Reaction pathways of 2,2,2-trifluoroethylamine and n-butylamine with [Ru(bpy)2(NO)Cl]2+

Article abstract of DOI:10.1016/S0040-4020(02)00382-4

The reaction of [Ru(bpy)₂(NO)Cl]²⁺ with 2,2,2-trifluoroethylamine produced [Ru(bpy)₂(NO)Cl]⁺ by electron transfer and a number of organic compounds formed via nucleophilic substitution of the intermediate 2,2,2-trifluoroethyldiazonium ion (free or coordinated). Density functional theory computed results suggest that stabilization of the trifluoroethyldiazonium ion by complexation is much larger than the one corresponding to the butyl ion, in agreement with the fact that no rearrangement products derived from CF₃CH₂⁺ were observed.

Full text of DOI:10.1016/S0040-4020(02)00382-4

TETRAHEDRON
Pergamon
Tetrahedron 58 (2002) 4237±4244
Reaction pathways of 2,2,2-tri¯uoroethylamine
and n-butylamine with [Ruꢀbpy) ꢀNO)Cl]
2
1
2
p
Florencia Di Salvo, Alejandro Crespo, Dar Âõ o A. Estrin and Fabio Doctorovich
Departamento de Qu Âõ mica Inorg a nica, Anal Âõ tica y Qu Âõ mica F Âõ sica/INQUIMAE, Facultad de Ciencias Exactas y Naturales,
Universidad de Buenos Aires, Ciudad Universitaria, Pabell o n II, piso 3 %1428), CEHA Buenos Aires, Argentina
Received 12 February 2002; accepted 28 March 2002
2
1
1
AbstractÐThe reaction of [Ru(bpy) (NO)Cl] with 2,2,2-tri¯uoroethylamine produced [Ru(bpy) (NO)Cl] by electron transfer and a
2
2
number of organic compounds formed via nucleophilic substitution of the intermediate 2,2,2-tri¯uoroethyldiazonium ion (free or co-
ordinated). Density functional theory computed results suggest that stabilization of the tri¯uoroethyldiazonium ion by complexation is
1
3 2
much larger than the one corresponding to the butyl ion, in agreement with the fact that no rearrangement products derived from CF CH
were observed. q 2002 Elsevier Science Ltd. All rights reserved.
1. Introduction
obtained aromatic diazonium salts stabilized by coordina-
tion to ruthenium through the reaction of [Ru(bpy)
2
2
1
We have recently studied from an experimental and theo-
retical standpoint the possibility of stabilizing diazonium
ions attached to sp carbons by coordination to ruthenium
and iron. Experimental results on reaction products as
well as density functional theory (DFT) calculations
(NO)Cl] with aniline and other aromatic amines. Similar
reactions involving aliphatic amines could provide insight
into the chemistry of the extremely reactive aliphatic diazo-
nium salts if coordination to the metal stabilizes them
enough to reduce their reaction rates to a manageable time-
scale, and if limited amounts of nucleophiles are present.
For example, the coordinated diazonium ions could be used
as direct sources of free diazonium ions by ligand displace-
ment reactions.
3
1
have shown that the butyldiazonium ion might be stabil-
ized by coordination to a [Ru(bpy) Cl] moiety (bpy is
1
2
0
2
,2 -bipyridyl). However, direct evidence of the formation
of this intermediate could not be found. Although butyl-
diazonium ion and most of the closely related diazonium
ions attached to sp carbons are extremely unstable, a few
3
In addition to the experimental study of the reaction path-
with 2,2,2-tri¯uoroethyl-
2
,3
21
were observed at low temperature. 2,2,2-Tri¯uoroethyl-
diazonium ion has been observed by NMR at 2608C, and
ways of [Ru(bpy)
2
(NO)Cl]
2
amine, we investigated the structure and stability of the
intermediate diazenido by using DFT computations and
a continuum solvation model. DFT has proved to be a
powerful and economical tool for the investigation of a
variety of molecular properties of transition metal com-
was therefore selected as a good candidate to test the
stabilizing effect of [Ru(bpy) Cl] . As will be shown
1
2
below, the electron-attracting effect of the ¯uorine
atoms stabilizes the diazonium ion and increases back-
donation from the metal center to the organic moiety. So
9
,10
pounds.
into the formalism by using continuum and/or discrete
Solvation effects can be readily incorporated
1
1
3
far there have been a few examples of sp diazonium ions
coordinated to molybdenum, tungsten, rhenium and
4
5,6
12
solvent models.
We have already employed this
7
cobalt. Our group is exploring the possibility of obtaining
approach in the investigation of IR spectroscopy, struc-
tural properties and reactivity of related Fe and Ru
complexes.
stabilized diazonium ions by diazotization of primary
amines with coordinated nitrosyl ligands. This would
provide an enormous number of possibilities since a
large number of amines are easily available.
3
,13±15
8
This route was ®rst pointed out by Meyer et al., who
2. Results and discussion
.1. Formation of products
2
Keywords: n-butylamine; density functional theory; electron transfer; 2,2,2-
tri¯uoroethylamine; nitrosyl; ruthenium; complex.
2
The products obtained by reaction of [Ru(bpy) (NO)Cl] ,
1, with 2,2,2-tri¯uoroethylamine, 2, are shown schematically
1
p
Corresponding author. Tel.: 15411-4576-3358; fax: 15411-4576-3341;
e-mail: doctorovich@q1.fcen.uba.ar
2
0040±4020/02/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(02)00 382-4

4238
F. Di Salvo et al. / Tetrahedron 58 %2002) 4237±4244
in the equation below:
amine is added. This can be explained taking into account
that part of the starting complex is consumed by the electron
transfer reaction described above (see the discussion
below).
The alcohol (6) is practically the only product when the
reaction is carried out in the presence of water (CH CN±
3
H Oˆ4:1). In the presence of a large amount of amine, (E)-
2
2,2,2-tri¯uoroethyldiazoate is observed at short reaction
times (3 h) as shown in Table 1 (last column). The large
excess of amine makes the reaction medium more basic and
favors deprotonation of the diazoic acid 9 (Scheme 1),
2
before loss of OH takes place. However, the diazoate
decomposes after a few hours, probably by a metal-
catalyzed pathway (see below).
ꢀ1†
In the case of 7, part of the chloride ligand may be replaced
by 2,2,2-tri¯uoroethylamine or CH CN. There is also
experimental evidence indicating the formation of
2.2. Proposed mechanism
3
Based on the products obtained in the reaction and in
21
3,16
[
fer (see below).
Ru(bpy) (NH CH CF )(Cl)] produced by electron trans-
3
previous results,
tion of tri¯uoroethylamine with [Ru(bpy) (NO)Cl] , 1,
the proposed mechanism for the reac-
2
2
2
2
1
2
involves two main pathways (Scheme 1). Pathway A
consists of a nucleophilic attack of the amine (2) to the
nitrosyl ligand to produce a diazoic complex, as previously
suggested. The diazoic ligand loses hydroxide to produce
the diazenido complex, which may be attacked by differ-
ent nucleophiles such as the amine itself, chloride or hy-
droxide to produce 3, 4 and 6, respectively. A mechanism
involving concerted addition of chloride ion or hydroxide
ion through a ®ve- or four-membered transition state cannot
be discarded (Eq. (2)). The vacant site might be occupied by
1
As it has been suggested, nucleophilic attack at coordinated
NO in 1 by the amine to produce intermediate 9 and subse-
quent loss of hydroxide to produce the diazenido 10 is
proposed (Scheme 1, pathway A). Products 3, 4 and 6 are
formed by nucleophilic attack to the carbocation (or the
diazonium salt) by 2,2,2-tri¯uoroethylamine, chloride ion
and hydroxide, respectively (Scheme 1). Although for the
sake of simplicity, Scheme 1 shows direct attack on the
coordinated diazonium ion, some amount of these products
could be produced by attack to the free diazonium ion.
Product 5 might be formed by nitrosation of 3 by the nitrosyl
complex. It is observed at low amine±complex ratios (1:1
and 2:1). Formation of product 8 might be explained by
electron transfer from the amide complex 11 to 1 (Scheme
1
7
2 or CH CN.
3
1
, pathway B). DFT calculations show that the electron
transfer process is thermodynamically favorable in aceto-
ꢀ2†
0
nitrile (DG ˆ218.9 kcal/mol). The amide complex could
be produced by tri¯uoroethylamine proton abstraction
from the coordinated amine. The acidity of the coordinated
amine is expected to be enhanced due to the electron with-
drawing effect of the nearby metal center. It must be noted
that the calculations showed that the electron transfer
process is thermodynamically unfavorable when the free
amine acts as the electron donor.
Regarding the decomposition of product 9, it must be noted
that free (E)-tri¯uoroethanediazoate decomposes slowly
1
7
even in protic medium and in principle, it is expected to
be stable in our reaction medium. A possibility is that the
intermediate diazoate decomposes via a metal catalyzed
pathway. It is important to note that coordination of tri-
¯uoroethanediazoate (or the corresponding diazoic acid)
through the nitrogen attached to oxygen should increase
rather than decrease the stability of the diazoate due to the
expected increase in acidity of the proton attached to the
oxygen in the R±NvN(OH) unit.
2
1
By observing the FTIR signal at 1931 cm (corresponding
to the nitrosyl ligand in the starting complex) of reaction
mixtures at 1±2 ratios varying from 1:1 to 1:15, it could be
determined that the stoichiometric ratio is 2±1 ù2.5. The
signal corresponding to NO in the starting complex disap-
peared completely at a 1±2 ratio equal to 1:3 while at a 1:2
ratio, it was still observed. This is due to the fact that 1±
In the presence of excess amine, the labile N ligand
2
2
mol of amine are required per mol of complex in order to
produced by decomposition of the diazonium ion is replaced
by tri¯uoroethylamine to produce the amine complex 7.
Formation of the N-nitrosocompound 5 (not shown in
Scheme 1) may be explained by nucleophilic attack of the
secondary amine 3 to the nitrosyl ligand in 1.
form the organic products, another mol of 2 is used in the
formation of the amine complex 7, and part of the amine is
deactivated by protonation during the reaction. As shown in
Table 1, only 25% of organic products are formed with
respect to the amount of starting complex when an equi-
molar ratio of reagents is used. When larger ratios are
used, the material balance increases up to 60%, but it
stays approximately the same even when a large excess of
The other pathway shown in Scheme 1 (pathway B)
involves outer sphere electron transfer. Since the hydrogen
atoms attached to the amine functionality in 7 are acidic due

F. Di Salvo et al. / Tetrahedron 58 %2002) 4237±4244
4239
21
2
Scheme 1. Proposed mechanism for the reaction of tri¯uoroethylamine, 2, with [Ru(bpy) (NO)Cl] , 1.
21
2
Table 1. Organic products obtained by the reaction of [Ru(bpy) (NO)Cl] , 1, with 2,2,2-tri¯uoroethylamine, 2
1
±2ˆ1:1
1±2ˆ1:3
CH CN
ca. 10
19
,1
1±2ˆ1:3
CH CN/H
ca. 10
,1
4
1±2ˆ1:15
Solvent
CH
5
7
3
CN
3
3
2
O
None
14
17
a
a
CF
3
CF
3
CF
3
CF
3
CF
3
CH
CH
CH
CH
CH
2
2
2
2
2
NHCH CF
Cl (4)
N(NO)CH
2
3
(3)
2
CF
3
(5)
2
2
OH (6)
NNO
11
,1
3025
,1
16
2
,1
16
1
Results were obtained by H NMR as described in Section 8. They are expressed as moles of product per 100 mol of starting complex.
a
1
The H NMR quartet corresponding to this product overlapped with the quartet corresponding to 2.

4240
F. Di Salvo et al. / Tetrahedron 58 %2002) 4237±4244
21
Table 2. Organic products obtained by the reaction of [Ru(bpy) (NO)Cl]
2
,
approximately 64226ˆ38% (the amount of 7 produced
by the nucleophilic route minus its isolated amount) of 11
reacted by electron transfer, which is in good agreement
with the 36% yield obtained for 8 and is consistent with
the proposed mechanism.
1
, with n-butylamine (1±BuNH
2
ˆ1:3)
Yield (%)
1
-Butene
8.5
4.9
4.0
5.6
1.9
7.2
,1
6.5
2.0
21
trans-2-Butene
cis-2-Butene
An interesting point to discuss is related to the large dif-
ference in reactivity exhibited by tri¯uoroethylamine as
compared to n-butylamine. In a previous work we have
1
2
1
2
-Chlorobutane
-Chlorobutane
-Butanol
1
-Butanol
studied the reaction of n-butylamine with the same complex
obtaining a large amount of rearrangement products derived
Dibutylamine
N-Butyl-1-butanimine
Butyronitrile
1
from the free carbocation (Bu ) such as alkenes, 2-butanol
and 2-chlorobutane, as seen in Table 2. In the case of the
tri¯uoroethyldiazonium ion, although the main decomposi-
tion product is expected to be tri¯uorodiazoethane (by rapid
Results are expressed as moles of product per 100 mol of starting complex.
1
7
proton loss), we found no evidence for its formation. We
believe that the complete absence of this product or other
rearrangement products in the case of tri¯uoroethylamine is
mainly due to two factors, being the larger stability and
electrophilicity of the intermediate diazonium ion derived
from tri¯uoroethylamine as compared to the one derived
from n-butylamine, in agreement with the computational
results (see below). Both factors would tend to favor the
reaction of the postulated diazonium ion with hydroxide
ion or chloride ion before decomposition takes place.
to the proximity of the electron attracting metal center, a
certain amount of coordinated amide complex 11 can be in
equilibrium with the corresponding amine complex 7. Elec-
tron transfer from the amide complex to 1 produces the
reduced NO complex 8. It has been established that 8 is
1
8
produced by electrochemical reduction of 1, although to
our knowledge it is the ®rst time that one-electron reduction
21
of [Ru(bpy) (NO)Cl] is observed in this kind of reaction
2
(
namely, addition of amines to NO complexes).
The determined yield for 8 was found to be 36% in a 1:3
reaction mixture. This result indicates that under these
conditions 36% of the starting complex reacted by electron
transfer and 64% reacted by the nucleophilic route, which
gives raise to the organic products. This is in good agree-
ment (considering the experimental errors) with the 59%
material balance for the organic products shown in Table
As it can be observed in Table 2, the total amount of organic
products for the n-butylamine reaction is around 65% (prac-
tically the same as in the 2,2,2-tri¯uoroethylamine case).
This fact plus the observation of an FTIR signal at
2
1
1640cm
in the reaction mixture (attributable to the
reduced complex 8) indicates that part of the initial complex
1 is consumed by the electron transfer reaction shown in
Scheme 1 (pathway B) also in the case of n-butylamine.
1
for the 1:3 reaction (second column). At this point, we
would like to make clear that we believe that the equilibrium
among 11 and 7 is presumably displaced to the right under
the reaction conditions; a small amount of 11 present in
steady state concentration is enough to react via the electron
transfer pathway. The yield of 7 would be therefore indica-
tive of how much of 11 (or 7) reacted by the electron trans-
fer pathway. The isolated yield for 7 was determined to be
2.3. Computed coordination geometries
21
The optimized structures of [Ru(bpy) Cl(N R)] (Rˆbutyl,
2
2
phenyl or tri¯uoroethyl) are shown in Fig. 1. Relevant
geometrical parameters are presented in Table 3.
2
6% in a 1:3 reaction, therefore it can be deduced that
Regarding the reliability of our DFT scheme in predicting
21
Figure 1. Structure of [Ru(bpy)
2
(Cl)R] , (RˆBuN
2 2 3 2 2
, PhN , CF CH N ).

F. Di Salvo et al. / Tetrahedron 58 %2002) 4237±4244
4241
Ê
Table 3. Selected optimized bond distances and angles (A and degrees)
C1±N2
N1±N2
Ru±N1
N±O
Ru±N1±N2
N1±N2±C1
N
2
±
1.112
1.112
1.113
1.111
1.117
1.150
±
±
±
±
±
±
±
±
±
1
[
[
[
[
[
[
[
[
[
[
CF CH
3
BuN
PhN
Ru(bpy)
Ru(bpy)
Ru(bpy)
Ru(bpy)
Ru(bpy)
Ru(bpy)
Ru(bpy)
2
N
2
]
1.402
1.415
1.358
±
1.402
1.4101.142
1.3601.152
177.7
176.0
179.9
±
1
2
]
]
1
2
2
1
2
2
2
2
2
2
2
(Cl)N
(Cl)N
(Cl)N
(Cl)N
(Cl)NO]
(Cl)NO]
(Cl)NO] Exp.
2
2
2
2
]
CH
1.942
1.821
178.3
173.8
2
1
2
CF
3
]
169.3
2
1
Bu]
Ph]
1.849
1.855
173.5
178.7
1.142
1.183
1.131
167.8
176.9
2
1
21
1.775
1.841
1.749
1
21
a
a
Ref. 31.
the geometries of Ru complexes, previous results for
coordinated N complex are smaller than in the diazenido
2
2
Ru(NH ) Pz] compared very well with experiment.
1
14
[
comparison of our computed geometry for [Ru(bpy) ClN ]
A
derivatives, re¯ecting in the last case less triple bond char-
acter as a consequence of back-donation. Interestingly, the
larger degree of back-donation in the diazenido complexes
3
5
1
2
2
1
9
with experimental results for [Ru(bpy) Cl ](H O) and
2
2
2
5
[
the quality of our results in bipyridil complexes. The
Ru(bpy) Cl(CO)][ClO ] has been made in order to gauge
compared to the N coordinated system is also re¯ected in
2
2
4
the Ru±N1 bonds, which are considerably shorter in the
diazenido species, consistently with a stronger Ru±N
bond. As expected for the strong electron attracting charac-
ter of the ¯uoride substituents, the shortest Ru±N1 bond
corresponds to tri¯uoroethyldiazenido.
Ê
computed Ru±Cl bond distance is 2.440A , compared
Ê
with the experimental results of 2.427 and 2.392 A
for [Ru(bpy) Cl ](H O) and [Ru(bpy) Cl(CO)][ClO ],
2
2
2
2
5
4
respectively. The Ru±N distances range from 2.012 to
2
Ê
.051 A in our computed geometry and from 2.013
Ê
to 2.052 and 2.068 to 2.178 A in the [Ru(bpy) Cl ](H O)
5
We have also performed geometry optimizations of the
reactant [Ru(bpy) Cl(NO)] , 1, and of the reduced species
2
2
2
2
1
and [Ru(bpy) Cl(CO)][ClO ], respectively. Regarding bond
2
4
2
1
[Ru(bpy) Cl(NO)] , 8. For the reactant, the computed
angles, the N±Ru±N angle within the heterocyclic ring is
9.28 in [Ru(bpy) Cl ](H O) , ranges from 76.8 to 78.78 in
2
2
0
7
results agree very well with experiment. It can be noted
that there is an increase in the NO bond distance upon
reduction. This can be explained by considering that the
LUMO of 1 (Fig. 2) has a signi®cant contribution of the
2
2
2
5
[
optimized [Ru(bpy) ClN ] structure. It can be noted that
Ru(bpy) Cl(CO)][ClO ], and from 78.3 to 79.68 in our
2 4
1
2
2
the computed geometrical parameters compare very well
with experimental data.
p
p NO orbital. It can also be noted that the Ru±N bond
distance of the reduced species is substantially larger than
the one corresponding to the reactant.
The computed structures of the complexes show that the
aryl species is practically linear, while in the aliphatic
complexes there are larger deviations from linearity, with
Ru±N1±N2 and C1±N2±N1 angles of 173.8 and 169.38,
respectively, for the tri¯uoroethyldiazenido complex. N1±
N2 bond distances in the free diazonium salts and the
2.4. Stabilization by complexation: computational
results
Table 4 shows DE values for the decomposition reaction of
2
1
[
Ru(bpy) (N R)] (Eq. (3), RˆPh, Bu, CF CH ) and the
2
2
3
2
free diazonium ions. It can be observed in the table that
stabilization of the tri¯uoroethyldiazenido ligand due to
complexation (B3LYP-PCM) is closer to the highly stable
benzenediazenido than to the butyldiazenido. The large
stabilization of the tri¯uoroethyldiazenido is mainly due
to instability of the carbocation, induced by the electron-
attracting ¯uoride substituents.
2
1
1
%
2
‰
Ruꢀbpy† ꢀN CF CH †ClŠ ! ‰Ruꢀbpy† ꢀN †ClŠ 1 CF CH
2
2
3
2
2
2
3
ꢀ
3†
In vacuo, the order of stability for the free diazonium ions is
Ph.tri¯uoroethyl.butyl, as expected. It is interesting to
remark that in vacuo, complexation leads to an important
decrease of the computed C±N bond dissociation energies.
This is probably explained by the fact that complexation
brings together two positive species. On the other hand, in
acetonitrile solution, our computations predict an important
stabilization of the diazenido ligands by complexation. The
effect of the solvent may be understood in terms of a charge
21
2
Figure 2. LUMO of [Ru(bpy) Cl(NO)] .

4242
F. Di Salvo et al. / Tetrahedron 58 %2002) 4237±4244
Table 4. C±N bond dissociation energies (kcal/mol)
7% of alcohol is obtained in the reaction of n-butylamine
under the same conditions.
B3LYP
B3LYP-PCM
1
[
[
[
[
[
[
CF CH
3
2
N
2
]
22.2
6.5
8.1
217.9
37.4
11.8
26.6
34.6
10.2
25.6
37.1
40.9
2
1
Ru(bpy)
2
2
2
(Cl)N
(Cl)N
(Cl)N
2
2
2
2 3
CH CF ]
3. Computational methodology
1
BuN
2
]
2
1
Ru(bpy)
Bu]
1
The calculations were performed using a Gaussian basis set
2
PhN ]
2
1
2
1
Ru(bpy)
Ph]
implementation of DFT. The Kohn±Sham self-consistent
procedure was applied for obtaining the electronic density
and energy through the determination of a set of one-
2
2
stabilization effect: the dielectric stabilizes more effectively
the doubly charged diazenido complex than the singly
charged products. On the other hand, solvation does not
signi®cantly affect the computed results for the free diazo-
nium ions.
electron orbitals. Gaussian basis sets were used for the
expansion of the one-electron orbitals and also for the addi-
tional auxiliary set used for expanding the electronic
density. Matrix elements of the exchange-correlation poten-
2
3
tial were calculated by a numerical integration scheme.
The orbital and auxiliary basis sets optimized by Sim et
2
4
Strengthening of the N±C bond in a diazenido ligand by
complexation is not the only important feature to be con-
sidered in order to predict its stability. The electrophilicity
of the carbon atom attached to nitrogen has to be taken into
account since nucleophilic attack to this carbon will also
break the N±C bond. As it can be seen in Table 5, all
considered diazonium ions are thermodynamically unstable
towards nucleophilic attack of hydroxide ion or the corre-
sponding amine. We can relate the computed DE values
with the relative stabilities of the diazonium ions in solution
by assuming that the activation energies, and therefore the
reaction rates correlate with the thermodynamical DE
values.
al. for DFT calculations were used for C, N, and H
atoms. Basis sets for Ru were taken from Ref. 25. The
contraction patterns were (5211/411/1) for C, and N
(633321/53211/531) for Ru, and (41/1) for H. The contrac-
tion patterns for the electronic density expansion sets are:
(1111111/111/1) for C and N, (1111111111/11111/11111)
for Ru, and (111111/1) for H. A more detailed description of
the technical aspects of the program is given in Ref. 21.
Geometries were optimized for the isolated systems within
the local density approximation (LDA) using the Vosko±
2
6
Wilk±Nusair correlation functional. It has been shown
that LDA performs well in predicting bond distances and
2
7
angles in Werner-type transition metal complexes. Single
point calculations were performed at the LDA gas phase
optimized geometries using the hybrid B3LYP exchange-
It can be seen in Table 5 that the reaction of the tri¯uoro-
ethyldiazenido ligand with hydroxide is thermodynamically
more favorable than that of butyldiazenido and benzene-
diazenido due to the electron-attracting effect of the ¯uoride
substituents and correlates with the stabilities of the corre-
sponding carbocations. Assuming that the reaction rates
correlate with the thermodynamical DE values, we could
say that the tri¯uoroethyldiazenido is more nucleophilic
than the butyldiazenido and benzenediazenido. However,
in our experimental situation, the diazenido could also be
attacked by the corresponding amine to produce a secondary
amine plus a nitrogen complex, as it has been observed
2
8
correlation functional.
Solvent effects were modeled using the polarized continuum
model (PCM) scheme. The PCM implementation given in
Ref. 29, in which the self-consistency between the solute
wavefunction and solvent polarization is achieved during
the self-consistent ®eld cycle, has been employed. PCM
computations have been performed using the GAUSSIAN
3
0
98 software package.
1
6
before. Table 5 shows that in this situation, the tri¯uor-
oethyldiazenido ligand is less prone to attack than the butyl-
diazenido ligand. In conclusion, on one hand, there is an
important strengthening of the N±C bond that makes the
tri¯uoroethyldiazenido ligand more stable than its butyl
analog, but on the other hand, the increased electrophilicity
of the tri¯uoroethyldiazenido makes the reaction toward
hydroxide more favorable than in the case of the butyl-
diazenido. This is consistent with the results shown in
Tables 1 and 2: the yield for the corresponding alcohol is
4. Experimental
4.1. General comments
Unless otherwise noted, all manipulations were performed
with exclusion of oxygen and moisture using standard
1
13
15
Schlenk procedures. H, C and N NMR spectra were
recorded using a Bruker AM500 equipped with a broadband
probe. H, C and N NMR shifts are reported relative to
1
13
15
3
0% for the 2,2,2-tri¯uoroethylamine reaction, while only
CD CN (dˆ1.95, 1.80and 2136 ppm, respectively). IR
3
Table 5. Energetic changes (kcal/mol) for nucleophilic substitution in diazonium salts
Reaction
B3LYP
B3LYP-PCM
2
OH 1CF
1
3
CH
2
N
2
!N
!N 1BuOH
2
1PhOH
2
1CF
3
CH OH
2
2247.1
2105.7
286.8
295.7
260.0
263.3
249.0
2
OH 1BuN
1
2
2
2221.6
2223.3
265.6
270.1
253.3
2
1
2
OH 1PhN
CF CH NH
BuNH 1BuN
PhNH21PhN
!N
1
1
3
2
2
1CF
3
CH
2
N
2
!N
2
11(CF
3 2 2 2
CH ) NH
1
2
2
!N 1(Bu)
2
2
NH
2
1
2
1
!N
2
1(Ph) NH
2 2

F. Di Salvo et al. / Tetrahedron 58 %2002) 4237±4244
4243
spectra were recorded using a Nicolet 510P FTIR spectro-
meter with a Spectra Tech cell for liquids with CaF2
windows. UV±visible spectra were recorded using a
Hewlett-Packard 8453 spectrometer. Gas chromatograms
were done on a Shimadzu GC-17A gas chromatograph.
GC±mass spectra were recorded on a Shimadzu GC-17A
gas chromatograph attached to a GCMS-QP5000S mass
spectrometer. In both chromatographs, a tandem consisting
of two capillary Supelco SPB5 and SE54 columns was used
4.5.1. Product identi®cation and isolation. Compounds 3,
4, 6 and (E)-2,2,2-tri¯uoroethyldiazoate were identi®ed
by comparison of their spectroscopical properties with
authentic samples. Yields were determined by com-
1
paring the integrations due to the H NMR signals corre-
sponding to the bipyridine ligand (which was used as
an internal standard) with those corresponding to the
products.
1
Data for CF CH NHCH CF %3). H NMR (CD CN):
(60m £0.32 mm each). Chemical analyses were performed
with a Carlo Erba EA 1108 microanalyzer.
3
2
2
3
3
1
3
dˆ3.7 ppm (q), J ˆ6.6 Hz. C NMR (CD CN): d ˆ
HF
3
3
2
4
5.7 ppm (q).
4
.2. Reagents
1
Data for CF CH Cl %4). H NMR (CD CN): dˆ4.1 ppm (q),
3
2
3
1
3
32
J ˆ8.5 Hz. C NMR (CD CN): dˆ43.5 ppm (q). GC±
Acetonitrile and methanol were purchased from J. T.
Baker and distilled from CaH2´ CD OD, CD CN,
[RuCl (bpy) ] and 2,2,2-tri¯uoroethylamine were pur-
2 2
chased from Aldrich and used as received. Na NO was
HF
3
1
MS (70eV); m/z (relative intensity): 120(24, M ), 118 (71),
3 (42), 69 (12).
3
3
8
1
5
2
1
Data for CF CH N%NO)CH CF %5). H NMR (CD CN):
1
8
purchased from MSD Isotopes. [Ru(bpy) Cl(NO)](PF )
2
3
2
2
3
3
6
1
5
3
and [Ru(bpy) Cl(NO )] were prepared by known pro-
1
dˆ5.1 ppm (q), J ˆ4.4 Hz.
N
NMR (CD CN):
3
HF
2
2
1
5
dˆ192 ppm (corresponding to CF CH N NO). FTIR
cedures. [Ru(bpy) Cl(NO)](PF ) was prepared from
2
RuCl (bpy) by modifying a previously reported proce-
2
3
2
6 2
2
1
15
21
(
CH CN): n(NNO)ˆ1631.8 cm ; n(N NO)ˆ1590cm
.
3
2
3
1
dure: the synthesis was carried out under an inert atmo-
sphere of nitrogen. The [Ru(bpy) Cl(NO)](PF ) complex
so obtained was orange, instead of brown or green as
obtained by the original technique. The difference was prob-
ably due to contamination of the green sample with a small
amount of oxo complex. Anal. calcd: C, 31.24; N, 9.11; H,
1
Data for CF CH OH %6). H NMR (CD CN): dˆ3.9 ppm
3
2
1
3
2
6 2
3
32
(
q), J ˆ9.1 Hz. C NMR (CD CN): dˆ60.0 ppm (q).
HF
3
2
Data for %E)-2,2,2-tri¯uoroethyldiazoate %CF CH NvNO ).
H NMR (CD CN): dˆ4.0ppm (q), J ˆ10.6 Hz.
3
2
1
17
3
HF
1
5
2
.10; found: C, 31.20; N, 9.38; H, 2.08. [Ru(bpy) Cl( NO)]
2
2
1
5
[
Ru(bpy) NH CH CF (X)] where XˆCl (compound 7) or
(PF ) was prepared by this same procedure, using Na NO
2
instead of NaNO2.
2
2
2
3
6
2
CH CN, was obtained by precipitation from the reaction
3
mixture at 2188C and isolated by centrifugation. Then the
dark orange solid was identi®ed by H NMR (CD CN):
1
3
4
[
.3. Reactions of 2,2,2-tri¯uoroethylamine with
Ruꢀbpy) ClꢀNO)]ꢀPF6)2
13
dˆ3.77 ppm (broad), C NMR (CD CN): dˆ41.9 ppm
3
2
32
q). m/z: 443 ([Ru(bpy) NH CH CF ]±CF ). Isolated
(
yield: 26%.
2 2 2 3 3
In all cases, the mixtures were transferred to the correspond-
ing vessel after the reaction was completed with the aid of
syringes and under inert atmosphere. The reaction mixtures
were analyzed by UV±visible, FTIR and NMR spectro-
scopies. When NMR spectra were ran on the reaction
mixtures, CD CN was used as the reaction solvent instead
3
of CH CN. In the cases that UV±visible spectra were deter-
3
mined, the reaction mixture was diluted around 2000 times
with CH CN.
1
Compound 8 ([Ru(bpy) (Cl)NO] ) was isolated from the
2
reaction mixture by column chromatography with silica
gel. CH OH±HClˆ100:1 was used as the solvent system.
18
3
Compound 8 was identi®ed by comparison of its UV±
visible and FTIR spectra with those previously reported.
Although we could not get a good isolated yield for 8
due to its instability (it oxidizes rather easily), we deter-
mined its yield to be 36% by looking at its corresponding
UV±visible band at 310nm in a 1:3 reaction mixture
3
4
18
4
.4. Reactions in solution
(
1ˆ1.62£10 ).
2
,2,2-Tri¯uoroethylamine (3.2 mL, 0.04 mmol for the 1:1
A broad signal attributable to a Ru(III) amine complex was
observed by C NMR of the reaction mixture. C NMR
1
3
13
reaction; 9.6 mL, 0.12 mmol for the 3:1 reaction) was
added to a solution of 30.4 mg (0.04 mmol) of [Ru(bpy)2
Cl(NO)](PF ) in 0.5 mL of acetonitrile in a 5 mL round-
3
2
(CD CN): dˆ43.5 ppm.
3
6
2
bottomed ¯ask. After a few minutes, the original orange
solution changed to dark red. It was allowed to react at
room temperature for 2 days protected from light.
Acknowledgements
4
.5. Heterogeneous reaction
This work was supported by University of Buenos Aires
(project TX-042), VW Stiftung and ANPCYT (project #
2
3
,2,2-Tri¯uoroethylamine (48 mL, 0.6 mmol) was added to
0.4 mg (0.04 mmol) of [Ru(bpy) Cl(NO)](PF ) . The solid
06-00000-01704). We thank the Cambridge Crystallo-
graphic Data Center for having provided us the Cambridge
Structural Database Version 5.18. F. D. and D. A. E. are
members of the scienti®c staff of CONICET. F. D. S. and A.
C. are UBA fellows.
2
6 2
was totally dissolved by the amine producing a dark red
solution. The reaction mixture was allowed to react for
3
h at room temperature protected from light.

4244
F. Di Salvo et al. / Tetrahedron 58 %2002) 4237±4244
References
S. R.; Edwards, A. J. J. Chem. Soc., Chem. Commun. 1980,
50.
0. Nagao, H.; Nishimura, H.; Funato, H.; Ichikawa, Y.; Howell,
7
2
2
1
. Doctorovich, F.; Escola, N.; Tr a pani, C.; Estrin, D. A.;
Turjanski, A. G.; Gonz a lez Lebrero, M. C. Organometallics
F. S.; Mukaida, M.; Kakihana, H. Inorg. Chem. 1989, 28,
3
955.
2
000, 19, 3810.
1. Estrin, D. A.; Corongiu, G.; Clementi, E. In METECC, Meth-
ods and Techniques in Computational Chemistry; Clementi,
E., Ed.; Stef: Cagliari, 1993; Chapter 12.
2
. Mohrig, J. R.; Keegstra, K. J. Am. Chem. Soc. 1967, 89, 5492.
. Berner, D.; McGarrity, J. F. J. Am. Chem. Soc. 1979, 101,
3
3
135.
2
2
2
2. Kohn, W.; Sham, L. J. Phys. Rev. 1965, A140, 1133.
3. Becke, A. D. J. Chem. Phys. 1988, 88, 1053.
4
. Herrmann, W. A.; Biersack, H. Chem. Ber. 1977, 110, 896.
. Diamantis, A. A.; Chatt, J.; Leigh, J. G.; Heath, G. A. J.
Organomet. Chem. 1975, 84, C11.
5
4. (a) Sim, F.; Salahub, D. R.; Chin, S.; Dupuis, M. J. Chem.
Phys. 1991, 95, 4317. (b) Sim, F.; St-Amant, A.; Papai, Y.;
Salahub, D. R. J. Am. Chem. Soc. 1992, 114, 4391.
5. Godbout, N.; Salahub, D. R.; Andzelm, J.; Wimmer, E. Can. J.
Chem. 1992, 70, 560.
6. Hillhouse, G. L.; Haymore, B. L.; Herrmann, W. A. Inorg.
Chem. 1979, 18, 2423.
7. Casey, C. P.; Widenhoefer, R. A.; Hayashi, R. K. Inorg. Chem.
8
9
2
2
2
1
995, 34, 2258.
. Bowden, W. L.; Little, W. F.; Meyer, T. J. J. Am. Chem. Soc.
977, 99, 4340.
6. Vosko, S. H.; Wilk, L.; Nusair, M. Can. J. Chem. 1980, 58,
1
200.
1
7. (a) Bray, M. R.; Deeth, R. J.; Paget, V. J.; Sheen, P. D. Int. J.
Quantum Chem. 1996, 61, 85. (b) Sosa, C.; Andzelm, J.; Elkin,
B. C.; Wimmer, E. J. Phys. Chem. 1992, 96, 6630.
. Li, J.; Noodleman, L.; Case, D. A. Electronic Structure Calcu-
lations: Density Functional Methods with Applications to
Transition Metal Complexes. In Inorganic Structure and
Spectroscopy; Solomon, E. I., Lever, B. P., Eds.; Wiley:
New York, 1999.
2
2
3
8. (a) Becke, A. D. J. Chem. Phys. 1993, 98, 5648. (b) Lee, C.;
Yang, W.; Parr, R. G. Phys. Rev. B 1988, 37, 785.
9. Cossi, M.; Barone, V.; Cammi, R.; Tomasi J. Chem. Phys.
Lett. 1996, 255, 327.
1
0. Deeth, R. J. Computational Modeling of Transition Metal
Centers; Structure and Bonding, Vol. 82; Springer: Berlin,
0. Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.;
Robb, M. A.; Cheeseman, J. R.; Zakrzewski, V. G.; Montgom-
ery, Jr., J. A.; Stratmann, R.; Burant, J.; Dapprich, S.; Millam,
J. M.; Daniels, A. D.; Kudin, K. N.; Strain, M. C.; Farkas, O.;
Tomasi, J.; Barone, V.; Cossi, M.; Cammi, R.; Mennucci, B.;
Pomelli, C.; Adamo, C.; Clifford, S.; Ochterski, J.; Petersson,
G. A.; Ayala, P. Y.; Cui, Q.; Morokuma, K.; Malick, D. K.;
Rabuck, A. D.; Raghavachari, K.; Foresman, J. B.;
Cioslowski, J.; Ortiz, J. V.; Baboul, A. G.; Stefanov, B. B.;
Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi, I.; Gomperts,
R.; Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.;
Peng, C. Y.; Nanayakkara, A.; Gonzalez, C.; Challacombe,
M.; Gill, P. M. W.; Johnson, B.; Chen, W.; Wong, M. W.;
Andres, J. L.; Gonzalez, C.; Head-Gordon, M.; Replogle, E.
S.; Pople, J. A. Gaussian 98, Rev. A7, Gaussian, Inc.: Pitts-
burgh, PA, 1998.
1995.
1
1. Cramer, C. J.; Truhlar, D. G. In Quantitative Treatments of
Solute/Solvent Interactions; Politzer, P., Murray, J. S., Eds.;
Elsevier: New York, 1994.
1
1
1
1
2. Ho, L. L.; MacKerell, A. D.; Bash, P. A. J. Phys. Chem. 1996,
100, 4466.
3. Estrin, D. A.; Baraldo, L. M.; Slep, L. D.; Barja, B. C.; Olabe,
J. A. Inorg. Chem. 1996, 35, 3897.
4. Hamra, O. Y.; Slep, L. D.; Olabe, J. A.; Estrin, D. A. Inorg.
Chem. 1998, 37, 2033.
5. Estrin, D. A.; Hamra, O. Y.; Paglieri, L.; Slep, L. D.; Olabe,
J. A. Inorg. Chem. 1996, 35, 6832.
1
1
1
1
6. Doctorovich, F.; Tr a pani, C. Tetrahedron Lett. 1999, 40, 4635.
7. Ho, J.; Fishbein, J. C. J. Am. Chem. Soc. 1994, 116, 6611.
8. Callahan, R. W.; Meyer, T. J. Inorg. Chem. 1977, 3, 16.
9. (a) Eggleston, D. S.; Goldsby, K. A.; Hodgson, D. J.; Meyer,
T. J. Inorg. Chem. 1985, 24, 4573. (b) Clear, J. M.; Kelly,
J. M.; O'Connel, C. M.; Vos, J. G.; Cardin, C. J.; Costa,
31. Godwin, J. B.; Meyer, T. J. Inorg. Chem. 1971, 10, 471.
1
32. The C NMR signal corresponding to the CF
observed due to the C±F splitting.
3
3
unit was not