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In this work, the pathways to the formation of the series of mononuclear [RuCl2(CO)2(ERR’)2] complexes from [RuCl2(CO)3]2 and ERR’ or E2Tpn2 (E = S, Se, Te; R, R’ = Me, Ph; Tpn = thiophen-2-yl) were explored by experimental and computational techniques. The reactions were monitored by 77Se and 125Te NMR spectroscopy and the products were characterized by 13C{1H}, 77Se, and 125Te NMR spectroscopy, as well as by single-crystal X-ray crystallography. The treatment of [RuCl2(CO)3]2 with ERR’ (E = S, Se, Te; R, R’= Me, Ph) in CH2Cl2 or THF produced [RuCl2(CO)2(ERR’)2] and [RuCl2(CO)3(ERR’)]. The yields were rather similar in both solvents, but the reactions were faster in THF than in CH2Cl2. The highest yields were observed for the telluroether complexes, and the yields decreased with lighter chalcogenoethers which was consistent with the computed energetics. All [RuCl2(CO)2(ERR’)2] complexes were cis(Cl), cis(CO), trans(ERR’)-isomers. This is consistent with the relative trans-influence strengths of the different donor atoms involved in the coordination sphere around ruthenium. The 77Se and 125Te NMR spectra of the complexes with symmetric chalcogenoether ligands (ER2) exhibited one resonance, whereas with unsymmetric chalcogenoether ligands (ERR’) two close-lying resonances were observed due to the presence of two discrete stereoisomers. The PBE0-D3/def2-TZVP calculations of the reaction pathways showed that the energetics is independent of the nature of the solvent and that thermal energy at room temperature is sufficient to cleave the bridging Ru–Cl bonds in [RuCl2(CO)3]2, which can then react with ERR’. The substitution of one CO ligand of the intermediate [RuCl2(CO)3(ERR’)] by the second ERR’ is the rate-determining step in all reactions. The reaction between [RuCl2(CO)3]2 and Te2Tpn2 (Tpn = thiophen-2-yl) afforded cct-[RuCl2(CO)2(TeTpn2)2] and TeTpn2 together with the precipitation of tellurium. The decomposition of Te2Tpn2 into TeTpn2 was monitored by 12, Tiivistelmä Tässä väitöskirjatyössä tutkittiin sekä kokeellisesti että laskennallisesti mononukleaaristen [RuCl2(CO)2(ERR’) 2] kompleksien muodostumisreittejä. [RuCl2(CO)3]2:n reaktioita ERR’:n ja E2Tpn2:n (E = S, Se, Te; R, R’ = Me, Ph; Tpn = tiofen-2-yyli) kanssa seurattiin 77Se- ja 125Te NMR-spektroskopian avulla. Kaikki tuotteet karakterisoitiin 13C{1H}, 77Se ja 125Te NMR-spektroskopialla sekä röntgenkristallografialla. [RuCl2(CO)3]2:n ja ERR’:n (E = S, Se, Te; R, R’ = Me, Ph) välisessä reaktiossa muodostuu [RuCl2(CO)2(ERR’)2]- ja [RuCl2(CO)3(ERR’)]-komplekseja sekä CH2Cl2:ssa että THF:ssa. Kompleksien saannot olivat melko samanlaisia molemmissa liuottimissa, mutta reaktiot olivat nopeampia tetrahydrofuraanissa kuin dikloorimetaanissa. Telluroeetterikompleksien saannot olivat suurimmat, mutta kevyemmillä kalkogenoeetterikomplekseilla pienemmät. Tiheysfunktionaaliset energialaskut ovat yhteensopivat havaittujen trendien kanssa. [RuCl2(CO)2(ERR’)2]-kompleksit esiintyivät cis(Cl), cis(CO), trans(ERR')-isomeereinä. Tämä voidaan selittää ruteniumiin koordinoitujen ligandien suhteellisilla trans-vaikutuksilla. Kun komplekseissa oli symmetrinen kalkogenoeetteriligandi (ER2), havaittiin 77Se ja 125Te NMR-spektreissä vain yksi resonanssi. Mikäli koordinoitunut ligandi oli epäsymmetrinen (ERR’), havaittiin kaksi lähekkäin olevaa resonanssihuippua johtuen kahdesta steroisomeeristä. PBE0-D3/def2-TZVP-laskut osoittivat, että reaktioiden energetiikka on riippumaton liuottimesta ja että lämpöenergia huoneenlämpötilassa riittää katkaisemaan silloittavan Ru–Cl-sidoksen [RuCl2(CO)3]2:ssa. ERR’:n sitoutuminen vapautuneeseen koordinaatiopaikkaan muodostaa välituotteen [RuCl2(CO)3(ERR')]. CO-ligandin substituutio toisella kalkogenoeetteri-molekyylillä ERR’ on reaktionopeuden määräävä vaihe. [RuCl2(CO)3]2:n ja Te2Tpn2:n (Tpn = tiofen-2-yyli) välisessä reaktiossa muodostuu cct-[RuCl2(CO)2(TeTpn2)2]:n ja TeTpn2:n lisäksi telluuria. Te2Tpn2:n hajoamista TeTpn2:ksi seurattiin 125Te NMR-s

The reaction of [RuCl₂(CO)₃]₂ and Te₂Tpn₂ (Tpn=thiophen-2-yl, C₄H₃S) in the absence of light resulted in the formation of cct-[RuCl₂(CO)₂(TeTpn₂)₂] (1) [cis(Cl)-cis(CO)-trans(TeTpn₂)] and TeTpn₂ (2) together with the precipitation of tellurium. The complex 1 and the monotelluride 2 were characterized by NMR spectroscopy and single-crystal X-ray diffraction. The decomposition of Te₂Tpn₂ to TeTpn₂ has been monitored by ¹²⁵Te NMR spectroscopy and seemed to be faster than the ligand substitution in [RuCl₂(CO)₃]₂ by TeTpn₂. A catalytic cycle is proposed for the decomposition of Te₂Tpn₂ to TeTpn₂ based on the PBE0-D3/def2-TZVP calculations.

The pathways to the formation of the series of [RuCl₂(CO)₂(ERR′)₂] (E = S, Se, Te; R, R′ = Me, Ph) complexes from [RuCl₂(CO)₃]₂ and ERR′ have been explored experimentally in THF and CH2Cl2, and computationally by PBE0-D3/def2-TZVP calculations. The end-products and some reaction intermediates have been isolated and identified by NMR spectroscopy, and their crystal structures have been determined by X-ray diffraction. The relative stabilities of the [RuCl₂(CO)₂(ERR′)₂] isomers follow the order cct > ccc > tcc > ttt ≈ ctc (the terms c/t refer to cis/trans arrangement of the ligands in the order of Cl, CO, and ERR′). The yields were rather similar in both solvents, but the reactions were significantly faster in THF than in CH₂Cl₂. The highest yields were observed for the telluroether complexes, and the yields decreased with lighter chalcogenoethers. PBE0-D3/def2-TZVP calculations indicated that the reaction path is independent of the nature of the solvent. The substitution of one CO ligand of the intermediate [RuCl₂(CO)₃(ERR′)] by the second ERR′ shows the highest activation barrier and is the rate-determining step in all reactions. The observed faster reaction rate in THF than in CH₂Cl₂ upon reflux can therefore be explained by the higher boiling point of THF. At room temperature the reactions in both solvents proceed equally slowly. When the reaction is carried out in THF, the formation of [RuCl₂(CO)₂(THF)] is also observed, and the reaction may proceed with the substitution of THF by ERR′. The formation of the THF complex, however, is not necessary for the dissociation of the [RuCl₂(CO)₂]₂. Thermal energy at room temperature is sufficient to cleave one of the bridging Ru–Cl bonds. The intermediate thus formed undergoes a facile reaction with ERR′. This mechanism is viable also in non-coordinating CH₂Cl₂.