Dalton Transactions View Article Online PAPER View Journal | View Issue Macrocycles containing 1,1’-ferrocenyldiselenolato ligands Cite this: Dalton Trans., 2018, 47, 5415 on group 4 metallocenes† Clara Sanchez-Perez,a,b Caroline E. Knapp, b Minna M. Karjalainen,a Raija Oilunkaniemi,a Claire J. Carmalt *b and Risto S. Laitinen *a 5 5 t Macrocyclic [Fe(η -C5H4Se)2M(η -C5H4R)2]2 [M = Ti (1), Zr (2), Hf (3), R = H; and M = Zr (4), Hf (5), R = Bu] were prepared and characterized by 77Se NMR spectroscopy and the crystal structures of 1–3 and 5 were determined by single-crystal X-ray diffraction. The crystal structure of 4 is known and the complex is iso- morphous with 5. 1–5 form mutually similar macrocyclic tetranuclear complexes in which the alternating Received 23rd January 2018, Fe(C5H4Se)2 and M(C5H4R)2 centers are linked by selenium bridges. The thermogravimetric analysis (TGA) Accepted 9th March 2018 of 1–3 under a helium atmosphere indicated that the complexes undergo a two-step decomposition DOI: 10.1039/c8dt00300a upon heating. The final products were identified using powder X-ray diffraction as FexMSe2, indicating Creative Commons Attribution-NonCommercial 3.0 Unported Licence. rsc.li/dalton their potential as single-source precursors for functional materials. Introduction been widely developed after the discovery that these materials may be used as precursors for semiconducting binary metal Transition metal dichalcogenides (TMDs) have been widely chalcogenides.13 Extension of this area to include various studied over the years due to their ability to intercalate species metallocene dichalcogenides has been possible because of the with apparent implications in catalytic and biological development of equipment for air-sensitive synthesis. Alkoxide This article is licensed under a – processes1 3 and biosensors.4 Due to their ability to intercalate and thiolate groups as ligands have been widely studied in the species with substantial alteration of their electronic structure development of metal-chalcogenide precursors in comparison but minimum changes in their crystal structure, they became with lesser known homologous complexes containing heavier 5–7 Open Access Article. Published on 12 March 2018. Downloaded 9/29/2021 2:52:49 AM. widely used as a new generation of semiconductors and elements. Selenium and tellurium analogues of common battery systems.8 In particular, transition metal diselenides sulphur-containing precursors are often unknown or not and ditellurides have exhibited band gaps lying within the readily available, and their metal-chalcogenolates are generally UV-visible region, which makes them promising candidates for non-volatile, polymeric compounds.14 solar cell energy devices.9 Conventional methods for prepa- Attempts to improve the stability of these compounds have η5 ration of binary and ternary transition metal dichalcogenides yielded several complexes of the type [( -C5H4R)2M(SeR)2], η5 ″ η5 (TMDs) require heating of high purity elements at high temp- [( -C5H4R)2MSe2R ] and the bulkier [( -C5H4R)2M(E 13 eratures for extensive periods, involving several homogenizing {SiMe3})2] (M = group 4 element). These studies show that – steps making their synthesis long and expensive.10 12 The there is increasing stability down the group, where the highest decomposition of metal chalcogenido complexes to metal reactivity is observed when M = Ti. chalcogenides takes place at significantly lower temperatures, Traditional synthetic routes for aryl chalcogenides involve providing high purity materials required for electronic appli- the use of chalcogenols, but due to their toxicity, synthetic cations in somewhat shorter timeframes. In recent years, the routes involving dilithium salts are preferentially used nowa- chemistry of organo-derivatives of selenium and tellurium has days.13,15 Special interest was focussed on zirconocene dichalco- genides although high temperatures were required for the – complex formation.3,15 17 Access to titanium and hafnium ana- aLaboratory of Inorganic Chemistry, Environmental and Chemical Engineering, logues through transmetallation decreased their overall yields University of Oulu, P. O. Box 3000, FI-90014 Oulu, Finland dramatically to 40%,18 and therefore the use of dilithium salts b Department of Chemistry, University College London, 20 Gordon Street, London, of diselenolate ligands with metallocene dichlorides was a WC1H 0AJ, UK. E-mail: [email protected] good compromise for simple synthetic design and achieving †Electronic supplementary information (ESI) available. CCDC 1810808–1810811. 19 For ESI and crystallographic data in CIF or other electronic format see DOI: high yields. Few examples are found in the literature involv- 20,21 10.1039/c8dt00300a ing sulfur and tellurium analogue species. An important This journal is © The Royal Society of Chemistry 2018 Dalton Trans.,2018,47,5415–5421 | 5415 View Article Online Paper Dalton Transactions 5 t 28 strategy to increase the stability and control the reactivity of (η -C5H4 Bu)2]2. In this contribution, a convenient tandem metallocene dichalcogenides is the choice of appropriate reaction involving chemically stabilized selenolates, purifi- ligands surrounding the transition metal.22 cation and structural and spectroscopic characterization of the 5 5 Aryl substituents bonded to metallocene dichalcogenides series of complexes [Fe(η -C5H4Se)2M(η -C5H4R)2]2 (M = Ti, R = have been shown to increase the molecular stability in com- H(1), M = Zr, R = H (2); M = Hf, R = H (3), tBu (5)) are reported. 16 5 5 t parison with alkyl fragments. Also, the choice of flexible [Fe(η -C5H4Se)2Zr(η -C5H4 Bu)2]2 (4) was also prepared and organic groups in the selenolato ligands are shown to allow characterized by 77Se NMR spectroscopy. Complexes 1–3 have maximum interaction between the d-orbitals of the metal and been studied as potentially suitable single-source precursors 23,24 the p-orbitals of the chalcogen atoms. for FexMSe2 materials (0 < x < 1; M = Ti, Zr, Hf) upon thermal A lot of research has been focused on the field of single- decomposition. As isolation of complexes 4 and 5 involved source precursors for binary transition metal selenides; complicated and time-consuming air sensitive column chrom- however ternary systems are still only achievable through atography, these complexes were not investigated as suitable multi-source precursor synthesis.12 Intercalation of group precursors for CVD. 4 metal dichalcogenides with first row transition metals Lithiation of ferrocene in hexane with tetramethyl- creates an overlap of the M–M 3d electronic states, which is ethylenediamine (TMEDA) proceeded with further addition of 25 5 29 predicted to tune their optical properties. As these materials selenium powder to form Li2[Fe(η -SeC5H4)2]. The cyclic η5 η5 are potentially interesting for photovoltaic applications, the complexes [Fe( -C5H4Se)2M( -C5H4R)2]2 [R=H,M=Ti(1), Zr development of precursors for their deposition is long (2), Hf (3); R = tBu, M = Zr (4), Hf (5)] were isolated from the 5 overdue. To the best of our knowledge, we are reporting the equimolar reaction of Li2[Fe(η -SeC5H4)2] with the respective first class of single-source precursors for iron-doped group 4 metallocene dichloride (Scheme 1), with high yields of com- transition metal dichalcogenides. plexes 1–3 (84% (1), 74% (2), and 69% (3)). The molecular 5 5 structures of [Fe(η -C5H4Se)2M(η -C5H5)2]2 [M = Ti (1), Zr (2), Creative Commons Attribution-NonCommercial 3.0 Unported Licence. Hf (3)] are shown in Fig. 1, left and that of the related complex η5 η5 t Results and discussion [Fe( -C5H4Se)2Hf( -C5H4 Bu)2]2 (5) is shown in Fig. 1, right. Selected bond lengths and angles are given in Table 1. 5 5 – The syntheses of [Fe(η -C5H4E)2M(η -C5H4R)2] (E = S, M = Ti, Crystallographic parameters of complexes 1 3 and 5 are listed R = H; E = Se, M = Zr, R = H, tBu; M = Hf, R = tBu) have been in Table 2. – reported,26 28 but the only crystallographically characterized All five complexes 1–5 form similar macrocyclic tetranuclear 5 complex is the formally dimeric macrocycle [Fe(η -C5H4Se)2Zr complexes in which the alternating Fe(C5H4Se)2 and This article is licensed under a Open Access Article. Published on 12 March 2018. Downloaded 9/29/2021 2:52:49 AM. Scheme 1 General synthesis of 1–5. 5 5 5 5 t Fig. 1 Molecular structures of [Fe(η -C5H4Se)2M(η -C5H5)2]2 [M = Ti (1), Zr (2), Hf (3)] (left) and [Fe(η -C5H4Se)2Hf(η -C5H4 Bu)2]2 (5) (right) including the numbering of central atoms. Thermal ellipsoids are displayed at a 50% probability level. 5416 | Dalton Trans.,2018,47,5415–5421 This journal is © The Royal Society of Chemistry 2018 View Article Online Dalton Transactions Paper Table 1 Selected bond lengths (Å) and angles (°) in 1–3 and 5 1 M=Ti 2 M=Zr 3 M=Hf 5 M=Hf Lengths (Å) M1–Se1 2.5471(11) 2.6434(11) 2.6219(5) 2.6438(11) M1–Se3 2.5242(12) 2.6396(12) 2.6145(5) 2.6180(10) M2–Se2 2.5414(11) 2.6284(15) 2.6197(5) 2.6368(11) M2–Se4 2.5517(10) 2.6521(14) 2.6301(5) 2.6253(10) Se1–C111 1.907(4) 1.918(7) 1.918(4) 1.923(8) Se2–C121 1.907(4) 1.907(7) 1.913(4) 1.902(8) Se3–C211 1.902(4) 1.908(7) 1.912(5) 1.906(9) Se4–C221 1.904(5) 1.921(7) 1.916(5) 1.894(9) Angles (°) Se1–M1–Se3 97.80(4) 102.52(4) 102.947(16) 98.53(3) Se2–M2–Se4 99.40(4) 100.98(5) 101.800(16) 98.37(3) 5 5 Fig. 2 Thermogravimetric analysis (TGA) of [Fe(η -C5H4Se)2Ti(η - 5 5 5 C5H5)2]2 (1) in green, [Fe(η -C5H4Se)2Zr(η -C5H5)2]2 (2) in red and [Fe(η - M(C5H4R)2 centres are linked by selenium bridges.