The solid-state structures of all members in the series of trichalcogenaferrocenophanes [FeIJC 5 H 4 E) 2 E′] (E, E′ = S, Se, Te) (1-9) have been explored to understand the trends in secondary bonding interactions (SBIs) between chalcogen elements sulfur, selenium, and tellurium. To complete the series, the crystal structures of the four hitherto unknown complexes [Fe(C 5 H 4 S) 2 Te] (3), [Fe(C 5 H 4 Se) 2 S] (4), [Fe(C 5 H 4 Se) 2 Te] (6), and [Fe(C 5 H 4 Te) 2 S] (7) have been determined in this contribution. The packings of all complexes 1-9 were considered by DFT calculations at the PBE0/pob-TZVP level of theory using periodic boundary conditions. The intermolecular close contacts were considered by QTAIM and NBO analyses. The isomorphous complexes [Fe(C 5 H 4 S) 2 S] (1), [Fe(C 5 H 4 S) 2 Se] (2), and [Fe(C 5 H 4 Se) 2 Se] (5a) form dimers via weak interactions between the central chalcogen atoms of the two trichalcogena chains of adjacent complexes. In the second isomorphous series consisting of [Fe(C 5 H 4 Se) 2 S] (4) and 5b, the complexes are linked together into continuous chains by short contacts via the terminal selenium atoms. The intermolecular chalcogen-chalcogen interactions are significantly stronger in complexes [Fe(C 5 H 4 S) 2 Te] (3), [Fe(C 5 H 4 Se) 2 Te] (6), and [Fe(C 5 H 4 Te) 2 E′] (E′ = S, Se, Te) (7-9), which contain tellurium. The NBO comparison of donor-acceptor interactions in the lattices of [Fe(C 5 H 4 S) 2 S] (1), [Fe(C 5 H 4 Se) 2 Se] (5a and 5b), and [Fe(C 5 H 4 Te) 2 Te] (9) indeed shows that the n(5p Te) 2 → σ*(Te-Te) interactions in 9 are the strongest. All other interaction energies are significantly smaller even in the case of tellurium. The computed natural charges of the chalcogen atoms indicate that electrostatic effects strengthen the attractive interactions in the case of all chalcogen atoms.

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were prepared and characterized by 77 Se 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 isomorphous with 5. 1-5 form mutually similar macrocyclic tetranuclear complexes in which the alternating Fe(C 5 H 4 Se) 2 and M(C 5 H 4 R) 2 centers are linked by selenium bridges. The thermogravimetric analysis (TGA) of 1-3 under a helium atmosphere indicated that the complexes undergo a two-step decomposition upon heating. The final products were identified using powder X-ray diffraction as Fe x MSe 2 , indicating their potential as single-source precursors for functional materials.

† Electronic Supplementary Information (ESI) available: Crystal data and details of structure determination and selected bond parameters of 2-5, CCDC 1522462-1522465, Definition of the angle of distortion. Energy profile of Th2Te2 + [Pt((h 2nb)(dppn)]. 31 P{ 1 H} NMR spectrum of [Pt(TeTh)2(dppn)].The oxidative addition reaction of ditellurides R2Te2 [R = n Bu, Ph, Th (2-thienyl, C4H3S)] to [Pt(η 2 -nb)(dppn)] (nb = norbornene, dppn = 1,2-bis(diphenylphosphino)naphthalene) was found to afford [Pt(TeR)2(dppn)] [R = n Bu (1), Ph (2), Th (3)] and [Pt(TeR)(R)(dppn)] [R = Ph (4), Th (5)] as a result of the cleavage of the Te-Te or C-Te bond, respectively. The reactions and the product distributions were monitored by 31 P{ 1 H} NMR spectroscopy. The spectral interpretation was assisted by the high-yield preparation of [Pt(TePh)2(dppn)] (2) and [Pt(TeTh)2(dppn)] (3) by ligand echange reactions from [PtCl2(dppn)], and by the crystal structure determinations and spectral characterizations of 2 and 3. Two series of reactions were carried out both at room temperature and at -80 o C. One involved the addition of the toluene solution of R2Te2 to that of [Pt(η 2 -nb)(dppn)], and the other the addition of [Pt(η 2 -nb)(dppn)] solution to the R2Te2 solution. The oxidative addition of n Bu2Te2 to [Pt(η 2 -nb)(dppn)] yielded solely [Pt(Te n Bu)2(dppn)]. In case of Ph2Te2 and Th2Te2, the reaction of equimolar amounts of ditelluride and [Pt(η 2 -nb)(dppn)] afforded only [Pt(TeR)(R)(dppn)] (R = Ph, Th), but when an excess of R2Te2 was used, the addition of [Pt(η 2 -nb)(dppn)] to the ditelluride resulted in the formation of a mixture of [Pt(TeR)2(dppn)] and [Pt(TeR)(R)(dppn)] with the latter the main component. An excess of R2Te2 and the lowering of the temperature favoured the formation of [Pt(TeR)2(dppn)]. The reaction energetics in toluene was calculated at revPBE GGA DFT / TZVP(f) level of theory. The increase of the electron withdrawing nature of the organic substituent rendered [Pt(TeR)(R)(dppn)] increasingly stable with respect to [Pt(TeR)2(dppn)]. The computation of the energy profiles of the likely pathways of the oxidative addition indicated that concurrent formation of [Pt(TeR)2(dppn)] and [Pt(TeR)(R)(dppn)] (R = Ph, Th) may be more likely than the formation of the latter due to the decomposition of the former. This was verified experimentally by stirring pure [Pt(TeR)2(dppn)] in toluene for a prolonged time at room tempertature. No decomposition was observed.

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