Synthesis, characterization and X-ray structure of several aryloxide and alkoxide derivatives of [Et4N][Re2(CO)6(OR) 3] (R = H or Me)

Article abstract of DOI:10.1016/j.ica.2004.11.017

The ligand exchange reaction of the anionic binuclear rhenium complexes Re₂(CO)₆(OR)₃^- (R = H (1) or Me (2)) has been studied with the arylalcohols 4-aminophenol (3, 4), 3-dimethylaminophenol (5), 3-cyanophenol

Full text of DOI:10.1016/j.ica.2004.11.017

Inorganica Chimica Acta 358 (2005) 1050–1060
www.elsevier.com/locate/ica
Synthesis, characterization and X-ray structure of several aryloxide
and alkoxide derivatives of [Et4N][Re2(CO)6(OR)3] (R = H or Me)
*
Kevin K. Klausmeyer , Franklin R. Beckles
Department of Chemistry and Biochemistry, Baylor University, Waco, TX 76798-7348, USA
Received 12 August 2004; accepted 10 November 2004
Abstract
ꢀ
The ligand exchange reaction of the anionic binuclear rhenium complexes Re2ðCOÞ ðORÞ (R = H (1) or Me (2)) has been stud-
6
3
ied with the arylalcohols 4-aminophenol (3, 4), 3-dimethylaminophenol (5), 3-cyanophenol (6) and 4-cyanophenol (7, 8) and the diol
ethylene glycol (9). Complete exchange of the three hydroxy or methoxy ligands by aryl alcohols can be attained by heating the
reaction mixture or allowing the mixture to stir for several days. Incomplete exchange is achieved by stoichiometric control of
the incoming ligand and is complete within twelve hours. For the alkyl alcohol ethylene glycol complete exchange can be obtained
in 8 h. Crystal structure determinations for several of these derivatives have been carried out.
ꢀ 2004 Elsevier B.V. All rights reserved.
Keywords: Rhenium carbonyl; Alkoxide complexes; Ligand exchange; X-ray crystallography
1. Introduction
shown to assist in the formation of a honeycomb supra-
molecular architecture encapsulating linear H-bonded
[DABCO-H] cations [13].
Monovalent rhenium tricarbonyl complexes have
been the focus of considerable attention recently. Inter-
est in these complexes is derived from several different
areas. For example, mononuclear complexes contain-
ing a variety of ligands have been implicated for use
as radiotherapeutic cancer agents [1] as well as radio-
pharmaceutical model complexes for 99mTc chemistry
[2–5].
Another area of interest comprises binuclear units
bridged by alkoxide or carboxylate ligands which have
been linked together for the formation of molecular rect-
angles [6–9]. This chemistry has been extended to the
study of luminescent rhenium carbonyls by use of pyri-
dine and 4,40-bipyridine as linking functionalities for the
formation of squares and rectangles. Mononuclear com-
plexes have also been observed to possess luminescence
[10–12]. More recently, [Re2(CO)6(OMe)3]ꢀ has been
Of particular interest to us are the triply bridged alk-
oxy complexes and their reaction chemistry. The ex-
change reaction chemistry fragmentation pathways of
the binuclear rhenium complexes [Re2(CO)6(OH)3]ꢀ
and [Re2(CO)6(OMe)3]ꢀ have previously been studied
by electrospray ionization mass spectrometry [14–16].
The compound [Et4N][Re2(CO)6(OPh)3] had been previ-
ously synthesized by reaction of phenol with [Re3
(l-H)4(CO)10]ꢀ [17]. In this paper, we report on the syn-
thesis and characterization of several new derivatives
obtained by either partial or complete ligand substitu-
tion of the anions [Re2(CO)6(OH)3]ꢀ and [Re2
(CO)6(OMe)3]ꢀ with substituted aromatic alcohols and
with ethylene glycol as shown below
ꢀ
ꢀ
Re2ðCOÞ ðORÞ þ 3HOR0 ! Re2ðCOÞ ðORÞ ðOR0Þ
6
3
6
x
3ꢀx
þ 3 ꢀ xHOR
where R = H or Me, R0 = Ar or CH2CH2OH, and x = 0
or 1.
*
Corresponding author. Tel.: +1 2547102665; fax: +1 2547104272.
E-mail address: kevin_klausmeyer@baylor.edu (K.K. Klausmeyer).
0020-1693/$ - see front matter ꢀ 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2004.11.017

K.K. Klausmeyer, F.R. Beckles / Inorganica Chimica Acta 358 (2005) 1050–1060
1051
These complexes show interesting exchange properties
which depend on the nature of the incoming ligand and
give insight to the formation of supramolecular
assemblies.
by the addition of 40 mL of hexane. The pale pink solid
obtained was dried under vacuum overnight. Complex 4
is light sensitive, but the complex remained stable after
the exposure to light.
2.2.3. Synthesis of [Et4N][Re2(CO)6(OCH2CH2OH)3] (9)
In a 100 mL Schlenk flask, 0.100 g (0.138 mmol) of
complex 1 was dissolved in 20 mL of THF and a
HOCH2CH2OH solution (3 equiv.) was added. The
solution was stirred for 8 h at room temperature, and
considered complete when there was no longer a change
the carbonyl region of the IR spectrum. The solvent was
then removed in vacuo. The white solid was recrystal-
lized by dissolving the solid in 4 mL of THF and precip-
itated by the addition of 40 mL of hexane. The white
solid obtained was dried under vacuum overnight. Com-
plex 9 is extremely hygroscopic.
2. Experimental
2.1. General considerations
All reactions were carried out under air free condi-
tions in an Argon filled glove box, or using standard
Schlenk techniques. THF, diethyl ether, and hexane were
freshly distilled from sodium/benzophenone ketyl, aceto-
nitrile was freshly distilled from calcium hydride. Infra-
red spectra were recorded on a ThermoMattson IR300
1
spectrometer. H and 13C NMR spectra were recorded
on a Bruker 300 MHz NMR spectrometer and refer-
enced to the residual solvent peaks. Mass spectra were
acquired using an API QStar Pulsar (MDS Sciex, Con-
cord, Ont.) quadrupole-time-of-flight mass spectrometer
(QqTOFMS) equipped with an ionspray source.
2.2.4. [Et4N][Re2(CO)6(OH)(4-OC6H4NH2)2] (3)
Pale pink powder; yield: 0.081 g (68%). IR (cmꢀ1):
CH3CN m(C–O) 2004 (m), 1887 (vs). 1H NMR (acetoni-
trile-d3): d 6.90 and 6.52 ppm (m, m, 4H, 4H,
OC6H4NH2), 3.69 ppm (s, 4H, NH2), 3.09 ppm (q,
8H, (CH3CH2)4N), 2.38 ppm (s, 1H, OH), 1.13 ppm
(tt, 12H, (CH3CH2)4N). 13C NMR (acetonitrile-d3):
200.7 ppm (CO), 158.7 ppm (OCC5H4NH2) 141.2 ppm
(OC5H4CNH2), 120.1, and 116.3 ppm (OC5H4NH2),
52.8 ppm (CH3CH2)4N and 7.4 ppm (CH3CH2)4N.
Anal. Calc. for C26H33N3O9Re2: C, 34.54; H, 3.68; N,
4.65. Found: C, 33.70; H, 3.61; N, 4.23%.!
2.2. Syntheses
The compounds [Et4N][Re2(CO)6(OH)3] (1) and
[Et4N][Re2(CO)6(OCH3)3] (2) were synthesized follow-
ing published procedures [18]. Re2(CO)10 was purchased
from Pressure Chemical. All other reagents were pur-
chased from Aldrich Chemical or Alfa Chemical and
used as received.
2.2.5. [Et4N][Re2(CO)6(4-OC6H4NH2)3] (4)
White powder; yield: 0.064 g (62%). IR (cmꢀ1):
CH3CN m(C–O) 2005 (m), 1888 (vs). 1H NMR (acetoni-
trile-d3): d 6.94 and 6.54 ppm (m, m, 6H, 6H,
OC6H4NH2), 3.76 ppm (s, 6H, NH2), 3.04 ppm (q,
8H, (CH3CH2)4N), 1.13 ppm (tt, 12H, (CH3CH2)4N).
13C NMR (acetonitrile-d3): 201.3 ppm (CO), 159.4
ppm (OCC5H4NH2), 141.9 ppm (OC5H4CNH2), 120.5,
and 117.0 ppm (OC5H4NH2), 52.8 ppm (CH3CH2)4N
and 7.4 ppm (CH3CH2)4N.
2.2.1. General synthesis of
[Et4N][Re2(CO)6(OR)(OR0)2] (R = H or Me;
R0 = 4-C6H4NH2 (3), 3-OC6H4NMe2 (5), 3-OC6H4CN
(6), and 4-C6H4CN (7 and 8))
Complex 1 or 2 was dissolved in 20 mL of acetonitrile
and a ROH solution (3 equiv.) was added, in order to
convert from the OHꢀ to the OMeꢀ complex a few
drops of MeOH was added. The mixture was stirred at
room temperature for 12 h and then the solvent was re-
moved in vacuo. The solid was dissolved in a minimum
amount of solvent (2–3 mL) and precipitated by the
addition of 60 mL of diethyl ether. The solid obtained
was dried under vacuum overnight.
2.2.6. [Et4N][Re2(CO)6(OH)(3-OC6H4N(CH3)2)2] (5)
Pale pink crystals; yield: 0.068 g (68%). IR (cmꢀ1):
CH3CN m(C–O) 2003 (m), 1886 (vs). 1H NMR (ace-
tone-d6): d 6.94, 6.79, 6.65 and 6.17 ppm (t, s, d, d,
2H, 2H, 2H, 2H, OC6H4N(CH3)2), 3.36 ppm (q, 8H,
(CH3CH2)4N), 2.91 ppm (s, 12H, N(CH3)2), 1.32 pm
(tt, 12H, (CH3CH2)4N). 13C NMR (acetone-d6): 200.01
ppm (CO), 165.5 ppm (OCC5H4N(CH3)2), 151.9 ppm
(OC5H4CN(CH3)2), 128.9, 108.2, 104.9 and 103.7 ppm
(OCC4H4N(CH3)2), 39.9 ppm (OC6H4N(CH3)2), 52.1
ppm (CH3CH2)4N and 6.7 ppm (CH3CH2)4N. Anal.
Calc. for C30H41N3O9Re2: C, 37.53; H, 4.31; N, 4.38.
Found: C, 37.24; H, 4.48; N, 4.03%.
2.2.2. Synthesis of [Et4N][Re2(CO)6(4- OC6H4NH2)3]
(4)
In a 100 mL Schlenk flask, 0.100 g (0.138 mmol) of
complex 1 was dissolved in 15 mL of THF and a 4-
HOC6H4NH2 solution (3 equiv.) was added. The solu-
tion was stirred at room temperature until no change
in the carbonyl region of the IR spectrum was observed.
Then the mixture was stirred at 60 ꢁC for 8 h, the solvent
was then removed in vacuo. The solid was recrystallized
by dissolving the solid in 4 mL of THF and precipitated

1052
K.K. Klausmeyer, F.R. Beckles / Inorganica Chimica Acta 358 (2005) 1050–1060
2.2.7. [Et4N][Re2(CO)6(OH)(3-OC6H4CN)2] (6)
White powder; yield: 0.083 g (65%). IR (cmꢀ1): THF
m(C–N) 2229 (w), m(C–O) 2009 (s), 1898 (vs). H NMR
of ether into an acetonitrile solution at 5 ꢁC, while crys-
tals of 7 were grown by vapor diffusion of hexane into a
1,2-dichloroethane solution of 7 at 5 ꢁC. A violet block
for 4, colorless block crystals for 5–9 were fixed to a
cryo-loop in paratone oil and immediately placed in a
nitrogen cold stream (110 K). Data for 4 were collected
on an Enraf-Nonius CAD4 diffractometer. For com-
plexes 5, 6, 7 and 9 a Bruker-Nonius X8 APEX diffrac-
tometer was used, while for complex 8 a Bruker
SMART 1000 X-ray diffractometer was used.
Data reduction was accomplished using XCAD for 4,
and SAINTPLUS (Bruker) for 5–9. All structures were
solved by direct methods using the SHELX program suite,
which provided the positions of the rhenium atoms and
some of the atoms of the ligands. Subsequent least
square refinements revealed the positions of the remain-
ing atoms in the structure. Unless noted otherwise, all
nonhydrogen atoms were refined anisotropically.
1
(acetone-d6): d 7.47 and 7.17 ppm (m, m, 4H, 4H,
OC6H4CN), 3.46 ppm (q, 8H, (CH3CH2)4N), 2.87
ppm (s, 1H, OH), 1.38 ppm (tt, 12H, (CH3CH2)4N).
13C NMR (acetone-d6): 199.72 ppm (CO), 166.03 ppm
(OCC5H4CN), 131.4, 125.5, 123.4, 123.2 and 113.5
ppm (OCC5H4CN), 119.7 ppm (CN), 53.1 ppm
(CH3CH2)4N and 7.7 ppm (CH3CH2)4N. Anal. Calc.
for C29H31N3O9Re2: C, 37.13; H, 3.34; N, 4.48. Found:
C, 37.19; H, 3.34; N, 4.47%.
2.2.8. [Et4N][Re2(CO)6(OH)(4-OC6H4CN)2] (7)
White powder; yield: 0.114 g (89%). IR (cmꢀ1): THF
1
m(C–N) 2229 (w), m(C–O) 2009 (s), 1898 (vs). H NMR
(acetone-d6): d 7.55 and 7.24 ppm (d, d, 4H, 4H,
OC6H4CN), 3.38 ppm (q, 8H, (CH3CH2)4N), 2.81
ppm (s, 1H, OH), 1.28 ppm (tt, 12H, (CH3CH2)4N).
13C NMR (acetone-d6): 199.4 ppm (CO), 169.3 ppm
(OCC5H4CN), 134.8, 121.5, and 102.6 ppm
(OCC5H4CN), 120.4 ppm (CN), 53.1 ppm (CH3CH2)4N
and 7.8 ppm (CH3CH2)4N. Anal. Calc for
C28H29NO9Re2: C, 36.40; H, 3.17; N, 4.55. Found: C,
36.69; H, 3.27; N, 4.57%.
3. Results and discussion
3.1. General characterizations
3.1.1. Synthesis and IR spectra
ꢀ
The reaction of the anions Re2ðCOÞ ðOHÞ (1), and
6
3
ꢀ
3
2.2.9. [Et4N][Re2(CO)6(OCH3)(4- OC6H4CN)2] (8)
White powder; yield: 0.102 g (78%). IR (cmꢀ1): THF
Re2ðCOÞ ðOMeÞ (2), with three equivalents of substi-
6
tuted aryl alcohols in acetonitrile results in the substitu-
tion of two of the bridging hydroxy or methoxy groups
by the aryl alcohol. For the aryl alcohols studied, 4-ami-
nophenol (3) and 4-cyanophenol (5, 6) complete ligand
substitution occurs if the reaction mixture is heated at
60ꢁC overnight or if the reaction is allowed to stir at
room temperature for one week. The trisubstituted com-
1
m(C–N) 2222 (w), m(C–O) 2012 (s), 1900 (vs). H NMR
(acetone-d6): d 7.66 and 7.33 ppm (d, d, 4H, 4H,
OC6H4CN),4.30 ppm (s, 4H, (OCH3)), 3.48 ppm (q,
8H, (CH3CH2)4N), 1.39 ppm (tt, 12H, (CH3CH2)4N).
13C NMR (acetone-d6): 198.1 ppm (CO), 168.3 ppm
(OCC5H4CN), 133.8, 120.5, and 101.6 ppm
(OCC5H4CN), 119.2 (CN), 65.3 ppm (OCH3), 52.1
ppm (CH3CH2)4N and 6.5 ppm (CH3CH2)4N. Anal.
Calc for C29H31NO9Re2: C, 37.13; H, 3.34; N, 4.48.
Found: C, 37.06; H, 3.27; N, 4.46%.
ꢀ
plex Re2ðCOÞ ð4-OC6H4NH2Þ (4), reported here has
6
3
been synthesized by the heating method. The bis-substi-
tuted products can also be formed by the stoichiometric
addition of the alcohol to the Re precursor, the reaction
is complete within 12 h. Complex 9 is formed by com-
plete exchange within 8 h. The infrared spectra of com-
plexes 3–9 is presented in Table 1, these compounds
contain two bands in the m(CO) region of 2030–1860
2.2.10. [Et4N][Re2(CO)6(OCH2CH2OH)3] (9)
White powder; yield: 0.088 g (75%). IR (cmꢀ1): THF
1
m(C–O) 1996 (s), 1879 (vs). H NMR (acetone-d6):4.24
ppm (t, 6H, (OCH2CH2OH)), 3.69 ppm (t, 6H, (OCH2-
CH2OH)), 3.50 ppm (q, 8H, (CH3CH2)4N), 1.40 ppm
(tt, 12H, (CH3CH2)4N). 13C NMR (acetone-d6): 201.06
ppm (CO), 79.19 ppm (OCH2CH2OH), 65.30 ppm
(OCH2CH2OH), 52.81 ppm (CH3CH2)4N and 7.46 ppm
(CH3CH2)4N. Anal. Calc for C20H35NO12Re2: C, 28.13;
H, 4.14; N, 1.64. Found: C, 28.68; H, 4.51; N, 1.59%.
Table 1
Infrared spectra in the carbonyl region for compounds 1–9
Compound
m(CO)
[Et4N][Re2(CO)6(OH)3] (1)a
1990 (s), 1870 (vs) [18]
1993 (s), 1876 (vs) [18]
1998 (s), 1880 (vs)
[Et4N][Re2(CO)6(OCH3)3] (2)b
[Et4N][Re2(CO)6(OH)(4-OC6H4NH2)2] (3)a
[Et4N][Re2(CO)6(4-OC6H4NH2)3] (4)a
2005 (s), 1888 (vs)
[Et4N][Re2(CO)6(OH)(3-OC6H4NMe2)2] (5)a 2003 (s), 1886 (vs)
2.3. X-ray crystallography
[Et4N][Re2(CO)6(OH)(3-OC6H4CN)2] (6)b
[Et4N][Re2(CO)6(OH)(4-OC6H4CN)2] (7)b
2009 (s), 1896 (vs)
2009 (s), 1898 (vs)
[Et4N][Re2(CO)6(OCH3)(4-OC6H4CN)2] (8)b 2012 (s), 1900 (vs)
Details of data collection and refinement are given in
Table 2. Crystals of complex 4 were grown from the va-
por diffusion of hexane into a THF solution of 4 at 5 ꢁC,
crystals of complexes 5–9 were grown by vapor diffusion
[Et4N][Re2(CO)6(OCH2CH2OH)3] (9)
1996 (s), 1879 (vs)
a
CH3CN solution.
THF solution.
b

Table 2
Crystal data, data collection, and structure refinement for 4–9
Compound
4
5
6
7
8
9
Empirical formula
Formula weight
Temperature (K)
C
33.81H42.21N409Re2
C34H49N3O10Re2
1032.16
C36H45N3011Re2
1068.15
C28H29N3O9Re2
923.94
C30H33Cl2N3O9Re2
1022.89
110
C20H35NO12Re2
853.89
1020.99
180
˚
Wavelength (A)
0.71073
monoclinic
P21/c
Crystal system
Space group
Unit cell dimensions
monoclinic
P21/n
monoclinic
P21/c
triclinic
ꢀ
triclinic
ꢀ
monoclinic
P21/c
P1
P1
˚
a (A)
10.3787(13)
22.931(3)
15.6321(17)
12.6007(11)
18.0688(15)
17.4926(15)
9.8829(2)
11.4110(2)
18.9479(4)
99.8120(10)
93.5560(10)
111.1800(10)
1945.49 (7)
2
9.6440(7)
31.158(3)
20.3608(16)
9.895(7)
11.737(9)
16.182(12)
85.596(6)
80.775(6)
72.164(7)
1765(2)
20.3628(19)
16.8214(15)
16.0927(15)
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
93.642(9)
107.622(4)
96.200(4)
95.514(3)
3
˚
Volume (A )
3712.8(8)
4
1.857
3795.8(6)
4
1.806
6082.3(8)
8
2.018
5486.7(9)
8
2.067
Z
2
1.925
7.056
Dcalc. (Mg/m3)
Absorption coefficient (mmꢀ1
Crystal size (mm)
1.823
6.277
)
6.570
6.429
8.009
8.874
0.41 · 0.36 · 0.24
1.58–24.97
ꢀ1 6 h 6 12
ꢀ5 6 k 6 27
ꢀ18 6 l 6 18
7756
0.17 · 0.14 · 0.04
2.76–26.00
ꢀ15 6 h 6 14
ꢀ21 6 k 6 19
ꢀ21 6 l 6 21
38006
0.24 · 0.20 · 0.14
2.20–30.58
ꢀ11 6 h 6 14
ꢀ16 6 k 6 9
ꢀ25 6 l 6 26
25444
0.31 · 0.28 · 0.20
2.12–26.00
ꢀ11 6 h 6 11
ꢀ38 6 k 6 29
ꢀ25 6 l 6 25
67688
0.32 · 0.30 · 0.25
2.19–25.00
ꢀ11 6 h 6 11
ꢀ13 6 k 6 13
ꢀ19 6 l 6 19
13620
0.30 · 0.29 · 0.20
1.76–25.50
ꢀ24 6 h 6 24
ꢀ20 6 k 6 20
ꢀ19 6 l 6 19
64000
h Range for data collection (ꢁ)
Limiting indices
Reflections collected
6505
0.0561
7333
0.0320
11650
0.0215
11744
0.0395
6142
0.0304
10210
0.0337
Independent reflections, Rint
Absorption correction
Refinement method
Goodness-of-fit on F2
Integration
full-matrix least squares on F2
SADABS
SADABS
SADABS
SADABS
SADABS
1.045
1.059
1.048
1.230
1.043
1.207
Final R indices (observed data)
R1
wR2
0.0549
0.1398
0.0207
0.0465
0.0251
0.0613
0.0246
0.0541
0.0338
0.0880
0.0382
0.0825
R indices (all data)
R1
0.0656
0.1486
0.0286
0.0508
0.0337
0.0636
0.0270
0.0548
0.0361
0.0904
0.0426
0.0856
wR2
Largest difference peak and hole (e/A )
3
˚
2.408 and ꢀ3.736
1.326 and ꢀ0.957
2.038 and ꢀ1.430
1.004 and ꢀ1.071
2.474 and ꢀ2.065
4.235 and ꢀ2407

1054
K.K. Klausmeyer, F.R. Beckles / Inorganica Chimica Acta 358 (2005) 1050–1060
Fig. 1. Thermal ellipsoid plot of 4 with atomic numbering scheme, ellipsoids are drawn at 30% probability.
resonance is at 158.7 ppm, and the C(ring)–NH2 carbon
is at 141.2 ppm.
Table 3
˚
Selected bond lengths (A) and angles (ꢁ) for 4
Re(1)–Re(2)
Re(1)–O(9)
Re(2)–O(9)
Re(2)–O(7)
O(8)–C(13)
N(1)–C(10)
N(3)–C(22)
3.1548(6) Re(1)–O(7)
2.136(7)
2.151(6)
2.151(7)
1.377(12)
1.333(11)
1.408(13)
Despite the inequivalence of the aminophenol ligands
in the X-ray crystal structure of 4, only a slight asymme-
2.148(6)
2.143(7)
2.153(6)
Re(1)–O(8)
Re(2)–O(8)
O(7)–C(7)
1
try is observed in the H NMR spectrum for the aro-
matic protons. This implies that on the NMR time
scale at least, the ligands are equivalent. The amine pro-
tons are at 3.76 ppm only slightly shifted downfield from
3. The carbon resonances are also shifted slightly down-
field at 201.3 for the carbonyls, 159.4 for the C(ring)–O
carbon, and 141.9 for the C(ring)–NH2 carbon.
For complex 5, the presence of the dimethylamino li-
gand in the ring causes a better resolved splitting of the
1
ring protons. In this case the H NMR spectrum shows
1.330(11) O(9)–C(19)
1.394(14) N(2)–C(16)
1.406(15)
O(9)–Re(1)–O(8)
O(9)–Re(2)–O(8)
O(9)–Re(2)–O(7)
C(7)–O(7)–Re(1)
Re(1)–O(7)–Re(2)
C(13)–O(8)–Re(1)
C(19)–O(9)–Re(2)
Re(2)–O(9)–Re(1)
71.5(3)
71.6(3)
71.4(2)
118.8(5)
94.7(3)
133.5(6)
130.0(6)
94.6(3)
O(7)–Re(1)–O(9)
71.6(3)
73.0(3)
72.7(2)
131.2(5)
132.1(6)
94.3(2)
132.7(6)
O(7)–Re(1)–O(8)
O(8)–Re(2)–O(7)
C(7)–O(7)–Re(2)
C(13)–O(8)–Re(2)
Re(2)–O(8)–Re(1)
C(19)–O(9)–Re(1)
four signals instead of two as in complex 6 (vide infra): a
triplet, singlet, doublet, and doublet corresponding to
the protons on the position 5, 2, 6, and 4, respectively.
Also the these signals appear upfield in comparison with
6 and this is due to the fact that the dimethylamino li-
gand is donating electron density to the ring instead of
withdrawing as in the case of the cyano ligand in com-
plex 6. The methyl protons associated with the dimeth-
ylamine appear as a singlet at 2.91 ppm. The 13C
NMR spectra the carbonyl groups peak at 200.01
ppm, the C(ring)–O at 165.50 ppm, the C(ring)–N at
151.9 ppm, and four signals at 128.9, 108.2, 104.9, and
103.7 ppm corresponding to the remaining carbons of
the ring that are more shielded than the analogous car-
bons in complex 6.
N(2)–H(2A)ꢁ ꢁ ꢁN(3)#2
3.098(15) N(3)–H(3A)ꢁ ꢁ ꢁN(1)#4
3.198(15)
Symmetry transformations used to generate equivalent atoms: #1 ꢀx ꢀ 1, ꢀy,
ꢀz + 1; #2 ꢀx + 1/2, y ꢀ 1/2, ꢀz + 3/2; #3 ꢀx ꢀ 1/2, y + 1/2, ꢀz + 3/2; # 4
cmꢀ1 consistent with a local C3v symmetry and also indi-
cating the presence of the fac-{Re(CO)3}+ core. All
compounds are soluble in acetone, acetonitrile and
THF.
3.1.2. NMR spectra
For each of the compounds 3–9 a proper integration
versus the protons of the Et4N cation was attained in the
1H NMR spectrum. For compound 3, the ring protons
resonate as multiplets at 6.90 and 6.52 ppm, the amine
protons are at 3.69 ppm. In the 13C NMR spectrum of
3, the carbonyl carbons are at 200.7 ppm, the C(ring)–O
In complex 6, the ring protons appear as multiplets at
7.47 and 7.17 ppm, this region is not as defined as in

K.K. Klausmeyer, F.R. Beckles / Inorganica Chimica Acta 358 (2005) 1050–1060
1055
Fig. 2. Thermal ellipsoid plot of 5 with atomic numbering scheme, ellipsoids are drawn at 40% probability.
Table 4
Selected bond lengths (A) and angles (ꢁ) for 5
protons in 7. The methoxy proton signal is a singlet at
4.30 ppm. The carbonyl resonance is at 198.1 ppm,
slightly up field with respect to 7. The C–N resonance
is shifted up field at 119.2 ppm. The signals for the meth-
oxy groups are at 65.3 ppm.
In complex 9, the methylene protons closest to the
bridging oxygen appears as triplet at 4.24 ppm, and
the methylene protons closest to the free hydroxy group
are at 3.69 ppm as a triplet. The 13C NMR spectrum
shows two distinctive peaks at 79.19 and 65.30 ppm that
correspond to the carbon closer to the metal center and
to the carbon closer to the free hydroxy group, respec-
tively. The carbonyl carbons resonate at 201.06 ppm.
˚
Re(1)–O(9)
Re(1)–O(7)
Re(2)–O(8)
O(7)–C(7)
N(1)–C(9)
N(1)–C(14)
N(2)–C(21)
2.119(2)
2.168(2)
2.171(2)
1.362(4)
1.406(5)
1.458(5)
1.438(7)
Re(1)–O(8)
Re(2)–O(9)
Re(2)–O(7)
O(8)–C(15)
N(1)–C(13)
N(2)–C(17)
N(2)–C(22)
2.164(2)
2.118(2)
2.179(2)
1.361(4)
1.450(5)
1.395(5)
1.449(6)
O(9)–Re(1)–O(8)
O(8)–Re(1)–O(7)
O(9)–Re(2)–O(7)
C(7)–O(7)–Re(1)
Re(1)–O(7)–Re(2)
C(15)–O(8)–Re(2)
Re(2)–O(9)–Re(1)
C(9)–N(1)–C(14)
C(17)–N(2)–C(21)
C(21)–N(2)–C(22)
N(2)–C(17)–C(16)
73.22(8)
71.27(9)
71.35(9)
131.87(19)
93.41(9)
130.30(19)
96.62(10)
117.9(3)
122.0(4)
113.5(4)
120.1(4)
O(9)–Re(1)–O(7)
O(9)–Re(2)–O(8)
O(8)–Re(2)–O(7)
C(7)–O(7)–Re(2)
C(15)–O(8)–Re(1)
Re(1)–O(8)–Re(2)
C(9)–N(1)–C(13)
C(13)–N(1)–C(14)
C(17)–N(2)–C(22)
N(2)–C(17)–C(18)
71.53(9)
73.08(8)
70.94(8)
130.8(2)
133.08(19)
93.76(9)
118.5(3)
115.9(3)
118.6(4)
121.3(4)
3.2. Description of the crystal structures
X-ray crystal structure determinations were carried
out for six of the derivatives synthesized and details of
data collection and refinement are given in Table 2.
All of the complexes contain an Re2(CO)6 core
with varying ligation around this core. All Re–C and
C–O(carbonyl) bond lengths and Re–C–O angles fall well
within normally observed values and each rhenium has
approximate octahedral geometry.
complex 5 where there is a well defined signal for every
proton of the ring. The signal corresponding to the
bridging hydroxide appears as a broad singlet at 2.87
ppm. In the 13C NMR spectrum the carbonyl signal ap-
pears at 199.72 ppm, the C(ring)–O at 166.03 ppm, and
the signal corresponding to C–N is at 119.7 ppm.
In the case of complex 7, the ring protons appear as a
doublet of doublets at 7.55 and 7.24 ppm, respectively.
The hydroxy proton signal is a singlet at 2.81 ppm.
The 13C NMR spectrum shows that the carbonyl groups
resonate at 199.4 ppm, the C(ring)–O at 169.3 ppm, and
the signal corresponding to C–N is at 120.4 ppm.
For complex 8, the ring protons are at 7.66 and 7.33
ppm, shifted downfield with respect to the analogous
3.2.1. Structure of complex 4
Complex 4, the trisubstituted aminophenol deriva-
tive, consists of three 4-aminophenol ligands bridging
2þ
the Re2ðCOÞ
core. A thermal ellipsoid plot for com-
plex 4 is provided in Fig. 1, and selected bond lengths
6
and angles are given in Table 3. The Re–Re nonbonding
˚
distance is 3.1548(6) A which is the same as that seen for
the phenoxide derivative [17]. While two of the amino-
phenol ligands (O8 and O9) are arranged such that the

1056
K.K. Klausmeyer, F.R. Beckles / Inorganica Chimica Acta 358 (2005) 1050–1060
ring carbons are roughly parallel to the Re–Re axis, sim-
ilar to that observed in the phenoxide derivative [17] and
similar tungsten derivatives [19], the third (O7) is rotated
nearly normal to the Re–Re axis. The Re–O–Re bond
angle is the same for all three groups at ꢂ94ꢁ, the Re–
O–C angles are 131.9 and 133.6ꢁ for O8 and 130.3 and
132.5ꢁ for O9, however O7 is quite different at 131.0ꢁ
for Re1–O7–C7 and 118.8ꢁ for Re2–O7–C7, suggesting
the hybridization of O7 appears to be closer to sp3 than
sp2. The observed difference is more obvious if one looks
at the average of the angles around the oxygen for the
three aminophenol ligands, for O8 and O9 the average
is 120.0ꢁ and 119.1ꢁ, respectively, for O7 it is 114.9ꢁ.
The Re–O bond lengths are similar to those previously
seen for the phenoxide derivative [17] ranging from
ecule of Et4N+ is present to balance charge, and the
asymmetric unit contains one half of a hexane solvent
molecule which is 60% occupied.
3.2.2. Structure of complex 5
Complex 5, the disubstituted dimethylaminophenol
derivative, is shown in Fig. 2 and selected bond dis-
tances and angles are in Table 4. This complex has
two 3-dimethylaminophenolate ions and one hydroxy
2þ
group connecting the Re2ðCOÞ
core. The Re–Re non-
˚
bonding distance in this complex is 3.1640(3) A. The
6
˚
average Re–O(ligand) bond length is 2.17 A, and the
˚
Re–O(hydroxy) is 2.118(2) A, for all of the complexes de-
scribed here the shortest Re–O bond lengths are associ-
ated with the hydroxy or methoxy moiety. The
dimethylamino groups are oriented anti to each other.
˚
2.136 to 2.153 A. The C–O bond lengths for the amino-
phenol ligands show some variation, the O9–C19 and
˚
The C(ring)–N distance is approximately 1.40 A for both
˚
O8–C13 bond lengths are 1.333 and 1.330 A, respec-
tively, appropriate for a partial C–O double bond in
conjugation with the aromatic ring. The O7–C7 bond
ligands. The Re1–O–Re2 angles are 93.41ꢁ for O7,
93.76ꢁ for O8, and 96.62ꢁ for O9 (hydroxy bridge) smal-
ler than the ones found for complex 4.
˚
length is longer at 1.377 A which suggests more of a sin-
gle bond character for this bond, concomitantly the N1–
3.2.3. Structure of complex 6
˚
C10 bond of this ligand is shorter at 1.394 A compared
to the N–C bonds of the other rings at 1.406 (N3) and
˚
1.408 (N2) A, these longer lengths compare quite favor-
ably with those seen in the analogous tungsten deriva-
˚
tive where the average N–C bond length is 1.439 A
[19]. Hydrogen bonding is observed for complex 4, N1
exhibits hydrogen bonding to N3 on adjacent molecule
Complex 6 presents a mixed ligand system with two
3-cyanophenolate ions and one hydroxide bound to
the Re2(CO)6 core. A thermal ellipsoid plot of this com-
plex is shown in Fig. 3, and selected bond lengths and
angles are in Table 5. The OH group is hydrogen
bonded to a symmetry equivalent with a distance of
˚
2.731(3) A. The nonbonding distance between Re1 and
˚
with a N–N distance of 3.198(15) A, N2 also has a
hydrogen bonding interaction with an N3 on an adja-
˚
cent molecule with a distance of 3.098(15) A. One mol-
˚
Re2 is 3.154 A, slightly smaller than in 5. The Re–O dis-
˚
˚
tances average 2.165 A for O7 and O8, and 2.12 A for
O9, where the shorter one corresponds to the hydroxyl
Fig. 3. Thermal ellipsoid plot of 6 with atomic numbering scheme, ellipsoids are drawn at 40% probability.

K.K. Klausmeyer, F.R. Beckles / Inorganica Chimica Acta 358 (2005) 1050–1060
1057
Table 5
Selected bond lengths (A) and angles (ꢁ) for 6
Table 6
Selected bond lengths (A) and angles (ꢁ) for 7
˚
˚
Re(1)–O(9)
Re(1)–O(8)
Re(2)–O(7)
O(7)–C(7)
N(1)–C(13)
C(9)–C(13)
2.118(2)
Re(1)–O(7)
2.1672(19)
2.122(2)
2.1660(18)
1.347(3)
1.157(4)
1.445(4)
Re(1)–O(7)
Re(1)–O(9)
Re(2)–O(9)
Re(3)–O(16)
Re(3)–O(18)
Re(4)–O(17)
O(8)–C(7)
2.153(3)
2.180(3)
2.171(3)
2.129(3)
2.182(3)
2.168(3)
1.355(5)
1.344(5)
1.152(7)
1.147(6)
Re(1)–O(8)
Re(2)–O(7)
Re(2)–O(8)
Re(3)–O(17)
Re(4)–O(16)
Re(4)–O(18)
O(9)–C(14)
O(18)–C(34)
N(2)–C(20)
N(4)–C(40)
2.177(3)
2.136(3)
2.180(3)
2.170(3)
2.135(3)
2.175(3)
1.342(5)
1.350(5)
1.147(6)
1.151(6)
2.1732(18) Re(2)–O(9)
2.1556(19) Re(2)–O(8)
1.359(3)
1.148(4)
1.442(4)
O(8)–C(14)
N(2)–C(20)
C(16)–C(20)
O(9)–Re(1)–O(7)
O(7)–Re(1)–O(8)
O(9)–Re(2)–O(8)
C(7)–O(7)–Re(2)
Re(2)–O(7)–Re(1)
C(14)–O(8)–Re(1)
Re(1)–O(9)–Re(2)
O(7)–C(7)–C(12)
N(2)–C(20)–C(16)
O(8)–C(14)–C(19)
O(9)–H(9B)ꢁ ꢁ ꢁO(11)#1
71.48(8)
71.36(7)
73.26(7)
132.97(17)
93.69(7)
132.74(17)
96.13(8)
121.1(3)
177.7(3)
120.7(2)
2.731(3)
O(9)–Re(1)–O(8)
O(9)–Re(2)–O(7)
O(7)–Re(2)–O(8)
C(7)–O(7)–Re(1)
73.18(7)
71.64(8)
O(17)–C(27)
N(1)–C(13)
N(3)–C(33)
71.72(7)
132.44(17)
C(14)–O(8)–Re(2) 133.85(17)
O(7)–Re(1)–O(8)
O(8)–Re(1)–O(9)
O(7)–Re(2)–O(8)
O(16)–Re(3)–O(17)
O(17)–Re(3)–O(18)
O(16)–Re(4)–O(18)
Re(2)–O(7)–Re(1)
Re(2)–O(9)–Re(1)
Re(4)–O(17)–Re(3)
C(34)–O(18)–Re(3)
N(1)–C(13)–C(10)
N(3)–C(33)–C(30)
71.34(11)
71.59(10)
71.62(11)
71.98(11)
71.61(11)
73.32(11)
95.16(11)
93.39(10)
93.55(10)
133.8(3)
O(7)–Re(1)–O(9)
O(7)–Re(2)–O(9)
O(9)–Re(2)–O(8)
O(16)–Re(3)–O(18)
O(16)–Re(4)–O(17)
O(17)–Re(4)–O(18)
Re(1)–O(8)–Re(2)
Re(3)–O(16)–Re(4)
C(34)–O(18)–Re(4)
Re(4)–O(18)–Re(3)
N(2)–C(20)–C(17)
N(4)–C(40)–C(37)
73.88(10)
74.41(10)
71.70(10)
73.30(11)
71.90(11)
71.78(10)
93.24(11)
95.69(12)
132.5(3)
Re(2)–O(8)–Re(1)
O(7)–C(7)–C(8)
N(1)–C(13)–C(9)
93.23(7)
120.1(2)
177.7(3)
O(8)–C(14)–C(15) 121.1(2)
93.02(11)
177.7(5)
179.4(6)
179.1(5)
179.9(7)
group. The Re–O–Re angles are 93.69ꢁ for O7, 93.23 for
O8, and 96.13 for O9. These values fall in the same
range as the one observed for complex 5 and 4. The
C–N average distance is 1.15 A that are in the normal
range for a C–N triple bond.
O(16)–H(16A)ꢁ ꢁ ꢁO(7)
Symmetry transformations used to generate equivalent atoms: #1 ꢀx + 1,
2.857(4)
O(7)–H(7A)ꢁ ꢁ ꢁN(4)#1
2.798(5)
˚
are provided in Table 7. Complex 8 is isostructural with
complex 7 with the exception of the replacement of the
hydroxyl group with the methoxy and hence there is
no hydrogen bonding, and the two will be discussed to-
3.2.4. Structure of complexes 7 and 8
Complexes 7 and 8 consist of the mixed ligand system
with two 4-cyanophenolate ions and one hydroxide (7),
or methoxide (8) ion bridging the Re2(CO)6 core. There
are two independent molecules in the asymmetric unit
for 7, with only minor differences between the two struc-
tures. The molecular structure of one of the independent
anions of 7 is shown in Fig. 4, and selected bond lengths
and angles are provided in Table 6. The anions in 7 are
hydrogen bonded together through the hydroxyl group
˚
gether. The Re–Re nonbonding distance is 3.140 A for
˚
one anion of 7 and 3.134 A for the other. The Re–Re
˚
nonbonding distance is slightly longer at 3.187 A in 8.
˚
The average Re–O bond length is 2.14 A for 7, and
˚
2.16 for 8, the O–C(ring) bond lengths average 1.34 A
˚
for 7 and 1.35 A for 8, while the C–N triple bond aver-
˚
˚
age is 1.14 A for 7 and 1.15 A for 8. For both 7 and 8 the
ring carbons of the phenolate are roughly parallel to the
Re–Re axis.
˚
with a distance of 2.85 A. A thermal ellipsoid plot for
8 is shown in Fig. 5 and selected bond lengths and angles
Fig. 4. Thermal ellipsoid plot of 7 with atomic numbering scheme, ellipsoids are drawn at 40% probability.

1058
K.K. Klausmeyer, F.R. Beckles / Inorganica Chimica Acta 358 (2005) 1050–1060
Fig. 5. Thermal ellipsoid plot of 8 with atomic numbering scheme, ellipsoids are drawn at 40% probability.
Table 7
3.2.5. Structure of complex 9
˚
Selected bond lengths (A) and angles (ꢁ) for 8
There are two independent molecules in the asymmet-
ric unit for 9, with the only major difference being a dis-
ordered ethylene glycol in one of the anions; otherwise
there is little difference between the two structures. The
molecular structure of one of the independent anions
of 9 is shown in Fig. 6, and selected bond lengths and
angles are provided in Table 8. For complex 9 each
dirhenium core has been completely substituted with
ethylene glycol ligands. The nonbonding distances be-
O(7)–Re(1)
O(8)–Re(1)
O(9)–Re(1)
C(13)–N(1)
C(7)–O(8)
C(21)–O(9)
2.183(4)
2.196(4)
2.101(4)
1.158(8)
1.349(6)
1.397(7)
O(7)–Re(2)
O(8)–Re(2)
O(9)–Re(2)
C(20)–N(2)
C(14)–O(7)
2.177(4)
2.191(4)
2.102(4)
1.138(8)
1.356(6)
N(1)–C(13)–C(10)
C(14)–O(7)–Re(2)
Re(2)–O(7)–Re(1)
C(7)–O(8)–Re(1)
C(21)–O(9)–Re(1)
Re(1)–O(9)–Re(2)
O(9)–Re(1)–O(8)
O(9)–Re(2)–O(7)
O(7)–Re(2)–O(8)
179.2(7)
N(2)–C(20)–C(17)
C(14)–O(7)–Re(1)
C(7)–O(8)–Re(2)
Re(2)–O(8)–Re(1)
C(21)–O(9)–Re(2)
O(9)–Re(1)–O(7)
O(7)–Re(1)–O(8)
O(9)–Re(2)–O(8)
177.9(7)
134.1(3)
93.91(14)
133.8(3)
130.9(4)
98.61(15)
73.09(15)
71.26(14)
69.77(13)
131.9(3)
127.2(3)
93.16(14)
128.9(4)
71.17(14)
69.57(13)
73.18(15)
˚
tween the rhenium centers are slightly less than 3.12 A
for both of the independent units; which is about 0.03
˚
A shorter than those containing aryloxide bridges. The
hybridization of the bridging oxygens appears to be
different for one of the ethylene glycol ligands in each
Fig. 6. Thermal ellipsoid plot of 9 with atomic numbering scheme, ellipsoids are drawn at 40% probability.

K.K. Klausmeyer, F.R. Beckles / Inorganica Chimica Acta 358 (2005) 1050–1060
1059
Table 8
˚
Selected bond lengths (A) and angles (ꢁ) for 9
Re(1)–O(7)
Re(1)–O(9)
Re(1)–O(11)
Re(1)–Re(2)
Re(3)–O(19)
Re(3)–O(21)
Re(4)–O(19)
O(7)–C(7)
2.156(5)
2.128(5)
2.124(5)
3.1178(5)
2.116(6)
2.150(5)
2.137(6)
1.446(9)
1.422(10)
1.434(10)
1.418(10)
1.418(12)
1.416(11)
1.479(12)
1.433(19)
1.43(2)
Re(2)–O(7)
Re(2)–O(9)
Re(2)–O(11)
Re(3)–Re(4)
Re(3)–O(23)
Re(4)–O(23)
Re(4)–O(21)
O(8)–C(8)
2.145(5)
2.128(5)
2.116(6)
3.1198(5)
2.128(5)
2.111(5)
2.147(5)
1.417(10)
1.424(10)
1.428(10)
1.429(9)
1.423(9)
1.508(11)
1.49(2)
O(9)–C(9)
O(10)–C(10)
O(19)–C(19)
O(21)–C(21)
O(23)–C(23)
C(7)–C(8)
O(11)–C(11)
O(20)–C(20)
O(22)–C(22)
O(24)–C(24)
C(9)–C(10)
C(12)–O(12)
C(12A)–O(12A)
C(21)–C(22)
C(11)–C(12)
C(11A)–C(12A)
C(19)–C(20)
C(23)–C(24)
1.49(2)
1.487(11)
1.497(12)
1.494(13)
O(11)–Re(1)–O(9)
O(9)–Re(1)–O(7)
O(11)–Re(2)–O(7)
O(19)–Re(3)–O(23)
O(23)–Re(3)–O(21)
O(23)–Re(4)–O(21)
C(17)–Re(4)–Re(3)
C(7)–O(7)–Re(1)
74.3(2)
72.3(2)
70.6(2)
O(11)–Re(1)–O(7)
O(11)–Re(2)–O(9)
O(9)–Re(2)–O(7)
70.3(2)
74.4(2)
72.5(2)
71.9(2)
75.0(2)
71.5(2)
121.0(5)
92.9(2)
127.2(5)
114(2)
75.1(2)
O(19)–Re(3)–O(21)
O(23)–Re(4)–O(19)
O(19)–Re(4)–O(21)
C(7)–O(7)–Re(2)
69.82(19)
70.19(19)
127.1(3)
118.2(5)
128.1(5)
94.2(2)
Re(2)–O(7)–Re(1)
C(9)–O(9)–Re(1)
C(9)–O(9)–Re(2)
Re(2)–O(9)–Re(1)
C(11)–O(11)–Re(2)
C(11)–O(11)–Re(1)
C(19)–O(19)–Re(3)
Re(3)–O(19)–Re(4)
C(21)–O(21)–Re(3)
C(23)–O(23)–Re(4)
Re(4)–O(23)–Re(3)
C(11A)–O(11)–Re(2)
C(11A)–O(11)–Re(1)
Re(2)–O(11)–Re(1)
C(19)–O(19)–Re(4)
C(21)–O(21)–Re(4)
Re(4)–O(21)–Re(3)
C(23)–O(23)–Re(3)
130.2(7)
128.1(9)
123.9(5)
94.4(2)
134(3)
94.7(2)
127.2(6)
121.7(4)
93.09(19)
128.7(5)
116.7(5)
124.2(5)
94.8(2)
O(8)–H(8A)ꢁ ꢁ ꢁO(12)#1
O(10)–H(10A)ꢁ ꢁ ꢁO(21)#1
O(20)–H(20A)ꢁ ꢁ ꢁO(7)#2
O(24)–H(24A)ꢁ ꢁ ꢁO(10)#4
O(12A)–H(12F)ꢁ ꢁ ꢁO(20)#3
2.717(17)
2.914(8)
2.899(8)
2.800(9)
2.98(5)
O(8)–H(8A)ꢁ ꢁ ꢁO(12A)#1
O(10)–H(10A)ꢁ ꢁ ꢁO(22)#1
O(22)–H(22A)ꢁ ꢁ ꢁO(24)#3
O(12)–H(12A)ꢁ ꢁ ꢁO(20)#3
2.79(6)
3.336(9)
2.689(9)
2.710(16)
Symmetry transformations used to generate equivalent atoms: #1 x, ꢀy + 3/2, z + 1/2; #2 x, ꢀ y + 1/2, z ꢀ 1/2; #3 x, ꢀy + 1/2, z + 1/2; #4 x, ꢀy + 3/
2, z ꢀ 1/2.
Fig. 7. Layers formed by 9 with Et4N+ between the layers of H-bonded anions.

1060
K.K. Klausmeyer, F.R. Beckles / Inorganica Chimica Acta 358 (2005) 1050–1060
independent unit. Two distinct bonding modes are
apparent, for Re–O9, Re–O11, Re–O19 and Re–O23
˚
the bond distance averages about 2.12 A with the aver-
age angle about the oxygen being greater than 115ꢁ. By
contrast the Re–O7 and Re–O21 distances average
˚
about 2.15 A with the average angle about the oxygen
being 110ꢁ. This would suggest that two of the bridging
oxygens are more of an sp2 hybrid with some double
bond character to the Re and the third has more of an
sp3 character and more of a single bond to the Re.
The anions of the structure are linked together by a
network of hydrogen bonds. The network forms a two
dimensional sheet formed from the hydrogen bond
interactions of the terminal OH groups of adjacent mol-
ecules. The tetraethylammonium cations occupy the
space between the sheets of anions forming a layer of ca-
tions. The layer-like structure is shown in Fig. 7. In gen-
eral the hydrogen bonding interactions are strong with
the Cambridge Crystallographic Data Centre as Deposit
Nos. 246579 for 4, 246581 for 5, 246580 for 6, 246584
for 7, 246582 for 8, and 246583 for 9. Copies of the data
can be obtained free of charge from The Director,
CCDC, 12 Union Road, Cambridge CB21EZ, UK
(fax: +44 1223 336 033; e-mail: deposit@ccdc.
cam.ac.uk).
Acknowledgements
This research was funded by a grant from the Robert
A. Welch Foundation (AA-1508). The Bruker X8
APEX diffractometer was purchased with funds received
from the National Science Foundation Major Research
Instrumentation Program Grant CHE-0321214.
˚
O–O distances ranging from 2.689(9) to 3.336(9) A.
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