Synthesis and structural characterization of bimetallic iron-nickel carbido cluster complexes

Article abstract of DOI:10.1021/ic100057x

In acetonitrile solvent, Fe₅(CO)₁₅(μ₅- C), 1, reacts with Ni(COD)₂ at room temperature to afford the iron-nickel complex Fe₅NI(NCMe)(CO)₁₅(μ₆-C), 3. The acetonitrile ligand In 3 can be replaced by CO and NH₃ to yield Fe₅Ni(CO)₁₆(μ₆-C), 4, and Fe ₅Ni(NH₃)(CO)₁₅(μ₆-C), 6, respectively. When refluxed In acetonitrile solvent, compound 3 loses a vertex to form the square pyramidal Fe₄Ni complex Fe₄Ni(NCMe) ₂(CO)₁₂(μ₅-C), 7. Compound 7 readily converts to Fe₄Ni(NCMe)(CO)₁₃(μ₅-C), 8, by losing one of Its acetonitrile ligands. Addition of acetonitrile to 8 gives compound 7. When heated to 110 o°C under an atmosphere of CO, both compounds 7 and 8 furnish the octahedral Fe₄NI₂ complex Fe ₄Ni₂(CO)₁₅(μ₆-C), 9. All six compounds were structurally characterized by single-crystal X-ray diffraction analyses.

Full text of DOI:10.1021/ic100057x

Inorg. Chem. 2010, 49, 3465–3472 3465
DOI: 10.1021/ic100057x
Synthesis and Structural Characterization of Bimetallic Iron-Nickel
Carbido Cluster Complexes
Sumit Saha, Lei Zhu, and Burjor Captain*
Department of Chemistry, University of Miami, Coral Gables, Florida 33124
Received January 11, 2010
In acetonitrile solvent, Fe (CO) (μ -C), 1, reacts with Ni(COD) at room temperature to afford the iron-nickel
5
15
5
2
complex Fe Ni(NCMe)(CO) (μ -C), 3. The acetonitrile ligand in 3 can be replaced by CO and NH to yield
5
15
6
3
Fe Ni(CO) (μ -C), 4, and Fe Ni(NH )(CO) (μ -C), 6, respectively. When refluxed in acetonitrile solvent,
5
16
6
5
3
15
6
compound 3 loses a vertex to form the square pyramidal Fe Ni complex Fe Ni(NCMe) (CO) (μ -C), 7. Compound
4
4
2
12
5
7
readily converts to Fe Ni(NCMe)(CO) (μ -C), 8, by losing one of its acetonitrile ligands. Addition of acetonitrile to 8
4 13 5
gives compound 7. When heated to 110 °C under an atmosphere of CO, both compounds 7 and 8 furnish the
octahedral Fe Ni complex Fe Ni (CO) (μ -C), 9. All six compounds were structurally characterized by single-crystal
4
2
4
2
15
6
X-ray diffraction analyses.
Introduction
For example, it has been shown that it is possible to increase
the activity of Ni based catalysts by alloying them with Fe for
the hydrogenation of CO to methane, an important reaction
A recent and now widely used approach for preparing
bimetallic nanoparticle catalysts is from bimetallic molecular
cluster complexes. Bimetallic nanoparticle catalysts have
been shown to exhibit superior catalytic properties, because
of the presence of different metals such that one metal
performs a certain role in a catalytic cycle and the other
4a
1
that is used in several industrial processes.
Recently, mixed-metal nitride clusters of Fe-Ni were
2
-
5
obtained using the nitrido anion [Fe (CO) (N)] . Iron
4
12
carbide carbonyl cluster complexes, especially Fe (CO) -
5
15
3
(μ -C), 1, have always been of considerable interest to metal
5
performs another function. Supported bimetallic Fe-Ni
particles have also been of interest in heterogeneous catalysis.
6
4
cluster researchers, and in a previous study we reported that
1
reacts with NiCp via metal-metal exchange and metal
2
cluster rearrangement processes, to yield the bimetallic
*
To whom correspondence should be addressed. E-mail: captain@
Ni-Fe carbide containing cluster complex, NiFe (Cp) -
4
2
miami.edu.
7
(
1) (a) Thomas, J. M.; Johnson, B. F. G.; Raja, R.; Sankar, G.; Midgley,
(CO) (μ -C), 2, see eq 1.
10 5
P. A. Acc. Chem. Res. 2003, 36, 20–30. (b) Hermans, S.; Raja, R.; Thomas, J. M.;
Johnson, B. F. G.; Sankar, G.; Gleeson, D. Angew. Chem., Int. Ed. 2001, 40,
1
211–1215. (c) Johnson, B. F. G.; Raynor, S. A.; Brown, D. B.; Shephard, D. S.;
Mashmeyer, T.; Thomas, J. M.; Hermans, S.; Raja, R.; Sankar, G. J. Mol. Catal.
A: Chem. 2002, 182-183, 89–97. (d) Johnson, B. F. G. Coord. Chem. Rev. 1999,
1
90-192, 1269–1285. (e) Hungria, A. B.; Raja, R.; Adams, R. D.; Captain, B.;
Thomas, J. M.; Midgley, P. A.; Golvenko, V.; Johnson, B. F. G. Angew. Chem.,
Int. Ed. 2006, 45, 4782–4785. (f) Adams, R. D.; Blom, D. A.; Captain, B.; Raja,
R.; Thomas, J. M.; Trufan, E. Langmuir 2008, 24, 9223–9226. (g) Siani, A.;
Alexeev, O. S.; Captain, B.; Lafaye, G.; Mar ꢀe cot, P.; Adams, R. D.; Amiridis,
M. D. J. Catal. 2008, 255, 162–179.
(
2) (a) Sinfelt, J. H. Bimetallic Catalysts. Discoveries, Concepts and
Applications; Wiley: New York, 1983. (b) Sachtler, W. M. H. J. Mol. Catal.
984, 25, 1–12.
3) (a) Goodman, D. W.; Houston, J. E. Science 1987, 236, 403–409. (b)
Ichikawa, M. Adv. Catal. 1992, 38, 283–400.
4) (a) Kustov, A. L.; Frey, A. M.; Larsen, K. E.; Johannessen, T.;
Herein we report on the reaction of 1 with bis(1,
1
5
-cyclooctadiene)nickel(0), Ni(COD) , in acetonitrile solvent
2
(
to afford the nickel-iron complex Fe Ni(NCMe)(CO) (μ -C),
5
15
6
(
Nørskov, J. K.; Christensen, C. H. Appl. Catal., A 2007, 320, 98–104. (b)
Ishihara, T.; Eguchi, K.; Arai, H. Appl. Catal. 1987, 30, 225–238. (c) Tee, Y.-H.;
Grulke, E.; Bhattacharyya, D. Ind. Eng. Chem. Res. 2005, 44, 7062–7070. (d)
Schrick, B.; Blough, J. L.; Jones, A. D.; Mallaouk, T. E. Chem. Mater. 2002, 14,
(
5) Pergola, R. D.; Fumagalli, A.; Garlaschelli, L.; Manassero, C.;
Manassero, M.; Sansoni, M.; Sironi, A. Inorg. Chim. Acta 2008, 361,
1
763–1769.
(6) (a) Braye, E. H.; Dahl, L. H.; H u€ bel, W.; Wampler, D. L. J. Am. Chem.
5
140–5147. (e) Park, C.; Baker, R. T. K. J. Catal. 2000, 190, 104–117. (f) Kibria,
Soc. 1962, 84, 4633–4639. (b) Tachikawa, M.; Geerts, R. L.; Muetterties, E. L.
J. Organomet. Chem. 1981, 213, 11–24. (c) Hriljac, J. A.; Harris, S.; Shriver,
D. F. Inorg. Chem. 1988, 27, 816–821.
A. K. M. F.; Mo, Y. H.; Nahm, K. S. Catal. Lett. 2001, 71, 229–236. (g)
Kumbhar, P. S.; Kharkar, M. R.; Yadav, G. D.; Rajadhyaksha, R. A. J. Chem.
Soc., Chem. Commun. 1992, 584–586.
(7) Yempally, V.; Zhu, L.; Captain, B. J. Cluster Sci. 2009, 20, 695–705.
r 2010 American Chemical Society
Published on Web 03/10/2010
pubs.acs.org/IC

3
466 Inorganic Chemistry, Vol. 49, No. 7, 2010
Saha et al.
Table 1. Crystallographic Data for Compounds 3, 4, and 6
3
4
6
empirical formula
formula weight
crystal system
NiFe
811.17
orthorhombic
5
O
15NC18
H
3
NiFe
5
O
16
798.13
C
17
NiFe
787.15
orthorhombic
5 3
O15NC16H
triclinic
lattice parameters
˚
˚
b (A)
˚
c (A)
a (A)
17.3484(6)
9.2771(3)
15.7591(5)
90
90
90
9.0290(5)
9.5672(5)
15.5994(8)
85.381(1)
83.673(1)
63.223(1)
1194.96(11)
P1 (# 2)
2
2.218
3.805
296
58.00
4679
352
1.038
0.000
0.0380; 0.1091
multiscan
0.9278/0.4882
0.617
20.8118(11)
10.3605(5)
10.7284(6)
90
90
90
2313.3(2)
1
Pna2 (# 33)
4
2.260
3.927
296
51.98
4301
344
1.004
0.001
0.0333; 0.0786
multiscan
R (deg)
β (deg)
γ (deg)
3
˚
V (A )
space group
2536.31(14)
Pna2 (# 33)
1
Z value
F
μ (Mo KR) (mm
temperature (K)
4
3
calc (g/cm )
2.124
3.586
296
56.00
5301
363
1.066
0.001
0.0304; 0.0670
multiscan
-
1
)
2Θmax (deg)
no. obs. (I > 2σ(I))
no. parameters
goodness of fit
max. shift in cycle
residuals :R1; wR2
a
absorption correction
max/min
largest peak in final diff. map (e /A )
0.7461/0.5169
0.593
0.6948/0.5072
0.681
-
3
˚
P
P
P
P
P
a
2
2 1/2
]
2
2
R = hkl(||Fobs| - |Fcalc||)/ hkl|Fobs|; R
w
= [ hklw(|Fobs| - |Fcalc|) / hklwFobs
, w = 1/σ (Fobs); GOF = [ hklw(|Fobs| - |Fcalc|) /(ndata
-
1
/2
.
n
vari)]
1
2032 (s), 2007 (v); H NMR (CDCl
3
. In addition, some chemistry with 3 was also studied
3
þ
in ppm): δ = 2.59 (s, 3 H,
þ
þ
which gave new Fe-Ni carbide clusters with varying Fe-Ni
ratios.
CH
5
3
). EI/MS: m/z 769 (M ), 657(M - 4CO), 601 (M - 2CO),
þ
þ
45 (M - 2CO), 461 (M - 3CO). The isotope distribution
pattern is consistent with the presence of one nickel atom and
five iron atoms.
Experimental Section
5 6
Preparation of Fe Ni(CO)16(μ -C), 4. A 100 mg (0.12 mmol)
General Data. Unless indicated otherwise, all reactions were
performed under an atmosphere of Argon. Reagent grade
solvents were dried by the standard procedures and were freshly
amount of 3 was dissolved in 20 mL of toluene in a 50 mL 3-neck
round-bottom flask equipped with a reflux condenser. Carbon
monoxide gas (1 atm) was bubbled through the solution, and the
solution was refluxed at 110 °C with stirring for 1 h. The solvent
was removed in vacuo, and the product was separated on a silica
gel column to yield a purple band of 4 (60 mg, 61% yield) eluted
by pure hexane. The compound was identified by IR in the νCO
distilled prior to use. Infrared spectra were recorded on a Nicolet
3
1
80 FT-IR spectrophotometer. H NMR were recorded on a
Bruker 400 spectrometer operating at 399.993 MHz. Elemental
analyses were performed by Columbia Analytical Services
6
b
-1
(
Tucson, AZ). Mass spectrometric measurements performed
by direct-exposure probe using electron impact ionization
EI) were made on a VG 70S instrument and electrospray mass
region. Spectral data for 4: IR νCO (cm in hexane): 2100(w),
2064 (m), 2042 (s), 2039 (s), 2015 (m), 1883(vw, br).
(
Preparation of Fe Ni(NH )(CO) (μ -C), 6. Conversion of 3
5
3
15
6
spectrometric measurements were obtained on a MicroMass
Q-Tof spectrometer at the University of South Carolina,
to 6. A 10.3 mg (0.013 mmol) amount of 3 was dissolved in 8 mL
of methylene chloride in a 50 mL 3-neck round-bottom flask.
Ammonia gas (1 atm) was bubbled through the solution, and the
solution was stirred at 0 °C (maintained in an ice bath) for
about15 min at which time TLC showed complete consumption
of the starting material. The solvent was removed in vacuo, and
the product was redissolved in methylene chloride and filtered
Columbia, SC. Bis(1,5-cyclooctadiene)nickel(0), Ni(COD)
purchased from Strem Chemicals, used without further purifica-
tion, and stored and handled in a drybox. NH was purchase form
2
, was
3
Matheson Tri-Gas as pure ammonia gas. Fe (CO) (μ -C), 1, was
5
15
5
6b
prepared according to the previously published procedure.
Product separations were performed by TLC in air on
through florisil to give 8.1 mg of 6 (82% yield). Spectral data for
-1
Analtech silica gel GF 250 or 500 μm glass plates. Silica gel
6
: IR νCO (cm in hexane): 2074(w), 2050 (w), 2033 (s), 2023 (m,
(
60-200 μm, 70-230 mesh) used for chromatographic separa-
1
sh), 2006 (w); H NMR (CDCl
3
þ
in ppm): δ = 3.30 (s, 3 H, NH
3
).
tions was purchased from Silicycle. Florisil (F100-500, 60-100
mesh) used for product purifications was purchased from Fisher
Scientific.
þ
þ
EI/MS: m/z 786 (M ), 730(M - 2CO), 674 (M - 2CO), 646
þ
þ
þ
þ
(
M - CO), 618 (M - CO), 590(M - CO), 562 (M - CO).
The isotope distribution pattern is consistent with the presence
of one nickel atom and five iron atoms. Elemental Anal. Calcd:
C, 24.41; H, 0.38; N, 1.77% Found: C, 24.36; H, 0.64; N, 1.72%.
Conversion of 4 to 6. A 15 mg (0.018 mmol) amount of 4 was
dissolvedin20 mLof methylene chloride in a50 mL3-neckround-
bottom flask. Then ammonia gas (1 atm) was bubbled through the
solution, and the solution was stirred at 0 °C (maintained in an ice
bath) for 10 min at which time IR showed complete consumption
of the starting material. The solvent was removed in vacuo, and
the product was redissolved in methylene chloride and filtered
through florisil to give 11.4 mg of 6 (77% yield).
Preparation of Fe Ni(NCMe)(CO) (μ -C), 3. A 100 mg
5
15
6
(
0.14 mmol) amount of 1 and a 58 mg (0.21 mmol) amount of
Ni(COD) were dissolved in 20 mL of acetonitrile in a 50 mL
-neck round-bottom flask. The solution was stirred at room
2
3
temperature for 10 min at which time IR showed complete
consumption of the starting material, 1. The solvent was
removed in vacuo, and the residue was washed with hexane
several times to remove any green side product of Fe (CO) .
3
12
The purple colored residue was dissolved in methylene chloride
and filtered through florisil to give 61.8 mg of 3 (54% yield).
-
1
Spectral data for 3: IR νCO (cm in hexane): 2078(w), 2064 (w),

Article
Inorganic Chemistry, Vol. 49, No. 7, 2010 3467
Table 2. Crystallographic Data for Compounds 7, 8, and 9.
7
8
9
empirical formula
formula weight
crystal system
NiFe
712.35
monoclinic
4
O
12
N
2
C
17
H
6
NiFe
699.30
monoclinic
4
O
13NC16
H
3
Ni
2 4 15 16
Fe O C
772.98
monoclinic
lattice parameters
˚
˚
b (A)
˚
c (A)
a (A)
9.6040(3)
15.3859(6)
16.0687(6)
90
106.2706(5)
90
2279.31(14)
9.5977(5)
15.5438(8)
14.7267(8)
90
91.1432(9)
90
2196.6(2)
10.5011(7)
10.9743(8)
20.5591(14)
90
90.551(1)
90
2369.2(3)
P2 /c (# 14)
1
4
2.167
4.013
296
R (deg)
β (deg)
γ (deg)
3
˚
V (A )
space group
P2
4
1
/c (# 14)
P2 /n (# 14)
4
2.115
1
Z value
F
μ (Mo KR) (mm
temperature (K)
3
calc (g/cm )
2.076
3.362
100
-
1
)
3.489
100
2
Θ
max (deg)
62.00
6821
327
1.107
0.004
0.0197; 0.0485
multiscan
0.8773/ 0.3774
0.443
63.00
5286
317
1.008
0.001
0.0364; 0.0755
multiscan
0.9659/0.4417
0.951
52.90
3226
334
1.056
0.000
0.0499; 0.1158
multiscan
0.9240/0.5007
1.563
no. obs. (I > 2σ(I))
no. parameters
goodness of fit
max. shift in cycle
residuals :R1; wR2
absorption correction
max/min
largest peak in final diff. map (e /A )
a
-
3
˚
P
P
P
P
P
a
2
2 1/2
]
2
2
R =
hkl(||Fobs| - |Fcalc||)/ hkl|Fobs|; R
w
= [ hklw(|Fobs| - |Fcalc|) / hklwFobs
, w = 1/σ (Fobs); GOF = [ hklw(|Fobs| - |Fcalc|) /
1
/2
.
(
n
data - nvari)]
Note: In both cases the reactions do proceed at room tem-
perature; however, owing to some decomposition, the yields at
0
°C are better.
4 2 5
Preparation of Fe Ni(NCMe) (CO)12(μ -C), 7. A 21 mg
0.026 mmol) amount of 3 was dissolved in 15 mL of acetonitrile
(
in a 50 mL 3-neck round-bottom flask equipped with a reflux
condenser. The solution was then heated to reflux with stirring
for 10 min at which time IR showed complete consumption of
the starting material. The solvent was removed in vacuo, and the
product was dissolved in acetonitrile and filtered through silica
gel to give 12.6 mg of 7 (68% yield). Spectral data for 7: IR νCO
-
1
(
(
(
cm in methylene chloride): 2087(w), 2066 (w), 2054 (m), 2030
1
s), 2016 (vs), 1941 (w,br); H NMR (CDCl in ppm): δ = 2.45
3
s, 6H, CH
.93% Found: C, 28.51; H, 0.88; N, 3.93%.
Note: Compound 7 slowly decomposes when dissolved in
3
). Elemental Anal. Calcd: C, 28.66; H, 0.85; N,
3
solvents other than acetonitrile.
Preparation of Fe Ni(NCMe)(CO) (μ -C), 8. Photolysis of
4
13
5
3
to 8. A 15 mg (0.018 mmol) amount of 3 was dissolved in 10 mL
of benzene in a 50 mL 3-neck round-bottom flask equipped with
a reflux condenser. The solution was irradiated using a high-
pressure mercury UV lamp (American Ultraviolet Co.) at the
1
25 wpi setting for 25 min at which time IR showed complete
5
Figure 1. ORTEP showing the molecular structure of Fe Ni(NCMe)-
consumption of the starting material. The solvent was removed
in vacuo, and the product was dissolved in methylene chloride
and filtered through silica gel to give 8.2 mg of 8 (63% yield).
6
(CO)15(μ -C), 3 at 40% thermal ellipsoid probability.
round-bottom flask. Then the solution was stirred at room
temperature for 15 min at which time IR showed complete
consumption of the starting material. The reaction
solution was filtered through silica gel to give 21.2 mg of 7
(97% yield).
-
1
Spectral data for 8: IR νCO (cm in hexane): 2111(w), 2075 (w),
065 (w), 2054 (m), 2043 (w), 2033 (s), 2017 (m), 2010 (m), 1942
2
(
1
w); H NMR (CDCl
þ
3
in ppm): δ = 2.31 (s, 3H, CH
3
). ES /MS
þ
for M , 699. The isotope distribution pattern is consistent with
the presence of one nickel atom and four iron atoms.
4 2 6
Preparation of Fe Ni (CO)15(μ -C), 9. Conversion of 7 to 9.
Conversion of 7 to 8. A 31.9 mg (0.045 mmol) amount of 7 was
dissolved in 10 mL of methylene chloride in a 50 mL 3-neck
round-bottom flask. Then the solution was stirred at room
temperature for 15 min at which time IR showed complete
consumption of the starting material. The solvent was removed
in vacuo, and the product was redissolved in methylene chloride
and filtered through silica gel to give 21.5 mg of 8 (68% yield).
Conversion of 8 to 7. A 21.5 mg (0.031 mmol) amount of 8
was dissolved in 10 mL of acetonitrile in a 50 mL 3-neck
A 21.2 mg (0.029 mmol) amount of 7 was dissolved in 15 mL of
toluene in a 50 mL 3-neck round-bottom flask equipped with a
reflux condenser. Then carbon monoxide gas (1 atm) was
bubbled through the solution and the solution was then heated
to reflux with stirring for 30 min at which time IR showed
complete consumption of the starting material. The solvent was
removed in vacuo, and the product was dissolved in methylene
chloride and filtered through silica gel to give 10.4 mg of 9 (45%
-
1
yield). Spectral data for 9: IR νCO (cm in hexane): 2111(w),

3
468 Inorganic Chemistry, Vol. 49, No. 7, 2010
Saha et al.
a
Table 3. Selected Intramolecular Distances and Angles for Compounds 3 and 6
˚
distance (A)
˚
distance (A)
atom
atom
3
6
atom
atom
3
6
Ni(1)
Ni(1)
Ni(1)
Ni(1)
Fe(1)
Fe(1)
Fe(2)
Fe(3)
Fe(4)
Fe(5)
Fe(2)
Fe(3)
2.7149(7)
2.5653(7)
2.5424(7)
2.7233(7)
2.7009(7)
2.6804(7)
2.7666(9)
2.5361(8)
2.5365(8)
2.6911(8)
2.6450(8)
2.7511(9)
Fe(1)
Fe(1)
Fe(2)
Fe(2)
Fe(3)
Fe(4)
Fe(4)
Fe(5)
Fe(3)
Fe(5)
Fe(4)
Fe(5)
2.6880(7)
2.6875(7)
2.7214(7)
2.6671(7)
2.7163(7)
2.6817(7)
2.7055(9)
2.6847(8)
2.6655(8)
2.6717(8)
2.7440(8)
2.7070(9)
angle (deg)
atom
atom
atom
3
6
Fe(4)
Fe(4)
Fe(3)
Fe(4)
Fe(3)
Fe(2)
Ni(1)
Ni(1)
Ni(1)
Fe(4)
Ni(1)
Ni(1)
Fe(2)
Fe(4)
Ni(1)
Ni(1)
Ni(1)
Ni(1)
Ni(1)
Ni(1)
Fe(2)
Fe(3)
Fe(3)
Fe(3)
Fe(4)
Fe(4)
Fe(5)
Fe(5)
Fe(3)
Fe(2)
Fe(2)
Fe(5)
Fe(5)
Fe(5)
Fe(3)
Fe(4)
Fe(2)
Fe(2)
Fe(5)
Fe(3)
Ni(1)
Ni(1)
64.25(2)
92.79(2)
61.972(19)
61.117(19)
92.38(2)
58.739(19)
56.314(18)
57.464(18)
61.714(19)
88.92(2)
65.50(2)
91.84(3)
60.17(2)
62.29(2)
93.63(3)
58.60(2)
55.63(2)
57.26(2)
64.21(2)
89.63(2)
61.66(2)
57.24(2)
62.11(2)
56.05(2)
62.771(19)
58.28(2)
60.473(19)
56.112(18)
a
Estimated standard deviations in the least significant figure are given in parentheses.
2
076 (m), 2065 (m), 2054 (w), 2043 (s), 2033 (m), 2028 (m), 2022
þ
þ
þ
(m), 1963 (w). EI/MS: m/z 772 (M ), 744(M - CO), 716 (M -
CO). The isotope distribution pattern is consistent with the
presence of two nickel atoms and four iron atoms.
Conversion of 8 to 9. A 21.5 mg (0.031 mmol) amount of 8 was
dissolved in 15 mL of toluene in a 50 mL 3-neck round-bottom
flask equipped with a reflux condenser. Then carbon monoxide
gas (1 atm) was bubbled through the solution, and the solution
was then heated to reflux with stirring for 30 min at which time
IR showed complete consumption of the starting material. The
solvent was removed in vacuo, and the product was dissolved in
methylene chloride and filtered through silica gel to give 10.4 mg
of 9 (44% yield).
Crystallographic Analysis. Single crystals of 3, 4, 6, 8, and 9
suitable for diffraction analysis were all grown by slow evapora-
tion of solvent from solutions in hexane/methylene chloride
solvent mixture at - 20 °C. Single crystals of 7 suitable for
diffraction analysis were grown by slow evaporation of solvent
from a solution of hexane/methylene chloride/acetonitrile sol-
vent mixture at - 20 °C. The data crystals for 3, 4, 6, and 9 were
glued onto the end of a thin glass fiber. Data crystals for 7 and 8
were mounted onto the end of a thin glass fiber using Paratone-
N. X-ray intensity data were measured by using a Bruker
SMART APEX2 CCD-based diffractometer using Mo KR
Figure 2. ORTEP showing the molecular structure of Fe
5
Ni(CO)16-
6
(μ -C), 4 at 40% thermal ellipsoid probability.
idealized positions and included as standard riding atoms
during the least-squares refinements. Crystal data, data collec-
tion parameters, and results of the analyses are listed in Tables 1
and 2.
8
˚
radiation (λ = 0.71073 A). The raw data frames were integrated
with the SAINTþ program by using a narrow-frame integration
8
algorithm. Corrections for Lorentz and polarization effects
Compounds 3 and 6 crystallized in the orthorhombic crystal
system. The systematic absences in the intensity data were
consistent with either of the space groups Pnma or Pna2 . The
1
structure could only be solved in the latter space group. Com-
pound 4 crystallized in the triclinic crystal system. The space
group P1 was assumed and confirmed by the successful solution
and refinement of the structure. Compounds 7, 8, and 9 crystal-
lized in the monoclinic crystal system. For compounds 7 and 9
the systematic absences in the intensity data were consistent with
were also applied with SAINTþ. An empirical absorption
correction based on the multiple measurement of equivalent
reflections was applied using the program SADABS. All struc-
tures were solved by a combination of direct methods and
difference Fourier syntheses, and refined by full-matrix least-
squares on F , by using the SHELXTL software package. All
non-hydrogen atoms were refined with anisotropic displace-
ment parameters. Hydrogen atoms were placed in geometrically
2
9
(
8) Apex2 Version 2.2-0 and SAINTþ Version 7.46A; Bruker Analytical
X-ray System, Inc.: Madison, WI, 2007.
9) Sheldrick, G. M. SHELXTL, Version 6.1; Bruker Analytical X-ray
Systems, Inc.: Madison, WI, 2000.
the unique space group P2
tic absences in the intensity data were consistent with the unique
space group P2 /n.
1
/c and for compound 8 the systema-
(
1

Article
Inorganic Chemistry, Vol. 49, No. 7, 2010 3469
a
Table 4. Selected Intramolecular Distances and Angles for Compound 4
˚
distance (A)
˚
distance (A)
atom
atom
atom
atom
Ni(1)
Ni(1)
Ni(1)
Ni(1)
Fe(1)
Fe(1)
Fe(2)
Fe(3)
Fe(4)
Fe(5)
Fe(2)
Fe(3)
2.6613(7)
2.5095(7)
2.6957(8)
2.6705(7)
2.6615(7)
2.7194(7)
Fe(1)
Fe(1)
Fe(2)
Fe(2)
Fe(3)
Fe(4)
Fe(4)
Fe(5)
Fe(3)
Fe(5)
Fe(4)
Fe(5)
2.6415(7)
2.7354(7)
2.7237(7)
2.6910(7)
2.6957(7)
2.6588(7)
atom
atom
atom
angle (deg)
atom
atom
atom
angle (deg)
Fe(3)
Fe(3)
Fe(2)
Fe(3)
Fe(2)
Fe(5)
Ni(1)
Ni(1)
Fe(5)
Ni(1)
Ni(1)
Ni(1)
Ni(1)
Ni(1)
Ni(1)
Fe(2)
Fe(2)
Fe(2)
Fe(2)
Fe(5)
Fe(5)
Fe(4)
Fe(4)
Fe(4)
Fe(5)
Fe(3)
Fe(3)
63.49(2)
94.17(2)
60.623(19)
62.26(2)
90.74(2)
59.400(19)
59.857(19)
55.538(19)
89.00(2)
Ni(1)
Ni(1)
Fe(4)
Fe(5)
Fe(5)
Fe(3)
Fe(4)
Fe(4)
Ni(1)
Fe(3)
Fe(3)
Fe(3)
Fe(4)
Fe(4)
Fe(4)
Fe(5)
Fe(5)
Fe(5)
Fe(4)
Fe(2)
Fe(2)
Fe(3)
Ni(1)
Ni(1)
Ni(1)
Fe(2)
Fe(2)
62.26(2)
60.97(2)
89.41(2)
90.27(2)
59.827(19)
55.480(19)
60.77(2)
90.89(2)
59.521(19)
a
Estimated standard deviations in the least significant figure are given in parentheses.
Results and Discussion
The reaction of Fe (CO) (μ -C), 1, with Ni(COD) in
5
15
5
2
acetonitrile solvent at room temperature afforded the new
bimetallic Fe-Ni cluster complex Fe Ni(NCMe)(CO) (μ -
5
15
6
C), 3, in 54% yield. Compound 3 was characterized by a
1
combination of IR, H NMR, mass spectrometry, and single
crystal X-ray diffraction analyses. An Oak Ridge thermal
ellipsoid plot (ORTEP) showing the molecular structure of 3
is shown in Figure 1. Selected bond distances and angles are
listed in Table 3. Compound 3 consist of an octahedral cluster
of five iron atomsand one nickel atom with the carbide ligand
encapsulated in the center of the Fe Ni octahedron. The
5
˚
Ni-Carbide distance of 1.831(3) A, is not significantly
different from the Fe-Carbide distances, range 1.888(3)-
˚
1
.916(3) A. Also the Fe-Carbide distances are similar to the
˚
Fe-Carbide distances in 1, range 1.87(3)-1.96(3) A, and in
the hexanuclear iron carbide anionic cluster complex
PPN] [Fe (CO) (SO )(μ -C)], range 1.870(10)-1.915(7) A.
Figure 3. ORTEP showing the molecular structure of Fe
(
5 3
Ni(NH )-
CO)15(μ -C), 6 at 40% thermal ellipsoid probability.
6
1
0
˚
[
2
6
15
2
6
Figure2 thestructure is very similar to compound 3 where the
acetonitrile ligand on the Ni atom has been replaced by a
carbonyl group. Compound 4 is isostructural to the
known platinum-ruthenium mixed-metal cluster complex
There is a terminal acetonitrile ligand from the reaction
solvent that is coordinated to the Ni atom. There are two
bridging CO ligands, and these bridge the Ni(1)-Fe(3) bond
˚
˚
(
2.5653(7) A), and the Ni(1)-Fe(4) bond (2.5424(7) A) and
1
2
PtRu (CO) (μ -C), 5, that was prepared previously by
these two metal-metal bonds are shorter than all the other
metal-metal bonds in the octahedral framework, range
5
16
6
Adams and Wu. Just like in compound 5, one of
˚
the metal-metal bonds has a bridging carbonyl group,
2
.6671(7)-2.7214(7) A. Compound 3 contains 86 cluster
˚
Ni(1)-Fe(3) = 2.5095(7) A, which is considerably shorter
valence electrons which is in accord to conventional electron
counting theories if all six transition metal atoms formally
have an 18-electron configuration.
than all the other metal-metal bonds in 4. Compound 4 can
11
be prepared by the reaction of the dianion [NEt ] -
4 2
[
(
Fe (CO) (μ -C)] with Ni(COD) to yield [Fe Ni(CO) -
5 14 5 2 5 14
2
Whensolutions of 3 were exposed to carbon monoxide gas,
compound 3 reacts with CO at 110 °C to furnish the binary
carbonyl cluster complex Fe Ni(CO) (μ -C), 4, in 61%
-
COD)(μ -C)] . Substitution of the COD group with CO
5
3
þ
followed by oxidation with Fe then gives the desired
5
16
6
6b
compound 4. The yield of this reaction is not reported,
and in our hands we were able to obtain a maximum yield
of 15% following this previously reported procedure.
Our preparation is a more convenient and perhaps “better”
yielding procedure for the synthesis of compound 4.
yield. Compound 4 was prepared a number of years ago by
6b
Muetterties et al., and its structure was formulated accu-
rately based on IR, mass spectrometry, and elemental ana-
lyses. We have now obtained a crystal structure for
compound 4 which is shown in Figure 2. Selected bond
distances and angles are listed in Table 4. As can be seen in
Both compounds 3 and 4 react with ammonia gas at 0 °C to
give the compound Fe Ni(NH )(CO) (μ -C), 6, in 82% and
5
3
15
6
7
7% yields, respectively. The solid state structure of 6 is
(
10) Bogdan, P. L.; Sabat, M.; Sunshine, S. A.; Woodcock, C.; Shriver,
D. F. Inorg. Chem. 1988, 27, 1904–1910.
11) (a) Mingos, D. M. P. Acc. Chem. Res. 1984, 17, 311–319. (b) Mingos,
D. M. P. Introduction to Cluster Chemistry; Prentice Hall: Engelwood Cliffs, NJ,
990; Chapter 2.
shown in Figure 3, and selected bond distances and angles are
listed in Table 3. The structure of compound 6 is similar to
(
1
(12) Adams, R. D.; Wu, W. J. Cluster Sci. 1991, 2, 271–290.

3
470 Inorganic Chemistry, Vol. 49, No. 7, 2010
Saha et al.
Figure 4. ORTEP showing the molecular structure of Fe
CO)12(μ -C), 7 at 50% thermal ellipsoid probability.
4
Ni(NCMe)
2
-
Figure 5. ORTEP showing the molecular structure of Fe
(
4
Ni(NCMe)-
(
5
CO)13(μ -C), 8 at 50% thermal ellipsoid probability.
5
a
Table 5. Selected Intramolecular Distances and Angles for Compounds 7 and 8
˚
distance (A)
atom
atom
7
8
Ni(1)
Ni(1)
Ni(1)
Fe(1)
Fe(1)
Fe(1)
Fe(2)
Fe(3)
Fe(1)
Fe(2)
Fe(4)
Fe(2)
Fe(3)
Fe(4)
Fe(3)
Fe(4)
2.5612(2)
2.6696(2)
2.5913(2)
2.5802(2)
2.6346(2)
2.5527(2)
2.6265(2)
2.6253(2)
2.5129(5)
2.6467(5)
2.6077(5)
2.5948(5)
2.6144(5)
2.5879(5)
2.6399(5)
2.6323(5)
angle (deg)
atom
atom
atom
7
8
Fe(1)
Fe(1)
Fe(4)
Fe(4)
Ni(1)
Fe(4)
Ni(1)
Fe(4)
Fe(2)
Fe(1)
Fe(1)
Fe(3)
Fe(4)
Fe(2)
Fe(4)
Fe(1)
Ni(1)
Ni(1)
Ni(1)
Ni(1)
Fe(1)
Fe(1)
Fe(1)
Fe(1)
Fe(1)
Fe(1)
Fe(2)
Fe(2)
Fe(2)
Fe(3)
Fe(3)
Fe(3)
Fe(4)
Fe(4)
Fe(4)
Fe(2)
Fe(2)
Ni(1)
Fe(2)
Fe(2)
Fe(3)
Fe(3)
Fe(3)
Fe(3)
Ni(1)
Ni(1)
Fe(1)
Fe(1)
Fe(2)
Ni(1)
Fe(3)
59.394(6)
60.681(14)
60.319(14)
90.295(16)
61.471(14)
62.395(15)
91.903(17)
92.924(17)
60.790(14)
60.896(14)
59.919(14)
57.286(14)
89.370(16)
59.107(14)
59.184(14)
89.911(16)
57.848(13)
90.381(16)
59.068(6)
91.320(7)
60.890(7)
62.562(7)
94.295(8)
89.704(8)
60.783(7)
60.473(7)
60.789(7)
58.370(6)
87.572(8)
58.067(6)
58.737(6)
91.538(8)
59.716(6)
89.260(8)
Figure 6. ORTEP showing the molecular structure of Fe
(μ -C), 9 at 40% thermal ellipsoid probability.
6
4 2
Ni (CO)15-
π- acceptor ligands, whereas an NH ligand is only capable of
3
13,14
σ donation.
Thermolysis of compound 3 up to temperatures of 110 °C
in solvents other than acetonitrile (benzene and toluene
solvent at reflux) decomposed compound 3 to give insoluble,
probably metallic particles. However, when compound 3 was
refluxed in acetonitrile solvent, the new Fe Ni carbido cluster
4
complex Fe Ni(NCMe) (CO) (μ -C), 7, was obtained in
4
2
12
5
6
7
8% yield. An ORTEP showing the molecular structure of
is shown in Figure 4, and selected bond distances and angles
a
Estimated standard deviations in the least significant figure are
given in parentheses.
are listed in Table 5. The complex consists of a square
pyramidal cluster of four iron atoms and one nickel atom
with a peripheral or exposed carbide ligand in the center of
the base of the square pyramid. The nickel atom in 7 is not in
the apical position but occupies one of the basal positions of
the square pyramid. The two acetonitrile ligands are termin-
both compounds 3 and 4; however, there now is an ammonia
ligand on the Ni atom. It is interesting to note here that the
replacement of the acetonitrile ligand in 3 by an ammonia
group and replacement of a carbonyl ligand by an ammonia
group is very facile. This is surprising since both CO and
NCMe are betting coordinating ligands than ammonia as
both CO and NCMe are good σ donors as well as good
1
ally coordinated to the nickel atom. The H NMR spectrum
for 7 should show two resonances for the methyl groups on
(14) (a) Kukushkin, Y. N.; Aleksandrova, E. A.; Pakhomova, T. B.;
(
13) (a) Kovacs, A.; Frenking, G. Organometallics 2001, 20, 2510–2524.
b) Varshavsky, Y. S.; Galding, M. R.; Cherkasova, T. G.; Smirnov, S. N.;
Khrustalev, V. N. J. Organomet. Chem. 2007, 692, 5788–5794.
Vlasova, R. A. Zh. Obshch. Khim. 1994, 64, 70507. (b) Intini, F. P.; Pellicani,
R. Z.; Boccarelli, A.; Sasanelli, R.; Coluccia, M.; Natile, G. Eur. J. Inorg. Chem.
2008, 4555–4561.
(

Article
Inorganic Chemistry, Vol. 49, No. 7, 2010 3471
a
Table 6. Selected Intramolecular Distances and Angles for Compound 9
˚
distance (A)
˚
distance (A)
atom
atom
atom
atom
Ni(1)
Ni(1)
Ni(1)
Ni(1)
Ni(2)
Ni(2)
Ni(2)
Fe(2)
Fe(3)
Fe(4)
Fe(1)
Fe(2)
2.4642(11)
2.6686(12)
2.6798(11)
2.6857(11)
2.6874(11)
2.6994(12)
Ni(2)
Fe(1)
Fe(1)
Fe(1)
Fe(2)
Fe(3)
Fe(4)
Fe(2)
Fe(3)
Fe(4)
Fe(3)
Fe(4)
2.6685(11)
2.6707(12)
2.7188(12)
2.6535(11)
2.6530(12)
2.6505(12)
atom
atom
atom
angle (deg)
atom
atom
atom
angle (deg)
Ni(2)
Ni(2)
Fe(2)
Ni(2)
Fe(2)
Fe(3)
Ni(1)
Ni(1)
Fe(4)
Fe(3)
Fe(3)
Ni(1)
Ni(1)
Ni(1)
Ni(1)
Ni(1)
Ni(1)
Ni(1)
Ni(2)
Ni(2)
Ni(2)
Fe(2)
Fe(2)
Fe(2)
Fe(2)
Fe(3)
Fe(3)
Fe(4)
Fe(4)
Fe(4)
Fe(4)
Fe(2)
Fe(2)
Ni(1)
Ni(2)
Ni(2)
63.31(3)
92.74(3)
59.48(3)
62.24(3)
90.83(3)
59.21(3)
62.95(3)
62.04(3)
90.54(4)
60.47(3)
88.24(3)
54.65(3)
Fe(4)
Fe(4)
Fe(2)
Fe(3)
Fe(3)
Ni(1)
Fe(4)
Fe(4)
Fe(2)
Fe(3)
Fe(3)
Ni(2)
Fe(3)
Fe(3)
Fe(3)
Fe(2)
Fe(2)
Fe(2)
Fe(3)
Fe(3)
Fe(3)
Fe(4)
Fe(4)
Fe(4)
Fe(2)
Ni(1)
Ni(1)
Ni(1)
Ni(2)
Ni(2)
Fe(2)
Ni(1)
Ni(1)
Ni(2)
Ni(1)
Ni(1)
91.95(4)
60.51(3)
60.05(3)
60.47(3)
88.24(3)
54.65(3)
91.95(4)
60.51(3)
60.05(3)
88.94(3)
60.29(3)
54.80(3)
a
Estimated standard deviations in the least significant figure are given in parentheses.
each of the NCMe ligands, as the two NCMe ligands are
inequivalent. Atom N(1) on one of the NCMe groups has
approximate trans coordination to the Ni(1)-Fe(1) bond,
N(1)-Ni(1)-Fe(1) = 159.67(3)°, whereas atom N(2) on the
other NCMe group is coordinated approximately cis to the
are bonded to each other, with one nickel atom occupying an
apical position and the other, one of the positions on the
square plane of the octahedron. Just as in compounds 3, 4,
and 6, there is a carbon ligand that is encapsulated in the
center of the Fe Ni octahedron; Metal-Carbide distances
4
2
1
˚
same bond, N(2)-Ni(1)-Fe(1) = 103.73(3)°. However, H
range is 1.861(5)-1.908(5) A. The Ni(1)-Ni(2) bond dis-
˚
NMR at room temperature showed a single resonance
indicating that the two NCMe groups are rapidly exchanging
on the NMR time scale, via most probably a mechanism
involving a polytopal rearrangement process on the nickel
atom. It is well-known that CO, CNR, NCR, and phosphine
tance of 2.4642(11) A is significantly shorter than that found
in the nitrido dianionic cluster complex, [HNi Fe (CO) -
2
4
13
2-
5
˚
(μ -C)] , 10, (2.724(1) A), and can be attributed to the
6
carbonyl ligand that bridges the Ni(1)-Ni(2) edge of the
octahedron. The other metal-metal bond distances are
similar to those found in 10. With 15 CO ligands the cluster
valence count is 86 which is consistent for a closo octahedron
15
ligands undergo rapid exchange process.
Photolysis of compound 3 at room temperature in benzene
11
solvent, however, afforded another Fe Ni carbido cluster
structure as seen in the solid state for 10.
4
complex Fe Ni(NCMe)(CO) (μ -C), 8, in 63% yield. The
Bimetallic Fe-Ni cluster complexes from the reaction of 1
4
13
5
molecular structure of 8 is shown in Figure 5, and selected
bond distances and angles are listed in Table 5. The structure
of 8 is very similar to that of 7, where in place of one of the
NCMe ligands on the nickel atom in 7, there is a terminal
carbonyl ligand. All the bond lengths in 8 are very similar to
those found in 7, see Table 5. When compound 8 is dissolved
in acetonitrile solvent at room temperature, substitution of a
CO ligand with acetonitrile occurs to give compound 7 in
with Ni(COD) were only obtained when the solvent acet-
2
onitrile was used. In the other common solvents and/or at
elevated temperatures, the reaction of 1 with Ni(COD) does
2
proceed, however, mainly with decomposition of the starting
materials, and we were unable to isolate and characterize any
Ni-Fe bimetallic complexes. As possible control experi-
ments, there was no reaction of Ni(COD) with acetonitrile.
2
In fact Ni(COD) is not soluble in acetonitrile solvent at
2
9
7% yield. Interestingly when CO was added at room
room temperature. When 1 was dissolved in acetonitrile
solvent at room temperature, compound 1 slowly degraded
to the trinuclear cluster Fe (CO) . However, when both 1
temperature to 7 to obtain 8, the new compound Fe Ni -
4
2
(
CO) (μ -C), 9, was obtained. Compound 7 when dissolved
15 6
3
12
in solvents other than acteonitrile, such as methylene chloride,
slowly “decomposes” to 8 in 68% yield. Compound 9 as
shown in Figure 6 (selected bond distances and angles are
listed in Table 6) contains an octahedral cluster composed of
four iron atoms and two nickel atoms. The two nickel atoms
and Ni(COD) were dissolved in acetonitrile solvent at room
2
temperature as mentioned above, complex 3 formed in 54%
yield. It is known and has been shown that the Ru analogue
of 1, Ru (CO) (μ -C) 11, in acetonitrile solvent forms the
5
15
5
16
open metal framework structure, 12, as shown in eq 2 via
bond homolysis of the square pyramidal geometry of 11 that
can provide vacant coordination sites without cluster frag-
mentation. However, we were not able to detect the presence
of such a species when 1 was dissolved in acetonitrile but
believe that such a process followed by migration of the
(
15) (a) Jesson, J. P.; Muetterties, E. L. In Dynamic Nuclear Magnetic
Resonance Spectroscopy; Jackman, L., Cotton, F. A., Eds.; Academic Press: New
York, 1975; Chapter 8. (b) Adams, R. D.; Cotton, F. A. In Dynamic Nuclear
Magnetic Resonance Spectroscopy; Jackman, L., Cotton, F. A., Eds.; Academic
Press: New York, 1975; Chapter 12. (c) Johnson, B. F. G.; Benfield, R. E. In
Transition Metal Clusters; Johnson, B. F. G., Ed.; Wiley, Chichester, U.K., 1980;
Chapter 7. (d) Muetterties, E. L.; Band, E. Chem. Rev. 1978, 78, 639–658. (e)
Aime, S.; Dastru, W.; Gobetto, R.; Krause, J.; Violano, L. Inorg. Chim. Acta
(16) (a) Johnson, B. F. G.; Lewis, J.; Nicholls, J. N.; Oxton, I. A.;
Raithby, P. J.; Rosales, M. J. Chem. Commun. 1982, 289–290. (b) Dyson,
P. J. Adv. Organomet. Chem. 1998, 43, 43–124.
1
995, 235, 357–366. (f) Adams, R. D.; Captain, B.; Fu, W. J. Cluster Sci. 2001,
1
2, 303–312.

3
472 Inorganic Chemistry, Vol. 49, No. 7, 2010
Saha et al.
Scheme 1
acetonitrile ligand to nickel perhaps facilitates the facile
formation of 3.
6 by reacting with ammonia gas. Compound 3 when dis-
solved in acetonitrile solvent and heated to reflux results in
removal of a vertex occupied by an iron atom in 3 along with
substitution of a CO ligand with acetonitrile to give a nido
octahedral (square pyramidal) cluster 7. Compound 7 is
stable in the solid state and in acetonitrile solvent, but loses
one of its acetonitrile ligands in methylene chloride solvent to
yield complex 8. Compound 8 can be converted to 7 by
dissolving 8 in acetonitrile solvent. Compound 7 reacts with
CO to form the Fe Ni octahedral cluster 9 via first forming
4
2
compound 8. Studies of some of these compounds to serve
as molecular precursors to new nickel-iron nanoparticle cata-
A summary of the products that were obtained in this
study is shown in Scheme 1. The pentairon carbide carbonyl
1
lysts for applications in heterogeneous catalysis are in progress.
cluster 1 reacts with Ni(COD) in acetonitrile solvent at room
2
temperature to yield the NiFe octahedral cluster, 3, which
Acknowledgment. This research was supported by
Start-up Funds provided by the University of Miami.
5
has an acetonitrile ligand from the reaction solvent on the
nickel atom. The acetonitrile ligand in 3 can be displaced by
CO to yield the binary carbonyl cluster complex 4. Ammonia
gas can also replace the acetonitrile ligand in 3 to yield
complex 6. Appropriately compound 4 can be converted to
Supporting Information Available: CIF files for each of the
structural analyses. This material is available free of charge via
the Internet at http://pubs.acs.org.