), 2049 s ν(CϵC), 1748 s ν(CϭO). Ϫ H NMR (CDCl3,
300 MHz): δ ϭ 1.13 (s, 9 H), 1.15 (s, 9 H), 2.67 (br. s, 8 H), 3.13
(s, 2 H), 3.21 (s, H), 6.22 (br. s, 1 H), 6.60 (br. s, 1 H), 6.89Ϫ7.10
(2m, 16 H), 7.10Ϫ7.32 (2m, 16 H), 7.37 (br. s, 1 H), 7.46 (br. s, 8
H), 7.67 (s, 1 H). Ϫ 31P{1H} NMR (121.5 MHz, CDCl3): δ ϭ
49.45(s). Ϫ C82H73ClO4P4Ru·H2O (1400.89): C 70.30, H 5.40;
found C 70.40, H 5.34. The intermediate vinylidene complex could
Synthesis of the Disubstituted Alkenyl Complex 14: A solution of
[RuHCl(CO)(PPh3)3] (13; 80 mg, 0.084 mmol) and alkyne
3
(23.5 mg, 0.042 mmol) was stirred at 23 °C in CH2Cl2 (10 mL) for
30 min. The orange-red solution was concentrated and hexane was
added. after cooling to 0 °C, the mixture was filtered and the fil-
trate was evaporated. The residue was taken up in CH2Cl2/Et2O
and filtered. Hexane was added to the filtrate to give a precipitate,
which was filtered off to give 14 (78 mg, 92%) as an orange solid.
˜
be isolated as above to give a brown-beige powder: IR (KBr): ν ϭ
3273 ms ν(ϵCH), 2110 w ν(CϵCH), 1751 ms ν(CϭO), 1628 ms
ν(ϭCϭC), 843 vs ν(PF6). Ϫ C82H74ClF6O4P5Ru (1528.9): calcd. C
64.42, H 5.18; found C 64.75, H 5.52.
Synthesis of the Disubstituted Alkynyl Complex 11: A solution of
alkyne 3 (29 mg, 0.052 mmol), cis-[RuCl2(dppe)2] (8) (100 mg,
0.10 mmol), and KPF6 (38 mg, 0.21 mmol) in CH2Cl2 (5 mL) was
stirred for 7 days at 23 °C. The mixture was filtered and the filtrate
was partially evaporated. Addition of hexane led to precipitation
of a solid, which was filtered off and washed with hexane to give
1
Ϫ IR (KBr): ν˜ ϭ 1924 vs ν(CϵO), 1736 s ν(CϭO). Ϫ H NMR
3
(CDCl3, 300 MHz): δ ϭ 0.93 (s, 18 H), 5.49 (d, JHPϭ 13.7 Hz, 2
H), 6.35 (s, 2 H), 6.89 (s, 2 H), 7.20Ϫ7.42 (m, 36 H, Ph), 7.45Ϫ7.70
3
(m, 24 H, Ph), 8.38 (d, JHP
ϭ
13.7 Hz,
2
H).
Ϫ
C100H86Br2Cl2O6P4Ru2·CH2Cl2 (2025.43): calcd. C 59.89, H 4.38;
found C 59.83, H 4.27.
˜
the divinylidene complex. Ϫ IR (KBr): ν ϭ 1750 ms ν (CϭO),
Synthesis of the Disubstituted Alkenyl Complex 15: Similarly, a solu-
tion of [RuHCl(CO)(PPh3)3] (13; 50 mg, 0.0525 mmol) and the al-
kyne 5 (11.83 mg, 0.0263 mmol) was stirred at 23 °C in CH2Cl2
(5 mL) for 1.5 h. After partial evaporation of solvent, addition of
Et2O led to a precipitate, which was filtered off to give 15 (44 mg,
1626 s ν (ϭCϭC), 836 vs ν (PF6). Ϫ C130H120Br2Cl2F12O4P10Ru2
(2716.9): calcd. C 57.47, H 4.45; found C 57.41, H 4.46. An excess
of Et3N (0.71 mmol, 0.1 mL) was added to the solution containing
the vinylidene complex, and the resulting solution was stirred for
1 h at 23 °C. The yellow solution, after addition of CH2Cl2
(15 mL), was washed with water (3 ϫ). After the usual workup the
solvent was partially evaporated. Addition of hexane led to the
formation of a yellow microcrystalline powder, which was filtered
˜
91%). Ϫ IR (KBr): ν ϭ 3288 w ν(ϵCH), 2110 vw ν(CϵCH), 1922
vs ν(CϵO), 1740 ν(CϭO). Ϫ 1H NMR (CDCl3, 300 MHz): δ ϭ
0.93 (s, 18 H), 3.11 (s, 2 H), 5.53 (d, 3JHP ϭ 14.0 Hz, 2 H), 6.41 (d,
J ϭ 2.0 Hz, 2 H), 6.84 (d, J ϭ 2.0 Hz, 2 H), 7.42Ϫ7.20 (m, 36
˜
off to give 11 (89 mg, 72%). Ϫ IR (KBr): ν ϭ 2050 s ν(CϵC), 1750
3
s ν(CϭO). Ϫ 1H NMR (CDCl3, 300 MHz): δ ϭ 1.19 (s, 18 H),
2.66 (br. s, 16 H), 6.48 (br. s, 2 H), 6.54 (br. s, 2 H), 6.92 (m, 16
H), 7.02 (m, 20 H), 7.18 (m, 12 H), 7.29 (m, 16 H), 7.40 (m, 16 H).
H), 7.70Ϫ7.45 (m, 24 H, Ph), 8.33 (dm, JHP ϭ 14.0 Hz, 2 H);
Ϫ C104H88Cl2O6P4Ru2·0.75H2O (1844.26): calcd. C 67.73, H 4.89;
found C 67.80, H 4.80.
Ϫ
13C NMR (CDCl3, 50.32 MHz): δ ϭ 26.9, 30.6 (m), 39.0, 110.7,
2
115.4 (br. s, RuϪCϵC), 127.0, 127.3 (br. s), 128.1 (quint, JPC
ϭ
Acknowledgments
16 Hz, CϵCϪRu), 128.9 (br. s), 131.7, 132.6, 133.9, 134.5 (br. s),
134.7, 135.8 (m), 141.5, 175.3. Ϫ 31P{1H} NMR (121.5 MHz,
CDCl3): δ ϭ 49.90 (s). Ϫ FAB-MS: m/z (%) ϭ 2421 (8) [Mϩ], 2386
(3), 2026 (59), 897 (59), 685 (6), 499 (42), 316 (56), 185 (95), 57
(100). Ϫ C130H122Br2Cl2O6P8Ru2·2H2O (2461.00): calcd. C 63.45,
H 5.00; found C 63.26, H 5.17.
We are grateful to the DGES (Projects PB97-0002-C2-01 and 02)
for support of this research. We also thank the MEC for a predoc-
toral fellowship to M. R. and to the CAM for a postdoctoral fel-
lowship to B. G.-L. We acknowledge Johnson Matthey PLC for a
generous loan of PdCl2 and RuCl3.
Synthesis of the Disubstituted Alkynyl Complex 12: An excess of
Et3N (0.1 mL, 0.71 mmol) was added to the brownish-yellow solu-
tion containing the divinylidene complex prepared from 5 (23 mg,
0.052 mmol), and the resulting solution was stirred for 1 h at 23
°C. The yellow solution, after addition of CH2Cl2 (15 mL), was
washed with water (3 ϫ). After the usual extractive workup, the
solvent was partially evaporated. Addition of hexane led to a yellow
microcrystalline powder of the dialkynyl complex 12 (101 mg, 85%)
as a yellow powder. This compound contained traces of the
monoalkynyl complex 10. A pure product was obtained by crystal-
lization from CH2Cl2/hexane to yield yellow crystals, which decom-
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