The syntheses and X-ray crystal structures of novel transition metal cluster arrays containing 2-5 coordinated [(CO)9Co3(μ3-CCOO)]- ligands in a variety of geometries

Article abstract of DOI:10.1016/S0277-5387(98)00415-X

Reaction of (CO)₉Co₃(μ₃-CCOOH) with metal trifluoroacetates leads to the isolation of Cr₂{μ-OOC-CCo₃(CO)₉} ₂{μ-OOCCF₃}₂(THF)₂, 1, and Sm₂{μ-OOCCCo₃(CO)₉} ₂{μ-OOCCF₃}₄{(CO)₉Co ₃CCOOH}₂(THF)₂·2THF, 2, which are cluster substituted analogs of known organic carboxylates. Reaction of Pt(II) acetate, prepared in situ, with (CO)₉Co₃(μ₃-CCOOH) leads to PtCo{μ-OOCCCo₃(CO)₉}₃(μ-OOCCH ₃){(CO)₉Co₃CCOOH}, 3, which contains an unusual Pt(II)Co(II) dimeric core. Reaction of Zn(OH)₂ with (CO)₉Co₃(μ₃-CCOOH) in THF leads to Zn₄(μ₄-O){μ-OOC-CCo₃(CO) ₉}₆ but in 2-MeTHF the reaction leads to ZnCo{μ-OOCCCo₃(CO)₉}₃{Co(CO) ₄}{2-(CH₃)C₄H₇O}, 4. This compound features the presence of a [Co(CO)₄]^- moiety coordinated to a Co(II) center. Reaction of Cr(II) acetate with (CO)₉Co₃(μ₃-CCOOH) in noncoordinating solvents results in CoCr₂(μ₃-O){μ-OOCCCo₃(CO) ₉}₄(μ-OOCCH₃)₂{(CO) ₉Co₃CCOOH}₂(H₂O)·C ₇H₈, 5a, and Cr₃(μ₃-O){μ-OOCCCo₃(CO)₉} ₄(μ-OOCCH₃)₂{(CO)₉Co ₃CCOOH}(CH₃OOH)₂·C₇H ₈, 5b, which are cluster ligand analogs of known organic carboxylate oxo metal trimers. Finally, deprotonation of (CO)₉Co₃(μ₃-CCOOH) with a bulky base inhibits the base degradation of the tricobalt cluster sufficiently such that [C₁₀H₆(N(CH₃)₂) ₂H][Co₂{μ-OOCCCo₃(CO)₉} ₃{OOCCCo₃(CO)₉}₂], 6, can be isolated. All compounds are structurally characterized by X-ray crystallography and selected spectroscopic techniques.

Full text of DOI:10.1016/S0277-5387(98)00415-X

Polyhedron 18 (1999) 1869–1880
The syntheses and X-ray crystal structures of novel transition metal cluster
arrays containing 2–5 coordinated [(CO)9Co3(m3-CCOO)]2 ligands in a
variety of geometries
Victor Calvo-Pereza, Maoyu Shanga, Glenn P.A. Yapb, Arnold L. Rheingoldb, Thomas P. Fehlnera,
*
aDepartments of Chemistry and Biochemistry, University of Notre Dame, Notre Dame IN 46556, USA
bUniversity of Delaware, Newark, DE 19716, USA
Received 3 April 1998; accepted 23 October 1998
Abstract
Reaction of (CO)9Co3(m3-CCOOH) with metal trifluoroacetates leads to the isolation of Cr2hm-OOC-CCo3(CO)9j2hm-
OOCCF3j2(THF)2, 1, and Sm2hm-OOCCCo3(CO)9j2hm-OOCCF3j4h(CO)9Co3CCOOHj2(THF)2?2THF, 2, which are cluster substituted
analogs of known organic carboxylates. Reaction of Pt(II) acetate, prepared in situ, with (CO)9Co3(m3-CCOOH) leads to PtCohm-
OOCCCo3(CO)9j3(m-OOCCH3)h(CO)9Co3CCOOHj, 3, which contains an unusual Pt(II)Co(II) dimeric core. Reaction of Zn(OH)2 with
(CO)9Co3(m3-CCOOH) in THF leads to Zn4(m4-O)hm-OOC-CCo3(CO)9j6 but in 2-MeTHF the reaction leads to ZnCohm-OOC-
CCo3(CO)9j3hCo(CO)4jh2-(CH3)C4H7Oj, 4. This compound features the presence of a [Co(CO)4]2 moiety coordinated to a Co(II)
center. Reaction of Cr(II) acetate with (CO)9Co3(m3-CCOOH) in noncoordinating solvents results in CoCr2(m3-O)hm-OOC-
CCo3(CO)9j4(m-OOCCH3)2h(CO)9Co3CCOOHj2(H2O)?C7H8, 5a, and Cr3(m3-O)hm-OOCCCo3(CO)9j4(m-OOCCH3)2h(CO)9Co3C-
COOHj(CH3OOH)2?C7H8, 5b, which are cluster ligand analogs of known organic carboxylate oxo metal trimers. Finally, deprotonation
of (CO)9Co3(m3-CCOOH) with a bulky base inhibits the base degradation of the tricobalt cluster sufficiently such that
[C10H6(N(CH3)2)2H][Co2hm-OOCCCo3(CO)9j3hOOCCCo3(CO)9j2], 6, can be isolated. All compounds are structurally characterized by
X-ray crystallography and selected spectroscopic techniques.
1999 Published by Elsevier Science Ltd. All rights reserved.
Keywords: Cobalt; Chromium; Zinc; Platinum; Samarium; Clusters; Carboxylates
1. Introduction
trated some of the differences a typical metal cluster, e.g.
(CO)9Co3(m3-C-), imparts to the coordinating ability of
the ligand functionality, e.g. -COO2, towards various
cationic metal centers [8]. In addition, some of the
compounds have found use as precursors to novel
heterogeneous hydrogenation catalysts [9–11].
As the cluster acid, (CO)9Co3(m3-CCOOH), degrades
under basic conditions, the synthetic challenge has been to
find ways to convert the acid to the [(CO)9Co3(m3-
CCO2)]2 coordinated ligand without decomposing the
cobalt cluster into organic and inorganic fragments. Some
of these compounds have been studied in detail and we
have provided efficient routes for gram scale syntheses
[5,8,12–20]. As described herein, other approaches have
now been explored and have uncovered an additional set of
new compounds with varied cluster ligand coordination
numbers as well as unusual cationic cores. The result is a
set of cluster arrays that mimic most of the classical
geometries of coordination chemistry and provide some
unique spatial arrays as well. In the following we describe
There has been considerable interest in recent years in
the logical synthesis of large molecular systems. The
approaches utilized to date are varied and lead, for
example, to one-dimensional chains [1] or rings [2] or
two-dimensional sheets [3] or three-dimensional dendritic
moieties [4]. Both organic reactions as well as coordina-
tion reactions have been employed to yield an impressive
variety of new substances with interesting properties. We
have explored a related area namely the synthesis of
transition metal cluster arrays using the concept of a
functionalized cluster as a ligand towards a cationic metal
center [5]. While our compounds derive from monofunc-
tional clusters, others have used bifunctional clusters to
form linear cluster arrays [6,7]. Our work has also illus-
*
Corresponding author. Tel.: 11-219-631-7058; fax: 11-219-631-
6652.
E-mail address: Thomas.P.Fehlner.1@nd.edu (T.P. Fehlner)
0277-5387/99/$ – see front matter
PII: S0277-5387(98)00415-X
1999 Published by Elsevier Science Ltd. All rights reserved.

1870
V. Calvo-Perez et al. / Polyhedron 18 (1999) 1869–1880
the preparation and structures of these new cluster metal
carboxylates.
2,600). Analysis (dried under vacuum). Found, C 24.38%,
7.80%, Co 24.14%, Cr 7.17%. Calculated for
F
C26Co6Cr2F6O26: C 26.26%, F 8.31%, Co 25.57%, Cr
7.58%.
2. Experimental
2.1.2. Sm2 hm-OOCCCo3(CO)9 j2 hm-OOCCF3 j4
h(CO)9Co3CCOOHj2(THF)2?2THF, 2
2.1. Syntheses
To
0.120
g
(0.228
mmol)
of
solid
Sm(OOCCF3)3(H2O)2 dispersed in 10 ml THF was added
a solution of 0.500 g (1.029 mmol) of (CO)9Co3(m3-
CCOOH) in 20 ml THF. After mixing at 308C for 1 h, the
solvent was removed under vacuum. The solid was ex-
tracted with hot toluene, filtered, kept at 108C for 1 day,
and then at 2208C. Well formed crystals of 2 were isolated
in 88% yield based on samarium (0.310 g, 0.104 mmol).
Recrystallization produced X-ray quality crystals. IR (KBr,
cm21): 2113 (w), 2051 (s), 1707 (m), 1607 (m), 1479 (w),
1488 (w), 1365 (w), 1339 (w), 1264 (w), 1205 (m), 1153
(w), 797 (w), 781 (w), 720 (w), 544 (w), 500 (w). EPR
(X-band) powder, g: 2.17, Dp–p: 55 G.
Anhydrous
CrCl2,
CF3COOH,
Na[CF3COO],
Ag[CH3COO], and PtBr2 were purchased form Aldrich
and used as received. Proton sponge C10H6(N(CH3)2)2
(Aldrich) was sublimed under vacuum at 308C on a
Schlenk line. Samarium metal (American Potash and
Chem. Corp, 99.9%) was dissolved in aqueous CF3COOH
(50%) and after 1 week, the clear solution was slow-
ly
evaporated
to
yield
white
crystals
of
Sm(OOCCF3)3(H2O)2. Zn(OH)2 gel was prepared from
4.4 g Zn(CH3COO)2?2H2O (Aldrich) aqueous solution and
diluted ammonia and the mixture was brought to pH 8.0.
The gel, thus obtained was centrifuged three times with
deionized water and later washed thoroughly on a column
with deionized water until no further base was released.
2-Methyl-tetrahydrofuran was purchased from Aldrich and
distilled over Na before use. (CO)9Co3(m3-CCOOH) was
prepared as described previously [21]. Cr2(OOCCF3)4?
(OEt2)2 was prepared as described in the literature [22].
All the solvents used were distilled under nitrogen just
before use. All reactions were performed under Ar on a
Schlenk line using standard methods. IR: Nicolet 205
FTIR. UV–Vis: Perkin-Elmer Model 6 or 19 spec-
trophotometers. MS: JEOL JMS-AX 505HA mass spec-
trometer in FAB mode. NMR: GN 300 MHz spectrometer.
EPR: Brucker 1600 EPR spectrometer working in the
X-band and equipped with an Oxford variable temperature
controller. XPS: Kratos SAM 800 spectrometer with a
magnesium anode using C1s at 285.0 eV as reference.
2.1.3. PtCohm-OOCCCo3(CO)9 j3(m-OOCCH3 )
h(CO)9Co3CCOOHj, 3
Reaction of PtBr2 and 2 AgOOCCH3 in water followed
by removal of the AgBr by filtration yielded a brown–
yellow solid after removal of the solvent. Presumably this
is the simple acetate as IR spectra showed that it is not
Pt4(OOCCH3)8. The latter compound, prepared separately
using the closely related method of Yamaguchi et al. [23],
yielded only Pt metal on reaction with the cluster acid. A
solution of 0.40 g of the fresh Pt intermediate was
combined with 1.31 g (2.70 mmol) of (CO)9Co3(m3-
CCOOH) in 100 ml THF and the mixture was stirred in
the dark at 458C for 4 days. After filtration, the THF was
removed under vacuum and the solid extracted with 70 ml
toluene. The volume of the solution was reduced to 25 ml
at 608C and slowly cooled to 108C at which temperature it
was kept for 2 weeks. Crystalline 3 (0.20 g, 0.09 mmol)
was isolated. IR (KBr, cm21) 2946 (w), 2110 (m), 2047
(vs), 1642 (w), 1625 (sh), 1584 (w), 1355 (m), 1328 (m),
1279 (w), 1069 (w), 768 (w), 722 (m), 546 (w), 527 (m),
499 (m), 462 (w). MS (negFAB, NBA, Xe) m/z 2250.1
(10%); calculated m/z 2254. Analysis. Found: C 25.18%,
H,0.5%, Co 34.3%, Pt 7.70%. Calculated for
C46H4Co13PtO46: C 24.52%, H 0.18%, Co 33.99%, Pt
8.66% .
2.1.1. Cr2 hm-OOC-CCo3(CO)9 j2 hm-OOCCF3 j2(THF)2 , 1
A 400 mg (0.57 mmol) amount of Cr2(OOCCF3)4?
(OEt2)2 plus 80 mg (0.59 mmol) CF3COONa and 300 mg
(0.62 mmol) of (CO)9Co3(m3-CCOOH) in 10 ml THF
plus 20 ml toluene afforded a deep purple–blue solution.
Stirring under argon at 308C for 45 min gave a black–
brown solution. The solvents were removed under vacuum
and the black solid was dispersed in 30 ml freshly distilled
toluene with sonication. The extract was quickly filtered on
a fine frit funnel to remove the solids. The filtrate was left
at room temperature for 1 day in the dark and then moved
to 48C for a week. Crystalline 1 in 32% yield (260 mg,
0.18 mmol) based on Cr was isolated. IR (KBr, cm21):
2988 (w), 2866 (w), 2110 (w), 2055 (vs), 2040 (sh), 1986
(m), 1659 (m), 1499 (w), 1473 (w), 1388 (m), 1343 (w),
1203 (m), 1160 (m), 1080 (w), 1041 (w), 822 (w), 852 (w),
792 (w), 757 (m), 728 (m), 558 (m), 529 (m), 504 (m), 422
(w). UV–Vis (toluene, nm, M21cm21): 380 sh, 516 (´
2.1.4. ZnCohm-OOCCCo3(CO)9 j3 hCo(CO)4 j
h2-(CH3 )C4H7Oj, 4
A 58 mg amount of Zn(OH)2 gel (0.090 mmol of Zn)
with 1.00 g (2.06 mmol) of (CO)9Co3CCOOH dissolved
in 15 ml THF’ (52-(CH3)C4H7O) was stirred for 30 m at
room temperature (RT) and the black–brown mixture was
then sonicated for 15 min to further disperse the gel. The
solvents were removed at 378C under vacuum and the
dark–brown solid was dispersed in 35 ml freshly distilled

V. Calvo-Perez et al. / Polyhedron 18 (1999) 1869–1880
1871
toluene plus 1 ml THF’ yielding a brown solution and a
2.1.7. [C10H6(N(CH3 )2 )2H][Co2 hm-OOCCCo3(CO)9 j3
hOOCCCo3(CO)9 j2 ], 6
dark-brown precipitate. The brown solution was filtered
and the filtrate stood at room temperature for one day and
then 2208C for a week. Crystals of 4 were obtained in
73% yield based on Zn (120 mg, 0.066 mmol) by layering
with hexane. Note that the use of THF leads to the
production of Zn4(m4-O)hm-OOC-CCo3(CO)9j6 [5] in
70% yield. IR (KBr cm21): 2960 (w), 2110 (m), 2055–
2045 (vs), 1974 (s), 1963 (s), 1944 (s), 1565 (m), 1496 (w),
1379 (s), 1340 (m), 1085 (w), 793 (w), 751 (m), 722 (m),
A 45-mg (0.093 mmol) amount of (CO)9Co3CCOOH
were placed in a Schlenk tube together with 20 mg (0.093
mmol) of proton sponge C10H6(N(CH3)2)2 and 2 ml of
CH2Cl2. After reaction for 2 h at 458C the warm solution
was filtered and layered with 4 ml of toluene and left
standing at room temperature for 5 days. Nicely shaped
black crystals (22 mg, 0.0079 mmol), suitable for X-ray
slowly grew from this solution. IR: (KBr pellet, cm21):
2109(m), 2040 (s), 1580 (m), 1541 (m), 1382 (m), 1338
(m), 749 (m), 723 (m), 551 (m), 528 (m), 501 (m), 408 (m).
(CH2Cl2, cm21): 2108 (w), 2068 (s), 2040 (s), 1579 (w),
1542 (w), 1383 (m). UV–Vis (CH2Cl2, nm, M21cm21):
520 (´ 5,500), 350 sh. Magnetic susceptibility (Evans
method, CD2Cl2, 208) c57.0831023 cm23mol21. EPR
(powder, 4 K) g: 2.04, Dp–p: 116 G, and a sharp signal at
g: 2.13, Dp–p: 2300 G. Analysis: Found C 29.86%, H
1
556 (m), 530 (m), 528 (m), 499 (m), 473 (w). H NMR
(CD2Cl2, d, 208): 8.3 br m, 6.5 br s, 3.4 br s, 2.6 br s, 1.2
br s. UV–Vis (CH2Cl2, nm, M21cm21): 300 (´ 13,300),
524 (´ 2,300). XPS confirms the existence of Zn (2p3 / 2
,
,
1021 and 2p1 / 2, 1044 eV) and Co (2p3 / 2, 780 and 2p1 / 2
795 eV) in the ratio of ¯1:9. Analysis (dried under
vacuum). Found, Co 41.47%, Zn 4.21% (10.98 Co/Zn mol
ratio). Calculated for C37Co11ZnO37: Co 37.04%, Zn
3.74% (11.0 Co/Zn mol ratio).
0.83%, N 1.11%. Calculated for C69H19Co17N2O55
30.05%, H 0.69%, N 1.02%.
C
2.1.5. CoCr2(m3-O)hm-OOCCCo3(CO)9 j4(m-OOCCH3 )2
h(CO)9Co3CCOOHj2(H2O)?C7H8 , 5a
2.2. Structure determinations
0.443 g (1.18 mmol) of Cr2(OOCCH3)4(H2O)2, syn-
thesized by published methods [24], were dispersed with
sonication in 30 ml of CH2Cl2 in a two-neck Schlenk flask
and mixed with 2.983 g (6.14 mmol) of (CO)9Co3C-
COOH dissolved in 20 ml CH2Cl2 under Ar. The solution
was sonicated three times for 5 min and allowed to react at
358C for 24 h. The solvent was removed under vacuum at
room temperature and the residue extracted with two 25 ml
portions of toluene, and filtered cold. The yield of crys-
talline product was 40% (730 mg 0.22 mmol) based on Cr.
IR (KBr pellet, cm21) 2962 (w), 2929 (w), 2109 (w), 2056
(s), 2045 (s), 2038 (s), 1694 (w), 1636 (w), 1600 (w), 1560
(w), 1379 (m), 1330 (m), 1263 (w), 1084 (w), 757 (w), 730
(w), 722 (w), 556 (w), 529 (w), 501 (m), 418 (w). UV–Vis
(CH2Cl2, nm, M21cm21) 512 (´ 9,030), 380(sh), 302 (´
75,000). EPR(crystals, X-band) silent at room temperature.
Analysis: Found: C 28.72%, H 0.77%, Co 32.08%. Calcu-
lated for C77H18Co19Cr2O72: C 27.87%, H 0.55%, Co
33.74%. MS (negFAB, Xe, NBA CH2Cl2) Found: m/z
1997.0 (22%), 2133.8 m/z (15%), 2156.5 m/z (25%).
Calculated: m/z 1997.0 Co(C11Co3O11)4, m/z 2133.8
C48H562Cr2Co12O48 -CO, m/z 2156.5 C48H652Cr2Co12O48
-4H.
2.2.1. Cr2 hm-OOC-CCo3(CO)9 j2 hm-OOCCF3 j2(THF)2 , 1
Crystals of 1 suitable for X-ray diffraction were grown
from a saturated solution of 1 in toluene kept at 108C for a
month. Crystal data and experimental details are given in
Table 1. A block-like black crystal with dimensions 0.583
0.3230.22 mm was mounted in a glass capillary in a
random orientation and data were collected with an Enraf–
Nonius CAD4 diffractometer equipped with a graphite
crystal monochromated Mo Ka X-radiation source. The
structure was solved by the MULTAN direct methods
followed by successive different Fourier syntheses. Full-
matrix least-squares refinements were employed. All-non-
hydrogen atoms were refined with anisotropic thermal
parameters in the final cycles. R50.04085, Rw 50.05394,
(370 variables refined) for 2642 reflections with F2o.
3s(F2o).
2.2.2. Sm2 hm-OOCCCo3(CO)9 j2 hm-OOCCF3 j4
h(CO)9Co3CCOOHj2(THF)2?2THF, 2
A black plate-like crystal was mounted on a glass fiber
with its long axis roughly parallel to the Phi axis of the
goniometer. Data were collected with an Enraf–Nonius
CAD4 diffractometer equipped with a graphite crystal
monochromated Mo Ka X-radiation source. Crystal data
and experimental details are given in Table 1. The
structure was solved by direct methods. A total of seven
metal atoms were located from an E-map and the remain-
ing were located in succeeding difference Fourier synth-
eses. Hydrogen atoms were not included in the calcula-
tions. The structure was refined in full-matrix least-
squares. All-non-hydrogen atoms were refined with aniso-
tropic thermal parameters in the final cycles. R150.04531,
2.1.6. Cr3(m3-O)hm-OOCCCo3(CO)9 j4(m-OOCCH3 )2
h(CO)9Co3CCOOHj(CH3OOH)2?C7H8 , 5b
The same reaction mixture as for 5a gave a small yield
(50 mg, 0.02 mmol) of a second compound. IR (KBr
pellet, cm21) 2963 (w), 2932 (w), 2111 (w), 2043 (s), 1645
(w), 1562 (w-br), 1430 (w), 1386 (w), 1252 (w), 1080 (w),
760 (w), 722 (m), 697 (w), 554 (m), 527 (m), 500(s), 418
(w). EPR (X-band) powder, g: 2.01, Dp–p: 500 G, single
crystal, g: 1.98, Dp–p: 520 G.

Table 1
Crystal data for compounds 1–6
1
2
3
4
5a
5b
6
Formula
C34H16Co6Cr2F6O28
C68H34Co12Sm2F12O56
2982.87
C46H4Co13PtO46
2253.74
C45Co11ZnO38
1862.0
C77H18Co19Cr2O72
3318.68
C70H23Co15Cr3O64
2927.91
C69H19Co17N2O55
2757.67
F.W.
1444.07
F(000)
1416
1446
4308
3234
5728
10768
Crystal dimensions
0.5830.3230.22 mm
0.1330.1830.48 mm
0.5530.2830.12 mm
0.4230.4430.56 mm
0.1830.0930.14 mm
0.5530.3630.35 mm
0.4030.4030.40 mm
˚
˚
˚
˚
˚
˚
˚
Mo Ka radiation
l50.71073 A
l50.71073 A
l50.71073 A
l50.71073 A
l50.71073 A
l50.71073 A
l50.71073 A
Temperature
208C
208C
208C
208C
208C
208C
2278C
Space group
P21 /n
Pi
P21 /c
P21 /n
Pi (No. 2)
P21 /n (No. 14)
P21 /c
˚
˚
˚
˚
˚
a
10.662(1)A
13.6311(9) A
21.759(4) A
12.222(5)
22.584 (6)
24.052 (6)
14.500 (3) A
17.770 (5) A
26.069(7) A
˚
˚
˚
˚
˚
˚
24.439 (5) A
b
12.430(3) A
13.952(2) A
17.979(3) A
20.291 (4) A
21.367 (2) A
.
˚
˚
˚
˚
˚
˚
c
19.415(3) A
16.691(2) A
20.053(5) A
20.817 (3) A
28.075 (7) A
30.236 (13) A
a
104.23(1)8
101.096(7)8
115.638(9)8
71.60 (1)8
80.90 (1)8
b
94.76(1)8
114.91(2)8
92.35
102.69 (1)8
90.70 (3)8
g
80.26 (2)8
3
3
3
3
3
3
˚
˚
˚
˚
˚
˚
V
2564.1(8) A
2606.7(6) A
7115(3) A
6633 (20)
5692 (2) A
10400 (4) A
19261 (11) A
Z
2
1
4
4
2
4
8
Cal. density
1.870 g/cm3
1.900 g/cm3
2.104 g/cm3
1.865 g/cm3
29.637 cm21
9398 total, 9081 unique
1.936 g/cm3
1.870 g/cm3
1.902 g/cm3
m(Mo Ka)
23.916 cm21
30.751 cm21
50.180 cm21
29.637 cm21
27.117 cm21
29.41 cm21
No. of reflections measured
Corrections
4260 total, 3434 unique
Lorentz-polarization
Linear decay (from 0.999 to
1.294 on I)
7573 total, 7216 unique
Lorentz-polarization
Linear decay (from 0.985 to
1.131 on I)
10447 total, 8781 unique
Lorentz-polarization
Linear decay (from 0.981 to
1.306 on I)
10556 total, 10556 unique
Lorentz-polarization
Linear decay (from 0.998 to
1.183 on I)
14948 total, 11088 unique
Lorentz-polarization
Linear decay (from 1.000 to
1.157 on I)
21148 total, 20645 unique
1
Reflection averaging
(agreement on I51.6%)
Empirical absorption
(0.8250–0.9977 on I)
Direct methods
Reflection averaging (agreement
on I52.5%)
Reflection averaging (agreement
on I53.1%)
Empirical absorption (from 0.89
to 1.00 on I)
Reflection averaging (agreement
on I52.2%)
9
Empirical absorption (0.6516–
0.9998 on I)
Empirical absorption (0.5978–
0.9990 on I)
Empirical absorption (from
0.9269 to 0.9998 on I)
Direct methods
1
Solution
Direct methods
Direct methods
Direct methods
Direct methods
Direct methods
1
hydrogen atoms
Not included
Not included
Not included
Not included
Not included
Not located
Idealized
Refinement
Full-matrix least-squares
ow(uFou2uFcu)2
Full-matrix least-squares
ow(uFou2uFcu)2
Full-matrix least-squares
ow(uFou2uFcu)2
Full-matrix least-squares
ow(uFou2uFcu)2
Full-matrix least-squares
ow(uFou2uFcu)2
Full-matrix least-squares
ow(uFou2uFcu)2
Full-matrix least-squares
ow(uFou2uFcu)2
Minimization function
Least-squares weights
Anomalous dispersion
Reflections included
Parameters refined
4F20 /s2(F20)51/s2(F0)
All non-hydrogen atoms
4F20 /s2(F20)51/s2(F0)
All non-hydrogen atoms
4F20 /s 2(F 20)51/s 2(F0)
All non-hydrogen atoms
4F02 /s 2(F02)51/s 2(F0)
All non-hydrogen atoms
3910 with F02.3.0s(F02
4F02 /s 2(F02)51/s 2(F0)
All non-hydrogen atoms
4F02 /s 2(F02)51/s 2(F0)
All non-hydrogen atoms
4F02 /s 2(F02)51/s 2(F0)
All non-hydrogen atoms
2642 with F20.3.0s(F02
)
5781 with F20.3.0s(F02
)
7226 with F20.3.0s(F02
)
)
6422 with F20.3.0s(F02
)
6507 with F20.3.0s(F02
)
20638 with F20.4.0s(F02
)
370
663
955
787
930
1315
Unweighted agreement factor
Weighted agreement factor
Esd of obs. of unit weight
Convergence, largest shift
High peak in final diff, map
Low peak in final diff, map
0.04085
0.05 394
1.824
0.04531
0.06065
2.077
0.03683
0.04770
1.536
0.0705
0.0737
0.070
0.085
2.26
0.08231
0.1074
2.240
0.1260
0.2783
0.02
0.03
0.01
0.26
0.03
3
3
3
3
3
3
3
˚
˚
˚
˚
˚
˚
˚
4.178 e/A
0.70(7) e/A
0.92 (11) e/A
1.56(10) e/A
0.97 e/A
2.38(13) e/A
1.13(13) e/A
3
3
3
3
3
3
˚
˚
˚
˚
˚
˚
20.32(7) e/A
20.86(11) e/A
20.64(10) e/A
20.85(13) e/A
20.85(13) e/A
21.863 e/A
R15ouF02Fcu/ouF0u, R25(ow(F02Fc)2 /owF02)1 / 2
.

V. Calvo-Perez et al. / Polyhedron 18 (1999) 1869–1880
1873
Table 2
Selected bond distances and angles for 1
˚
Bond
Distance [A]
Angle
Angle [8]
Cr
Cr
Cr
Cr
Cr
Cr
Co(1)
Co(1)
Co(1)
Co(1)
Co(1)
Co(1)
Co(2)
Cr
2.427(1)
1.993(4)
2.002(4)
2.028(4)
2.021(4)
2.234(4)
2.456(1)
2.449(1)
1.884(5)
1.780(6)
1.825(8)
1.748(8)
2.458(1)
Cr
Cr
Cr
O(2)
O(3)
O(4)
C(1)
C(1)
C(1)
Cr
Cr
Cr
Cr
Cr
C(1)
C(3)
C(3)
0(2)
121.4(3)
117.7(3)
118.5(3)
123.6(5)
118.1(4)
118.3(4)
174.2(1)
90.9(1)
88.6(1)
94.2(1)
89.2(1)
90.8(1)
91.6(1)
174.8(1)
92.0(1)
93.2(1)
O(1)
O(2)
O(3)
O(4)
O(5)
Co(2)
Co(3)
C(2)
C(11)
C(12)
C(13)
Co(3)
O(1)
O(1)
O(2)
O(1)
O(1)
O(1)
O(1)
O(2)
O(2)
O(2)
O(3)
O(3)
0O4)
C(2)
C(2)
0O(2)
O(3)
O(4)
O(5)
O(3)
O(4)
O(5)
O(4)
O(5)
O(5)
Cr
Cr
Cr
Cr
Cr
Fig. 2. Molecular structure of Sm2hm-OOCCCo3(CO)9j2hm-
OOCCF3j4h(CO)9Co3CCOOHj2(THF)2?2THF, 2.
R250.06065, (663 variables refined) for 5781 reflections
with F2o.3s(F2o).
with an Enraf–Nonius CAD4 diffractometer equipped with
a graphite crystal monochromated Mo Ka X-radiation
source. Crystal data and experimental details are given in
Table 1. The structure was solved by direct methods
followed by successive different Fourier syntheses. Full-
matrix least-squares refinements were employed. All-non-
hydrogen atoms were refined with anisotropic thermal
parameters in the final cycles. R150.03683, R250.04770,
(955 variables refined) for 7226 reflections with F2o.
3s(F2o).
2.2.3. PtCohm-OOCCCo3(CO)9 j3(m-OOCCH3 )
h(CO)9Co3CCOOHj, 3
A black plate-like crystal was mounted in a glass
capillary in a random orientation and data were collected
2.2.4. ZnCohm-OOCCCo3(CO)9 j3 hCo(CO)4 j
h2-(CH3 )C4H7Oj, 4
A suitable crystal of 3 was mounted in a thin wall
capillary under nitrogen. Crystal data and experimental
details are given in Table 1. The unit cell parameters were
obtained by the least-squares refinement of the angular
settings of 24 reflections (208#2u#248). Approximately
10% of the data was rejected by the learnt-profile routine
Table 3
Selected bond distances and angles for 2
˚
Bond
Distance [A]
Angle
Angle [8]
Sm
Sm
Sm
Sm
Sm
Sm
Sm
Sm
O(1)
O(3)
O(4)
O(5)
O(6)
O(7)
O(8)
O(9)
2.475(5)
2.483(5)
2.420(5)
2.410(6)
2.39(5)
2.379(4)
2.462(5)
2.467(5)
O(1)
O(1)
O(1)
O(1)
O(1)
O(1)
O(1)
O(3)
O(3)
O(6)
O(6)
O(6)
O(7)
O(7)
O(8)
O(5)
Sm
Sm
Sm
Sm
Sm
Sm
Sm
Sm
Sm
Sm
Sm
Sm
Sm
Sm
Sm
Sm
O(3)
O(4)
O(5)
O(6)
O(7)
O(8)
O(9)
O(4)
O(5)
O(7)
O(8)
O(9)
O(8)
O(9)
O(9)
O(9)
71.8(1)
97.1(2)
144.8(1)
73.3(2)
141.5(2)
74.1(2)
74.4(2)
53.0(2)
134.3(1)
75.1(2)
79.9(2)
143.9(2)
120.8(2)
140.8(2)
76.0(2)
73.8(2)
Fig. 1. Molecular structure of Cr2hm-OOC-CCo3(CO)9j2hm-
OOCCF3j2(THF)2, 1.

1874
V. Calvo-Perez et al. / Polyhedron 18 (1999) 1869–1880
Table 4
Selected bond distances and angles for 3
˚
Bond
Distance [A]
Angle
O(1) Pt
O(1) Pt
O(1) Pt
O(2) Pt
O(2) Pt
O(3) Pt
O(5) Co(1)
O(5) Co(1)
O(5) Co(1)
O(5) Co(1)
O(6) Co(1)
O(6) Co(1)
O(6) Co(1)
O(7) Co(1)
O(7) Co(1)
O(8) Co(1)
Angle [8]
Pt
Pt
Pt
Pt
Pt
Co(1) 2.506(1)
O(2)
O(3)
90.0(2)
91.9(2)
O(4) 177.9(2)
O(3) 178.1(2)
O(1)
O(2)
O(3)
O(4)
1.995(5)
2.006(4)
2.018(4)
1.996(6)
2.071(5)
2.036(4)
2.138(4)
2.049(6)
2.013(5)
O(4)
O(4)
O(6)
O(7)
88.6(2)
89.6(2)
89.9(2)
85.7(2)
Co(1) O(5)
Co(1) O(6)
Co(1) O(7)
Co(1) O(8)
Co(1) O(9)
O(8) 165.8(2)
O(9) 95.3(2)
O(7) 164.9(2)
O(8) 91.8(2)
O(9) 100.5(2)
O(8)
O(9)
O(9)
89.1(2)
94.3(2)
98.3(2)
2.2.6. Cr3(m3-O)hm-OOCCCo3(CO)9 j4(m-OOCCH3 )2
h(CO)9Co3CCOOHj(CH3OOH)2?C7H8 , 5b
Fig. 3. Molecular structure of PtCohm-OOCCCo3(CO)9j3(m-OOCCH3)
h(CO)9Co3CCOOHj, 3.
Crystals of 5b suitable for X-ray diffraction were grown
from a hot saturated extract of 5b in toluene left at room
temperature for one day and cooled to 108C for a week. A
black crystal was mounted on a glass capillary with its
long axis parallel to the phi axis of the goniometer and
data were collected with an Enraf–Nonius CAD4 diffrac-
tometer equipped with a graphite crystal monochromator
and Mo Ka X-radiation source. Crystal data and ex-
perimental details are given in Table 1. The structure was
solved by the direct methods finding the 18 metal atoms,
the remaining atoms were found in succeeding difference
Fourier synthesis. Full-matrix least-squares refinements
were employed. All-non-hydrogen atoms were refined with
anisotropic thermal parameters in the final cycles. Two
tricobaltcarbonyl clusters were disordered in two sets of
as contributions from a minor twin or satellite crystal. The
unit cell of this compound contains four dimers, where two
are structurally different clusters. The structure was solved
by direct methods and completed by subsequent difference
Fourier synthesis and refined by full-matrix least-squares
procedures. Carbon atoms were refined isotropically. A
Me-THF molecule coordinated to the Zn appears to be
thermally disordered. A benzene molecule was found near
an inversion center with an occupancy of 50% and was
refined as a rigid body. Hydrogen atoms were ignored. The
3
˚
remaining peak in the difference map (0.97 e/A ) occurs
at a chemically unreasonable position and was considered
as noise.
2.2.5. CoCr2(m3-O)hm-OOCCCo3(CO)9 j4(m-OOCCH3 )2
h(CO)9Co3CCOOHj2(2H2O).C7H8 , 5a
Crystals of 5a suitable for X-ray diffraction were grown
from a warm toluene extract of 5a left at room temperature
for a week. A black plate-like crystal was mounted on a
glass fiber with its long axis parallel to the phi axis of the
goniometer. Data were collected with an Enraf–Nonius
CAD4 diffractometer equipped with a graphite crystal
monochromatic and Mo Ka X-radiation source. Crystal
data and experimental details are given in Table 1. The
structure was solved by direct methods where we found 21
metal atoms and followed by successive different Fourier
syntheses. Full-matrix least-squares refinements were em-
ployed. All-non-hydrogen atoms were refined with aniso-
tropic thermal parameters in the final cycles. Two toluene
molecules were found in two different sets of inversion
centers. R50.070, Rw50.085, (787 variables refined) for
6422 reflections with F2o.3s(Fo2).
Fig. 4. Molecular structure ofZnCohm-OOCCCo3(CO)9j3hCo(CO)4jh2-
(CH3)C4H7Oj, 4.

V. Calvo-Perez et al. / Polyhedron 18 (1999) 1869–1880
1875
Table 5
Table 6
Selected bond distances and angles for 4
Selected distances and angles for 5a and 5b
˚
˚
˚
Bond
Distance [A]
Angle
Angle [A]
Bond Distance [A]
Angle
Angle [8]
Co(1)–Co(11)
Zn–O(32)
Zn–O(35)
2.419(4)
1.917(13)
1.921(12)
5a
Co(1) O(1)
Co(1) O(2)
Co(1) O(3)
Co(1) O(4)
Co(1) O(5)
Co(1) O(6)
Cr(1) O(1)
Cr(1) O(7)
Cr(1) O(8)
Cr(1) O(9)
Cr(1) O(10) 1.957(9)
Cr(1) O(11) 2.10(1)
Cr(2) O(1)
Cr(2) O(12) 1.956(9)
Cr(2) O(13) 2.01(1)
Cr(2) O(14) 1.96(1)
Cr(2) O(15) 1.987(9)
Cr(2) O(16) 2.09(1)
1.936(9)
2.12(1)
2.12(1)
2.11(1)
2.12(1)
2.13(1)
1.85(1)
2.020(9)
1.96(1)
1.99(1)
O(1)
O(2)
O(2)
O(2)
O(2)
O(3)
O(3)
O(3)
O(4)
O(4)
O(5)
O(1)
O(1)
O(1)
O(1)
O(1)
O(7)
O(7)
O(7)
O(7)
O(8)
O(8)
Co(1) O(6)
Co(1) O(3)
Co(1) O(4)
Co(1) O(5)
Co(1) O(6)
Co(1) O(4)
Co(1) O(5)
Co(1) O(6)
Co(1) O(5)
Co(1) O(6)
Co(1) O(6)
Cr(1) O(7)
Cr(1) O(8)
Cr(1) O(9)
Cr(1) O(10)
179.4(4)
85.8(4)
92.2(4)
166.9(4)
84.2(4)
171.1(4)
91.9(4)
86.0(4)
88.1(4)
85.2(4)
82.8(4)
95.9(4)
96.7(5)
94.9(5)
94.3(4)
Zn–O(32)–C(32)
O(32)–Zn–O(35)
Zn–O(35)–C(34)
O(32)–Zn–O(36)
Zn–O(36)–C(36)
O(32)–Zn–O(38)
Co(1 1)–Co(1)–C(1)
Co(1 1)–Co(1)–C(3)
Co(11)–Co(1)–C(3)
Co(11)–Co(1)–C(4)
Co(1)–Co(11)–O(33) 119.4(4)
Co(11)–O(33)–C(32) 143.2(13)
Co(1)–Co(11)–O(34) 113.3(4)
Co(11)–O(34)–C(34) 139.4(13)
Co(1)–Co(11)–O(37) 108.2(4)
Co(11)–O(37)–C(36) 144.8(13)
126.7(12)
112.2(5)
130.2(5)
112.5(12)
122.8(12)
102.5(5)
75.6(7)
88.7(8)
167.6(7)
73.2(9)
Zn–O(36)
1.923(11)
Zn–O(38)
1.982(13)
1.792(23)
1.722(27)
1.790(23)
1.754(25)
Co(1)–C(1)
Co(1)–C(2)
Co(1)–C(3)
Co(1)–C(4)
Co(11)–O(33) 1.969(14)
Co(11)–O(34) 1.943(13)
Co(11)–O(37) 1.969(13)
1.87(1)
Cr(1) O(11) 175.6(5)
Cr(1) O(8)
Cr(1) O(9)
89.9(4)
85.6(4)
Co(8)–Co(9)
Co(8)–Co(10)
Co(9)–Co(10)
2.455(4)
2.4.64(4)
2.466(4)
Co(8)–Co(9)–Co(10)
Co(9)–Co(8)–Co(10)
60.1(1)
60.2(1)
Cr(1) O(10) 169.7(4)
Cr(1) O(11)
Cr(1) O(9)
Cr(1) O(10)
86.9(4)
167.9(5)
90.1(4)
positions with occupancies of 0.73 and 0.27, the rotational
disorder about the C(3)–C(4) bond was successfully
modeled. A toluene molecule was found with the methyl
group disordered. The hydrogen atoms were not found but
three H-bonded carboxylic acid show up in the terminal
position of the chromium centers. R50.0823, Rw50.1074,
(930 variables refined) for 6507 reflections with F2o.
3.0s(F2o).
5b
Cr(1) O(1)
Cr(1) O(2)
Cr(1) O(3)
Cr(1) O(4)
Cr(1) O(5)
Cr(1) O(6)
Cr(2) O(1)
Cr(2) O(7)
Cr(2) O(8)
Cr(2) O(9)
1.868(9)
2.10(1)
1.968(9)
1.99(1)
1.98(1)
2.021(9)
1.856(9)
2.10(1)
1.971(8)
2.01(1)
O(1)
O(1)
O(1)
O(1)
O(1)
O(2)
O(2)
O(2)
O(2)
O(3)
O(3)
O(3)
O(4)
O(4)
O(5)
O(1)
O(1)
O(1)
O(1)
O(1)
O(7)
O(7)
O(7)
O(7)
O(8)
O(8)
O(8)
O(9)
O(9)
Cr(1) O(2)
Cr(1) O(3)
Cr(1) O(4)
Cr(1) O(5)
Cr(1) O(6)
Cr(1) O(3)
Cr(1) O(4)
Cr(1) O(5)
Cr(1) O(6)
Cr(1) O(4)
Cr(1) O(5)
Cr(1) O(6)
Cr(1) O(5)
Cr(1) O(6)
Cr(1) O(6)
Cr(2) O(7)
Cr(2) O(8)
Cr(2) O(9)
Cr(2) O(10)
Cr(2) O(11)
Cr(2) O(8)
Cr(2) O(9)
Cr(2) O(10)
Cr(2) O(11)
Cr(2) O(9)
Cr(2) O(10)
178.4(4)
96.8(4)
94.0(4)
96.6(4)
95.5(4)
81.8(4)
85.4(4)
84.0(4)
85.9(4)
91.7(4)
89.9(4)
167.7(4)
169.0(4)
86.6(4)
89.5(4)
177.6(4)
95.6(4)
93.4(4)
96.8(4)
95.5(4)
83.2(4)
84.6(4)
85.3(4)
85.6(4)
92.0(4)
90.4(4)
2.2.7. [C10H6(N(CH3 )2 )2H][Co2 hm-OOCCCo3(CO)9 j3
hOOCCCo3(CO)9 j2 ], 6
A crystal of 6 was mounted inside a thin wall capillary
Cr(2) O(10) 1.95(1)
Cr(2) O(11) 2.008(9)
Cr(3) O(1)
1.940(9)
Cr(3) O(12) 2.16(1)
Cr(3) O(13) 2.07(1)
Cr(3) O(14) 2.06(1)
Cr(3) O(15) 2.05(1)
Cr(3) O(16) 2.05(1)
C(1)
C(1)
C(1)
C(3)
C(3)
O(3)
O(8)
C(2)
O(4)
O(9)
1.28(2)
1.23(2)
1.47(2)
1.24(2)
1.24(2)
Cr(2) O(11) 168.7(4)
Cr(2) O(10) 169.3(4)
Cr(2) O(11)
O(10) Cr(2) O(11)
85.4(4)
90.3(4)
O(1)
O(1)
O(1)
O(1)
O(1)
Cr(3) O(12) 175.9(4)
Cr(3) O(13)
Cr(3) O(14)
Cr(3) O(15)
Cr(3) O(16)
97.7(4)
94.5(4)
93.7(4)
95.7(4)
85.5(4)
83.0(4)
88.8(4)
81.0(4)
O(12) Cr(3) O(13)
O(12) Cr(3) O(14)
O(12) Cr(3) O(15)
O(12) Cr(3) O(16)
Fig. 5. Molecular structure of CoCr2(m3-O)hm-OOCCCo3(CO)9j4(m-
OOCCH3)2h(CO)9Co3CCOOHj2(H2O)?C7H8, 5a. The CO ligands have
been removed from the tricobalt clusters for clarity.

1876
V. Calvo-Perez et al. / Polyhedron 18 (1999) 1869–1880
asymmetric unit. The remaining peak in the difference map
3
˚
(4.18 e/A ) occurs at a chemically unreasonable positions
and were considered artifacts arising from less than
satisfactory absorption coefficients. All crystals of 6 that
were examined diffracted weakly and broadly indicating a
large mosaic spread.
3. Results and discussion
Descriptions of the structures of the various cluster
coordination compounds are presented below and salient
features discussed proceeding from low to high cluster
coordination number. In all cases, the structure of the
tricobalt cluster in the ligand remains invariant within
experimental error. Hence, the emphasis is on cluster
coordination number, geometry, and core properties. Here
the terms cluster coordination number and geometry refer
only to the coordinated cluster ligands [(CO)9Co3(m3-
COO)]2, i.e. our interest lies primarily in the spatial array
of the tricobalt clusters rather than the complete coordina-
tion properties of the cationic metal cores which serve to
support these arrays. Some compounds contain weakly
coordinating cluster acid and this is ignored in defining the
geometry of the cluster array. The coordinated cluster acid
is known to be easily lost in solution [12]. Most likely it is
found in the crystalline materials used for structural
characterization as it fills some of the large voids that
would exist in its absence, i.e., the tricobalt cluster
substituent has substantial steric bulk.
Fig. 6. Molecular structure of Cr3(m3-O)hm-OOCCCo3(CO)9j4(m-
OOCCH3)2h(CO)9Co3CCOOHj(CH3OOH)2?C7H8, 5b. The CO ligands
have been removed from the tricobalt clusters for clarity.
under nitrogen. Crystal data and experimental details are
given in Table 1. The unit cell parameters were obtained
by the least-squares refinement of the angular settings of
24 reflections (208#2u#258). Systematic absences are
uniquely consistent with space group P21 /c. The structure
was solved by direct methods and completed by sub-
sequent difference Fourier synthesis and refined by full-
matrix least-squares procedures. There are two indepen-
dent but chemically equivalent cluster anions in the
Several of the new compounds contain Co(II) and one a
Co(CO)4 fragment. As discussed previously [5,14,21],
these species arise from the degradation of the tricobalt
cluster during reaction. The likelihood of finding them in
the products increases with increasing reaction time.
Despite the curious source of the Co(II), yields of isolated
products are good in most cases.
Table 7
Selected bond distances and angles for 6
˚
Bond
Distance [A]
Angle
Angle [8]
Co(1)–O(1)
1.97(3)
1.93(3)
1.94(3)
Co(1)–O(1)–C(1)
O(7)–Co(1)–O(1)
Co(1)–O(3)–C(3)
O(7)–Co(1)–O(3)
Co(1)–O(5)–C(5)
O(7)–Co(1)–O(5)
Co(1)–O(7)–C(7)
O(9)–Co(2)–O(2)
Co(2)–O(2)–C(1)
O(9)–Co(2)–O|4)
Co(2)–O(4)–C(3)
O(9)–Co(2)–O(6)
Co(2)–O(6)–C(5)
Co(2)–O(9)–C(9)
130(3)
113.4(13)
130(3)
109.8(13)
143(3)
98.9(14)
109(3)
116.3(12)
141(3)
109.5(12)
142(3)
101.5(12)
126(3)
103(3)
Co(1)–O(3)
Co(1)–O(5)
Co(1)–O(7)
Co(2)–O(2)
1.93(3)
1.97(3)
Co(2)–O|4)
1.96(3)
1.99(3)
Co(2)–O(6)
Co(2)–O(9)
Co(3)–Co(4)
Co(3)–Co(5)
Co(4)–Co(5)
1.97(3)
2.44(2)
2.456(13)
2.439(12)
Fig. 7. Molecular structure of [C10H6(N(CH3)2)2H][Co2hm-OOC-
CCo3(CO)9j3hOOCCCo3(CO)9j2], 6. The CO ligands have been removed
from the tricobalt clusters for clarity.
Co(3)–Co(4)–Co(5)
Co(4)–Co(5)–Co(3)
60.5(4)
59.7(5)

V. Calvo-Perez et al. / Polyhedron 18 (1999) 1869–1880
1877
Fig. 8. Schematic drawings of the relative geometries of the metal coordinated cluster ligands for structurally characterized cluster coordination compounds
where G5–CCo3(CO)9: (a) 1, (b) 2, (c) 3, (d) 4, (e) 5a, (f) 6.
3.1. Cluster coordination number52
electron withdrawing as the [CF3COO] group but more so
than the [CH3COO] group consistent with our earlier
conclusions [5]. Note that the Cr–O distances for the
[CF3COO] ligand are significantly longer than those for
the cluster carboxylate ligand, e.g., Cr(1)–O(3)52.028(4)
3.1.1. Cr2 hm-OOC-CCo3(CO)9 j2 hm-OOCCF3 j2(THF)2 , 1
The structure of 1 is shown in Fig. 1 (Table 2) and
exhibits trans cluster carboxylate ligands leading to a linear
array of tricobalt clusters (Fig. 8a). The axial positions are
coordinated by two THF molecules which is typical of
related compounds [10]. The Cr–Cr distance 2.427(1) A is
typical of a Cr–Cr quadruple bond and midway between
that of Cr2(m-OOCCF3)4(THF)2 (2.541 A) [25] and that
of Cr2(m-OOCCH3)4(CH3CCOOH)2 (2.300 A) [26]. This
˚
˚
A, Cr(1)–O(1)51.993(4) A.
˚
3.1.2. Sm2 hm-OOCCCo3(CO)9 j2 hm-OOCCF3 j4
h(CO)9Co3CCOOHj2(THF)2?2THF, 2
The structure of 2, which is shown in Fig. 2 (Table 3)
˚
˚
and Fig. 8b, exhibits a dimeric Sm(III) core (Sm–Sm5
2
˚
suggests that the [(CO)9Co3(m3-CCOO)] group is not as
4.239 A) asymmetrically bridged by four [CF3COO]

1878
V. Calvo-Perez et al. / Polyhedron 18 (1999) 1869–1880
ligands. Two [CF3COO]2 ligands apparently chelate one
Sm(III) each and are positioned such that one oxygen atom
each also bridges the two Sm atoms. Additionally, each
Sm(III) center is chelated by one [(CO)9Co3CCOO]2
ligand plus coordinated to one THF molecule and one
(CO)9Co3CCOOH cluster acid which also forms a hydro-
gen bond to an oxygen atom of the chelating cluster ligand.
Thus, the core is closely related to that found in the
[Sm2hOOCCH3j3hH2Oj2]2 dimer, i.e. CF3COO2 is re-
placed by acetate, the cluster ligand by acetate and the
THF and the cluster acid by two H2O molecules [27]. As
far as the coordinated cluster ligands are concerned, they
form a linear array in the same manner as compound 1 but
with a substantially larger distance separating them.
THF can be observed for 4 in CD2Cl2 with somewhat
larger than normal chemical shifts. The IR spectrum
distinctly shows the signature [28] of bridging carboxylates
consistent with the solid state structure. In addition, the
bands observed at 1984–1944 cm21, not present in the
other compounds, are assigned to the Co(CO)4 moiety.
The band position suggests considerably more negative
charge than present on the Co(CO)3 groups of the ligand
clusters which is consistent with a polar (donor–acceptor)
Co(1) – Co(11) metal–metal bond. Thus, we view Co(11)
as a Co(II) center.
3.3. Cluster coordination number54
3.3.1. CoCr2(m3-O)hm-OOCCCo3(CO)9 j4(m-OOCCH3 )2
h(CO)9Co3CCOOHj2(H2O)?C7H8 , 5a; Cr3(m3-O)
hm-OOCCCo3(CO)9 j4(m-OOCCH3 )2 h(CO)9Co3CCOOHj
(CH3OOH)2?C7H8 , 5b
3.2. Cluster coordination number53
3.2.1. PtCohm-OOCCCo3(CO)9 j3(m-OOCCH3 )
h(CO)9Co3CCOOHj, 3
Compounds 5 are related to the known organic car-
boxylates of the type Cr3(m3-O)(m-OOCR)7(L)3 [29], e.g.
Cr3(m3-O)hm-OOCRj6(py)3, a mixed valence trimer with
one Cr(II) and two Cr(III) centers [30], which have been
extensively studied [31,32]. Because of the kinetic inert-
ness of the Cr(III) centers, a simple cluster carboxylate
exchange strategy does not lead to the cluster analogs.
However, partially ‘‘exchanged’’ analogs were obtained
from the dimeric Cr(II) cluster carboxylate; namely both
mixed metal 5a and homonuclear 5b complexes. Mixed
The structure of 3, shown in Fig. 3 (Table 4) and Fig.
8c, exhibits a Co(II)Pt(II) core bridged by three cluster
carboxylates and one acetate. The P(II) center is in a
square planar environment of oxygen atoms; however, the
Pt–Co distance is well within the sum of the metal
˚
covalent radii (Pt–Co(1)52.506(1) A). The Co(II) center
is axially coordinated by the oxygen of a cluster acid the
presence of which is corroborated by the IR spectrum in
that a band at 1642 cm21 characteristic of the acid is
observed [28]. As is common with coordinated cluster
acids, the OH group is also hydrogen bonded to one of the
oxygen atoms of a bridging cluster ligand. Thus, the Co(II)
center may be considered either five or six coordinate
depending how the Pt atom is viewed. The three coordi-
nated tricobalt clusters form a T-shaped or isosceles
triangular array.
metal
species
such
as
Cr2Co(m3-O)hm-OOC-
CMe3j6(H2O)3 [33] have also been studied previously
[34].
The structure of 5a is shown in Figs. 5 and 8e (Table 6)
and the core structure is similar to that of a Cr2Co(m3-
O)(m-OOCR)6 complex described earlier [33]. Both
Cr(III) and Co(II) centers are octahedral. The existence of
cluster acid connected to each to the Cr centers is evident
from the IR band at 1695 cm21 which is typical of a
carboxylic acid. The structure of the cluster 5b is shown in
Fig. 6. Oxo-trimers of Cr3(III, III, III) have been reported
much more frequently [29] than Cr3(II, III, III) compounds
[30]. The EPR signal observed for 5b is consistent with
that exhibited by Cr3(m3-O)(m-OOCCH3)7 [35]. Thus, the
fact that 5a is EPR silent is ascribed to the presence of the
octahedral Co(II) d7 metal ion.
3.2.2. ZnCohm-OOCCCo3(CO)9 j3 hCo(CO)4 j
h2-(CH3 )C4H7Oj, 4
The structure of cluster 4, shown in Figs. 4 and 8d,
consists of a Zn(II)Co(II) nonbonded dimer bridged by
three cluster carboxylates. Consequently, the three cluster
ligands display a trigonal arrangement. The two metal
cations have tetrahedral environments: the fourth position
being occupied with methyl THF in the case of Zn and a
[Co(CO)4]2 fragment in the case of Co. The methyl group
of the THF ligand is oriented towards the center of the
cluster and lies between two of the cluster ligands.
3.4. Cluster coordination number55
3.4.1. [C10H6(N(CH3 )2 )2H][Co2 hm-OOCCCo3(CO)9 j3
hOOCCCo3(CO)9 j2 ], 6
˚
The Co(1)–Co(11) distance of 2.419 (4) A (Table 5) is
Two species are found in the solid state:
a
close to that found in a Co3(CO)9(m3-CR) cluster (i.e.
[C10H6(N(CH3)2)2H]1 cation and the anionic cluster
coordination compound shown in Figs. 7 and 8f (Table 7).
Reminiscent of 4, 6 contains a Co(II)Co(II) non-bonded
˚
2.450(4) A) and consistent with an unsupported metal–
metal bond. Of course, one cannot determine from struc-
tural data whether [Co(CO)4]2 or Co(CO)4 is bound to the
cobalt center. Therefore, it is not at all clear how one
should view the formal oxidation state of the Co atom in
the ZnCo core. 1H NMR signals for the coordinated methyl
˚
(3.502(2) and 3.431(2) A in the two independent anions)
dimetal core bridged by three cluster carboxylate ligands.
The Co(II) centers have tetrahedral environments but, in

V. Calvo-Perez et al. / Polyhedron 18 (1999) 1869–1880
1879
contrast to 4, the remaining position in each is filled by a
monodentate cluster ligand. The net result is a trigonal
bipyramidal array of coordinated cluster ligands.
cation. Inhibition of decomposition permits the isolation of
the first anionic cluster metal carboxylate, 6.
We have shown previously that cluster metal carbox-
ylates serve as precursors for heterogeneous catalysts for
hydrogenation reactions. These catalysts possess promising
activities and selectivities for demanding reactions such as
the hydrogenation of crotonaldehyde to the unsaturated
alcohol [11]. Most importantly we have shown that not
only do catalytic properties depend on metal core com-
position but also on the geometry of the cluster array in the
catalyst precursor, e.g. Co4(m4-O)hm-OOC-CCo3(CO)9j6
imparts very different properties to the catalyst than those
generated by Co2hm-OOC-CCo3(CO)9j4. Hence, the com-
pounds illustrated in Fig. 8 provide a library of cluster
arrays that can be used to further change, and hopefully
refine, the properties of the catalysts derived from them.
Consistent with the nonbonded tetrahedral Co(II) cen-
ters, compound 6 is paramagnetic and displays an EPR
signal both in the solid state and in a frozen glass at low
temperature. The IR spectrum distinctly shows the signa-
tures [28] of both bridging and monodentate carboxylates
consistent with the solid state structure. The electronic
spectrum is similar to that of the cluster ligand but the
position of the main band is shifted 15 nm to the red
compared to the free cluster acid.
4. Conclusions
Due to the instability of a cluster carboxylate salt such
as Na[(CO)9Co(m3-CCOO)] towards cluster degradation,
simple metathesis chemistry cannot be used to form the
desired coordination compounds. In past work we have
shown that the protolysis of group 12 metal alkyls provides
one route to cluster carboxylates and cluster ligand ex-
change reactions with M(II) metal acetates provides
another. This work provides additional examples of the
metal acetate exchange route and also establishes new
synthetic pathways to cluster carboxylates. Some are
analogs of known organic carboxylates whereas others
exhibit unusual features that reflect the unique properties
of the tricobalt cluster substituent.
Extension of the normal acetate exchange pathway to Pt
has led to the characterization of 2 with an unusual Pt–Co
core. When applied to metal trifluoroacetates, the ligand
exchange pathway permits the isolation of a M2L4 dimer
carboxylate, 1, with two trans cluster ligands. Thus, we
now have a set of M2L4 compounds with two, three, and
four cluster ligands [10,12,21] In addition, this route
provides an example of a samarium cluster metal car-
boxylate, 2.
Supplementary data
Positional parameters and estimated equivalent isotropic
thermal parameters, anisotropic thermal parameters, full
list of atomic distances and angles are available from the
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK.
Acknowledgements
We are grateful for the support of the National Science
Foundation. VCP also thanks the Department for a Reilly
Fellowship.
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