Synthesis, structure, and reactivity of mononuclear Re(I) oximato complexes

Article abstract of DOI:10.1021/ic062168c

Complexes [Re(ONCMe₂)(CO)₃(bipy)] (1) and [Re(ONCMe₂)(CO)₃(phen)] (2), synthesized by reaction of the respective triflato precursors [Re(OTf)(CO)₃(N-N)] (N-N = bipy, phen) with KONCMe₂, feature O-bonded monodentate oximato Iigands. Compound [Re(CO)₃(phen)(HONCMe₂)]BAr′₄ (3), with a monodentate N-bonded oxime ligand, was prepared by reaction of [Re(OTf)(CO)₃(phen)], HONCMe₂, and NaBAr′ ₄. Deprotonation of 3 afforded 2. The oximato complexes reacted with p-tolylisocyanate, p-tolylisothiocyanate, maleic anhydride, and tetracyanoethylene, affording the products of the insertion of the electrophile into the Re-O bond, compounds 4-7. One representative of each type of compound was fully characterized, including single-crystal X-ray diffraction. The reactions of 1 and 2 with dimethylacetylenedicarboxylate were found to involve first an insertion as the ones mentioned above but followed by incorporation of water, loss of acetone, and formation of the charge-separated neutral amido complexes 9 and 10. The structure of 9 and 10 was determined by X-ray diffraction, and key features of their electronic distribution were studied using a topological analysis of the electron density as obtained from the Fourier map.

Full text of DOI:10.1021/ic062168c

Inorg. Chem. 2007, 46, 2836−2845
Synthesis, Structure, and Reactivity of Mononuclear Re(I) Oximato
Complexes
Luciano Cuesta,† Miguel A. Huertos,† Dolores Morales,† Julio Pe´rez,*,† Luc´ıa Riera,† V´ıctor Riera,†
Daniel Miguel,‡ Amador Mene´ndez-Vela´zquez,§,£ and Santiago Garc´ıa-Granda|
Departamento de Qu´ımica Orga´nica e Inorga´nica -IUQOEM, Facultad de Qu´ımica, UniVersidad
de OViedo-CSIC, 33006 OViedo, Spain, Departamento de Qu´ımica Inorga´nica, Facultad de
Ciencias, UniVersidad de Valladolid, 47005 Valladolid, Spain, Instituto de Ciencia de Materiales
de Madrid, CSIC, Cantoblanco Ctra de Colmenar Km 15, 28049 Madrid, Spain, SpLine, European
Synchrotron Radiation Facility, 6 rue Jules Horowit, BP 220, F-38043 Grenoble CEDEX, France,
and Departamento de Qu´ımica F´ısica y Anal´ıtica, Facultad de Qu´ımica, UniVersidad de OViedo,
33006 OViedo, Spain
Received November 14, 2006
Complexes [Re(ONCMe2)(CO)3(bipy)] (1) and [Re(ONCMe2)(CO)3(phen)] (2), synthesized by reaction of the respective
triflato precursors [Re(OTf)(CO)3(N N)] (N bipy, phen) with KONCMe2, feature O-bonded monodentate oximato
ligands. Compound [Re(CO)3(phen)(HONCMe2)]BAr 4 (3), with a monodentate N-bonded oxime ligand, was prepared
by reaction of [Re(OTf)(CO)3(phen)], HONCMe2, and NaBAr 4. Deprotonation of 3 afforded 2. The oximato complexes
reacted with p-tolylisocyanate, p-tolylisothiocyanate, maleic anhydride, and tetracyanoethylene, affording the products
of the insertion of the electrophile into the Re O bond, compounds 4 7. One representative of each type of
−
−N )
′
′
−
−
compound was fully characterized, including single-crystal X-ray diffraction. The reactions of 1 and 2 with
dimethylacetylenedicarboxylate were found to involve first an insertion as the ones mentioned above but followed
by incorporation of water, loss of acetone, and formation of the charge-separated neutral amido complexes 9 and
10. The structure of 9 and 10 was determined by X-ray diffraction, and key features of their electronic distribution
were studied using a topological analysis of the electron density as obtained from the Fourier map.
Introduction
or more metals results in that many oximato complexes are
polynuclear species. In particular, this is the most common
situation for transition metal carbonyl complexes, the ones
more pertinent to this work.2 Most mononuclear carbonyl
complexes containing oximato ligands are of the type [MCp-
{ONC(R)R′}(CO)3] (M ) Mo, W; Cp ) η5-cyclopentadi-
enyl), with a κ(N,O) bidentate oximate ligand.3
Due to the presence of lone electron pairs on the adjacent
oxygen and nitrogen atoms, oximato ligands have been found
to be able to adopt several different coordination modes.1
The tendency of the ligand to act as a bridge between two
* To whom correspondence should be addressed. E-mail: japm@uniovi.es.
Fax: (34) 985103446.
† Universidad de Oviedo-CSIC.
(2) (a) Khare, G. P.; Doedens, R. J. Inorg. Chem. 1976, 15, 86. (b) Aime,
S.; Gervasio, G.; Milone, L.; Rossetti, R.; Stanghellini, P. L. Chem.
Commun. 1976, 11, 370. (c) Aime, S.; Gervasio, G.; Milone, L.;
Rossetti, R.; Stanghellini, P. L. J. Chem. Soc., Dalton Trans. 1978,
534. (d) Carofligio, T.; Stella, S.; Floriani, C.; Chiesi-Villa, A.;
Guastini, C. J. Chem. Soc., Dalton Trans. 1989, 1957. (e) Deeming,
A. J.; Owen, D. W.; Powell, N. I. J. Organomet. Chem. 1990, 398,
229. (f) Chao, M.; Kumaresan, S.; Wen, Y.; Lin, S.; Hwu, J. R.; Lu,
K. Organometallics 2000, 19, 714. (g) Wong, J. S.; Wong, W. New
J. Chem. 2002, 26, 94. (h) Cabeza, J. A., del R´ıo, I.; Riera, V.; Sua´rez,
M.; Alvarez-Ru´a, C.; Garc´ıa-Granda, S.; Chuang, S. H.; Hwu, J. R.
Eur. J. Inorg. Chem. 2003, 23, 4159.
‡ Universidad de Valladolid.
§ Instituto de Ciencia de Materiales de Madrid.
£ European Synchrotron Radiation Facility.
| Universidad de Oviedo.
(1) (a) Singh, A.; Gupta, V. D.; Srivastava, G.; Mehrotra, R. C. J.
Organomet. Chem. 1974, 64, 145. (b) Chakravorty, A. Coord. Chem.
ReV. 1974, 65, 145. (c) Kukushkin, V. Y.; Tudela, D., Pombeiro, A.
J. L. Coord. Chem. ReV. 1996, 156, 333. (d) Kukushkin, V. Y.;
Pombeiro, A. J. L. Coord. Chem. ReV. 1999, 181, 147. (e) Mehrotra,
R. C. In ComprehensiVe Coordination Chemistry; Wilkinson, G.,
Gillard, R. D., McCleverty, J. A., Eds.; Pergamon: Oxford, 2000;
Vol. 2, pp 269-275. (f) Kukushkin, V. Y.; Pombeiro, A. J. L.;
Mehrotra, R. C. In ComprehensiVe Coordination Chemistry II;
McCleverty, J. A., Meyer, T. J., Eds.; Elsevier: Oxford, 2004; Vol 1,
pp 631-637.
(3) (a) Khare, G. P.; Doedens, R. J. Inorg. Chem. 1977, 16, 907. (b) King,
R. B.; Chen, K. N. Inorg. Chem. 1977, 16, 1164. (c) For examples of
mononuclear carbonyl oxime/oximato complexes with other metal
fragments, see: Meyer, U.; Werner, H. Chem. Ber. 1990, 123, 697.
2836 Inorganic Chemistry, Vol. 46, No. 7, 2007
10.1021/ic062168c CCC: $37.00
© 2007 American Chemical Society
Published on Web 02/14/2007

Mononuclear Re(I) Oximato Complexes
Scheme 1. Synthesis of the Oximato and Oxime Complexes,
[Re(ONCMe2)(CO)3(N-N)] (1-2) and
[Re{N(OH)CMe2}(CO)3(phen)]BAr’4 (3), Respectively; Transformation
of the Latter into the Former by Deprotonation.
Figure 1. Thermal ellipsoid (30%) plot of [Re(ONCMe2)(CO)3(bipy)] (1).
Selected bond distances [Å] and angles [deg]: Re(1)-O(4) 2.079(4), N(3)-
C(4) 1.282(9), N(3)-O(4) 1.368(6), N(3)-O(4)-Re(1) 118.2(3), C(4)-
N(3)-O(4) 112.6(6).
In addition to spectroscopic characterization (see Experi-
mental Section), single crystals grown by slow diffusion of
diethyl ether into a THF solution of complex 1 were found
to be suitable for X-ray diffraction, and the results of the
structural determination are summarized in Figure 1. The
molecule of 1 features an oximato ligand bound through its
oxygen atom to a {Re(CO)3(bipy)} fragment and a Re-O
distance, 2.079(4) Å, similar to that found in the methoxo
complex [Re(OMe)(CO)3(bipy)] (2.081(5) Å).10
The monodentate coordination of the oximato ligand in
compounds 1 and 2 is enforced by the lack of additional
open metal coordination sites in these 18-electron products,
and the preference for coordination through oxygen, the atom
bearing the negative charge, over N-coordination, has been
encountered for previously reported terminal oximato com-
plexes.1
Since there is no significant difference in the reactivity of
the [ReX(CO)3(N-N)] bipy and phen derivatives, in most
of what follows only the chemistry of one of the oximato
complexes will be discussed, and only one product of each
type of reaction, the one for which X-ray quality crystals
could be obtained, will be characterized.
To compare the complex of the anionic oximato ligand
with that of the neutral oxime, we prepared [Re(CO)3-
(HONCMe2)(phen)]BAr′4 (3) by the reaction of [Re(OTf)-
(CO)3(phen)], HONCMe2, and NaBAr′4 in CH2Cl2.11 Com-
pound 3 was characterized spectroscopically (see Experimental
Section) and by X-ray diffraction (see Figure 2).
We have recently found that complexes [ReX(CO)3(N-
N)] (N-N ) 2,2′-bipyridine, bipy, or 1,10-phenanthroline,
phen), where X is an anionic ligand with one or two lone
electron pairs, such as alkoxo,4 hydroxo,5 amido,6 alkylide-
neamido,7 or phosphido,8 display a rich X-based reactivity
toward organic electrophiles. We set out to study if related
complexes featuring terminal oximato ligands could be
prepared and, if so, how they would react toward organic
electrophiles. Our findings are reported in what follows.
Results and Discussion
Complexes [Re(ONCMe2)(CO)3(bipy)] (1) and [Re-
(ONCMe2)(CO)3(phen)] (2) were obtained as the single
products of the reactions of in situ-generated KONCMe2 with
[Re(OTf)(CO)3(bipy)]4b or [Re(OTf)(CO)3(phen)],4b respec-
tively, in THF (see Scheme 1 and the Experimental Section).
Precedents of this kind of synthetic procedure date back as
early as 1970.9
(4) (a) Hevia, E.; Pe´rez, J.; Riera, L.; Riera, V.; Miguel, D. Organome-
tallics 2002, 21, 1750. (b) Hevia, E.; Pe´rez, J.; Riera, L.; Riera, V.;
del R´ıo, I.; Garc´ıa-Granda, S.; Miguel, D. Chem. Eur. J. 2002, 8, 4510.
(5) (a) Morales, D.; Navarro Clemente, M. E.; Pe´rez, J.; Riera, L.; Riera,
V.; Miguel, D. Organometallics 2002, 21, 4934. (b) Gerbino, D. C.;
Hevia, E.; Morales, D.; Navarro Clemente, M. E.; Pe´rez, J.; Riera,
L.; Riera, V.; Miguel, D. Chem. Commun. 2003, 328. (c) Cuesta, L.;
Gerbino, D. C.; Hevia, E.; Morales, D.; Navarro Clemente, M. E.;
Pe´rez, J.; Riera, L.; Riera, V.; Miguel, D.; del R´ıo, I.; Garc´ıa-Granda,
S. Chem. Eur. J. 2004, 10, 1765. (d) Cuesta, L.; Hevia, E.; Morales,
D.; Pe´rez, J.; Riera, L.; Miguel, D. Organometallics 2006, 25, 1717.
(6) (a) Hevia, E.; Pe´rez, J.; Riera, V.; Miguel, D. Organometallics 2002,
21, 1966. (b) Hevia, E.; Pe´rez, J.; Riera, V.; Miguel, D. Chem.
Commun. 2002, 1814. (c) Hevia, E.; Pe´rez, J.; Riera, V.; Miguel, D.
Organometallics 2003, 22, 257.
(7) (a) Hevia, E.; Pe´rez, J.; Riera, V.; Miguel, D. Angew. Chem., Int. Ed.
2002, 20, 3558. (b) Hevia, E.; Pe´rez, J.; Riera, V.; Miguel, D.;
Campomanes, P.; Mene´ndez, M. I.; Sordo, T. L., Garc´ıa-Granda, S.
J. Am. Chem. Soc. 2003, 125, 3706.
(8) (a) Cuesta, L.; Hevia, E.; Morales, D.; Pe´rez, J.; Riera, V.; Rodr´ıguez,
E.; Miguel, D. Chem. Commun. 2005, 116. (b) Cuesta, L, Hevia, E.;
Morales, D. Pe´rez, J.; Riera, V.; Seitz, M.; Miguel, D. Organometallics
2005, 24, 1772.
The main difference between the coordination geometry
of this cationic complex and that of the neutral O-bonded
oximato complex 1 discussed above is that the oxime ligand
is coordinated to rhenium through its nitrogen atom. This
coordination mode is the normally found for oxime com-
plexes.1 Comparison of the Re-N distance in 3 (2.183(6)
Å) with those found in the compounds [Re(CO)3(bipy)(HNd
CPh2)]OTf (2.192(3) Å)7a and [Re(CO)3(bipy)(H2Np-Tol)]-
(10) Gibson, D. H.; Sleadd, B. A.; Yin, X. Organometallics 1998, 17, 2689.
(11) Hevia, E.; Pe´rez, J., Riera V.; Miguel, D. Inorg. Chem. 2002, 41, 4673.
(9) Harrison, P. G.; Zuckerman, J. J. Inorg. Chem. 1970, 9, 175.
Inorganic Chemistry, Vol. 46, No. 7, 2007 2837

Cuesta et al.
carbamato ligand formed. The structure of 4, determined by
X-ray diffraction, is displayed in Figure 3.
The pseudooctahedral molecule of 4 consists of a [N(p-
Tol)C(O)ONCMe2] ligand bonded through the nitrogen from
(p-Tol)NCO to a {Re(CO)3(phen)} fragment. The geometry
about this nitrogen (labeled N(3) in Figure 3) is planar,
indicating electronic delocalization (of the lone pair formally
on nitrogen). The comparison between the distances N(3)-
C(4) ) 1.333(7) Å and N(3)-C(31) ) 1.432(7) Å indicates
that the delocalization involves the carbonyl group rather
than the aryl group. A consequence of this delocalization is
that 4 does not retain the nucleophilic character present in
the oximato precursor, as it is demonstrated by the fact that
4 does not react with excess (p-Tol)NCO.
The preference for N-coordination over O-coordination
observed in complex 4 can be rationalized on the basis of a
softer character for the nitrogen atom, which would be a
better match for the soft, low-oxidation, metal carbonyl
fragment, in line with previous findings.4b
Figure 2. Thermal ellipsoid (30%) plot of the cation of [Re{N(OH)CMe2}-
(CO)3(phen)]BAr′4 (3). Selected bond distances [Å] and angles [deg]: Re-
(1)-N(1) 2.162(5), Re(1)-N(2) 2.170(5), Re(1)-N(3) 2.183(6), N(3)-
O(4) 1.396(9), N(3)-C(4) 1.256(11), Re(1)-N(3)-O(4) 108.4(5), Re(1)-
N(3)-C(4) 137.0(7).
Compound 1 reacted also with the equimolar amount of
p-tolylisothiocyanate ([(p-Tol)NCS], as shown in Scheme 3).
The reaction took 8 h at room temperature (insofar as (p-
Tol)NCS is less electrophilic than (p-Tol)NCO)4b and af-
forded as single product the new yellow complex [Re{SCN-
(p-Tol)ONCMe2}(CO)3(bipy)] (5). As for compound 4 (see
above), the spectroscopic data of 5 indicate the presence of
the oximato and (p-Tol)NCS fragments, as well as the
decrease in electron density of the metal center upon reaction
with the isothiocyanate. The structure of 5 was determined
by X-ray diffraction, and the results are shown in Figure 4.
The distances N(4)-C(4) ) 1.24(2) Å and S(1)-C(4) )
1.73(1) Å are consistent with the double- and single-bond
depictions, respectively, included in Scheme 2. The fact that
the ligand resulting from the insertion of isothiocyanate into
the Re-oximate bond is bonded to Re through S fits the
simple soft/hard arguments mentioned above.
Complex 2 reacted with maleic anhydride over several
hours to afford a mixture of two fac-tricarbonyl compounds,
6a and 6b, as judged by the IR monitoring of the reaction.
Compound 6a could be isolated by fractional crystallization
and was characterized by IR, NMR, and X-ray diffraction
(see Figure 5) as the complex [Re{OC(O)CHdCHC(O)-
ONCMe2}(CO)3(phen)]. The X-ray determination of the
structure of 6a (Figure 5) confirms the formulation given
above, resulting from ring-opening and insertion of maleic
anhydride into the Re-O bond. The Re-O distance in 6a,
2.140(3) Å, is longer than that in the starting oximato
complex 2 (2.079(4) Å), likely a result of the lower donor
capability of the carboxylato ligand bonded to the rhenium
fragment in 6a compared with the oximato ligand in complex
2, also reflected in the substantial increase in IR νCO values.
The spectroscopic data of the byproduct 6b featured IR
OTf (2.250(3) Å)6a suggests that the oxime is a donor (σ-
donor/π-aceptor) comparable to an imine and better than an
amine. The Re-N(oxime) distance in 3 is short for a neutral
ligand, since it is only slightly longer than the Re-N(phen)
distances within the same complex (2.162(5) and 2.170(5)
Å), suggesting that the oxime is a good ligand.
The synthesis of the oxime complex 3 contrasts with the
oxidative addition of the N-O bond of HONCMe2 to a
highly electron-rich Re(I) center observed by Pombeiro and
co-workers.12
Treatment of compound 3 with the strong base KN-
(SiMe3)2 led to the instantaneous formation of the neutral
oximato complex 2, a transformation that illustrates the
preference of oximato and oxime ligands for O- and
N-coordination, respectively, as mentioned above.
Next, the reactivity of the oximato complexes toward the
electrophiles p-tolylisocyanate, p-tolylisothiocyanate, maleic
anhydride, tetracyanoethylene (TCNE), and dimethylacety-
lenedicarboxylate (DMAD) was studied.
Complex 2 reacted with the equimolar amount of p-
tolylisocyanate [(p-Tol)NCO] in 1.5 h at room temperature,
affording as the single product the new orange-colored
complex [Re{N(p-Tol)C(O)ONCMe2}(CO)3(phen)] (4), re-
sulting from the formal insertion of the isocyanate into the
Re-O bond (Scheme 3).
The reaction was accompanied by a shift to higher
wavenumber values of the IR νCO bands (at 2016, 1915, and
1889 cm-1 in THF solution in the product), consistent with
the reaction of the metal carbonyl complex with an electro-
phile. The NMR data of compound 4 include two singlets
1
at 2.11 and 1.61 ppm in H NMR, assigned to the two
inequivalent methyl groups from the oximato ligand, and two
low-intensity singlets at 160.7 and 156.5 ppm in 13C NMR,
assigned to the CdO and CdN carbons, respectively, of the
ν
CO bands higher than those of 2, and an AB system for the
two nonequivalent olefinic hydrogens. We therefore sus-
pected that 6b could be the compound [Re{OC(O)CHd
CHC(O)OH}(CO)3(phen)], with a hydrogenmaleate ligand
resulting from the acid-base reaction between the oximato
complex 2 and maleic acid, present as a contaminant in the
(12) Ferreira, C. M. P.; Guedes da Silva, M. F. C.; Kukushkin, V. Y.;
Frau´sto da Silva, J. J. R.; Pombeiro, A. J. L. Dalton Trans. 1998,
325.
2838 Inorganic Chemistry, Vol. 46, No. 7, 2007

Mononuclear Re(I) Oximato Complexes
Scheme 2. Reaction of the Oximato Complexes [Re(ONCMe2)(CO)3(N-N)] (1-2) toward Different Organic Unsaturated Electrophiles
maleic anhydride due to its partial hydrolysis. To check this
hypothesis, compound 2 was allowed to react with the
equimolar amount of maleic acid. The reaction first afforded
quantitatively the salt [Re(CO)3(phen)(HONCMe2)][OC(O)-
CHdCHC(O)OH] (6′), the result of the protonation of the
oximato ligand by maleic acid. Upon standing in solution
several hours, 6′ was transformed into 6b, the result of the
displacement of the neutral oxime by the anionic hydrogen-
maleate ligand (Scheme 2).
The addition of the equimolar amount of TCNE to a THF
solution of complex 2 led to an instantaneous reaction,
accompanied by a change in the color from red to yellow.
The IR νCO bands shifted to higher frequencies by ca. 30
cm-1. The IR spectrum of the resulting solution features also
two low-intensity bands at 2216 and 2199 cm-1 assigned to
the C-N stretches of the cyano groups (at 2253 cm-1 in
free TCNE). A single product, complex 7, could be char-
1
acterized by IR and H NMR (see Experimental Section).
In addition, slow diffusion of hexane into a solution of 7 in
CH2Cl2 at -20 °C afforded yellow crystals, one of which
Figure 3. Thermal ellipsoid (30%) plot of [Re{N(p-Tol)C(O)ONCMe2}-
(CO)3(phen)] (4). Selected bond distances [Å] and angles [deg]: Re(1)-
N(3) 2.192(5), N(3)-C(4) 1.333(7), N(3)-C(31) 1.432(7), Re(1)-C(31)-
N(3) 120.5(3), Re(1)-C(4)-N(3) 119.5(4), C(4)-N(3)-C(31) 120.0(5).
Figure 4. Thermal ellipsoid (30%) plot of [Re{SCN(p-Tol)ONCMe2}-
(CO)3(bipy)] (5). Selected bond distances [Å] and angles [deg]: Re(1)-
S(1) 2.490(5), S(1)-C(4) 1.736(14), C(4)-N(4) 1.24(2), Re(1)-S(1)-C(4)
115.5(5).
Inorganic Chemistry, Vol. 46, No. 7, 2007 2839

Cuesta et al.
Figure 5. Thermal ellipsoid (30%) plot of [Re{OC(O)CHdCHC(O)-
ONCMe2}(CO)3(phen)] (6a).
Figure 7. Thermal ellipsoid (30%) plot of [Re{NH2C(CO2Me)C(CO2-
Me)(O)}(CO)3(phen)] (9). Selected bond distances [Å]: Re(1)-N(3) 2.237-
(9), N(3)-C(4) 1.463(12), C(5)-O(4) 1.275(12), C(4)-C(6) 1.457(15),
C(6)-O(6) 1.160(11), C(6)-O(7) 1.386(14), C(8)-O(8) 1.211(13), C(8)-
O(9) 1.311(14).
When the reaction was carried out in CD2Cl2 in an NMR
1
tube, H NMR monitoring showed that the transformation
of 8 into 9 was accompanied by the production of an
equimolar amount of acetone, identified by the singlet at 2.12
1
ppm. Compound 9 was characterized by IR and H NMR
(its low solubility precluded the acquisition of a 13C
spectrum) and also by single-crystal X-ray diffraction. In
agreement with the loss of acetone mentioned above, the 1H
NMR spectrum of 9 features only two methyl singlets,
attributed to the two methoxycarbonyl groups from DMAD.
The results of the structural determination are shown in
Figure 7.
The molecule of 9 consists of a {Re(CO)3(phen)} fragment
bonded to the nitrogen atom of a [H2NC(CO2Me)dC(CO2-
Me)O] ligand. Given the structure of 9, the observed
formation of acetone upon transformation of 8 into 9 and
the outcome of the reactions discussed above, we propose
that the intermediate 8 is the product of the formal DMAD
insertion into the Re-O bond depicted in Scheme 3.
Figure 6. Thermal ellipsoid (30%) plot of [Re{C(CN)2C(CN)2ONCMe2}-
(CO)3(phen)] (7). Selected bond distances [Å]: Re(1)-C(4) 2.359(5), C(4)-
C(5) 1.547(7), C(5)-O(5) 1.419(6).
was employed for the structural determination by means of
X-ray diffraction. The results, shown in Figure 6, indicate
that 7 is the product of formal insertion of TCNE into the
Re-O bond of the starting oximato complex. Accordingly,
the distance C(4)-C(5) ) 1.547(7) Å, is consistent with a
single bond. The distance Re-C(4) ) 2.359(5) Å is slightly
longer than the Re-C distances found for other rhenium
alkyl complexes, the same trend found when alkyl complexes
of other metal fragments are compared with the related
polycyanoalkyl complexes.4b Similar parameters were found
in the compound [Re{C(CN)2C(CN)2(OMe)}(CO)3(Me2-
bipy)], the product of the reaction of TCNE with the alkoxo
complex [Re(OMe)(CO)3(Me2bipy)] (Me2bipy ) 4,4′-di-
methyl-2,2′-bipyridine).4b
1
Accordingly, the H NMR spectrum of 8 includes four
methyl singlets; two of them, at higher frequencies, are
assigned to the two methoxycarbonyl groups from the
DMAD reagent, and the other two are assigned to the two
nonequivalent oxime methyl groups. An alkenyl rhenium
complex resulting from the reaction of DMAD with the
rhenium methoxo complex [Re(OMe)(CO)3(bipy)] was pre-
viously reported by us.4a
It was noted that the transformation of 8 into 9 required
the presence of water (the addition of a large excess of water
to a solution of 8 caused its instantaneous transformation
into 9). Since the source of the water involved in the
formation of 9 must be the adventitious traces of water
present in the reaction mixture, the reaction was repeated
several times with solvents as anhydrous as we could get
and with different batches of DMAD and oximato complex.
The same result (slow formation of 9) was consistently
obtained. Furthermore, the formation of the analogous
bipyridine complex [Re(NH2C(CO2Me)dC(CO2Me)O)(CO)3-
The oximato complex 2 reacted instantaneously with the
equimolar amount of DMAD. The reaction yielded initially
a single product, compound 8 (brown), which was isolated
1
as a spectroscopically (IR and H NMR) pure solid. When
left in solution, compound 8 was found to quantitatively
transform into a second species, 9 (yellow), in 8 h at room
temperature.
2840 Inorganic Chemistry, Vol. 46, No. 7, 2007

Mononuclear Re(I) Oximato Complexes
Scheme 3. Proposed Mechanism for the Transformation of Compound 8 into 9.
Chart 1. Electronic Delocalization in Compounds 9 and 10.
(bipy)] (10), the structure of which was confirmed by X-ray
diffraction, was found when the oximato complex 1 was
allowed to react with DMAD (see Experimental Section and
Supporting Information).
A proposed rationale for the transformation of 8 (or its
bipy analog) to 9-10, admittedly a purely speculative one,
is displayed in Scheme 3. The presence of the two strongly
electron-withdrawing methoxycarbonyl groups in 8, as well
as the possible formation of a hydrogen bond to one of the
hydrogen atoms of a molecule of water by the carbonyl
oxygen of one of the -C(O)OMe groups, are factors that
can explain the fact that 8 undergoes hydrolysis in conditions
(only traces of water) in which other products of the reactions
of the oximates 1 and 2, also featuring the -O-NdCMe2
moiety (described above), do not.
The preceding discussion is only based on comparisons
between bond distances. To obtain a more clear picture of
the bond orders, a topological analysis of the electron density
as obtained from the Fourier map was carried out.13 The
results of this study afforded a picture consistent with that
proposed in the preceding discussion. Thus, in 9, the charge
density is 2.017 e/Å3 for the bond C(5)-O(4), intermediate
between the values found for the double bonds C(6)-O(6)
(2.234 e/Å3) and C(8)-O(8) (2.291 e/Å3) and those found
for the single bonds (1.646 e/Å3 for C(6)-O(7) and 1.893
e/Å3 for C(8)-O(9)).
The final product, 9, is depicted as a charge-separated
tautomer, a situation rarely encountered for organometallic
complexes. Experimental evidence in support of this for-
mulation comes both from spectroscopic and X-ray diffrac-
tion data. Thus, the solution IR νCO bands in THF of 9 (2026
and 1919 cm-1) and 10 (2026 and 1918 cm-1) are closer to
those of a cationic amino complex (2034 and 1925 cm-1 for
[Re(CO)3(bipy)(H2Np-Tol)]OTf) than to those of a neutral
amido complex (2003, 1899, and 1884 cm-1 for [Re(HNp-
Tol)(CO)3(bipy)]).6a In the solid state, the Re-N(3) distances
(2.237(9) Å for 9 and 2.248(5) Å for 10) are closer to the
Re-N(amino) distance in [Re(CO)3(bipy)(H2Np-Tol)]OTf
(2.250(3) Å) than to the Re-N(amido) distance in [Re(Np-
Tol)(CO)3(bipy)] (2.112(4) Å).6a This set of data suggest that
the monodentate N-donor is an amino rather than an amido
ligand. With regard to the oxygen atom to which we are
assigning a negative charge, O(4), in complex 10 (in 9 the
corresponding distances are known less accurately) the
distance C(5)-O(4) (1.244(9) Å) is closer to the double bond
C-O distances C(6)-O(6) (1.238(8) Å) and C(8)-O(8)
(1.193(8) Å) than to the single bond C-O distances C(6)-
O(7) (1.340(9) Å) and C(8)-O(9) (1.335(9) Å). This, and
even the difference between the two double bond C-O
distances mentioned above, are consistent with the delocal-
ization depicted in Chart 1.
Likewise, in 10, the charge density is 1.900 e/Å3 for the
bond C(5)-O(4), intermediate between the values found for
the double bonds C(6)-O(6) (2.160 e/Å3) and C(8)-O(8)
(2.047 e/Å3) and those found for the single bonds (1.707
e/Å3 for C(6)-O(7) and 1.801 e/Å3 for C(8)-O(9)).
When the intermolecular interactions are taken into ac-
count, the analysis of the X-ray diffraction data showed that
both compounds 9 and 10 exist as dimers resulting from
strong intermolecular hydrogen bonds in which the amino
N-H bonds act as donors and the oxygen atom labeled O(4)
is the acceptor (N(3)‚‚‚O(4) ) 2.81 Å and N(3)‚‚‚H‚‚‚O(4)
) 146° for compound 9), as shown in Figure 8.
An indication that such dimers maintain their integrity in
solution comes from the low solubility of complexes 9 and
10 in moderately polar organic solvents such as CH2Cl2 or
THF. Further evidence is provided by the presence of two
separate low-intensity, broad signals in the 1H NMR spectra
of 9 and 10 for the two hydrogens of the NH2 group of each
complex. The inequivalence of these two hydrogen atoms
(which would be equivalent in the monomeric Cs-symmetric
(13) Mene´ndez-Vela´zquez, A.; Garc´ıa-Granda, S. J. Appl. Cryst. 2003, 36,
193.
Inorganic Chemistry, Vol. 46, No. 7, 2007 2841

Cuesta et al.
300, DPX-300, or Advance 400 spectrometer. NMR spectra are
1
referred to the internal residual solvent peak for H and 13C{1H}
NMR. IR solution spectra were obtained in a Perkin-Elmer FT
1720-X or RX I FT-IR spectrometer using 0.2 mm. CaF2 cells.
Elemental analyses were performed on a Perkin-Elmer 2400B
microanalyzer.
Synthesis of [Re(ONCMe2)(CO)3(bipy)] (1). KN(SiMe3)2 (0.37
mL of a 0.5 M solution in toluene, 0.18 mmol) was added to a
solution of acetone oxime (0.013 g, 0.17 mmol) in THF (10 mL)
at -78 °C. The resulting colorless solution was transferred via
canula to a solution of [Re(OTf)(CO)3(bipy)] (0.100 g, 0.17 mmol)
in THF (10 mL). The color of the solution changed immediately
from yellow to bright red. After 5 min the solvent was evaporated
under reduced pressure, the residue was extracted with CH2Cl2 (10
mL), and filtered. The solvent was removed in vacuo to a volume
of 5 mL and addition of hexane (20 mL) caused the precipitation
of a red microcrystalline solid, which was washed with diethyl ether
(2 × 5 mL) and redissolved in THF (5 mL). Slow diffusion of
diethyl ether (10 mL) into this solution at room temperature afforded
red crystals of 1, one of which was employed for an X-ray structure
determination. Yield: 0.062 g (69%). IR (THF, cm-1): 2006 vs,
1903 s, 1876 s (νCO). 1H NMR (CD2Cl2): δ 9.03, 8.21, 8.03, 7.51
(m, 2H each, bipy), 1.50 (s, 3H, CH3), 1.12 (s, 3H, CH3). Anal.
Calcd for C16H14N3O4Re:C, 38.55; H, 2.83; N, 8.43. Found: C,
38.16; H, 3.13; N, 8.55.
Figure 8. Hydrogen-bond interactions in the crystalline structure of 9
leading to dimers. Selected intermolecular distance and angle: N(3)‚‚‚O(4)
2.81 Å, N(3)‚‚‚H‚‚‚O(4) 146°.
Synthesis of [Re(ONCMe2)(CO)3(phen)] (2). Compound 2 was
prepared as described above for 1, from [Re(OTf)(CO)3(phen)]
(0.100 g, 0.17 mmol), KN(SiMe3)2 (0.37 mL of a 0.5 M solution
in toluene, 0.18 mmol), and acetone oxime (0.013 g, 0.17 mmol).
Slow diffusion of diethyl ether into a concentrated solution of 2 in
THF at room temperature afforded red crystals. Yield: 0.066 g
molecules) is attributed to their different involvement in the
hydrogen-bonding scheme, depicted in Figure 8. Thus, one
of the hydrogens on N(3) is involved in the mentioned
intermolecular hydrogen bond, whereas the other forms an
intramolecular hydrogen bond with O(6). In addition, the
presence of the strong hydrogen bonds leading to the
formation of the dimers should be a major factor in the
stabilization of the charge-separated tautomer.
In summary, mononuclear complexes [Re(ONCMe2)(CO)3-
(N-N)] (N-N ) bipy or phen) containing O-coordinated
oximato ligands, readily prepared by reaction of [KONdCMe2]
with the respective triflato complexes, reacted with (p-Tol)-
NCO, (p-Tol)NCS, maleic anhydride, TCNE, and DMAD,
affording a single product in each case. The products have
structures corresponding to the formal insertion of the
electrophile into the Re-O bond. While the products of the
first four reactions are stable, the product of the reaction with
DMAD undergoes facile hydrolysis in the presence of the
traces of water present in the solvents. This reaction is a
complex process that involves addition of water, elimination
of acetone, cleavage of the N-O bond, and formation of
Re-N bond.
1
(71%). IR (THF, cm-1): 2007 vs, 1903 s, 1877 s (νCO). H NMR
(CD2Cl2): δ 9.41 (dd, J ) 5.1, 1.5 Hz, 2H, phen), 8.61 (dd, J )
8.2, 1.5 Hz, 2H, phen), 8.05 (s, 2H, phen), 7.89 (dd, J ) 8.2, 5.1
Hz, 2H, phen), 1.42 (s, 3H, CH3), 0.81 (s, 3H, CH3). 13C{1H} NMR
(CD2Cl2): δ 199.9 (2 × CO), 195.0 (CO), 150.1 (CdN), 152.7,
147.4, 137.9, 130.4, 127.3, 125.3 (phen), 20.9, 12.9 (2 × CH3).
Anal. Calcd for C18H14N3O4Re: C, 41.38; H, 2.70; N, 8.04.
Found: C, 40.67; H, 3.01; N, 7.96.
Synthesis of [Re{N(OH)CMe2}(CO)3(phen)]BAr′4 (3). To a
solution of [Re(OTf)(CO)3(phen)] (0.050 g, 0.083 mmol) in CH2-
Cl2 (10 mL), NaBAr′4 (0.074 g, 0.083 mmol), and acetone oxime
(0.007 g, 0.092 mmol) were added. The mixture was stirred at room
temperature for 5 min, filtered via canula, and the solvent was
evaporated under reduced pressure to a volume of 5 mL. Slow
diffusion of hexane (10 mL) into this solution at room temperature
afforded yellow crystals of 3, one of which was employed for an
X-ray structure determination. Yield: 0.104 g (91%). IR (CH2Cl2,
cm-1): 2034 vs, 1932 s, 1923 s (νCO). 1H NMR (CD2Cl2): δ 9.46
(dd, J ) 5.2, 1.2 Hz, 2H, phen), 8.70 (dd, J ) 8.3, 1.2 Hz, 2H,
phen), 8.10 (s, 2H, phen), 8.00 (dd, J ) 8.3, 5.2 Hz, 2H, phen),
7.74 (s, 8H, Ho BAr′4), 7.55 (s, 4H, Hp BAr′4), 5.56 (s, 1H, OH),
2.24 (s, 3H, CH3), 1.86 (s, 3H, CH3). 13C{1H} NMR (CD2Cl2): δ
194.3 (2 × CO), 189.6 (CO), 176.4 (CdN), 161.7 (c(1JCB ) 50.1
Hz), Ci BAr′4), 154.2, 147.1, 140.2, 131.2, 128.3, 126.6 (phen),
134.8 (Co BAr′4), 128.9 (c(2JCF ) 31.5 Hz), Cm BAr′4), 124.5 (c(1JCF
) 272.7 Hz), CF3 BAr′4), 117.5 (Cp BAr′4), 25.4, 19.2 (2 × CH3).
Anal. Calcd for C50H27BF24N3O4Re: C, 43.31; H, 1.96; N, 3.03.
Found: C, 43.58; H, 1.65; N, 3.15.
Experimental Section
All manipulations were carried out under a nitrogen atmosphere
using conventional Schlenk techniques. Solvents were purified
according to standard procedures.14 [Re(OTf)(CO)3(N-N)] (N-N
) bipy, phen)4b and NaBAr′415 were prepared according to literature
procedures. Other reagents were purchased and used as received.
Deuterated solvents were stored under nitrogen in Young tubes.
1H NMR and 13C NMR spectra were recorded on a Bruker Advance
Synthesis of [Re{N(p-Tol)C(O)ONCMe2}(CO)3(phen)] (4). (p-
Tol)NCO (0.012 mL, 0.096 mmol) was added to a solution of [Re-
(ONCMe2)(CO)3(phen)] (2) (0.050 g, 0.096 mmol) in THF (15 mL),
and the mixture was stirred for 2 h. The color of the solution
(14) Perrin, D. D.; Armarego, W. L. F. Purification of Laboratory
Chemicals, 3rd ed.; Pergamon Press: Oxford, 1988.
(15) (a) Brookhart, M.; Grant, B.; Volpe, A. F. Organometallics 1992, 11,
3920.
2842 Inorganic Chemistry, Vol. 46, No. 7, 2007

Mononuclear Re(I) Oximato Complexes
changed from red to orange. The solvent was evaporated under
reduced pressure to a volume of 5 mL, and addition of hexane (15
mL) caused the precipitation of an orange microcrystalline solid,
which was washed with hexane (2 × 5 mL) and diethyl ether (2 ×
5 mL). Compound 4 was redissolved in 10 mL of CH2Cl2, and
slow diffusion of diethyl ether (20 mL) at room temperature
afforded orange crystals, one of which was employed for an X-ray
analysis. Yield: 0.050 g (87%). IR (THF, cm-1): 2016 vs, 1915 s,
1889 s (νCO). 1H NMR (CD2Cl2): δ 9.11 (m, 2H, phen), 8.50 (dd,
J ) 8.2, 1.4 Hz, 2H, phen), 8.01 (s, 2H, phen), 7.66 (dd, J ) 8.2,
5.3 Hz, 2H, phen), 6.49, 5.81, 5.79 (q, AA′BB′system, 4H, p-Tol),
2.11 (s, br, 6H, CH3 p-Tol and CH3 NdC(CH3)2), 1.61 (s, 3H, CH3).
13C{1H} NMR (CD2Cl2): δ 200.7 (2 × CO), 195.6 (CO), 160.7
(CdO), 156.5 (CdN), 149.2, 140.0, 134.0, 132.7, 130.2, 129.6,
128.6, 127. 5 (p-Tol and phen), 27.3 (CH3, p-Tol), 22.7, 17.5 (2 ×
CH3). Anal. Calcd for C26H21N4O5Re‚0.25CH2Cl2: C, 46.58; H,
3.20; N, 8.28. Found: C, 46.19; H, 3.11; N, 8.32.
× 10 mL) and diethyl ether (2 × 10 mL). Yield: 0.022 g (93%).
1
IR (THF, cm-1): 2029 vs, 1926 s, 1916 s (νCO). H NMR (CD2-
Cl2): δ 9.42 (m, 2H, phen), 8.66 (m, 2H, phen), 8.06 (s, 2H, phen),
7.92 (dd, J ) 8.2, 5.1 Hz, 2H, phen), 5.84 (s, 2H, HCdCH), 2.32
(s, 3H, CH3), 1.89 (s, 3H, CH3).
Synthesis of [Re{OC(O)CHdCHC(O)OH}(CO)3(phen)] (6b).
Compound 6′ (0.022 g, 0.034 mmol) was dissolved in THF (10
mL), and the light orange solution was stirred at room temperature
for 5 h. The solvent was evaporated under reduced pressure to a
volume of 5 mL and addition of hexane (15 mL) caused the
precipitation of a yellow solid, which was washed with hexane (2
× 10 mL) and diethyl ether (2 × 10 mL). Yield: 0.018 g (91%).
1
IR (THF, cm-1): 2025 vs, 1924 s, 1905 s (νCO). H NMR (CD2-
Cl2): δ 9.48 (dd, J ) 5.1, 1.4 Hz, 2H, phen), 8.66 (dd, J ) 8.2,
1.4 Hz, 2H, phen), 8.09 (s, 2H, phen), 7.95 (dd, J ) 6.2, 5.1 Hz,
2H, phen), 5.80, 5.71 (AB system, 2H, HCdCH). Anal. Calcd for
C19H11N2O7Re: C, 40.35; H, 1.96; N, 4.95. Found: C, 39.98; H,
2.21; N, 5.14.
Synthesis of [Re{SCN(p-Tol)(ONCMe2)}(CO)3(bipy)] (5). (p-
Tol)NCS (0.012 mL, 0.096 mmol) was added to a solution of [Re-
(ONCMe2)(CO)3(bipy)] (1) (0.050 g, 0.096 mmol) in THF (15 mL),
and the mixture was stirred for 8 h. The color of the solution
changed from red to yellow. The solvent was evaporated under
reduced pressure to a volume of 5 mL and addition of hexane (20
mL) caused the precipitation of a yellow microcrystalline solid,
which was washed with hexane (2 × 10 mL) and diethyl ether (2
× 5 mL). Slow diffusion of hexane (10 mL) into a concentrated
solution of 5 in CH2Cl2 at room temperature afforded yellow
crystals, one of which was employed for an X-ray analysis. Yield:
0.054 g (87%). IR (CH2Cl2, cm-1): 2017 vs, 1917 s, 1898 s (νCO).
1H NMR (CD2Cl2): δ 8.98 (m, 2H, bipy), 8.44 (m, 2H, bipy), 8.02
(m, 2H, bipy), 7.50 (m, 2H, bipy), 6.82, 6.79, 6.40, 6.37 (q,
AA′BB′system, 4H, p-Tol), 2.15 (s, 3H, CH3), 2.12 (s, 3H, CH3),
2.03 (s, 3H, CH3). 13C{1H} NMR (CD2Cl2): δ 163.3 (CdN), 157.6,
155.7, 150.8, 141.13, 133.0, 131.0, 129.4, 125.6, 123.9 (bipy and
p-Tol), 24.2 (CH3, p-Tol), 22.8, 19.7 (2 × CH3). Low solubility of
5 precluded the observation of the weak Re-CO signals. Anal.
Calcd for C24H21N4O4ReS:C, 44.44; H, 3.27; N, 8.64. Found: C,
44.76; H, 3.61; N, 8.55.
Synthesis of [Re{C(CN)2C(CN)2ONCMe2}(CO)3(phen)] (7).
Tetracyanoethylene (0.012 g, 0.096 mmol) was added to a solution
of [Re(ONCMe2)(CO)3(phen)] (2) (0.050 g, 0.096 mmol) in THF
(15 mL) at -78 °C. Immediately, the color of the solution changed
from red to yellow. The solvent was evaporated under reduced
pressure to a volume of 5 mL and addition of hexane (15 mL)
caused the precipitation of a yellow solid, which was washed with
hexane (2 × 10 mL). Slow diffusion of hexane (10 mL) into a
concentrated solution of 7 in CH2Cl2 at -20 °C afforded yellow
crystals, one of which was employed for an X-ray analysis. Yield:
0.062 g (88%). IR (CH2Cl2, cm-1): 2216w, 2199w (νCN); 2033
vs, 1931 s (νCO). 1H NMR (CD2Cl2): δ 9.45 (dd, J ) 5.1, 1.4 Hz,
2H, phen), 8.69 (dd, J ) 8.2, 1.4 Hz, 2H, phen), 8.14 (s, 2H, phen),
8.00 (dd, J ) 8.2, 5.1 Hz, 2H, phen), 2.01 (s, 3H, CH3), 1.97 (s,
3H, CH3). Anal. Calcd for C24H14N7O4Re‚CH2Cl2: C, 40.82; H,
2.19; N, 13.33. Found: C, 41.16; H, 1.90; N, 13.82.
Synthesis of [Re{C(CO2Me)CdC(CO2Me)(ONCMe2}(CO)3-
(phen)] (8). DMAD (0.012 mL, 0.097 mmol) was added to a
solution of 2 (0.050 g, 0.096 mmol) in THF (15 mL). The color of
the solution changed immediately from red to light brown. The
solvent was evaporated under reduced pressure to a volume of 5
mL, and addition of hexane (15 mL) caused the precipitation of a
brown solid, which was washed with hexane (2 × 10 mL) and
diethyl ether (2 × 10 mL). Yield: 0.047 g (74%). IR (THF, cm-1):
2020vs, 1917s, 1895s (νCO). 1H NMR ((CD3)2CO): δ 9.45 (m, 2H,
phen), 9.00 (m, 2H, phen), 8.36 (s, 2H, phen), 8.19 (dd, J ) 8.1,
5.1 Hz, 2H, phen), 3.77 (s, 3H, CO2CH3), 3.34 (s, 3H, CO2CH3),
1.06 (s, 3H, CH3), 0.66 (s, 3H, CH3).
Synthesis of [Re{OC(O)CHdCHC(O)ONCMe2}(CO)3(phen)]
(6a). To a solution of [Re(ONCMe2)(CO)3(phen)] (2) (0.050 g,
0.096 mmol) in THF (15 mL), maleic anhydride (0.010 g, 0.100
mmol) was added and the mixture was stirred for 12 h. The color
of the solution changed from red to yellow. The solvent was
evaporated under reduced pressure to a volume of 5 mL, and
addition of hexane (20 mL) caused the precipitation of a yellow
solid, which was washed with hexane (2 × 10 mL). Slow diffusion
of diethyl ether (20 mL) into a concentrated solution of 6a in CH2-
Cl2 at room temperature afforded yellow crystals, one of which
was employed for an X-ray determination. Yield: 0.041 g (68%).
Synthesis of [Re{NH2C(CO2Me)C(CO2Me)(O)}(CO)3(phen)]
(9). Attempts to crystallize compound 8 at room temperature by
slow diffusion of hexane (15 mL) in a concentrated solution of 8
in CH2Cl2 afforded yellow crystals. One of these crystals was
employed for an X-ray determination which showed a hydrolysis
reaction had occurred affording compound 9. Yield: 0.011 g (18%).
1
IR (THF, cm-1): 2019 vs, 1917 s, 1891 s (νCO). H NMR (CD2-
Cl2): δ 9.48 (dd, J ) 5.1, 1.4 Hz, 2H, phen), 8.63 (dd, J ) 8.3,
1.4 Hz, 2H, phen), 8.07 (s, 2H, phen), 7.91 (dd, J ) 8.3, 5.1 Hz,
2H, phen), 5.85, 5.57 (AB system, 2H, HCdCH), 2.06 (s, 3H, CH3),
1.92 (s, 3H, CH3). Anal. Calcd for C22H16N3O7Re: C, 42.58; H,
2.60; N, 6.67. Found: C, 41.26; H, 2.69; N, 6.75.
1
IR (THF, cm-1): 2020vs, 1917s, 1895s (νCO). H NMR ((CD3)2-
CO): δ 9.44 (dd, J ) 5.2, 1.3 Hz, 2H, phen), 8.90 (dd, J ) 8.2,
1.3 Hz, 2H, phen), 8.25 (s, 2H, phen), 8.07 (dd, J ) 8.2, 5.2 Hz,
2H, phen), 4.68 (s, br, 1H, NH of NH2), 3.28 (s, 3H, CO2CH3),
3.10 (s, br, NH of NH2), 2.82 (s, 3H, CO2CH3). Anal. Calcd for
C21H16N3O8Re: C, 40.38; H, 2.58; N, 6.73. Found: C, 40.63; H,
2.49; N, 6.49.
Synthesis of [Re{NH2C(CO2Me)C(CO2Me)(O)}(CO)3(bipy)]
(10). To a solution of 1 (0.050 g, 0.096 mmol) in THF (15 mL),
DMAD (12 µL, 0.097 mmol) was added and the mixture was stirred
at room temperature for 8 h. The color of the solution changed
Synthesis of [Re{N(OH)CMe2}(CO)3(phen)][OC(O)CHd
CHC(O)OH] (6′). To a solution of [Re(ONCMe2)(CO)3(phen)] (2)
(0.020 g, 0.037 mmol) in THF (10 mL) maleic acid (0.004 g, mmol)
was added. The color of the solution changed immediately from
red to pale orange, and the mixture was stirred at room temperature
for 15 min. The solvent was evaporated under reduced pressure to
a volume of 5 mL, and addition of hexane (15 mL) caused the
precipitation of a yellow solid, which was washed with hexane (2
Inorganic Chemistry, Vol. 46, No. 7, 2007 2843

Cuesta et al.
Table 1. Selected Crystal, Measurement and Refinement Data for Compounds 1, 3, 4, 5, 6a, 7, 9, and 10.
1
3
4
5
formula
fw
C16H14N3O4Re
498.50
C50H27BF24N3O4Re
1386.76
C26H21N4O5Re°0.25CH2Cl2
676.90
C24H21N4O4ReS
647.71
cryst syst
space group
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
Z
monoclinic
P21
6.665(2)
14.740(5)
8.779(3)
90
91.498(6)
90
862.2(5)
2
monoclinic
P21/n
20.177(5)
13.770(3)
20.177(5)
90
111.696(3)
90
5209(2)
triclinic
P1h
9.984(3)
11.569(4)
13.526(5)
103.207(6)
11.490(5)
95.130(6)
1389.3(8)
2
monoclinic
P21/n
6.559(5)
18.448(14)
22.006(17)
90
90.758(14)
90
2663(4)
4
4
F(000)
D
476
2.412
2704
1.768
661
1.618
1264
1.616
calcd, g cm-3
radiation (λ, Å)
Mo KR, 0.71073
7.071
Mo KR, 0.71073
2.467
Mo KR, 0.71073
4.462
Mo KR, 0.71073
4.677
µ, mm-1
cryst size, mm3
T, K
0.22 × 0.17 × 0.13
0.45 × 0.11 × 0.07
0.44 × 0.35 × 0.32
0.31 × 0.10 × 0.04
296(2)
296(2)
293(2)
296(2)
θ limits, deg
2.32-23.27
-7/7, -16/16, -9/5
3813
2430
SADABS
219/1
1.22-23.31
-22/22, -15/15, -21/22
23 260
7506
SADABS
741/0
1.84-23.26
-11/11, -12/12, -11/14
6026
3877
SADABS
335/0
1.44-23.26
-7/6, -16/20, -22/24
11 795
3800
SADABS
311/0
min/max h, k, l
collected reflns
unique reflns
absorption
params/restraints
GOF on F2
1.016
1.012
1.023
1.163
R1 (on F, I > 2σ(I))
wR2 (on F2, all data)
max/min ∆F, e Å-3
0.0171
0.0420
0.532 and -0.337
0.0431
0.1238
0.907 and -0.977
0.0288
0.0861
1.863 and -1.863
0.0724
0.1791
1.846 and -3.889
6a
7
9
10
formula
fw
C22H16N3O7Re
620.58
C24H12N7O4Re°CH2Cl2
735.55
C21H20N3O10Re
660.61
C19H16N3O8Re
600.55
cryst syst
space group
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
Z
monoclinic
C2/c
24.471(14)
10.101(5)
20.223(10)
90
129.629(7)
90
4480(4)
triclinic
P1h
Monoclinic
P 21/c
9.2206(3)
20.4832(8)
13.3466(6)
90
94.792(2)
90
2511.9(2)
4
Triclinic
P -1
7.7302(15)
11.292(2)
16.019(3)
88.46(3)
77.65(3)
76.79(3)
1329.5(5)
2
8.374(3)
10.639(4)
13.446(5)
103.459(7)
106.804(7)
105.346(7)
1041.9(7)
2
8
F(000)
D
2400
1.840
712
1.837
1288
1.747
580
1.914
calcd, g cm-3
radiation (λ, Å)
Mo KR, 0.71073
5.474
Mo KR, 0.71073
4.817
Cu KR, 1.54184
9.978
Mo KR, 0.71073
5.883
µ, mm-1
cryst size, mm3
T, K
0.27 × 0.15 × 0.06
0.20 × 0.10 × 0.07
0.27 × 0.15 × 0.17
0.15 × 0.07 × 0.04
296(2)
293(2)
293(2)
296(2)
θ limits, deg
1.86-23.32
-25/31, -11/9, -22/22
9651
3215
SADABS
300/0
1.30-25.68
-9/9, -13/13, -18/19
7131
4860
multi scan
355/0
4.0 to 68.2
-10/11, 0/23, 0/16
21166
4387
SORTAV
331/12
1.68 to 23.41
-9/9, -11/11, -8/14
4738
2998
SADABS
282/0
min/max h, k, l
collected reflns
unique reflns
absorption
params/restraints
GOF on F2
1.020
1.089
1.110
1.021
R1 (on F, I > 2σ(I))
wR2 (on F2, all data)
max/min ∆F, e Å-3
0.0240
0.0542
0.694 and -0.564
0.0408
0.1057
1.890 and -1.728
0.0544
0.1638
1.130 and -1.271
0.0361
0.0546
0.808 and -0.869
from red to yellow. The solvent was evaporated under reduced
pressure to a volume of 5 mL, and addition of hexane (20 mL)
caused the precipitation of a yellow solid, which was washed with
diethyl ether (2 × 5 mL). Slow diffusion of diethyl ether (20 mL)
into a concentrated solution of 10 in CH2Cl2 at room temperature
afforded crystals, one of which was employed for an X-ray
determination. Yield: 0.037 g, 64%. IR (CH2Cl2, cm-1): 2026vs,
Crystal Structure Determination for Compounds 1, 3, 4, 5,
6a, 7, 9, and 10. General Description. A suitable crystal was
attached to a glass fiber and transferred to a Bruker AXS SMART
1000 (Nonius Kappa CCD for 9) diffractometer with graphite-
monochromatized Mo KR (Cu KR for 9) X-ray radiation and a
CCD area detector. One hemisphere of the reciprocal space was
collected in each case. Raw frame data were integrated with the
SAINT16 (HKL Denzo and Scalepack17 for 9) program. The
1
1919s (νCO). H NMR ((CD3)2CO): δ 9.04 (m, 2H, bipy), 8.56
(m, 2H, bipy), 8.25 (m, 2H, bipy), 7.68 (m, 2H, bipy), 4.63 (s, br,
1H, NH of NH2), 3.38 (s, 3H, CO2CH3), 3.20 (s, br, 1H, NH of
NH2), 2.98 (s, 3H, CO2CH3). Anal. Calcd for C19H16N3O8Re: C,
38.00; H, 2.69; N, 7.00. Found: C, 37.61; H, 2.77; N, 7.19.
(16) SAINT+. SAX area detector integration program. Version 6.02; Bruker
AXS, Inc.: Madison, WI, 1999.
(17) Otwinowski, Z.; Minor, W. Methods Enzymol. 1997, 276, 307.
2844 Inorganic Chemistry, Vol. 46, No. 7, 2007

Mononuclear Re(I) Oximato Complexes
structures were solved by direct methods with SHELXTL.18 An
empirical absorption correction was applied with the program
SADABS19 (SORTAV20 for 9). All non-hydrogen atoms were
refined anisotropically. Hydrogen atoms were set in calculated
positions and refined as riding atoms. Drawings and other calcula-
tions were made with SHELXTL (ORTEP21 and X-Seed20 for 9
and 10). Crystal and refinement details are collected in Table 1.
Acknowledgment. We thank Ministerio de Ciencia y
Tecnolog´ıa (grants CTQ2006-08924, MAT2006-1997,
BQU2003-08649, and CTQ2006-07036/BQU) and Junta de
Castilla y Leo´n (Grant No. VA012C05) for support of this
work, and Ministerio de Educacio´n y Ciencia for a FPU
predoctoral fellowship (to L.C.) and for Ramo´n y Cajal
contracts (to D. Morales and L.R.).
(18) Sheldrick, G. M. SHELXTL, An integrated system for solVing, refining,
and displaying crystal structures from diffraction data. Version 5.1;
Bruker AXS, Inc.: Madison, WI, 1998.
(19) Sheldrick, G. M. SADABS, Empirical Absorption Correction Program;
University of Go¨ttingen: Go¨ttingen, Germany, 1997.
Supporting Information Available: X-ray crystallographic data
for compounds 1, 3, 4, 5, 6a, 7, 9, and 10 as CIF. This material is
available free of charge via the Internet at http://pubs.acs.org.
(20) Blessing, R. H. Acta Crystallogr. 1995, A51, 33.
(21) Farrugia, L. J. J. Appl. Crystallogr. 1997, 30, 565.
(22) Barbour, L. J. J. Supramol. Chem. 2001, 1, 189.
IC062168C
Inorganic Chemistry, Vol. 46, No. 7, 2007 2845