Controlled acidolysis of hexacarbonyltris(μ-alkoxo)dirhenium(I) anions: Facile synthesis of hexacarbonylbis(μ-alkoxo)-[μ-1,1′-bis(diphenylphosphino)ferrocene] dirhenium(I) complexes and nonacarbonyltris(μ-methoxo)(μ3-methoxo)trirhenium(I)

Article abstract of DOI:10.1021/om970614l

The complexes [Re₂(μ-OR)₂(μ-dppf)(CO)₆] (R = H, 1; Me, 2; Et, 3; Ph, 4) were synthesized by the controlled acidolysis of the anions [Re₂(μ-OR)₃(CO)₆]^- (R = H, Me, Et) and [Re₂(μ-OH)(μ-OPh)₂(CO)₆]^- (5), respectively, in the presence of dppf (1,1′-bis(diphenylphosphino)-ferrocene). The dppf ligands in complexes 1-4 undergo a twisting motion in solution at room temperature, which, in the case of 3, is correlated with the restricted rotation of the ethyl groups about the O-CH₂ bonds. Complex 3 is an interesting example of an organometallic complex in which the two exchanging positions of the methylen protons of an ethyl group are nonequivalent, while the exchanging positions of the methyl group are equivalent. Controlled acidolysis of [Re₂(μ-OMe)₃(CO)₆]^- under 1 atm of CO pressure affords the complex [Re₃(μ-OMe)₃(μ₃-OMe)(CO) ₉]^- (6), which consists of Re₃ triangle held together by one face-capping and three bridging methoxo groups, with no Re-Re bonds. The crystal structures of 1, 3, 5, and 6, were determined by single-crystal X-ray diffraction analysis. The synthetic relationship of dirhenium-dialkoxo, dirhenium-trialkoxo, and trirhenium-tetraalkoxo entities is established.

Full text of DOI:10.1021/om970614l

Organometallics 1998, 17, 173-181
173
Con tr olled Acid olysis of
Hexa ca r bon yltr is(µ-a lk oxo)d ir h en iu m (I) An ion s: F a cile
Syn th esis of Hexa ca r bon ylbis(µ-a lk oxo)-
[µ-1,1′-bis(d ip h en ylp h osp h in o)fer r ocen e]d ir h en iu m (I)
Com p lexes a n d
Non a ca r bon yltr is(µ-m eth oxo)(µ3-m eth oxo)tr ir h en iu m (I)
Chenghua J iang,† Yuh-Sheng Wen,‡ Ling-Kang Liu,*,‡ T. S. Andy Hor,*,† and
Yaw Kai Yan*,§
Department of Chemistry, Faculty of Science, National University of Singapore,
Kent Ridge, Singapore 119260, Institute of Chemistry, Academia Sinica,
Taipei, Taiwan 11529, and Division of Chemistry, National Institute of Education,
Nanyang Technological University, 469 Bukit Timah Road, Singapore 259756
Received J uly 18, 1997X
The complexes [Re2(µ-OR)2(µ-dppf)(CO)6] (R ) H, 1; Me, 2; Et, 3; Ph, 4) were synthesized
by the controlled acidolysis of the anions [Re2(µ-OR)3(CO)6]- (R ) H, Me, Et) and [Re2(µ-
OH)(µ-OPh)2(CO)6]- (5), respectively, in the presence of dppf (1,1′-bis(diphenylphosphino)-
ferrocene). The dppf ligands in complexes 1-4 undergo a twisting motion in solution at
room temperature, which, in the case of 3, is correlated with the restricted rotation of the
ethyl groups about the O-CH2 bonds. Complex 3 is an interesting example of an
organometallic complex in which the two exchanging positions of the methylene protons of
an ethyl group are nonequivalent, while the exchanging positions of the methyl group are
equivalent. Controlled acidolysis of [Re2(µ-OMe)3(CO)6]- under 1 atm of CO pressure affords
the complex [Re3(µ-OMe)3(µ3-OMe)(CO)9]- (6), which consists of a Re3 triangle held together
by one face-capping and three bridging methoxo groups, with no Re-Re bonds. The crystal
structures of 1, 3, 5, and 6 were determined by single-crystal X-ray diffraction analysis.
The synthetic relationship of dirhenium-dialkoxo, dirhenium-trialkoxo, and trirhenium-
tetraalkoxo entities is established.
In tr od u ction
noteworthy that while the complexes [Re2(µ-OH)2(µ-PP)-
(CO)6] (PP ) dppm, dmpm, dppe, dmpe)2 have been
synthesized by the photolysis of [Re2(µ-PP)(CO)8] in wet
toluene,3 the OEt, OPh, and OCH2CH2Cl analogues
have not been reported.
The synthesis, reactions, and solution dynamics of
rhenium(I) carbonyl alkoxo complexes is a subject of
current interest.1 Much of our attention had been
focused on the diphosphine- and dimethoxo-bridged
complexes [Re2(µ-OMe)2(µ-PP)(CO)6] {PP ) dppf [1,1′-
bis(diphenylphosphino)ferrocene) Ph2P(CH2)nPPh2, n )
1-4), which were synthesized by the oxidative decar-
bonylation of Re2(CO)10 by Me3NO in a mixture of THF
and MeOH, followed by the addition of diphosphine.1b,c
Curiously, this synthetic route cannot be extended to
the synthesis of the analogous complexes [Re2(µ-OR)2(µ-
PP)(CO)6] (R ) H, Et, Ph, CH2CH2Cl).1a,d It is also
It is somewhat surprising that to date there is no
synthetic relationship between the bis(alkoxo)-bridged
complexes [Re2(µ-OR)2(µ-PP)(CO)6] and the well-estab-
lished tris(alkoxo)-bridged complexes [Re2(µ-OR)3-
(CO)6]-.4,5 In this paper, we report the facile synthesis
of the complexes [Re2(µ-OR)2(µ-dppf)(CO)6] (R ) H, 1;
Me, 2; Et, 3; Ph, 4) by the controlled acidolysis of the
complexes [Re2(µ-OH)(µ-OPh)2(CO)6]- (5) and [Re2(µ-
OR)3(CO)6]- (R ) H, Me, Et) in the presence of dppf
(Scheme 1). In order to investigate the stereogeometri-
cal effects of the hydroxide and alkoxide ligands on the
† National University of Singapore.
‡ Academia Sinica.
§ Nanyang Technological University.
X Abstract published in Advance ACS Abstracts, December 15, 1997.
(1) (a) J iang, C. H.; Wen, Y.-S.; Liu, L.-K.; Hor, T. S. A.; Yan, Y. K.
J . Organomet. Chem. 1997, 543, 179. (b) Yan, Y. K.; Chan, H. S. O.;
Hor, T. S. A.; Tan, K. L.; Liu, L.-K.; Wen, Y.-S. J . Chem. Soc., Dalton
Trans. 1992, 423. (c) Low, P. M. N.; Yong, Y. L.; Yan, Y. K.; Hor, T. S.
A.; Lam, S.-L.; Chan, K. K.; Wu, C.; Au-Yeung, S. C. F.; Wen, Y.-S.;
Liu, L.-K. Organometallics 1996, 15, 1369. (d) Hor, T. S. A.; Lam, C.
F.; Yan, Y. K. Bull. Singapore Natl. Inst. Chem. 1991, 19, 115. (e)
Mandal, S. K.; Ho, D. M.; Orchin, M. Organometallics 1993, 12, 1714.
(f) Mandal, S. K.; Ho, D. M.; Orchin, M. Inorg. Chem. 1991, 30, 2244.
(g) Herrmann, W. A.; Egli, A.; Herdtweck, E.; Alberto, R.; Baumga¨rtner,
F. Angew. Chem., Int. Ed. Engl. 1996, 35, 432.
(2) Abbreviations used: dppm ) bis(diphenylphosphino)methane,
dmpm ) bis(dimethylphosphino)methane, dppe ) 1,2-bis(diphenylphos-
phino)ethane, dmpe ) 1,2-bis(dimethylphosphino)ethane.
(3) Lee, K.-W.; Pennington, W. T.; Cordes, A. W.; Brown, T. L.
Organometallics 1984, 3, 404.
(4) Ioganson, A. A.; Lokshin, B. V.; Kolobova, E. E.; Anisimov, K.
N. J . Gen. Chem. 1974, 20, 20. (Translated from Zh. Obshch. Khim.
1974, 44, 23.)
(5) (a) Ginsberg, A. P.; Hawkes, M. J . J . Am. Chem. Soc. 1968, 90,
5930. (b) Ciani, G.; D’Alfonso, G.; Freni, M.; Romiti, P.; Sironi, A. J .
Organomet. Chem. 1978, 152, 85. (c) Freni, M.; Romiti, P. Atti Accad.
Naz. Lincei, Mem. Cl. Sci. Fis. Mat. Nat. Rend. 1973, 55, 515.
S0276-7333(97)00614-6 CCC: $15.00 © 1998 American Chemical Society
Publication on Web 01/19/1998

174 Organometallics, Vol. 17, No. 2, 1998
J iang et al.
Sch em e 1
dirhenium core, the variable-temperature 1H NMR
behavior of 3 was studied and the crystal structures of
1 and 3 determined and compared with that of 2.1b We
also report the crystal structures of 5 and [NEt4][Re3-
(µ-OMe)3(µ3-OMe)(CO)9] (6), the latter of which was
obtained from the acidolysis of [Re2(µ-OMe)3(CO)6]-
under 1 atm of CO gas. The structure of 5 would reveal
any structural deformities imposed by the mixed alkox-
ide ligands, while that of 6 provides a direct comparison
of a Re3 with the Re2 entities.
Resu lts a n d Discu ssion
Syn th esis of th e Dir h en iu m An ion s [Re2(µ-OR)3-
(CO)6]- (R ) H, Me, Et) a n d [Re2(µ-OH)(µ-OP h )2-
(CO)6]-. The tris(alkoxo)-bridged complexes [Re2(µ-
OR)3(CO)6]- (R ) H, Me, Et) are easily synthesized by
the reaction of ReBr(CO)5 with the corresponding base,
NaOR, in a mixture of THF and ROH at room temper-
ature. We found this method more convenient than
those involving refluxing conditions using ReBr(CO)5 or
Re2(CO)10 in alcoholic solutions of NaOR or KOH.4,5
Surprisingly, the complex [Re2(µ-OPh)3(CO)6]- was not
obtained in the analogous reaction with NaOPh under
anhydrous conditions. A complex mixture of numerous
products was obtained instead. When wet THF ([H2O]:
[ReBr(CO)5]:[OPh-] ca. 1:2:6) was used as the solvent,
however, the novel mixed-bridge complex [Re2(µ-OH)-
(µ-OPh)2(CO)6]- (5) was obtained in good yield. Increas-
ing the water content of the reaction mixture ([H2O]:
[ReBr(CO)5]:[OPh-] ca. 5:1:3) resulted in the formation
of [Re2(µ-OH)3(CO)6]- as the main product.
Cr ysta l Str u ctu r e of [NEt4][Re2(µ-OH)(µ-OP h )2-
(CO)6]- (5). The molecular structure of the complex
anion (Figure 1) consists of two [Re(CO)3] fragments
bridged by two OPh- ligands and one OH- ligand. To
our knowledge, complex 5 is the first structurally well-
defined mixed-bridge [Re2(µ-OR)x(µ-OR′)y(CO)6]- (x + y
) 3) complex that is synthesized in good yield.6 There
have been two reports of the X-ray diffraction analysis
of the complexes [Re2(µ-OMe)x(µ-OEt)y(CO)6]- (x + y )
3).7 In these cases, complete formulation of the com-
F igu r e 1. Crystal structure of [Re2(µ-OH)(µ-OPh)2(CO)6]-
(5; 50% probability ellipsoids).
plexes was not successful due to the severe disorder of
the alkoxo ligands.
The Re atoms in 5 exhibit a distorted octahedral
geometry and fulfil the 18-electron rule without the need
for a direct metal-metal bond. The Re‚‚‚Re nonbonding
distance of 3.152 Å is essentially identical to that in [Re2-
(µ-OPh)3(CO)6]- (3.154 Å).6c The Re-(µ-O)-Re bond
angles for the OPh- ligands (93.6(3)° and 94.3(3)°) are
somewhat smaller than that for the OH- bridge (95.5-
(4)°). This corresponds to a longer average Re-O(Ph)
bond length (2.156(8) Å) compared to the average Re-
O(H) bond length (2.128(9) Å). Comparable bond lengths
and angles have been observed in [Re2(µ-OPh)3(CO)6]-
and [Re2(µ-OH)3(CO)6]-.6a,c The Re-CO bond lengths
are identical within experimental error. The weaker
Re-O(Ph) bonds are consistent with the experimental
observation that the formation of the trihydroxo or
mixed-ligand hydroxo/phenoxo complex is favored over
that of the triphenoxo complex.
Syn th esis a n d Ch a r a cter iza tion of [Re2(µ-OR)2-
(µ-d p p f)(CO)6] (R ) H, 1; Me, 2; Et, 3; P h , 4).
Complexes 1-4 were synthesized by the stoichiometric
protonation of [Re2(µ-OR)3(CO)6]- (R ) H, Me, Et) and
[Re2(µ-OH)(µ-OPh)2(CO)6]- (5), respectively, by p-tolu-
enesulfonic acid (TsOH), followed by attack of dppf
(Scheme 1). In all cases, it was possible to selectively
replace one of the bridging OR- groups with the diphos-
phine. It is also noteworthy that in 5 the OH- group is
preferentially substituted over the bulkier OPh- groups.
This may be attributed to the higher basicity of the
hydroxide, which renders it more susceptible to acid
attack.
(6) Well-refined crystal structures have been reported for the
following homobridged [Re2(µ-OR)3(CO)6]- complexes: (a) R ) H.
Alberto, R.; Egli, A.; Abram, U.; Hegetschweiler, K.; Gramlich, V.;
Schubiger, P. A. J . Chem. Soc., Dalton Trans. 1994, 2815. (b) R ) Me.
Herrmann, W. A.; Mihalios, D.; O¨ fele, K.; Kiprof, P.; Belmedjahed, F.
Chem. Ber. 1992, 125, 1795. (c) R ) Ph. Beringhelli, T.; Ciani, G.;
D’Alfonso, G.; Sironi, A.; Freni, M. J . Chem. Soc., Dalton Trans. 1985,
1507.
(7) (a) Kolobova, N. E.; Zdanovich, V. I.; Lobanova, I. A.; Andrianov,
V. G.; Struchkov, Yu. T.; Petrovskii, P. V. Bull. Acad. Sci. USSR, Div.
Chem. Sci. 1984, 33, 871. (b) Ciani, G.; Sironi, A.; Albinati, A. Gazz.
Chim. Ital. 1979, 109, 615.

Controlled Acidolysis of [Re2(µ-OR)3(CO)6]-
Organometallics, Vol. 17, No. 2, 1998 175
Ta ble 1. Com p a r ison of Selected Str u ctu r a l
P a r a m eter s of [Re2(µ-OR)2(µ-d p p f)(CO)6] (R ) H, 1;
Me, 2; Et, 3)
Re‚‚‚Re
distance
(Å)
average
θ
(O-Re-O) in
ω
φ
R
complex
(deg)a {Re2O2} core (deg) (deg)b (deg)c (deg)d
1
2
3
3.42
3.40
3.43
29.7
30.7
26.3
70.7(2)
71.3(2)
72.8(3)
86.1
85.9
84.0
46.1 121.8
53.5 122.6
50.8 123.7
a
θ is the fold angle of the {Re2O2} core:
b
ω is the angle by which the two Cp rings of the dppf ligand are
twisted from the P, P eclipsed position. c φ is the angle made by
the projection of the Cp···Cp axis of dppf onto the Re···Re axis.
is the average Cipso(Cp)-P-Re angle.
d
R
F igu r e 2. Crystal structure of Re2(µ-OH)2(µ-dppf)(CO)6 (1;
50% probability ellipsoids).
The ability of the dppf ligand to fine-tune its confor-
mation to adjust to the steric demands of its molecular
environment is reflected by the variation in the struc-
tural parameters listed in Table 1. The parameter that
is most sensitive seems to be the angle (φ) made by the
projection of the Cp‚‚‚Cp axis of dppf onto the Re‚‚‚Re
axis. It is also evident that the fold angle θ of the
{Re2O2} core for the ethoxo complex 3 is significantly
smaller than those of complexes 1 and 2. The variations
in θ and φ are, however, not monotonic with the steric
bulk of the alkoxo bridges. On the other hand, the
strain on the Cipso(Cp)-P-Re angle appears to increase
with increasing bulk of the alkoxo groups.
There is a disorder of the methyl groups of the ethoxo
ligands in 3, as shown in Figure 3. The structure was
refined with two positions for the methyl carbon (C(20)
and C(20′)) having occupancies of 60% and 40%, respec-
tively. Both positions are directed away from the phenyl
ring (C(11)-C(16)).
F igu r e 3. Crystal structure of Re2(µ-OEt)2(µ-dppf)(CO)6
(3; 30% probability ellipsoids).
1H NMR Sp ectr oscop ic Stu d ies. The Cp reso-
While 1 was obtained in high yield from the acidolysis
reaction carried out in THF, the yield of 2 was very low
in THF. Infrared spectroscopy indicated that the pre-
dominant species present in the latter reaction mixture
were probably fac-[ReX(CO)3(η2-dppf)]n+ complexes (X
) OTs (n ) 0) or THF (n ) 1)). The yield of 2 increased
dramatically when a mixture of CHCl3 and MeOH was
used as the solvent for the acidolysis reaction.
A mixture of chloroform and ethanol was used as the
solvent for the synthesis of complex 3. The yield of this
complex was, however, significantly lower than those
for 1 and 2. This is probably due to the bulkiness of
the OEt- group, which hinders both the approach of the
acid molecules and the coordination of dppf.
Cr ysta l Str u ctu r es of 1 a n d 3. The crystal struc-
tures of 1 and 3 are depicted in Figures 2 and 3,
respectively. Complex 3 possesses a crystallographic C2
axis (passing through the Fe atom and the center of the
{Re2O2} core), so that only half of the molecule is unique.
Both 1 and 3 are structurally similar to 2,1b with dppf
and two OR- ligands bridging two facial Re(I) tricar-
bonyl moieties. The bulk of the dppf bridge forces the
Cp‚‚‚Cp axis8 to twist significantly with respect to the
Re‚‚‚Re axis and the two Re coordination planes to fold
along the O‚‚‚O axis away from the diphosphine. A
comparison of selected structural parameters of com-
plexes 1-3 is provided in Table 1.
1
nances in the room temperature H NMR spectra of 1,
3, and 4 comprise two extremely broad signals in the
region 5.5-3.5 ppm. This pattern is very similar to that
1
observed in the room temperature H NMR spectrum
of 2, which has been interpreted in terms of an exchange
of Cp protons due to the twisting motion of the bridging
dppf ligand with respect to the axis joining the two
bridged Re atoms.9
An interesting feature of the 1H NMR spectrum of
complex 3 (Figure 4a) is that the signal due to the
methylene protons of the ethyl group takes the form of
a broad singlet (at 4.65 ppm) instead of the familiar
quartet, suggesting fluxionality involving the methylene
protons. The signal for the CH3 groups is, however, in
the expected form of a triplet at 1.45 ppm. The 1H NMR
spectrum recorded at 243 K (Figure 4b) shows two well-
resolved quartets10 attributable to the methylene pro-
tons at 4.44 and 4.86 ppm. At this temperature, the
Cp signals are also resolved into four sharp singlets at
1
3.00, 3.88, 4.19 and 5.74 ppm. These Cp H chemical
shifts are very close to those observed for 2 at 228 K,
for which the large range of chemical shifts has been
(9) Lam, S.-L.; Cui, Y.-X.; Au-Yeung, S. C. F.; Yan, Y.-K.; Hor, T. S.
A. Inorg. Chem. 1994, 33, 2407.
(10) The term “quartets” is used here since the methylene proton
signals resemble the 1:3:3:1 quartet expected in the first-order 1H NMR
spectrum of an ethyl group. The methylene signals observed here are
not first order, however, as discussed in the subsequent paragraph of
the text.
(8) In this paper, Cp is used as the abbreviation for the substituted
cyclopentadienyl ring, C5H4, rather than the conventional C5H5.

176 Organometallics, Vol. 17, No. 2, 1998
J iang et al.
F igu r e 6. The conformer of Re2(µ-OEt)2(µ-dppf)(CO)6 (3)
with endo methyl groups.
Sch em e 2
F igu r e 4. 1H NMR spectra of Re2(µ-OEt)2(µ-dppf)(CO)6 (3)
to Ha/Ha′ and Hb/Hb′, respectively. The ethyl protons
at 243 K can, therefore, be described as an ABX3 spin
system, assuming that the methyl group can still rotate
freely at this temperature. This is consistent with the
second-order features observed in the methylene proton
signals: the lines in the quartets do not have the 1:3:
3:1 intensity ratio, and additional lines which appear
as shoulders are apparently present.11 The Ha/Ha′ and
Hb/Hb′ positions are exchanged when the dppf bridge
twists into the enantiomeric conformation (see Scheme
2), with the concomitant turning of the two ethyl groups
toward the phenyl rings (C(11)-C(16) and C(11a)-
C(16a), respectively). Since the two exchanging posi-
tions for each of the methyl groups are equivalent, the
methyl resonance is unaffected by temperature varia-
tions. Similar arguments may be put forward for the
slow exchange of conformers with only endo methyl
groups (Figure 6).
Both the exo and endo conformers of complex 3 can,
in principle, co-exist in solution, since the conformers
coexist in the ratio of 60:40 in the crystal structure of
the complex. Curiously, however, the 1H NMR spec-
trum of 3 at 243 K indicates the presence of only one
major conformer (since each conformer is expected to
give rise to two methylene proton signals and four Cp
proton signals). Interconversion of the exo and endo
conformers is unlikely in solution at room temperature
at (a) 300 K and (b) 243 K.
F igu r e 5. The conformer of Re2(µ-OEt)2(µ-dppf)(CO)6 (3)
with exo methyl groups.
attributed to ring current effects from the phenyl groups
of the dppf ligand.9 Thus, the variable-temperature
NMR behavior of the Cp protons can be attributed solely
to the freezing-out of the twisting motion of the bridging
dppf ligand at lower temperatures, similar to that
observed in complex 2.9 The triplet signal due to the
terminal methyl groups shows no noticeable change as
the temperature is lowered.
Assuming that the crystal structure of complex 3
(with both the methyl groups in exo positions (Figure
5)) corresponds closely with that of one of the intercon-
verting conformers of the complex in solution, the two
methylene quartets observed at 243 K can be assigned
(11) The methylene proton signals at 243 K were simulated using
the program DSYMPC (see: Ha¨gele, G.; Spiske, R.; Ho¨ffken, H. W.;
Lenzen, T.; Weber, U.; Goudetsidis, S. Phosphorus Sulfur 1993, 77,
262) on a Pentium PC. Good agreement with the observed spectrum
was obtained with the following parameters: 2J (HaHb) ) 11.0 Hz,
3J (HaH3C) ) 3J (HbH3C) ) 6.5 Hz, line width ) 5.0 Hz.

Controlled Acidolysis of [Re2(µ-OR)3(CO)6]-
Organometallics, Vol. 17, No. 2, 1998 177
and below, since rotation of the methyl groups from the
exo to the endo positions is severely hindered by the
equatorial CO groups (C(2)-O(2) and C(2a)-O(2a)).
This was established by calculating the theoretical
position of C(20) when the methyl group is being rotated
past the carbonyl group C(2a)-O(2a), i.e., when the
torsional angle C(20)-C(10)‚‚‚Re(1a)-C(2a) is 0.0°
(C(10)-C(20) bond length set at 1.540 Å and O(10)-
C(10)-C(20) set at 114.0°, cf. the measured O(10)-
C(10)-C(20) of 113.9°). At this position (fractional
coordinates 0.82791, 0.11117, 0.53613), the C(20)‚‚‚C-
(2a) distance is 2.69 Å, which is much shorter than the
sum of the van der Waals radii of two carbon atoms12
(3.70 Å). Although some of the trace “impurity” peaks
in the spectrum could possibly be assigned to the minor
conformer, this assignment cannot be made with cer-
tainty since the minor component that gave rise to these
peaks has so far eluded isolation.
Acid olysis of [Re2(µ-OMe)3(CO)6]- in th e P r es-
en ce of Mon od en ta te Liga n d s. The successful syn-
thesis of 1-4 by the controlled acidolysis route prompted
us to attempt the analogous synthesis of the complexes
[Re2(µ-OMe)2(CO)6(PPh3)2] and [Re2(µ-OMe)2(CO)8] by
using PPh3 and CO in place of dppf. An earlier attempt
to synthesize [Re2(µ-OMe)2(CO)6(PPh3)2] by applying the
original synthetic strategy for 2, i.e., by the oxidative
decarbonylation of Re2(CO)10 by Me3NO in a mixture
of THF and MeOH, followed by addition of PPh3, was
unsuccessful.1c There has also been no report of the
complex [Re2(µ-OMe)2(CO)8], although the complexes
[Re2(µ-X)2(CO)8] (X ) halides) are well-established.13
Acid olysis of [Re2(µ-OMe)3(CO)6]- in th e P r es-
en ce of P P h 3. The reaction proceeded very slowly,
with little conversion of starting materials even after 4
h (cf. the analogous reaction with dppf, which is virtu-
ally complete within 1 h). The main product that was
isolated after the reaction had proceeded for 24 h was
fac-[Re(η1-OTs)(CO)3(PPh3)2].
The preferential formation of the mononuclear Re
complex can be explained by the large bulk of PPh3,
which would destabilize the dinuclear {Re2(µ-OMe)2-
(PPh3)2} moiety. Cleavage of the dimer followed by
PPh3 scrambling and attack of TsOH would give the
observed product fac-[Re(η1-OTs)(CO)3(PPh3)2]. It is
noteworthy that the complex [Re2(µ-OH)2(CO)6(py)2] (py
) pyridine) has been synthesized in good yield by
heating η5-indenylrhenium tricarbonyl in wet pyridine
at 50 °C.14 In the latter case, the low steric demand of
the pyridine ligands allows the {Re2(µ-OH)2} core to
remain intact without a third bridging ligand.
Acid olysis of [Re2(µ-OMe)3(CO)6]- in th e P r es-
en ce of CO. Reaction of [Re2(µ-OMe)3(CO)6]- with
TsOH in the presence of CO gas (1 atm) unexpectedly
affords the trinuclear complex anion [Re3(µ-OMe)3(µ3-
OMe)(CO)9]- (6) instead of [Re2(µ-OMe)2(CO)8]. An
increase of the CO pressure to 2 atm led to a mixture
of numerous trace products which are presently uni-
dentified. The formation of 6 suggests that only one
F igu r e 7. Crystal structure of [Re3(µ-OMe)3(µ3-OMe)-
(CO)9]- (6; 50% probability ellipsoids).
methoxo group is cleaved for every three molecules of
[Re2(µ-OMe)3(CO)6]- and that the latter complex is not
carbonylated in the reaction:
3[Re2(OMe)3(CO)6]- + H+
f
2[Re3(OMe)4(CO)9]- + MeOH
The presence of CO gas is, however, necessary for the
synthesis of complex 6, since the complex is not formed
in detectable quantities when the reaction is carried out
under an argon atmosphere. This “catalytic” effect of
CO can be explained by the stabilizing effect of CO upon
the [Re(CO)3] moiety formed by cleavage of a Re-O(Me)
bond (whereby the formation of a [Re(CO)4] moiety
would provide temporary stabilization). Subsequent
attack of a basic terminal or µ2-methoxy group would
eliminate a CO and regenerate the [Re(CO)3] fragment.
Complex 6 has also been reported as a product of the
carbonylation of ammonium perrhenate in methanol at
240 °C under a CO pressure (at room temperature) of
ca. 50 bar.6b The IR and 1H NMR spectroscopic data
for 6 prepared by our method are, however, different
from those reported.15 This prompted us to determine
the crystal structure of complex 6.
Cr ystal Str u ctu r e of [NEt4][Re3(µ-OMe)3(µ3-OMe)-
(CO)9] (6). The crystal structure of the anion 6 consists
of a Re3 triangle held together by one face-capping and
three edge-bridging methoxo groups, with no Re-Re
bonds (Figure 7). Its gross structural features are
similar to those observed in the analogous complexes
[Re3(µ-OH)2(µ-OMe)(µ3-OMe)(CO)9]- 1a and [Re3(µ-OH)3-
(µ3-OH)(CO)9]-,6a whose structures can be described in
terms of a {Re4O4} cube with a missing Re vertex.
However, while there is no significant difference in the
bond lengths between Re and µ- or µ3-OH in [Re3(µ-
OH)3(µ3-OH)(CO)9]- (average 2.157(7) and 2.167(6) Å,
respectively), the Re-(µ3-OMe) bond lengths (average
2.202(5) Å) are significantly longer than the Re-(µ-
(12) Emsley, J . The Elements; Clarendon Press: Oxford, 1989; p 46.
(13) Boag, N. M.; Kaesz, H. D. In Comprehensive Organometallic
Chemistry, 1st ed.; Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.;
Pergamon: Oxford, 1982; Vol. 4, p 161.
(14) Zdanovich, V. I.; Lobanova, I. A.; Petrovskii, P. V.; Batsanov,
A. S.; Struchkov, Yu. T.; Kolobova, N. E. Bull. Acad. Sci. USSR, Div.
Chem. Sci. 1987, 36, 1500.
(15) Herrmann et al. reported νCO bands at 1991 s, 1878 vs, and
1867 vs cm-1 (in THF). The νCO bands we observed generally occur at
higher wavenumbers: 2021 w, 2003 s, 1892 vs, 1878 s(sh) cm-1 (in
THF). In the reported 1H NMR ((CD3)2CO) data, the signals of the
methoxo protons occur at δ 3.70 (s, 3H) and 4.23 (s, 9H), respectively.
We observed the corresponding signals at δ 4.52 and 4.24, respectively,
in the same solvent.

178 Organometallics, Vol. 17, No. 2, 1998
J iang et al.
cubic crystals of [NEt4][Re2(µ-OH)3(CO)6] formed were isolated
by filtration and dried under vacuum. Yield 0.052 g (72%).
OMe) bond lengths (average 2.129(5) Å) in 6. This is
probably due to the larger steric hindrance experienced
by the µ3-OMe group compared to the µ3-OH group
(apart from the expected weaker interaction of the Re
atoms with a µ3-OR group, which is less basic than µ2-
OR groups). The bulkier methoxo groups do not cause
any significant expansion of the Re3 triangle, however,
as shown by the close similarity between the range of
Re‚‚‚Re distances in 6 (3.42-3.44 Å) and those observed
in [Re3(µ-OH)2(µ-OMe)(µ3-OMe)(CO)9]- (3.42-3.44 Å)
and [Re3(µ-OH)3(µ3-OH)(CO)9]- (3.41-3.44 Å).
Con clu d in g Rem a r k s. Controlled acidolysis of [Re2-
(µ-OR)3(CO)6]- complexes in the presence of dppf pro-
vides a convenient general route to the complexes
[Re2(µ-OR)2(µ-dppf)(CO)6] (R ) H, Me, Et, Ph). The
latter complexes exhibit fluxionality in solution at room
temperature, in the form of the twisting of the ferrocenyl
moiety of the dppf ligand with respect to the Re‚‚‚Re
axis. This twisting motion is correlated with the
restricted rotation of the ethyl groups about the O-CH2
bonds in the ethoxo complex [Re2(µ-OEt)2(µ-dppf)(CO)6],
which provides an interesting example of a situation in
which the two exchanging positions of the methylene
protons of an ethyl group are nonequivalent while the
exchanging positions of the methyl group are equivalent.
Controlled acidolysis of [Re2(µ-OMe)3(CO)6]- under 1
atm of CO pressure affords the complex [Re3(µ-OMe)3-
(µ3-OMe)(CO)9]- instead of [Re2(µ-OMe)2(CO)8]. This
may be attributed to the strong tendency of OMe groups
to function as bridging ligands,16 the relative lability of
CO ligands, and the low steric hindrance of CO and
OMe ligands against the aggregation of [Re(OMe)(CO)3]
fragments. Similar reasons may be invoked to explain
the fact that [Re(OMe)(CO)5] has so far eluded isolation.
Anal. Calcd for
C14H23NO9Re2: C, 23.3; H, 3.2; N, 1.9.
Found: C, 23.2; H, 3.2; N, 2.0. IR (cm-1): CH2Cl2 ν(C-O) 2007
(vw), 1996 (m), 1878 (vs); KBr ν(O-H) 3639 (m).
The recovery of the anion was increased to 90% when
[NBun4]Br was used as the precipitant, in which case the salt
was obtained as white microcrystals after 1 day at 10 °C.
[NEt4][Re2(µ-OR)3(CO)6] (R ) Me, Et). In a typical
synthesis, a 1 M solution of NaOR in ROH was prepared by
the reaction of sodium (0.23 g, 10 mmol) with 10 mL of the
alcohol. A 0.6 mL amount of the 1 M NaOR/ROH solution
was added to a solution of ReBr(CO)5 (0.082 g, 0.2 mmol) in
20 mL of THF and 10 mL of ROH. The resultant mixture was
stirred under vacuum at room temperature for 1 h and then
under argon for 20 h. The solvent was removed under reduced
pressure, and the solid residue obtained was redissolved in 5
mL of ROH. The solution was filtered and treated with a
solution of [NEt4]Cl (0.33 g, 2.0 mmol) in H2O (5 mL). The
resultant solution was kept at -10 °C for 1-2 days. The
precipitate of [NEt4][Re2(µ-OR)3(CO)6] obtained was isolated
by filtration and dried under vacuum.
[NEt4][Re2(µ-OMe)3(CO)6]. Colorless needle-shaped crys-
tals. Yield 0.065 g (85%). Anal. Calcd for C17H29NO9Re2: C,
26.7; H, 3.8; N, 1.8. Found: C, 26.1; H, 3.8; N, 1.9.19 IR (cm-1):
CH2Cl2 ν(C-O) 1993 (s), 1876 (vs). 1H NMR ((CD3)2CO): δ
4.20 (s, 9H, µ-OMe).
[NEt4][Re2(µ-OEt)3(CO)6]. White powder. Yield 0.055 g
(68%). Anal. Calcd for C20H35NO9Re2: C, 29.8; H, 4.4; N, 1.7.
Found: C, 29.8; H, 4.4; N, 1.7. IR (cm-1): CH2Cl2 ν(C-O) 1990
(s), 1872 (vs). 1H NMR (CDCl3): δ 4.24 (q, 6H, µ-OCH2CH3),
1.28 (t, 9H, µ-OCH2CH3).
[NEt4][Re2(µ-OH)(µ-OP h )2(CO)6] (5). A 1 M solution of
NaOPh in THF was prepared by the reaction of sodium (0.115
g, 5 mmol) with phenol (0.565 g, 6 mmol, dried under vacuum
at room temperature and weighed in a glovebox) in freshly-
distilled THF. A 0.6 mL amount of this solution and 0.1 mL
of wet THF ([H2O] ≈ 1 M, prepared by the addition of 0.18
mL (ca. 10 mmol) of water to 10 mL of dried THF) were added
to a solution of ReBr(CO)5 (0.082 g, 0.2 mmol) in 20 mL of
THF. The resultant mixture was stirred under vacuum at
room temperature for 1 h and then under argon for 20 h. The
solvent was removed under reduced pressure, and the solid
residue obtained was redissolved in 10 mL of H2O. The
solution was filtered and treated with a solution of [NEt4]Cl
(0.33 g, 2.0 mmol) in H2O (5 mL). The resultant solution was
kept at 10 °C for 1-2 days, during which a white powdery
precipitate of [NEt4][Re2(µ-OH)(µ-OPh)2(CO)6] (5) was formed.
The solid was separated by filtration, dried under vacuum, and
recrystallized by layering a solution of the compound in CH2-
Cl2 with hexane. Colorless prismatic crystals of [NEt4][Re2-
(µ-OH)(µ-OPh)2(CO)6] were obtained. Yield 0.065 g (74%).
Exp er im en ta l Section
All reactions were performed under pure dry argon using
standard Schlenk techniques. Solvents used were of reagent
grade and were dried by published procedures17 and freshly
distilled under argon before use. The complex [ReBr(CO)5] was
prepared according to reported procedures.18 All other re-
agents were of AR grade and were obtained from commercial
sources. Precoated silica plates of layer thickness 0.25 mm
were obtained from Merck. 1H and 31P{1H} NMR spectra were
recorded at ca. 300 K at field strengths of 300.0 and 121.5
MHz, respectively. 1H and 31P chemical shifts are quoted in
ppm downfield of tetramethylsilane and external 80% H3PO4,
respectively. Elemental analyses were performed by the
Microanalytical Laboratory, Department of Chemistry, Na-
tional University of Singapore.
[NEt4][Re2(µ-OH)3(CO)6]. Aqueous NaOH (0.2 M, 5 mL)
was added to a solution of ReBr(CO)5 (0.082 g, 0.2 mmol) in
20 mL of THF and 5 mL of H2O. The resultant mixture was
stirred under vacuum at room temperature for 1 h and then
under argon for 20 h. The solvent was removed under reduced
pressure, and the solid residue obtained was redissolved in 5
mL of H2O. The solution was filtered and treated with a
solution of [NEt4]Cl (0.33 g, 2.0 mmol) in H2O (5 mL). The
resultant solution was kept at 10 °C for 1 week. The colorless
Anal. Calcd for
C26H31NO9Re2: C, 35.7; H, 3.6; N, 1.6.
Found: C, 34.6; H, 3.6; N, 1.6.19 IR (cm-1): CH2Cl2 ν(C-O)
2003 (s), 1886 (vs); KBr ν(O-H) 3648 (m). 1H NMR: CD2Cl2
δ 7.26-7.16 (m, 8H, Ph), 6.76 (tt, 2H, Ph), 2.92 (q, 8H, NCH2-
CH3), 1.14 (tt, 12H, NCH2CH3).
[Re2(µ-OH)2(µ-d p p f)(CO)6] (1). A solution of TsOH‚H2O
(recrystallized from hot water) (0.038 g, 0.20 mmol) in 10 mL
of THF was transferred into a stirred solution of [NEt4][Re2-
(µ-OH)3(CO)6] (0.145 g, 0.20 mmol) and dppf (0.112 g, 0.20
mmol) in 20 mL of THF. The resultant mixture was stirred
under argon for 3 h. The solution was then concentrated to
10 mL and filtered. Water (20 mL) was added to the filtered
chrome-yellow solution, and the mixture was kept at 10 °C
for 24 h. The yellow precipitate formed was filtered and
(16) Cotton, F. A.; Wilkinson, G. Advanced Inorganic Chemistry, 5th
ed.; Wiley-Interscience: Singapore, 1988; p 472.
(17) Gordon, A. J .; Ford, R. A. The Chemist’s Companion:
A
Handbook of Practical Data, Techniques and References; Wiley-
Interscience: New York, 1972.
(18) (a) Albano, V. G.; Bellon, P. L.; Sansoni, M. J . Chem. Soc. A
1971, 2420. (b) Angelici, R. J .; Kruse, A. E. J . Organomet. Chem. 1970,
22, 461.
(19) The carbon analysis was consistently lower than the calculated
value, despite excellent agreement for the H and N analyses, possibly
due to the formation of a small amount of refractory rhenium carbide
during combustion analysis.

Controlled Acidolysis of [Re2(µ-OR)3(CO)6]-
Organometallics, Vol. 17, No. 2, 1998 179
Ta ble 2. Cr ysta llogr a p h ic Da ta for Com p ou n d s 1, 3, 5, a n d 6
1
3
5
6
chemical formula
space group
unit cell dimens
a (Å)
b (Å)
c (Å)
C
P1h
40H30FeO8P2Re2(C3H6O)2.5
C47H38FeO8P2Re2
C2/c
C26H31NO9Re2
P21/n
C21H32NO13Re3
P1h
12.037(3)
12.781(3)
16.877(4)
109.37(2)
99.17(2)
97.31(2)
2372.5(10)
2
20.664(3)
15.369(2)
17.129(2)
90
122.231(9)
90
13.479(3)
14.601(4)
14.888(3)
90
102.850(10)
90
10.195(5)
11.436(5)
13.493(5)
96.56(3)
99.54(3)
96.62(3)
R (deg)
â (deg)
γ (deg)
V (Å3)
4601.8(10)
4
2856.7(12)
4
1526.8(11)
2
Z
cryst size (mm)
0.25 × 0.24 × 0.44
0.13 × 0.20 × 0.40
0.08 × 0.15 × 0.30
0.07 × 0.20 × 0.40
µ (mm-1
)
5.59
5.679
8.518
11.921
min, max transmission
diffractometer
max 2θ (deg)
0.677, 0.999
Nonius
49.9
-14 to 14, 0 to 15,
-20 to 18
8777
0.5976, 0.8455
Siemens P4
47.0
-1 to 23, to 1 to 17,
to 19 to 16
4066
0.4894, 0.9487
Siemens P4
45.1
-1 to 14, to 1 to 15,
to 16 to 15
4667
0.3452, 0.9798
Siemens P4
50.0
-1 to 12, to 13 to 13,
to 16 to 15
6343
hkl range
no. of reflns measd
no. of unique reflns (Rint
)
8341 (0.012)
3412 (0.038)
0.0448, 0.1225
3707 (0.039)
0.0438, 0.1017
5357 (0.017)
0.0296, 0.0718
R1,b wRc (I >2 σ(I))
0.032, 0.035 (Rw)d
a
Details in common: temperature of 296 ( 2 K, graphite-monochromated Mo KR radiation, θ-2θ scan mode, empirical ψ absorption
corrections. R1 ) ∑||Fo| - |Fc||/∑|Fo|. c wR ) [∑w(Fo - Fc2)2/∑w(Fo2)2]1/2
.
Rw ) [∑w(|Fo| - |Fc|)2/∑w|Fo| ]1/2
.
b
2
d
2
recrystallized from acetone (slow evaporation at 10 °C). Yellow
prismatic crystals of Re2(µ-OH)2(µ-dppf)(CO)6 (1) were formed.
The crystals became opaque soon after leaving the mother
liquor. Yield 0.198 g (88%). Anal. Calcd for C40H30FeO8P2-
Re2: C,42.6; H, 2.7; P, 5.5. Found: C, 42.7; H, 2.7; P, 5.5. IR
(cm-1): CH2Cl2 ν(C-O) 2026 (s), 2009 (m), 1920 (m), 1898 (vs),
1888 (s, sh); KBr ν(O-H) 3600 (m). 1H NMR: CD2Cl2 δ 7.43
(br s, 20H, Ph), 5.5-4.5 (vbr s, 4H, Cp), 3.8-3.4 (vbr s, 4H,
Cp), -0.38 (t, 3J (HP) ) 1.3 Hz, 2H, µ-OH) [cf. δ(OH) -0.35,
3J (HP) ) 4.0 Hz for Re2(µ-OH)2(µ-dppm)(CO)6].3 31P{1H} NMR
(CD2Cl2): δ 3.0.
[Re2(µ-OMe)2(µ-d p p f)(CO)6] (2). A solution of TsOH‚H2O
(0.038 g, 0.20 mmol) in 10 mL of CHCl3 and 10 mL of MeOH
was transferred into a stirred solution of [NEt4][Re2(µ-OMe)3-
(CO)6] (0.152 g, 0.20 mmol) and dppf (0.112 g, 0.20 mmol) in
10 mL of CHCl3. The resultant mixture was stirred under
argon for 1 h. The solvent was then removed under reduced
pressure. The residue obtained was redissolved in a minimum
amount of CHCl3 and chromatographed on silica TLC plates
(CH2Cl2/hexane 2:3). Complex 2 was isolated from the main
band (Rf 0.50) and was recrystallized from a CH2Cl2-MeOH
mixture and identified by IR and 1H and 31P NMR
spectroscopy.1b Yield 0.164 g (71%).
°C. Yield 0.095 g (36%, yellow powder). Anal. Calcd for
C52H38FeP2O8Re2.0.5CH2Cl2: C, 47.6; H, 3.0; P, 4.7. Found:
C, 47.3; H, 3.1; P, 4.8. IR (cm-1): CH2Cl2 ν(C-O) 2024 (s),
2008 (m), 1916 (m, sh), 1899 (vs), 1887 (s, sh). 1H NMR: CD2-
Cl2 δ 7.8-7.1 (vbr m, 30H, Ph), 4.8-4.6 (br s, 4H, Cp), 3.8-
3.7 (vbr s, 4H, Cp); (CD3)2CO δ 7.8-7.1 (vbr m, 30H, Ph), 4.7-
4.5 (br s, 4H, Cp), 3.8-3.5 (vbr s, 4H, Cp). 31P{1H} NMR:
CD2Cl2 δ 3.6; (CD3)2CO δ 2.6.
Acid olysis of [Re2(µ-OMe)3(CO)6]- in th e p r esen ce of
P P h 3. The procedure was similar to that described for
complex 2, except that PPh3 (0.106 g, 0.40 mmol) was used
instead of dppf (0.112 g, 0.20 mmol) and that the reaction was
allowed to proceed for 24 h. Removal of solvent followed by
TLC (CH2Cl2/hexane 2:3) revealed the presence of numerous
products which were formed in minute quantities. The
complex [fac-Re(η1-OTs)(CO)3(PPh3)2] was isolated from the
main band (Rf 0.08) and recrystallized by layering a solution
of the complex in CH2Cl2 with hexane. Yield 0.020 g (12%,
colorless prismatic crystals). Anal. Calcd for C46H37O6P2-
ReS: C, 57.2; H, 3.8; S, 3.3; P, 6.4. Found: C, 57.8; H, 4.0; S,
2.8; P, 6.7. IR (cm-1): CH2Cl2 ν(C-O) 2041 (s), 1960 (m), 1908
(m). 1H NMR: CD2Cl2 δ 7.4-7.0 (m, 34H, Ph), 2.35 (s, 3H,
CH3). 31P{1H} NMR (CD2Cl2): δ 9.2.
[Re2(µ-OEt)2(µ-d p p f)(CO)6] (3). The procedure was simi-
lar to that described for complex 2 except that [NEt4][Re2(µ-
OEt)3(CO)6] (0.161 g, 0.20 mmol) and EtOH were used instead
of [NEt4][Re2(µ-OMe)3(CO)6] and MeOH. Removal of solvent
followed by TLC (CH2Cl2/hexane 2:3) yielded complex 3 (Rf
0.47), which was then recrystallized from CH2Cl2-EtOH
solution at -10 °C. Yield 0.028 g (12%, chrome-yellow
Acid olysis of [Re2(µ-OMe)3(CO)6]- in th e p r esen ce of
CO. Carbon monoxide was bubbled through a stirred solution
of [NEt4][Re2(µ-OMe)3(CO)6] (0.152 g, 0.20 mmol) in 20 mL of
CHCl3. About 10 min later, a solution of TsOH‚H2O (0.038 g,
0.20 mmol) in 10 mL of CHCl3 and 10 mL of MeOH was
transferred into the above CO-saturated solution. The mixture
was stirred at room temperature for 24 h, with CO being
bubbled through at a slow rate. The solvent was removed
under reduced pressure, and the residue obtained was redis-
solved in a minimum amount of CHCl3 and chromatographed
on silica TLC plates (CHCl3). The main band (Rf 0.08) was
extracted with CH2Cl2, and the concentrated extract was
layered with hexane. Colorless prismatic crystals of [NEt4]-
[Re3(µ3-OMe)(µ-OMe)3(CO)9] were obtained (0.018 g, 13%).
Anal. Calcd for C21H32NO13Re3: C, 23.7; H, 3.0; N, 1.3.
Found: C, 23.9; H, 3.1; N, 1.5. IR (cm-1): CH2Cl2 ν(C-O) 2023
(w), 2004 (s), 1893 (vs), 1879 (s, sh); THF 2021 (w), 2003 (s),
1892 (vs), 1878 (s, sh). 1H NMR: (CD3)2CO δ 4.52 (s, 3H, µ3-
OMe), 4.24 (s, 9H, µ-OMe); CD2Cl2 δ 4.51 (s, 3H, µ3-OMe), 4.30
(s, 9H, µ-OMe).
microcrystals). Anal. Calcd for C44H38FeO8P2Re2(CH2Cl2)0.5
:
C, 43.5; H, 3.2; P, 5.0. Found: C, 43.8; H, 3.2; P, 5.2. IR
(cm-1): CH2Cl2 ν(C-O) 2025 (vs), 2008 (s), 1920 (s), 1898 (vs),
1890 (s, sh). 1H NMR: CD2Cl2 δ 7.46 (br s, 20H, Ph), 4.65 (br
s, 4H, CH2), 1.45 (t, 3J (HH) ) 6.2 Hz, 6H, CH3). 31P{1H} NMR
(CD2Cl2): δ 3.6.
[Re2(µ-OP h )2(µ-d p p f)(CO)6] (4). A solution of TsOH‚H2O
(0.038 g, 0.20 mmol) in 20 mL of CHCl3 was transferred into
a stirred suspension of [NEt4][Re2(µ-OH)(µ-OPh)2(CO)6] (0.175
g, 0.20 mmol) and dppf (0.112 g, 0.20 mmol) in 20 mL of CHCl3.
The resultant mixture was stirred under argon for 1 h. The
solvent was then removed under reduced pressure. The
residue obtained was redissolved in a minimum amount of
CHCl3 and chromatographed on silica TLC plates (CH2Cl2/
hexane 2:3). Complex 4 was isolated from the main band (Rf
0.56) and recrystallized from CH2Cl2-hexane solution at -10
X-r a y Cr ysta llogr a p h y. The crystallographic data for
compounds 1, 3, 5, and 6 are summarized in Table 2, and
selected bond lengths and angles are given in Tables 3-6.

180 Organometallics, Vol. 17, No. 2, 1998
J iang et al.
Ta ble 3. Bon d Len gth s (Å) a n d An gles (d eg) for 1
Ta ble 6. Bon d Len gth s (Å) a n d An gles (d eg) for 6
Re(1)-P(1)
Re(1)-C(1)
Re(1)-C(2)
Re(1)-C(3)
Re(1)-O(7)
Re(1)-O(8)
2.5147(23)
1.899(9)
1.921(9)
1.903(9)
2.171(5)
2.170(5)
Re(2)-P(2)
Re(2)-C(4)
Re(2)-C(5)
Re(2)-C(6)
Re(2)-O(7)
Re(2)-O(8)
2.5307(21)
1.895(9)
1.933(9)
1.890(9)
2.153(5)
2.178(5)
Re(1)-C(11)
Re(1)-C(12)
Re(1)-C(13)
Re(1)-O(1)
Re(1)-O(3)
Re(1)-O(4)
Re(2)-C(21)
Re(2)-C(22)
Re(2)-C(23)
Re(2)-O(2)
Re(2)-O(3)
1.915(8)
1.891(8)
1.910(8)
2.134(5)
2.135(5)
2.213(4)
1.915(9)
1.914(9)
1.893(8)
2.132(5)
2.122(5)
Re(2)-O(4)
Re(3)-C(31)
Re(3)-C(32)
Re(3)-C(33)
Re(3)-O(1)
Re(3)-O(2)
Re(3)-O(4)
O(1)-C(1)
O(2)-C(2)
O(3)-C(3)
O(4)-C(4)
2.183(5)
1.896(9)
1.902(8)
1.906(8)
2.124(4)
2.129(5)
2.210(5)
1.412(8)
1.425(8)
1.406(9)
1.466(8)
C(1)-Re(1)-P(1)
83.4(3)
C(6)-Re(2)-P(2)
C(4)-Re(2)-O(8)
C(5)-Re(2)-O(8)
C(6)-Re(2)-O(8)
C(4)-Re(2)-C(5)
C(4)-Re(2)-C(6)
C(5)-Re(2)-C(6)
O(7)-Re(2)-O(8)
88.3(3)
170.7(3)
94.6(3)
101.1(3)
85.6(4)
88.1(4)
83.4(4)
70.81(18)
C(2)-Re(1)-P(1) 167.4(3)
C(3)-Re(1)-P(1)
88.3(3)
C(1)-Re(1)-O(7) 172.3(3)
C(2)-Re(1)-O(7)
C(3)-Re(1)-O(7)
C(1)-Re(1)-C(2)
C(1)-Re(1)-C(3)
C(2)-Re(1)-C(3)
O(7)-Re(1)-O(8)
C(4)-Re(2)-P(2)
94.6(3)
97.2(3)
86.1(4)
90.5(4)
84.7(4)
Re(1)-O(1)-Re(3)
Re(2)-O(2)-Re(3)
Re(1)-O(3)-Re(2)
Re(1)-O(4)-Re(2)
Re(1)-O(4)-Re(3)
Re(2)-O(4)-Re(3)
O(1)-Re(1)-O(3)
O(1)-Re(1)-O(4)
O(3)-Re(1)-O(4)
O(2)-Re(2)-O(3)
O(2)-Re(2)-O(4)
O(3)-Re(2)-O(4)
106.9(2)
106.6(2)
107.8(2)
103.0(2)
101.3(2)
102.1(2)
82.2(2)
74.8(2)
73.5(2)
81.4(2)
74.9(2)
74.3(2)
O(1)-Re(3)-O(2)
O(1)-Re(3)-O(4)
O(2)-Re(3)-O(4)
C(1)-O(1)-Re(1)
C(1)-O(1)-Re(3)
C(2)-O(2)-Re(2)
C(2)-O(2)-Re(3)
C(3)-O(3)-Re(1)
C(3)-O(3)-Re(2)
C(4)-O(4)-Re(1)
C(4)-O(4)-Re(2)
C(4)-O(4)-Re(3)
81.2(2)
75.1(2)
74.3(2)
Re(1)-O(7)-Re(2) 104.45(20)
119.9(4)
121.4(4)
120.8(5)
119.3(5)
121.1(5)
122.1(5)
115.5(4)
116.5(4)
116.2(4)
70.61(18) Re(1)-O(8)-Re(2) 103.64(20)
85.53(25) C(51)-P(1)-Re(1) 120.6(3)
C(5)-Re(2)-P(2) 168.1(3)
C(56)-P(2)-Re(2) 123.0(3)
Ta ble 4. Bon d Len gth s (Å) a n d An gles (d eg) for 3a
Re(1)-P(1)
Re(1)-C(1)
Re(1)-C(2)
Re(1)-C(3)
Re(1)-O(10)
2.543(3)
1.930(14)
1.910(14)
1.88(2)
Re(1)-O(10a)
O(10)-C(10)
C(10)-C(20)
C(10)-C(20′)
2.189(8)
1.421(9)
1.503(10)
1.514(10)
(except those of the acetone solvate molecules) being allowed
anisotropic motion. All hydrogen atoms were held fixed in the
final cycles of least-squares refinement. During the structure
refinement, 2.5 acetone solvate molecules were found, the third
one being disorderedsthree independent non-H sites connected
with three inversion-related sites, making a total of six for four
non-H atoms of acetone. A combined scattering curve Oa was
2.190(7)
C(1)-Re(1)-P(1)
C(2)-Re(1)-P(1)
C(3)-Re(1)-P(1)
C(1)-Re(1)-O(10)
168.0(4) C(2)-Re(1)-C(3)
87.4(4) O(10a)-Re(1)-O(10)
85.9(4) C(10)-O(10)-Re(1a) 123.0(7)
92.3(4) C(10)-O(10)-Re(1) 113.7(8)
86.6(6)
72.8(3)
C(2)-Re(1)-O(10) 172.3(4) Re(1a)-O(10)-Re(1) 103.2(3)
C(3)-Re(1)-O(10)
C(1)-Re(1)-C(2)
C(1)-Re(1)-C(3)
99.8(5) O(10)-C(10)-C(20)
84.0(5) O(10)-C(10)-C(20′) 113.2(10)
85.3(6) C(31)-P(1)-Re(1) 123.7(4)
113.9(10)
constructed as (1/6O + /6C), and a combined scattering curve
5
Ob was constructed as (1/3O + 2/3C). The contributions of the
third acetone solvate molecule to the structure factors were
the summation of two Oa positions, each with half occupancy,
and one Ob, with full occupancy. The last least-squares cycle
was calculated with 523 parameters and 5850 reflections. The
weighting function used was w-1 ) σ2(Fo) + 0.000100Fo2, and
the secondary extinction coefficient23 was 0.12(5). The maxi-
mum shift/σ ratio was 0.026. In the last difference map, the
deepest hole was -0.700 e/Å3 and the highest peak was 0.960
e/Å3.
a
Symmetry transformations used to generate equivalent at-
oms: -x + 2, y, -z + 3/2.
Ta ble 5. Bon d Len gth s (Å) a n d An gles (d eg) for 5
Re(1)···Re(2)
Re(1)-O(10)
Re(1)-O(20)
Re(1)-O(30)
Re(1)-C(1)
Re(1)-C(2)
Re(1)-C(3)
3.1519(9)
2.162(8)
2.149(8)
2.138(9)
1.89(2)
Re(2)-O(10)
Re(2)-O(20)
Re(2)-O(30)
Re(2)-C(4)
Re(2)-C(5)
Re(2)-C(6)
2.163(9)
2.151(8)
2.118(9)
1.88(2)
1.88(2)
1.91(2)
[Re2(µ-OEt)2(µ-d p p f)(CO)6] (3). Single chrome-yellow
crystals of 3 were grown by the slow evaporation of a solution
of the complex in a CH2Cl2-hexane mixture at 10 °C. The
number of data used for structure solution and refinement was
2563 (I > 2.0σ(I)). The structure was solved by the heavy-
atom method. All non-hydrogen atoms (except those of the
disordered solvate molecule and the disordered methyl carbon
atoms) were refined anisotropically by the full-matrix least-
squares method (on F2). Hydrogen atoms were introduced in
calculated positions and refined isotropically (riding model)
in the final cycles of least-squares refinement. The disordered
ethyl group was refined with two positions for the methyl
carbon (C(20) and C(20′)), having occupancies of 60% and 40%,
respectively, and the distance constraints O(10)-C(10) ) 1.43
( 0.01, C(10)-C(20)/C(20′) ) 1.54 ( 0.01, and O(10)···C(20)/
C(20′) ) 2.43 ( 0.01. The relatively large thermal parameter
(U(eq) 0.108(7) Å2) and elongated shape of the thermal ellipsoid
of the methylene carbon C(10) suggest that the methylene
group is also disordered. An attempt to refine the structure
based on a disordered methylene carbon (by splitting the atom
along the direction of maximum displacement) did not improve
the R values. The severely-disordered solvate molecule is
1.89(2)
1.88(2)
Re(1)-O(10)-Re(2)
Re(1)-O(20)-Re(2)
Re(1)-O(30)-Re(2)
C(1)-Re(1)-C(2)
C(1)-Re(1)-C(3)
C(2)-Re(1)-C(3)
C(4)-Re(2)-C(5)
C(4)-Re(2)-C(6)
C(5)-Re(2)-C(6)
93.6(3) O(10)-Re(1)-O(30)
94.3(3) O(20)-Re(1)-O(30)
95.5(4) O(10)-Re(2)-O(20)
86.0(6) O(10)-Re(2)-O(30)
88.7(6) O(20)-Re(2)-O(30)
88.0(7) C(11)-O(10)-Re(1) 136.0(8)
86.0(7) C(11)-O(10)-Re(2) 130.1(8)
85.1(7) C(21)-O(20)-Re(1) 133.1(7)
88.0(6) C(21)-O(20)-Re(2) 132.6(7)
72.8(3)
71.5(4)
71.4(3)
73.1(4)
71.9(3)
O(10)-Re(1)-O(20) 71.5(3)
Computations for 1 were carried out on a Microvax 3600
computer with the NRCVAX system,20 while computations for
3, 5, and 6 were carried out on a Pentium PC using the
SHELXTL PLUS software package.21
[Re2(µ-OH)2(µ-d p p f)(CO)6] (1). Single orange crystals of
1 were grown by the slow evaporation of a solution of the
complex in acetone at 10 °C. As crystals of 1 desolvate readily
on leaving the mother liquor, the crystal used for data
collection was sealed in a lithium glass capillary. The number
of data used for structure solution and refinement was 5850
(I > 2.0σ(I)). The structure was solved by direct methods
(MULTAN22). Refinement (on F) was carried out by the full-
matrix least-squares method with all non-hydrogen atoms
located about
a crystallographic inversion center and is
(22) Main, P.; Fiske, S. E.; Hull, S. L.; Germain, G.; Declerq, J . P.;
Woolfson, M. M. MULTAN, a System of Computer Programs for Crystal
Structure Determination from X-ray Diffraction Data; Universities of
York (UK) and Louvain (Belgium), 1980.
(23) The refined parameter is the average path length in a mosaic
block in µm, see: Larson, A. C. In Crystallographic Computing; Ahmed,
F. R., Ed.; Munksgaard: Copenhagen, 1970; p 293.
(20) Gabe, E. J .; Le Page, Y.; Charland, J .-P.; Lee, F. L.; White, P.
S. J . Appl. Crystallogr. 1989, 22, 384.
(21) Sheldrick, G. M. SHELXTL PC, Version 5.03; Siemens Analyti-
cal X-ray Instruments, Inc.: Madison, WI, 1994.

Controlled Acidolysis of [Re2(µ-OR)3(CO)6]-
Organometallics, Vol. 17, No. 2, 1998 181
probably CH2Cl2 or n-hexane. Yet, as reasonable models of
either CH2Cl2 or n-hexane could not be constructed, C100,
C200, and C300 (all half occupancy) per asymmetric unit were
refined to account for the scattering in the solvate region. The
last least-squares cycle was calculated with 269 parameters
and all of the 3412 unique reflections. The weighting function
used was w-1 ) σ2(Fo2) + (0.0700P)2 + 27.0000P, where P )
solution and refinement was 4598 (I > 2.0σ(I)). The structure
was solved by the heavy-atom method. All non-hydrogen
atoms were refined anisotropically by the full-matrix least-
squares method (on F2). Hydrogen atoms were introduced in
calculated positions and refined isotropically (riding model)
in the final cycles of least-squares refinement. The last least-
squares cycle was calculated with 343 parameters and all of
the 5357 unique reflections. The weighting function used was
2
(Fo + 2Fc2)/3. The maximum shift/σ ratio was 0.004. In the
last difference map, the deepest hole was -1.009 e/Å3 and the
highest peak was 1.798 e/Å3 (within 1 Å from the Re atom).
[NEt4][Re2(µ-OH)(µ-OP h )2(CO)6] (5). Single colorless
crystals of 5 were grown by layering a solution of the compound
in CH2Cl2 with hexane. The number of data used for structure
solution and refinement was 2742 (I > 2.0σ(I)). The structure
was solved by direct methods. All non-hydrogen atoms were
refined anisotropically by the full-matrix least-squares method
(on F2). Hydrogen atoms were introduced in calculated posi-
tions and refined isotropically in the final cycles of least-
squares refinement. All the hydrogen atoms were refined
using the riding model, except for the hydroxo hydrogen, which
was allowed to vary freely with only the bond length constraint
O-H ) 0.85 ( 0.02 Å. The last least-squares cycle was
calculated with 347 parameters and all of the 3707 unique
reflections. The weighting function used was w-1 ) σ2(Fo2) +
w-1 ) σ2(Fo2) + (0.0400P)2, where P ) (Fo + 2Fc2)/3. The
2
maximum shift/σ ratio was 0.002. In the last difference map,
the deepest hole was -1.405 e/Å3 and the highest peak was
0.880 e/Å3.
Ack n ow led gm en t. We thank the National Univer-
sity of Singapore (NUS) (Grant No. RP 950695), the
National Institute of Education, Nanyang Technological
University (Grant No. RP 15/95 YYK), and the Aca-
demia Sinica, Taipei, for financial support. Technical
assistance from the staff of the NMR Laboratory,
Department of Chemistry, NUS is acknowledged. C.H.J .
is grateful to NUS for a scholarship award.
Su p p or tin g In for m a tion Ava ila ble: Text giving the
details of X-ray structural analyses and tables of crystal-
lographic data, refined atomic coordinates and isotropic ther-
mal parameters, anisotropic thermal parameters, and bond
lengths and angles (26 pages). Ordering information is given
on any current masthead page.
(0.0600P)2, where P ) (Fo + 2Fc2)/3. The maximum shift/σ
2
ratio was 0.149. In the last difference map the deepest hole
was -1.583 e/Å3 and the highest peak was 1.221 e/Å3 (within
1 Å from Re(1)).
[NEt4][Re3(µ3-OMe)(µ-OMe)3(CO)9] (6). Single colorless
crystals of 6 were grown by layering a solution of the compound
in CH2Cl2 with hexane. The number of data used for structure
OM970614L