Substitution of labile triflate in [(triphos)Re(CO)2(OTf)]: A new synthetic route to mononuclear and dinuclear Re(I) complexes

Article abstract of DOI:10.1039/a806683c

New synthetic routes to the neutral complex [(triphos)Re(CO)₂(OTf)] [triphos = MeC(CH₂PPh₂)₃, OTf = CF₃SO₃^-] (3) are reported. The triflate ligand in 3 is labile and can be easil

Full text of DOI:10.1039/a806683c

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Substitution of labile triÑate in [(triphos)Re(CO) (OTf)] : a new
2
synthetic route to mononuclear and dinuclear ReI complexes
Paola Bergamini,a Fabrizia Fabrizi DeBiani,b Lorenza Marvelli,*,a Nicoletta Mascellani,a
Maurizio Peruzzini,*,c Roberto Rossi*,a and Piero Zanellob
a Dipartimento di Chimica, Universita di Ferrara, V ia L . Borsari 46, 44100 Ferrara, Italy
b Dipartimento di Chimica, Universita di Siena, Pian dei Mantellini 44, 53100 Siena, Italy
c Istituto per lo Studio della Stereochimica ed Energetica dei Composti di Coordinazione,
ISSECC, CNR, V ia J. Nardi 39, 50132 Firenze, Italy
Received (in Montpellier, France) 21st August 1998, Accepted 6th October 1998
New synthetic routes to the neutral complex [(triphos)Re(CO) (OTf)] [triphos \ MeC(CH PPh ) , OTf \
2
2
2 3
CF SO ~] (3) are reported. The triÑate ligand in 3 is labile and can be easily replaced by di†erent halides and
3
3
pseudohalides (CN~, N ~, SCN~, SeCN~, OCN~) to give new mononuclear octahedral ReI complexes of formula
3
[(triphos)Re(CO) (X)] (X \ Cl~, Br~, I~, CN~, N ~, SCN~, SeCN~, OCN~). In some cases, when a double
2
3
proportion of 3 is treated with the appropriate pseudohalide, rare examples of binuclear ReI complexes featuring a
single bridging pseudohalide ligand, [M(triphos)Re(CO) N (l-X)]Y (X \ CN~, N ~, SCN~, SeCN~; Y \ OTf,
2 2
3
BPh ~), have been obtained. All of the new ReI complexes have been characterized by conventional spectroscopic
4
methods and by electrochemical and spectroelectrochemical techniques. Selected examples of regioselective
electrophilic alkylations of both halide and pseudohalide ligands are also reported. Noticeably, selective
methylation of [(triphos)Re(CO) (g1-X-XCN)] (X \ S, Se) a†ords the complexes [(triphos)Re(CO) Mg1-X-
2
2
X(Me)(CN)N]OTf, which contain the unprecedented methylsulfocyanate and methylselenocyanate ligands.
The coordinatively unsaturated 16-electron fragment
parative routes to 3 starting from the more easily available
[(triphos)Re(CO) ]` [triphos \ MeC(CH PPh ) ] is a versa-
[(triphos)Re(CO) (Cl)] (2). Also, we shall describe the use of 3
2
2
2 3
2
tile precursor for a large number of ReI organometallic com-
plexes containing hydride, vinylidene, alkynyl, acyl, alkyne,
carbene and carbyne ligands.1 Removal of a labile ligand dis-
posed trans to the triphos apical phosphorus atom is a very
simple way to generate this synthon in solution. In this regard,
we have already reported that the dihydrogen cationic
complex [(triphos)Re(CO) (g2-H )]BPh easily eliminates H
as a precursor for the synthesis of a large family of mono-
nuclear and binuclear complexes of ReI. The latter, of formula
[M(triphos)Re(CO) N (l-X)]Y (Y \ OTf, BPh ~), are worthy of
2 2
4
mention because they represent unusual examples of bridging
symmetrical (X \ N ~) or asymmetrical (X \ CN~, SCN~,
3
SeCN~) pseudohalide ligands.
2
2
4
2
to a†ord the [(triphos)Re(CO) ]` moiety.1 In this paper we
Results and discussion
2
show that the easily accessible [(triphos)Re(CO) (OTf)] (3)
2
Synthesis of [(triphos)Re(CO) (OTf)] (3)
2
represents an alternative and more convenient precursor for
the generation of the [(triphos)Re(CO) ]` fragment.
The OTf group has been regarded as a classical ““non-co-
3 represents an important reagent to enter into the chemistry
2
of the very stable ReI fragment [(triphos)Re(CO) ]`, whose
2
ordinatingÏÏ anion for a long time, before the existence of its
complexes with di†erent transition metals was deÐnitively
proven.2 Currently, it is considered as a poorly co-ordinating
anion and its salts and derivatives are largely used in synthetic
inorganic and organometallic chemistry.2,3 The importance of
triÑate compounds stems from their many synthetically useful
properties such as their good solubility in polar solvents, their
lack of oxidizing power, their water stability and, above all,
their proclivity to be replaced by many di†erent nucleophiles.
This latter property has been related to the electron-
withdrawing properties of both the CF and wSO w triÑate
organometallic chemistry is currently under examination by
our groups.1 This complex can be prepared by several routes,
which are summarized in Scheme 1. The original preparation
(route A) involves the straightforward alkylation of
[(triphos)Re(CO) (H)] (1) with MeOTf, which a†ords 3 in
2
moderate yield following methane elimination.1a The triÑate
complex 3 can alternatively be synthesized (route B) by proto-
nation of 1 with HOTf. This reaction a†ords 3 upon elimi-
nation of molecular hydrogen from the non-classical hydride
[(triphos)Re(CO) (g2-H )], which is Ðrst formed. Interestingly,
2
2
although triÑate is a very poor co-ordinating ligand and the
molecular hydrogen complex is stable at room temperature,
co-ordination of triÑate ion is competitive even when a pro-
3
2
components. The lability of the triÑate ligand is of paramount
importance for the generation of several co-ordinatively
unsaturated species that are largely used for both synthetic
and catalytic applications in modern organometallic chem-
istry.4
tective H atmosphere is employed.5
2
In order to avoid the use of the hydride complex and to
improve the preparation of 3, we decided to search for a more
simple route starting from the readily accessible
Complex 3 was previously obtained from the reaction
between the neutral monohydride [(triphos)Re(CO) (H)] (1)
[(triphos)Re(CO) (Cl)] (2).1 In agreement with our expecta-
2
2
and MeOTf.1a We report now on several improved pre-
tions, we have found that 3 can be prepared by several alter-
native strategies, which share the use of 2 as starting material.
These synthetic procedures include: the metathesis of chloride
by triÑate using AgOTf (route C), the reaction of 2 with HOTf
* Corresponding
authorsÏ
e-mail:
Maurizio
Peruzzini,
peruz=service.area.Ð.cnr.it; Lorenza Marvelli, mg1=dns.unife.it
New J. Chem., 1999, 207È217
207

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Scheme 2
P
P
Re
X
X–
P
P
Scheme 1
CO
CO
CO
CO
P
P
Re
MeX
MeOTf
(route D) and the electrophilic alkylation of 2 with MeOTf
(route E).
OTf
3
X = Cl, 2; Br, 4; I, 5
Method C a†ords 3 by removal of the chloride ligand from
2 in the form of insoluble AgCl. This is a very reliable and
sound synthetic procedure (yield higher than 85%), but is not
useful for a bulk preparation of 3 due to the use of the light-
sensitive and relatively expensive silver triÑate.
Protonation of 2 with HOTf (method D) is an alternative
method for the preparation of 3. From a mechanistic point of
view, we hypothesise that 3 is formed following the elimi-
nation of a weakly co-ordinated HCl ligand from a transient
Scheme 3
bility of the halocarbon adduct is due to the existence of easy
reactivity paths that eliminate MeCl. Thus, MeCl is readily
substituted by the triÑate counter anion to give 3. Even in the
absence of co-ordinating anions, the halocarbon adduct is
replaced in the co-ordination sphere of the metal by an intra-
molecular agostic interaction, or, depending on the nucleo-
philicity of the solvent, by solvent co-ordination. As a matter
of fact, on repeating the electrophilic attack on 2 with the
Meerwin reagent, Me OBF , in THF, the agostic derivative
and undetected adduct of formula [(triphos)Re(CO) (HCl)]`.
2
Co-ordination of HCl is well-documented by in situ NMR
3
4
4
[(triphos)Re(CO) ]BF is the principal species formed,
experiments and has been reported to be the Ðrst step of the
2
together with some [(triphos)Re(CO) (g1-OC H )]`.11
proton transfer reaction on hydride ligands.6 In the case of the
2
4 8
rhenium hydride [(triphos)Re(CO) (H)] (1), it has been
2
Substitution reactions of [(triphos)Re(CO) (OTf)] with X—
[X = Cl, (2); Br, (4); I, (5)]
demonstrated by IR and NMR techniques that on proto-
2
nation of the hydride complex, the formation of a labile
hydrogen-bond adduct takes place before the hydrogen trans-
fer step is completed.7
When a THF solution of [(triphos)Re(CO) (OTf)] is stirred
with the halide salts NaCl, KBr or KI at room temperature,
2
Nevertheless, the formation of HCl as a secondary product
of route D may cause several complications in the isolation of
3 as well as in its use in further chemical reactions. Thus, the
remaining procedure E, which falls under the same reaction
paradigm, appears as the most convenient to prepare 3
because the only secondary product that is formed is the vola-
tile and easily removed MeCl. The reaction occurs promptly
(5 min), providing an easy access to pure 3 in high yield (90%).
The elimination of MeCl from 2 is the key step in the forma-
tion of 3, as conÐrmed by an in situ 1H NMR experiment
the mononuclear complexes [(triphos)Re(CO) (X)] [X \ Cl,
2
(2); Br, (4); I, (5)] are obtained after a few hours stirring
(Scheme 3). All of these complexes are air-stable in both the
solid state and solution. They are sparingly soluble in
dichloromethane and chloroform and behave as non-
electrolytes in nitroethane.
Attempts to prepare the corresponding Ñuoroderivative by
the same route, using di†erent sources of Ñuoride such as
NaF, KF or (PPN)F, were unsuccessful, most likely because of
the low affinity of the very hard base Ñuoride for the soft ReI
acid.12,13
(CDCl ), which features a singlet at 3.0 ppm ascribable to
3
CH Cl.
The bromo and iodo derivatives, 4 and 5, react with an
3
Although electrophilic alkylation of halide complexes has
excess of methyl triÑate to reform [(triphos)Re(CO) (OTf)]. As
2
been scarcely considered from a synthetic point of view, there
are some precedents indicating that a halide ligand can be
removed in the form of the corresponding halogenated hydro-
carbon upon reaction with methyl triÑate.8 In the case at
hand, addition of MeOTf likely forms an unstable
anticipated above for the reaction of 2 with MeOTf, elimi-
nation of CH Br or CH I was observed, respectively, by 1H
3
3
NMR spectroscopy.8 Complexes 4 and 5 have been character-
ized by elemental analysis, IR and multinuclear NMR spec-
troscopies (Table 1) as well as by electrochemical
measurements (see below, Table 2). The 31PM1HN NMR
[(triphos)Re(CO) (ClMe)]` cation (Scheme 2) in which MeCl
2
acts as an g1-ligand towards the rhenium centre by using a
spectra of 4 and 5 exhibit the AM splitting pattern expected
2
lone pair on the chloride atom. In keeping with this hypothe-
sis, it is worthy of mention that an extensive literature exists
on the co-ordinating abilities of several halocarbons toward
strong Lewis acid moieties,9 including some rhenium
assemblies.10 The chloromethyl compound, however, has not
been intercepted, even when the alkylation reaction is carried
out at low temperature in an NMR tube and it is monitored
by 31PM1HN NMR spectroscopy. Probably, the intrinsic insta-
for an octahedral complex with the tripodal triphos ligand
occupying a face of the co-ordination polyhedron.14h16
Synthesis of [(triphos)Re(CO) (CN)] (6) and
2
[{(triphos)Re(CO) } (l-CN)]OTf (7)
2 2
When the triÑate complex 3 is treated with 5 equiv. of
[Bu N]CN in THF at room temperature, yellow micro-
4
208
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Table 1 31PM1HN NMR spectral data and selected IR spectral absorptions for the complexesa
31PM1HN
IR
Complex
d /ppm
d /ppm
J
/Hz
m
/cm~1
m
/cm~1
A
M
AM
(CO)
(other)
3
6.20
2.40
2.15
[10.11
14.7
14.7
14.6
15.3
18.4
16.3, 19.5
14.9
16.3
17.0
17.1
17.4
16.0
18.3
18.1
15.3, 13.7
21.5
19.2
19.6
1967, 1902
1948, 1887
1950, 1889
1950, 1892
1946, 1890
1967, 1908
1936, 1879
1952, 1894
1956, 1900
1320 m(g1-OTf)
2
[18.23
4
[20.14
5
[0.12
[24.70
6
[5.90
[17.88
2106 m(CN)
7b
0.21, [7.41
[17.12, [17.66
[15.07
2097 m(CN), 1275 m(OTf)
2044 m (N ), 1334 m (N )
8
1.07
0.75
as 3 sy 3
2122 m (N ), 1272 m(OTf)
9
[11.96
as
3
10
10º
11
11º
12b
13b
14/14ºb
15
16
17
18
[2.42
[15.95
2106 m(SCN)
0.07
[15.58
2077 m(NCS)
2103 m(SeCN)
2066 m(NCSe)
2140, m(SCN), 1273 m(OTf)
2142 m(SeCN), 1271 m(OTf)
2234 m(NCO)
2184 m(CN), 1269 m(OTf)
2139 m(SCN), 1267 m(OTf)
2183, m(SeCN), 1271 m(OTf)
[3.41
[16.18
1958, 1898
[0.23
[15.01
[2.13, [2.52
[2.18, [3.47
1.79, 3.75
[12.04
[5.19
[12.90, [14.70
[12.90, [15.97
[16.42, [18.94
[14.15
1958, 1900
1960, 1900
1950, 1886
1971, 1915
1956, 1900
1956, 1898
[10.52
[4.60
[9.93
[3.53
[13.10
18.2
a The 31PM1HN NMR spectra were recorded in CD Cl at room temperature and all exhibit an AM splitting pattern. b (AA@M M@ ) spin systems.
2
2
2
2 2
crystals of the cyanide complex 6, [(triphos)Re(CO) (CN)], are
In order to explore this possibility, we have reacted 6 with a
second equivalent of 3. As a result, the bridging cyanide deriv-
2
obtained in pure form and good yield (Scheme 4). Complex 6
is a non-electrolyte in nitroethane and exhibits an IR spec-
trum featuring, besides the two strong carbonyl stretching
vibrations, a very strong band (2106 cm~1) assigned to
m(CN)17 (Table 1).
ative [M(triphos)Re(CO) N (l-CN)]OTf, (7), is obtained in
2 2
almost quantitative yield. The same product can be prepared
by reacting 3 and [Bu N]CN in a rigorous 1 : 0.5 ratio
4
(Scheme 4).
The high-energy shift of the cyanide absorption with respect
In keeping with the cationic nature of 7, the infrared spec-
trum exhibits a slightly red-shifted CN stretching vibration
(2097 cm~1) in comparison to the corresponding band of the
neutral monomeric derivative 6 (2106 cm~1),19b while the
31PM1HN NMR spectrum in CD Cl consists of two well-
to unco-ordinated cyanide (2050 cm~1 in [Bu N]CN) points
4
to a stronger r-donor than p-acceptor contribution in the
RewCN bond.17,18 This behaviour, which has been already
reported by Gladysz and coworkers for the mononuclear
[Cp*Re(NO)(PPh )(CN)] (Cp* \ C H or C Me ) comp
2
2
separated 1 : 1 AM spin systems, which are temperature
3
5
5
5
5
2
lexes,10c,19 suggests an increase of the M dp ] CO p* back-
donation and agrees also with the low-frequency shift
observed for the CO stretches (1946, 1890 cm~1), in compari-
son to the triÑate complex 3 (1967, 1902 cm~1). The cyanide
ligand in 6 exhibits a diagnostic 13CM1HN NMR absorption at
131.4 ppm and is coupled to only one phosphorus atom
invariant in the temperature window of dichloromethane. The
NMR pattern reÑects the inequivalency of the two donor ends
of the cyanide bridge and the di†erent electronic density expe-
rienced by the two rhenium atoms. The Ðrst set of resonances
features a triplet at 0.21 ppm and a doublet at [17.12 ppm
(2J \ 16.3 Hz), while the second one falls at [7.41 (t) and
PP
(2J
\ 10.9 Hz). Similar NMR parameters have been
[17.66 (d) (2J \ 19.5 Hz). As a consequence of the di†erent
CP trans
PP
reported for other mononuclear ReI-cyanide complexes.10c, 19a
Cyanide complexes of transition metals have attracted
renewed interest during the last decade because the residual
electron density on the nitrogen makes these complexes suit-
able for use as reagents with electrophilic transition metal
fragments, with which they form homo- or heteronuclear
bimetallic species in which a cyanide ligand bridges two tran-
sition metals.19b,20 These binuclear compounds appear rele-
vant in the topical areas of material sciences (materials with
non-linear optical properties,21 energy storage devices22), as
well as biological sciences.23
nature of the donor atoms of the CN group, the two axial
phosphorus atoms in [(triphos)Re]` have very di†erent
chemical shifts, one being trans to carbon and the other one
trans to nitrogen in the linear PwRewCy NwRewP six
atom assembly. Interestingly, one of the two triplets (d [ 7.41)
appears much broader than the other one resonating at d 0.21
and exhibits a signiÐcantly longer relaxation time (2.0 vs. 0.7 s).
This experimental Ðnding allows one to assign the broader
resonance to the P atom located trans to the nitrogen end of
the cyanide ligand. It is indeed conceivable that the strong
interaction with the 14N nucleus, which has a large electric
quadrupolar moment, causes severe line broadening of the
phosphorus resonance. Moreover, the concomitant increase of
T measured for the same P resonance presumably reÑects the
1
smaller magnetic moment of 14N vs. 13C, which, reducing the
dipolarÈdipolar interaction, increases the relaxation time of
the faced P nucleus.24,25
Synthesis of [(triphos)Re(CO) (N )] (8) and
2
3
[{(triphos)Re(CO) } (l-N )]Y [Y = OTf, (9); BPh —, (9-
2 2
3
4
BPh )]
4
When
a large excess (P3 equiv.) of bis(triphenylphos-
phoranylidene)azide is added to a stirred dichloromethane
solution of 3, the yellow colour immediately turns deep red.
Addition of n-hexane precipitated pale yellow microcrystals of
Scheme 4
New J. Chem., 1999, 207È217
209

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[(triphos)Re(CO) (N )] (8), in good yield (Scheme 5). 8
A useful and largely applied diagnostic tool, to discriminate
between the two possible linkage isomers, is IR spectroscopy.
In this respect, a useful marker for assigning the N-bound vs.
X-bound co-ordination is the m(CN) band above 2000
cm~1.18,29b,31 In the thiocyanate complex 10, the presence of
an S-co-ordinated ligand is readily inferred from the strong
m(CN) band at 2106 cm~1. This absorption is moved to a
higher frequency with respect to the unco-ordinated thiocy-
anate anion, suggesting that the ligand is S- rather than N-
bound.29b,31 This behaviour markedly di†ers from that
reported by Abram and co-workers for the ReV and ReIII
compounds of formula [ReN(NCS) (CH CN)(Ph P) ],
2
3
behaves as a non-electrolyte in dichloromethane and exhibits
in the IR spectrum two strong bands at 2044 and 1334 cm~1,
which are assigned to the antisymmetric and symmetric
stretches of a terminal azido ligand, respectively.18,26
Monitoring in THF the reaction of 3 with a stoichiometric
amount of (PPN)N by 31PM1HN NMR, a second less intense
3
AM spin system is observed together with the resonances of
2
8. The two products are formed in a 10 : 1 ratio, which does
not change within a week and does not appear to be tem-
perature dependent. The new product can be obtained in pure
form and quantitative yield by allowing 3 to react with
2 3
3 2
(PPN)N in a rigorous 1 to 0.5 ratio. On the basis of several
[ReN(NCS) (Me PhP) ], [Re(NS)(NCS) (Me PhP) ] and
3
2
2
3
2
2
3
observations, the binuclear formula [M(triphos)Re(CO) N (l-
[ReCl (NCS)(Me PhP) ], for which an N-co-ordination has
2 2
N )]OTf, in which an azido ligand is sandwiched between two
3
2
2
3
been proposed by IR measurements and has been authenticat-
ed by X-ray di†raction analysis.32
symmetric [(triphos)Re]` moieties, is assigned to 9. In partic-
ular, the IR spectrum shows a strong and broad absorption at
2122 cm~1, characteristic of bridging azido ligands.26
In the case at hand, a rationale for the preference of S-co-
ordination vs. N-co-ordination may be found in the softness of
ReI, which therefore exhibits a higher affinity for sulfur than
for nitrogen. In keeping with the presence of an S-bound thio-
cyanate ligand in 10, the 13CM1HN NMR spectrum exhibits a
broad singlet at 124.5 ppm, which is in line with other NMR
authenticated S-bound thiocyanates.33
Terminal azido complexes of the transition metals have
been reported to undergo thermal N elimination to a†ord
2
metal-nitride complexes.27 In particular, this reaction readily
takes place with rhenium derivatives in high oxidation states
of the metal, owing to the high stability of the Rey N core.28
In the present case, however, no reaction occurs even under
forcing conditions and the starting mono- and binuclear azido
complexes are recovered unchanged after prolonged reÑux in
THF.
On replacing NH SCN with KSeCN in the previous reac-
4
tion, deep green microcrystals of [(triphos)Re(CO) (g1-Se-
2
SeCN)] (11) are obtained in good yield. On the basis of similar
arguments [m(CN) at 2103 cm~1 and an upÐeld-shifted
quartet in the 13CM1HN NMR spectrum at d 108.9 33] the
presence of a Se-bound selenocyanate ligand is hypothesized
in complex 11. This structural assignment is indirectly sup-
ported by an in situ NMR study of the alkylation reaction
with MeOTf (see below), which points to the occurrence of a
regioselective methylation of the selenium atom.
Synthesis of the pseudohalide complexes [(triphos)Re(CO) (g1-
2
X-XCN)] [X = S, (10); Se, (11)] and [{(triphos)Re(CO) } (l-
2 2
g1-X, g1-N-XCN)]OTf [X = S, (12); Se, (13)]
Addition of a large excess of NH SCN to a stirred THF solu-
4
tion of 3 at room temperature results in the formation of the
Monitoring the reaction between 3 and one equivalent of
purple neutral complex [(triphos)Re(CO) (g1-S-SCN)] (10),
NH SCN in THF-d (in a 5 mm NMR tube by 31PM1HN
2
4
8
where the thiocyanate ligand is S-co-ordinated to rhenium,
NMR spectroscopy) reveals that the AM pattern attributed
2
(Scheme 6). Thiocyanate (and selenocyanate, see below) com-
plexes exhibit linkage isomerism, being capable of co-
ordinating the metal using either the nitrogen end or the
terminal chalcogen donor atom. 29,30
to 10 (ca. 70%) (d [ 2.42, d [ 15.95, J 17.0 Hz) is Ñanked
A
M
2
AM
(ca. 20%) by a second AM spin system (10º) with similar
chemical shifts and coupling constants (d 0.07, d [ 15.58,
A
M
J
17.1 Hz). On heating a sample of this mixture at 60 ¡C for
AM
3 days 10º transforms completely and irreversibly in 10. A
slower transformation converting 10º into 10 takes place also
at room temperature. Although a deÐnitive structural assign-
ment of this minor component is not possible on the basis of
the 31PM1HN NMR data only, we hypothesize that it corre-
sponds to the N-bound isomer [(triphos)Re(CO) (g1-N-
NCS)], (10º), which is formed together with 10 when 3 is
P
(PPN)N3
CO
CO
P
P
Re
N3
8
excess or 1:1
(1 equiv)
3
3
2
reacted with ammonium thiocyanate. On increasing the tem-
perature or even on prolonged standing at room temperature,
10º transforms into the more stable isomer 10. Opposite con-
version (from the S-bound to the N-bound isomer) has also
been reported.33
P
OC CO
Re
P
(PPN)N3
1: 0.5
9
Re
N3 P
OC CO
P
P
P
A similar behaviour is observed when studying the reaction
of 3 with KSeCN, which at room temperature gives a mixture
Scheme 5
of two octahedral complexes, [(triphos)Re(CO) (g1-Se-SeCN)]
2
(11) and [(triphos)Re(CO) (g1-N-NCSe)] (11@), in an approx-
2
imate 1 : 1 ratio. On standing at room temperature, the trans-
formation of 11º in 11 is faster than the analogous
transformation of 10º into 10. At reÑux temperature in THF,
the isomerization of 11º into 11 occurs within 1 d.
During the analysis of the 31PM1HN NMR experiments with
NH SCN (or KSeCN), a new complex 12 (or 13) featuring two
4
2
AM sets of equal intensity appears in the spectrum (O10%)
together with the isomeric mixture of 10 and 10º (or 11 and
11@). Noticeably, these minor components do not transform
into any of the isomeric products after prolonged standing at
room temperature or after 3 days heating to 60 ¡C. In con-
trast, addition of a second equivalent of 3 to a solution of 10
and 10º (or 11 and 11@) readily converts this mixture into 12
(or 13), which becomes the only rhenium-containing product.
Scheme 6
210
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Thus, we attribute to 12 and 13 the dinuclear formula
S(Me)(CN)N](OTf
(16)
and
[(triphos)Re(CO) Mg1-Se-
2
[M(triphos)Re(CO) N (l-g1-X,g1-N-XCN)]OTf (X \ S, 12; Se,
Se(Me)(CN)N]OTf (17) are obtained in very good yields,
(Scheme 7). Compounds 16 and 17 are air-stable in the solid
state and do not decompose in solutions of chlorocarbons
within a week. The existence of an g1-S- or g1-Se-co-ordi-
nated S(Me)(CN) or Se(Me)(CN) ligand in 16 and 17, respec-
tively, was conÐrmed by the observation in the 1H NMR
spectrum of 17 of a couple of broad selenium satellites Ñank-
ing the methyl resonance at 2.28 ppm (Fig. 1). The magnitude
2 2
13). Compounds 12 and 13 may be quantitatively prepared by
reacting 3 with half an equivalent of the appropriate thio- or
selenocyanate. Their IR spectra show the typical bands of the
bridging chalcogenocyanate ligands at 2140 (12) and 2142 (13)
cm~1.29b
Reaction of 3 with NaOCN
of the 2J coupling constant (13.1 Hz), which is in the range
HSe
On replacing the thio- or selenocyanate salt with sodium
cyanate in the above procedure a 7 : 3 mixture of the two
reported for organic selenide complexes,35 is clear-cut proof
for the occurrence of the regioselective alkylation of the chal-
cogen rather than the nitrogen atom of the chalcogenocyanate
ligand. A similar regioselectivity is assigned to the sulfur deriv-
ative 16 on the basis of the very similar NMR and IR proper-
ties.
linkage isomers, [(triphos)Re(CO) (g1-N-NCO)] (14) and
2
[(triphos)Re(CO) (g1-O-OCN)] (14º) is obtained. No attempts
2
were made to separate the two isomers. The formation of two
mononuclear cyanate complexes was inferred by IR and
NMR spectroscopy29b (see Table 1). However, we were unable
to assign the di†erent signals to each of the two isomers.
Noticeably, no evidence for the formation of dinuclear com-
pounds was obtained by monitoring (31P NMR spectroscopy)
the reaction between 3 and NaCNO, even when di†erent
ratios of the reagents were used.
When the selenocyanate complex 11 is treated with MeOTf
at low temperature [31PM1HN NMR spectroscopy ([30 ¡C)]
two di†erent products (17, 70%; 18, 30%) are formed, (Scheme
8). Heating the sample at room temperature converts the
minor product 18 into 17, which, within one hour, becomes
the only detectable rhenium phosphine complex. This obser-
vation indicates that at low temperature the reaction is
kinetically controlled and there is no selectivity in driving the
Electrophilic alkylation of the pseudohalide complexes with
MeOTf
Terminal pseudohalide ligands like cyanide, cyanate and chal-
cogenocyanate complexes exhibit a residual electron density
on the exposed nitrogen and are potentially capable of react-
ing with di†erent electrophiles to produce the corresponding
isocyanide, isocyanate or isochalcogenocyanate metal com-
plexes, respectively. Such a reaction is well-documented for
terminal cyanide complexes, which, upon electrophilic attack
on the nitrogen end, give metal-stabilized alkylisocyanide
ligands.34 In contrast, this reactivity has been scarcely con-
sidered for the cognate cyanate and chalcogenocyanate com-
plexes, which would transform into the elusive isocyanate or
isochalcogenocyanate metal complexes. On the other hand,
the electrophilic attack could occur also on the rhenium-co-
ordinated sulfur or selenium atom to yield an S- or Se-bound
alkylcyanide species.
Thus, we decided brieÑy to investigate the electrophilic
methylation of the cyanide complex 6 and to extend these
studies to the related chalcogenocyanate and cyanate com-
plexes 10, 11 and 14/14º, respectively. Compound 6 reacts with
a slight excess of MeOTf to give air-stable yellow micro-
crystals of [(triphos)Re(CO) (CNCH )]OTf (15), (Scheme 7).
2
3
The IR spectrum contains a medium intensity absorption at
2184 cm~1 in the region expected for metal isonitriles. The
31P and 1H NMR spectra are consistent with the presence of
the methyl isocyanide complex. Particularly, the proton NMR
spectrum contains a singlet at 3.06 ppm assigned to the three
protons of the methyl isocyanide ligand.
A di†erent regioselectivity takes place with repeating the
same reaction with the thiocyanate complex 10 and the sele-
nocyanate derivative 11. After addition of MeOTf and usual
work-up, orange to pale yellow microcrystals of the new
Fig. 1 1H NMR (200.13 MHz, CD Cl , 25 ¡C, TMS reference) spec-
2
2
trum of 17 in the aliphatic region showing the SeCH resonance with
3
the satellites due to HÈ77Se coupling.
methylchalcogenocyanate complexes [(triphos)Re(CO) Mg1-S-
2
P
P
P
P
MeOTf
Re
CNMe
Re
P
P
CN
OC CO
OC CO
15
6
P
P
P
P
CN
Me
MeOTf
Re
Re
P
P
XCN
X
OC CO
OC CO
X = S, 10; Se, 11
X = S, 16; Se, 17
Scheme 7
Scheme 8
New J. Chem., 1999, 207È217
211

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electrophilic attack, which then proceeds on both the selenium
and the nitrogen ends. As a result the two isomers, 17 and the
isomethylselenocyanate complex [(triphos)Re(CO) (g1-Se-
2
SeCNMe)]OTf (18), are formed. On increasing the tem-
perature, the reaction becomes thermodynamically controlled
and the less favoured isomer 18 is completely transformed
into the methylselenocyanate complex 17, which is indeÐnitely
stable at room temperature in dichloromethane solution.
Noticeably, on lowering the temperature down to [30 ¡C, the
equilibrium is not restored, thus indicating the irreversibility
of the transformation of 18 into 17.
We have attempted also to study the alkylation reaction of
the azide complex 8 as well as of the mixture of the cyanate
and isocyanate complexes 14 and 14º. However, the only
product that has been recovered from these reactions is the
triÑate complex 3.
Electrochemical properties
All of the monomeric compounds 1, 2, 4, 5, 8È11 and 14 show
a single oxidation process (see Table 2) in the range 0.59È0.80
V generally reversible on the CV timescale, with the noticeable
Fig. 2 Cyclic voltammogram of (a) a 4.6 ] 10~4 M solution of 1 and
(b) a 10.8 ] 10~4 M solution of 2 in CH Cl È0.2 M NBu PF . Scan
exception of [(triphos)Re(CO) (H)]. Controlled potential cou-
2
2
2
4
6
lometry proves the monoelectronic nature of such redox
rate 0.2 V s~1.
changes. This is ascribable to the ReII/ReI couple and is fol-
lowed always by chemical complications. No evidence has
been found for the presence of the ReI/Re0 and the ReIII/ReII
couples, this last being possibly covered by the irreversible
oxidation of the ancillary triphos ligand (1.5 V).
E¡@ \ ]0.73 V for 4).
IR spectroscopy monitoring (see Table 2) of the electro-
chemical process allows us to examine the products formed
upon oxidation of the ReI complexes, following the progres-
sive disappearance of the original m(CO) bands associated
with the appearance of a new unique higher energy band (at
2140 cm~1 for 2 and at 2030 cm~1 for 4).36 In contrast, the
new redox system that appears upon exhaustive oxidation of 5
is cathodically shifted (E¡@ \ ]0.51 V vs. E¡@ \ ]0.67 V). In
all cases the colourless solutions turn deep violet, this being an
almost general feature accompanying the exhaustive oxidation
of the examined complexes.
Halide complexes and the hydride analogue. Fig. 2 shows
the cyclic voltammogramms in dichloromethane (0.2 M
NBu PF ) of [(triphos)Re(CO) (H)] and [(triphos)Re(CO) -
4
6
2
2
(Cl)]. The latter is typical for the general behaviour of the
halide compounds.
The rhenium hydride complex, [(triphos)Re(CO) (H)],
2
undergoes an irreversible oxidation process at E \ ]0.60 V,
followed by chemical reactions that give rise to a new
reversible redox system (E¡@ \ ]0.69 V). Scan rates as high as
5000 mV s~1 are necessary to prevent the formation of this
new species and to observe the directly associated cathodic
Pseudohalide complexes [(triphos)Re(CO) (XCN)] [X = S,
2
(10); Se, (11)]. The redox proÐle of these complexes is also
characterized by the presence of a single oxidation process
encompassing the ReII/ReI couple. The Se complex 11 di†ers
from the sulfur analogue 10 in that the redox change
response
[(triphos)Re(CO) (H)]` ] [(triphos)Re(CO) (H)].
2
2
On the contrary, for compounds 2, 4 and 5 the same anodic
process is both electrochemically and chemically reversible on
the CV timescale, as demonstrated by the constant value of
i /i B 1 as well as by the linear plot of i vs. the square root
11 Ç 11` is not fully reversible and the i /i current ratio
pc pa
does not reach a value of unity even at scan rates higher than
5 V s~1. Moreover, the shape of the anodic peak appears
slightly rounded, suggesting the possible presence of the two
pc pa
pa
of the scan rate. Nevertheless, exhaustive oxidation (E \ ]1
w
V) reveals that the electrogenerated ReII cation complexes,
proposed isomers [(triphos)Re(CO) (g1-Se-SeCN)] (11) and
2
[(triphos)Re(CO) (g1-N-NCSe)] (11@). Such a feature is not
2
[(triphos)Re(CO) (X)]`, are unstable and undergo a chemical
2
rearrangement resulting in new redox systems featuring elec-
better resolved in the DPV (di†erential pulse voltammogram)
trochemical reversibility. In the case of 2 and 4, the potential
of the electrogenerated species is anodically shifted
(E¡@ \ ]0.77 V vs. E¡@ \ ]0.75 V for 2 and E¡@ \ ]0.80 V vs.
proÐle, which also maintains a rounded shape. On the con-
trary, both 10 and 14 display well-shaped peaks and the redox
change is reversible on the CV timescale. Nevertheless, as the
Table 2 Electrochemical properties for selected complexes
[(triphos)Re(CO) (X)]
2
X
E¡@/V
*E a/mV
i
/i
a
IR m
/cm~1
IR m /cm~1
Initial colour
Final colour
p
pc pa
initial
final
1
H
Cl
Br
I
0.60b
0.75
0.73
0.67
0.59
0.79
0.76
0.69
0.73
È
68
71
77
65
67
72
79
70
È
È
È
2140
2030
È
1990, 1930
1990, 1930, 1725
È
È
È
Colourless
Pale yellow
Pale yellow
Pale yellow
Pale yellow
Yellow
Purple
Pale green
Pale yellow
Violet
Violet
Violet
Violet
Violet
Violet
Violet
Violetd
Violete
2
0.97
0.98
0.98
0.88
0.47
0.92
0.36
0.91
2050, 1960
1980, 1915
È
2050, 1970, 1900, 1615
2080, 1990, 1970, 1925
È
2100, 1980, 1920
2240, 1975, 1910
4
5
8
N
3
9c
k-N
3
10
SCN
11
SeCN
OCN
14/14ºe
a At 0.2 V s~1. b Registered at 5.0 V s~1. c [M(triphos)Re(CO) N (l-N )]. d Turns golden yellow on standing. e Mixture of linkage isomers.
2 2
3
212
New J. Chem., 1999, 207È217

View Article Online
utility of this compound as a synthon of the highly stable
rhenium(I) fragment [(triphos)Re(CO) ]` is exempliÐed by the
2
synthesis of a variety of mononuclear and binuclear halide
and pseudohalide complexes. Among the new complexes are
the Ðrst dirhenium(I) species featuring bridging azido, thio-
and selenocyanate ligands. Regioselective alkylation of the
chalcogenocyanate derivatives a†ords unprecedented exam-
ples of methylsulÐde- and methylselenide-cyanide rhenium
complexes. Studies are in progress to deÐne the synthetic
scope of the electrophilic alkylation of 10 and 11 better and to
verify if the unusual S(Me)(CN) and Se(Me)(CN) ligands may
be removed from the co-ordination sphere of the metal and
used in organic and organometallic synthesis.
Experimental
Materials and methods
All reactions and manipulations were routinely performed
under a dry nitrogen atmosphere by using standard Schlenk
techniques. Tetrahydrofuran (THF) was freshly distilled over
LiAlH before use; n-hexane was stored over molecular sieves
and purged with nitrogen prior to use. All other reagents and
chemicals were commercial products and were used as
Fig. 3 (a) Overlapped cyclic voltammograms of 8 (1.2 ] 10~3 M,
dotted line) and 9 (7.0 ] 10~4 M, full line). Scan rate 0.2 V s~1. (b)
Di†erential pulse voltammogram of 9 (7.0 ] 10~4 M). Solutions are in
CH Cl È0.2 M NBu PF . Scan rate 0.004 V s~1.
4
received without further puriÐcation; [(triphos)Re(CO) (Cl)]
2
2
4
6
2
(2) was prepared as previously reported.1a
IR spectra were obtained in KBr using a Nicolet 510 P
FT-IR (4000È200 cm~1) spectrophotometer. Deuteriated sol-
vents for NMR measurements (Aldrich and Merck) were dried
over molecular sieves (4 Ó). Proton NMR spectra were
recorded on Bruker AC200 or Varian VXR300 instruments
operating at 200.13 and 299.94 MHz, respectively. Peak posi-
tions are relative to tetramethylsilane (TMS) as an external
reference or were calibrated with respect to the residual pro-
tiated solvent. 31PM1HN NMR spectra were recorded at 81.01
and 121.42 MHz, on the same instruments, respectively.
Chemical shifts are relative to external 85% H PO with
congener 11 does, they rearrange upon exhaustive oxidation
(E \ ]1 V) to give rise to a new derivative, which in both
w
cases undergoes a reversible process at E¡@ \ ]0.70 V. The
progress of the chemical reaction that follows the exhaustive
oxidation was monitored by the disappearance of the IR
m(CO) bands.
Azide
complexes
2 2
[(triphos)Re(CO) (N )]
(8)
and
2
3
[{(triphos)Re(CO) } (l-N )]OTf (9). The redox behaviour of
3
complexes 8 and 9 is similar to that of the above discussed
compounds. In Fig. 3(a) the cyclic voltammetric proÐles of 8
and 9 are superimposed in order to better appreciate the con-
siderable anodic shift on passing from the monomeric to the
dimeric species. This latter complex also exhibits a single oxi-
dation peak, which is assigned to the simultaneous and inde-
pendent ReII/ReI redox change of both metal sites.
3
4
downÐeld values reported as positive. 13CM1HN and 19FM1HN
NMR spectra were recorded on the Bruker AC200P instru-
ment at 50.32 MHz and 188.3 MHz, respectively. The chemi-
cal shifts are relative to TMS for 13CM1HN and to external
CFCl for 19FM1HN NMR.
3
The spin-lattice relaxation time (T ) on the cyanide binu-
1
Inspection of the DPV proÐle [Fig. 3(b)] indicates that the
two oxidation peaks are not exactly coincident, nevertheless
the potential separation is so small that the peaks cannot be
clearly distinguished. Therefore, in spite of the highly conju-
clear complex 7 was measured in dichloromethane at 300
MHz by the inversion-recovery method using the standard
180¡ÈsÈ90¡ pulse sequence. The calculations of the relaxation
times were made using the Ðtting routine of the Varian
VXR300 spectrometer. The 90 degree pulse on the sample of 7
gated pathway o†ered by the N bridging group, electro-
3
chemical data indicate the presence of an extremely weak
was carefully measured before running the T measurements.
1
metalÈmetal interaction. In both cases the exhaustive oxida-
tion is followed by a rearrangement of the electrogenerated
cations: the original colourless solutions turn violet and then
golden yellow. No redox active species is obtained upon such
a decomposition. IR monitoring of the redox process shows
The computer simulation of the 13CM1HN NMR spectra was
carried out with a locally developed package containing the
programs LAOCN338 and DAVINS.39 The initial choices of
shifts and coupling constants were reÐned by iterative least-
squares calculations using the experimental digitized spec-
trum. The Ðnal parameters gave a satisfactory Ðt between
experimental and calculated spectra, the agreement factor
being less than 1% in all cases.
the complete disappearance of both the m(CO) and the m(N )
3
signals for 8 and 9 together with the growing in of a strong
signal at 1725 cm~1 for 9.
A rationale for this behaviour could be found in the cleav-
age of one (or even two) RewCO bond(s) after the metal-
centred oxidation. Indeed, the ReI ] ReII oxidation process
Molar conductivities were measured with an AMEL model
134 conductance cell connected with a model 101 conductivity
meter. The conductivity data were obtained at sample concen-
trations of 10~3 M in nitroethane solutions at room tem-
perature (22 ¡C). Elemental analyses (C, H, N, S) were
performed using a Carlo Erba model 1106 elemental analyser.
Mass spectra were recorded on a Hewlett Packard MS Engine
HP 5989A. For the FAB measurements, xenon was used as
the primary beam gas. The ion gun was operated at 8 kV and
10 lA (probe temperature 50 ¡C); nitrobenzyl alcohol was
used as the matrix. Materials and apparatus for electrochem-
istry have been described elsewhere.40 Voltammetric (cyclic
and di†erential pulse) and coulometric techniques coupled
removes electrons from the t metal orbitals involved in the
2g
back-donation mechanism with the CO ligands and therefore
decreases the RewCO bond order. A similar behaviour has
been previously observed for analogous octahedral ReI species
stabilized by n-back-bonding interactions.37
Conclusions
A number of new synthetic procedures for preparing the tri-
Ñate complex [(triphos)Re(CO) (OTf)] (3) are described. The
2
New J. Chem., 1999, 207È217
213

View Article Online
with IR spectroscopy have been used to characterize both the
redox behaviour and the stability of the electrogenerated
species. All of the measurements were done at a platinum elec-
trode in dichloromethane using NBu PF (0.2 M) as the sup-
The extracts were concentrated to half their volume and 5 mL
of n-hexane was added to give white microcrystals, which were
collected by Ðltration, washed with diethyl ether and dried
under reduced pressure. Yield 73%. Anal. found: C, 53.98; H,
4
6
porting electrolyte. The potentials are referred to SCE.
4.08. Calcd for C
H
BrO P Re: C, 54.55; H, 4.15%. IR:
43 39
2 3
m(CO) 1950, 1889 cm~1. 31PM1HN NMR (295 K, CD Cl ):
2
2
AM spin system, d 2.15, d [ 20.14, J 14.6 Hz. 1H NMR
AM
(295 K, CD Cl ): 1.42 (q, J 2.4 Hz, CH , 3H), 2.42 (m, CH ,
HP
Synthesis of [(triphos)Re(CO) (OTf)] (3)
2
A
M
2
2
2
3
2
Method 1. A Schlenk tube was charged with 2 (2.0 g, 2.21
mmol) and dichloromethane (15 mL). The resulting solution
was cooled to [10 ¡C with an iceÈsalt bath and stirred under
6H).
[(triphos)Re(CO) (I)] (5). The iodide derivative was pre-
2
N before adding an excess of MeOTf (377 lL, 3.32 mmol) via
pared as described above by replacing KBr with KI (157.7 mg,
2
a microsyringe. The starting material dissolved in a few
0.95 mmol). Complex 5 was isolated as a pale yellow product
in ca. 90% yield. Anal. found. C, 51.86; H, 4.00. Calcd for
minutes to give a clear yellow solution. The cooling bath was
removed and the solution was stirred at room temperature for
15 min. The reaction mixture was concentrated to ca. 6 mL
under vacuum. Addition of diethyl ether (5 mL) precipitated a
pale yellow powder, which was Ðltered o†, washed with
diethyl ether (2 ] 3 mL) and dried under vacuum. Yield 95%.
C
H
IO P Re: C, 51.97; H, 3.96%. IR: m(CO) 1950, 1892
43 39 2 3
cm~1. 31PM1HN NMR (295 K, CD Cl ): AM spin system, d
2
2
2
A
[ 0.12, d [ 24.7, J 15.2 Hz. 1H NMR (295 K, CD Cl ):
AM
1.40 (q, J 2.5 Hz, CH , 3H), 2.22 (m, CH , 6H).
HP
M
2 2
3
2
Attempted synthesis of [(triphos)Re(CO) (F)]. No reaction
2
was observed when 3 and di†erent sources of Ñuoride ion
Method 2. To a solution of 2 (200.0 mg, 0.22 mmol) in
dichloromethane (10 mL) was added 1.1 equiv. of AgOTf (70.0
mg, 0.27 mmol). The mixture was stirred for 1 h and then
silver chloride was removed by Ðltering the grey suspension
through Celite, which was then washed with dichloromethane
(2 ] 3 mL). The combined Ðltrate and washings were evapo-
rated to dryness under vacuum. The solid residue was
extracted with 5 mL of dichloromethane. Concentration of the
resulting yellow solution and addition of n-hexane (3 mL)
gave a pale yellow product, which was Ðltered o†, washed
with diethyl ether (2 ] 3 mL) and dried under vacuum. Yield
85%.
[NaF, KF or (PPN)F] were allowed to react under the reac-
tion conditions reported above.
Synthesis of the pseudohalide complexes
[(triphos)Re(CO) (CN)] (6). To a stirred suspension of 3
2
(200.0 mg, 0.19 mmol) in 20 mL of THF at room temperature,
a Ðve-fold excess of tetrabutylammonium cyanide (264.4 mg,
0.95 mmol) was added. The starting material dissolved within
a few minutes to give a clear yellow solution. After 1 h stirring,
the volume was reduced to ca. 5 mL. Slow addition of n-
hexane (5 mL) gives a yellow precipitate, which was collected
by Ðltration, washed with diethyl ether and dried under
reduced pressure. Yield 75%. Anal. found: C, 59.10; H, 4.38;
Method 3. A slight excess of HOTf (6 lL, ca. 6.6 ] 10~2
mmol) was added via syringe to a solution of 2 (50 mg,
N, 1.51. Calcd for C
H
NO P Re: C, 59.18; H, 4.40; N,
44 39
2 3
5.5 ] 10~2 mmol) in dichloromethane-d (1.0 mL) in a 5 mm
1.56%. IR: m(CN) 2106, m(CO) 1946, 1890 cm~1. 31PM1HN
2
NMR tube. 31PM1HN and 1H NMR spectroscopy showed the
NMR (295 K, CD Cl ): AM spin system, d [ 5.90, d
2
2
2
A
M
quantitative formation of 3.
[ 17.88, J 18.4 Hz. 1H NMR (295 K, CDCl ): 1.46 (br s,
AM
3
CH , 3H), 2.40 (m, CH , 6H). 13CM1HN NMR (295 K, CDCl ):
3
2
3
Method 4. HOTf (56 lL, 0.63 mmol) was added under nitro-
d 195.0 (m, CO), 131.4 (d, 2J
10.9 Hz, CN), 40.2 (q, J
CP trans
CP
gen to a stirred suspension of [(triphos)Re(CO) (H)] (1) (500.0
9.9 Hz, CH C), 39.2 (q, J 3.3 Hz, CH C), 35.2 (m, CH P ),
2
3
33.3 (m, CH P ).
2 eq
CP
3
2 ax
mg, 0.57 mmol) in dichloromethane (15 mL) cooled to
[10 ¡C. Stirring was continued for 5 min during which time
all the monohydride dissolved to produce a pale yellow solu-
tion, which was slowly brought to room temperature. After
1 h stirring, addition of n-hexane (10 mL) yielded 3 as a pale
yellow product. Monitoring the reaction by 1H and 31P NMR
spectroscopy showed that the formation of 3 is at the
[{(triphos)Re(CO) } (l-CN)]OTf (7). Method 1. The binu-
2 2
clear complex 7 was prepared, in almost quantitative yield,
from the reaction of the monomeric complex 6 (100.0 mg, 0.11
mmol) with 1 equiv. of 3 (113.7 mg) in dichloromethane (5
mL) at room temperature. The resulting solution was stirred
for 15 min during which time the originally pale yellow solu-
tion turned colourless. Addition of 5 mL of n-hexane caused
the precipitation of 7 as white microcrystals. These were col-
lected by Ðltration and washed with n-hexane and diethyl
ether before being dried under nitrogen. Yield 90%.
beginning
accompanied
by
the
agostic
complex
[(triphos)Re(CO) ]OTf.1a This completely transformed into 3
2
over 1 h. Anal. found: C, 52.00; H, 3.90; S, 3.12. Calcd for
C
H
F O P SRe: C, 52.02; H, 3.87; S, 3.16%. IR: m(CO)
44 39 3 5 3
1967, 1902; m(g1-OSO CF ) 1320 cm~1. 31PM1HN NMR (295
2
3
Method 2. Compound 7 was obtained also by treating a
K, CD Cl ): AM spin system, d 6.20, d [ 10.11; J 14.7
AM
Hz. 1H NMR (295 K, CD Cl ): 1.54 (br s, CH , 3H), 2.55 (m,
2
2
2
A
M
suspension of 3 (200.0 mg, 0.19 mmol) in THF (20 mL) with
2
2
3
0.5 equiv of [Bu N]CN (25.5 mg). Yield ca. 80%. Anal. found:
CH , 6H). 19F NMR (295 K, CD Cl ): [77.55 (s, g1-
4
2
2 2
2 2
C, 55.70; H, 4.15; N, 0.74; S, 1.70. Calcd for C
H
F -
OSO CF ). 13CM1HN NMR (295 K, CD Cl ): d 197.5 (AXX@Y
88 78 3
2
3
NO P Re S: C, 55.37; H, 4.12; N, 0.73; S, 1.68%. IR: m(CN)
spin system, J 52.8, J [ 8.2, J 6.6, J
AX AX{ AY
39.9 (q, J 9.9 Hz, CH C), 39.4 (q, J 3.3 Hz, CH C), 37.9
26.5 Hz, CO);
7 6
2
XX{
2097; m(CO) 1967, 1908; m(OTf~) 1275 cm~1. 31PM1HN NMR
CP
28.0, J
3
CP
2 ax
2 eq
3
(295 K, CD Cl ): AA@M M@ spin system, d 0.21, d [ 7.41,
(dt, J
] J
4.0 Hz, CH P ), 33.7 [td, N \ (J
5.1 Hz, CH P ].
2
2
2
2
A
A{
CPax
) 15.7, J
CPeq
CPeq{
d [ 17.12, d [ 17.66, J
M{
16.3, J
19.5, J \ J
\
M
AM
A{M{
AA{
MM{
CPax_
CPax
J
\ J
0 Hz. 1H NMR (295 K, CD Cl ): 1.49 (q, J 2.4
A{M
AM{
2
2
HP
Hz, CH , 3H), 1.56 (s, CH , 3H), 2.6È2.2 (m, CH , 12H).
Synthesis of the halide complexes
3
3
2
"
\ 43.3 )~1 cm2 mol~1. FAB`-MS: m/z 1760
(M`), 893 [(triphos)Re(CO) CN]`, 867 [(triphos)Re(CO) ]`,
839 [(triphos)Re(CO)]`.
M(nitroethane)
[(triphos)Re(CO) (Br)] (4). An excess of KBr (117.2 mg,
2
2
2
0.98 mmol) was added at room temperature under vigorous
stirring to a suspension of 3 (200.0 mg, 0.19 mmol) in 20 mL of
THF. The mixture was stirred for 18 h, the solvent was
removed under reduced pressure and the resulting yellow solid
was extracted with two 5 mL portions of dichloromethane.
[{(triphos)Re(CO) } (l-CN)]BPh (7-BPh ). A solution of
2 2
4
4
NaBPh (26.9 mg, 7.8 ] 10~2 mmol) in methanol (5 mL) was
4
added to 7 (100.0 mg, 5.2 ] 10~2 mmol) dissolved in dichloro-
214
New J. Chem., 1999, 207È217

View Article Online
methane (5 mL). After 30 min stirring, the white solid formed
was collected on a Ðlter, washed with methanol and diethyl
ether and dried under vacuum. Anal. found: C, 64.20; H, 4.80;
Calcd for C
H
NO P ReS: C, 57.13; H, 4.25; N, 1.51; S,
44 39
2 3
3.47%. IR: m(SCN) 2106; m(CO) 1956, 1900 cm~1. 31PM1HN
NMR (295 K, CD Cl ): AM spin system, d [ 2.42, d
2
2
2
A
M
N, 0.71. Calcd for C
0.67%. The IR spectrum showed the characteristic band at
H
BNO P Re : C, 64.13; H, 4.75; N,
[ 15.95, J 17.0 Hz. 1H NMR (295 K, CD Cl ): 1.53 (q, J
111 98
4 6
2
AM
2
2
HP
2.4 Hz, CH , 3H), 2.53 (m, CH , 6H). 13CM1HN NMR (295 K,
3
2
610 cm~1 due to m(BPh ).
CD Cl ): d 197.4 (m, CO), 124.5 (br s, SCN), 41.4 (q, J 10.1
4
2 2
CP
Hz, CH C), 41.0 (q, J 3.8 Hz, CH C), 37.0 (dt, J
26.9,
3
CP
3
CPax
[(triphos)Re(CO) (N )] (8). An excess of (PPN)N (341.2
J
J
3.0 Hz, CH P ), 35.7 [td, N \ (J
5.5 Hz, CH P ]. FAB`-MS: m/z 925 (M`), 867
[(triphos)Re(CO) ]`, 839 [(triphos)Re(CO)]`.
] J ) 14.3;
2
3
3
CPeq
CPax
2 ax
2 eq
CPeq{
CPax_
mg, 0.57 mmol) was added to a stirred dichloromethane (5
mL) solution of 3 (200 mg, 0.19 mmol). An immediate colour
change from yellow to deep red was observed while stirring
was continued additionally for 15 min. Addition of diethyl
ether (5 mL) gave 8 as yellow microcrystals. The compound
was collected on a sintered glass frit, washed with diethyl
ether and dried under vacuum. Yield 75%. Anal. found: C,
2
Monitoring the reaction of NH SCN with 3 by 31P{1H}
4
NMR spectroscopy. 31PM1HN NMR monitoring of the reaction
between 3 (30.0 mg, 2.9 ] 10~2 mmol) and one equivalent of
NH SCN (2.2 mg, 2.9 ] 10~2 mmol) in a 5 mm NMR tube
4
56.80; H, 4.30; N, 4.59. Calcd for C
H
N O P Re: C,
(1.0 mL of THF-d ) showed that the formation of 10 (ca. 70%)
43 39
3
2 3
8
56.82; H, 4.32; N, 4.62%. IR: m (N ) 2044; m(CO) 1936, 1879;
is accompanied by two new sets of resonances ascribable to
as
3
m
(N ) 1334 cm~1. 31PM1HN NMR (295 K, CD Cl ): AM
sym
spin system, d 1.07, d [ 15.07, J 14.9 Hz. 1H NMR (295
AM
K, CD Cl ): 1.48 (br s, CH , 3H), 2.48 (m, CH , 6H).
the N-bonded thiocyanate isomer, 10º (ca. 20%), and to the
dinuclear complex 12 (ca. 10%, see below for the NMR
characterization), respectively. On heating the NMR tube at
60 ¡C, the transformation of 10º into 10 was completed in 3
days. 31PM1HN NMR (295 K, THF-d ) of 10º : AM spin
3
2
2
2
A
M
2
2
3
2
Monitoring the reaction of 3 with PPN(N ) by 31P{1H}
3
8 2
17.1 Hz. On concentrating
NMR spectroscopy. Monitoring the reaction between 3 (30
system, d 0.07, d [ 15.58; J
A
M
AM
mg, 2.9 ] 10~2 mmol) and a stoichiometric amount of
the NMR tube solution to dryness, a purple powder was
obtained, which in the IR spectrum exhibited a sharp band at
2077 cm~1 assignable to m(NCS) in the N-bonded isomer 10º.
(PPN)N (17.6 mg, 2.9 ] 10~2 mmol) in a 5 mm NMR tube
3
(1.0 mL of dichloromethane-d ) by 31P NMR spectroscopy
2
showed that 8 is formed together with the binuclear derivative
9 (ca. 10 : 1 ratio). The composition of the mixture does not
[{(triphos)Re(CO) } (l-g1-S,g1-N-SCN)]OTf (12). Method
2 2
change over a week and is temperature invariant.
1. To a stirred solution of 3 (200.0 mg, 0.19 mmol) in THF (20
mL), 0.5 equivalent of solid NH SCN (7.2 mg, 0.095 mmol)
4
[{(triphos)Re(CO) } (l-N )]OTf (9). The dinuclear
was added. The initial yellow colour immediately disappeared
2 2
3
complex 9 was obtained as white microcrystals by combining
to produce a deep purple solution, which was stirred for 1 h.
Concentration of the solution under nitrogen and addition of
diethyl ether (5 mL) gave purple microcrystals of 12, which
were Ðltered o† and washed with diethyl ether before being
dried under nitrogen. Yield 85%.
3 (200.0 mg, 0.19 mmol) with 0.5 equiv of (PPN)N (55.1 mg)
3
in dichloromethane (10 mL) at room temperature. The colour
of the solution immediately became deep red, but in a few
minutes turned to deep yellow. After 30 min stirring the solu-
tion was evaporated under nitrogen to ca. 5 mL. Addition of
diethyl ether (5 mL) gave 9. Yield 77%. Anal. found: C, 54.30;
Method 2. One equivalent of 3 (109.8 mg, 0.10 mmol) was
added under vigorous stirring to a dichloromethane solution
(5 mL) of 10 (100.0 mg, 0.10 mmol). After 1 h stirring, concen-
tration under nitrogen and addition of n-hexane (10 mL) gave
purple microcrystals of 12. Yield 75%. Anal. found: C, 54.55;
H, 4.00; N, 2.17; S, 1.64. Calcd for C
54.29; H, 4.08; N, 2.18; S, 1.67%. IR: m(N ) 2122; m(CO) 1952,
H F N O P Re S: C,
87 78 3
3
7 6
2
3
1894; m(OTf) 1272 cm~1. 31PM1HN NMR (295 K, CD Cl ):
2
2
(AM ) spin systems, d 0.75, d [ 11.96, J
16.3 Hz. 1H
2 2
A
M
AM
NMR (295 K, CD Cl ): 1.51 (br s, CH , 6H), 2.50 (m, CH ,
H, 4.06; N, 0.75; S, 3.28. Calcd for C H F NO P Re S : C,
2
2
3
2
88 78 3
7 6 2 2
12H).
"
\ 57.4 )~1 cm2 mol~1. FAB`-MS:
54.46; H, 4.05; N, 0.72; S, 3.30%. IR: m(SCN) 2140; m(CO)
1958, 1900; m(OTf) 1273 cm~1. 31PM1HN NMR (295 K,
CD Cl ): AA@M M@ spin systems, d [ 2.13, d [ 2.52, d
M(nitroethane)
m/z 1775 (M`), 909 [(triphos)Re(CO) N ]`, 867 [(triphos)-
2
3
Re(CO) ]`, 839 [(triphos)Re(CO)]`.
2
2
2
2
2
A
A{
M
[ 12.90, d [ 14.70; J \ J
18.3, J \ J \ J
\
M{ AM A{M{
AA{ MM{
A{M
[{(triphos)Re(CO) } (l-N )]BPh (9-BPh ). Metathetical
J
0 Hz. 1H NMR (295 K, CD Cl ): 1.72 (br s, CH , 6H),
2 2
3
4
4
AM{
2
2
3
reaction of 9 (100.0 mg, 5.2 ] 10~2 mmol) with an excess of
2.4È2.6 (m, CH , 12H). "
\ 48.5 )~1 cm2 mol~1.
2
M(nitroethane)
NaBPh (26.7 mg, ca. 7.8 ] 10~2 mmol) in dichloromethaneÈ
4
methanol (1 : 1 v/v,
8
mL) gave [M(triphos)Re(CO) N l-
[{(triphos)Re(CO) } (l-g1-S,g1-N-SCN)]BPh (12-BPh ).
2 2 4 4
2 2
N )]BPh as white microcrystals. Yield 90%.
Metathetical reaction of 12 (100.0 mg, 5.1 ] 10~2 mmol) in
3
4
dichloromethane (5 mL) with excess NaBPh (26.4 mg,
4
7.7 ] 10~2 mmol) in ethanol (2 mL) gave 12-BPh in almost
4
Thermal behaviour of [(triphos)Re(CO) (N )] (8) and
2
3
[{(triphos)Re(CO) } (l-N )]OTf (9). On reÑuxing either 8 or
quantitative yield. Anal. found: C, 63.20; H, 4.70; N, 0.64; S,
2 2
3
9 in THF, no reaction took place over a period of 12 h
(31PM1HN NMR monitoring).
1.49. Calcd for C
H
BNO P Re S: C, 63.0.8; H, 4.68; N,
111 98
4 6
2
0.66; S, 1.51%. IR: m(SCN) 2140; m(CO) 1958, 1900; m(BPh )
610 cm~1.
4
[(triphos)Re(CO) (g1-S-SCN)] (10). Solid NH SCN (72
2
4
mg, 0.95 mmol) was added to a stirred suspension of 3 (200
mg, 0.19 mmol) in 20 mL of THF. The resulting mixture,
which immediately turned deep red, was stirred for 4 h and
concentrated to dryness. The crude material was extracted
twice with dichloromethane (2 mL) and Ðltered to remove
excess ammonium thiocyanate. Concentration of the com-
bined extracts and addition of diethyl ether (5 mL) gave a
purple product, which was Ðltered o† and dried under oil
pump vacuum. The crude product was recrystallized from
dichloromethaneÈdiethyl ether to yield purple microcrystals of
10. Yield 85%. Anal. found: C, 57.15; H, 4.23; N, 1.50; S, 3.44.
[(triphos)Re(CO) (g1-Se-SeCN)]
(11). On replacing
2
NH SCN with KSeCN (85 mg, 0.60 mmol) in the preparation
4
of 10, deep green microcrystals of 11 were obtained after usual
work-up. Recrystallization from dichloromethaneÈdiethyl
ether gave 11 in analytically pure form. Yield 75%. Anal.
found: C, 54.25; H, 3.99; N, 1.39. Calcd for
C
H P ReO SeN: C, 54.38; H, 4.04; N, 1.44%. IR:
44 39 3
2
m(SeCN) 2116; m(CO) 1958, 1898 cm~1. 31PM1HN NMR (295
K, CD Cl ): AM spin system, d [ 3.41, d [ 16.18, J 17.4
2
2
2
A
M
HP
AM
3
Hz. 1H NMR (295 K, CD Cl ): 1.50 (q, J 2.3 Hz, CH , 3H),
2
2
2.47 (m, CH , 6H). 13CM1HN NMR (295 K, CD Cl ): d 197.9
2
2 2
New J. Chem., 1999, 207È217
215

View Article Online
(AXX@Y spin system, J 55.6, J [ 8.8, J 7.1, J
AX AX{ AY
Hz, CO), 108.9 (q, J 3.4 Hz, SeCN), 40.1 (q, J 10.0 Hz,
CP CP
CH C), 39.8 (q, J 3.2 Hz, CH C), 35.4 (dt, J 26.3, J
CPeq
4.9
28.5
methane and ethanol (1 : 1 v/v). Yield 90%. Anal. found: C,
XX{
52.20; H, 4.03; N, 1.28; S, 3.01. Calcd for C
H F NO -
46 42 3
5
P ReS: C, 52.27; H, 4.00; N, 1.33; S, 3.03%. IR: m(CN) 2184;
3
CP
3
CPax
) 15.3; J
3
3.1 Hz, CH P ), 34.3 [td, N \ (J
] J
CPax_
m(CO) 1971, 1915; m(OTf) 1269 cm~1. 31PM1HN NMR (295 K,
2 ax
Hz, CH P ].
2 eq
CPeq{
CPax
CD Cl ): AM spin system, d [12.04, d [14.15, J 21.5
2
2
2
A
M
AM
Hz. 1H NMR (295 K, CD Cl ): 1.65 (br q, J 2.9 Hz, CH ,
2 2 HP
3
Monitoring the reaction of KSeCN with 3 by 31P{1H} NMR
spectroscopy. Monitoring the reaction between 3 (40 mg,
3.9 ] 10~2 mmol) and one equivalent of KSeCN (5.7 g,
3H), 2.57 (m, CH , 6H), 3.06 (s, CNCH , 3H).
2
3
[(triphos)Re(CO) {g1-S-S(CH )(CN)} ]OTf (16). On repla-
2
3
3.9 ] 10~2 mmol) in a 5 mm NMR tube (1.0 mL of THF-d )
cing 6 with 10 in the above procedure, 16 was obtained as pale
yellow microcrystals. Yield ca. 90%. Anal. found: C, 50.65; H,
8
as described above for the thiocyanate analogue showed that
the formation of 11 (45%) is accompanied by that of the N-
bonded selenocyanate isomer, 11º (10%), and the dinuclear
compex 13 (45%, see below for the NMR properties). On
heating the NMR tube at 60 ¡C, the transformation of 11º into
3.90; N, 1.28; S, 5.90. Calcd for C
H F NO P ReS : C,
46 42 3
5 3
2
50.73; H, 3.89; N, 1.29; S, 5.89%. IR: m(SCN) 2139; m(CO)
1956, 1900; m(OTf) 1267 cm~1. 31PM1HN NMR (295 K,
CD Cl ): d [5.19, d [10.52, J 19.2 Hz. 1H NMR (295
2
2
A
M
AM
11 was completed in one day. 31PM1HN NMR (295 K, THF-d )
K, CD Cl ): 1.65 (br q, J 2.9 Hz, CH , 3H), 2.8È2.4 (m,
8
2
2
HP
3
of 11º : AM spin system, d [ 0.23, d [ 15.01; J 16.0 Hz.
CH , 6H), 2.30 (s, SCH , 3H).
2
A
M
AM
2
3
On concentrating the NMR tube solution to dryness, a pale
green powder was obtained, which in the IR spectrum exhibits
a sharp band at 2066 cm~1 characteristic of m(NCSe) in the
N-bonded isomer 10º.
[(triphos)Re(CO) {g1-Se-Se(CH )CN)} ]OTf
(17).
On
2
3
replacing 10 with 11 in the above procedure, 17 was obtained
as pale yellow microcrystals. Yield ca. 90%. Anal. found: C,
48.60; H, 3.75; N, 1.26; S, 2.80. Calcd for C
H F NO -
46 42 3
5
[{(triphos)Re(CO) } (l-g1-Se,g1-N-SeCN)]OTf
(13).
P ReSSe: C, 48.64; H, 3.73; N, 1.23; S, 2.82%. IR: m(SeCN)
2 2
3
Bluish violet microcrystals of 13 were isolated following a pro-
cedure identical to that described for 12, using KSeCN (14.2
2183; m(CO) 1956, 1898; m(OTf) 1271 cm~1. 31PM1HN NMR
(295 K, CD Cl): d [4.60, d [9.93, J 19.6 Hz. 1H NMR
2
A
M
AM
mg) instead of NH SCN. The colour of the solution imme-
(295 K, CD Cl ): 1.65 (br q, J 2.9 Hz, CH , 3H), 2.85È2.45
4
2
2
HP
3
diately became deep green, but after a few minutes, turned
(m, CH P , 4H), 2.57 (d, J 10.6, CH P , 2H), 2.28 (s,
2 eq
HP
2 ax
blue. Yield 75%. Anal. found: C, 53.00; H, 3.91; N, 0.68; S,
SeCH , 3H; this signal exhibits 77Se satellites with 2J
\
3
HSe
1.58. Calcd for C
H F NO P Re SSe: C, 53.09; H, 3.95; N,
13.1 Hz).
88 78 3
7 6
2
0.70; S, 1.61%. IR: m(SeCN) 2142; m(CO) 1960, 1900; m(OTf)
1271 cm~1. 31PM1HN NMR (295 K, CD Cl ): AA@M M@ spin
In situ NMR studies
2
2
2 2
systems, d [2.18, d [3.47, d [12.90, d [15.97, J
\
A
A{
18.1, J \ J \ J \ J
AA{ MM{ A{M AM{
CD Cl ): 1.68 (br s, CH , 6H), 2.47 (m, CH , 12H).
M
M{
AM
Reaction of 2 with Me OBF (Scheme 2). A 5 mm NMR
J
0 Hz. 1H NMR (295 K,
3
4
A{M{
tube was charged with 30.0 mg (3.3 ] 10~2 mmol) of 2 in
2
2
3
2
THF-d (0.8 mL). The tube was cooled down to [78 ¡C with
"
\ 67.6 )~1 cm2 mol~1.
8
M(nitroethane)
a liquid nitrogenÈisopropanol bath and Me OBF (10.0 mg,
3
4
6.6 ] 10~2 mmol) in 0.2 mL of THF-d was added with a
syringe. The tube was inserted into the spectrometer cooled to
[{(triphos)Re(CO) } (l-g1-Se,g1-N-Se(CN)]BPh
(13-
8
2 2
4
BPh ). Metathetical reaction of 13 (100.0 mg, 5.0 ] 10~2
4
[60 ¡C and a 31PM1HN NMR spectrum was immediately
recorded. It showed the formation of the agostic cation
mmol) in dichloromethane (5 mL) with excess of NaBPh
4
(25.8 mg, 7.5 ] 10~2 mmol) in ethanol (2 mL) gave the tetra-
complex [(triphos)Re(CO) ]` (80%)1a together with some
phenylborate salt 13-BPh in almost quantitative yield. Anal.
2
4
[(triphos)Re(CO) (g1-O-THF-d )]` (20%); 31PM1HN NMR
found: C, 61.61; H, 4.54; N, 0.62. Calcd for C
H
BNO -
2
8
111 98
4
(295 K, CD Cl ): d 3.76, d [18.88, J 13.73 Hz.11
P Re Se: C, 61.68; H, 4.57; N, 0.65%. IR: m(SeCN) 2142;
m(CO) 1960, 1900; m(BPh ) 610 cm~1.
2
2
A
M
AM
6
2
4
Reaction of 2 with MeOTf (Scheme 2). A 5 mm NMR tube
was charged with the chloride complex 2 (30.0 mg, 3.3 ] 10~2
Preparation of the isomeric mixture [(triphos)Re(CO) (g1-
2
N-NCO)] (14) and [(triphos)Re(CO) (g1-O-NCO)] (14º). A
2
mmol) in CDCl (0.8 mL) and capped with a septum. The
3
tube was immersed in a liquid nitrogen bath and MeOTf (4
suspension of 3 (200.0 mg, 0.19 mmol) in 20 mL of THF was
lL, ca. 3.3 ] 10~2 mmol) was added with a syringe before
inserting the tube into the probe of the NMR spectrometer
precooled to [60 ¡C. The 31PM1HN spectrum showed the for-
treated with a Ðve-fold excess of NaOCN (64.0 g, 1.0 mmol)
and stirred at room temperature for 12 h without any change
of colour. Addition of n-hexane (20 mL) and concentration
under nitrogen yielded a pale yellow precipitate, which was
washed with diethyl ether and dried under vacuum. Yield
70%. The 31PM1HN NMR analysis of the crude product indi-
cates the formation of a mixture of the two complexes 14
(70%) and 14º (30%). Anal. found: C, 58.20; H, 4.35; N, 1.52.
mation of [(triphos)Re(CO) (OTf)] (3) as the only product,
2
while the 1H NMR spectrum featured a singlet at ca. 3.0 ppm
attributed to free CH Cl. On repeating the same in situ NMR
3
experiment with the bromide and the iodide derivatives 4 and
5, stoichiometric formation of CH Br (d 2.68) and CH I (d
3
3
2.15) was observed, respectively.
Calcd for C
H P ReO N: C. 58.14; H, 4.32; N, 1.54%. IR:
44 39 3
3
m (NCO) 2234; m(CO) 1950, 1886 cm~1. 31PM1HN NMR (295
as
K, CD Cl ): 14, AM spin system, d 1.79, d [16.42, J
Reaction of 11 with MeOTf. A 5 mm NMR tube was
charged with the selenocyanate complex 11 (25 mg,
2
2
2
A
M
AM
15.3 Hz; 14º, AM spin system, d 3.75, d [18.94, J 13.7
2
A
M
AM
Hz. 1H NMR (295 K, CD Cl ): 1.48 (br s, CH , 3H of 14 and
2.6 ] 10~2 mmol) in dichloromethane-d (10 mL) and capped
2
2
3
2
14º), 2.5È2.4 (m, CH , 6H of 14 and 14º).
with a septum. The tube was cooled down to [78 ¡C and
2
MeOTf (4.4 lL, 3.8 ] 10~2 mmol) was added with a syringe.
The tube was shaken and inserted into the NMR probehead
pre-cooled to [30 ¡C and a 31PM1HN NMR spectrum was
immediately recorded. It showed the formation of 17 (70%)
Electrophilic alkylation reations
[(triphos)Re(CO) (CNCH )]OTf (15). A Schlenk tube was
2
3
charged with 6 (100.0 mg, 0.11 mmol) dissolved in dichloro-
methane (10 mL) and MeOTf (14 lL, 0.12 mmol) was added
under vigorous stirring with a syringe. Evaporation of the
solution to dryness under vacuum gave 15, as a yellow
powder. The crude product was recrystallized by dichloro-
and of the N-alkylated isomer [(triphos)Re(CO) Mg1-Se-
2
Se(Me)(CN)N]OTf (18) (30%). On standing at low temperature,
18 transforms into 17 within one night. The transformation is
completed in 1 h at room temperature. 31PM1HN NMR (243 K,
216
New J. Chem., 1999, 207È217

View Article Online
16 C. Bianchini, A. Meli, M. Peruzzini and F. Vizza, Organometallics,
1990, 9, 226.
CD Cl ) of 18: AM spin system, d [3.53, d [13.10, J
AM
2
2
2
A
M
18.2 Hz.
Reaction of [(triphos)Re(CO) (N )] and
17 S. L. Bartley, S. N. Bernstein and K. R. Dunbar, Inorg. Chim. Acta,
1993, 213, 213.
18 K. Nakamoto, Infrared and Raman Spectra of Inorganic and Co-
ordination Compounds, Wiley & Sons, New York, 4th edn., 1986.
19 (a) T. S. Peng, C. H. Winter and J. A. Gladysz, Inorg. Chem., 1994,
33, 2534; (b) G. A. Stark, A. M. Arif and J. A. Gladysz,
Organometallics, 1997, 16, 2909.
2
3
[(triphos)Re(CO) (NCO)] with MeOTf
2
Repeating the electrophilic methylation on either the azide (8)
or the cyanate complex (14) gave the triÑate complex 3 in
quantitative yield. Monitoring of both the reactions by NMR
spectroscopy did not give further information about the reac-
tion mechanisms and did not disclose any intermediate
species.
20 (a) C. Diaz and A. Arancibia, Inorg. Chim. Acta, 1998, 269, 246; (b)
G. Barrado, G. A. Carriedo, C. D. Valenzuela and V. Riera, Inorg.
Chem., 1991, 30, 4416; (c) P. C. Cagle, O. Meyer, K. Weickhardt,
A. M. Arif and J. A. Gladysz, J. Am. Chem. Soc., 1995, 117, 11730;
(d) C. A. Bignozzi, S. Roffia, C. Chiorboli, J. Davila, M. T. Indelli
and F. Scandola, Inorg. Chem., 1989, 28, 4350.
Acknowledgements
21 W. M. Laidlaw, R. G. Denning, T. Verbiest, E. Chauchard, A.
Persons, Nature (L ondon), 1993, 363, 58.
We are grateful to the EC (ERBIC15CT960746) for Ðnancial
support. Thanks are expressed to Mr M. Fratta (University of
Ferrara) for technical assistance and elemental analyses, to Mr
E. Angeli (University of Ferrara) for the FAB measurements,
and to Professor A. Romerosa (University of Almeria, Spain)
for helpful discussions.
22 See for example: R. Argazzi, C. A. Bignozzi, T. A. Heimer, G. J.
Meyer, Inorg. Chem., 1997, 36, 2 and references therein.
23 The cyanide toxicity has been recently associated with the forma-
tion of FewCNwCu units interacting with cytochrome-c; see
M. J. Scott, S. C. Lee and R. H. Holm, Inorg. Chem., 1994, 33,
4651.
24 R. J. Abraham and P. Loftus, Proton and Carbon-13 NMR Spec-
troscopy, Heyden, London, UK, 1978.
Notes and references
25 H. Friebolin, Basic One- and T wo-Dimensional NMR Spectroscopy,
VCH, Weinheim, Germany, 2nd edn., 1993.
1 (a) C. Bianchini, A. Marchi, L. Marvelli, M. Peruzzini, A.
Romerosa, R. Rossi and A. Vacca, Organometallics, 1995, 14, 3203;
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