Multiple Re-C bonds at the [{MeC(CH2PPh2)3}Re(CO)2]+ auxiliary

Article abstract of DOI:10.1021/om9602264

After displacement of the η²-H₂ ligand from [(triphos)Re(CO)₂(η²-H₂)]BF₄ (2), ethyne and various 1-alkynes, HC≡CR, are tautomerized at the Re(I) center to vinylidene ligands (R = H, Ph, p-t

Full text of DOI:10.1021/om9602264

3804
Organometallics 1996, 15, 3804-3816
Mu ltip le Re-C Bon d s a t th e [{MeC(CH2P P h 2)3}Re(CO)2]+
Au xilia r y
Claudio Bianchini,*,† Andrea Marchi,‡ Lorenza Marvelli,‡ Maurizio Peruzzini,*,†
Antonio Romerosa,† and Roberto Rossi*,‡
Istituto per lo Studio della Stereochimica ed Energetica dei Composti di Coordinazione, CNR,
Via J . Nardi 39, 50132 Firenze, Italy, and Laboratorio di Chimica Nucleare ed Inorganica,
Dipartimento di Chimica, Universita` di Ferrara, Via Borsari 46, 44100 Ferrara, Italy
Received March 25, 1996X
After displacement of the η2-H2 ligand from [(triphos)Re(CO)2(η2-H2)]BF4 (2), ethyne and
various 1-alkynes, HC≡CR, are tautomerized at the Re(I) center to vinylidene ligands (R )
H, Ph, p-tolyl, COOEt, n-C6H13, SiMe3). A kinetic π-alkyne adduct is intercepted at low
temperature during the reaction between 2 and ethyne. The primary vinylidene complex
[(triphos)Re(CO)2(CdCH2)]BF4 (7-BF4) can also be obtained by reaction of the (trimethylsilyl)-
vinylidene complex [(triphos)Re(CO)2{CdC(H)SiMe3}]BF4 with stoichiometric water. Un-
precedented examples of addition of either water or alcohols to Re-vinylidene moieties to
give hydroxycarbene or alkoxycarbene complexes are presented. In particular, an excess of
water transforms 7-BF4 into the secondary hydroxycarbene complex [(triphos)Re(CO)2{C(OH)-
CH3}]BF4 (11), which can be isolated in the solid state. Upon thermolysis in refluxing
tetrahydrofuran, 11 selectively converts to the tricarbonyl complex [(triphos)Re(CO)3]BF4
and methane. Deprotonation of 11 by mild bases gives the acetyl derivative (triphos)Re-
(CO)2(COCH3), which regenerates the hydroxycarbene precursor by protonation with strong
acids. The ethoxycarbene complexes [(triphos)Re(CO)2{C(OEt)CH2R}]BPh4 (R ) H, COOEt)
are prepared by nucleophilic addition of ethanol across the CdC double bond of the
corresponding vinylidene derivatives. Neutral σ-alkynyl complexes of the general formula
(triphos)Re(CO)2(C≡CR) (R ) Ph, p-tolyl, COOEt, n-C6H13, H) are obtained by reaction of
the vinylidene derivatives with strong bases. The reaction of the σ-alkynyl complexes with
various methylating agents affords disubstituted vinylidene derivatives, herein exemplified
by [(triphos)Re(CO)2{CdC(Me)Ph}](OSO2CF3). The structural identities in the solid state
of the phenylvinylidene complex [(triphos)Re(CO)2{CdC(H)Ph}]BF4 and of the ethoxycarbene
complex [(triphos)Re(CO)2{C(OEt)CH3}]BPh4 have been determined by X-ray diffraction
analyses. In both complexes the metal center is octahedrally coordinated by a fac triphos
ligand, by two mutually cis terminal carbonyls, and by the organyl ligand.
In tr od u ction
fleeting existence in related reactions with other transi-
tion metals.2
The chemistry of rhenium-carbon multiple bonds has
experienced much progress in recent years.1 Several
vinylidene, carbene, and carbyne complexes have been
synthesized and many exotic reactions have been dis-
closed which are made possible by the ability of rhenium
to stabilize intermediates that generally have only a
A glance through the literature shows that most of
the Re-C multiple bond chemistry is based on cyclo-
pentadienyl ligands.1,2 In earlier work, we have dem-
onstrated that the tripodal triphosphine MeC(CH2-
PPh2)3 (triphos) is as efficient as the isolelectronic and
isolobal cyclopentadienyl ligands in forming rhenium
complexes in various metal oxidation states and coor-
dination numbers.3,4 Unlike cyclopentadienyl ligands,
triphos provides its metal complexes with a much higher
thermal stability and thus is more amenable to catalytic
studies than cyclopentadienyl groups.5
† ISSECC, CNR.
‡ Universita` di Ferrara.
X Abstract published in Advance ACS Abstracts, J uly 15, 1996.
(1) (a) Casey, C. P. Science 1993, 259, 1552. (b) Roma˜o, C. C. In
Encyclopedia of Inorganic Chemistry; King, R. B., Ed.; J . Wiley:
Chichester, England, 1994; Vol. 6, p 3437. (c) O’Connor, J . M. In
Comprehensive Organometallic Chemistry II; Abel, E. W., Stone, F.
G. A., Wilkinson, G., Eds.; Pergamon Press: Oxford, England, 1985;
Vol. 6, pp 168-228.
Herein are reported the reactions of the [(triphos)Re-
(CO)2]+ fragment with ethyne and selected 1-alkynes
to give primary Re(I) vinylidene complexes whose
remarkable stability has allowed us to investigate their
(2) (a) Casey, C. P.; Carin˜o, R. S.; Hayashi, R. K.; Schladetzky, K.
D. J . Am. Chem. Soc. 1996, 118, 1617. (b) Wang, Y.; Gladysz, J . A.
Chem. Ber. 1995, 128, 213. (c) Weng, W.; Bartik, T.; Brady, M.; Bartik,
B.; Ramsden, J . A.; Arif, A. M.; Gladysz, J . A. J . Am. Chem. Soc. 1995,
117, 11922. (d) Leeaphon, M.; Ondracek, A. L.; Thomas, R. J .; Fanwick,
P. E.; Walton, R. A. J . Am. Chem. Soc. 1995, 117, 9715. (e) LaPointe,
A. M.; Schrock, R. R. Organometallics 1995, 14, 1875. (f) Casey, C. P.;
Czerwinski, C. J .; Hayashi, R. K. J . Am. Chem. Soc. 1995, 117, 4189.
(g) Kort, D. A.; Shih, K.-Y.; Wu, W.; Fanwick, D. E.; Walton, R. A.
Organometallics 1995, 14, 448. (h) Padolik, L. L.; Gallucci, J . C.;
Wojcicki, A. J . Am. Chem. Soc. 1993, 115, 9986. (i) Lang, H. Angew.
Chem., Int. Ed. Engl. 1994, 33, 547. (j) Flatt, B. T.; Grubbs, R. H.;
Blanski, R. L.; Calabrese, J . C.; Feldman, J . Organometallics 1994,
13, 2728.
(3) Bianchini, C.; Peruzzini, M.; Zanobini, F.; Magon, L.; Marvelli,
L.; Rossi, R. J . Organomet. Chem. 1993, 451, 97.
(4) Bianchini, C.; Marchi, A.; Marvelli, L.; Peruzzini, M.; Romerosa,
A.; Rossi, R.; Vacca, A. Organometallics 1995, 14, 3203.
(5) See for example: (a) Bianchini, C.; Herrera, V.; J imenez, M. V.;
Meli, A.; Sa´nchez-Delgado, R.; Vizza, F. J . Am. Chem. Soc. 1995, 117,
8567. (b) Bianchini, C.; Caulton, K. G.; J ohnson, T. J .; Meli, A.;
Peruzzini, M.; Vizza, F. Organometallics 1995, 14, 933. (c) Bianchini,
C.; Meli, A.; Peruzzini, M.; Vizza, F.; Zanobini, F. Coord. Chem. Rev.
1992, 120, 193 and references therein.
S0276-7333(96)00226-9 CCC: $12.00 © 1996 American Chemical Society

Multiple Re-C Bonds
Organometallics, Vol. 15, No. 18, 1996 3805
tivities were measured with an Orion Model 990101 conduc-
tance cell connected to a Model 101 conductivity meter. The
conductivity data were obtained at sample concentrations of
ca. 1 × 10-3 M in nitroethane solutions at room temperature
(21 °C). Elemental analyses were performed with a Carlo Erba
Model 1106 elemental analyzer.
reactivity toward nucleophiles such Bronsted bases,
alcohols, and water. As a result, a variety of new Re-
organyl complexes have been synthesized, which in-
cludes σ-alkynyl, η1-acyl, primary, secondary, and ter-
tiary vinylidene, secondary hydroxycarbene, and alkoxy-
carbene derivatives.
Syn th esis of th e Vin ylid en e Com p lexes [(tr ip h os)Re-
(CO)2{CdC(H)R}]Y [R ) P h (3), p-tolyl (4), COOEt (5),
n -C6H13 (6), Y ) BF 4, BP h 4]. Gen er a l P r oced u r e.
A
Exp er im en ta l Section
dichloromethane (10 mL) solution of the complex [(triphos)-
Re(CO)2(η2-H2)]BF4 (2) was prepared in a 25 mL Schlenk flask
by reaction of [(triphos)Re(CO)2H] (1) (0.25 g, 0.26 mmol) with
HBF4‚OMe2 (33 µL, 0.27 mmol) at -10 °C.4 To this solution a
slight excess (ca. 10%) of the terminal alkyne was added with
stirring. Immediately the color of the resulting solution
changed from pale yellow to either deep violet (R ) Ph, p-tolyl)
or pale purple (R ) COOEt, n-C6H13). After the reaction
mixture was allowed to reach room temperature, the solvent
was removed in vacuo, and the solid residue was extracted
twice with 3 mL of THF. After addition of ethanol (2 mL) and
partial evaporation of the solvent under a flow of nitrogen,
the vinylidene complexes [(triphos)Re(CO)2{CdC(H)R}]BF4 [R
) Ph (3-BF4), p-tolyl (4-BF4), COOEt (5-BF4), n-C6H13 (6-BF4)]
were obtained in very good yield (g89%).
Addition of NaBPh4 (0.10 g, 0.22 mmol) in 2 mL of ethanol
and workup as above yielded the corresponding tetraphenylbo-
rate salts in yields higher than 95%.
All the vinylidene complexes are air stable in the solid state,
whereas an inert atmosphere is required for their manipula-
tion in solution (acetone, THF, chlorinated hydrocarbons,
nitroethane).
Gen er a l P r oced u r es. Tetrahydrofuran (THF), toluene,
n-hexane, and diethyl ether were purified by distillation over
sodium/benzophenone under a nitrogen atmosphere. Dichlo-
romethane and ethanol were purified by distillation under
nitrogen over calcium hydride. Terminal alkynes were pur-
chased from Aldrich, their purity was checked by 1H NMR
spectroscopy, and, when necessary, they were distilled under
a N2 atmosphere prior to use. All the other reagents and
chemicals were reagent grade and, unless otherwise stated,
were used as received by commercial suppliers. All reactions
and manipulations were routinely performed under a dry
nitrogen atmosphere by using standard Schlenk-tube tech-
niques. The solid complexes were collected on sintered glass
frits and washed with diethyl ether or n-pentane before being
dried in a stream of nitrogen. The ligand CH3C(CH2PPh2)3
(triphos)6 and the complexes [(triphos)Re(CO)2H] (1)4 and
[(triphos)Re(CO)2(η2-H2)]BF4 (2)4 were prepared as described
in the literature. Deuterated solvents for NMR measurements
(Merck and Aldrich) were dried over molecular sieves (4 Å).
1H and 13C{1H} NMR spectra were recorded on Varian VXR
300, Bruker AC200, or Bruker AVANCE DRX 500 spectrom-
eters operating at 299.94, 200.13, or 500.13 MHz (1H) and
75.42, 50.32, or 125.80 MHz (13C), respectively. Peak positions
are relative to tetramethylsilane and were calibrated against
the residual solvent resonance (1H) or the deuterated solvent
multiplet (13C). 13C-DEPT and gated 13C{1H}-decoupled NMR
experiments were run on the Bruker AC200 spectrometer.
1H,13C-2D HETCOR NMR experiments were recorded on
either the Bruker AC200 spectrometer using the XHCORR
pulse program or the Bruker AVANCE DRX 500 spectrometer
equipped with a 5-mm triple resonance probe head for 1H
detection and inverse detection of the heteronucleus (inverse
correlation mode, HMQC experiment) with no sample spin-
[(tr ip h os)Re(CO)2{CdC(H)P h }]BP h 4 (3-BP h 4): violet,
yield 98%. Anal. Calcd for C75H65BO2P3Re: C, 69.93; H, 5.08.
Found: C, 69.82; H, 4.99. 1H NMR (CD2Cl2, 22 °C, 200.13
MHz): δ 1.75 (q, J HP 3.0 Hz, CH3(triphos), 3H), δ 2.70 (m,
CH2(triphos), 6H). 13C{1H} NMR (CD2Cl2, 22 °C, 75.42 MHz): δ
39.8 (q, J CP 10.9 Hz, CΗ3(triphos)), δ 39.9 (q, J CP 2.7 Hz,
CΗ3C(triphos)), δ 32.7 (m, CH2Paxial), δ 33.2 (br d, J CP 4.0 Hz,
CH2Pequat). ΛΜ(nitroethane) ) 55 Ω-1 cm2 mol-1
.
[(tr ip h os)Re(CO)2{CdC(H)(p-tolyl)}]BP h 4 (4-BP h 4): vio-
let, yield 96%. Anal. Calcd for C76H67BO2P3Re: C, 70.09; H,
5.19. Found: C, 69.87; H, 5.09. 1H NMR (CDCl3, 22 °C, 299.94
MHz): δ 1.82 (br s, CH3(triphos), 3H), δ 2.40 (s, CH3(p-tolyl), 3H),
δ 2.70 (m, CH2(triphos), 6H). 13C{1H} NMR (CDCl3, 22 °C, 75.42
MHz): δ 39.1 (q, J CP 10.6 Hz, CΗ3(triphos) ), δ 39.3 (q, J CP 2.9
Hz, CΗ3C(triphos)), δ 32.1 (br d, J CP 24.5 Hz, CH2Paxial), δ 32.2
(td, N ) J CPequat′ + J CPequat′′ ) 14.9 Hz, J CPaxial 5.2 Hz, CH2Pequat),
1
ning. The H,1H-2D COSY NMR experiments were routinely
conducted on the Bruker AC200 instrument in the absolute
magnitude mode using a 45 or 90° pulse after the incremental
delay or were acquired on the AVANCE DRX 500 Bruker
spectrometer using the phase-sensitive TPPI mode with double
quantum filter. 31P{1H} NMR spectra were recorded on either
the Varian VXR 300 or Bruker AC200 instruments operating
at 121.42 and 81.01 MHz, respectively. Chemical shifts were
measured relative to external 85% H3PO4 with downfield
values taken as positive. The proton NMR spectra with broad-
band phosphorus decoupling were recorded on the Bruker
AC200 instrument equipped with a 5-mm inverse probe and
a BFX-5 amplifier device using the wideband phosphorus
decoupling sequence GARP. Computer simulations of NMR
spectra were carried out with a locally developed package
containing the programs LAOCN37 and DAVINS8 run on a
Compaq Deskpro 386/25 personal computer. The initial
choices of shifts and coupling constants were refined by
iterative least-squares calculations using the experimental
digitized spectrum. The final parameters gave a satisfactory
fit between experimental and calculated spectra, the agree-
ment factor R being less than 1% in all cases. Infrared spectra
were recorded in KBr pellets on a Nicolet 510 P spectrometer
operating in the FT mode or as Nujol mulls on a Perkin-Elmer
1600 series FT-IR spectrometer between KBr plates. Conduc-
δ 21.04 (s, CH3(p-tolyl)). ΛΜ(nitroethane) ) 58 Ω-1 cm2 mol-1
.
[(tr ip h os)Re(CO)2{CdC(H)CO2Et}]BP h 4 (5-BP h 4): pink,
yield 95%. Anal. Calcd for C72H65BO4P3Re: C, 67.35; H, 5.10.
Found: C, 67.25; H, 5.15. 1H NMR (CD2Cl2, 22 °C, 200.13
MHz): δ 1.32 (t, J HH 7.1 Hz, CH3(ester), 3H), δ 1.58 (q, J HP 3.0
Hz, CH3(triphos), 3H), δ 2.62 (m, CH2(triphos), 6H), δ 4.30 (q, J HH
7.1 Hz, CH2(ester), 2H). 13C{1H} NMR (CD2Cl2, 22 °C, 75.42
MHz): δ 163.4 (s, COOEt), δ 61.6 (br s, OCH2(ester)), δ 40.0 (q,
J CP 9.9 Hz, CΗ3(triphos)), δ 39.8 (q, J CP 3.3 Hz, CΗ3C(triphos)), δ
33.5 (br t, J CP 4.0Hz, CH2Paxial), δ 32.6 (td, N ) J CPequat′
J CPequat′′ ) 15.9 Hz, J CPaxial 5.3 Hz, CH2Pequat), δ 15.1 (s,
CH3(ester)). ΛΜ(nitroethane) ) 52 Ω-1 cm2 mol-1
+
.
[(tr ip h os)Re(CO)2{CdC(H)C6H13}]BP h 4 (6-BP h 4): pink,
yield 96%. Anal. Calcd for C75H73BO2P3Re: C, 69.49; H, 5.68.
Found: C, 69.21; H, 5.18. 1H NMR (CD2Cl2, 22 °C, 200.13
MHz): δ 0.89 (t, J HH 6.6 Hz, CH3(hexyl), 3H), δ 1.1-1.3 (m,
CH2(hexyl), 10 H), δ 1.53 (br s, CH3(triphos), 3H), δ 2.38 (m,
CH2(triphos), 6H). 13C{1H} NMR (CD2Cl2, 22 °C, 75.42 MHz): δ
40.2 (q, J CP 10.0 Hz, CΗ3(triphos)), δ 39.9 (q, J CP 3.2 Hz,
CΗ3C(triphos)), δ 32.6 (m, CH2Paxial), δ 33.4 (td, N ) J CPequat′
+
J CPequat′′ ) 15.3 Hz, J CPaxial 4.5 Hz, CH2Pequat), δ 32.3, δ 32.2, δ
29.6, δ 23.4, δ 20.3 (all singlets, CH2(hexyl)), δ 14.6 (s, CH3(hexyl)).
ΛΜ(nitroethane) ) 49 Ω-1 cm2 mol-1
.
(6) Hewertson, W.; Watson, R. J . Chem. Soc. 1962, 1490.
(7) Castellano, S.; Bothner-By, A. A. J . Chem. Phys. 1964, 41, 3863.
(8) (a) Stephenson, D. S.; Binsch, G. A. J . Magn. Reson. 1980, 37,
395. (b) Stephenson, D. S.; Binsch, G. A. J . Magn. Reson. 1980, 37,
409.
[(tr ip h os)Re(CO)2{CdC(H)P h }]BF 4 (3-BF 4): violet, yield
92%. Anal. Calcd for C51H45BF4O2P3Re: C, 58.02; H, 5.20.
Found: C, 57.73; H, 5.15. ΛΜ(nitroethane) ) 80 Ω-1 cm2 mol-1
.

3806 Organometallics, Vol. 15, No. 18, 1996
Bianchini et al.
Ta ble 1. 31P {1H} NMR Sp ectr a l Da ta a n d Selected IR Absor p tion s for th e Com p lexes
chem shift (ppm)a IR (cm-1
)
compd
δ(PA)
δ(PM
)
J AM (Hz)
ν(CO)
ν(other)
[(triphos)Re(CO)2{CdC(H)Ph}]Yb (3)
[(triphos)Re(CO)2{CdC(H)(p-tolyl)}]Yb,c (4)
[(triphos)Re(CO)2{CdC(H)CO2Et}]Yb (5)
-20.46
-20.27
-21.80
-15.98
-16.04
-15.22
25.5
25.6
25.9
2013, 1961
2016, 1958
2036, 1970
CdC 1654
CdC 1639
COester 1701, CdC 1607,
COC 1223
CdC 1663
[(triphos)Re(CO)2{CdC(H)C6H13}]Yb (6)
[(triphos)Re(CO)2(CdCH2)]Yb (7)
-18.99
-19.78
-16.62
-19.49
-11.18
-12.70
-9.07
-15.24
-16.23
-12.87
-16.73
-22.49
-13.82
-15.47
-19.94
-20.10
-19.00
24.2
24.5
20.6
24.3
24.5
19.1
17.1
17.5
25.6
18.9
2007, 1952
2011, 1946
1968, 1900
CdC 1624
COC 1269
[(triphos)Re(CO)2{C(OEt)(CH3)}]Yb (8)
[(triphos)Re(CO)2{CdC(H)SiMe3}]BF4 (9)
[(triphos)Re(CO)2(π-HCtCH)]BF4 (10)
d
[(triphos)Re(CO)2{C(OH)CH3}]BF4 (11)
1962, 1886
1939, 1866
1942, 1881
1937, 1879
1947, 1888
OH 3510
COacetyl 1621
CtC 2079
CtC 2081
CtC 2062, COester 1659,
COC 1200
(triphos)Re(CO)2(COCH3)d (13)
(triphos)Re(CO)2(CtCPh) (14)
(triphos)Re(CO)2{CtC(p-tolyl)} (15)
(triphos)Re(CO)2(CtCCO2Et) (16)
-7.14
-6.77
-7.60
(triphos)Re(CO)2{CtC(n-C6H13)} (17)
(triphos)Re(CO)2(CtCH) (18)
[(triphos)Re(CO)2{CdC(Me)Ph}]OSO2CF3 (19)
[(triphos)Re(CO)2{C(OEt)(CH2CO2Et)}]BPh4 (20)
-6.99
-6.79
-20.52
-18.09
-17.16
-20.08
-16.47
-13.36
17.2
17.8
25.2
21.3
1937, 1881
1926, 1875
2004, 1940
1962, 1902
CtC 2101
CtC 1954
CdC 1643
COester 1734, COC 1290
a
All measurements were recorded at room temperature in CD2Cl2 unless otherwise stated. All the 31P{1H} NMR spectra exhibit an
b
c
d
AM2 splitting pattern. Y ) BF4, BPh4. In CDCl3. In THF-d8.
[(tr ip h os)Re(CO)2{CdC(H)(p-tolyl)}]BF 4 (4-BF 4): violet,
yield 94%. Anal. Calcd for C52H47BF4O2P3Re: C, 58.38; H,
4.43. Found: C, 58.07; H, 4.38. ΛΜ(nitroethane) ) 81 Ω-1 cm2
described above, a slight excess of HCtCSiMe3 (40 µL, 0.29
mmol) and a few drops of water were added with stirring. After
being stirred for 30 min at -10 °C, the solvent was removed
in vacuo to give a rust-colored solid which was washed with
ethanol and n-pentane. The crude product was crystallized
from dichloromethane/n-hexane to afford 7-BF4 in analytically
pure form. Yield: 92%.
mol-1
.
[(tr ip h os)Re(CO)2{CdC(H)CO2Et}]BF 4 (5-BF 4): pink,
yield 92%. Anal. Calcd for C48H45BF4O4P3Re : C, 54.81; H,
4.31. Found: C, 54.69; H, 4.43. ΛΜ(nitroethane) ) 76 Ω-1 cm2
mol-1
.
Meth od B. A steady stream of ethyne was bubbled for ca.
1 min into a dichloromethane solution (10 mL) of 2 cooled at
ca. 0 °C. After ethyne was replaced by nitrogen, the solution
was heated to room temperature. The resulting red-orange
solution was stirred for 30 min, and then the solvent was
removed in vacuo to give a rust-colored residue of 7-BF4.
Crystallization from dichloromethane/n-hexane gave crystals
of 7-BF4. Yield: 90%. Anal. Calcd for C45H41BF4O2P3Re: C,
55.17; H, 4.22. Found: C, 54.85; H, 4.16. ΛΜ(nitroethane) ) 82
[(tr iph os)Re(CO)2{CdC(H)C6H13}]BF4 (6-BF4): pink, yield
89%. Anal. Calcd for C51H53BF4O2P3Re: C, 57.58; H, 5.02.
Found: C, 57.54; H, 5.12. ΛΜ(nitroethane) ) 77 Ω-1 cm2 mol-1
.
Rea ction of [(tr ip h os)Re(CO)2(η2-H2)]BF 4 (2) w ith Eth -
yn yltr im eth ylsila n e a n d Na BP h 4. Neat ethynyltrimeth-
ylsilane, HCtCSiMe3 (40 µL, 0.29 mmol), was syringed into a
dichloromethane (10 mL) solution of 2 prepared as described
above. Analogous workup gave rust-colored crystals of the
unsubstituted vinylidene complex [(triphos)Re(CO)2(CdCH2)]-
BPh4 (7-BPh4) invariably contaminated by the alkoxycarbene
complex [(triphos)Re(CO)2{C(OEt)(CH3)}]BPh4 (8-BPh4) (5-
10%) (vide infra).
Ω-1 cm2 mol-1
.
Prolonged bubbling of ethyne must be avoided as it causes
extensive decomposition of 7-BF4 to unidentified products.
The tetraphenylborate salt 7-BPh4 was obtained by crystal-
lization of the crude product from THF/n-hexane (2:1) in the
presence of NaBPh4 (1.1 equiv). Anal. Calcd for C69H61BO2P3-
Re: C, 68.37; H, 5.07. Found: C, 68.46; H, 4.90. ΛΜ(nitroethane)
Rea ction of [(tr ip h os)Re(CO)2(η2-H2)]BF 4 (2) w ith Eth -
yn yltr im eth ylsila n e in a Sea led NMR Tu be. CD2Cl2 (0.8
mL) was transferred under nitrogen into a 5-mm NMR tube
previously charged with 1 (0.025 g, 0.028 mmol). Addition of
) 53 Ω-1 cm2 mol-1 1H NMR (CD2Cl2, 22 °C, 200.13 MHz):
.
.
3.3 µL (0.027 mmol) of HBF4 OMe2 completely dissolved the
δ 1.72 (q, J HP 4.2 Hz, CH3(triphos), 3H), δ 2.67 (d, J HPaxial 4.2 Hz,
CH2Paxial, 2H), δ 2.70 (m, CH2Pequat, 4H). 13C{1H} NMR (CD2-
Cl2, 22 °C, 50.32 MHz): δ 39.8 (q, J CP 10.4 Hz, CΗ3(triphos)), δ
39.2 (q, J CP 3.0 Hz, CΗ3C(triphos)), δ 32.6-35.3 (m, CH2(triphos)).
R ea ct ion of [(t r ip h os)R e(CO)2(η2-H 2)]BF 4 (2) w it h
Eth yn e in a Sea led NMR Tu be. A solution of 2 (0.028
mmol) in CD2Cl2 (1.0 mL) was prepared in a 5-mm NMR tube
as described above. After two freeze/pump thaw cycles at -196
°C, the solution was frozen and pumped on at -196 °C. After
adding ethyne (ca. 4 equiv) via syringe, the tube was flame-
sealed and then introduced into a NMR probe precooled at -50
monohydride to give a solution of 2 which was cooled to -78
°C. After 4.0 µL (0.029 mmol) of HCtCSiMe3 was syringed
into the tube, this was flame-sealed in a dry-ice bath and then
introduced into a NMR probe precooled at -45 °C. The
1
reaction progress was monitored by variable-temperature H
and 31P{1H} NMR spectroscopy. A slow reaction occurred
already at -18 °C to give the (trimethylsilyl)vinylidene
complex [(triphos)Re(CO)2{CdC(H)SiMe3}]BF4 (9) and the
vinylidene complex [(triphos)Re(CO)2(CdCH2)]BF4 (7-BF4) in
a ratio of 1 to 1.5 since the acquisition of the first 31P{1H} NMR
spectrum. The 1H NMR spectrum showed the presence of free
hydrogen (4.61 ppm). With time the concentration of 7-BF4
increased at the expense of that of 9. Within 30 min at -15
°C, 7 was the only product detected by 31P{1H}NMR spectros-
copy. On warming of the NMR tube to room temperature, no
change in the product composition was observed. GC-MS
analysis of the reaction mixture showed the formation of
HOSiMe3 together with traces of O(SiMe3)2. NMR data for 9
(see also Tables 1 and 2): 1H NMR (CD2Cl2, -15 °C, 200.13
1
°C. The reaction was followed by variable-temperature H and
31P{1H} NMR spectroscopy. The reaction between 2 and
HCtCH already occurred at -15 °C to give an intermediate
species which we assign the formula [(triphos)Re(CO)2(π-
HCtCH)]BF4 (10). With time, 10 converted to 7-BF4.
A
complete transformation of 2 into 10 and 7-BF4 was observed
after 30 min at -15 °C, while the secondary transformation
of 10 into 7-BF4 completely occurred in further 30 min. NMR
data for 10 (see also Tables 1 and 2): 1H NMR (CD2Cl2, -15
°C, 200.13 MHz) δ 1.72 (q, J HP 1.8 Hz, CH3(triphos), 3H), δ 2.69
(m, CH2(triphos), 6H).
Rea ction of [(tr ip h os)Re(CO)2(CdCH2)]BF 4 w ith H2O
in a Sea led NMR Tu be. A 3 equiv amount of distilled water
(3.5 µL, 0.19 mmol) was introduced via syringe into a THF-d8
MHz) δ 0.35 (s, SiMe3, 9H), δ 1.66 (q, J HP 1.7 Hz, CH3(triphos)
,
3H), δ 2.62 (d, J HPaxial 9.2 Hz, CH2Paxial, 2H), δ 2.69 (m,
CH2Pequat, 4H).
Syn t h esis of [(t r ip h os)R e(CO)2(CdCH 2)]BF 4 (7-BF 4).
Meth od A. To a CH2Cl2 solution of 2 prepared at -10 °C as

Multiple Re-C Bonds
Organometallics, Vol. 15, No. 18, 1996 3807
(1.0 mL) solution of 7-BF4 (0.06 g, 0.06 mmol) in a 5-mm NMR
tube cooled at -78 °C. The tube was flame-sealed under
nitrogen and then introduced into a NMR probe at 20 °C. The
reaction was monitored at this constant temperature by 31P-
After the solvent was removed in vacuo, the off-white (oc-
casionally yellowish) residue was extracted with dichlo-
romethane (2 × 3 mL). Addition of ethanol/n-hexane (10 mL,
1:1 v/v) to the CH2Cl2 solution caused the precipitation of the
alkynyl derivatives 14-18 as off-white microcrystals. Replac-
ing solid KOtBu with LiHBEt3 or NEt3 in the above prepara-
tions gave the alkynyl derivatives in similar yields.
(tr ip h os)Re(CO)2(CtCP h ) (14): off-white, yield 90%.
Anal. Calcd for C51H44O2P3Re: C, 63.28; H, 4.58. Found: C,
63.06; H, 4.64. 1H NMR (CD2Cl2, 22 °C, 200.13 MHz): δ 1.45
(br s, CH3(triphos), 3H), δ 2.46 (m, CH2(triphos), 6H). 13C{1H} NMR
(CD2Cl2, 22 °C, 50.32 MHz): δ 40.9 (q, J CP 9.7 Hz, CΗ3(triphos)),
δ 40.1 (q, J CP 4.2 Hz, CΗ3C(triphos)), δ 36.1 (dt, J CPaxial 22.4 Hz,
1
{1H} and H NMR spectroscopy. Within 5 min a new species
was formed, which was identified as the hydroxycarbene
complex [(triphos)Re(CO)2{C(OH)CH3}]BF4 (11). The complete
conversion of 7-BF4 to 11 occurred in ca. 1 h. On long standing
in the NMR tube, the secondary transformation of 11 into the
known tricarbonyl complex [(triphos)Re(CO)3]BF4 (12)4 and
free methane (1H NMR singlet at ca. 0.18 ppm) slowly occurred
(ca. 23% conversion in 72 h as determined by 31P NMR
integration). At 60 °C, the complete transformation of 11 into
12 and free methane occurred in 30 min. NMR data for 11
(see also Tables 1 and 2): 1H NMR (THF-d8, 21 °C, 200.13
MHz) δ 1.73 (q, J HP 2.7 Hz, CH3(triphos), 3H), δ 2.74 (m,
CH2(triphos), 6H) (the resonance due to the hydroxy proton was
not observed); 13C{1H} NMR (THF-d8, 21 °C, 50.32 MHz) δ
53.6 (d, J CPtrans 5.6 Hz, CH3(carbene)), δ 40.6 (q, J CP 10.0 Hz,
CΗ3(triphos)), δ 41.0 (q, J CP 5.3 Hz, CΗ3C(triphos)), δ 36.1 (m,
CH2Paxial), δ 36.4 (td, N ) J CPequat′ + J CPequat′′ ) 14.1 Hz, J CPaxial
5.9 Hz, CH2Pequat).
J CPequat 3.0 Hz, CH2Paxial), δ 34.5 (td, N ) J CPequat + J CPequat′
15.4 Hz, J CPaxial 4.5 Hz, CH2Pequat).
)
(tr iph os)Re(CO)2{CtC(p-tolyl)} (15): off-white, yield 92%.
Anal. Calcd for C52H46O2P3Re: C, 63.60; H, 4.72. Found: C,
63.47; H, 4.81. 1H NMR (CD2Cl2, 22 °C, 299.94 MHz): δ 1.41
(br s, CH3(triphos), 3H), δ 2.41 (m, CH2(triphos), 6H). 13C{1H} NMR
(CD2Cl2, 22 °C, 50.32 MHz): δ 41.0 (q, J CP 11.1 Hz, CΗ3(triphos)),
δ 40.2 (q, J CP 2.4 Hz, CΗ3C(triphos)), δ 35.2 (br d, J CPaxial 21.0
Hz, CH2Paxial), δ 34.6 (m, CH2Pequat).
Substitution of D2O for H2O in the above reaction gave
[(triphos)Re(CO)2{C(OD)CD3}]BF4 (11-d4).
(tr ip h os)Re(CO)2(CtCCO2Et) (16): off-white, yield 92%.
Anal. Calcd for C48H44O4P3Re: C, 59.81; H, 4.60. Found: C,
59.62; H, 4.55. 1H NMR (CD2Cl2, 22 °C, 200.13 MHz): δ 1.46
(br s, CH3(triphos), 3H). 13C{1H} NMR (CD2Cl2, 22 °C, 50.32
MHz): δ 42.3 (q, J CP 8.4 Hz, CΗ3(triphos)), δ 41.9 (q, J CP 4.2 Hz,
CΗ3C(triphos)), δ 37.3 (br d, J CPaxial 23.3 Hz, CH2Paxial), δ 36.2
(td, N ) J CPequat + J CPequat′ ) 15.2 Hz, J CPaxial 6.1 Hz, CH2Pequat).
(tr ip h os)Re(CO)2{CtC(n -C6H13)} (17): off-white, yield
86%. Anal. Calcd for C51H52O2P3Re: C, 62.76; H, 5.37.
Found: C, 62.58; H, 5.50. 1H NMR (CD2Cl2, 22 °C, 200.13
MHz): δ 1.53 (br s, CH3(triphos), 3H), δ 2.46 (m, CH2(triphos), 6H).
(tr ip h os)Re(CO)2(CtCH) (18): off-white, yield 90%. Anal.
Calcd for C45H40O2P3Re: C, 60.60; H, 4.52. Found: C, 60.51;
H, 4.42. 1H NMR (CD2Cl2, 22 °C, 200.13 MHz): δ 1.44 (q, J HP
2.7 Hz, CH3(triphos), 3H), δ 2.41 (m, CH2(triphos), 6H). 13C{1H}
NMR (CD2Cl2, 22 °C, 50.32 MHz): δ 40.5 (q, J CP 9.8 Hz,
CΗ3(triphos)), δ 39.9 (q, J CP 4.3 Hz, CΗ3C(triphos)), δ 37.3 (dt, J CPaxial
Syn th esis of [(tr ip h os)Re(CO)2{C(OH)CH3}]BF 4 (11). A
10 equiv amount of water (46 µL, 2.55 mmol) was syringed
into a THF solution (3 mL) of 7-BF4 (0.25 g, 0.25 mmol) at 0
°C under vigorous stirring. Within a few minutes, the red-
orange solution turned red-yellow. Removal of the solvent in
vacuo gave a yellow-orange powder which was washed with 2
× 2 mL of a n-hexane/ethanol mixture (4:1 v/v) and then with
n-pentane (2 × 2 mL). 31P{1H} NMR analysis of this product
showed it to be a ca. 9.5:0.5 mixture of the hydroxycarbene
derivative 11 and of the acetyl derivative (triphos)Re(CO)2-
(COCH3) (13) (vide infra).
Th er m olysis of 11 in THF . A solid sample of 11 (0.10 g,
0.10 mmol; contaminated by ca. 5% of 13) was dissolved in 5
mL of THF and gently refluxed for 1 h. On cooling of the
sample to room temperature, amber colored crystals of the
tricarbonyl complex 12 separated. Yield: 90%. An indepen-
dent experiment performed on an authentic specimen of the
acetyl complex 13 showed that this product is thermally stable
in refluxig THF.
23.2 Hz, J CPequat 2.8 Hz, CH2Paxial), δ 34.3 (td, N ) J CPequat
J CPequat′ ) 14.7 Hz, J CPaxial 6.1 Hz, CH2Pequat).
+
Rea ction of (tr ip h os)Re(CO)2(CtCR) (R ) H, P h ,
p-tolyl, COOEt, n -C6H13) w ith HBF 4‚OMe2. A Schlenk flask
was charged with the appropriate alkynyl derivative (14-18)
(ca. 0.2 mmol) in dichloromethane (5 mL) at -20 °C. A 1 equiv
amount of HBF4‚OMe2 (25 µL, 0.20 mmol) was syringed under
vigorous stirring. To the resulting dark violet or pale purple
solutions was added NaBPh4 (0.10 g, 0.22 mmol) in 5 mL of
ethanol. Concentration under a brisk current of nitrogen gave
the vinylidene complexes 3-7 in almost quantitative yield.
Syn th esis of [(tr iph os)Re(CO)2{CdC(Me)P h }](OSO2CF3)
(19-OSO2CF 3). By addition of methyl triflate (45 µL, 0.41
mmol) to a solution of 14 (0.40 g, 0.41 mmol) in dichlo-
romethane (20 mL) at -20 °C, a deep violet solution was
obtained from which violet crystals of the disubstituted vi-
nylidene complex 19-OSO2CF3 separated at room temperature
after addition of ethanol (20 mL) and slow evaporation of the
solvent under a nitrogen stream. Yield: 96%. Anal. Calcd
for C53H47F3O5P3ReS: C, 56.23; H, 4.18. Found: C, 56.08; H,
4.14. The vinylidene iodide salt 19-I was obtained using CH3I
(28 µL, 0.41 mmol) instead of methyl triflate as methylating
agent. Yield: 91%. Anal. Calcd for C52H47IO2P3Re: C, 56.27;
H, 4.27. Found: C, 56.11; H, 4.20. 1H NMR (CD2Cl2, 22 °C,
299.94 MHz): δ 1.72 (q, J HP 2.8 Hz, CH3(triphos), 3H), δ 2.60 (m,
CH2Pequat, 2H), δ 2.70 (d, J HPaxial 9.4 Hz, CH2Paxial, 2H), δ 2.78
(m, CH2Pequat, 2H). 13C{1H} NMR (CD2Cl2, 25 °C, 75.42
MHz): δ 40.0 (q, J CP 10.6 Hz, CΗ3(triphos)), δ 39.8 (br s,
CΗ3C(triphos)), δ 32.8 (dt, J CPaxial 22.8 Hz, J CPequat 2.5 Hz,
CH2Paxial), δ 33.4 (td, N ) J CPequat′ + J CPequat′′ ) 15.2 Hz, J CPaxial
5.3 Hz, CH2Pequat).
Syn th esis of (tr ip h os)Re(CO)2(COCH3) (13). A slight
excess of triethylamine (45 µL, 0.32 mmol) was syringed into
a stirred THF solution (8 mL) of 11 prepared as described
above from 7-BF4 (0.25 g, 0.26 mmol) and water (14.0 µL, 0.78
mmol). Addition of n-hexane (10 mL) and evaporation of the
solvent under a brisk current of nitrogen gave a mixture of
the acetyl complex 13 and of [HNEt3]BF4. Recrystallization
of the crude reaction mixture from THF/EtOH gave yellow
crystals of 13 in 73% yield. Anal. Calcd for C45H42O3P3Re:
C, 59.40; H, 4.65. Found: C, 59.28; H, 4.72. 1H NMR (THF-
d8, 20 °C, 200.13 MHz): δ 1.44 (q, J HP 2.7 Hz, CH3(triphos), 3H),
δ 2.3-2.5 (m, CH2(triphos), 6H). 13C{1H} NMR (THF-d8, 20 °C,
50.32 MHz): δ 57.2 (d, J CPtrans 10.4 Hz, CH3(acetyl)), δ 41.3 (q,
J CP 3.7 Hz, CΗ3C(triphos)), δ 41.1 (q, J CP 9.3 Hz, CΗ3(triphos)), δ
37.7 (dt, J CPaxial 18.9 Hz, J CPequat 3.1 Hz, CH2Paxial), δ 36.9 (td,
N ) J CPequat′ + J CPequat′′ ) 14.0 Hz, J CPaxial 7.3 Hz, CH2Pequat).
Reaction of 13 with HBF4‚OMe2. A stoichiometric amount
.
of HBF4 OMe2 was syringed into a THF-d8 solution (0.8 mL)
of 13 (0.030 g, 0.033 mmol) in a 5-mm screw-cap NMR tube.
1
31P{1H} and H NMR analysis of the resulting yellow solution
showed the complete transformation of 13 into the hydroxy-
carbene complex 11.
Syn th esis of th e σ-Alk yn yl Com p lexes (tr ip h os)Re-
(CO)2(CtCR) [R ) P h (14), p-tolyl (15), COOEt (16),
n -C6H13 (17), H (18)]. A Schlenk tube was charged with the
appropriate vinylidene complex (3-7) (ca. 0.25 mmol) in THF
(5 mL) at -78 °C. Solid KOtBu (0.03 g, 0.27 mmol) was added
with stirring. As a result, an immediate reaction occurred to
give a colorless solution (occasionally pale yellow). The
reaction mixture was stirred for 30 min at room temperature.
Syn th esis of [(tr ip h os)Re(CO)2{C(OEt)(CH3)}]BF 4 (8-
BF 4). Meth od A (On e-P ot P r oced u r e). Neat ethynyltri-
methylsilane, HCtCSiMe3, (40 µL, 0.29 mmol), was syringed

3808 Organometallics, Vol. 15, No. 18, 1996
Ta ble 2. Selected 1H a n d 13C{1H} NMR Sp ectr a l Da ta for th e Com p lexesa
Bianchini et al.
1H NMR
δ (multiplicity)b
4.23 (q)
13C{1H} NMR
complex
assgnt
J (Hz)
assgnt
δ (multiplicity)b
J (Hz)
CH
J HP 2.9
CR
351.0 (dt)
J CPtrans 30.7, J CPcis 11.6
CO
191.6 (AXX′Y)
J
AX 47.4, J AX′ -12.0, J AY
8.4, J XX′ 24.9
Câ
116.3 (dt)
J CPtrans 13.3, J CPcis 2.7
CH
4.12 (q)
3.92 (q)
J HP 3.2
CR
351.9 (dt)
191.1 (AXX′Y)
J CPtrans 32.0, J CPcis 11.4
CO
J
AX 46.9, J AX′ -11.4, J AY
8.6, J XX′ 20.6
Câ
115.4 (br b)
J CPtrans 13.7
CH
CH
J HP 3.0
CR
CO
339.5 (dt)
189.6 (AXX′Y)
J CPtrans 33.8, J CPcis 10.6
J
AX 45.7, J AX′ -10.0, J AY
8.8, J XX′ 25.6
CO2Et
Câ
OCH2
CH3
CR
CO
Câ
163.4 (s)
109.2 (dt)
61.6 (br s)
15.1 (s)
344.6 (dt)
191.9 (br m)
111.5 (dt)
J CPtrans 13.9, J CPcis 2.0
3.41 (tq)
3.09 (q)
J HH 8.3, J HP 2.8
J CPtrans 32.6, J CPcis 9.9
J CPtrans 13.3, J CPcis 2.9
CdCH2
J HP 2.8
CR
CO
Câ
340.9 (dt)
191.3 (m)
95.8 (dt)
J CPtrans 32.3, J CPcis 10.7
J CPtrans 14.0, J CPcis 2.4
CH3
CH3 carbene
OCH2
0.90 (t)
2.79 (s)
4.03 (q)
J HH 7.1
J HH 7.1
RedC
306.2 (dt)
J CPtrans 37.7, J CPcis 8.3
CO
197.1 (AXX′Y)
J AX 48.2, J AX′ -12.3, J AY
9.0, J XX′ 26.1
OCH2
CH3 carbene
CH3
73.7 (s)
48.0 (dt)
14.2 (s)
J CPtrans 5.6, J CPcis 1.8
SiMe3
CH
0.35 (s)
3.14 (dt)
J HPtrans 4.3, J HPcis 1.9
HCtCH
5.27 (td)
2.82 (s)
J HPM 3.3, J HPA 2.2
CH3
RedC
296.3 (dt)
J CPtrans 32.1, J CPcis 10.3
CO
200.5 (AXX′Y)
J
AX 42.8, J AX′ -10.8, J AY
8.9, J XX′ 20.1
CH3
53.6 (d)
J CPtrans 5.0
CH3
2.53 (s)
RedC
295.5 (dt)
J CPtrans 30.1, J CPcis 9.0
CO
203.1 (AXX′Y)
J
AX 47.0, J AX′ -8.7, J AY
5.2, J XX′ 27.1
CH3
57.2 (d)
J CPtrans 10.4
CO
Câ
CR
198.4 (m)
123.8 (s)
108.7 (dt)
J CPtrans 32.8, J CPcis 14.2
CH3 p-tolyl
2.22 (s)
CO
Câ
CR
CH3 p-tolyl
198.6 (m)
116.0 (br s)
106.9 (dt)
34.5 (s)
J CPtrans 33.2, J CPcis 14.6

Multiple Re-C Bonds
Organometallics, Vol. 15, No. 18, 1996 3809
13C{1H} NMR
Ta ble 2 (Con tin u ed )
1H NMR
complex
assgnt
δ (multiplicity)b
1.21 (t)
J (Hz)
assgnt
δ (multiplicity)b
199.6 (AXX′Y)
J (Hz)
CH3 ester
J HH 7.1
CO
J AX 44.2, J AX′ -8.8, J AY
5.6, J XX′ 27.2
OCH2 ester
4.04 (q)
CO2Et
CR
168.6 (s)
123.6 (dt)
11.1 (s)
62.3 (s)
16.9 (s)
J CPtrans 33.9, J CPcis 13.3
Câ
OCH2
CH3
CH3 hexyl
CH2 hexyl
0.89 (t)
1.2-1.4 (m)
CH
2.09 (q)
2.11 (s)
J HP 2.4
CO
CR
Câ
199.0 (m)
100.3 (dt)
not detected
J CPtrans 12.8, J CPcis 1.5
CH3 vinylidene
CR
CO
349.7 (dt)
192.3 (AXX′Y)
J CPtrans 33.9, J CPcis 11.9
J
AX 55.1, J AX′ -10.7, J AY
9.3, J XX′ 23.9
Câ
122.2 (dt)
10.4 (s)
J CPtrans 13.3, J CPcis 2.7
CH3 vinylidene
CH3 ethoxy
CH3 ester
OCH2 ethoxy
OCH2 ester
CH2CO2Et
0.74 (t)
1.38 (t)
4.17 (q)
4.31 (q)
4.53 (s)
J HH 7.2
J HH 7.2
J HH 7.2
J HH 6.9
RedC
296.7 (dt)
J CPtrans 40.5, J CPcis 8.1
CO
CO2Et
196.8 (m)
189.6 (s)
75.7 (s)
63.2 (s)
63.0 (s)
14.7 (s)
14.0 (s)
OCH2 ester
OCH2 ethoxy
CH2CO2Et
CH3 ester
CH3 ethoxy
a
b
At room temperature in CD2Cl2 unless otherwise stated. Key: s, singlet; d, doublet; t, triplet; q, quartet; m, multiplet; br broad.
c
d
In CDCl3. In THF-d8.
into a dichloromethane (10 mL) solution of 2 (0.26 mmol) at
-10 °C prepared as described above. After 30 min, when all
the rhenium was present in the form of 7, ethanol (2 mL) was
added at room temperature. The reaction mixture was stirred
for 2 h during which time the red-orange color turned yellow.
Addition of ethanol/diethyl ether (10 mL, 1:2 v/v) gave the
ethoxycarbene complex 8-BF4 as light yellow crystals. Yield:
94%. Anal. Calcd for C47H47BF4O3P3Re: C, 55.03; H, 4.62.
Found: C, 54.88; H, 4.73. ΛΜ(nitroethane) (for 8-BF4) ) 76 Ω-1
cm2 mol-1. The tetraphenylborate salt 8-BPh4 can be obtained
by recrystallization of 8-BF4 from dichloromethane/ethanol (2:1
v/v) in the presence of NaBPh4 (1.1 equiv). Yield: 95%. Anal.
Calcd for C71H67BO3P3Re: C, 67.78; H, 5.37. Found: C, 67.54;
separated by addition of ethanol/diethyl ether (10 mL, 1:2 v/v).
Yield: 72%. Anal. Calcd for C74H71BO5P3Re: C, 66.81; H,
5.38. Found: C, 66.65; H, 5.46. 1H NMR (CD2Cl2, 22 °C,
299.94 MHz): δ 1.57 (br s, CH3(triphos), 3H), δ 2.57 (m, CH2(triphos)
,
6H). 13C{1H} NMR (CD2Cl2, 25 °C, 75.42 MHz): δ 39.7 (q,
J CP 10.7 Hz, CΗ3(triphos)), δ 39.5 (q, J CP 3.0 Hz, CΗ3C(triphos)), δ
32.4 (br d, J CPaxial 22.2 Hz, CH2Paxial), δ 35.3 (td, N ) J CPequat′
+ J CPequat′′ ) 14.8 Hz, J CPaxial 5.0 Hz, CH2Pequat). ΛΜ(nitroethane)
) 47 Ω-1 cm2 mol-1
.
X-r a y Diffr a ction Stu d ies. A summary of crystal and
intensity data for the compounds 3-BF4 and 8-BPh4 is pre-
sented in Table 4. Experimental data were recorded at room
temperature (21 °C) on a Enraf-Nonius CAD4 (3-BF4) or a
Philips-PW1100 diffractometer with an upgraded computer
control (FEBO system) (8-BPh4‚0.5CH2Cl2). A set of 25
carefully centered reflections in the range 7° e θ e 12° (3-
BF4) and 15.5° e θ e 18.5° (8-BPh4‚0.5CH2Cl2), respectively,
was used for determining the lattice constants. As a general
procedure, the intensities of three standard reflections were
measured periodically every 200 reflections for orientation and
intensity control. This procedure did not reveal an appreciable
decay of intensities. The data were corrected for Lorentz and
polarization effects. Atomic scattering factors were those
tabulated by Cromer and Waber9 with anomalous dispersion
corrections taken from ref 10. An empirical absorptions
correction was applied via ψ scan for compound 8-BPh4‚0.5CH2-
Cl2 with transmission factors in the range 1.006-2.158. The
computational work was performed with a Digital Dec 5000/
H, 5.36. ΛΜ(nitroethane) (for 8-BPh4) ) 50 Ω-1 cm2 mol-1
.
Meth od B. Ethanol (2 mL) was added to a solution of
isolated 7-BF4 (or 7-BPh4) (ca. 0.20 mmol) in dichloromethane
(10 mL). The solution was stirred for 2 h at room temperature
during which time the red-orange color of the initial solution
turned bright yellow. Addition of ethanol/diethyl ether (10 mL,
1:2 v/v) gave yellow crystals of 8-BF4 (or 8-BPh4) in almost
quantitative yield. 1H NMR (CD2Cl2, 28 °C, 500.13 MHz): δ
1.52 (q, J HP 2.8 Hz, CH3(triphos), 3H), δ 2.44 (m, CH2Pequat, 2H),
δ 2.50 (d, J HPaxial 8.7 Hz, CH2Paxial, 2H), δ 2.61 (m, CH2Pequat
,
2H). 13C{1H} NMR (CD2Cl2, 28 °C, 125.75 MHz): δ 40.3 (q,
J CP 9.9 Hz, CΗ3(triphos)), δ 39.6 (q, J CP 4.2 Hz, CΗ3C(triphos)), δ
33.0 (dt, J CPaxial 22.2 Hz, J CPequat 4.8 Hz, CH2Paxial), δ 35.6 (td,
N ) J CPequat′ + J CPequat′′ ) 14.9 Hz, J CPaxial 5.1 Hz, CH2Pequat).
Syn th esis of [(tr ip h os)Re(CO)2{C(OEt)(CH2CO2Et)}]-
BP h 4 (20). Ethanol was added to a solution of 5 (0.25 g, 0.19
mmol) in dichloromethane (10 mL). The reaction mixture was
stirred overnight at room temperature to give a yellow solution
from which crystals of the disubstituted carbene complex 20
(9) Cromer, D. T.; Waber, J . T. Acta Crystallogr. 1965, 18, 104.
(10) International Tables of Crystallography; Kynoch Press: Bir-
mingham, U.K., 1974; Vol. IV.

3810 Organometallics, Vol. 15, No. 18, 1996
Bianchini et al.
Ta ble 3. Selected Bon d Dista n ces (Å) a n d An gles
atoms and structure factors are available as Supporting
Information.
(d eg) for 3-BF 4 a n d 8-BP h 4‚0.5CH2Cl2
[(tr ip h os)Re(CO)2{CdC(H)P h }]BF 4 (3-BF 4). Deep-violet
crystals of the compound were grown under nitrogen from a
diluted dichloromethane/ethanol solution. A parallelepiped
crystal with dimension 0.225 × 0.200 × 0.075 mm was used
for the data collection. The structure was solved via Patterson
methods. Refinement was done by full-matrix least-squares
calculations, initially with isotropic thermal parameters and
then with anisotropic thermal parameters for all non-F and
non-H atoms. The phenyl rings were treated as rigid bodies
with D6h symmetry with C-C bond distances fixed at 1.39 Å.
The hydrogen atoms were introduced in calculated positions
(dC-H ) 0.96 Å for sp3 carbon atoms and dC-H ) 0.92 Å for sp2
carbon atoms).
[(t r ip h os)R e(CO)2{C(OE t )(CH 3)}]BP h 4‚0.5CH 2Cl2 (8-
BP h 4‚0.5 CH2Cl2). Light yellow crystals of the compound
were grown from slow concentration in the air of a dichlo-
romethane solution layered with ethanol. A parallelepiped
crystal with dimension 0.25 × 0.25 × 0.50 mm was used for
the data collection. The structure was solved by using the
heavy-atom technique and all of the non-hydrogen atoms were
found through a series of F0 Fourier maps. Full-matrix least-
squares refinement were carried out initially with isotropic
thermal parameters and then with anisotropic thermal pa-
rameters only for Re, P, and the C atoms of the ligand triphos
backbone. The phenyl rings were treated as rigid bodies with
D6h symmetry with C-C bond distances fixed at 1.39 Å, and
the hydrogen atoms were introduced in calculated positions
(dC-H ) 0.95 Å). The final difference maps revealed the
presence of a disordered molecule of dichloromethane which
was attributed a population factor of 0.5.
[(triphos)Re(CO)2{CdCH(Ph)}]BF4 (3-BF4)
Re-P1
Re-P3
Re-C7
C6-O1
C8-C9
2.469(2)
2.523(2)
1.949(7)
1.136(8)
1.289(9)
Re-P2
Re-C6
Re-C8
C7-O2
C9-C1G
2.480(2)
1.944(7)
1.925(6)
1.138(8)
1.494(11)
C8-Re-C6
C6-Re-C7
C6-Re-P1
C8-Re-P2
C7-Re-P2
C8-Re-P3
C7-Re-P3
P2-Re-P3
C9-C8-Re
87.7(3)
87.8(3)
172.0(2)
96.9(2)
174.5(2)
174.1(2)
92.3(2)
86.16(6)
173.0(6)
C8-Re-C7
C8-Re-P1
C7-Re-P1
C6-Re-P2
P1-Re-P2
C6-Re-P3
P1-Re-P3
O2-C7-Re
C8-C9-C1G
85.1(3)
91.2(2)
99.9(2)
87.1(2)
85.15(6)
97.6(2)
84.03(7)
174.1(6)
122.3(7)
[(triphos)Re(CO)2{C(OEt)CH3}]BPh4 (8-BPh4‚0.5CH2Cl2)
Re-P1
Re-P3
Re-C11
C6-O3
O3-C8
C10-O1
2.478(2)
2.478(2)
1.904(10)
1.319(10)
1.481(12)
1.180(11)
Re-P2
Re-C10
Re-C6
C6-C7
C8-C9
C11-O2
2.482(2)
1.892(9)
2.071(8)
1.478(13)
1.48(2)
1.171(11)
C10-Re-C11
C11-Re-C6
C11-Re-P1
C10-Re-P3
C6-Re-P3
C10-Re-P2
C6-Re-P2
P3-Re-P2
90.8(4)
83.9(4)
176.0(3)
178.4(3)
91.5(2)
96.7(3)
176.4(2)
84.89(8)
C10-Re-C6
87.0(4)
93.2(3)
96.1(2)
88.8(3)
87.18(7)
96.2(3)
83.54(8)
C10-Re-P1
C6-Re-P1
C11-Re-P3
P1-Re-P3
C11-Re-P2
P1-Re-P2
Ta ble 4. Su m m a r y of Cr ysta l Da ta a n d Str u ctu r e
Refin em en t for 3-BF 4, a n d 8-BP h 4‚0.5CH2Cl2
Resu lts a n d Discu ssion
3-BF4
8-BPh4‚0.5CH2Cl2
formula
fw
cryst size, mm
cryst system
space group
a, Å
C51H45BF4O2P3Re
1055.85
C71.5H68BClO3P3Re
1300.72
The preparations and the principal reactions of the
complexes described in this paper are illustrated in
Schemes 1-4. Selected NMR spectral data for the
metal complexes are collected in Table 1 (IR and 31P-
{1H} NMR) and Table 2 (1H and 13C{1H} NMR) or are
provided in the Experimental Section. 1H{31P}, 13C-
DEPT, 13C-1H-2D HETCOR, 1H-13C-2D HETCOR, and
1H-1H 2D COSY NMR spectra allowed the total and
unequivocal assignment of all hydrogen and carbon
resonances for all metal complexes.
0.225 × 0.200 × 0.075 0.25 × 0.25 × 0.50
triclinic
monoclinic
P21/c
10.2710(10)
16.3936(5)
37.257(9)
90
97.49(3)
90
6426(3)
P1h
10.693(2)
13.387(3)
17.785(4)
111.19(3)
94.10(3)
b, Å
c, Å
R, deg
â, deg
γ, deg
104.84(4)
2256.2(8)
2
1.553
2.856
V, Å3
Z
F
4
calcd, g cm-3
1.343
5.508
2704
abs coeff, mm-1
F(000)
(14) Zsolnai, L.; Pritzkow, H. ZORTEP. Ortep Original Program
Modified for PC; University of Heidelberg: Heidelberg, Germany, 1994.
(15) The literature of vinylidene complexes is extensive. Some
comprehensive reviews are as follows: (a) Bruce, M. I. Chem. Rev.
1991, 91, 197. (b) Antonova, A. B.; Ioganson, A. A. Russ. Chem. Rev.
1989, 58, 593. (c) Bruce, M. I.; Swincer, A. G. Adv. Organomet. Chem.
1983, 22, 59.
(16) Recent leading references of transition metal vinylidene com-
plexes: (a) Ara, I.; Berenguer, J . R.; Fornie´s, J .; Lalinde, E.; Tomas,
M. Organometallics 1996, 15, 1014. (b) Beddoes, R. L.; Bitcon, C.;
Grime, R. W.; Ricalton, A.; Whiteley, M. W. J . Chem. Soc., Dalton
Trans. 1995, 2873. (c) O’Connor, J . M.; Hu¨bner, K.; Merwin, R.; Pu,
L. J . Am. Chem. Soc. 1995, 117, 8861. (d) Bianchini, C.; Innocenti, P.;
Peruzzini, M.; Romerosa, A.; Zanobini, F. Organometallics 1996, 15,
272. (e) Esteruelas, M. A.; Lahoz, F. J .; On˜ate, E.; Oro, L. A.; Valero,
C.; Zeier, B. J . Am. Chem. Soc. 1995, 117, 7935. (f) Wiedemann, R.;
Wolf, J .; Werner, H. Angew. Chem., Int. Ed. Engl. 1995, 34, 1244. (g)
Werner, H. J . Organomet. Chem. 1994, 475, 45. (h) Touchard, D.;
Haquette, P.; Pirio, N.; Toupet, L.; Dixneuf, P. H. Organometallics
1993, 12, 3132. (i) Bianchini, C.; Peruzzini, M.; Romerosa, A.; Zanobini,
F. Organometallics 1995, 14, 3152. (j) Bianchini, C.; Glendenning, L.;
Peruzzini, M.; Romerosa, A.; Zanobini, F. J . Chem. Soc., Chem.
Commun. 1994, 2219.
1054
θ range, deg
index ranges
2.50-24.96
-12 e h e 12
-15 e k e 14
0 e l e 19
6802
6524 (Rint ) 0.0257)
full-matrix least
squares on F2
6522/0/572
2.87-55.03
-10 e h e 10
0 e k e 17
0 e l e 39
7556
7429 (Rint ) 0.0183)
full-matrix least
squares on F2
7423/0/259
reflcns collcd
indepdt reflcns
refinement method
data/constraints/
params
goodness-of-fit on F2
final R indices
[I > 2σ(I)]
1.447
R1 ) 0.0336
1.045
R1 ) 0.0648
wR2 ) 0.0852
R1 ) 0.0508
wR2 ) 0.0901
wR2 ) 0.1616
R1 ) 0.0668
wR2 ) 0.1665
1.697
R indices (all data)
largest diff peak, e Å3 1.814
largest diff hole, e Å-3 -0.937
-0.879
200 workstation using the programs SHELX76,11 SHELX93,12
ORTEP,13 and ZORTEP.14 Final atomic coordinates of all
(17) For leading references on the alkyne to vinylidene tautomer-
ization, see: (a) Fryzuk, M. D.; Huang, L.; McManus, N. T.; Paglia,
P.; Rettig, S. J .; White, G. S. Organometallics 1992, 11, 2979. (b)
Lumphrey, J . R.; Selegue, J . P. J . Am. Chem. Soc. 1992, 114, 5518. (c)
Werner, H. Angew. Chem., Int. Ed. Engl. 1990, 29, 1077. (d) Bianchini,
C.; Peruzzini, M.; Vacca, A.; Zanobini, F. Organometallics 1991, 10,
3697. (e) Xiao, J .; Cowie, M. Organometallics 1993, 12, 463. (f) Davies,
S. G.; McNally, J . P.; Smallridge, A. J . Adv. Organomet. Chem. 1990,
30, 30. (g) Bullock, R. M. J . Chem. Soc., Chem. Commun. 1989, 165.
(11) Sheldrick, G. M. SHELX-76. A Program for Crystal Structure
Determination; University of Cambridge: Cambridge, U.K., 1976.
(12) Sheldrick, G. M. SHELX-93. Program for Structure Refinement;
University of Go¨ttingen: Go¨ttingen, Germany, 1993.
(13) J ohnson, C. K. Report ORNL-5138; Oak Ridge National
Laboratory: Oak Ridge, TN, 1976.

Multiple Re-C Bonds
Organometallics, Vol. 15, No. 18, 1996 3811
Sch em e 1
stricted rotation have been reported, i.e. the rhenium
compounds [(η5-Cp)Re(NO)(PPh3)(CdCHR)]+ described
by Gladysz for which the existence of a mixture of
rotamers at room temperature has been demonstrated
by NMR spectroscopy.21
The presence of vinylidene ligands in 3-6 is unam-
1
biguously shown by H NMR resonances at ca. 4 ppm
due to the vinylidene hydrogen15-17 and by 13C NMR
resonances at ca. 350 ppm (CR) and ca. 110 ppm (Câ),
which appear as doublets of triplets due to coupling of
both vinylidene carbon atoms to the phosphorus nu-
clei.15,16,22 Two phosphorus nuclei are trans to the
carbonyl ligands which are thus magnetically inequiva-
lent (AXX′Y multiplets at ca. 190 ppm). Analogous spin
systems have been reported by Baird and co-workers
for the isoelectronic ruthenium complexes [(triphos)Ru-
(CO)2X]n+ (X ) halide or organyl).23 Finally, medium-
intensity IR absorptions in the region 1600-1660
cm-1 16,22 and a pair of strong bands near 2000 cm-1
characterize the vinylidene CdC bond and the terminal
carbonyls, respectively.
The molecular structure of the phenylvinylidene
complex 3-BF4 has been determined by an X-ray dif-
fraction analysis. The crystal structure consists of
[(triphos)Re(CO)2{CdC(H)Ph}]+ cations and tetrafluo-
roborate anions in a 1:1 ratio. A selected list of bond
angles and distances is given in Table 3, while an
ORTEP view of the complex cation is shown in Figure
1 with the atomic labeling scheme.
The coordination geometry around rhenium can be
described as a slightly distorted octahedron with the
metal atom surrounded by the three P donor atoms of
triphos, by two mutually cis carbonyl ligands, and by a
σ-bonded phenylvinylidene group. The most relevant
distortions from the idealized geometry are related to
the structural constraints imposed by the tripodal
phosphine. This is confirmed by the bending of the
three P-Re-P angles which are significantly smaller
than 90° (average value 85.1°).4,24 The overall donor-
atom set around rhenium is quite symmetrical with a
negligible displacement [0.001(3) Å] of the metal from
the orthogonal planes P1-P2-C6-C7 and P3-P2-C8-
C7, while a slightly larger displacement [0.0045(3)] Å
is observed with respect to the P3-P1-C8-C6 plane.
The Re-P bond lengths [d(Re-P)av ) 2.49 Å] are signifi-
Syn th esis an d Ch ar acter ization of th e Vin yliden e
Com p lexes [(tr ip h os)Re(CO)2{CdC(H)R}]Y. (Y )
BF 4, BP h 4; R ) P h (3), p-tolyl (4), COOEt (5),
n -C6H13 (6), H (7)). Scheme 1 illustrates the one-pot
reaction which converts the Re(I) hydride complex
[(triphos)Re(CO)2H] (1) to the vinylidene derivatives
[(triphos)Re(CO)2{CdC(H)R}]Y (Y ) BF4, BPh4; R ) Ph
(3), p-tolyl (4), COOEt (5), n-C6H13 (6)) by sequential
action of a protic acid and a terminal alkyne. The
reactions proceed via the intermediacy of the isolable
complex [(triphos)Re(CO)2(η2-H2)]+,4 which undergoes
displacement of the η2-H2 ligand by the terminal alkynes.
The latter molecules most likely form π-adducts prior
to tautomerism to vinylidene ligands by 1,2-hydrogen
shift which is the mechanism generally followed by d6
metal systems.15-17 In actuality, a π-alkyne intermedi-
ate has been intercepted at low temperature with
ethyne (vide infra).
Despite the different electronic properties of the
vinylidene substituents, compounds 3-6 exhibit very
similar NMR characteristics. All 31P{1H} NMR spectra
show first-order AM2 spin systems with chemical shifts
and coupling constants, which are in line with those of
Re(I) phosphine complexes.4 The substantial negligibil-
ity of coordination chemical shift [∆δ(31P) ) δ(31Pcoord
)
- δ(31Pfree ligand) e 20 ppm]18 well accounts for the
deshielding effect of coordinated 31P nuclei observed for
5d-block metal phosphine complexes.19 The 31P{1H}
NMR spectra of the vinylidene complexes are temper-
ature invariant down to -90 °C, consistent with a low-
energy rotational barrier separating the different rot-
amers I and II.
(19) See, for example: (a) Pregosin, P. S.; Kunz, R. W. 31P and 13C
NMR of Transition Metal Phosphine Complxes; Diehl, P., Fluck, E.,
Konsfeld, R., Eds.; Springer-Verlag: Berlin, Heidelberg, New York,
1979. (b) Crumbliss, A. L.; Topping, R. J . Phosphorus-31 NMR
Spectroscopy in Stereochemical Analysis; Verkade, J . G., Quin, L. D.,
Eds.: VCH Publ. Inc.: Deerfield Beach, FL, 1987.
(20) Kostic´, N. M.; Fenske, R. F. Organometallics 1982, 1, 974.
(21) (a) Wong, A.; Gladysz, J . A. J . Am. Chem. Soc. 1982, 104, 4948.
(b) Senn, D. R.; Wong, A.; Patton, A. T.; Marsi, M.; Strouse, C. E.;
Gladysz, J . C. J . Am. Chem. Soc. 1988, 110, 6096. (c) Kowalczyk, J . J .;
Arif, A. M.; Gladysz, J . A. Organometallics 1992, 11, 3635. (d)
Ramsden, J . A.; Weng, W.; Bartik, T.; J ohnson, M. T.; Arif, A. M.;
Gladysz, J . A. Organometallics 1995, 14, 839.
(22) See, for example: (a) Bianchini, C.; Meli, A.; Peruzzini, M.;
Zanobini, F.; Zanello, P. Organometallics 1990, 9, 241. (b) Gamasa,
M. P.; Gimeno, J .; Ma´rtin-Vaca, B. M.; Borge, J .; Ga´rcia-Granda, S.;
Perez-Carren˜o, E. Organometallics 1994, 13, 4045. (c) Wolf, J .; Lass,
R. W.; Manger, M.; Werner, H. Organometallics 1995, 14, 2649 and
references therein.
(23) Hommeltoft, S. I.; Cameron, A. D.; Shackleton, T. A.; Fraser,
M. E.; Fortier, S.; Baird, M. C. Organometallics 1986, 5, 1380.
(24) Recent, representative examples: (a) Kowalski, A.; Ashby, M.
T. J . Am. Chem. Soc. 1995, 117, 12639. (b) Bianchini, C.; Meli, A.;
Peruzzini, M.; Vizza, F.; Moneti, S.; Herrera, V.; Sa´nchez-Delgado, R.
J . Am. Chem. Soc. 1994, 116, 4370. (c) Ghilardi, C. A.; Innocenti, P.;
Midollini, S.; Orlandini, A.; Vacca, A. J . Chem. Soc., Dalton Trans.
1995, 1109. (d) Costello, M. T.; Fanwick, P. E.; Green, M. A.; Walton,
R. A. Inorg. Chem. 1992, 31, 2359.
A rapid rotation of the vinylidene group about the
M-C axis characterizes most of the known metal
complexes and has also been rationalized by means of
theoretical studies.20 However, some examples of re-
(18) The chemical shift of triphos phosphorus atoms in dichlo-
romethane-d2 is -25.2 ppm.

3812 Organometallics, Vol. 15, No. 18, 1996
Bianchini et al.
phosphine ligands, III [1.33(3) Å],27 [CpRe(NO)(PPh3)-
{CdCH(1-C10H7)}]BPh4 (IV) [1.387(17) Å],21b and trans-
[ReCl{CdCH(Ph)}(dppe)2] (V) [1.31(2) Å] [dppe ) 1,2-
bis(diphenylphosphino)ethane].25e,f
Finally, the crystal packing appears to be dictated by
van der Waals interactions with no anomalous inter-
molecular contacts.
Unlike all the other vinylidene complexes, the one
obtained by reaction of 2 in CH2Cl2 with ethynyltri-
methylsilane is highly reactive toward moisture. In
fact, the complex [(triphos)Re(CO)2{CdC(H)SiMe3}]BF4
(9) is seen only as a transient species, which quite
rapidly transforms into the parent vinylidene derivative
[(triphos)Re(CO)2(CdCH2)]BPh4 (7-BPh4) and HOSiMe3
even at -18 °C (Scheme 1). Consistently, in the
presence of stoichiometric water, 9 is not intercepted
even at low temperature (NMR experiment). The facile
hydrolysis of C(sp2)-Si bonds in metal complexes is well
documented in the literature.28 Despite its transient
nature which does not allow one to record 13C NMR
spectra, 9 can unequivocally be assigned the same
structure of the previously described vinylidene com-
plexes in which the metal center is octahedrally coor-
dinated by a fac triphos ligand, by two cis disposed
carbonyls group, and by a vinylidene ligand trans to a
phosphorus atom. In particular, the resonance of the
vinylidene hydrogen in 9 appears as a doublet of triplets
at 3.14 ppm (J HPtrans 4.3 Hz, J HPcis 1.9 Hz) and collapses
Figu r e 1. ORTEP drawing of the complex cation [(triphos)-
Re(CO)2{CdC(H)Ph}]+ in 3-BF4. All of the phenyl rings of
the triphos ligand are omitted for clarity.
catively longer than those found in the monohydride
(triphos)Re(CO)2H [d(Re-P)av ) 2.42 Å]4,24 but compare
well with the analogous distances in [(triphos)Re(CO)2-
{C(OEt)Me}]BPh4 [d(Re-P)av ) 2.48 Å] (vide infra). The
Re-P1 and Re-P2 distances are similar [2.469(2) and
2.480(2) Å, respectively] and shorter than the Re-P3
separation [2.523(2) Å], which is consistent with the
smaller trans influence of the vinylidene ligand.
The phenylvinylidene ligand shows the typical geo-
metrical features of this organyl moiety17d,25 with metri-
cal data which are consistent with sp and sp2 hybrid-
izations of the C8 and C9 carbon atoms, respectively.
Accordingly, the angle at the Câ carbon, C8-C9-C1G,
measures 122.3(7)°. The Re-C8 bond distance [1.925-
(6) Å] is considerably shorter than those found in Re-C
single bond compounds26 and is close to the separation
found in [Cp(CO)2Re{CdCPhCPhdCH2}][(CO)2ReCp]27
[1.90(2) Å] (III). As a consequence of the trans influence
1
to a singlet in the broad-band phosphorus-decoupled H
spectrum. Identical primary geometry is adopted by the
parent vinylidene complex [(triphos)Re(CO)2(CdCH2)]-
BF4 (7-BF4), whose geminal vinylidene protons appear
1
in the H NMR spectrum as a quartet (3.09 ppm, J HP
2.8 Hz) which, in a 2D-NMR H,C-HETCOR experiment,
correlates with a doublet of triplets at 95.8 ppm (CdCH2).
Consistent with its methylenic nature, this signal is
antiphased in the 13C-DEPT spectrum.
In addition to hydrolysis of 9, the parent vinylidene
complex can straightforwardly be prepared by treatment
of 2 in CH2Cl2 with ethyne (Scheme 2).
A variable-temperature NMR study of the reaction
between 2 and ethyne has provided valuable mechanis-
tic information on the formation of the vinylidene
complex. At -18 °C, the formation of the vinylidene
complex 7 is preceded by that of the kinetic η2-alkyne
product [(triphos)Re(CO)2(π-HCtCH)]BF4 (10), which
spontaneously transforms into the vinylidene complex
7 within 1 h.
Although it was not possible to record a 13C NMR
spectrum of the kinetic product, 10, there is little doubt
that this complex contains a π-bonded ethyne molecule.
In fact, the 31P NMR resonance of the phosphorus donor
trans to the ethyne ligand in 10 (PA) is shifted downfield
as compared to the analogous resonance in the vi-
nylidenes 3-7 due to the higher π acidity of the
vinylidene ligands.15,16 Moreover, the 1H NMR spec-
trum contains a resonance at δ 5.27 (td, J HPM 3.3 Hz,
J HPA 2.2 Hz) which fall in the proper region for two-
electron donor π-HC≡CH ligands;17b,29 see for example
[CpRe(CO)2(η2-C2H2)] (δCH 5.61)30 and [CpRu(PMe2Ph)2-
of the P3 phosphorus atom, the C8-C9 bond length
[1.289(9) Å] is slightly shorter than those found in other
X-ray-authenticated Re(I) vinylidenes without trans
(25) X-ray-authenticated phenylvinylidene complexes include: (a)
Beevor, R. G.; Green, M.; Orpen, A. G.; Williams, J . D. J . Chem. Soc.,
Chem. Commun. 1983, 673. (b) Beevor, R. G.; Green, M.; Orpen, A.
G.; Williams, J . D. J . Chem. Soc., Dalton Trans. 1987, 319. (c) Wolf,
J .; Werner, H.; Serhadli, O.; Ziegler, M. L. Angew. Chem., Int. Ed. Engl.
1983, 22, 414. (d) Werner, H.; Wolf, J .; Alonso, J . G.; Ziegler, M. L.;
Serhadli, O. J . Organomet. Chem. 1987, 397, 336. (e) Pombeiro, A. J .
L.; J effrey, J . C.; Pickett, C. J .; Richards, R. L. J . Organomet. Chem.
1984, 277, C7. (f) Pombeiro, A. J . L.; Almeida, S. S. P. R.; Silva, M. F.
C. G.; J effrey, J . C.; Richards, R. L. J . Chem. Soc., Dalton Trans. 1989,
2381. (g) Werner, H.; Stark, A.; Schulz, M.; Wolf, J . Organometallics
1992, 11, 1126. (h) Schumann, H.; Admiral, G.; Beurskens, P. T. Z.
Naturforsch. 1992, 47B, 1125. (i) Aleksandrov, G. G.; Antonova, A. B.;
Kolobova, N. E.; Struchov, Yu. T. Koord. Khim. 1976, 2, 1684. (j)
Burrell, A. K.; Bryan, J . C.; Kubas, G. J . Organometallics 1994, 13,
1067. (k) LeLagadec, R.; Roman, E.; Toupet, L.; Muller, U.; Dixneuf,
P. H. Organometallics 1994, 13, 5030.
(28) (a) Barbaro, P.; Bianchini, C.; Peruzzini, M.; Polo, A.; Zanobini,
F. Inorg. Chim. Acta 1994, 220, 5. (b) Rappert, T.; Nu¨rnberg, O.;
Werner, H. Organometallics 1993, 12, 1359. (c) Bruce, M. I.; Koutsan-
tonis, G. A. Aust. J . Chem. 1991, 44, 207.
(26) Orpen, A. G.; Brammer, L.; Allen, F. H.; Kennard, O.; Watson,
D. G. J . Chem. Soc., Dalton Trans. 1989, S1.
(27) Kolobova, N. E.; Antonova, A. B.; Khitrova, O. M.; Antipin, M.
Yu.; Struchkov, Yu. T. J . Organomet. Chem. 1977, 137, 69.
(29) (a) Templeton, J . L. Adv. Organomet. Chem. 1989, 29, 1. (b)
Templeton, J . L.; Ward, B. C. J . Am. Chem. Soc. 1980, 102, 3288.
(30) Alt, H. G.; Engelhardt, H. E. J . Organomet. Chem. 1988, 342,
176.

Multiple Re-C Bonds
Organometallics, Vol. 15, No. 18, 1996 3813
Sch em e 2
(η2-C2H2)] (δCH 5.27).17b Like 10, the ruthenium complex
rearranges to its vinylidene tautomer above 60 °C.
In an attempt to isolate 10, cold n-hexane was added
to a solution of 2 and HC≡CH thermostated at -15 °C
until precipitation of a yellowish solid occurred. This
solid contains 10 and 7-BF4 in a 1:4 ratio (31P NMR
integration). More importantly, the IR spectrum shows
a band at 1740 cm-1 which may tentatively be assigned
to the C≡C stretching frequency of the π-coordinated
ethyne ligand.17b,29
The interception of the kinetic product 10 suggests
that the present Re-assisted 1-alkyne to vinylidene
tautomerization reactions proceed via the 1,2-H shift
mechanism proposed in 1985 by J erome and Hoffmann31
on the basis of EHMO calculations and recently sup-
ported by ab initio studies on the conversion of RuCl2-
(PH3)2(HCtCH) to RuCl2(PH3)2(CdCH2).32 In actuality,
the alternative intramolecular 1,3-H shift mechanism
would hardly be accessible to the present [(triphos)Re-
(CO)2]+ fragment, which is not sufficiently electron-rich
to undergo the oxidative addition of the alkyne C-H
bond. As a matter of fact, the only known d6 metal
system which has been found capable of tautomerizing
a terminal alkyne to vinylidene via a 1,3-H shift
mechanism is the very electron-rich Ru system [(C5Me5)-
RuCl(dippe)] reported by Puerta and co-workers (dippe
) 1,2-bis(diisopropylphosphino)ethane).33
With the exception of 9, excellent stability in both the
solid state and solution characterizes all the members
of the present family of vinylidene complexes. This
feature and the general synthetic methodology herein
described provide facile access to a large variety of Re-
(I) vinylidene complexes, the chemistry of which still is
at an early stage of development. Moreover, with the
exception of the neutral complexes trans-ReCl{CdC-
t
(H)R}(dppe)2 (VIII) (R ) Ph, Et, Bu, SiMe3, COOMe,
COOEt, C6H10OH) described by Pombeiro et al.,25f all
the other known Re vinylidene complexes, reported by
Gladysz,21 Casey,35 Geoffroy,34 and Kolobova,27 contain
as ancillary ligands either cyclopentadienyl or substi-
tuted cyclopentadienyl rings, which are less thermally
and chemically stable than triphos.
Rea ction s of th e Vin ylid en e Com p lexes. The
following sections describe selected examples of chemical
transformations occurring at the vinylidene ligands
bound to the [(triphos)Re(CO)2]+ auxiliary.
Syn th esis, Ch a r a cter iza tion , a n d Rea ctivity of
t h e Secon d a r y H yd r oxyca r b en e Com p lex [(t r i-
p h os)Re(CO)2{C(OH)CH3}]BF 4 (11). Treatment of
the parent vinylidene complex 7-BF4 in THF with an
excess of water at g0 °C results in the transformation
of the starting compound into the secondary hydroxy-
carbene complex [(triphos)Re(CO)2{C(OH)CH3}]BF4 (11)
(Scheme 2). In situ NMR experiments show that the
addition of water to 7-BF4 (see trace “B” in Figure 2) is
a selective reaction.36-39 In contrast, 11, isolated by
removal of the solvent in vacuo, is invariably contami-
nated by some acetyl derivative (triphos)Re(CO)2-
(COCH3) (13) (e10%) whose formation, however, is an
indirect evidence of the nature of 11 (vide infra).
Complex 7 is the first parent Re vinylidene complex
directly accessible by displacement of a labile ligand by
ethyne. Moreover, unlike the Gladysz derivative [(η5-
21b
Cp)Re(NO)(PPh3)(CdCH2)]OSO2CF3
(VI), which re-
(35) Casey, C. P.; Ha, Y.; Powell, D. R. J . Organomet. Chem. 1994,
472, 185.
(36) Buhro, W. E.; Wong, A.; Merrifield, J . H.; Lin, G.-Y.; Constable,
A. C.; Gladysz, J . A. Organometallics 1983, 2, 1852.
(37) Tam, W.; Lin, G.-Y.; Wong, W.-K.; Kiel, W. A.; Wong, V. K.;
Gladysz, J . A. J . Am. Chem. Soc. 1982, 104, 141.
(38) Green, M. L. H.; Hurley, C. R. J . Organomet. Chem. 1967, 10,
188.
quires rigorous anaerobic and moisture-free conditions
for its preparation, and the Geoffrey compound (η5-Cp)-
Re(CO)2(CdCH2)34 (VII), which decomposes in solution
at room temperature, 7 is sufficiently air- and moisture-
stable in the solid state to be handled in a laboratory
with no particular care.
(39) For other examples of hydroxycarbene complexes, see: (a) Lilga,
M. A.; Ibers, J . A. Organometallics 1985, 4, 590. (b) Catheline, D.;
Lapinte, C.; Astruc, D. C. R. Acad. Sci. Paris 1985, 301, II, 479. (c)
Guerchais, V.; Lapinte, C. J . Chem. Soc., Chem. Commun. 1986, 663.
(d) Grundy, V. K.; J enkins, J . J . Organomet. Chem. 1984, 265, 77. (e)
Barrott, D. S.; Cole-Hamilton, D. J . J . Organomet. Chem. 1986, 306,
C41. (f) Barrott, D. S.; Glidewell, C.; Cole-Hamilton, D. J . J . Chem.
Soc., Dalton Trans. 1988, 1079. (g) Casey, C. P.; Sakaba, H.; Underiner,
T. L. J . Am. Chem. Soc. 1991, 113, 6673. (h) Green, M. L. H.; Mitchard,
L. C.; Swanwick, M. G. J . Chem. Soc. A 1971, 794. (i) Fischer, E. O.;
Kreis, G.; Kreissl, F. R. J . Organomet. Chem. 1973, 56, C37. (j) Darst,
K. P.; Lenhert, P. G.; Lukehart, C. M.; Warfield, L. T. J . Organomet.
Chem. 1980, 195, 317. (k) Powell, J .; Farrar, D. H.; Smith, S. J . Inorg.
Chim. Acta 1984, 85, L23. (l) Gibson, D. H.; Mondal, S. K.; Owens, K.;
Richardson, J . F. Organometallics 1990, 10, 1936.
(31) Silvestre, J .; Hoffmann, R. Helv. Chim. Acta 1985, 68, 1461.
(32) Wakatsuki, Y.; Koga, N.; Yamazaki, H.; Morokuma, K. J . Am.
Chem. Soc. 1994, 116, 8105.
(33) de los Rios, I.; J imenez-Tenorio, M.; Puerta, M. C.; Valerga, P.
J . Chem. Soc., Chem. Commun. 1995, 1757.
(34) Terry, M. R.; Mercando, L. A.; Kelley, C.; Geoffroy, G. L.;
Nombell, P.; Lugan, N.; Mathieu, R.; Ostrander, R. L.; Owens-
Waltermire, B. E.; Rheingold, A. L. Organometallics 1994, 13, 843.
(40) Bianchini, C.; Casares, J . A.; Peruzzini, M.; Romerosa, A.;
Zanobini, F. J . Am. Chem. Soc. 1996, 118, 4585.

3814 Organometallics, Vol. 15, No. 18, 1996
Bianchini et al.
F igu r e 2. 31P{1H} NMR spectra of the stepwise reaction 2
9 9 9
i8 7 ii8 11 iii8 13 carried out by sequential addition to 2 of C2H2
(i), H2O (ii), and NEt3 (iii) (5-mm screw-cap NMR tube, THF-d8, 21 °C, 81.01 MHz, 85% H3PO4 reference).
The presence of a hydroxycarbene ligand in 11 is
Hydroxycarbene metal complexes are still rare
species.36-39 With the exception of (η5-C5Me5)Fe(CO)2-
(CHOH), prepared by hydride abstraction from a hy-
droxymethyl ligand,39c all the known, authentic, hy-
droxycarbene complexes have been generated by reaction
of either η1-formyl or η1-acyl precursors with strong
protic acids.36-39 Compound 11 thus represents the first
example of generation of a stable hydroxycarbene ligand
by direct addition of water to a vinylidene ligand.
unequivocally demonstrated by a 13C NMR resonance
2
2
at 296.3 ppm (dt, J CPtrans 32.1 Hz, J CPcis 10.3 Hz) that
can readily be assigned to the carbene carbon atom,2f,36,37
which couples to the triphos phosphorus nuclei (slightly
second-order 31P NMR AB2 pattern; see trace “C” in
Figure 2). In the 1H NMR spectrum, the resonance due
to the carbene CH3 substituent appears as a singlet at
2.82 ppm,36,38 which, in fact, disappears in the spectrum
of the perdeuterated isotopomer [(triphos)Re(CO)2-
{C(OD)CD3}]BF4 (7-d4) obtained by reacting 7-BF4 with
D2O (exchange of the vinylidene hydrogens with deu-
terium40 evidently occurs prior to interaction of water
with the RedCdC moiety). The hydroxycarbene OH
The evident interconnection of vinylidene and hy-
droxycarbene ligands is quite interesting as both these
species are believed to play a key role in the hydrogena-
tion of CO catalyzed by iron-group metals to give a
variety of organic products.41,42 In particular, surface-
bound secondary hydroxycarbene ligands have been
postulated in forming the initial C-H bonds in Fischer-
Tropsch reactions.43,44 Accordingly, in light of our
discovery, one cannot disregard the possibility that
water (produced in the Fischer-Tropsch process)45
interacts with vinylidene intermediates to give hydroxy-
carbene species, which ultimately may generate either
hydrocarbons and CO or other oxygenated products such
as aldehydes and ketones. As a matter of fact, we have
found that the hydroxycarbene ligand in 11 is selectively
transformed into CO and methane by thermolysis in
THF.
1
resonance was not detected in the H NMR spectrum
of 11. However, the compound shows a broad absorp-
tion at ca. 3500 cm-1 in its IR spectrum, which we
36-38
assign as νOH
.
Compound 11 is fairly stable in solution at room
temperature. On long standing, however, it decomposes
to the know tricarbonyl complex [(triphos)Re(CO)3]BF4
1
(12)5 and methane (detected by H NMR) (23% conver-
sion in 72 h). In refluxing THF, this transformation
quantitatively occurs in a few minutes (Scheme 2).
Deprotonation of 11 in THF to the acetyl complex 13
rapidly and selectively occurs by treatment with mild
bases such as NEt3 (see trace “D” in Figure 2). Com-
pound 13, isolated as yellow crystals, is reversibly
.
protonated by strong acids (HBF4 OMe2) in THF to
(41) (a) Hoel, E. L.; Anselt, G. B.; Leta, S. Organometallics 1986, 5,
585. (b) Hoel, E. L. Organometallics 1986, 5, 587.
(42) (a) Starch, H. H.; Golumbis, H.; Anderson, R. B. The Fischer-
Tropsch and Related Syntheses; Wiley: New York, 1951. (b) Kummer,
J . T.; Emmett, P. M. J . Am. Chem. Soc. 1953, 75, 5177. (c) Nijs, H. H.;
J acobs, P. A. J . Catal. 1980, 66, 401.
(43) Collmann, J . P.; Hegedus, L. S.; Norton, J . R.; Finske, R. G.
Principles and Applications of Organotransition Metal Chemistry;
University Science Books: Mill Valley, CA, 1987.
(44) (a) Olah, G. A.; Molna´r, A. Hydrocarbon Chemistry; Wiley: New
York, 1995; Chapter 3, pp 66-73. (b) Turner, M. L.; Long, H. C.;
Sherton, A.; Byers, P. K.; Maitlis, P. M. Chem. Eur. J . 1995, 1, 549.
(45) (a) Brady, R. C.; Pettit, R. J . Am. Chem. Soc. 1980, 102, 6181.
(b) Brady, R. C.; Pettit, R. J . Am. Chem. Soc. 1981, 103, 1297. (c) Biloen,
P. J . R. Neth. Chem. Soc. 1980, 99, 33. (d) Biloen, P. J .; Sachter, W.
M. H. Adv. Catal. 1981, 30, 165.
regenerate the hydroxycarbene precursor.39l The main
spectroscopic properties of 13 are similar to those of all
the present neutral complexes containing the [(triphos)-
Re(CO)2]+ auxiliary. The acetyl ligand is readily rec-
ognized by a 13C NMR resonance at 265.5 ppm (dt,
2
2J CPtrans 30.1 Hz, J CPcis 9.0 Hz) due to the COCH3
1
carbon atom, by a H NMR singlet at 2.53 ppm due to
the Re-COCH3 acetyl protons, and by an IR νCdO
absorption at 1621 cm-1 36
The facile deprotonation of
.
11 accounts for the observed formation of some 13 in
any attempt to isolate 11 from its solutions.

Multiple Re-C Bonds
Organometallics, Vol. 15, No. 18, 1996 3815
Sch em e 3
The cleavage of the C-C bond in vinylidene ligands
by water has a few precedents in the literature.40,46,47
A mechanistic study has recently been carried out on
the reaction which converts the Ru vinylidene complex
fac,cis-(PNP)RuCl2{CdC(H)Ph} to the carbonyl complex
fac,cis-(PNP)RuCl2(CO) and toluene by treatment with
water [PNP ) CH3CH2CH2N(CH2CH2PPh2)2].40 A num-
ber of key intermediates were intercepted, including
σ-acyl and alkylcarbonyl species, but the intermediacy
of a hydroxycarbene complex was only postulated. The
present discovery thus confirms that hydroxycarbene
species can be precursors to the C-C bond cleavage
step.
p-tolyl (15), COOEt (16), n -C6H13 (17), H (18)]. The
monosubstituted vinylidene complexes 3-7 are readily
deprotonated by bases (KOtBu, NEt3, LiCtCPh, LiH-
BEt3) to give σ-alkynyl derivatives of the general
formula (triphos)Re(CO)2(CtCR) [R ) Ph (14), p-tolyl
(15), COOEt (16), n-C6H13 (17), H (18)] (Scheme 3).
All the alkynyl complexes show a strong IR νCtC
absorption between 2062 and 2101 cm-1. The parent
ethynyl complex 18 displays C-H and CtC stretching
modes at 3280 and 1954 cm-1, respectively. The red-
shift observed for the νCtC frequency in 18 is due to the
less electron-rich character of the unsubstituted alkynyl
ligand. In accord with the lack of charge as well as the
major basicity of the alkynyl ligands, the νCtO stretching
frequencies of the carbonyl ligands are shifted to lower
energy as compared to the corresponding vinylidene
precursors [∆ν ) ν(CtO)vinylidene - ν(CtO)alkynyl > 70 cm-1].
The 31P NMR spectra display the expected AM2 patterns
in which the triplet resonance of the phosphorus donor
trans to the σ-organyl ligand is shifted to lower field as
compared to the vinylidene precursors, most likely due
to the greater trans influence of the σ-alkynyl groups.52
Rea ction s of th e σ-Alk yn yl Com p lexes w ith Elec-
tr op h iles. The alkynyl complexes 14-18 regenerate
the vinylidene precursors by reaction with protic acids
which regioselectively attack the Câ carbon atom (Scheme
3). In a similar way, the reaction of the alkynyl
complexes with carbon electrophiles provides a simple
and convenient route to the synthesis of disubstituted
vinylidene derivatives. As an example, the reaction of
14 with different methylating reagents, such as MeOSO2-
CF3, Me3OBF4, or MeI, gives the cationic methylphe-
nylvinylidene species [(triphos)Re(CO)2{C)C(Me)Ph}]Y
(19) (Y ) OSO2CF3, BF4, I) which can be isolated as deep
violet crystals. Compound 19 exhibit IR and NMR
spectral properties which are quite comparable with
those of the monosubstituted Re(I) vinylidenes 3-7.
Syn th esis a n d Ch a r a cter iza tion of th e Eth oxy-
ca r b en e Com p lexes [(t r ip h os)R e(CO)2{C(OE t )-
CH2R}]BP h 4 (R ) H, 8; R ) COOEt, 20). In keeping
with the well-known proclivity of vinylidene complexes
to undergo nucleophilic additions across the CdC double
bond,15 the less electron-rich vinylidene complexes 5 and
7 react with ethanol at room temperature to give the
ethoxycarbene complexes [(triphos)Re(CO)2{C(OEt)-
CH2R}]BPh4 (R ) H, 8; R ) COOEt, 20) (Scheme 4).
Consistent with previous reports,22b the less activated
vinylidene complexes, 3, 4, and 6, do not react with
either methanol or ethanol even under drastic reaction
conditions.
As for the mechanism of the thermal degradation of
11 to the tricarbonyl complex 12 and methane, we can
safely exclude an intramolecular rearrangement of the
hydroxycarbene ligand to acetaldehyde,31a,f,48 followed
by decarbonylation of the latter ligand.43,49 In fact, the
[(triphos)Re(CO)2]+ fragment binds acetaldehyde to form
a mixture of both η1-O-CH3CHO and η2-C,O-CH3CHO
complexes,50 which do not degrade to the tricarbonyl
complex 12 and methane upon thermolysis in THF.
Following the thermolysis of 11 in THF-d8 by variable-
temperature NMR spectroscopy in a sealed tube, we had
no evidence of intermediate species prior to formation
of the tricarbonyl complex. Accordingly, no reliable
mechanism can be forwarded for the thermal conversion
of 11 to 12 and methane. Like the above mentioned
Ru-PNP vinylidene complex reaction,40 also the trans-
formation of 11 into 12 might proceed via the interme-
diacy of an Re η2-triphos acyl species which would
degrade to the tricarbonyl complex and methane by CO
deinsertion, followed by protonolysis of the Re-CH3
bond. However, no experimental evidence of an arm-
off mechanism was provided by a variable-temperature
NMR study of the acetyl complex 13 in THF. Arm-off
mechanisms have frequently been observed or proposed
for metal triphos complexes, particularly in CO and
alkyl insertion/deinsertion reactions.51 Examples of Re
η2-triphos complexes have also been described.3 In the
absence of experimental evidence, however, this remains
only speculation and we cannot exclude the occurrence
of different types of either intramolecular or intermo-
lecular mechanisms.
Syn th esis a n d Ch a r a cter iza tion of th e Alk yn yl
Com p lexes (tr ip h os)Re(CO)2(CtCR) (R ) P h (14),
(46) (a) Bruce, M. I.; Swincer, A. G. Aust. J . Chem. 1980, 33, 1471.
(b) Abu Salah, O. M.; Bruce, M. I. J . Chem. Soc., Dalton Trans. 1974,
2302. (c) Sullivan, B. P.; Smythe, R. S.; Kober, E. M.; Meyer, T. J . J .
Am. Chem. Soc. 1982, 104, 4701. (d) Mountassir, C.; Ben Hadda, T.;
Le Bozec, H. J . Organomet. Chem. 1990, 388, C13. (e) Knaup, W.;
Werner, H. J . Organomet. Chem. 1991, 411, 471. (f) Bruce, M. I. Pure
Appl. Chem. 1986, 58, 553.
(47) Hill, A. F. In Comprehensive Organometallic Chemistry II; Abel,
E. W., Stone, F. G. A., Wilkinson, G., Eds.; Pergamon Press: Oxford,
U.K., 1995; Vol. 7, Chapter 6, p 351.
(48) Fischer, E. O.; Maasbo¨l, A. Chem. Ber. 1967, 100, 2445.
(49) See for example: Wang, K.; Emge, T. J .; Goldman, A. S.; Li,
C.; Nolan, S. P. Organometallics 1995, 14, 4929 and references therein.
(50) Unpublished results from these laboratories. The literature of
η1- and η2-aldehyde complexes is voluminous. Some represantative
papers are as follows: (a) Caldarelli, J . L.; Wagner, L. E.; White, P.
S.; Templeton, J . L. J . Am. Chem. Soc. 1994, 116, 2878. (b) Wang, Y.;
Agbossou, F.; Dalton, D. M.; Liu, Y.; Arif, A. M.; Gladysz, J . A.
Organometallics 1993, 12, 2699 and references therein. (c) Huang, Y.
H.; Gladysz, J . A. J . Chem. Educ. 1988, 65, 298 and references therein.
(51) Arm-off mechanisms are well documented in transition-metal
polyphosphine chemistry. See, for example: (a) Bianchini, C.; Masi,
D.; Meli, A.; Peruzzini, M.; Zanobini, F. J . Am. Chem. Soc. 1988, 110,
6411. (b) Bianchini, C.; Meli, A.; Peruzzini, M.; Frediani, P.; Bohanna,
C.; Esteruelas, M. A.; Oro, L. A. Organometallics 1992, 11, 138. (c)
Thaler, E. G.; Folting, K.; Caulton, K. G. J . Am. Chem. Soc. 1990, 112,
2664. (d) Thaler, E. G.; Caulton, K. G. Organometallics 1990, 9, 1871.
(e) Kiss, G.; Horva´th, I. T. Organometallics 1991, 10, 3798.
The IR spectra of the ethoxycarbene complexes exhibit
νCOC bands at ca. 1260-1290 cm-1
. The NMR data
(52) Manna, J .; J ohn, K. D.; Hopkins, M. D. Adv. Organomet. Chem.
1995, 38, 79.

3816 Organometallics, Vol. 15, No. 18, 1996
Bianchini et al.
Sch em e 4
unequivocally point to the presence of an ethoxycarbene
ligand. In particular, the 31P{1H} NMR spectra display
the typical AM2 patterns which are temperature invari-
ant down to -90 °C consistent with a rapid rotation of
the carbene moiety arbout the Re-C bond. In the 13C-
{1H} NMR spectra, the carbene carbon atoms appear
as a doublet of triplets in the expected down-field region
of the spectrum (ca. 300 ppm).22b,36,39l
Since the preparation of alkoxycarbene complexes
from vinylidene precursors and alcohols has been known
for many years,15,53 it is thus surprising that none of
the relatively few Re alkoxycarbene complexes so far
reported has been synthesized through the direct ad-
dition of alcohols to vinylidene complexes. Alkylation
of neutral metal acyls has been used by Fischer,54
Gladysz,36 and Gibson,39l while Geoffroy has reported
that Re alkoxycarbene complexes can be prepared by
reaction of cationic rhenium carbyne derivatives with
epoxides.55
The molecular structure of the ethoxycarbene complex
8-BPh4‚0.5CH2Cl2 has been determined by an X-ray
diffraction analysis. The crystal structure consists of
[(triphos)Re(CO)2{C(OEt)CH3}]+ cations, tetraphenylbo-
rate anions, and interspersed dichloromethane solvent
molecules in a ratio of 1:1:0.5. An ORTEP drawing of
the complex cation is shown in Figure 3, while a list of
selected bond distances and angles is presented in Table
3.
Like the vinylidene derivative 3-BF4 (vide supra), the
coordination geometry around the rhenium atom can
be described as a slightly distorted octahedron with
comparable distortions with respect to the idealized
geometry. A salient structural feature is the length of
the Re-P3 bond opposite to the carbene ligand [2.482-
(2) Å], which is practically identical with the other two
Re-P separations [2.478(2) Å] but is significatively
shorter than the analogous distance in 3-BF4 [2.523(2)
Å]. We assign this finding to the higher electron-
withdrawing character of the vinylidene ligand as
compared to the alcoxycarbene group. In keeping with
Figu r e 3. ORTEP drawing of the complex cation [(triphos)-
Re(CO)2{C(OEt)(CH3)}]+ in 8-BPh4‚0.5CH2Cl2. Only the
ipso carbon of the phenyl rings of the triphos ligand are
shown for the sake of clarity.
this hypothesis, we notice also a significative RedC bond
elongation [2.071(8) Å] vs [1.925(6) Å] in 3-BF4 as well
as shorter Re-CO distances [d(Re-CO)av is 1.898(9) Å in
8-BPh4 and 1.946(7) Å in 3-BF4]. On the other hand,
also the trend of νCtO observed in the IR spectra of the
vinylidene and alkylidene complexes points to a higher
π-acceptor character of the vinylidene ligand (see Table
1). The other metrical parameters exhibited by the
carbene complex 8-BPh4 are in good agreement with
those reported for authenticated rhenium ethoxycarbene
complexes and do not deserve additional comments.54,56
Con clu sion s
A family of stable Re(I) vinylidene complexes has been
prepared by tautomerism of ethyne and various 1-alkynes
at the unsaturated metal center in [(triphos)Re(CO)2]+.
All the vinylidene complexes exhibit a rich reactivity
toward nucleophiles. In particular, they are excellent
precursors to either other types of Re-C multiple bond
compounds, such as disubstituted vinylidene, secondary
hydroxycarbene, and alkoxycarbene complexes, or Re-C
single bond compounds, such as σ-alkynyl and σ-acyl
complexes. For the first time, experimental evidence
has been provided of the key role of hydroxycarbene
species in the metal-assisted hydration of alkynes
leading to C-C bond cleavage.40,46,47
Ack n ow led gm en t. Thanks are due to Mr. Dante
Masi for technical assistance in the X-ray structure
determinations. Thanks are also expressed to the EC
for financial support (Contract No. ERBCHRXCT930147).
(53) Bruce, M. I.; Swincer, A. G.; Wallis, R. C. J . Organomet. Chem.
1979, 171, C5.
(54) Filippou, A. C.; Fischer, E. O.; Mu¨ller, G.; Alt, H. G. J .
Organomet. Chem. 1987, 329, 223.
(55) Mercando, L. A.; Handwerker, B. M.; MacMillan, H. J .; Geoffroy,
G. L.; Rheingold, A. L.; Owens-Waltermire, B. E. Organometallics 1993,
12, 1559.
(56) (a) Chen, J .; Yu, Y.; Liu, K.; Wu, G.; Zheng, P. Organometallics
1993, 12, 1213. (b) Alvarez-Toledano, C.; Parlier, A.; Rudler, H.; Rudler,
M.; Daran, J . C.; Knobler, C.; J eannin, Y. J . Organomet. Chem. 1987,
328, 357.
Su p p or tin g In for m a tion Ava ila ble: Tables of final
positional parameters and isotropic and anisotropic displace-
ment parameters for all atoms and bond lengths and angles
for 3-BF4 and 8-BPh4‚0.5CH2Cl2 (18 pages). Ordering infor-
mation is given on any current masthead page.
OM9602264