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Reactivity of 1,2,3-triselena[3]ferrocenophane towards transition metal carbonyls
Journal of Organometallic Chemistry 794 (2015) 266e273
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Reactivity of 1,2,3-triselena[3]ferrocenophane towards transition metal carbonyls Pradeep Mathur a, b, *, Abhinav Raghuvanshi b, Shaikh M. Mobin a a b
School of Basic Sciences, Indian Institute of Technology Indore, Khandwa Road, Simrol, Indore 452020, India Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
a r t i c l e i n f o
a b s t r a c t
Article history: Received 24 March 2015 Received in revised form 28 June 2015 Accepted 2 July 2015 Available online 14 July 2015
Reactions of 1,2,3-triselena[3]ferrocenophane with [Mn2(CO)10], [Fe(CO)5] and [Os3(CO)12] have been investigated under photolytic or thermolytic conditions. Clusters with contrasting structures have been isolated from these reactions: [{Fe(h-C5H4Se)2Mn(CO)3}2] (1), [Fe(h-C5H4Se)2Fe2(CO)6] (2), [Fe(hC5H4Se)2Os3(CO)10] (3), [Fe(h-C5H4Se)2(m2-Se)Os2(CO)6] (4) and [Fe(h-C5H4Se)2(m3-Se)Os4(CO)11] (5). Formally, these new clusters are formed by substitution of the central selenium of 1,2,3-triselena[3] ferrocenophane by metal carbonyl units, as in 1e3 or insertion of two Os(CO)3 groups or an Os4(CO)11 unit into the SeeSe bond as in 4 and 5, respectively. © 2015 Elsevier B.V. All rights reserved.
Keywords: 1,2,3-triselena[3]ferrocenophane Cluster Metal chalcogenide Manganese carbonyl Osmium carbonyl Molecular structure
1. Introduction Chemistry of polynuclear transition metal chalcogenide clusters has drawn considerable attention, not only because of their fundamental significance as a class of clusters with specific chemical and structural properties, but also because of their potential applications in the preparation of nanomaterials, catalysts and semiconducting materials [1e14]. The role of chalcogenide ligand is important as it stabilizes the metal clusters and helps in cluster growth reactions. Because of the functionality of the side arm of [n] ferrocenophanes (n 3), various oxa- and aza-ferrocenophanes have been found to be good electrochemical sensors for cations or anions [15e20]. Since the first report of 1,2,3-trithia[3]ferrocenophane, Fe(C5H4)S3, by Davison and Smart in 1969 [21], a series of [3]ferrocenophanes with trichalcogen chains, -Se3-, -SSeS-, -STeS-, -SeSSe-, -SeTeSe-, -Te3- as bridging groups have been synthesized [22e30]. Reactivity of 1,2,3-trithia[3]ferrocenophane has been quite well explored, while investigations on 1,2,3-triselena[3]ferrocenophane are somewhat limited [31e35], a summary of its
* Corresponding author. Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India. E-mail address: [email protected] (P. Mathur). http://dx.doi.org/10.1016/j.jorganchem.2015.07.005 0022-328X/© 2015 Elsevier B.V. All rights reserved.
reactivity features is given in Scheme 1. 1,2,3-triselena[3]ferrocenophane has been used to synthesise some transition metal inserted complexes (Scheme 1(a) and (b)) [33,34] as well as few macrocyclic polyselenaferrocenophanes (Scheme 1(c)) [35]. Complexes [Fe2(CO)6(m-EE0 )] (E, E0 ¼ S, Se, Te) have been used extensively for cluster growth reactions, and a large number of mixed metal clusters have been obtained by virtue of a formal addition of metal units across the EeE0 bonds of [Fe2(CO)6(m-EE0 )] (Scheme 2, only for E, E0 ¼ Se) [36e41]. Similarity of these products with those arising from reactions of the 1,2,3-triselena[3]ferrocenophane, depicted in Scheme 1, highlights the role of the selenium atoms as bridges to the adding metal units. Formal replacement of the central selenium atom of 1,2,3-triselena[3]ferrocenophane by various inorganic and organic units suggests that the 1,2,3-triselena [3]ferrocenophane compounds may serve as useful synthon for selenium-bridged mixed metal clusters. Although the synthesis of mixed metal clusters by using [Fe2(CO)6Se2] has been quite successful in providing clusters of a large number of metal combinations, those with manganese and osmium containing selenium bridges remains limited. Here, we report on the reaction of 1,2,3-triselena[3]ferrocenophane with [Mn2(CO)10] and [Os3(CO)12] to give novel, mixed Se-bridged Mn and Os containing clusters. A facile reaction with Fe(CO)5 is also reported.
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Scheme 1. Reactions of 1,2,3-triselena[3]ferrocenophane.
2. Results and discussion Photochemical reaction of a THF solution of 1,2,3-triselena[3] ferrocenophane with dimanganese decacarbonyl affords a green compound, which is stable in solid state. Based on spectroscopic characterisation and its molecular structure determination by single crystal X-ray diffraction, it is identified as a novel mixed metal cluster [(Fe(h-C5H4Se)2Mn(CO)3)2] (1) (Scheme 3). The IR spectrum shows carbonyl stretching vibrational frequencies corresponding to terminal metal carbonyls. 1H NMR spectrum of 1 consists of two peaks at d 4.44 ppm and d 4.73 ppm, corresponding to protons of the Cp rings. Single crystals of 1 were grown from hexane/dichloromethane solvent mixture and for unambiguous molecular structure determination, a single crystal x-ray diffraction investigation was undertaken. Molecular structure of compound 1 is depicted in Fig. 1. The structure of 1, may be seen to derive by a formal replacement of the central selenium atom of 1,2,3-triselena[3]ferrocenophane by a Mn(CO)3 unit, and then a coupling of two such units involving new MneSe and SeeSe bond formations to overall give a core consisting of a distorted Mn2Se2 square and a Se2 unit bridging the diagonally located Mn atoms. The SeeSe bond distance in 1 (Se(1)-Se(4) ¼ 2.4208(8) Å) is longer than those found in previously reported MneSe systems,
[Se6Mn6(CO)18]4 (2.394(1) Å) [42], [Se10Mn6(CO)18]4 (2.37(2) Å) [42], [Se5Mn4(CO)12]2 (2.38(1) Å) [42], [Se4Mn3(CO)10] (2.3588(5) Å) [42], [Se8C2Mn2(CO)6]2 (2.357(2) Å) [43], [Se4Mn2(CO)6]2 (2.327(3) Å) [44], [Se8Mn2(CO)6]2 (2.364(3) Å) [44] and [Se2Mn2(CO)5(PPh3)2] (2.311(2) Å) [45]. Two Mn atoms are separated by 3.725 Å which is clearly a nonbonding distance. Both Mn centres are coordinated to three Se atoms and three terminal carbonyl groups in a distorted octahedral geometry. Since there are two different types of Se atoms present, two different MneSe bond distanes are observed. MneSe average bond distance for Se(2) and Se(3), which are bridging two Mn atoms, is 2.51 Å, whereas, MneSe average bond distance for Se(1) and Se(4), which are bridging a Mn and a Se atom, is 2.44 Å. Assuming the diselenide ligand in 1 to be a 10-electron donor, each metal atom achieves an 18-electron configuration. Distorted square M2E2 is an important structural core and many mixed-metal cluster geometries have evolved around this core, e.g. octahedral, square pyramidal, picnic basket and several others [46,47]. Examples where only two of the four core atoms of the basic square core units are involved in cluster formation are very limited. Bicyclic cage like structures, similar to 1 have been observed in a SneSe system in tetraselenadistannabicyclo[2,1,1] hexane [48] and two MneS systems, [Mn2(CO)6(m-h4-SC6H3(CH3)SSC6H3(CH3)S)] [49] and [(Mn(CO)3)2(m-SC6H4-o-S-S-C6H4-o-m-S-)]
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Scheme 2. [Fe2(CO)6(m-Se2)] in cluster growth reactions.
Scheme 3. Reaction of 1,2,3-triselena[3]ferrocenophane with metal carbonyls.
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Fig. 1. (a) Molecular structure of 1. (b) Core structure of 1. Selected bond lengths (Å) and bond angles (deg): Mn(1)eSe(1) ¼ 2.4230(10), Mn(1)eSe(2) ¼ 2.5108(10), Mn(1)e Se(3) ¼ 2.5227(10), Mn(2)eSe(4) ¼ 2.4313(11), Mn(2)eSe(2) ¼ 2.5077(10), Mn(2)eSe(3) ¼ 2.5086(11), Se(1)eSe(4) ¼ 2.4208(8), Se(1)eC(1) ¼ 1.910(5), Se(2)eC(6) ¼ 1.923(5), Se(3)eC(17) ¼ 1.925(5), Se(4)eC(22) ¼ 1.924(5) and Se(1)eMn(1)eSe(2) ¼ 92.17(3), Se(2)eMn(1)eSe(3) ¼ 78.19(3), Se(4)eSe(1)eMn(1) ¼ 105.23(3), Mn(2)eSe(2)e Mn(1) ¼ 95.87(3), Mn(2)eSe(3)eMn(1) ¼ 95.55(3), Se(1)eSe(4)eMn(2) ¼ 105.92(3), Se(2)eMn(2)eSe(3) ¼ 78.51(3).
[50]. Cluster 1 may be considered as an example of a new category where Se atoms of the square unit are connected to the bridging Se2 units via a ferrocenyl group. When a hexane solution of 1,2,3-triselena[3]ferrocenophane was photolysed with iron pentacarbonyl under inert atmosphere, formation of a new ferrocene-bridged Fe2Se2 cluster, [Fe(hC5H4Se)2Fe2(CO)6] (2) was observed (Scheme 3). The compound was found to be stable in solid state but decomposes slowly in solution. The 1H NMR spectrum of 2 consists of two peaks at d 4.13 and 4.32 ppm, corresponding to the protons of Cp rings. The infrared spectrum of 2 shows CO stretching pattern in the range 2068e1991 cm1, indicating the presence of terminal carbonyls. Suitable single crystals of 2 were grown from hexane/dichloromethane solvent mixture and the structure was established crystallographically. The molecular structure of compound 2, shown in Fig. 2, consists of a butterfly [Fe2(CO)6Se2] unit with ferrocene unit added across the open butterfly edge. Structure of 2 is similar to the sulphur analogue reported by Seyferth and Hames [51]. The
Fig. 2. Molecular structure of compound 2. Selected bond lengths (Å) and bond angles (deg): Se(1)eFe(2) ¼ 2.3804(4), Se(1)eFe(1) ¼ 2.3820(5), Se(2)eFe(1) ¼ 2.3834(4), Se(2)eFe(2) ¼ 2.3861(5), Fe(1)eFe(2) ¼ 2.5508(5), Se(1)eC(7) ¼ 1.907(3), Se(2)e C(12) ¼ 1.903(3) and Fe(2)eSe(1)eFe(1) ¼ 64.770(15), Fe(1)eSe(2)e Fe(2) ¼ 64.662(14), Se(1)eFe(1)eSe(2) ¼ 90.156(15), Se(1)eFe(2)eSe(2) ¼ 90.129(15).
compound is formed by addition of Fe2(CO)6 across the Se side arm of 1,2,3-triselena[3]ferrocenophane with the loss of central Se atom. Average FeeSe bond distance in 2 is 2.38 Å and average FeeSeeFe bond angle is 64.70 , both in the normal range. Average SeeFeeSe bond angle of 90.1 is larger to the systems where alkyne unit is attached to butterfly edge [52e54], but is much larger than the average SeeFeeSe bond angle of 58 in the closed tetrahedron of [(CO)6Fe2(m-Se2)] [55]. This widening of bond angle is to accommodate the ferrocene unit on the Fe2Se2 butterfly core. When a toluene solution of 1,2,3-triselena[3]ferrocenophane was refluxed with triosmium dodecacarbonyl, formation of three new compounds was observed which were identified as [Fe(hC5H4Se)2Os3(CO)10] (3), [Fe(h-C5H4Se)2(m2-Se)Os2(CO)6] (4) and [Fe(h-C5H4Se)2(m3-Se)Os4(CO)11] (5) (Scheme 3). The yield of compounds 3 and 5 was very less compared to 4. The infrared spectrum of all three compounds shows CO stretching pattern, indicating the presence of terminal carbonyls. Suitable single crystals of 3, 4 and 5 were grown from hexane/dichloromethane solvent mixture and the molecular structures were established by single crystal X-ray crystallographic analysis. The data for compounds were collected at room temperature which leads to slightly higher thermal values for metal ions particularly for the Os atoms in compound 3. Molecular structures of compounds 3 and 4 are shown in Figs. 3 and 4, respectively. Molecular structure of 3 consists of a Os3Se2 core, whereas 4 consists of a Os2Se3 core. 3 differ by 4 by having a Se atom in place of Os(CO)4 unit. Each selenium atom of the ferrocenediselenolate ligand bridges the two osmium atoms and form a butterfly type structure, where Cp rings of the ferrocene is attached to the Se-wingtips, in both compounds. Further, in 3 both osmium atoms are bridged by another Os atom and in 4 they are bridged by a selenido ligand. OseOs distances in 3 (Os(1)eOs(3) ¼ 2.9067(4) Å, Os(2)eOs(3) ¼ 2.9103(5) Å) agree with metalemetal bonding. There is no significant change in the structural parameters when Os(CO)4 unit is replaced by Se atom as non-bonded OseOs bond distances are 3.466 Å and 3.439 Å, in 3 and 4, respectively and average OseSe and SeeC bond distances remain almost same (Table 1). Also, there is not much difference in OseSeeOs bond angle and dihedral angle between the Os2Se planes in molecular structures of 3 and 4. In both compounds geometry around each Os atom is distorted octahedral and each Os atom is 18 electron
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Fig. 3. Molecular structure of compound 3. Selected bond lengths (Å) and bond angles (deg): Os(1)eOs(3) ¼ 2.9067(4), Os(2)eOs(3) ¼ 2.9103(5), Se(1)eOs(1) ¼ 2.5851(8), Se(1)eOs(2) ¼ 2.5773(8), Se(2)eOs(2) ¼ 2.5762(9), Se(2)eOs(1) ¼ 2.5785(9), Se(1)e C(6) ¼ 1.918(8), Se(2)eC(1) ¼ 1.913(9); Os(2)eSe(1)eOs(1) ¼ 84.35(2), Os(2)eSe(2)e Os(1) ¼ 84.50(3), Os(1)eOs(3)eOs(2) ¼ 73.144(12).
Fig. 4. Molecular structure of compound 4. Selected bond lengths (Å) and bond angles (deg): Os(1)eSe(3) ¼ 2.5631(14), Os(1)eSe(1) ¼ 2.5850(15), Os(1)eSe(2) ¼ 2.5879(14), Os(2)eSe(3) ¼ 2.5568(14), Os(2)eSe(1) ¼ 2.5706(15), Os(2)eSe(2) ¼ 2.5858(15), Se(1)eC(1) ¼ 1.927(14), Se(2)eC(6) ¼ 1.908(13) and Os(2)eSe(3)eOs(1) ¼ 84.33(4), Os(2)eSe(1)eOs(1) ¼ 83.61(4), Os(2)eSe(2)eOs(1) ¼ 83.25(4).
satisfied. Compound 3 has 50 cluster valence electron. Molecular structure of compound 5 is presented in Fig. 5. The compound consists of four Os atoms arranged in a spiked triangular fashion. The osmium triangle is triply bridged by a selenido ligand. Each selenium atom of the ferrocenediselenolate ligand bridges the two osmium atoms, Os(1) and Os(2), and form a butterfly type structure. The triangle formed by Os is not equilateral Os(2)eOs(3) ¼ 2.8592(8) Å, Os(2)eOs(4) ¼ 2.8651(8) Å, Os(3)eOs(4) ¼ 2.7390(9) Å). Despite having partially semibridging carbonyls between Os(2) and the other two osmiums (Os(3) and Os(4)), the Os(2)eOs(3) and Os(2)eOs(4) bond distances are larger than Os(3)eOs(4). The OseSe distances in selenido bridged Os-triangle, Os(2)eSe(3) ¼ 2.5005(14), Os(3)eSe(3) ¼ 2.4697(15), Os(4)eSe(3) ¼ 2.4723(16), shows closer interaction of Se(3) with
Table 1 Comparison of selected bond lengths and bond angles in compounds 3, 4 and 5. Compound
3
4
5
Average OseOs bond length Average OseSe bond length Average SeeC bond length Average OseSeeOs bond angle Dihedral angle between Os2Se planes
2.9085 Å 2.5792 Å 1.9155 Å 84.425 55.02
e 2.5752 Å 1.9175 Å 83.73 55.81
2.8021 Å 2.5102 Å 1.915 Å 67.842 68.77
Os(3) and Os(4). The triply bridging selenide shortens the OseOs bond (average 2.802 Å), relative to the value found in parent carbonyl, [Os3(CO)12] (average 2.877 Å). The SeeOs distances are almost similar (Os(1)eSe(1) ¼ 2.5147(17) Å, Os(1)e Se(2) ¼ 2.5286(14) Å, Os(2)eSe(1) ¼ 2.5401(16) Å, Os(2)e Se(2) ¼ 2.5447(15) Å) and are shorter than those found in 3 and 4 (Table 1). Average OseSeeOs bond angle in 5 is 67.842 and is considerably shorter than that found in compound 3 (84.425 ) and 4 (83.73 ). The dihedral angle formed between the Os2Se planes of butterfly unit is 68.77 which was found to be significantly higher than those observed in 3 (55.02 ) and 4 (55.84 ), also the same angle between the Fe2Se planes in compound 2 is even smaller (50.52 ). Because of higher dihedral angle nonbonded Se(1)eSe(2) distance in 5 is considerably higher (3.521 Å) than in compound 2, 3 and 4, where it is approximately 3.4 Å. Longer distance between the selenium atoms in 5 is because of steric reasons, which is created by the close proximity of bulkier Os atoms. Compound 5 has 64 cluster valence electrons, which is consistent with the spiked triangular skeleton with four MeM bonds [56]. It is found that three selenium atoms donates 10 electron to the cluster core in compound 5, whereas, same number of selenium donates 8 electron in compound 4 to satisfy the electron count around each metal atom. In all five complexes the two cyclopentadienyl rings are tilted towards each other towards the complex formation side. The angle between the two Cp planes are 2.62 , 5.58 , 2.45 , 4.54 and 3.90 in compounds 1, 2, 3, 4 and 5, respectively. The Cp rings exhibit an eclipsed conformation and are virtually planer, while the selenium atoms attached to each ring are displaced outward from the Cp ring planes probably to bring down the steric strain. In all five complexes, there is no significant change in the CeSe average bond distance (1.9 Å) of ferrocenediselenolate ligand after complexation. 3. Conclusion Use of 1,2,3-triselena[3]ferrocenophane as a useful synthon for selenium-bridged mixed-metal clusters has been demonstrated. Its reaction with Mn2(CO)10 and Fe(CO)5 to form ferrocenyl incorporated clusters under facile photolytic conditions is significant. Similarly, formation of some novel selenium-bridged osmium clusters, under thermolytic conditions highlights the potential of using the 1,2,3-triselena[3]ferrocenophane in novel cluster preparation. 4. Experimental details 4.1. General procedures All reactions and manipulations were performed under an inert atmosphere of pre-purified nitrogen or argon. Solvents were purified, dried and distilled under argon or nitrogen atmosphere prior to use. Infrared spectra were recorded on Perkin Elmer FTIR spectrometer. NMR spectra were recorded on Bruker AVANCE III/400 spectrometer with TMS as internal standard. Elemental analyses were carried out with a Flash 2000 elemental analyser. 1,2,3triselena[3]ferrocenophane has been synthesised by reported procedure [57]. Metal carbonyls were purchased from Fluka and SigmaeAldrich. Photochemical reactions were carried out in a water cooled double-walled quartz vessel having a 125 W mercury lamp manufactured by SAIC, India. Medium pressure mercury lamp has been used for the experiments which radiate predominantly 365e366 nm light. TLC plates were purchased from Merck (20 20 cm, silica gel 60 F254).
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Fig. 5. (a) Molecular structure of compound 5.(b) Core structure of 5. Selected bond lengths (Å) and bond angles (deg): Os(1)eSe(1) ¼ 2.5147(17), Os(1)eSe(2) ¼ 2.5286(14), Os(1)e Os(2) ¼ 2.7451(8), Os(2)eSe(1) ¼ 2.5401(16), Os(2)eSe(2) ¼ 2.5447(15), Os(2)eOs(3) ¼ 2.8592(8), Os(2)eOs(4) ¼ 2.8651(8), Os(3)eOs(4) ¼ 2.7390(9), Os(2)eSe(3) ¼ 2.5005(14), Os(3)eSe(3) ¼ 2.4697(15), Os(4)eSe(3) ¼ 2.4723(16), Se(1)eC(12) ¼ 1.910(17), Se(2)eC(17) ¼ 1.920(16); Os(1)eSe(1)eOs(2) ¼ 65.78(4), Os(1)eSe(2)eOs(2) ¼ 65.52(4), Os(3)e Se(3)eOs(4) ¼ 67.32(4), Os(3)eSe(3)eOs(2) ¼ 70.23(4), ¼ Os(4)eSe(3)eOs(2) ¼ 70.36(4), O(4)eC(4)eOs(2) ¼ 167.2(15), O(5)eC(5)eOs(2) ¼ 168.0(14), Se(1)eOs(1)e Se(2) ¼ 88.26(5), Se(1)eOs(2)eSe(2) ¼ 87.36(5).
4.2. Reaction of 1,2,3-triselena[3]ferrocenophane with Mn2(CO)10 To a THF solution of 1,2,3-triselena[3]ferrocenophane (42 mg, 0.1 mmol) [Mn2(CO)10] (78 mg, 0.2 mmol) was added and the mixture was photolysed at 20 C for 30 min under a nitrogen atmosphere. The solvent was removed under reduced pressure, and the residue was subjected to a chromatographic workup on silica gel TLC plates. Elution with dichloromethane/hexane solvent mixture yielded 5.5 mg (6%) of compound 1 as green band along with a red product that does not move on TLC plate. IR (nCO in hexane): 2027 cm1, 2008 cm1 and 1950 cm1 indicate the presence of terminal carbonyls. 1H NMR (d, CDCl3): 4.44 and 4.73 ppm (Cp protons). Elemental analyses: Found (%): C 31.11, H 1.81; Calcd for C26H16Fe2Mn2O6Se4.CH2Cl2: C 30.98, H 1.73.
(Yield ¼ 21 mg, 22%), yellow coloured compound 3 (Yield ¼ 2 mg, 2%) and orange coloured compound 5 (Yield ¼ 6 mg, 4%). Compound 3: IR (nCO in hexane): 2097 cm1, 2057 cm1, 2000 cm1 and 1968 cm1 suggest the presence of terminal carbonyls. Elemental analyses: Found (%): C 19.96, H 0.85; Calcd for C20H8FeO10Os3Se2.H2O: C 19.84, H 0.83. Compound 4: IR (nCO in hexane): 2081 cm1, 2000 cm1, 1941 cm1 indicate the presence of terminal carbonyls. 1H NMR (d, CDCl3):4.30 and 4.57 ppm (Cp protons). 77SeNMR (d, CDCl3): 757.84 and 459.47 ppm. Elemental analyses: Found (%): C 19.91, H 0.87; Calcd for C16H8FeO6Os2Se3: C 19.82, H 0.83. Compound 5: IR (nCO in hexane): 2068 cm1, 2028 cm1, 1992 cm1, 1972 cm1 and 1913 cm1 indicate the presence of terminal carbonyls. Elemental analyses: Found (%): C 16.82, H 0.62 Calcd for C21H8FeO11Os4Se3: C 16.93, H 0.54.
4.3. Reaction of 1,2,3-triselena[3]ferrocenophane with Fe(CO)5 4.5. Crystal structure determination of compound 1-5 To a hexane solution of 1,2,3-triselena[3]ferrocenophane (42 mg, 0.1 mmol) Fe(CO)5 (0.27 ml, 0.2 mmol) was added and the mixture was photolysed at 0 C for 30 min under a nitrogen atmosphere. The solvent was removed under reduced pressure, and the residue was subjected to a chromatographic workup on silica gel TLC plates by using hexane solvent as eluent, which afforded 13 mg (21%) of brown band as compound 2 along with [Fe3(CO)9(m3-Se)2]. IR (nCO in hexane): 2068 cm1, 2032 cm1, 2001, 1991 cm1 indicate the presence of terminal carbonyls. 1H NMR (d, CDCl3): 4.13 and 4.32 ppm (Cp protons), 13C NMR (d, CDCl3):70.1, 75.2, 83.7, 208.8 ppm, 77Se NMR (d, CDCl3): 218.3 ppm. Elemental analyses: Found (%): C 31.07, H 1.35; Calcd for C16H8Fe3O6Se2: C 30.91, H 1.29. 4.4. Reaction of 1,2,3-triselena[3]ferrocenophane with [Os3(CO)12] To a toluene solution of 1,2,3-triselena[3]ferrocenophane (42 mg, 0.1 mmol) [Os3(CO)12] (181 mg, 0.2 mmol) was added and the mixture was refluxed for 6 h. The solvent was removed under reduced pressure, and the residue was subjected to a chromatographic workup on silica gel TLC plates by using dichloromethane/ hexane solvent mixtures as eluent. First yellow band was unreacted osmium carbonyl, next bands were yellow coloured compound 4
Relevant crystallographic data and structure refinement details are listed in Table 2. Suitable X-ray quality crystals of compounds 1, 2, 3, 4 and 5 were grown by slow evaporation of n-hexane and dichloromethane solution at 0 oC-5 oC. A CCD technology Supernova diffractometer was used for the cell determination and intensity data collection. Monochromatic Cu (l ¼ 1.5418 Å)/Mo Ka radiation (l ¼ 0.71073 Å) were used for the measurements. The strategy for the data collection was evaluated by using the CrysAlis Pro CCD software. The data were collected by the standard ‘phiomega’ scan techniques, and were scaled and reduced using CrysAlis Pro RED software. Absorption corrections using multi j-scans were applied. The data for compound 3 was collected at room temperature which leads to slightly higher thermal values for metal ions particularly for the Os atoms. For 1 and 5 SQUEEZE was applied to disordered DCM solvent molecules and the calculated numbers of squeezed electrons are 72 for 1 and 64 electrons for 5. The structures were solved by direct methods (SHELXS) and refined by full matrix least squares against F2 using SHELXL-97 software [58]. Non-hydrogen atoms were refined with anisotropic thermal parameters. All hydrogen atoms were geometrically fixed and allowed to refine using a riding model.
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Table 2 Crystal data and structure refinement parameters for compounds 1, 2, 3, 4 and 5. Compound
1
Empirical formula Formula wt. Crystal system Space group a (Å) b (Å) c (Å) a (deg) b (deg) g (deg) Volume, (Å3) Z Dcalcd, Mg/m3 Abs coeff, mm1 F(000) Crystal size, mm q range, deg Index ranges
C104H64Fe8Mn8O24Se16 3847.23 Monoclinic P 21/c 13.5958(3) 19.2314(4) 23.2339(6) 90 103.756(3) 90 5900.6(2) 2 2.165 20.523 3664 0.29 0.20 0.13 3.02e72.51 deg. 16 h 10, 23 k 23, 23 l 28 Reflections collected/unique 45776/11556 [R(int) ¼ 0.0459] Completeness to q 98.8% Data/restraints/parameters 11556/0/721 Goodness of fit on F2 1.060 Final R indices [I > 2s(I)] R1 ¼ 0.0418, wR2 ¼ 0.1060 R indices (all data) R1 ¼ 0.0531, wR2 ¼ 0.1132 Largest diff. peak and hole, 1.540 and 1.261 e Å3
2
3
4
5
C8H4Fe1.50O3Se 310.85 Monoclinic P 21/n 7.6080(2) 13.7179(3) 18.2822(4) 90 96.639(2) 90 1895.24(8) 8 2.179 6.136 1192 0.33 0.22 0.16 2.97 to 25.00 9h 9, 16 k 15, 21 l 1 14987/3335 [R(int) ¼ 0.0236] 99.9% 3335/0/244 1.030 R1 ¼ 0.0200, wR2 ¼ 0.0462 R1 ¼ 0.0241, wR2 ¼ 0.0483 0.509 and 0.303
C80H32Fe4O40Os12Se8 4770.54 Orthorhombic Pbca 18.2769(3) 13.3537(3) 20.3340(5) 90 90 90 4962.80(18) 2 3.192 18.872 4240 0.31 0.25 0.16 3.00 to 25.00 14 h 21, 15 k 15, 24 l 24 41627/4354 [R(int) ¼ 0.1683] 99.8% 4354/8/326 1.083 R1 ¼ 0.0469, wR2 ¼ 0.1170 R1 ¼ 0.0492, wR2 ¼ 0.1201 2.224 and 5.364
C16H8FeO6Os2Se3 969.35 Orthorhombic P n a 21 24.3439(4) 11.5778(2) 7.05070(10) 90 90 90 1987.23(6) 4 3.240 35.983 1728 0.34 0.26 0.23 3.63 to 72.05 29 h 29, 8k 14, 8l 8 12402/3864 [R(int) ¼ 0.0685] 99.8% 3864/1/249 1.045 R1 ¼ 0.0512, wR2 ¼ 0.1345 R1 ¼ 0.0517, wR2 ¼ 0.1351 3.255 and 1.841
C42H16Fe2O22Os8Se6 2979.61 Triclinic P -1 12.7554(6) 14.2328(7) 18.5409(8) 104.177(4) 95.968(4) 112.099(4) 2950.8(2) 2 3.353 21.394 2616 0.33 0.26 0.23 3.21 to 25.00 15 h 13, 16 k 16, 22 l 22 23156/10357 [R(int) ¼ 0.0512] 99.7% 10357/0/721 1.040 R1 ¼ 0.0544, wR2 ¼ 0.1357 R1 ¼ 0.0717 wR2 ¼ 0.1471 3.740 and 3.709
Acknowledgements P.M. and A.R. are grateful to the DST, Government of India for financial assistance. Appendix. Supplementary material CCDC nos. 1054484, 1054483, 1054486, 1054485 and 1054482 contain the supplementary crystallographic data for compounds 1, 2, 3, 4 and 5, respectively. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc. cam.ac.uk/products/csd/request. References [1] D.F. Shriver, H.D. Kaesz, R.D. Adams (Eds.), The Chemistry of Metal Cluster Complexes, Wiley-VCH Publishers, New York, 1990. [2] P. Braunstein, L.A. Oro, P.R. Raithby (Eds.), Metal Clusters in Chemistry, WileyVCH Publishers, Weinheim, 1999. [3] R.D. Adams, M. Tasi, J. Clust. Sci. 1 (1990) 249e267. [4] P. Mathur, Adv. Organomet. Chem. 41 (1997) 243e314. [5] M.A. Ansari, J.A. Ibers, Coord. Chem. Rev. 100 (1990) 223e266. [6] M.G. Kanatzidis, S.-P. Huang, Coord. Chem. Rev. 130 (1994) 509e621. [7] H. Ogino, S. Inomata, H. Tobita, Chem. Rev. 98 (1998) 2093e2121. [8] C. Femoni, M.C. Iapalucci, F. Kaswalder, G. Longoni, S. Zacchini, Coord. Chem. Rev. 250 (2006) 1580e1604. [9] M.G. Richmond, Coord. Chem. Rev. 249 (2005) 2763e2786. €fer, I. Issac, D. Fenske, O. Fuhr, P. Sevillano, C. Persau, [10] C.E. Anson, A. Eichho D. Stalke, J. Zhang, Angew. Chem. Int. Ed. 47 (2008) 1326e1331. €fer, D. Fenske, Eur. J. Inorg. Chem. (2002) 279e317. [11] S. Dehnen, A. Eichho [12] J. Xu, K. Jang, J. lee, H.J. Kim, J. Jeong, J.-G. Park, S.U. Son, Cryst. Growth Des. 11 (2011) 2707e2710. [13] C.B. Murray, D.J. Norris, M.G. Bawendi, J. Am. Chem. Soc. 115 (1993) 8706e8715. [14] V.L. Colvin, M.C. Schlamp, A.P. Alivisatos, Nature 370 (1994) 354e357. rraga, P. Molina, Sensors 14 (2014) 14339e14355. [15] A. Sola, A. Espinosa, A. Ta rraga, A. Espinosa, M.D. Velasco, J. Vidal-Gan[16] A. Caballero, V. Lloveras, A. Ta cedo, C. Rovira, K. Wurst, P. Molina, J. Veciana, Angew. Chem. Int. Ed. 44 (2005) 1977e1981.
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[52] P. Mathur, A. Raghuvanshi, R.S. Ji, S.M. Mobin, J. Organomet. Chem. 731 (2013) 55e60. [53] P. Mathur, A.K. Dash, M.M. Hossain, C.V.V. Satyanarayana, A.L. Rheingold, G.P.A. Yap, L.M. Liable-Sands, J. Organomet. Chem. 543 (1997) 135e143. [54] P. Mathur, M.M. Hossain, Organometallics 12 (1993) 2398e2400. [55] C.F. Campana, F. Lo, L.F. Dahl, Inorg. Chem. 18 (1979) 3060e3064. [56] H.G. Ang, L.L. Koh, S.G. Ang, S.Y. Ng, G.Y. Yang, J. Chem. Soc. Dalton Trans. (1996) 4083e4088. [57] A.G. Osborne, R.E. Hollands, J.A.K. Howard, R.F. Bryan, J. Organomet. Chem. 205 (1981) 395e406. [58] G.M. Sheldrick, Acta Crystallogr. A64 (2008) 112e122.
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Reactivity of 1,2,3-triselena[3]ferrocenophane towards transition metal carbonyls Pradeep Mathur a, b, *, Abhinav Raghuvanshi b, Shaikh M. Mobin a a b
School of Basic Sciences, Indian Institute of Technology Indore, Khandwa Road, Simrol, Indore 452020, India Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
a r t i c l e i n f o
a b s t r a c t
Article history: Received 24 March 2015 Received in revised form 28 June 2015 Accepted 2 July 2015 Available online 14 July 2015
Reactions of 1,2,3-triselena[3]ferrocenophane with [Mn2(CO)10], [Fe(CO)5] and [Os3(CO)12] have been investigated under photolytic or thermolytic conditions. Clusters with contrasting structures have been isolated from these reactions: [{Fe(h-C5H4Se)2Mn(CO)3}2] (1), [Fe(h-C5H4Se)2Fe2(CO)6] (2), [Fe(hC5H4Se)2Os3(CO)10] (3), [Fe(h-C5H4Se)2(m2-Se)Os2(CO)6] (4) and [Fe(h-C5H4Se)2(m3-Se)Os4(CO)11] (5). Formally, these new clusters are formed by substitution of the central selenium of 1,2,3-triselena[3] ferrocenophane by metal carbonyl units, as in 1e3 or insertion of two Os(CO)3 groups or an Os4(CO)11 unit into the SeeSe bond as in 4 and 5, respectively. © 2015 Elsevier B.V. All rights reserved.
Keywords: 1,2,3-triselena[3]ferrocenophane Cluster Metal chalcogenide Manganese carbonyl Osmium carbonyl Molecular structure
1. Introduction Chemistry of polynuclear transition metal chalcogenide clusters has drawn considerable attention, not only because of their fundamental significance as a class of clusters with specific chemical and structural properties, but also because of their potential applications in the preparation of nanomaterials, catalysts and semiconducting materials [1e14]. The role of chalcogenide ligand is important as it stabilizes the metal clusters and helps in cluster growth reactions. Because of the functionality of the side arm of [n] ferrocenophanes (n 3), various oxa- and aza-ferrocenophanes have been found to be good electrochemical sensors for cations or anions [15e20]. Since the first report of 1,2,3-trithia[3]ferrocenophane, Fe(C5H4)S3, by Davison and Smart in 1969 [21], a series of [3]ferrocenophanes with trichalcogen chains, -Se3-, -SSeS-, -STeS-, -SeSSe-, -SeTeSe-, -Te3- as bridging groups have been synthesized [22e30]. Reactivity of 1,2,3-trithia[3]ferrocenophane has been quite well explored, while investigations on 1,2,3-triselena[3]ferrocenophane are somewhat limited [31e35], a summary of its
* Corresponding author. Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India. E-mail address: [email protected] (P. Mathur). http://dx.doi.org/10.1016/j.jorganchem.2015.07.005 0022-328X/© 2015 Elsevier B.V. All rights reserved.
reactivity features is given in Scheme 1. 1,2,3-triselena[3]ferrocenophane has been used to synthesise some transition metal inserted complexes (Scheme 1(a) and (b)) [33,34] as well as few macrocyclic polyselenaferrocenophanes (Scheme 1(c)) [35]. Complexes [Fe2(CO)6(m-EE0 )] (E, E0 ¼ S, Se, Te) have been used extensively for cluster growth reactions, and a large number of mixed metal clusters have been obtained by virtue of a formal addition of metal units across the EeE0 bonds of [Fe2(CO)6(m-EE0 )] (Scheme 2, only for E, E0 ¼ Se) [36e41]. Similarity of these products with those arising from reactions of the 1,2,3-triselena[3]ferrocenophane, depicted in Scheme 1, highlights the role of the selenium atoms as bridges to the adding metal units. Formal replacement of the central selenium atom of 1,2,3-triselena[3]ferrocenophane by various inorganic and organic units suggests that the 1,2,3-triselena [3]ferrocenophane compounds may serve as useful synthon for selenium-bridged mixed metal clusters. Although the synthesis of mixed metal clusters by using [Fe2(CO)6Se2] has been quite successful in providing clusters of a large number of metal combinations, those with manganese and osmium containing selenium bridges remains limited. Here, we report on the reaction of 1,2,3-triselena[3]ferrocenophane with [Mn2(CO)10] and [Os3(CO)12] to give novel, mixed Se-bridged Mn and Os containing clusters. A facile reaction with Fe(CO)5 is also reported.
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Scheme 1. Reactions of 1,2,3-triselena[3]ferrocenophane.
2. Results and discussion Photochemical reaction of a THF solution of 1,2,3-triselena[3] ferrocenophane with dimanganese decacarbonyl affords a green compound, which is stable in solid state. Based on spectroscopic characterisation and its molecular structure determination by single crystal X-ray diffraction, it is identified as a novel mixed metal cluster [(Fe(h-C5H4Se)2Mn(CO)3)2] (1) (Scheme 3). The IR spectrum shows carbonyl stretching vibrational frequencies corresponding to terminal metal carbonyls. 1H NMR spectrum of 1 consists of two peaks at d 4.44 ppm and d 4.73 ppm, corresponding to protons of the Cp rings. Single crystals of 1 were grown from hexane/dichloromethane solvent mixture and for unambiguous molecular structure determination, a single crystal x-ray diffraction investigation was undertaken. Molecular structure of compound 1 is depicted in Fig. 1. The structure of 1, may be seen to derive by a formal replacement of the central selenium atom of 1,2,3-triselena[3]ferrocenophane by a Mn(CO)3 unit, and then a coupling of two such units involving new MneSe and SeeSe bond formations to overall give a core consisting of a distorted Mn2Se2 square and a Se2 unit bridging the diagonally located Mn atoms. The SeeSe bond distance in 1 (Se(1)-Se(4) ¼ 2.4208(8) Å) is longer than those found in previously reported MneSe systems,
[Se6Mn6(CO)18]4 (2.394(1) Å) [42], [Se10Mn6(CO)18]4 (2.37(2) Å) [42], [Se5Mn4(CO)12]2 (2.38(1) Å) [42], [Se4Mn3(CO)10] (2.3588(5) Å) [42], [Se8C2Mn2(CO)6]2 (2.357(2) Å) [43], [Se4Mn2(CO)6]2 (2.327(3) Å) [44], [Se8Mn2(CO)6]2 (2.364(3) Å) [44] and [Se2Mn2(CO)5(PPh3)2] (2.311(2) Å) [45]. Two Mn atoms are separated by 3.725 Å which is clearly a nonbonding distance. Both Mn centres are coordinated to three Se atoms and three terminal carbonyl groups in a distorted octahedral geometry. Since there are two different types of Se atoms present, two different MneSe bond distanes are observed. MneSe average bond distance for Se(2) and Se(3), which are bridging two Mn atoms, is 2.51 Å, whereas, MneSe average bond distance for Se(1) and Se(4), which are bridging a Mn and a Se atom, is 2.44 Å. Assuming the diselenide ligand in 1 to be a 10-electron donor, each metal atom achieves an 18-electron configuration. Distorted square M2E2 is an important structural core and many mixed-metal cluster geometries have evolved around this core, e.g. octahedral, square pyramidal, picnic basket and several others [46,47]. Examples where only two of the four core atoms of the basic square core units are involved in cluster formation are very limited. Bicyclic cage like structures, similar to 1 have been observed in a SneSe system in tetraselenadistannabicyclo[2,1,1] hexane [48] and two MneS systems, [Mn2(CO)6(m-h4-SC6H3(CH3)SSC6H3(CH3)S)] [49] and [(Mn(CO)3)2(m-SC6H4-o-S-S-C6H4-o-m-S-)]
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Scheme 2. [Fe2(CO)6(m-Se2)] in cluster growth reactions.
Scheme 3. Reaction of 1,2,3-triselena[3]ferrocenophane with metal carbonyls.
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Fig. 1. (a) Molecular structure of 1. (b) Core structure of 1. Selected bond lengths (Å) and bond angles (deg): Mn(1)eSe(1) ¼ 2.4230(10), Mn(1)eSe(2) ¼ 2.5108(10), Mn(1)e Se(3) ¼ 2.5227(10), Mn(2)eSe(4) ¼ 2.4313(11), Mn(2)eSe(2) ¼ 2.5077(10), Mn(2)eSe(3) ¼ 2.5086(11), Se(1)eSe(4) ¼ 2.4208(8), Se(1)eC(1) ¼ 1.910(5), Se(2)eC(6) ¼ 1.923(5), Se(3)eC(17) ¼ 1.925(5), Se(4)eC(22) ¼ 1.924(5) and Se(1)eMn(1)eSe(2) ¼ 92.17(3), Se(2)eMn(1)eSe(3) ¼ 78.19(3), Se(4)eSe(1)eMn(1) ¼ 105.23(3), Mn(2)eSe(2)e Mn(1) ¼ 95.87(3), Mn(2)eSe(3)eMn(1) ¼ 95.55(3), Se(1)eSe(4)eMn(2) ¼ 105.92(3), Se(2)eMn(2)eSe(3) ¼ 78.51(3).
[50]. Cluster 1 may be considered as an example of a new category where Se atoms of the square unit are connected to the bridging Se2 units via a ferrocenyl group. When a hexane solution of 1,2,3-triselena[3]ferrocenophane was photolysed with iron pentacarbonyl under inert atmosphere, formation of a new ferrocene-bridged Fe2Se2 cluster, [Fe(hC5H4Se)2Fe2(CO)6] (2) was observed (Scheme 3). The compound was found to be stable in solid state but decomposes slowly in solution. The 1H NMR spectrum of 2 consists of two peaks at d 4.13 and 4.32 ppm, corresponding to the protons of Cp rings. The infrared spectrum of 2 shows CO stretching pattern in the range 2068e1991 cm1, indicating the presence of terminal carbonyls. Suitable single crystals of 2 were grown from hexane/dichloromethane solvent mixture and the structure was established crystallographically. The molecular structure of compound 2, shown in Fig. 2, consists of a butterfly [Fe2(CO)6Se2] unit with ferrocene unit added across the open butterfly edge. Structure of 2 is similar to the sulphur analogue reported by Seyferth and Hames [51]. The
Fig. 2. Molecular structure of compound 2. Selected bond lengths (Å) and bond angles (deg): Se(1)eFe(2) ¼ 2.3804(4), Se(1)eFe(1) ¼ 2.3820(5), Se(2)eFe(1) ¼ 2.3834(4), Se(2)eFe(2) ¼ 2.3861(5), Fe(1)eFe(2) ¼ 2.5508(5), Se(1)eC(7) ¼ 1.907(3), Se(2)e C(12) ¼ 1.903(3) and Fe(2)eSe(1)eFe(1) ¼ 64.770(15), Fe(1)eSe(2)e Fe(2) ¼ 64.662(14), Se(1)eFe(1)eSe(2) ¼ 90.156(15), Se(1)eFe(2)eSe(2) ¼ 90.129(15).
compound is formed by addition of Fe2(CO)6 across the Se side arm of 1,2,3-triselena[3]ferrocenophane with the loss of central Se atom. Average FeeSe bond distance in 2 is 2.38 Å and average FeeSeeFe bond angle is 64.70 , both in the normal range. Average SeeFeeSe bond angle of 90.1 is larger to the systems where alkyne unit is attached to butterfly edge [52e54], but is much larger than the average SeeFeeSe bond angle of 58 in the closed tetrahedron of [(CO)6Fe2(m-Se2)] [55]. This widening of bond angle is to accommodate the ferrocene unit on the Fe2Se2 butterfly core. When a toluene solution of 1,2,3-triselena[3]ferrocenophane was refluxed with triosmium dodecacarbonyl, formation of three new compounds was observed which were identified as [Fe(hC5H4Se)2Os3(CO)10] (3), [Fe(h-C5H4Se)2(m2-Se)Os2(CO)6] (4) and [Fe(h-C5H4Se)2(m3-Se)Os4(CO)11] (5) (Scheme 3). The yield of compounds 3 and 5 was very less compared to 4. The infrared spectrum of all three compounds shows CO stretching pattern, indicating the presence of terminal carbonyls. Suitable single crystals of 3, 4 and 5 were grown from hexane/dichloromethane solvent mixture and the molecular structures were established by single crystal X-ray crystallographic analysis. The data for compounds were collected at room temperature which leads to slightly higher thermal values for metal ions particularly for the Os atoms in compound 3. Molecular structures of compounds 3 and 4 are shown in Figs. 3 and 4, respectively. Molecular structure of 3 consists of a Os3Se2 core, whereas 4 consists of a Os2Se3 core. 3 differ by 4 by having a Se atom in place of Os(CO)4 unit. Each selenium atom of the ferrocenediselenolate ligand bridges the two osmium atoms and form a butterfly type structure, where Cp rings of the ferrocene is attached to the Se-wingtips, in both compounds. Further, in 3 both osmium atoms are bridged by another Os atom and in 4 they are bridged by a selenido ligand. OseOs distances in 3 (Os(1)eOs(3) ¼ 2.9067(4) Å, Os(2)eOs(3) ¼ 2.9103(5) Å) agree with metalemetal bonding. There is no significant change in the structural parameters when Os(CO)4 unit is replaced by Se atom as non-bonded OseOs bond distances are 3.466 Å and 3.439 Å, in 3 and 4, respectively and average OseSe and SeeC bond distances remain almost same (Table 1). Also, there is not much difference in OseSeeOs bond angle and dihedral angle between the Os2Se planes in molecular structures of 3 and 4. In both compounds geometry around each Os atom is distorted octahedral and each Os atom is 18 electron
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Fig. 3. Molecular structure of compound 3. Selected bond lengths (Å) and bond angles (deg): Os(1)eOs(3) ¼ 2.9067(4), Os(2)eOs(3) ¼ 2.9103(5), Se(1)eOs(1) ¼ 2.5851(8), Se(1)eOs(2) ¼ 2.5773(8), Se(2)eOs(2) ¼ 2.5762(9), Se(2)eOs(1) ¼ 2.5785(9), Se(1)e C(6) ¼ 1.918(8), Se(2)eC(1) ¼ 1.913(9); Os(2)eSe(1)eOs(1) ¼ 84.35(2), Os(2)eSe(2)e Os(1) ¼ 84.50(3), Os(1)eOs(3)eOs(2) ¼ 73.144(12).
Fig. 4. Molecular structure of compound 4. Selected bond lengths (Å) and bond angles (deg): Os(1)eSe(3) ¼ 2.5631(14), Os(1)eSe(1) ¼ 2.5850(15), Os(1)eSe(2) ¼ 2.5879(14), Os(2)eSe(3) ¼ 2.5568(14), Os(2)eSe(1) ¼ 2.5706(15), Os(2)eSe(2) ¼ 2.5858(15), Se(1)eC(1) ¼ 1.927(14), Se(2)eC(6) ¼ 1.908(13) and Os(2)eSe(3)eOs(1) ¼ 84.33(4), Os(2)eSe(1)eOs(1) ¼ 83.61(4), Os(2)eSe(2)eOs(1) ¼ 83.25(4).
satisfied. Compound 3 has 50 cluster valence electron. Molecular structure of compound 5 is presented in Fig. 5. The compound consists of four Os atoms arranged in a spiked triangular fashion. The osmium triangle is triply bridged by a selenido ligand. Each selenium atom of the ferrocenediselenolate ligand bridges the two osmium atoms, Os(1) and Os(2), and form a butterfly type structure. The triangle formed by Os is not equilateral Os(2)eOs(3) ¼ 2.8592(8) Å, Os(2)eOs(4) ¼ 2.8651(8) Å, Os(3)eOs(4) ¼ 2.7390(9) Å). Despite having partially semibridging carbonyls between Os(2) and the other two osmiums (Os(3) and Os(4)), the Os(2)eOs(3) and Os(2)eOs(4) bond distances are larger than Os(3)eOs(4). The OseSe distances in selenido bridged Os-triangle, Os(2)eSe(3) ¼ 2.5005(14), Os(3)eSe(3) ¼ 2.4697(15), Os(4)eSe(3) ¼ 2.4723(16), shows closer interaction of Se(3) with
Table 1 Comparison of selected bond lengths and bond angles in compounds 3, 4 and 5. Compound
3
4
5
Average OseOs bond length Average OseSe bond length Average SeeC bond length Average OseSeeOs bond angle Dihedral angle between Os2Se planes
2.9085 Å 2.5792 Å 1.9155 Å 84.425 55.02
e 2.5752 Å 1.9175 Å 83.73 55.81
2.8021 Å 2.5102 Å 1.915 Å 67.842 68.77
Os(3) and Os(4). The triply bridging selenide shortens the OseOs bond (average 2.802 Å), relative to the value found in parent carbonyl, [Os3(CO)12] (average 2.877 Å). The SeeOs distances are almost similar (Os(1)eSe(1) ¼ 2.5147(17) Å, Os(1)e Se(2) ¼ 2.5286(14) Å, Os(2)eSe(1) ¼ 2.5401(16) Å, Os(2)e Se(2) ¼ 2.5447(15) Å) and are shorter than those found in 3 and 4 (Table 1). Average OseSeeOs bond angle in 5 is 67.842 and is considerably shorter than that found in compound 3 (84.425 ) and 4 (83.73 ). The dihedral angle formed between the Os2Se planes of butterfly unit is 68.77 which was found to be significantly higher than those observed in 3 (55.02 ) and 4 (55.84 ), also the same angle between the Fe2Se planes in compound 2 is even smaller (50.52 ). Because of higher dihedral angle nonbonded Se(1)eSe(2) distance in 5 is considerably higher (3.521 Å) than in compound 2, 3 and 4, where it is approximately 3.4 Å. Longer distance between the selenium atoms in 5 is because of steric reasons, which is created by the close proximity of bulkier Os atoms. Compound 5 has 64 cluster valence electrons, which is consistent with the spiked triangular skeleton with four MeM bonds [56]. It is found that three selenium atoms donates 10 electron to the cluster core in compound 5, whereas, same number of selenium donates 8 electron in compound 4 to satisfy the electron count around each metal atom. In all five complexes the two cyclopentadienyl rings are tilted towards each other towards the complex formation side. The angle between the two Cp planes are 2.62 , 5.58 , 2.45 , 4.54 and 3.90 in compounds 1, 2, 3, 4 and 5, respectively. The Cp rings exhibit an eclipsed conformation and are virtually planer, while the selenium atoms attached to each ring are displaced outward from the Cp ring planes probably to bring down the steric strain. In all five complexes, there is no significant change in the CeSe average bond distance (1.9 Å) of ferrocenediselenolate ligand after complexation. 3. Conclusion Use of 1,2,3-triselena[3]ferrocenophane as a useful synthon for selenium-bridged mixed-metal clusters has been demonstrated. Its reaction with Mn2(CO)10 and Fe(CO)5 to form ferrocenyl incorporated clusters under facile photolytic conditions is significant. Similarly, formation of some novel selenium-bridged osmium clusters, under thermolytic conditions highlights the potential of using the 1,2,3-triselena[3]ferrocenophane in novel cluster preparation. 4. Experimental details 4.1. General procedures All reactions and manipulations were performed under an inert atmosphere of pre-purified nitrogen or argon. Solvents were purified, dried and distilled under argon or nitrogen atmosphere prior to use. Infrared spectra were recorded on Perkin Elmer FTIR spectrometer. NMR spectra were recorded on Bruker AVANCE III/400 spectrometer with TMS as internal standard. Elemental analyses were carried out with a Flash 2000 elemental analyser. 1,2,3triselena[3]ferrocenophane has been synthesised by reported procedure [57]. Metal carbonyls were purchased from Fluka and SigmaeAldrich. Photochemical reactions were carried out in a water cooled double-walled quartz vessel having a 125 W mercury lamp manufactured by SAIC, India. Medium pressure mercury lamp has been used for the experiments which radiate predominantly 365e366 nm light. TLC plates were purchased from Merck (20 20 cm, silica gel 60 F254).
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Fig. 5. (a) Molecular structure of compound 5.(b) Core structure of 5. Selected bond lengths (Å) and bond angles (deg): Os(1)eSe(1) ¼ 2.5147(17), Os(1)eSe(2) ¼ 2.5286(14), Os(1)e Os(2) ¼ 2.7451(8), Os(2)eSe(1) ¼ 2.5401(16), Os(2)eSe(2) ¼ 2.5447(15), Os(2)eOs(3) ¼ 2.8592(8), Os(2)eOs(4) ¼ 2.8651(8), Os(3)eOs(4) ¼ 2.7390(9), Os(2)eSe(3) ¼ 2.5005(14), Os(3)eSe(3) ¼ 2.4697(15), Os(4)eSe(3) ¼ 2.4723(16), Se(1)eC(12) ¼ 1.910(17), Se(2)eC(17) ¼ 1.920(16); Os(1)eSe(1)eOs(2) ¼ 65.78(4), Os(1)eSe(2)eOs(2) ¼ 65.52(4), Os(3)e Se(3)eOs(4) ¼ 67.32(4), Os(3)eSe(3)eOs(2) ¼ 70.23(4), ¼ Os(4)eSe(3)eOs(2) ¼ 70.36(4), O(4)eC(4)eOs(2) ¼ 167.2(15), O(5)eC(5)eOs(2) ¼ 168.0(14), Se(1)eOs(1)e Se(2) ¼ 88.26(5), Se(1)eOs(2)eSe(2) ¼ 87.36(5).
4.2. Reaction of 1,2,3-triselena[3]ferrocenophane with Mn2(CO)10 To a THF solution of 1,2,3-triselena[3]ferrocenophane (42 mg, 0.1 mmol) [Mn2(CO)10] (78 mg, 0.2 mmol) was added and the mixture was photolysed at 20 C for 30 min under a nitrogen atmosphere. The solvent was removed under reduced pressure, and the residue was subjected to a chromatographic workup on silica gel TLC plates. Elution with dichloromethane/hexane solvent mixture yielded 5.5 mg (6%) of compound 1 as green band along with a red product that does not move on TLC plate. IR (nCO in hexane): 2027 cm1, 2008 cm1 and 1950 cm1 indicate the presence of terminal carbonyls. 1H NMR (d, CDCl3): 4.44 and 4.73 ppm (Cp protons). Elemental analyses: Found (%): C 31.11, H 1.81; Calcd for C26H16Fe2Mn2O6Se4.CH2Cl2: C 30.98, H 1.73.
(Yield ¼ 21 mg, 22%), yellow coloured compound 3 (Yield ¼ 2 mg, 2%) and orange coloured compound 5 (Yield ¼ 6 mg, 4%). Compound 3: IR (nCO in hexane): 2097 cm1, 2057 cm1, 2000 cm1 and 1968 cm1 suggest the presence of terminal carbonyls. Elemental analyses: Found (%): C 19.96, H 0.85; Calcd for C20H8FeO10Os3Se2.H2O: C 19.84, H 0.83. Compound 4: IR (nCO in hexane): 2081 cm1, 2000 cm1, 1941 cm1 indicate the presence of terminal carbonyls. 1H NMR (d, CDCl3):4.30 and 4.57 ppm (Cp protons). 77SeNMR (d, CDCl3): 757.84 and 459.47 ppm. Elemental analyses: Found (%): C 19.91, H 0.87; Calcd for C16H8FeO6Os2Se3: C 19.82, H 0.83. Compound 5: IR (nCO in hexane): 2068 cm1, 2028 cm1, 1992 cm1, 1972 cm1 and 1913 cm1 indicate the presence of terminal carbonyls. Elemental analyses: Found (%): C 16.82, H 0.62 Calcd for C21H8FeO11Os4Se3: C 16.93, H 0.54.
4.3. Reaction of 1,2,3-triselena[3]ferrocenophane with Fe(CO)5 4.5. Crystal structure determination of compound 1-5 To a hexane solution of 1,2,3-triselena[3]ferrocenophane (42 mg, 0.1 mmol) Fe(CO)5 (0.27 ml, 0.2 mmol) was added and the mixture was photolysed at 0 C for 30 min under a nitrogen atmosphere. The solvent was removed under reduced pressure, and the residue was subjected to a chromatographic workup on silica gel TLC plates by using hexane solvent as eluent, which afforded 13 mg (21%) of brown band as compound 2 along with [Fe3(CO)9(m3-Se)2]. IR (nCO in hexane): 2068 cm1, 2032 cm1, 2001, 1991 cm1 indicate the presence of terminal carbonyls. 1H NMR (d, CDCl3): 4.13 and 4.32 ppm (Cp protons), 13C NMR (d, CDCl3):70.1, 75.2, 83.7, 208.8 ppm, 77Se NMR (d, CDCl3): 218.3 ppm. Elemental analyses: Found (%): C 31.07, H 1.35; Calcd for C16H8Fe3O6Se2: C 30.91, H 1.29. 4.4. Reaction of 1,2,3-triselena[3]ferrocenophane with [Os3(CO)12] To a toluene solution of 1,2,3-triselena[3]ferrocenophane (42 mg, 0.1 mmol) [Os3(CO)12] (181 mg, 0.2 mmol) was added and the mixture was refluxed for 6 h. The solvent was removed under reduced pressure, and the residue was subjected to a chromatographic workup on silica gel TLC plates by using dichloromethane/ hexane solvent mixtures as eluent. First yellow band was unreacted osmium carbonyl, next bands were yellow coloured compound 4
Relevant crystallographic data and structure refinement details are listed in Table 2. Suitable X-ray quality crystals of compounds 1, 2, 3, 4 and 5 were grown by slow evaporation of n-hexane and dichloromethane solution at 0 oC-5 oC. A CCD technology Supernova diffractometer was used for the cell determination and intensity data collection. Monochromatic Cu (l ¼ 1.5418 Å)/Mo Ka radiation (l ¼ 0.71073 Å) were used for the measurements. The strategy for the data collection was evaluated by using the CrysAlis Pro CCD software. The data were collected by the standard ‘phiomega’ scan techniques, and were scaled and reduced using CrysAlis Pro RED software. Absorption corrections using multi j-scans were applied. The data for compound 3 was collected at room temperature which leads to slightly higher thermal values for metal ions particularly for the Os atoms. For 1 and 5 SQUEEZE was applied to disordered DCM solvent molecules and the calculated numbers of squeezed electrons are 72 for 1 and 64 electrons for 5. The structures were solved by direct methods (SHELXS) and refined by full matrix least squares against F2 using SHELXL-97 software [58]. Non-hydrogen atoms were refined with anisotropic thermal parameters. All hydrogen atoms were geometrically fixed and allowed to refine using a riding model.
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Table 2 Crystal data and structure refinement parameters for compounds 1, 2, 3, 4 and 5. Compound
1
Empirical formula Formula wt. Crystal system Space group a (Å) b (Å) c (Å) a (deg) b (deg) g (deg) Volume, (Å3) Z Dcalcd, Mg/m3 Abs coeff, mm1 F(000) Crystal size, mm q range, deg Index ranges
C104H64Fe8Mn8O24Se16 3847.23 Monoclinic P 21/c 13.5958(3) 19.2314(4) 23.2339(6) 90 103.756(3) 90 5900.6(2) 2 2.165 20.523 3664 0.29 0.20 0.13 3.02e72.51 deg. 16 h 10, 23 k 23, 23 l 28 Reflections collected/unique 45776/11556 [R(int) ¼ 0.0459] Completeness to q 98.8% Data/restraints/parameters 11556/0/721 Goodness of fit on F2 1.060 Final R indices [I > 2s(I)] R1 ¼ 0.0418, wR2 ¼ 0.1060 R indices (all data) R1 ¼ 0.0531, wR2 ¼ 0.1132 Largest diff. peak and hole, 1.540 and 1.261 e Å3
2
3
4
5
C8H4Fe1.50O3Se 310.85 Monoclinic P 21/n 7.6080(2) 13.7179(3) 18.2822(4) 90 96.639(2) 90 1895.24(8) 8 2.179 6.136 1192 0.33 0.22 0.16 2.97 to 25.00 9h 9, 16 k 15, 21 l 1 14987/3335 [R(int) ¼ 0.0236] 99.9% 3335/0/244 1.030 R1 ¼ 0.0200, wR2 ¼ 0.0462 R1 ¼ 0.0241, wR2 ¼ 0.0483 0.509 and 0.303
C80H32Fe4O40Os12Se8 4770.54 Orthorhombic Pbca 18.2769(3) 13.3537(3) 20.3340(5) 90 90 90 4962.80(18) 2 3.192 18.872 4240 0.31 0.25 0.16 3.00 to 25.00 14 h 21, 15 k 15, 24 l 24 41627/4354 [R(int) ¼ 0.1683] 99.8% 4354/8/326 1.083 R1 ¼ 0.0469, wR2 ¼ 0.1170 R1 ¼ 0.0492, wR2 ¼ 0.1201 2.224 and 5.364
C16H8FeO6Os2Se3 969.35 Orthorhombic P n a 21 24.3439(4) 11.5778(2) 7.05070(10) 90 90 90 1987.23(6) 4 3.240 35.983 1728 0.34 0.26 0.23 3.63 to 72.05 29 h 29, 8k 14, 8l 8 12402/3864 [R(int) ¼ 0.0685] 99.8% 3864/1/249 1.045 R1 ¼ 0.0512, wR2 ¼ 0.1345 R1 ¼ 0.0517, wR2 ¼ 0.1351 3.255 and 1.841
C42H16Fe2O22Os8Se6 2979.61 Triclinic P -1 12.7554(6) 14.2328(7) 18.5409(8) 104.177(4) 95.968(4) 112.099(4) 2950.8(2) 2 3.353 21.394 2616 0.33 0.26 0.23 3.21 to 25.00 15 h 13, 16 k 16, 22 l 22 23156/10357 [R(int) ¼ 0.0512] 99.7% 10357/0/721 1.040 R1 ¼ 0.0544, wR2 ¼ 0.1357 R1 ¼ 0.0717 wR2 ¼ 0.1471 3.740 and 3.709
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