0022-4766/13/5404-0747

©

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Journal of Structural Chemistry. Vol. 54, No. 4, pp. 747-751, 2013

Original Russian Text Copyright © 2013 by D. A. Bashirov, N. V. Kuratieva, A. I. Smolentsev, S. N. Konchenko

STRUCTURE OF NEW CARBONYL CLUSTER COMPLEXES

WITH THE [Fe4(µ4-Q)(µ4-AsCH3)(CO)11] CORE

D. A. Bashirov,1,2

N. V. Kuratieva,1,2

A. I. Smolentsev,1

and S. N. Konchenko1,2

UDC 541.49:548.736

By X-ray diffraction study the structure of two new carbonyl cluster complexes of the composition [Fe4(μ4-

Q)(μ4-AsMe)(CO)11], where Q = Se or Te, is determined. The structures are molecular, and the selenium-

containing cluster complex crystallizes in the form of a solvate with toluene.

DOI: 10.1134/S0022476613040136

Keywords: carbonyl cluster, iron, synthesis, crystal structure.

Carbonyl cluster complexes containing atoms of transition and non-transition elements in a given stoichiometry are

viewed as the precursors of materials with the precisely specified elemental composition and structure [1]. The convenient

objects for the synthesis of a wide range of polyelemental cluster complexes are chalcogenide carbonyl clusters of iron whose

framework can be modified by adding or substituting individual metal-organic vertices [2-5].

Previously, we have developed convenient methods for the synthesis of cluster complexes of the [Fe3(μ3-Q)(μ3-

ER)(CO)9] type containing different combinations of elements of 15 (E) and 16 (Q) groups: Se/As, Te/As, Se/Sb, Te/Sb,

Se/Bi [6-11]. In their structure and properties these cluster complexes are similar to chalcogenide [Fe3(μ3-Q)(μ3-Q′)(CO)9]

clusters, where Q and Q′ are the same or different chalcogen atoms. Substitution reactions of one {Fe(CO)3} group by

isolobal moieties are typical of both cluster types, e.g.: Pd(PPh3)2, Pt(PPh3)2, MCp* (M = Rh, Ir) [12–14]. For [Fe3(μ3-

Q)2(CO)9] (Q = Se, Te) clusters reactions are also known that lead to an increase in the cluster core, e.g., interaction with

[Fe(CO)5] resulting in the formation of octahedral [Fe4(μ3-Q)2(CO)11] [15] complexes.

This paper studies the reactions of [Fe3(μ3-Q)(μ3-AsCH3)(CO)9] (Q = Se, 1a, Q = Te, 1b) with a carbonyl

[Fe2(CO)9] complex, which also give the products of the addition of the {Fe(CO)2} moiety to the cores of initial clusters.

EXPERIMENTAL

All procedures related to the synthesis and isolation of the products were performed in an argon atmosphere

(Schlenk equipment); toluene was subjected to dehydration and degassing by boiling and distillation in an argon atmosphere

using metal Na as a drying agent [16]. The precursors [Fe3(μ3-Q)(μ3-AsMe)(CO)9] (Q = Se, Te) [11] and [Fe2(CO)9] [17]

were synthesized using the known procedures.

The PMR spectra (chemical shifts: δ, ppm) were recorded at room temperature on a Bruker Advance 300

spectrometer at a frequency of 300.132 MHz; the solvent signals were used as the internal standard (δH = 5.31 for CD2Cl2).

1A. V. Nikolaev Institute of Inorganic Chemistry, Siberian Division, Russian Academy of Sciences, Novosibirsk; bashirov@ngs.ru. 2Novosibirsk State University. Translated from Zhurnal Strukturnoi Khimii, Vol. 54, No. 4, pp. 702-706, July-August, 2013. Original article submitted September 12, 2012; revised October 12, 2012.

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TABLE 1. Crystallographic Data and Structure Refinement Results

Parameter 2a⋅0.5(C7H8) 2b

M 746.49 749.06 T, K 150(2) 100(2)

Symmetry Monoclinic Monoclinic Space group C2/m P21/n

a, b, c, Å 17.3780(7), 15.0302(5), 9.3070(4) 8.3988(2), 13.9310(4), 16.6351(4)

β, deg 116.430(1) 99.447(1)

V, Å3 2176.85(15) 1919.97(9) Z 4 4

ρ(calc.), g/cm3 2.278 2.591

F(000) 1436 1408

μ, mm–1 5.849 6.216

Crystal size, mm 0.12×0.05×0.02 0.36×0.32×0.20

2θmax, deg 56.56 61.02

Intervals of reflection indices –23 ≤ h ≤ 22, –13 ≤ k ≤ 20, –11 ≤ l ≤ 12 –11 ≤ h ≤ 10, –19 ≤ k ≤ 17, –23 ≤ l ≤ 20Number of measured/indep. reflections 8764/2803 [R(int) = 0.0280] 17481/5838 [R(int) = 0.0220] Completeness of data collection over

θ = 25.25° 99.8% 99.8%

Number of reflections with I ≥ 2σ(I ) 2221 5303

Number of refined parameters 166 263

R factors for I ≥ 2σ(I ) R1 = 0.0248, wR2 = 0.0592 R1 = 0.0188, wR2 = 0.0406

R factors for all reflections R1 = 0.0386, wR2 = 0.0626 R1 = 0.0224, wR2 =0.0415 GOOF for F 2 0.970 1.083

Residual electron density (min/max, e/Å3) –0.353/0.778 –0.692/0.495

The IR spectra were recorded for the solutions in methylene chloride on a Bruker IFS28 spectrometer.

The elemental analysis was performed using a Eurovector EuroEA3000 CHN analyzer.

PRODUCTION OF [Fe4(µ4-Q)(µ4-AsMe)(CO)11] (2a,b)

To the mixture of solid [Fe3(μ3-Q)(μ3-AsMe)(CO)9] (0.141 mmol, 0.083 g (Q = Se) or 0.090 g (Q = Te)) and

[Fe2(CO)9] (0.668 mmol, 0.243 g) at room temperature 15 ml of toluene were added and left to stir for 12 h. The obtained

solution was filtered from a black residue. When the solution is cooled to –12°C, the crystals of 2a⋅0.5C7H8 and 2b

compounds precipitate; yield is approximately 40%.

2a⋅0.5C7H8. IR spectrum (ν, cm–1): 2033 s, 2005 m, 1982 m. The 1H NMR (CD2Cl2): 1.36 (s, 3H, As–CH3), 2.34 (s,

3H, CH3, toluene), 7.17 (m, CH, toluene), 7.25 (m, CH, toluene). Found, %: C 24.8, H 0.97. C15.5H7AsFe3O11Se. Calculated,

%: C 24.9, H 0.94.

2b. IR spectrum (ν, cm–1): 2027 s, 2000 m, 1977 m. The 1H NMR (CD2Cl2): 1.41 (s, 3H, As–CH3). Found, %:

C 18.9, H 0.54. C12H3AsFe3O11Te. Calculated, %: C 19.2, H 0.40.

Single crystals for the X-ray diffraction study were selected directly from the crystalline masses of the substances.

The X-ray diffraction study of the complexes was performed by the standard technique on a Bruker-Nonius X8 Apex

automated four-circle diffractometer with a two-dimensional CCD detector using molybdenum radiation (λ = 0.71073 Å) and

graphite monochromator. The reflection intensities were measured by ϕ-scanning of narrow (0.5°) frames. Absorption was

taken into account semi-empirically using the SADABS software [18]. The structures were solved by a direct method and

refined by full-matrix LSM in the anisotropic for non-hydrogen atoms approximation using the SHELXTL software [19];

the details of the experiments and refinement are given in Table 1. Sites of hydrogen atoms were refined in the rigid body

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approximation. The crystallographic data were deposited with CCDC under numbers 899116 and 899117 on the website

www.ccdc.cam.ac.uk/data_reguest/cif.

RESULTS AND DISCUSSION

The reactions of the [Fe3(μ3-Q)2(CO)9] (Q = Se, Te) clusters with [Fe(CO)5] proceed under UV irradiation [15]. It is

known that under these conditions iron pentacarbonyl dimerizes and in fact the reactions occur with [Fe2(CO)9], hence, in our

case, we used ready iron nonacarbonyl as the initial reagent. The interaction of 1a,b with [Fe2(CO)9] in toluene leads to

products of the formal addition of an extra {Fe(CO)2} moiety to the initial cluster framework: 2a,b; therewith one of the CO

ligands becomes bridged (Scheme 1). Monitoring the reaction with TLC showed that in 12 h the product amount in the mixture

reaches its maximum, the initial reagents being also present in the solution. The obtained products appeared to be unstable:

Scheme 1

when dissolved in toluene, 2a,b completely decompose in several hours at room temperature with the formation of initial 1a,b

(monitoring with TLC) and a black residue insoluble in organic solvents. Apparently, the presence of the 2a,b clusters in rather

large amounts in the reaction mixture can be explained by an excess of the initial iron carbonyl, which suppresses the

decomposition of the products. At the same time, in the solid state, compounds 2a,b can be stored in an argon atmosphere

without decomposition for several months. Note that analogous phosphorus-containing [Fe4(μ4-Q)(μ4-PPri)(CO)11] (Q = S, Se,

Te, Pri is isopropyl) clusters are much more stable in the solution. This conclusion can be drawn from the fact that they were

isolated using column chromatography [20, 21]. This pattern is typical of [Fe4(µ4-Q)2(CO)11] (Q = S, Se, Te) clusters, and with

an increase in the radius of chalcogens in the cluster core the stability of the complexes in the solution decreases: while the

sulfur-containing clusters do not decompose when dissolved, more heavy analogues gradually break down with the formation of

[Fe3(µ3-Q)2(CO)9], therewith the tellurium-containing clusters decompose much faster [15].

Cluster cores in the structures of 2a,b are the distorted octahedra (Fig. 1). Assuming that the chalcogen atom

supplies 6 electrons into the cluster, the total CVE number is 64, which corresponds to a square of metal atoms. These

compounds have different structures due to solvate toluene molecules in the structure of 2a. In 2a, the cluster complex is cut

by a mirror plane passing through the As, Se, and C23 atoms. One of the carbonyl ligands in these clusters is bridged, and the

bond between the iron atoms, to which the bridge ligand is coordinated, is significantly shorter than the other Fe–Fe bonds. It

should be noted that the other Fe–Fe bonds have usual lengths varying in a relatively small range (Fig. 1). In turn, all Fe–Se,

Fe–Te, and Fe–As bonds are significantly shorter than the sum of covalent radii (SCR) (2.52 Å, 2.70 Å, and 2.51 Å

respectively [22]). Since the As–C bond lengths coincide with SCR (1.92 Å [22]) and remain almost the same in all these

clusters, the shortening of the Fe–As and Fe–Q bonds is probably explained by the back donation of iron lone pairs with

unoccupied d orbitals of heavy non-transition elements, which was suggested in [23].

In the structure of 2a, a pseudo-chain staggered arrangement of the molecular moieties along the c axis is observed.

These chain ribbons have a primitive squared packing in the perpendicular direction. In the curved channels of ribbon

packing, the disordered toluene molecules are located (Fig. 2a). The asymmetric part of the structure of 2b contains a whole

cluster molecule. In the structure, a pseudo-layer packing of cluster particles parallel to the [101] plane family can be isolated.

The molecules within a pseudo-layer have a distorted hexagonal packing. The centers of cluster particles have two-layer

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Fig. 1. Structure of clusters 2a,b. Hydrogen atoms are not shown. Main bond lengths (Å) for 2a: Fe1–Fe1′ 2.7458(7), Fe1–Fe2 2.6784(5), Fe2–Fe2′ 2.5173(6), Se–Fe1 2.4021(5), Se–Fe2 2.4666(4), As–Fe1 2.3477(4), As–Fe2 2.3847(4), Fe2–C23 1.943(3), As–C1 1.925(4); for 2b: Fe1–Fe2 2.7978(4), Fe2–Fe3 2.7395(4), Fe3–Fe4 2.7196(4), Fe4–Fe1 2.5066(4), Te1–Fe1 2.6238(3), Te1–Fe2 2.5850(3), Te1–Fe3 2.5785(3), Te1–Fe4 2.6605(3), As–Fe1 2.3660(3), As–Fe2 2.3272(3), As–Fe3 2.3446(3), As–Fe4 2.3706(3), As–C1 1.9423(18), Fe1–C43 1.9287(19), Fe4–C43 1.9395(18).

Fig. 2. Staggered ribbon of clusters in the structure of 2a (a), hexagonal layer in the [101] plane in the structure of 2b (b).

packing with a 1/4(c–a) shift (Fig. 2b). In the IR spectra of the solutions of these compounds in methylene chloride, the

signals typical of bridge CO groups are observed. The PMR spectroscopic and the elemental analysis data correspond to the

structure and composition of the obtained compounds.

Thus, in the present work new cluster [Fe4(μ4-Q)(μ4-AsMe)(CO)11] complexes were produced; their structure was

determined by X-ray diffraction and confirmed by a set of physicochemical methods. It is found that, in contrast to similar

phosphorus-containing clusters, these compounds are unstable in the solution and decompose with the formation of [Fe3(μ3-

Q)(μ3-AsMe)(CO)9].

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The work was supported by RFBR (Projects Nos. 10-03-00385-a, 12-03-31759, and 12-03-31530) and the Federal

Targeted Program “Scientific and Scientific Pedagogical Personnel of Innovative Russia,” contract No. 8631, registration

No. 1012-1.3.1-12-000-1012-009.

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