Syntheses, Structures, and Properties of New Aluminum(III)-Molybdenum(IV) Heterometallic Clusters M2Al2[Mo3O4(O2CR) 8]2·nRCO2H (M = Na, K; R = Me, Et; n = 0, 1)

Full text of DOI:10.1021/ic951542y

Inorg. Chem. 1996, 35, 5097-5100
5097
Notes
Table 1. Crystallographic Data for Na2Al2[Mo3O4(O2CEt)8]2 (1)
and Na2Al2[Mo3O4(O2CCH3)8]2‚CH3CO2H (2)
Syntheses, Structures, and Properties of New
Aluminum(III)-Molybdenum(IV) Heterometallic
Clusters M2Al2[Mo3O4(O2CR)8]2‚nRCO2H (M )
Na, K; R ) Me, Et; n ) 0, 1)
empirical formula
fw
space group (No. 2) P1h
a, Å
b, Å
c, Å
Al2Mo6O40C48H80Na2 Al2Mo6O42C34H51Na2
1972.73
1807.34
P1h
13.008(8)
11.528(8)
13.713(11)
11.246(9)
104.20(8)
110.86(6)
70.10(8)
1546
13.896(10)
12.133(15)
109.46(9)
117.01(6)
90.21(7)
1810.7
1
Li Xu,* Zaofei Li, and Jinshun Huang*
R, deg
â, deg
γ, deg
V, Å3
Z
State Key Laboratory of Structural Chemistry,
Fujian Institute of Research on the Structure of Matter,
Chinese Academy of Sciences, Fuzhou,
Fujian 350002, P. R. China
1
D
calcd, g cm-3
1.81
1.94
T, °C
λ, Å
25
0.710 69
11.1
0.053
0.064
25
0.710 69
12.9
0.053
0.062
ReceiVed December 4, 1995
µ, cm-1
R(Fo)a
Rw(Fo)b
Introduction
Of the known kinds of triangular metal-metal-bonded cluster
compounds,1-3 the incomplete cubane-type [M3O4L9] (M3 )
Mo3,4,5 Mo2W,6 W37 ) is one of the most commonly encountered.
Their syntheses, structures, spectroscopy, dynamics, electro-
chemistry, and electronic structures have been subjects of
numerous reports.4-9 Such species contain a basic incomplete
cuboidal [M3O4]4+ unit which is surrounded by terminal L
ligands (L ) O, H2O, C2O42-, NCS-, edta, mida, F-, [9]aneN3)
to complete the octahedral coordination of each metal atom
(without counting M-M bonds). An alkylidyne-capped deriva-
tive with terminal pivalato ligands was also reported, which was
trapped by three chromium(III) ions to form the hexanuclear
cluster W3(CCH2CMe3)O3Cr3(O2CCMe3)12.10
a R ) ∑||Fo| - |Fc||/∑|Fo|. b Rw ) [∑w(||Fo| - |Fc||)2/∑w(|Fo|)2]1/2
.
Herein we wish to report the syntheses, structures, and
properties of the three new aluminum(III)-molybdenum(IV)
heterooctametallic clusters M2Al2[Mo3O4(O2CR)8]2‚nRCO2H (M
) Na, R ) Et, n ) 0 (1); M ) Na, R ) Me, n ) 1 (2); M )
K, R ) Et (3)), which possess the two incomplete cubane-type
cluster units [Mo3O4(O2CR)8]4- bridged with two Al(III) ions.
In contrast to the derivatives bridged by Cr(III) (M ) Mo (4),
W (5)), V(III) (M ) Mo (6), W (7)), Fe(III) (M ) Mo (8), W
(9)) and Mo(III) (M3 ) MoW2 (10), W3 (11)) reported
previously,11-13 the present clusters are diamagnetic and soluble
(M ) K (3)). This work may be of additional interest in that
Al-containing oxides and carboxylates have been known to have
many uses in catalytic, ceramic, paper, textile, and pharmaceuti-
cal industries.14
(1) Cotton, F. A. Polyhedron 1986, 5, 3.
(2) Cotton, F. A.; Shang, M. Y.; Sun, Z. S. Inorg. Chim. Acta. 1993,
212, 95.
(3) (a) Chisholm, M. H.; Hoffmann, D. M.; Hoffman, J. C. Inorg. Chem.
1984, 23, 3684. (b) Chisholm, M. H.; Folting, K.; Hoffman, J. C.;
Kirkkpatric, C. C. J. Am. Chem. Soc. 1981, 103, 5967.
(4) Zn2Mo3O8: (a) McCarroll, W. H.; Katz, L.; Ward, R. J. Am. Chem.
Soc. 1957, 79, 5410. (b) Ansell, G. B.; Katz, L. Acta Crystallogr.
1966, 21, 482.
Experimental Section
All reagents were analytical grade without further purification before
use. All manipulations were carried out in air.
(5) [Mo3O4]4+: (a) Bino, A.; Cotton, F. A.; Dori, Z. J. Am. Chem. Soc.
1978, 100, 5252. (b) Rodgers, K. R.; Murmann, R. K.; Schlemper, E.
O.; Schelton, M. E. Inorg. Chem. 1985, 24, 1313. (c) Cramer, S.;
Eidem, P. K.; Paffett, M. T.; Winkler, J. R.; Dori, Z.; Gray, H. B. J.
Am. Chem. Soc. 1983, 105, 799. (d) Gheller, S. F.; Brownlee, T. W.;
O'Connor, R. T. C.; Snow M. J. J. Am. Chem. Soc. 1983, 105, 1527.
(e) Bino, A.; Cotton, F. A.; Dori, Z. J. Am. Chem. Soc. 1979, 101,
3842. (f) Bino, A.; Cotton, F. A.; Dori, Z. Inorg. Chim. Acta. 1985,
99, 137. (g) Muller, A.; Ruck, A.; Dartmann, A.; Reinsch-Vogell, U.
Angew. Chem. 1981, 93, 493. (h) Schlemper, E. O.; Hussain, M. S.;
Murmann, R. K. Cryst. Struct. Commun. 1982, 11, 89. (i) Shreiber,
P.; Wieghardt, K.; Nuber, B. Inorg. Chim. Acta. 1993, 205, 199.
(6) [Mo2WO4]4+: (a) Patel, A.; Richens, D. T. J. Chem. Soc., Chem.
Commun. 1992, 274. (b) Patel, A.; Siddiqui, S.; Richens, D. T.;
Harman, M. E.; Harsthouse, M. B. J. Chem. Soc., Dalton Trans. 1993,
767.
Syntheses. Na2Al2[Mo3O4(O2CEt)8]2 (1). A mixture of Na2MoO4‚-
2H2O (0.96 g, 4.0 mmol), Mo(CO)6 (0.53 g, 2.0 mmol), AlCl3 (0.27 g,
2.0 mmol), and propionic anhydride (40 mL) was heated at 120 °C for
2 days. After the mixture was cooled to room temperature, well-formed
black crystals of 1 (1.21 g, 61%) were isolated. IR (cm-1): 811 (s),
791 (vs), 762 (s) [ν(Mo3O4)].
Na2Al2[Mo3O4(O2CMe)8]2‚MeCO2H (2). Na2MoO4‚2H2O (0.96 g,
4.0 mmol) was refluxed in acetic anhydride (30 mL) for 3 h. To the
solution obtained were added Mo(CO)6 (0.53 g, 2.0 mmol), AlCl3 (0.27
g, 2.0 mmol), and CH3CO2Na (0.1 g), and the resulting mixture was
heated at 120 °C for 3 days. After the mixture was cooled to room
temperature, well-formed black crystals of cluster 1 (0.31 g, 17%) were
isolated.
K2Al2[Mo3O4(O2CEt)8]2‚nEtCO2H (3). Cluster 3 was prepared
similarly to 1 using K2MoO4 with about 10% yield. IR (cm-1): 810
(s), 791 (vs), 765 (s) [ν(Mo3O4)]..
X-ray Crystallography. The crystallographic data for 1 and 2 are
summarized in Table 1. The structures were solved by direct methods
using MULTAN11/82 and refined by full-matrix least-squares proce-
(7) [W3O4]4+: (a) Sagawa, M.; Sasaki, Y. J. Am. Chem. Soc. 1985, 107,
5565. (b) Mattes, R.; Mennemann, K. Z. Z. Anorg. Allg. Chem. 1977,
437, 175; Angew. Chem. 1976, 88, 92. (c) Chaudhuri, P.; Wieghardt,
K.; Gebert, W.; Jibril, I.; Huttner, G. Z. Z. Anorg. Allg. Chem. 1985,
521, 23.
(8) (a) Richens, D. T.; Sykes, A. G. Inorg. Chem. 1982, 21, 418. (b) Paffet,
M. T.; Anson, F. C. Inorg. Chem. 1983, 22, 1347. (c) Ooi, B. L.;
Petrou, A. L.; Sykes, A. G. Inorg. Chem. 1988, 27, 3626.
(9) (a) Cotton, F. A. Inorg. Chem. 1964, 3, 1217. (b) Bursten, B. E.;
Cotton, F. A.; Hall, M. B.; Najjar, K. C. Inorg. Chem. 1982, 21, 302.
(c) Li, J.; Liu, C. W.; Lu, J. X. J. Chem. Soc., Faraday Trans. 1994,
39.
(11) Xu, L.; Liu, H.; Yan, D. C.; Huang, J. S.; Zhang, Q. E. J. Chem. Soc.,
Chem. Commun. 1993, 1507.
(12) Xu, L.; Liu, H.; Yan, D. C.; Huang, J. S.; Zhang, Q. E. J. Chem. Soc.,
Dalton Trans. 1994, 2099.
(10) (a) McCarley, R. E.; Philos. Trans. R. Soc. London 1982, A308, 141.
(b) Katovic, V.; Templeton, J. L.; McCarley, R. E. J. Am. Chem. Soc.
1976, 98, 5705.
(13) Xu, L.; Liu, H.; Huang, J. S.; Yan, D. C.; Zhang, Q. E., submitted for
publication.
(14) Mehrotra R. C. Metal Carboxylates, Academic Press: London, 1983.
S0020-1669(95)01542-4 CCC: $12.00 © 1996 American Chemical Society

5098 Inorganic Chemistry, Vol. 35, No. 17, 1996
Notes
Table 2. Positional and Thermal Parameters with Esd’s for 1
atom
x
y
z
Beq,a Å2
Mo1
Mo2
Mo3
Al1
O1
O2
0.95308(8)
1.12277(8)
0.93340(8)
1.2195(3)
0.9648(6)
1.1130(5)
0.8978(5)
1.0913(6)
0.7936(6)
0.9169(6)
1.0194(6)
0.7706(8)
1.1707(6)
1.3045(5)
1.1753(6)
1.1008(7)
0.9231(6)
0.7518(6)
0.8937(6)
0.866(1)
1.3423(6)
0.8072(6)
0.7579(6)
0.6660(6)
0.737(1)
0.619(1)
0.549(1)
0.8173(9)
0.7661(9)
0.648(1)
1.1131(9)
1.142(1)
1.264(1)
1.154(1)
1.204(1)
1.329(1)
1.3740(9)
1.4991(9)
1.507(1)
0.889(1)
0.879(1)
0.774(2)
0.8549(9)
0.867(1)
0.847(2)
0.6632(9)
0.541(1)
0.515(2)
0.8995(4)
0.35993(7)
0.27993(7)
0.24274(7)
0.5515(2)
0.2091(5)
0.4264(5)
0.3814(5)
0.2811(5)
0.3181(6)
0.5065(5)
0.3531(6)
0.1653(7)
0.1399(5)
0.3286(5)
0.2894(5)
0.0450(6)
0.0934(5)
0.1926(6)
0.2607(5)
-0.0114(7)
0.4910(5)
0.4002(5)
0.5020(5)
0.3299(6)
0.2443(9)
0.270(1)
0.28378(8)
0.39556(8)
0.39558(9)
0.5601(3)
0.2390(6)
0.4280(6)
0.4112(6)
0.5341(6)
0.1199(7)
0.2816(6)
0.1504(6)
-0.0349(8)
0.3620(6)
0.5262(6)
0.2563(6)
0.1490(7)
0.3741(7)
0.2662(7)
0.5512(6)
0.1653(9)
0.5450(6)
0.5769(6)
0.3061(6)
0.3082(7)
0.004(1)
-0.080(1)
-0.216(2)
0.2596(9)
0.163(1)
0.142(1)
0.164(1)
0.052(1)
0.090(1)
0.263(1)
0.307(1)
0.420(2)
0.5492(9)
0.588(1)
0.494(2)
0.277(1)
0.315(1)
0.325(2)
0.6104(9)
0.737(1)
0.827(1)
0.247(1)
0.145(2)
0.178(3)
0.0426(4)
2.32(2)
2.37(2)
2.55(2)
2.63(8)
3.1(2)
2.4(2)
2.1(2)
2.6(2)
3.5(2)
2.7(2)
3.2(2)
6.2(3)
3.4(2)
2.8(2)
3.1(2)
4.4(2)
3.8(2)
3.9(2)
3.5(2)
7.5(4)
3.1(2)
3.1(2)
2.8(2)
3.5(2)
3.7(3)
6.0(5)
7.7(6)
2.6(3)
3.5(3)
6.7(4)
3.7(3)
5.7(4)
9.6(6)
4.2(3)
6.0(4)
9.1(7)
3.0(3)
4.9(4)
10.4(7)
4.4(4)
6.3(5)
12.8(6)
3.2(3)
7.3(4)
8.6(6)
3.5(3)
7.2(6)
14.95(5)
4.0(1)
O3
O4
O11
O12
O13
O14
O21
O22
O23
O24
O31
O32
O33
O34
O41
O42
O43
O44
C11
C12
C13
C14
C15
C16
C17
C18
C19
C21
C22
C23
C24
C25
C26
C31
C32
C33
C34
C35
C36
C37
C38
C39
Na1
Figure 1. UV-vis spectra of 1 in HCl (2 M) (s) and DMF (-‚-)
solutions. The spectrum in HCl solution is very similar to that of the
[Mo3O4]4+ ion (- - -).
0.189(1)
0.5269(8)
0.5827(8)
0.607(1)
0.3178(9)
0.305(1)
0.288(2)
0.0546(9)
0.9687(9)
0.003(1)
0.4062(8)
0.3965(9)
0.296(2)
0.0019(9)
-0.0895(9)
-0.099(1)
0.3284(8)
0.322(1)
0.404(1)
0.2338(8)
0.168(1)
0.086(2)
0.0648(3)
Figure 2. ORTEP drawing of the cluster dianion of 1 with 50%
probability thermal ellipsoids.
a Beq ) (4/3)π[a2B(1,1) + b2B(2,2) + c2B(3,3) + ab(cos γ)B(1,2)
+ ac(cos â)B(1,3) + bc(cos R)B(2,3)].
Results and Discussion
Redox reactions of M0(CO)6 and MVIO42- (M ) Mo, W) in
refluxing carboxylic anhydride are an effective route to trinuclear
dioxo-capped carboxylate clusters of molybdenum(IV) and
tungsten(IV).15-19 This reaction system was recently success-
fully extended to the preparation of the Mo(IV) [or W(IV)]-
Cr(III) [or V(III)] mixed-metal clusters 4-7 using Cr(CO)6 or
NaVO3 in place of M(CO)6 or Na2MO4 in heating (120 °C)
instead of refluxing propionic anhydride.11,12 The formation
Figure 3. ORTEP drawing of the cluster dianion of 2 with 50%
probability thermal ellipsoids.
dures with all non-hydrogen atoms anisotropic except those of 2, for
which a molecule of acetic acid was refined isotropically. The
refinement of the acetic acid molecule of 2 based on a multiplicity of
1.0 would lead to the high-temperature factors (Beq is about 25) of the
oxygen atoms. On the basis of a refinement of the occupancy, a
multiplicity of 0.5 was used and gave reasonable temperature factors.
The highest peak in the final difference Fourier map for 2 was located
around the disordered acetic acid molecule. All calculations were
performed on a VAX-786 computer using the SDP program package
with scattering factors taken from the International Tables.
(15) Birnbaum, A.; Cotton, F. A.; Dori, Z.; Marler, D. O.; Reisner, G. M.;
Schwotzer, W.; Shaia, M. Inorg. Chem. 1983, 22, 2723.
(16) Powell, G.; Richens, D. T. Inorg. Chem. 1993, 32, 4021.
(17) Liu, H.; Xu, L.; Huang, J. S.; Yan, D. C.; Zhang, Q. E. Chin. J. Struct.
Chem. 1994, 13, 52.
(18) Na[MoW2O2(O2CMe)9]‚2H2O prepared by the reaction of Na2WO4‚-
2H2O and Mo(CO)6 in refluxing acetic anhydride has been confirmed
by a UV-vis spectrum similar to that of [MoW2O2(O2CMe)6-
(H2O)3]2+ 20 and an X-Ray structure determination, details of which
will be published elsewhere.
Physical Methods. UV-vis spectra and IR spectra were obtained
on Schimadzu UV-3000 and Digilab FTS-40 spectrophotometers.

Notes
Inorganic Chemistry, Vol. 35, No. 17, 1996 5099
Table 3. Positional and Thermal Parameters with Esd’s for 2
Table 4. Selected Bond Lengths (Å) and Angles (deg) for 1 and 2
atom
x
y
z
Beq, Å2
1
2
Mo1
Mo2
Mo3
Al1
O1
O2
0.29035(7)
0.38015(7)
0.42051(7)
0.4783(3)
0.2484(5)
0.4082(5)
0.4350(5)
0.5335(5)
0.1480(5)
0.2856(5)
0.1394(5)
-0.0133(7)
0.3451(5)
0.4824(6)
0.2218(5)
0.1344(6)
0.4091(6)
0.3213(6)
0.5937(5)
0.2030(6)
0.4865(6)
0.6200(5)
0.3398(5)
0.3663(6)
0.0377(9)
-0.033(1)
0.2794(8)
0.1921(8)
0.1349(9)
0.0192(9)
0.2458(8)
0.276(1)
0.4954(9)
0.520(1)
0.3166(9)
0.365(1)
0.6580(9)
0.7972(9)
0.3123(8)
0.227(1)
0.0555(3)
-0.036(2)
-0.155(2)
-0.144(2)
-0.238(2)
0.13605(6)
0.27205(6)
0.22866(6)
-0.0354(2)
0.2893(4)
0.1231(5)
0.0796(4)
0.2434(4)
0.1272(5)
-0.0189(4)
0.1797(5)
0.2758(6)
0.4295(4)
0.2896(5)
0.2965(5)
0.5044(5)
0.3703(5)
0.2158(5)
0.1781(5)
0.4659(5)
0.1458(5)
0.0069(5)
-0.0823(5)
0.0447(5)
0.1861(8)
0.133(1)
-0.0782(7)
-0.1497(7)
0.2481(7)
0.2760(9)
0.5101(8)
0.6130(7)
0.2376(8)
0.2918(9)
0.4557(7)
0.5409(7)
0.0883(8)
0.077(1)
0.44619(8)
0.61310(8)
0.39773(8)
0.2520(3)
0.4403(6)
0.6203(6)
0.3765(5)
0.5688(5)
0.2771(6)
0.4276(6)
0.5301(6)
0.2620(9)
0.6467(6)
0.8122(6)
0.6847(6)
0.5761(7)
0.3662(6)
0.1997(6)
0.3453(6)
0.3139(7)
0.8765(6)
0.2622(6)
0.2468(6)
0.1205(6)
0.220(1)
0.095(1)
0.3221(9)
0.284(1)
0.6258(9)
0.673(1)
0.6173(8)
0.641(1)
0.898(1)
1.035(1)
0.3338(9)
0.321(1)
0.3045(9)
0.312(1)
2.00(2)
2.00(2)
2.00(2)
2.22(6)
2.3(1)
2.2(1)
1.9(1)
2.1(1)
2.6(2)
2.5(2)
2.7(2)
5.4(3)
2.4(2)
2.7(2)
2.8(2)
3.4(2)
2.8(2)
2.9(2)
2.9(2)
4.5(2)
2.9(2)
2.7(2)
2.4(2)
2.9(2)
3.3(3)
5.0(4)
2.3(2)
3.4(3)
2.8(2)
3.8(3)
2.5(2)
3.6(3)
3.0(3)
5.2(4)
3.0(2)
4.4(3)
3.2(2)
5.9(4)
2.7(2)
3.8(3)
3.2(1)
9.6(7)a
11.2(8)a
4.5(5)a
4.5(5)a
Mo1-Mo2
Mo1-Mo3
Mo2-Mo3
Mo1-O1
Mo1-O2
Mo1-O3
Mo1-O11
Mo1-O12
Mo1-O13
Mo2-O1
Mo2-O2
Mo2-O4
Mo2-O21
Mo2-O22
Mo2-O23
Mo3-O1
Mo3-O3
Mo3-O4
Mo3-O31
Mo3-O32
Mo3-O33
Al1-O2
2.500(1)
2.518(1)
2.515(2)
2.007(7)
1.961(7)
1.924(7)
2.018(8)
2.098(7)
2.130(8)
1.999(8)
1.957(8)
1.897(8)
2.013(8)
2.105(8)
2.130(8)
2.027(8)
1.951(7)
1.894(7)
1.999(8)
2.103(8)
2.113(8)
1.902(8)
1.896(8)
1.861(9)
1.885(8)
1.909(8)
1.885(9)
2.321(9)
2.26(2)
Mo1-Mo2
Mo1-Mo3
Mo2-Mo3
Mo1-O1
Mo1-O2
Mo1-O3
Mo1-O11
Mo1-O12
Mo1-O13
Mo2-O1
Mo2-O2
Mo2-O4
Mo2-O21
Mo2-O22
Mo2-O23
Mo3-O1
Mo3-O3
Mo3-O4
Mo3-O31
Mo3-O32
Mo3-O33
Al1-O2
2.507(1)
2.526(1)
2.519(1)
2.001(6)
1.956(7)
1.936(7)
2.031(7)
2.101(6)
2.112(7)
2.004(7)
1.974(6)
1.894(7)
2.020(6)
2.124(8)
2.142(6)
2.053(6)
1.954(6)
1.909(7)
2.012(6)
2.105(7)
2.124(6)
1.912(8)
1.891(7)
1.863(7)
1.870(7)
1.892(7)
1.880(7)
2.351(7)
2.26(1)
O3
O4
O11
O12
O13
O14
O21
O22
O23
O24
O31
O32
O33
O34
O41
O42
O43
O44
C11
C12
C13
C14
C15
C16
C21
C22
C23
C24
C31
C32
C33
C34
C35
C36
Na1
O51
O52
C51
C52
Al1-O3
Al1-O3
Al1-O41
Al1-O42
Al1-O43
Al1-O44
O1-Na1
O14-Na1
O24-Na1
O24-Na1
O34-Na1
Al1-O41
Al1-O42
Al1-O43
Al1-O44
O1-Na1
O14-Na1
O24-Na1
O24-Na1
O34-Na1
2.40(2)
2.31(2)
2.27(1)
2.377(9)
2.336(9)
2.296(9)
O1-Mo1-O2
O1-Mo1-O3
O2-Mo1-O3
O1-Mo2-O2
O1-Mo2-O4
O2-Mo2-O4
O1-Mo3-O3
O1-Mo3-O4
O3-Mo3-O4
O2-Al1-O3
O2-Al1-O41
O2-Al1-O42
O2-Al1-O43
O2-Al1-O44
O3-Al1-O41
O3-Al1-O42
O3-Al1-O43
O3-Al1-O44
O41-Al1-O42
O41-Al1-O42
O41-Al1-O44
O42-Al1-O43
O42-Al1-O44
O43-Al1-O44
101.3(3)
100.9(3)
90.8(3)
101.8(3)
99.0(3)
93.4(4)
99.3(3)
98.1(3)
98.6(3)
94.2(3)
89.4(4)
88.8(4)
89.1(3)
175.9(4)
175.8(4)
91.2(3)
88.8(3)
89.8(4)
91.1(4)
89.1(4)
86.6(4)
177.8(4)
92.2(5)
90.0(4)
O1-Mo1-O2
O1-Mo1-O3
O2-Mo1-O3
O1-Mo2-O2
O1-Mo2-O4
O2-Mo2-O4
O1-Mo3-O3
O1-Mo3-O4
O3-Mo3-O4
O2-Al1-O3
O2-Al1-O41
O2-Al1-O42
O2-Al1-O43
O2-Al1-O44
O3-Al1-O41
O3-Al1-O42
O3-Al1-O43
O3-Al1-O44
O41-Al1-O42
O41-Al1-O43
O41-Al1-O44
O42-Al1-O43
O42-Al1-O44
O43-Al1-O44
101.8(3)
101.4(3)
90.6(3)
101.1(3)
100.2(3)
92.7(3)
99.0(2)
98.0(3)
98.9(3)
92.7(3)
89.9(3)
87.9(3)
89.7(4)
177.1(3)
177.2(3)
90.0(4)
90.3(3)
89.9(4)
91.2(3)
88.7(3)
87.4(3)
177.5(4)
93.1(3)
89.3(3)
0.1390(8)
0.1674(9)
0.4189(3)
0.454(2)
0.529(2)
0.478(2)
0.1090(8)
-0.0242(9)
0.3653(4)
0.106(2)
-0.031(3)
0.049(2)
0.460(2)
0.073(2)
a Atoms were refined isotropically.
of these species may be understood on the grounds that reduction
of Na2MO4 or oxidation of M(CO)6 produced the incomplete
cuboidal units [M3O4(O2CEt)8]4- which were trapped by Cr3+
(or V3+) and Na+ ions in the reaction to form the insoluble
chain products. These reported synthetic methods are, however,
limited and are not adaptable to the preparation of, for example,
the present Al(III)-bridged clusters. We thus consider using
the redox reaction of Na2MoO4 and Mo(CO)6 to produce
[Mo3O4(O2CEt)8]4- ions which are expected to be trapped by
Al3+ and Na+ ions in the reaction to yield Al(III)-bridged
derivatives. As might be expected, reaction of Na2MoO4, Mo-
(CO)6, and AlCl3 has produced the desired Al(III)-bridged
cluster 1 as well-formed black crystals in excellent yield. The
acetate 2 is prepared similarly using acetic anhydride but in
low yield due to the simultaneous formation of a considerable
amount of the insoluble dioxo-capped cluster Na[Mo3O2(O2-
CMe)9].15 The potassium salt 3, which has been confirmed by
the IR spectrum identical to that of 1, can also be prepared
similarly to 1 using K2MoO4. However, the considerable
solubility in the reaction solution as will be described leads to
a low yield.
2-
The structures of the cluster dianions, Al2[Mo3O4(O2CR)8]2
(R ) Et (1), Me (2)) are shown in Figures 2 and 3, respectively.
Atomic coordinates and selected bond lengths and angles for 1
and 2 are listed in Tables 2-4. Table 5 summarizes some
important mean bond lengths of 1, 2, 4-11, and related
complexes for a structural comparison. As expected, the
structures are identical to those of 4-7 reported.11,12 The Al-
(21) Taylor, D. Aust. J. Chem. 1978, 31, 1455.
(22) Anson, C. E.; Saard, M. C.; Bourke, J. P.; Cannon, R. D.; Jayasooriya,
U. A.; Powell, A. K. Inorg. Chem. 1993, 32, 1502.
(23) Cotton, F. A.; Lewis, G. R.; Mott, G. M. Inorg. Chem. 1982, 21, 331.
(24) Black, A. B.; Fraser, L. R. J. Chem. Soc. 1975, 193.
(19) Xu, L.; Yu, X. F. Chin. J. Struct. Chem. 1990, 9, 150.
(20) Wang, B.; Sasaki, Y.; Nagasawa, A.; Ito, T. J. Am. Chem. Soc. 1986,
108, 6059.

5100 Inorganic Chemistry, Vol. 35, No. 17, 1996
Notes
ref
Table 5. Comparison of Mean Bond Lengths (Å) in Clusters 1, 2, 4-11, and Related Complexes
a
d
e
complex
M-M
M-Ob
M-Ob*b
M-Otc
M-Ocp
M-Oba
M′-Ob* M′-Oba
Na2Al2[Mo3O4(O2CCH3)8]2 (1)
Na2Al2[Mo3O4(O2CC2H5)8]2 (2)
Na2Cr2[Mo3O4(O2CC2H5)8]2 (4)
Na2Cr2[W3O4(O2CC2H5)8]2 (5)
Na2V2[Mo3O4(O2CC2H5)8]2 (6)
Na2V2[W3O4(O2CC2H5)8]2 (7)
Na2Fe2[Mo3O4(O2CC2H5)8]2 (8)
Na2Fe2[W3O4(O2CC2H5)8]2 (9)
2.518(1)
2.511(2)
2.5198(9) 1.907(4)
2.5313(9) 1.927(9)
2.519(1)
2.5328(6) 1.926(6)
1.908(7)
1.895(8)
1.957(7) 2.022(7) 2.023(7)
1.948(8) 2.010(8) 2.011(8)
1.952(5) 2.010(4) 2.026(4)
1.972(8) 2.012(9) 2.059(9)
1.953(6) 2.005(6) 2.026(7)
1.974(6) 2.013(6) 2.057(6)
1.957(7) 2.010(8) 2.027(7)
2.121(7) 1.901(8) 1.877(8) this work
2.113(8) 1.896(8) 1.885(8) this work
2.114(5) 1.947(4) 1.973(5) 11,12
2.110(9) 1.929(8) 1.986(9) 11,12
2.119(8) 1.985(6) 1.989(8) 11,12
2.107(7) 1.962(6) 2.012(6) 11,12
2.121(8) 1.992(8) 1.993(8) 13
1.905(6)
2.517(1)
2.535(1)
1.915(7)
1.92(1)
1.909(9)
1.90(2)
1.915(7)
1.891(15)
1.911
1.98(2)
2.02(2)
2.04(2)
2.11(2)
1.98(2)
2.02(2)
13
Na2Mo2[M3O4(O2CC2H5)8]2 (10) 2.520(1)
Na2Mo2[W3O4(O2CC2H5)8]2 (11) 2.530(2)
1.959(9) 2.011(9) 2.034(9)
2.104(9) 2.028(6) 2.079(9) 13
1.97(2)
1.99(2)
2.06(2)
2.020(3)
2.021(14)
2.039
2.10(3)
2.03(2)
2.10(2)
13
5f
[Mo3O4(C2O4)3(H2O)3]2-
[Mo2WO4(NCS)9]4-
[W3O4(NCS)9]4-
2.493(3)
2.521(5)
2.534
6a
7a
21
[Al(ox)3]3-
1.911(4)
[Cr3O(O2CEt)6F3]2-
[V3O(O2CMe)8(THF)3]
[Fe3O(O2CCMe3)6(MeOH)3]+
1.909(4) 1.974(3) 22
1.910(6) 2.00(2)
1.905(5) 2.02(2)
23
24
a Bridging M atom. a Bridging M and M′ atoms. c Terminal C2H5CO2. d Capping O atoms. e Bridging C2H5CO2.
Oca (O2CEt) bond lengths in 1 and 2, which are close to those
in [Al(ox)3]3- 21
are nearly equal to the Al-Ob* (O2 or O3)
bonds, similar to the situations in 6-8 but unlike those in 4
and 5, where the Cr-Ob* bonds are significantly shorter than
the Cr-Oca bonds. This may be assignable to different degrees
of the M′-Ob* d-p π bonds.
The acetate 2 contains an acetic acid molecule that is weakly
bound to Na+ (Na-O ) 2.83 Å). The remaining Na-O bonds
[average 2.32(1) Å] are similar to those in 1 and 4-11 [average
2.31(1) Å].
Clusters 1-3 are all air stable, like 4 and 5 but in contrast to
6-11, which are stable in air for only about 1 month. These
species have different degrees of solubility or stability in acid
solution. Clusters 1-3 dissolve in HCl (2 M) to produce red
solutions. Interestingly, as shown in Figure 1, the UV-vis
spectrum is identical to that of red [Mo3O4]4+ aqua ion reported
previously,5,6 suggesting occurrence of cleavage of the Al-O
bonds and formation of isolated [Mo3O4]4+ units. A similar
situation applies for 6 and 8 although the peak at λmax ) 510
nm for 8 is not obvious, presumably caused by the effect of
Fe3+ ions. In contrast, 4 only slowly dissolves upon heating in
HCl solution and 5 is not soluble, displaying considerably higher
stability in acid solution. This may be attributed to the stronger
Cr-O bonding enhanced by the crystal field stabilization energy.
In contrast to the sodium salts (1, 2, 4-9), which are all
insoluble in water and common organic solvents such as THF,
DMF, or EtOH at room temperature, as expected for rather
strong Na-O bonds of considerable covalence (ca. 2.31 Å vs
2.42 Å for a Na-O bond) in the infinite-chain structure, the
potassium salt 3 can be easily dissolved in these solvents because
of the weaker K-O ionic bonds. Nevertheless, 1-9 can all be
slowly dissolved upon heating (>80 °C) in DMF, giving brown
solutions, unlike the situations in acid solution as described
above. These indicate that the dissolution results from cleavage
of the Na(K)-O bonds only. The UV-vis spectrum of 1 in
DMF solution given in Figure 1, similar to that of 3, shows a
peak at λmax ) 560 nm (sh) which differs clearly from that of
1 in HCl solution perhaps because of the retention of the Al-O
bonds and solvent effects. Such a peak is not observed in the
spectra of the V, Cr, and Fe complexes.
Cyclic voltammetry measurements of 1-3 in DMF solution
with 0.1 M Bu4NBF4 as supporting electrolyte show no evident
redox signal in the range -1.5 to +1.5 V vs SCE, indicating
the high resistance toward oxidation and reduction. This is
unlike the situation in acid solution of the [Mo3O4]4+ ion, where
the three-electron redox process readily occurs.8
,
Acknowledgment. This work was supported by the National
Science Foundation of China.
Supporting Information Available: Listings of detailed crystal-
lographic data, complete bond lengths and angles, and thermal
parameters for 1 and 2 (9 pages). Ordering information is given on
any current masthead page.
IC951542Y