Backward synthesis of rhenium(I) γ3-hydroxyvinylidene and γ-methoxyvinylidene complexes and their conversion to the allenylidene[Re{C=C=CPh2}(CO)2(MeC(CH2PPh 2)3)](OSO2CF3)

Article abstract of DOI:10.1039/b103293n

The reactivity of the rhenium(I) allenylidene complex [Re{C=C=CPh₂}(CO)₂(triphos)](OTf) (1) [triphos = MeC(CH₂PPh₂)₃] towards ionic nucleophiles and electrophiles has been explored. Nucleophiles regio

Full text of DOI:10.1039/b103293n

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Backward synthesis of rhenium(I) ꢀ-hydroxyvinylidene and
ꢀ-methoxyvinylidene complexes and their conversion to the
allenylidene [Re{C᎐C᎐CPh }(CO) (MeC(CH PPh ) )](OSO CF )
᎐ ᎐
2
2
2
2 3
2
3
Nicoletta Mantovani,a Lorenza Marvelli,a Roberto Rossi,*a Claudio Bianchini,*b
Isaac de los Rios,b Antonio Romerosac and Maurizio Peruzzini*b
a Laboratorio di Chimica Nucleare ed Inorganica, Dipartimento di Chimica,
Università di Ferrara, Via L. Borsari 46, 44100 Ferrara, Italy. E-mail: mg2@dns.unife.it
b Istituto per lo Studio della Stereochimica ed Energetica dei Composti di Coordinazione, CNR,
Via J. Nardi 39, Firenze, Italy. E-mail: bianchin@fi.cnr.it; peruz@fi.cnr.it
c Área de Química Inorgánica, Facultad de Ciencias, Universidad de Almería, Almería, Spain
Received 12th April 2001, Accepted 5th June 2001
First published as an Advance Article on the web 30th July 2001
The reactivity of the rhenium() allenylidene complex [Re{C᎐C᎐CPh }(CO) (triphos)](OTf ) (1) [triphos =
᎐ ᎐
2
2
MeC(CH2PPh2)3] towards ionic nucleophiles and electrophiles has been explored. Nucleophiles regioselectively attack
the Cγ carbon atom leading to the formation of σ-alkynyl complexes, while electrophiles attack the Cβ atom yielding
carbyne complexes. The sequential addition of OHϪ and Hϩ to 1 at low temperature gave the γ-hydroxyvinylidene
complex [Re{C᎐C(H)C(OH)Ph }(CO) (triphos)](OTf ) which regenerated 1 above Ϫ40 ЊC via H O elimination.
᎐
2
2
2
ligands, the metal center in the [Re(CO)2(triphos)]ϩ fragment is
not particularly electron-rich and therefore one would expect
nucleophilic attack at the Cα atom by the oxygen atom
from water or alcohol followed by proton transfer to Cβ
as occurs in analogous reactions involving isoelectronic
ruthenium() allenylidene complexes.7,8 The addition of ROH
across the Cβ–Cγ bond of 1 is thermodynamically disfavored as
it would result in the plain transformation of the allenylidene
Introduction
The presence of as many as three reactive carbon atoms in
the allenylidene group constitutes the main reason for the
considerable attention that is presently paid to transition metal
complexes containing this poly-unsaturated ligand.1 Indeed,
in the allenylidene ligand, which exhibits both σ-donor and
π-acceptor properties, the Cα and Cγ carbon atoms are electro-
philic in nature, while the Cβ atom behaves as a nucleophilic
center. Moreover, the regioselectivity of nucleophilic addition is
strongly dependent on both the supporting metal fragment and
the Cγ substituents.1 This wealth of diverse and spatially close
reactivity centers, in addition to the intrinsic reactivity of the
metal center itself, makes the chemistry of allenylidene com-
plexes a topic of much current interest in both organometallic
synthesis2 and homogeneous catalysis.3
group into the γ-hydroxyvinylidene Re᎐C᎐C(H)C(OH)Ph
᎐ ᎐
2
which is in fact a precursor to 1 (vide infra).1,5 The fact that
no reaction takes place between 1 and water or alcohols
reflects electronic7,8 and steric9 effects. Indeed, α,β-unsaturated
hydroxy- and alkoxy-carbenes are inherently unstable and very
few examples of such compounds have been isolated.10–16
Accordingly, the apparent stability of 1 in the presence of
water and alcohols might be determined predominantly by
electronic factors, which is consistent with our observation
that both thiols and amines smoothly react with 1 to give
isolable α,β-unsaturated thio- and amino-carbene derivatives.17
On the other hand, the six phenyl substituents at the phos-
phorus atoms provide remarkable steric congestion at Cα
and therefore one cannot rule out a steric contribution to the
stability of 1. As a matter of fact, metal allenylidene complexes
bearing from three to four diphenylphosphino groups do not
similarly react with water or alcohols (e.g. [RuCl(dppm)2-
As a part of our ongoing investigation of the chemistry of
cumulene ligands stabilized by the Re() fragment [Re(CO)2-
(triphos)]ϩ (triphos = MeC(CH2PPh2)3),4 we have recently
synthesized and characterized the allenylidene derivative
[Re{C᎐C᎐Ph }(CO) (triphos)](OTf )5 (1), which represents a
᎐ ᎐
2
2
rare example of rhenium allenylidene obtained by activation of
a propargyl alcohol (OTf = ϪOSO2CF3).6
In this paper, we report a study of the reactivity of 1 towards
various nucleophiles and electrophiles. We have found,
inter alia, that the backward allenylidene to γ-hydroxyvinyl-
idene conversion at the [Re(CO)2(triphos)]ϩ fragment can be
achieved in a stepwise manner involving nucleophilic addition
of OHϪ to the allenylidene Cγ atom, followed by electrophilic
attack by Hϩ at the Cβ atom of the σ-alkynyl product.
{C᎐C᎐CPh }]ϩ
(dppm = bis(diphenylphosphinomethane)),18
᎐ ᎐
2
[(NP )RuCl{C᎐C᎐CPh }]ϩ (NP3 = N(CH2CH2PPh2)3),19 or
᎐ ᎐
3
2
[MCl (PPh ) {C᎐ C᎐CPh }] (M = Ru, Os),20 while complexes
᎐
᎐
2
3
2
2
containing two or less diphenylphosphino groups, such as
[(PNP)RuCl {C᎐C᎐CPh }]21 (PNP = n-PrN(CH2CH2PPh2)2) or
᎐ ᎐
2
2
[Ru(CO)(η1-OCMe2)(PPri3)(Cp)], readily react with water or
alcohols yielding α,β-unsaturated hydroxy- or alkoxy-carbenes
as either final or intermediate products.
Results and discussion
In accord with previous experimental and theoretical
Synthesis and characterization of the ꢁ-alkynyl complexes
evidence,22 we have found that anionic nucleophiles regio-
᎐
[Re{C᎐CC(R)Ph }(CO) (triphos)] [R ؍ OH (2), OMe (3),
᎐
2
2
selectively attack the Cγ atom in 1 to give σ-alkynyl compounds
H (4), Me (5), CH2NO2 (6), CH2C(O)CH3 (7)]
᎐
with the formula [Re{C᎐CC(OR)Ph }(CO) (triphos)] [R = H
᎐
2
2
(2); Me (3)] (Scheme 1).4a A similar regioselectivity in nucleo-
philic addition to Cγ has been observed upon reactions of 1
with either LiHBEt3 or various sources of carbon nucleophiles
Unlike several isoelectronic metal allenylidenes, 1 does not react
with neutral molecules containing O–H bonds such as water7
or alcohols.7,8 Due to the presence of two terminal carbonyl
DOI: 10.1039/b103293n
J. Chem. Soc., Dalton Trans., 2001, 2353–2361
This journal is © The Royal Society of Chemistry 2001
2353

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Scheme 1
such as CH3Li, NO2CH2Na and CH3C(O)CH2Na. In all cases,
[Re{C᎐C(H)CCH Ph }(CO) (triphos)](OTf ) (9) (Scheme 2).
᎐
3 2 2
γ-functionalized σ-alkynyl products with the general formula
Unambiguous evidence for the presence of vinylidene ligands in
᎐
[Re{C᎐CC(R)Ph }(CO) (triphos)] were obtained [R = H (4);
8 and 9 was provided by NMR spectroscopy that showed the
᎐
2
2
1
CH3 (5), CH2NO2 (6), CH2C(O)CH3 (7)] (Scheme 1).
typical H NMR resonances at ca. δ 3.5 for the vinylidene
It is worth noticing that no trace of the isomeric η1-allenyl
proton as well as 13C NMR absorptions at ca. δ 345 (dt) and
ca. δ 120 (d) for the Cα and Cβ vinylidene atoms, respectively.25
The 31P NMR spectra appear as first-order AM2 spin systems
with chemical shifts and coupling constants in line with those
reported for other Re() vinylidene complexes containing
phosphine ligands.4a,6 Due to the greater π-acceptor ability of
the vinylidene ligand as compared to the alkynyl one,25 the
resonance of the trans phosphorus donor (triplet) is signifi-
cantly shifted downfield in 8 and 9 in comparison with 4 and 5
(δ ca. Ϫ5 vs. δ ca. Ϫ19).
derivatives [Re{C(OR)᎐C᎐CPh }(CO) (triphos)], which might
᎐ ᎐
2
2
form by either direct nucleophilic attack at the allenylidene Cα
atom or tautomerization of the γ-functionalized σ-alkynyl
complex,1 was observed even for prolonged reaction times. The
stability of the allenylidene Cα atom towards anionic nucleo-
philes reflects particular steric and electronic properties of 1 as
η1-allenyl ligands can be synthesized by nucleophilic addition
to the allenylidene Cα atom.2i
Complexes 2–7 are air-stable crystalline solids with good
solubility in benzene, THF, acetone and halogenated hydro-
carbons. Their unambiguous characterization was achieved by
means of elemental analysis and conventional spectroscopic
techniques (IR and multinuclear [1H, 31P{1H}, 13C{1H}] NMR)
(Table 1).
The protonation of 6 gave the vinylidene [Re{C᎐C(H)-
᎐
CCH2NO2Ph2}(CO)2(triphos)](OTf ) (12), while 7 was con-
verted to a complex mixture of products that denied first-order
analysis and therefore the reaction was not investigated further.
Under similar conditions, the alkylation of 4 and 5 with
In keeping with the presence of a σ-alkynyl ligand, the IR
spectra of 2–7 exhibit strong and sharp νC᎐C absorptions between
MeOSO2CF3 gave the tertiary vinylidenes [Re{C᎐C(Me)-
᎐
CHPh2}(CO)2(triphos)](OTf )
(10)
and
[Re{C᎐C(Me)-
᎐
2097 and 2083 cmϪ1. The νC᎐O stretching᎐frequencies of the two
CCH3Ph2}(CO)2 (triphos)](OTf ) (11) with NMR properties in
line with those of the secondary vinylidenes 8 and 9 except for
the NMR signals due to the methyl substituent at Cβ (Table 1).
Unlike 4 and 5, the reactions of the γ-hydroxy- and
γ-methoxy-alkynyls 2 and 3 with protic acids at room tempera-
ture did not produce the expected vinylidenes, instead they
regenerated the parent allenylidene 1 via elimination of water
and methanol, respectively (Scheme 2). To our surprise, the
reactions of 2 and 3 with MeOTf at room temperature also gave
1 together with stoichiometric amounts of MeOH and OMe2,
respectively.
᎐
᎐
ancillary carbonyl ligands are shifted to lower energy (1952–
1880 cmϪ1) as compared with the parent metallacumulene 1
(2000, 1921 cmϪ1), which reflects the neutral character of 2–7.4a
The 31P{1H} NMR spectra consist of first-order AM2 patterns
with chemical shifts and coupling constants similar to those
reported for σ-alkynyl rhenium() complexes with the triphos
ligand.4 The 13C{1H} NMR spectra exhibit AXXЈY patterns for
the two magnetically inequivalent CO ligands,4,5,23 while doub-
lets of triplets and triplets are features of the alkynyl Cα and Cβ
atoms, respectively.4a,24 The presence of the CH2C(O)CH3 func-
tional group attached to the terminal Cγ atom in 7 is shown by
characteristic IR (νC᎐O 1706 cmϪ1), 13C{1H} NMR (δC᎐O 209.8,
Low-temperature protonation and alkylation of the rhenium ꢁ-
alkynyls
᎐
᎐
δCH 58.3, δCH 28.5) and 1H NMR (δCH 2.39, δCH 1.05) signals.
Similarly, the3 functionalized alkynyl in2 6 can be 3recognized by
the NMR resonances of the nitromethyl substituent [1H
(δCH NO 5.20) and 13C{1H} (δCH NO 85.1)].
2
Intrigued by the formation of MeOH and Me2O upon methyl-
ation of 2 and 3, respectively, we decided to carry out a
variable-temperature NMR study of these electrophilic
additions.
The reaction of five equivalents of either triflic or tetrafluoro-
boric acid with a CD2Cl2 solution of 2 at Ϫ78 ЊC gave a dark
violet solution containing the new γ-hydroxyvinylidene com-
2
2
2
2
Protonation and alkylation of the rhenium ꢁ-alkynyls
Consistent with the chemistry of σ-alkynyl metal complexes,25
4 and 5 readily reacted with 1 equivalent of HOSO2CF3 in
dichloromethane yielding the corresponding vinylidene deriv-
plex [Re{C᎐C(H)C(OH)Ph }(CO) (triphos)](OTf ) (13) along
᎐
2
2
atives [Re{C᎐C(H)CHPh }(CO) (triphos)](OTf ) (8) and
with variable amounts of 1 (10–20%) (selected 31P and 1H NMR
᎐
2
2
2354
J. Chem. Soc., Dalton Trans., 2001, 2353–2361

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Table 1 1H, 13C{1H} and 31P{1H} NMR spectral data (δ in ppm, J in Hz) and IR absorptions (KBr, ν in cmϪ1) for the complexes
Complex 1H
13C{1H}
31P{1H}
IR
1b
1.68 (br s, 3H, CH3 triphos
)
290.7 (m, Re᎐C᎐C᎐C)
δA Ϫ17.82
δB = δBЈ Ϫ17.63 JBBЈ Ϫ25.0
JAB = JABЈ 24.4 ν(CO)sym 2000
ν(CO)antisym ϩ
ν(C᎐C᎐C) 1921
᎐
᎐ ᎐
2.62 (m, 6H, CH2 triphos
)
208.1 (m, Re᎐C᎐C᎐C)
᎐
᎐ ᎐
192.3 (m, CO)
᎐
᎐
163.3 (s, Re᎐C᎐C᎐C)
40.0 (q, JCP 10.0, CH3 triphos
ν(OTf ) 1273
᎐
᎐ ᎐
)
39.8 (q, JCP 3.3, CH3-C triphos
)
34.3 (m, CH2-Pax triphos
33.5 (m, CH2-Peq triphos
198.0 (m, CO)
)
)
2b
1.40 (br s, 3H, CH3 triphos
2.20–2.50 (br m, 6H, CH2 triphos
)
δA Ϫ5.67
δM Ϫ18.12
JAM 17.7
ν(C᎐C) 2090
᎐
᎐
᎐
)
115.7 (d, JCP trans 13.3, Re-C᎐C)
ν(CO) 1946, 1880
᎐
2.75 (br s, 1H, OH)
100.4 (dt, JCP trans 33.0, JCP cis 12.5,
᎐
Re-C᎐C)
᎐
53.5 (s, CPh2OH)
40.4 (q, JCP 10.2, CH3 triphos
)
39.8 (q, JCP 5.4, CH3-Ctriphos
35.8 (d, JCPax 22.5, CH2-Pax triphos
)
)
33.9 (td, JCPeq 14.0, JCpax 4.0,
CH2-Peq triphos
198.3 (m, CO)
111.8 (d, JCP trans 13.3, Re-C᎐C)
)
3b
1.44 (q, JHP 2.4, 3H, CH3 triphos
2.41 (d, JHP 8.4, 2H, CH2-Pax triphos
2.25–2.75 (br m, 4H, CH2 Peq triphos
3.39 (s, 3H, OCH3)
)
δA Ϫ5.49
δM Ϫ18.42
JAM 18.2
ν(C᎐C) 2083
᎐
᎐
᎐
)
)
ν(CO) 1946, 1890
᎐
100.7 (dt, JCP trans 28.9, JCP cis 13.3,
᎐
Re-C᎐C)
᎐
51.6 (s, OCH3)
40.1 (q, JCP 9.8, CH3 triphos
)
39.7 (q, JCP 4.1, CH3-Ctriphos
35.8 (s, CPh2OCH3)
35.4 (d, JCPax 22.5, CH2-Pax triphos
)
)
33.8 (td, JCPeq 14.9, JCpax 5.8,
CH2-Peq triphos
198.5 (br m, CO)
115.7 (d, JCPtrans 12.1, C᎐C)
)
4b
1.41 (q, JHP 1.87, 3H, CH3 triphos
2.10–2.70 (br m, 7H, CH2 triphos ϩ
CHPh2)
)
δA Ϫ4.98
δM Ϫ18.89
JAM 17.3
ν(C᎐C) 2097
᎐
᎐
᎐
ν(CO) 1944, 1885
᎐
᎐
90.9 (dt, JCPtrans 32.2, JCPcis 14.3, C᎐C)
᎐
68.0 (s, CHPh2)
40.1 (q, JCP 10.1, CH3 triphos
)
39.7 (q, JCP 5.0, CH3-Ctriphos
35.7 (d, JCPax 22.7, CH2-Pax triphos
)
)
33.8 (td, JCPeq 15.1, JCPax 5.5,
CH2-Peq triphos
198.3 (m, CO)
117.8 (d, JCP trans 12.1, Re-C᎐C)
)
5b
1.42 (q, JHP 2.5, 3H, CH3 triphos
2.40 (d, JHP 8.4, 2H, CH2-Pax triphos
)
δA Ϫ5.07
δM Ϫ19.50
JAM 17.0
ν(C᎐C) 2086
᎐
᎐
᎐
)
ν(CO) 1942, 1889
᎐
2.20–2.80 (br m, 7H, CH2 Peq triphos ϩ
CH3)
90.3 (dt, JCP trans 31.8, JCP cis 14.3,
᎐
Re-C᎐C)
᎐
47.2 (s, CPh2CH3)
40.1 (q, JCP 9.8, CH3 triphos
39.7 (q, JCP 4.4, CH3-Ctriphos
)
)
37.7 (d, JCPax 22.9, CH2-Pax triphos
)
33.7 ( td, JCPeq 14.3, JCPax 5.5,
CH2-Peq triphos
)
31.5 (s, CH3)
198.0 (m, CO)
111.2 (d, JCPtrans 13.7, Re-C᎐C)
6a,e
1.38 (br s, 3H, CH3 triphos
2.00–3.30 (br m, 6H,CH2 triphos
)
δA Ϫ5.77
δM Ϫ18.31
JAM 17.3
ν(C᎐C) 2085
᎐
᎐
᎐
)
ν(CO)1946, 1888
᎐
5.20 (s, 2H, CH2NO2)
98.8 (dt, JCPtrans 33.2, JCPcis 13.3,
᎐
Re-C᎐C)
᎐
85.1 (s, CH2NO2)
52.4 (s, CPh2CH2NO2)
41.1 (q, JCP 10.2, CH3 triphos
40.2 (q, JCP 4.6, CH3-Ctriphos
)
)
36.1 (d, JCPax 21.4, CH2-Pax triphos
)
34.4 (m, CH2-Peq triphos
209.8 (s, C(5)O)
198.0 (br m, CO)
115.3 (d, JCPtrans 13.0, Re-C᎐C(2)
)
7a,e
1.05 (s, 3H, CH3 (C6)
1.38 (br s, 3H, CH3 triphos
2.00–2.50 (br m, 6H, CH2 triphos
2.39 (s, 2H, CH2 (C4)
)
δA Ϫ4.00
δM Ϫ16.58
JAM 17.5
ν(C᎐C) 2085
᎐
᎐
)
ν(CO)1952, 1880
᎐
)
)
ν(C᎐O)1706
᎐
᎐
)
94.2 (dt, JCPtrans 33.0, JCPcis 12.0,
᎐
Re-C(1)᎐᎐(C)
58.3 (s, C(4)H2)
51.0 (s, C(3)Ph2CH2COCH3)
40.5 (q, JCP 10.6, CH3 triphos
39.7 (q, JCP 4.7, CH3-Ctriphos
)
)
35.6 (d, JCPax 21.2, CH2-Pax triphos
)
34.1 (td, JCPeq 14.0, JCPax 4.0,
CH2-Peq triphos
)
28.5 (s, C(6)H3)
J. Chem. Soc., Dalton Trans., 2001, 2353–2361
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Table 1 (Contd.)
Complex 1H
13C{1H}
31P{1H}
IR
ν(CO) 2008, 1946
8b
1.7 (q, JHP 2.6, 3H, CH3 triphos
)
343.1 (dt, JCPtrans 32.3, JCPcis 10.4,
δA Ϫ20.34
δM Ϫ18.20
JAM 25.4
Re᎐C᎐C)
᎐
᎐
2.30–2.80 (br m, 7H, CH2 triphos ϩ
CHPh2)
192.0 (td, JCPtrans 8.5, JCPcis 20.7, CO)
ν(C᎐C) 1660
᎐
3.42 (dm, JHP 4.1, 1H, Re᎐C᎐CH)
191.3 (dt, JCPtrans 7.9, JCPcis 20.8, CO)
ν(OTf ) 1260
᎐
᎐
119.3 (d, JCPtrans 12.8, Re᎐C᎐C)
᎐
᎐
68.8 (s, CHPh2)
39.9 (q, JCP 9.1, CH3 triphos
39.7 (q, JCP 3.1, CH3-Ctriphos
32.0–34.5 (br m, CH2 triphos
344.9 (dt, JCPtrans 32.5, JCPcis 10.5,
Re᎐C᎐C)
)
)
)
9b
1.74 (br s, 3H, CH3 triphos
)
δA Ϫ18.36
δM Ϫ15.84
JAM 23.7.7
ν(CO) 2013, 1950
᎐
᎐
2.40–3.00 (br m, 9H, CH2 triphos ϩ CH3)
3.64 (br s, Re᎐C᎐CH)
191.4 (m, CO)
122.2 (d, JCPtrans 12.2, Re᎐C᎐C)
ν(C᎐C) 1649
᎐
ν(OTf ) 1269
᎐
᎐
᎐ ᎐
46.7 (s, CPh2CH3)
40.1 (m, CH3 triphos
39.3 (q, JCP 3.7, CH3-Ctriphos
)
)
32.6 (m, CH2 triphos
)
30.4 (s, CH3)
10b
1.40 (br s, 3H, CH3 triphos
)
340.6 (dt, JCPtrans 32.5, JCPcis 13.3,
Re᎐C᎐C)
δA Ϫ18.74
δM Ϫ15.28
JAM 24.4
ν(CO) 2005, 1944
᎐
᎐
2.20–2.50 (br m, 7H, CH2 triphos ϩ CHPh2) 190.9 (m, CO)
2.81 (s, 3H, Re᎐C᎐CCH3) 115.6 (d, JCPtrans 13.3, Re᎐C᎐C)
ν(C᎐C) 1655
᎐
ν(OTf ) 1268
᎐
᎐
᎐ ᎐
60.7 (s, CHPh2)
43.2 (s, Re᎐C᎐CCH3)
39.7 (q, JCP 9.7, CH3 triphos
᎐
᎐
)
39.5 (q, JCP 4.0, CH3-Ctriphos
37.8 (d, JCPax 29.4, CH2-Pax triphos
)
)
32.7 (td, JCPeq 15.7, JCPax 5.0,
CH2-Peq triphos
345.5 (dt, JCPtrans 32.4, JCPcis 11.0,
Re᎐C᎐C)
)
11b
1.41 (q, JHP 2.5, 3H, CH3 triphos
)
δA Ϫ19.50
δM Ϫ16.97
JAM 25.1
ν(CO) 2009, 1951
᎐
᎐
2.30 (s,, 3H, Re᎐C᎐C(Me)CCH3Ph2)
192.5 (m, CO)
122.1 (s, Re᎐C᎐C)
ν(C᎐C) 1646
᎐
᎐
᎐
2.50–2.95 (br m, 6H, CH2 triphos
)
ν(OTf ) 1267
᎐
᎐
3.45 (s, 3H, Re᎐C᎐CCH3)
61.7 (s, Re᎐C᎐C(CH3) CCH3Ph2)
᎐
᎐
᎐ ᎐
47.8 (s, Re᎐C᎐C᎐CPh2CH3)
᎐
᎐ ᎐
40.5 (m, CH3 triphos ϩ CH3-Ctriphos
33.7 (m, CH2 triphos
)
)
33.1 (s, CCCH3Ph2)
338.0 (dt, JCPtrans 32.7 JCPcis 10.2,
12a
1.80 (br s, 3H, CH3 triphos
)
δA Ϫ21.09
δM Ϫ17.86
JAM 25.6
ν(CO) 2018, 1952
Re᎐C᎐C)
᎐
᎐
2.10–2.90 (br m, 6H, CH2 triphos
)
)
191.0 (br m, CO)
116.7 (d, JCPtrans 12.1, Re᎐C᎐C)
ν(C᎐C) 1644
᎐
3.25 (s, 1H, Re᎐C᎐CH)
ν(OTf ) 1260
᎐
᎐
᎐ ᎐
5.23 (s, 2H, CH2NO2)
85.9 (s, CH2NO2)
49.6 (s, CPh2CH2NO2)
39.9 (br s, CH3 triphos ϩ CH3-Ctriphos
33.1 (br m, CH2 triphos
)
)
13a
1.57 (br s, 3H, CH3 triphos
)
Not recorded
δA Ϫ20.01
δM Ϫ17.36
JAM 25.3
Not recorded
2.20–2.80 (br m, 6H, CH2 triphos
3.80 (q, JHP 2.6, 1H, Re᎐C᎐CH)
᎐
᎐
d
16a
17a
18b
Not recorded
Not recorded
δA Ϫ19.39
δM Ϫ14.51
δA Ϫ20.03
δM Ϫ16.60
δA Ϫ27.84
δM Ϫ11.57
JAM 25.2
JAM 25.7
JAM 29.5
Not recorded
Not recorded
Not recorded
d
᎐
1.96 (q, JHP 3.3, 3H, CH3 triphos
2.84 (d, JHP 9.3, 2H, CH2 Pax triphos
2.58–3.01 (br m, 4H, CH2 Peq triphos
)
310.5 (d br m, JCPtrans 38, Re᎐C)
185.0 (m, CO)
᎐
)
)
144.8 (s, CH᎐CPh2)
᎐
5.72 (dt, JHPtrans 3.3, JHPcis 1.8, 1H, CH᎐
122.1 (s, CH᎐CPh2)
᎐
᎐
CPh2)
39.2 (brs, CH3 triphos
)
38.9 (q, JCP 13.8, CH3-Ctriphos
30.9 (m, CH2 triphos
311.5 (dt, JCPtrans 29, JCPcis 8, Re᎐C)
)
)
19a
1.99 (br s, 3H, CH3 triphos
2.86 (d, JHP 10.4, 2H, CH2 Pax triphos
)
δA Ϫ30.26
δM Ϫ13.91
JAM 29.3
ν(CO) 2096, 2055
᎐
᎐
)
186.0 (m, CO)
2.55–3.20 (br m, 4H, CH2 Peq triphos
3.30 (s, 3H, C(CH3)᎐᎐CPh2)
)
124.5 (s, C(CH3)᎐᎐CPh2)
118.1 (s, C(CH3)᎐᎐CPh2)
60.88 (s, C(CH3)᎐᎐CPh2)
39.6 (q, JCP 2.5, CH3 triphos
39.4 (q, JCP 6.1, CH3-Ctriphos
31.4 (td, JCPeq 17.1, JCPax 4.0,
CH2-Peq triphos
31.0 (m, CH2-Pax triphos
)
)
)
)
The NMR spectra were recorded in CD2Cl2 (unless otherwise stated) at room temperature using a Bruker AC200 or b Varian VXR300 instruments.
All 31P{1H} NMR spectra exhibit AM2 splitting pattern. Key: s, singlet; d, doublet; t, triplet; q, quartet; m, multiplet; br, broad. c Confirmed by
DEPT-135 experiment. d The 1 H NMR resonances of 16 and 17 could not be confidently assigned as both these complexes were formed in very low
concentration and their resonances were likely masked by those of the most abundant species. e Recorded in CDCl3.
2356
J. Chem. Soc., Dalton Trans., 2001, 2353–2361

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data for 13 are reported in Table 1) (Scheme 3). Increasing the
temperature to Ϫ40 ЊC completely converted the γ-hydroxy-
vinylidene 13 to 1. Repeating the same experiment at Ϫ78 ЊC
with a weaker acid such as tris(trifluoromethyl)-tert-butanol,
HOC(CF3)3, resulted in the quantitative and selective formation
of the γ-hydroxyvinylidene 13 (Fig. 1).
the latter step, an equivalent amount of water is released.4c,5,27
In a few reactions only, γ-hydroxyvinylidene compounds have
been either intercepted spectroscopically or isolated in the solid
state.10–16
The protonation of γ-hydroxyalkynyl complexes has been
previously investigated in situ.28–30 In no case, however, was the
formation of a hydroxyvinylidene species detected during the
protonation reaction so that the primary regiochemistry of Hϩ
addition to the hydroxyalkynyl moiety is still unclear, i.e. it has
not been demonstrated whether the proton attacks primarily
the terminal hydroxy substituent or the Cβ atom. For example,
The conversion of 2 to 1 via 13 is mechanistically relevant to
the metal-mediated transformation of propargylic alcohols
᎐
HC᎐CC(R)(RЈ)OH into allenylidene ligands M᎐C᎐C᎐C(R)-
᎐
᎐ ᎐ ᎐
(RЈ) and water which proceeds via a cascade mechanism
primarily proposed by Selegue (Scheme 4).26 This mechanism
involves the sequential conversion of the propargyl alcohol to
π-alkyne, γ-hydroxyvinylidene and then allenylidene ligands. In
i
᎐
the protonation of [CpOs(PPr ) (H){C᎐CC(OH)Ph }]PF (14)
᎐
3
2
2
6
has been suggested to involve the direct protonation of the OH
group exclusively on the basis of the inertness of 14 to convert
to the corresponding vinylidene.28 The unambiguous detection
of the 3-hydroxyvinylidene complex 13 during the protonation
of 2 at low temperature clearly points to the alternative path-
way in which the proton is selectively delivered to the Cβ carbon
of the hydroxyalkynyl ligand to give a vinylidene intermediate,
which rearranges to allenylidene 1 and water above Ϫ40 ЊC. The
low activation barrier of γ-hydroxyvinylidene to allenylidene
conversion explains why no trace of 13 was detected by
variable-temperature NMR spectroscopy in the course of the
᎐
reaction between HC᎐CCPh (OH) and the Re() fragment
᎐
2
[Re(CO)2(triphos)]ϩ, generated from [Re(OTf )(CO)2(triphos)]
(15).4c The activation of the propargyl alcohol by the Re()
fragment occurred at Ϫ5 ЊC, well above the temperature at
which 13 spontaneously degrades to 1 and water.
A similar scenario accounts for the reactions between 2 and
Meϩ and between 3 and Hϩ (Scheme 3) which gave 1 and
MeOH. Indeed, the intermediate hydroxyvinylidene com-
plex [Re{C᎐C(Me)C(OH)Ph }(CO) (triphos)](OTf ) (16) was
᎐
2
2
detected at low temperature, while the protonation of the
methoxyalkynyl complex 3 did not allow us to intercept any
intermediate species preceding the formation of 1 and MeOH
even at Ϫ80 ЊC. Gimeno and co-workers have similarly reported
that MeOH is liberated from the methoxyvinylidene intermedi-
᎐
Fig.
1
Reaction of [Re{C᎐CC(OH)Ph2}(CO)2(triphos)] (2) with
᎐
HOC(CF3)3 (1 : 5) in CD2Cl2: (a) 31P{1H} NMR spectrum of 2 at
Ϫ78 ЊC; (b) 31P{1H} NMR spectrum immediately after addition of
᎐
HOC(CF3)3 at Ϫ78 ЊC; (c) at Ϫ40 ЊC; (d) at Ϫ20 ЊC. A: [Re{C᎐CC(OH)-
Ph2}(CO)2(triphos)] (2). B: [Re{C᎐C(H)C(OH)Ph2}(CO)2(triphos)]-
(OTf ) (13). C: [Re{C᎐C᎐CPh2}(CO)2(triphos)](OTf ) (1).
᎐
᎐
ate [(η5-C H )Ru(PPh ) {C᎐C(H)CH(Ph)OMe}]ϩ obtained by
᎐
9
7
3 2
᎐
᎐
Scheme 2
Scheme 3
J. Chem. Soc., Dalton Trans., 2001, 2353–2361
2357

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Scheme 4
reacting [(η5-C9H7)Ru(PPh3)2Cl] with HC᎐CCH(Ph)OH/
carbon atoms appear as highly deshielded doublets of multi-
plets at δ 310.5 and 311.5.
᎐
᎐
NaPF6.10
Upon methylation with MeOTf at room temperature, the
γ-methoxyalkynyl complex 3 quantitatively converted to 1
releasing one equivalent of Me2O. When the reaction was per-
formed at low temperature, the 2-methyl-3-methoxyvinylidene
Although the two carbynes could be obtained quantitatively
in the NMR tube, all our attempts to isolate pure samples in the
solid state from their CH2Cl2 solutions were unsuccessful due to
extensive formation of the parent allenylidene 1. By adding
MeOTf to a stirred suspension of 1 in benzene, 19 immediately
precipitated as a greenish yellow solid, which proved to be
extremely moisture-sensitive and regenerated 1 rapidly even in
the solid state unless handled in a dry box. A satisfactory elem-
ental analysis and the observation in the IR v(CO) region of
two strong absorptions at high wavenumbers (2096, 2055 cmϪ1)
confirmed the carbyne nature of 19. Dissolution of the solid
product in wet CD2Cl2 gave 1 even at low temperature, which
reflects a particulary strong acidic character for the rhenium()
dicationic carbyne complex, as well as the great thermodynamic
stability of the allenylidene 1.
intermediate [Re(CO) {C᎐C(Me)C(OMe)Ph }(triphos)](OTf )
᎐
2
2
(17) was intercepted by NMR spectroscopy (31P{1H} NMR:
AM2 pattern with δA Ϫ20.03, δM Ϫ16.60, JAM = 25.7 Hz)
(Scheme 3). On increasing the temperature to ca. 20 ЊC, 17
transformed into 1 with contemporaneous formation of Me2O.
The elimination of dimethyl ether from γ-methoxyvinylidene
complexes has no precedent in the literature and confirms that
the formation of metalloallenylidenes represents the thermo-
dynamic sink of any Selegue type reaction.
Reaction of 1 with electrophiles: synthesis and characterization
of dicationic rhenium carbyne complexes
i
᎐
An osmium carbyne complex [CpOs(PPr ) {᎐CC(H)᎐
᎐
᎐
3
2
CPh2}](PF6)2 has been prepared by protonation of a parent
allenylidene. Unlike 19, the Os complex could be isolated in the
solid state and was also authenticated by X-ray crystallo-
graphy.28
In line with the chemistry of metallacumulenes,1,31,32 the Cβ
atom in 1 was selectively attacked by HOTf and MeOTf to give
᎐
the emerald-green carbyne complexes [Re(CO) {᎐CC(H)᎐
᎐
᎐
2
᎐
CPh2}(triphos)](OTf )2 (18) and [Re(CO) {᎐CC(Me)᎐CPh }-
᎐
᎐
2
2
(triphos)](OTf )2 (19), respectively (Scheme 5). A fivefold excess
Conclusion
The results presented in this paper show that the γ-hydroxy-
vinylidene [Re{C᎐C(H)C(OH)Ph }(CO) (triphos)](OTf ) is
᎐
2
2
intermediate to the allenylidene [Re{C᎐C᎐CPh }(CO) -
᎐ ᎐
2
2
(triphos)](OTf ) in the course of the reaction of the Re()
fragment [Re(CO)2(triphos)]ϩ with the propargyl alcohol
᎐
HC᎐CCPh OH. The intermediacy of the γ-hydroxyvinylidene
᎐
2
complex could not be observed by the straightforward reaction
due to the very low activation barrier for water elimination
from the latter complex.
The allenylidene complex represents a true thermodynamic
sink: it also forms quantitatively by spontaneous extrusion
of dimethyl ether from the γ-methoxyvinylidene complex
[Re(CO) {C᎐C(Me)C(OMe)Ph }(triphos)](OTf ) that involves
both C–C and C–O bond breaking.
᎐
2
2
Scheme 5
of electrophile was necessary for quantitative formation of the
carbynes.
Experimental
The 31P{1H} NMR spectra of the two Re() carbyne products
exhibit AM2 patterns with peculiar chemical shifts and coupling
constants for triphos–Re() carbenes,4a,b vinylidenes4a and
allenylidenes.4c,5 The triplet resonance due to the phosphorus
atom trans to the carbyne carbon atom is remarkably shifted to
high field [δA Ϫ27.84 (18), Ϫ30.18 (19)] as compared to the
vinylidene precursor, while the J(PP) constant is unusually large
All reactions and manipulations were routinely performed
under a dry nitrogen atmosphere by using standard Schlenk
techniques. Tetrahydrofuran (THF) was freshly distilled over
LiAlH4; acetone and benzene were distilled over P2O5;
dichloromethane and methanol were purified by distillation
over CaH2 before use; n-hexane was stored over molecular
sieves and purged with nitrogen prior to use. The complex
1
for Re() triphos complexes [J(PAPM)ave = 29.5 Hz].4,5 In the H
NMR spectrum of 18, a doublet of triplets at 5.72 ppm features
[Re{C᎐C᎐CPh }(CO) (triphos)](OTf )5 (1) was prepared as
᎐ ᎐
2
2
the ᎐CH proton, while the resonances of the two sp2 carbon
previously reported. All the other reagents and chemicals were
reagent grade and, unless otherwise stated, were used as
received from commercial suppliers. The solid complexes were
᎐
atoms of the alkenyl ligand fall at 144.8 (CH᎐) and 122.1
᎐
(᎐CPh ) ppm in the 13C{1H} NMR spectrum. The sp carbyne
᎐
2
2358
J. Chem. Soc., Dalton Trans., 2001, 2353–2361

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collected on sintered glass-frits and washed with either light
diethyl ether or n-pentane before being dried in a stream of
nitrogen unless otherwise stated. IR spectra were obtained in
KBr using a Nicolet 510P FT-IR (4000–200 cmϪ1) spectro-
photometer. Deuterated solvents for NMR measurements
(Aldrich and Merck) were dried over molecular sieves (4 Å).1H
and 13C{1H} NMR spectra were recorded on Bruker AC200,
Varian VXR300 and Bruker DRX 500 spectrometers operating
at 200.13, 299.94 and 500.13 MHz, and 50.32, 75.42 and 125.75
MHz, respectively. Peak positions are relative to tetramethyl-
silane and were calibrated against the residual solvent reson-
ance (1H) or the deuterated solvent multiplet (13C). 31P{1H}-
NMR spectra were recorded on the same instruments operating
at 81.01, 121.42 and 202.46 MHz, respectively. Chemical shifts
were measured relative to external 85% H3PO4 with downfield
values taken as positive. The computer simulation of the
second-order NMR spectra was carried out with a locally
developed package containing the programs LAOCN333 and
DAVINS.34 The initial choices of shifts and coupling constants
were refined by iterative least-squares calculations using the
experimental digitised spectrum. The final parameters gave a
satisfactory fit between experimental and calculated spectra, the
agreement factor being less than 1% in all cases. Elemental
analyses (C, H, N) were performed using a Carlo Erba model
1106 elemental analyser.
(triphos)](OTf ) (16) as minor product (ca. 10%). As the tem-
perature was increased 16 quickly transformed into 1 (the trans-
formation was complete at Ϫ40 ЊC) while at higher temperature
in the presence of a larger excess of methyl triflate the alkenyl-
᎐
carbyne [Re{᎐CC(Me)᎐CPh }(CO) (triphos)](OTf ) (19) (see
᎐
᎐
2
2
2
below) began to form. Elimination of one equivalent of MeOH
1
was shown by GC-MS analysis and confirmed by H NMR
spectroscopy (δMeOH 3.40).
᎐
[Re{C᎐CC(OMe)Ph }(CO) (triphos)] (3). A solution of 1
᎐
2
2
(200 mg, 0.17 mmol) in 10 mL of methanol was treated with a
tenfold excess of sodium methoxide (92 mg, 1.70 mmol) added
in small portions with vigorous stirring. The mixture was addi-
tionally stirred for 30 min during which time a pale yellow-
brown solid separated. The solvent was removed under reduced
pressure and the solid was washed with water, isopropylic
alcohol and n-hexane to leave a yellowish brown powder.
Yield: 78%. Anal. Calcd for C59H52O3P3Re: C, 65.12; H, 4.82.
Found: C, 65.45; H, 4.97%.
In situ NMR reaction of 3 with HBF4ؒOEt2 or HOCHx-
(CF3)3 ؊ x (x ؍ 0, 1). Addition of five equivalents of HBF4ؒOEt2
(33 µL, 0.18 mmol) to a CDCl3 solution (0.8 mL) of 3 (40 mg,
0.04 mmol) at Ϫ55 ЊC in a 5 mm screw-cap NMR tube, caused
an immediate colour change from yellow-brown to dark violet.
31P{1H} NMR spectroscopy showed the quantitative formation
of the parent allenylidene 1 as the only rhenium–triphos
species.
Replacing HBF4ؒOEt2 with either HOC(CF3)3 or HOCH-
(CF3)2 did not affect the course of the reaction and produced
1 with no detectable intermediate. The transformation was
complete at Ϫ30 ЊC in 15 min.
Preparations
᎐
[Re{C᎐CC(OH)Ph }(CO) (triphos)] (2). A solution of 1
᎐
2
2
(200 mg, 0.17 mmol) in 5 mL of CH2Cl2 was slowly added
to a solution of KOH (100 mg, 1.78 mmol) in 5 mL of
distilled water under vigorous stirring to favour the mixing of
the organic and aqueous phases. Stirring was continued for ca.
1.5 h until the starting deep purple colour of the organic phase
became reddish orange. The dichloromethane layer was
separated from the aqueous layer and dried over Na2SO4. After
filtration, the solvent was removed under reduced pressure and
the brown-orange residue was washed with H2O, isopropylic
alcohol and n-hexane. Yield 72%. Anal. Calcd for C58H50O3-
P3Re: C, 64.85; H, 4.69. Found: C, 64.57; H, 4.82%.
The formation of one equivalent of MeOH was confirmed in
each case by both GC-MS analysis and 1H NMR spectroscopy.
In situ NMR reaction of 3 with CH3OSO2CF3. A solution of
3 (40 mg, 0.04 mmol) in CD2Cl2 (0.8 mL) was prepared in a
5 mm screw-cap NMR tube and cooled to Ϫ78 ЊC with a dry
ice/acetone bath before adding five equivalents of CH3-
OSO2CF3 through the serum cap. The tube was inserted into
the NMR probe precooled at Ϫ74 ЊC and the progress of the
reaction was monitored by 31P{1H} NMR spectroscopy. At
Ϫ50 ЊC the formation of 3, 1 and the 2-methyl-3-methoxy-
In situ NMR reaction of 2 and HOSO2CF3. A solution of 2
(25 mg, 0.022 mmol) in CD2Cl2 (0.8 mL) was prepared in a 5
mm screw-cap NMR tube and cooled to Ϫ78 ЊC with a dry ice/
acetone bath before adding five equivalents of HOSO2CF3
through the serum cap. The tube was inserted into the NMR
probe precooled at Ϫ74 ЊC and the progress of the reaction was
monitored by 31P{1H} NMR spectroscopy. At this temperature,
a 1:5 mixture of the allenylidene 1 and of the hydroxyvinyl-
vinylidene
[Re(CO) {C᎐C(Me)C(OMe)Ph }(triphos)](OTf )
᎐
2 2
(17) in a 10 : 10 : 1 ratio was observed. On standing at room
temperature a complete transformation into 1 occurred in 1 h.
The formation of one equivalent of Me2O was confirmed by
GC-MS analysis and 1H NMR spectroscopy (δMe O = 3.27).
2
idene [Re{C᎐C(H)C(OH)Ph }(CO) (triphos)](OTf ) (13) was
observed. At higher temperature, 13 converted into 1 and at
᎐
᎐
2
2
[Re{C᎐CC(H)Ph }(CO) (triphos)] (4). A tenfold excess of
᎐
2
2
LiHBEt3 (1 M THF solution, 1.7 mL, 1.7 mmol) was syringed
into a solution of 1 (200 mg, 0.17 mmol) in 10 mL of THF
cooled at Ϫ15 ЊC. The dark violet colour turned to yellow
immediately. After stirring for 30 min at 0 ЊC, the solution was
concentrated to ca. 1 mL and complex 4 was obtained as a pale
yellow powder upon slow addition of 2 mL of n-hexane. The
solid product was washed with water, cold isopropylic alcohol
and n-hexane. Yield 76%. Anal. Calcd for C58H50O2P3Re: C,
65.83; H, 4.76. Found: C, 65.94; H, 4.92%.
Ϫ40 ЊC, 1 was the only detectable product. On increasing the
᎐
temperature to ca. 0 ЊC the carbyne [Re(CO) {᎐CC(H)᎐
᎐
᎐
2
CPh2}(triphos)](OTf )2 (18) (see below) was also formed.
In situ NMR reaction of 2 and HOC(CF3)3. Ten equivalents
of HOC(CF3)3 were syringed into a solution of 2 cooled to
Ϫ78 ЊC as described above. At this temperature, the quanti-
tative formation of 13 was confirmed by 31P{1H} NMR spec-
troscopy. Heating the NMR sample to Ϫ20 ЊC quantitatively
transformed 2 into the parent allenylidene 1 while no trace of
18 was observed at any temperature.
In situ NMR reaction of 4 and HOSO2CF3. Synthesis of
[Re{C᎐C(H)CHPh }(CO) (triphos)](OTf ) (8). A stoichiometric
᎐
2
2
amount of HOSO2CF3 (6.7 µL, 0.07 mmol) was added to a
CD2Cl2 solution (0.8 mL) of 4 (80.0 mg, 0.07 mmol) in a 5 mm
screw-cap NMR tube. Immediately the colour changed from
yellow to brownish orange and the NMR spectra showed the
complete transformation of 4 into 8.
In situ NMR reaction of 2 and CH3OSO2CF3. Addition of
five equivalents of CH3OSO2CF3 to a cold solution of 2
prepared as described above, caused an immediate colour
change from brownish orange to dark violet indicating the
formation of the parent allenylidene compound. A 31P{1H}
NMR spectrum at Ϫ74 ЊC showed the presence of the
In situ NMR reaction of 8 and NEt3. A tenfold excess of NEt3
secondary hydroxyvinylidene [Re{C᎐C(Me)C(OH)Ph }(CO) -
(93 µL, 0.70 mmol) was added to a CD2Cl2 solution (0.8 mL) of
᎐
2
2
J. Chem. Soc., Dalton Trans., 2001, 2353–2361
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8 (80.0 mg, 0.07 mmol) in a 5 mm screw-cap NMR tube. 31P
NMR spectrum confirmed the quantitative transformation of 8
into 4.
stirring for 30 min, addition of 200.0 mg (0.17 mmol) of 1
under stirring caused a fast colour change from dark violet to
red-brown. The solution was additionally stirred for 2 h at room
temperature and then filtered through Celite. Removal of the
solvent under reduced pressure gave a reddish solid that was
dissolved in CH2Cl2 (3 mL). The resulting red solution was
filtered through a cotton plug and concentrated almost to dry-
ness (0.5 mL). Addition of n-pentane (2.0 mL) precipitated 7 as
a beige solid. Yield: 72%. Anal. Calcd for C61H54O3P3Re: C,
65.76; H, 4.88. Found: C, 66.10; H, 4.85%.
In situ NMR reaction of 4 and CH3OSO2CF3. Synthesis of
[Re{C᎐C(Me)CHPh }(CO) (triphos)](OTf ) (10). Addition of
᎐
2
2
one equivalent of CH3OSO2CF3 (6.2 µL, 0.07 mmol) to a
CD2Cl2 solution (0.8 mL) of 4 (80.0 mg, 0.07 mmol) in a 5 mm
screw-cap NMR tube, completely transformed 4 into 10 (31P
NMR analysis).
᎐
[Re{C᎐CC(Me)Ph }(CO) (triphos)] (5). To a solution of 1
᎐
2
2
In situ NMR reaction of 7 and HOSO2CF3. A stoichiometric
amount of HOSO2CF3 (2.4 µL, 0.03 mmol) was added to a 5
mm screw-cap NMR tube charged with 7 (30 mg, 0.03 mmol)
and CD2Cl2 (0.7 mL). A 31P NMR spectrum of the resulting red
solution showed the presence of a complicated mixture of
products which were not studied further.
(200 mg, 0.17 mmol) in 5 mL of THF was added a tenfold
excess of CH3Li (1.7 M THF, 1.0 mL, 1.70 mmol) which caused
a colour change from dark violet to dark orange. After stirring
for 3 h at room temperature, wet THF (1.0 mL) was added
dropwise to hydrolyse the excess of CH3Li. The solvent was
removed under vacuum and the pale brown residue was washed
with H2O, ethanol and n-hexane. Yield 78%. Anal. Calcd for
C59H52O2P3Re: C, 66.10; H, 4.89. Found: C, 66.37; H, 4.95%.
᎐
In situ synthesis of [Re{᎐CC(H)᎐CPh }(CO) (triphos)](OTf )
᎐
᎐
2
2
2
(18). Addition of a fivefold excess of HOSO2CF3 to a CD2Cl2
solution (0.8 mL) of 1 (40.0 mg, 0.03 mmol) in a 5 mm screw
cap NMR tube at room temperature, caused an immediate
colour change from dark purple to emerald green. NMR moni-
toring of the reaction revealed the quantitative formation of 18.
Addition of water or of other nucleophiles to a solution of
18 immediately restored the purple colour of 1.
In situ NMR reaction of 5 and HOSO2CF3. Synthesis of
[Re{C᎐C(H)C(Me)Ph }(CO) (triphos)](OTf ) (9). Addition of
of HOSO2CF3 (6.7 µL, 0.07 mmol) to a CD2Cl2 solution (0.8
mL) of 5 (80.0 mg, 0.07 mmol) in a 5 mm screw-cap NMR tube
completely transformed 5 into 9.
᎐
2
2
In situ NMR reaction of 9 and NEt3. A complete transform-
ation of 9 into 5 took place after addition of a tenfold excess of
NEt3 (25.0 µL, 0.20 mmol) to a CD2Cl2 solution (0.8 mL) of 9
(30.0 mg, 0.02 mmol) in a 5 mm screw-cap NMR tube
(confirmed by 31P NMR spectroscopy).
᎐
In situ synthesis of [Re{᎐CC(Me)᎐CPh }(CO) (triphos)]-
᎐
᎐
2
2
(OTf )2 (19). Replacing HOSO2CF3 with MeOSO2CF3 in the
above preparation, gave the carbyne [Re(CO) {᎐CC(Me)᎐
CPh2}(triphos)](OTf )2 (19) in quantitative NMR yield.
᎐
᎐
᎐
2
Synthesis of 19. In a Schlenk tube 1 (40 mg, 0.03 mmol) was
suspended in benzene (3 mL) and a fivefold excess of
MeOSO2CF3 (16 µL) was syringed under vigorous stirring.
After 15 min, the solvent was removed under reduced pressure
and the greenish residue was washed with cold benzene (2 × 1
mL) and pentane (2 × 1 mL) before being dried. Anal. Calcd.
for C61H52F6O8P3S2Re: C, 53.47; H, 3.82. Found: C, 54.02; H,
3.94%.
In situ NMR reaction of 5 and CH3OSO2CF3. Synthesis of
[Re{C᎐C(Me)C(Me)Ph }(CO) (triphos)](OTf ) (11). A stoi-
᎐
2
2
chiometric amount of CH3OSO2CF3 (8.4 µL, 0.07 mmol) was
added to a CD2Cl2 solution (0.8 mL) of 5 (80.0 mg, 0.07 mmol)
in a 5 mm screw-cap NMR tube. The immediate transformation
of 5 into 11 was shown by the colour change from yellow
to brownish orange and confirmed by 31P{1H} NMR
spectroscopy.
᎐
Acknowledgements
[Re{C᎐CC(CH NO )Ph }(CO) (triphos)] (6). 200 mg of
᎐
2
2
2
2
MeONa (3.70 mmol) was introduced under stirring in a
Schlenk tube containing 5 mL of nitromethane. After 5 min
solid 1 (200 mg, 0.17 mmol) was added in small portions and
the resulting solution was stirred for 1 h at room temperature
during which time the colour of the solution slowly turned from
deep violet to brown. Removal of the solvent in vacuo yielded 6
as a brown solid which was washed with ethanol and n-pentane.
Yield: 75%. Anal. Calcd for C59H51NO4P3Re: C, 63.43; H, 4.60;
N, 1.25. Found: C, 64.10; H, 4.69; N, 1.37%.
Thanks are due to the EC through COSTD17 Action (WGD17/
003) for supporting this research and to the RTN contract
HPRM-CT-2000-0010. Thanks are also expressed to the
MURST (Rome, Italy) for financial support. I. de los Ríos
thanks “Ministerio de Ciencia y Tecnologia” (Spain) for a post-
doctoral grant.
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᎐
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᎐
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᎐
2
3
2
2
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2360
J. Chem. Soc., Dalton Trans., 2001, 2353–2361

View Article Online
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᎐
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᎐
᎐
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i
᎐
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᎐
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J. Chem. Soc., Dalton Trans., 2001, 2353–2361
2361