Kinetic study of the alkylation of cyanide at [NBu4][trans-Re(CN)2(dppe)2]. Crystal structures of [NBu4][trans-Re(CN)2(dppe)2] and trans-[Re(CN)2(dppe)2]

Article abstract of DOI:10.1016/S0022-328X(99)00113-8

The mechanism of alkylation of [NBu₄][trans-Re(CN)₂(dppe)₂] (1) by alkyl iodides (RI; R=Me, Et or Pr) or EtBr was studied by stopped-flow techniques, which indicate that it involves a fast first alkylation to give trans-[Re(CN)(CNR)(dppe)₂] that undergoes a subsequent relatively slow alkylation at the cyano-ligand with a rate constant that decreases with the increase of the carbon chain length of the R group and with the replacement of iodide by bromide in the organohalide. Sodium iodide inhibits the rates of alkylation, probably by forming ion pairs with trans-[Re(CN)₂(dppe)₂]^- as confirmed by the formation of the adducts [Re(CN)(CNM)(dppe)₂] (M=Li, Na, Tl or Ag) by reaction of 1 with convenient metal salts and by the kinetics of the reaction between MeI and [Re(CN)(CNNa)(dppe)₂]. The X-ray molecular structures of [NBu₄][trans-Re(CN)₂(dppe)₂] and trans-[Re(CN)₂(dppe)₂] confirm they have pseudo octahedral geometries and indicate that the former crystallizes in the triclinic P1 space group with a=17.938(2), b=18.473(3), c=20.061(3) A and the latter in the monoclinic space group P2₁/c with a=11.673(2), b=13.302(3), c=17.166(4) A.

Full text of DOI:10.1016/S0022-328X(99)00113-8

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 583 (1999) 56–62
Kinetic study of the alkylation of cyanide at
[NBu4][trans-Re(CN)2(dppe)2]. Crystal structures of
[NBu4][trans-Re(CN)2(dppe)2] and trans-[Re(CN)2(dppe)2]ꢀ
M. Fernanda N.N. Carvalho a, M. Teresa Duarte a, Adelino M. Galva˜o a,
Armando J.L. Pombeiro a,*, Richard Henderson b, Hartmut Fuess c, Ingrid Svoboda c
a Centro de Qu´ımica Estrutural, Complexo I, Instituto Superior Te´cnico, A6. Ro6isco Pais, 1049-001 Lisbon, Portugal
b Nitrogen Fixation Laboratory, John-Innes Centre, Norwich Research Park, Colney Lane, Norwich NR4 7UH, UK
c Strukturforschung, FB Materialwissenschaft, Technische Uni6ersita¨t, Petersenstrasse 23, 64287 Darmstadt, Germany
Received 10 July 1998; received in revised form 28 September 1998
Abstract
The mechanism of alkylation of [NBu4][trans-Re(CN)2(dppe)2] (1) by alkyl iodides (RI; R=Me, Et or Pr) or EtBr was studied
by stopped-flow techniques, which indicate that it involves a fast first alkylation to give trans-[Re(CN)(CNR)(dppe)2] that
undergoes a subsequent relatively slow alkylation at the cyano-ligand with a rate constant that decreases with the increase of the
carbon chain length of the R group and with the replacement of iodide by bromide in the organohalide. Sodium iodide inhibits
the rates of alkylation, probably by forming ion pairs with trans-[Re(CN)2(dppe)2]− as confirmed by the formation of the adducts
[Re(CN)(CNM)(dppe)2] (M=Li, Na, Tl or Ag) by reaction of 1 with convenient metal salts and by the kinetics of the reaction
between MeI and [Re(CN)(CNNa)(dppe)2]. The X-ray molecular structures of [NBu4][trans-Re(CN)2(dppe)2] and trans-
[Re(CN)2(dppe)2] confirm they have pseudo octahedral geometries and indicate that the former crystallizes in the triclinic P1 space
,
group with a=17.938(2), b=18.473(3), c=20.061(3) A and the latter in the monoclinic space group P21/c with a=11.673(2),
,
b=13.302(3), c=17.166(4) A. © 1999 Elsevier Science S.A. All rights reserved.
Keywords: Alkylation; Kinetic studies; Stopped flow spectrophotometry; Cyanide; Isocyanide; Organohalide; Rhenium; X-ray analyses
kinetic study of this process and of that of the
[Re(CN)(CNNa)(dppe)2] adduct.
1. Introduction
It was previously demonstrated [1] that cyanide coor-
dinated at [NBu4][trans-Re(CN)2(dppe)2] (1) is readily
alkylated, by species such as [Et3O][BF4] or RI (R=
Me, Et or Pr), affording the bis-isocyanide species
trans-[Re(CNR)2(dppe)2]+. However, it remained un-
known if the process involved electrophilic attack at the
electron-rich anionic centre or direct attack on the
cyanide ligand, as well as the effect of the R moiety or
the halide character on the kinetics. We now report a
The crystal structures of the first complex and of that
readily derived upon oxidation, trans-[Re(CN)2(dppe)2],
are also reported.
2. Results and discussion
2.1. Kinetic studies for the alkylation of the
dicyano-complex
The reactions of [NBu4][trans-Re(CN)2(dppe)2] (1)
with alkyl halides (RX; X=I, R=Me, Et or Pr. X=
Br, R=Et) (Eq. (1)) were studied by stopped-flow
spectrophotometry at u=400 nm in THF, using at
least a tenfold excess of the alkylating agent.
ꢀ Dedicated to Professor Alberto Ceccon on the occasion of his
65th birthday.
* Corresponding author. Tel.+351-1-841-9237; fax: +351-1-846-
4455/4457.
E-mail address: pombeiro@alfa.ist.utl.pt (A.J.L. Pombeiro)
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00113-8

M.F.N.N. Car6alho et al. / Journal of Organometallic Chemistry 583 (1999) 56–62
57
[NBu4][trans-Re(CN)2(dppe)]2+2RX
(1)
“trans-[Re(CNR)2(dppe)2]X+[NBu4]X
(1)
The absorbance versus time traces have an initial
absorbance (Ai) slightly lower than that of the precursor
cyanide complex (A0) and close to that of the mixed
cyanide–isocyanide
intermediate
trans-
[Re(CN)(CNR)(dppe)2] (Ai=0.42, for R=Me, see Fig.
1). The final absorbance Aꢀ=0.13, R=Me) is in good
agreement with that of the dialkylated complex trans-
[Re(CNR)2(dppe)2]+. The traces are an excellent fit to a
single exponential curve as shown in Fig. 1.
The exponential nature of the curves is consistent
with a first order dependence on the concentration of
the complex (1). This was confirmed by observing that
kobs was unaffected by varying the complex concentra-
tion (in the 1×10−4–5×10−3 mol dm−3 range), at a
constant concentration (1×10−3 mol dm−3 or 50×
10−3 mol dm−3) of the alkylating agent. The depen-
dence on the concentration of RX is first order as shown
in Fig. 2, for the reaction with MeI.
Fig. 2. Plot of kobs versus [MeI] for reaction (1), in THF at 25°C.
Concentration of complex (1)=1.0×10−4 M.
The rate law for the second alkylation process is given
by Eq. (4):
d[Re]
dt
−
=k2[RX][Re(CN)(CNR)(dppe)2]
(4)
The observed behaviour is in agreement with a fast
first alkylation process occurring within the dead-time
(2 ms) of the apparatus (reaction 2), followed by the
second alkylation process (reaction 3) which is the
reaction being monitored.
The rate constant of the second alkylation reaction
with RI (k2) shows a marked influence of the nature of
R (Figs. 2 and 3): k2=9.190.3 (R=Me); 0.6790.03
(R=Et) and 0.4590.03 (R=Pr) dm3 mol−1 −1, in a
s
different order to that expected on the basis of the C-I
dissociation energy (239.0, 233.3 or 233.1 kJ mol−1 for
R=Me, Et or Pr, respectively [2]), but following the
steric effects of R which appear to be the dominant
ones. However, for EtBr, with a much higher C-halogen
dissociation energy (292 kJ mol−1 [2]), the alkylation
reaction is clearly slower (3.32×10−291.6×10−4
[NBu4][trans-Re(CN)2(dppe)]2+RX
(1)
k
“1 [Re(CN)(CNR)(dppe)2]+[NBu4]X
(2)
k
[Re(CN)(CNR)(dppe)]2+RX“2 [Re(CNR)2(dppe)2]X
(3)
dm3 mol−1 −1).
s
Since the lowest concentration of MeI used was 1
mmol dm−3, and even under these conditions the k1
step is complete within the dead-time of the stopped-
flow apparatus (2 ms) we can calculate that k1]3×105
dm3 mol−1 s−1
.
In order to obtain further information on the alkyla-
tion kinetics we studied the effects of adding [NBu4]CN,
CNMe or NaI.
Fig. 1. Absorbance versus time dependence for the reaction of
[NBu4][trans-Re(CN)2(dppe)2] (1) (1.0×10−4 M) with MeI (1.0×
10−1 M), in THF at u=400 nm, temperature=25°C; A0, ab-
sorbance of complex (1). Curve was fitted using kobs=0.649 s−1
DA= −0.31, Aꢀ=0.13, the residuals are shown at the bottom.
,
Fig. 3. Plot of kobs versus [RI] (R=Et or Pr) for reaction (1), in THF
at 25°C. Concentration of complex (1)=1.0×10−4 M.

58
M.F.N.N. Car6alho et al. / Journal of Organometallic Chemistry 583 (1999) 56–62
Fig. 4. Dependence of kobs on (a) added cyanide or (b) methyl
isocyanide for the reaction of (1) (1.0×10−4 M) with MeI (1.25×
10−2 M and 1.0×10−2 M, respectively) in THF at 25°C.
Scheme 1.
d[Re(CN)2(dppe)2−]
(1.6890.05)×103[MeI]
!
"
(5)
−
=
dt
1+(4.890.9)×102[NaI]
×[Re(CN)2(dppe)2−]
This behaviour is consistent with the mechanism
At
a
constant concentration of [NBu4][trans-
Re(CN)2(dppe)2] (1) and RX, the addition of CN− or
CNMe does not affect the rate of the reaction over
the concentration range amenable to study as shown
in Fig. 4(a) and (b).
shown in Scheme 1, in which Re=Re(dppe)2.
In this mechanism adduct formation between NaI
and [Re(CN)2(dppe)2]− successively generates the spe-
cies
[Re(CN)(CNNa)(dppe)2]
and
[Re(CNNa)2-
(dppe)2]+. In the first of these adducts it is to be
expected that the electron-withdrawing Na+ decreases
the nucleophilicity of the CN ligands and that this
effect is compounded for [Re(CNNa)2(dppe)2]+.
The general rate law associated with the mechanism
in Scheme 1 is presented in Eq. (6):
However, added sodium iodide disturbs the alkyla-
tion process in a complicated way. We have shown
that this complexity is attributable to the formation
of Na+ adducts as discussed below.
2.2. The reaction between trans-[Re(CN)2(dppe)]−
d[Re(CN)2(dppe)2−]
and MeI in the presence of NaI
−
dt
The addition of an excess of NaI to the reaction
between trans-[Re(CN)2(dppe)2]− (1) and MeI affects
the rate as shown in Fig. 5.
Under these conditions, the absorbance–time curves
are exponential, indicating a first order dependence on
the concentration of complex. In addition the initial
absorbance corresponds to that of (1).
Two features are evident from the data on Fig. 5:
(i) at low concentrations of NaI, the value of kobs
[MeI] is higher than that of k2, and (ii) at high con-
centrations of NaI the MeI reaction is inhibited.
Numerical analysis of these data results in the rate
law shown in Eq. (5):
k +kNaKa[NaI]+kN3 aK K [NaI]2
!
"
1
2
a
b
=
1+Ka[NaI]+KaKb[NaI]2
×[MeI][Re(CN)2(dppe)2−]
(6)
This rate law is derived assuming that formation of
adducts are rapidly established equilibria. Inspection
of the data in Fig. 5 shows that, even at the lowest
concentration of NaI (0.5 mmol dm−3) quantitative
formation of [Re(CN)(CNNa)(dppe)2] occurs, indicat-
ing Ka[NaI]\1 and Ka]2×103 dm3 mol−1. In addi-
tion, at high [NaI] the rate becomes vanishingly small
with kN3 a=insignificant. Thus, under the conditions
our experiments were performed, Eq. (6) simplifies to
Eq. (7):
/
d[Re(CN)2(dppe)2−] k2Na[MeI][Re(CN)2(dppe)2−]
−
=
dt
1+Kb[NaI]
(7)
Comparison with Eq. (5) gives kN2 a=(1.6890.05)
×103 dm3 mol−1 s−1 and Kb=(4.890.9)×102 dm3
mol−1
.
This interpretation of the effect of NaI on the reac-
tion with MeI is intuitively reasonable with k1ꢁ
k2Naꢁk3Na and Ka\Kb.
The effect of ion-pairing on the nucleophilicity of
metal complexes has been surveyed [3]. Further confir-
mation of our proposal comes from the isolation of a
variety of adducts with mono-cations discussed below.
Fig. 5. Plot of kobs versus [NaI] for the reaction of (1) (1.0×10−4 M)
with MeI (2.5×10−2 M) in THF at 25°C.

M.F.N.N. Car6alho et al. / Journal of Organometallic Chemistry 583 (1999) 56–62
59
2.3. Reactions of the dicyano-complex with metal salts.
Formation of the adducts trans-[Re(CN)(CNM)(dppe)2]
(M=Li, Na, Tl or Ag)
trans-[Re(CN)(CNM)(dppe)2]+2MeI
(2, M=Na)
“trans-[Re(CNMe)2(dppe)2]I+NaI
(9)
The kinetics of this reaction were studied, by
stopped-flow spectrophotometry, under similar experi-
mental conditions to those used for the dicyano-com-
plex (see above). The absorbance–time curves are a
single exponential, indicating a first order dependence
on the concentration of complex. However, the lower
solubility of [Re(CN)(CNNa)(dppe)2] in THF leads to
very small absorbance changes (DA=0.01, compared
with DA=0.32 for studies with [Re(CN)2(dppe)2]−).
This results in a large error for the rate constant. Over
We have previously observed [1] that [NBu4][trans-
Re(CN)2(dppe)2] (1) reacts with Ag[BF4] to give trans-
[Re(CN)(CNAg)(dppe)2],
a
rather insoluble and
unstable species in solution. In the mass spectrum
(FAB/MS) of this complex, the molecular ion (M+
1143, using a nitrobenzylic alcohol matrix) is clearly
detected although displaying a much lower intensity
than the fragment (1035) corresponding to the molecu-
lar ion of the much more stable compound
[Re(CN)2(dppe)2] [4].
In order to get further evidence for the ability of 1 to
react with metal salts with formation of adducts we
investigated its reactions with MX (LiClO4, NaI and
TlBF4). In general the reactions of MX with
[Re(CN)2(dppe)2]− in THF afford products that are
poorly soluble in the usual solvents and, upon at-
tempted recrystallisation, undergo oxidation conceiv-
ably by adventitious oxygen to give trans-[Re(CN)2-
(dppe)2], as observed [4] previously for the parent com-
plex 1, thus preventing their characterization by NMR
spectroscopy. However, FAB/MS, elemental microanal-
ysis and IR spectroscopy support their formulation as
the adducts [Re(CN)(CNM)(dppe)2] (2; M=Li, Na or
Tl) formed according to reaction (8):
the concentration range, [MeI]+0.25–2.5 mmol dm−3
the kinetics follow a first order dependence on MeI
(k4=70920 dm3 mol−1 −1). This effect is qualita-
,
s
tively that predicted by our mechanism in Scheme 1 (i.e.
k4Bk1). The difference between the values of kN2 a and
k4 is presumably due to the use of NaI in the former
and Na+ in the latter.
The first alkylation of [Re(CN)(CNNa)(dppe)2] is
slower than the first alkylation of the anionic complex
[Re(CN)2(dppe)2]−, as expected, but faster than that of
[Re(CN)(CNMe)(dppe)2] (reaction 3) possibly on ac-
count of the significant ionic character of the CN–Na
interaction which makes the CNNa ligand a better
electron donor than CNMe. Moreover, the reaction of
[Re(CN)(CNNa)(dppe)2] with MeI produces [Re(C-
NMe)2(dppe)2]+ in a process associated with a single
exponential, rate-limited by the first alkylation step.
This indicates that the reaction of MeI with [Re(C-
NMe)(CNNa)(dppe)2]+ is faster than MeI reacting
with [Re(CN)(CNMe)(dppe)2] (Eq. (3)). It seems likely
that the Na+ has a promoting effect on the H3C–I
bond cleavage process, possibly involving a transition
state of the type shown below:
[NBu4][Re(CN)2(dppe)]2+MX
(1)
“[Re(CN)(CNR)(dppe)2]+[NBu4]X
(8)
(2)
Hence, the molecular ions of the Li+ and Na+
adducts are clearly detected in their FAB/MS spectra at
M+ 1042 (1,4-butanediol as matrix) and 1058 (ni-
trobenzylic alcohol matrix), respectively, as well as the
fragment [M–M%]+ (1035) corresponding to the molec-
ular ion of the more stable decomposition product
[Re(CN)2(dppe)2].
In the IR (KBr or Nujol) spectra of the adducts (2,
M=Li, Na or Tl) a strong and broad band is observed
at 1985, 1970 or 1945 cm−1, respectively, being as-
signed to w(CN). These values, as expected, are consid-
erably lower than that of the dicyano Re(II) complex
(2020 cm−1) [4] but fall within the range observed for
the Re(I) compounds 1 (1995 cm−1) [4] and trans-
[Re(CN)(CNMe)(dppe)2] (2080, 1950 cm−1).
2.5. X-ray molecular structures of [NBu4][trans-
Re(CN)2(dppe)2] and trans-[Re(CN)2(dppe)2]
X-ray diffraction analysis performed on a crystal of
[NBu4][trans-Re(CN)2(dppe)2] (1) showed that two
molecules exist per unit cell and the compound displays
a pseudo octahedral geometry (Fig. 6a) and crystallizes
in the triclinic space group P1.
2.4. Alkylation of [Re(CN)(CNNa)(dppe)2]
[Re(CN)(CNNa)(dppe)2] (2, M=Na) in THF, a sol-
vent in which this complex dissolves slightly, is readily
alkylated by MeI to afford trans-[Re(CNMe)2(dppe)2]+
(reaction 9) which was previously obtained [5] upon
replacement of chloride by CNMe at trans-[ReCl-
(CNMe)(dppe)2]:
The two cyanide ligands are mutually trans in both
complexes and display a linear arrangement (ÚC1–
Re–C2=178.1(14)°) around rhenium.
Selected bond angles and distances are displayed in
Table 1, and the fractional atomic coordinates are
available as supplementary material.

60
M.F.N.N. Car6alho et al. / Journal of Organometallic Chemistry 583 (1999) 56–62
Fig. 6. ORTEP drawing of the anion [trans-Re(CN)2(dppe)2]− (a), and of trans-[Re(CN)2(dppe)2] (b), showing the labeling schemes.
Table 1
Selected bond angles and distances are displayed in
Table 2, and the fractional atomic coordinates are
available as supplementary material.
,
Selected bond lengths (A) and angles (°) for [NBu4]-
[trans-Re(CN)2(dppe)2] (1)
These two complexes crystallise in different space
groups and display considerably different Re–P bond
lengths which are shorter in the former, Re(I), complex
Re(1)–C(1)
Re(1)–C(2)
Re(2)–C(3)
Re(2)–C(4)
Re(1)–P(1)
Re(1)–P(2)
Re(1)–P(3)
Re(1)–P(4)
Re(2)–P(5)
Re(2)–P(6)
Re(2)–P(7)
Re(2)–P(8)
N(1)–C(1)
N(2)–C(2)
N(3)–C(3)
N(4)–C(4)
C(11)–C(41)
C(21)–C(31)
C(51)–C(61)
C(71)–C(81)
P–C (average)
2.10(3)
2.08(3)
2.09(3)
2.10(3)
2.381(8)
2.379(8)
2.347(8)
2.366(8)
2.370(8)
2.377(8)
2.356(8)
2.373(8)
1.15(3)
1.16(3)
1.18(3)
1.16(3)
1.37(3)
1.46(3)
1.45(4)
1.48(3)
1.84
,
(2.34–2.38 A) than in the latter, Re(II), compound
,
(2.41–2.42 A). The values measured for the Re(II)
complex are in excellent agreement with those previ-
ously reported for the related complex trans-
,
[ReCl2(dppe)2] (Re–P=2.41–2.42 A) [5]. A related
,
decrease of ca. 0.1 A on the M–P bond length upon
addition of one electron to the metal site was previously
recognized [6] for Re(III) or Mo(III) complexes with
the {M(dppe)2} skeleton.
In contrast, no effect is observed on the Re–C bond
lengths at the Re(I) or Re(II) cyanide complexes,
,
2.10(3) and 2.08(1) A, respectively. Comparatively, the
,
Re–C bond length (2.005(5) A) measured on the re-
lated isocyanide complex trans-[Re(CNEt)2(dppe)2]-
[PF6] is considerably shorter as a consequence of the
better electron withdrawing properties of isocyanide
compared to cyanide.
C(2)–Re(1)–C(1)
C(3)–Re(2)–C(4)
Re(1)–C(1)–N(1)
Re(1)–C(2)–N(2)
Re(2)–C(3)–N(3)
Re(2)–C(4)–N(4)
178(1)
179(1)
178(3)
174(2)
177(3)
177(3)
Table 2
,
Selected bond lengths (A) and angles (°) for trans-[Re(CN)2(dppe)2]
Re(1)–C(1)
Re(1)–P(1)
Re(1)–P(2)
C(11)–C(21)
C(1)–N(1)
P–C (average)
P(1)–Re(1)–P(2)
Re(1)–C(1)–N(1)
2.08(1)
2.410(3)
2.417(3)
1.54(2)
1.17(1)
1.83
The single crystal X-ray diffraction analysis of trans-
[Re(CN)2(dppe)2] showed it crystallizes in the mono-
clinic space group P21/c and displays an octhedral
geometry (Fig. 6b).
The two cyanide ligands also occupy the trans posi-
tion to each other and the molecule presents a centre of
inversion.
79.4(1)
176.0(10)

M.F.N.N. Car6alho et al. / Journal of Organometallic Chemistry 583 (1999) 56–62
61
3. Experimental
3.4. Structure solution and refinement for complexes
3.4.1. [NBu4][trans-Re(CN)2(dppe)2
The complex, Mr=2555, crystallizes in the triclinic
space P1 with a=17.938(2), b=18.473(3), c=
All the solutions were prepared under dinitrogen.
The solvent (THF) was dried by standard methods and
distilled immediately before use. [NBu4][trans-
Re(CN)2(dppe)2] [4], trans-[Re(CN)2(dppe)2] [4] and
trans-[Re(CN)(CNAg)(dppe)2] [1] were prepared by
published methods. The kinetics were performed on a
Cantebury SF-40, from HI-TECH Scientifics at 25°C,
monitoring the absorbance changes associated with the
rhenium complexes at u=400 nm.
The absorbance–time traces were single exponential
in all cases and the rate constants, together with the
initial and the final absorbances, were computed by use
of the Rapid Kinetics Software Suite (version 1.0)
program on a City Desk 386-SX computer interfaced to
the stopped-flow spectrophotometer. Curves were expo-
nential for at least three half-lives. Typical absorbance–
time curves for [NBu4][trans-Re(CN)2(dppe)2] are
shown in Fig. 1.
,
20.061(3) A, h=78.88(1), i=81.46(1), k=85.76(1)°,
3
V=6443 A , Z=2, Dc=1.32 g cm−3, v(Mo–Ka)=
,
20.3 cm−1
.
Two molecules exist by unit cell, orientation matrix
was obatined by least-squares refinement of 25 centred
reflections with 14BqB17° and 17 877 independent
reflections with Rint=0.036 were collected in an Enraf-
Nonius CAD4 diffractometer. 17 842 unique reflections
with F2]0 were used in structure solution and refine-
ment of 725 parameters. The relative position of the Re
atoms was found in a Patterson map and all the other
non hydrogen atoms were located in subsquent differ-
ence Fourier maps. The Re, P and N atoms as well as
the carbon in CN groups were refined isotropically. The
hydrogen atoms of the anionic metal centre were in-
serted in calculated positions. The cation was refined
without hydrogens. The weighting scheme w=1/
[s2(F02)+(0.074*P)2+80.4*P] (P=F02+2*F2c/3) was
found to give an acceptable agreement analysis. Final
refinement converged at RI=0.05 (I\2|(I)). The
molecular structure is shown in Fig. 6(a) and final
atomic coordinates for all the non hydrogen atoms are
available as supplementary material.
3.1. [Re(CN)(CNLi)(dppe)2]
THF (20 cm3) was added to a mixture [NBu4][trans-
Re(CN)2(dppe)2] (35 mg, 0.027 mmol) and LiClO4 (6.0
mg, 0.065 mmol) and the mixture stirred overnight. The
light orange solid was filtered off and dried under
vacuum (20 mg, 71% yield).
FAB/MS (1,4-butanediol matrix): 1042 (M+), 1035
(M–Li+). Elemental analysis: Found (Calc.): %C, 62.4
(62.2); %N, 2.5 (2.7); %H, 4.8 (4.6).
3.4.2. trans-[Re(CN)2(dppe)2]
The complex, Mr=1035.02, crystallises in the mono-
clinic space group P21/c with a=11.673(2), b=
,
13.302(3), c=17.166(4) A, i=96.72(3)°, V=2647(1)
3.2. [Re(CN)(CNNa)(dppe)2]
3
A , Z=2, Dc=1.30 g cm−3, v(Mo–Ka)=24.5 cm−1
.
,
In a similar procedure to that of the previous com-
pound, 9327 reflections 1.5BqB31.5° (4650 indepen-
dent with Rint=0.07) were collected by the ꢀ-2q scan
mode, in an Enraf-Nonius TURBO CAD4 diffractome-
ter equipped with a rotating anode (50 kV, 70 mA),
using graphite monochromated radiation. Three stan-
dard reflections were monitored during data collection
but no decay or instrumental instability was detected
(the loss of intensity is less then 0.1%/h). Using the
CAD4 software, data were corrected for Lorentz and
polarization effects and empirically for absorption
(minimum transmission factor 68%, average transmis-
sion factor 84%). 4200 unique reflections with F2]0
were used in structure solution and refinement of 277
parameters. The position of the Re atom was obtained
by a tridimensional Patterson synthesis and was found
to be located at the special position 1. All the other
non-hydrogen atoms were located in subsequent differ-
ence Fourier maps and refined with anisotropic thermal
motion parameters. The hydrogen atoms were inserted
in calculated positions and refined with fixed distances
THF (10 cm3) was added to
a mixture of
[NBu4][trans-Re(CN)2(dppe)2] (102 mg, 0.080 mmol)
and NaI (13 mg, 0.087 mmol), and the mixture was
stirred for 30 min at room temperature. The yellow
suspension was filtered off and slightly washed with
Et2O (45 mg, 53% yield).
FAB/MS (nitrobenzylic alchool matrix): 1058 (M+),
1035 (M–Na+). Elemental analysis: Found (Calc. with
1/4NaI of crystallisation): %C, 58.8 (59.2); %N, 2.7
(2.6); %H, 4.6 (4.4).
3.3. [Re(CN)(CNTl)(dppe)2]
THF (5 cm3) was added to a mixture of [NBu4][trans-
Re(CN)2(dppe)2] (20 mg, 0.016 mmol) and TlBF4 (15
mg, 0.051 mmol) and the suspension stirred for 1 h.
The orange solid was filtered off and dried under
vacuum (12 mg, 60% yield).
Elemental analysis: Found (Calc. with 1/10TlBF4 of
crystallisation): %C, 49.3 (49.2);%N, 1.9 (2.0);%H, 4.2
(3.8).
,
(1.08 A) to the parent carbon atom. The weighting

62
M.F.N.N. Car6alho et al. / Journal of Organometallic Chemistry 583 (1999) 56–62
scheme
w=1/[s2(F2o)+(0.1188ꢀP)2+13.7ꢀP](P+
Nacional de Investigac¸a˜o Cient´ıfica e Tecnolo´gica
(JNICT), the Fundac¸a˜o para a Cieˆncia e Tecnologia
(FCT), the PRAXIS XXI programme (Portugal) and
the Instituto de Cooperac¸a˜o Cient´ıfica e Tecnolo´gica
Internacional (ICCTI)/The British Council protocol.
F2o+2ꢀF2c/3) was found to give an acceptable agree-
ment analyses. Final refinement converged at R1=0.07
(I\2|(I)). The molecular structure is shown in Fig.
6(b) and final atomic coordinates for all the non hydro-
gen atoms are given in Table 2.
Lists of observed and calculated structure factors, for
both structures, tables of anisotropic thermal parame-
ters, hydrogen atomic coordinates, bond lengths are
avaiable as suplementary material. The structure solu-
tion and refinement were done with SHELX93 [7] and
the illustrations were drawn with ORTEP-II [8]. The
atomic scattering factors and anomalous scattering
terms were taken from International Tables [9].
References
[1] M.F.N.N. Carvalho, M.T. Duarte, A.M. Galva˜o, A.J.L.
Pombeiro, J. Organometal. Chem. 511 (1996) 163.
[2] D.R. Lide (Ed.), Handbook of Chemistry and Physics, 74th Edn.,
CRC Press, Boca Raton, 1993–4.
[3] S. Henderson, R.A. Henderson, Adv. Phys. Org. Chem. 23 (1987)
1, and references therein.
[4] M.F.N.N. Carvalho, M.T. Duarte, A.M. Galva˜o, A.J.L.
Pombeiro, J. Organometal. Chem. 469 (1994) 79.
[5] M.F.N.N. Carvalho, A.J.L. Pombeiro, J. Chem. Soc. Dalton
Trans. (1989) 1209.
4. Supplementary material
[6] T.Al Salih, M.T.Duarte, J.J.R. Frau´sto da Silva, A. M. Galva˜o,
M.F.C. Guedes da Silva, P.B. Hitchcock, D.L. Hughes, C.J.
Pickett, A.J.L. Pombeiro, R.L. Richards, J. Chem. Soc. Dalton
Trans. (1993) 3015.
[7] G.M. Scheldrick, SHELX93; Crystallographic Calculation Pro-
gram, University of Cambridge, 1993.
Ten tables with kinetic data are available as well as
tables with the fractional atomic coordinates for each
of the two X-ray structures.
[8] C.K. Johnson, ORTEP-II, Report ORNL-5138, Oak Ridge Na-
tional Laboratory, Park Ridge, TN, 1976.
Acknowledgements
[9] T. Hahn (Ed.), International Tables for Crystallography, vol. A,
Reidel, Dordrecht, 1983.
This work was partially supported by the Junta
.
.