Facile Os-Os bond cleavage in the reactions of [Os3(CO)10(NCMe)2] and [Os3(CO)10(μ-H)2] with tetramethylthiuram disulfide (tmtd): Syntheses and crystal structures of new polynuclear osmium carbonyl complexes containing a dimethyldithiocarbamate ligand(s)
Graphical abstract
Introduction
Dithiocarbamates are widely used in inorganic chemistry as a 3-electron donor that can stabilize metal centers in a variety of oxidation states [[1], [2], [3], [4], [5]]. Consequently, a large number of transition metal dithiocarbamate complexes are known, some of which find use in applications as key device components in materials science, as well as medicine and agriculture [1,2]. Although dithiocarbamate donors generally function as robust bidentate ligands and act in a simple spectator fashion, it is becoming increasingly apparent that this is not always the case since such ligands have been found to act in a non-innocent fashion in an increasing number of instances. For example, the formation of sulfido and thiocarboxamide ligands via a single carbon-sulfur bond cleavage of dithiocarbamates have been reported over the last four decades [6], while more recently double carbon-sulfur cleavage has been observed leading to the generation of multiple sulfido and an aminoalkylidyne ligands [[7], [8]]. These same carbon-sulfur bond cleavage reactions have been successfully exploited for the preparation of metal sulfide nanoparticles [9,10]. Finally, several studies on transition metal dithiocarbamate complexes as anticancer agents have also drawn considerable attraction [11].
Although numerous examples of mono, di and polynuclear iron and ruthenium dithiocarbamate complexes have been reported in the literature [1,5,12], dithiocarbamate complexes of osmium, which provide the greatest range of oxidation states in the Group 8 compounds that contain an ancillary dithiocarbamate ligand, remain relatively limited [1,[13], [14], [15], [16]]. Most of these osmium complexes contain either a mono or dinuclear framework. To our knowledge, only two polynuclear osmium complexes containing a dithiocarbamate ligand have been reported, and these products were isolated from the reaction of the vinyloxy-compound [HOs3(CO)10(μ-OCH=CH2)] with [Et4N][S2CNEt2] at −78 °C [14,15]. Here the initial product of substitution is [HOs3(CO)10{μ-κ1(S)-S2CNEt2}], which decarbonylates upon heating in refluxing heptane to give [HOs3(CO)9{μ3-κ2(S,S)-S2CNEt2}] (Scheme 1) [14,15].
While numerous synthetic routes exist for the preparation of new dithiocarbamate-substituted polynuclear osmium complexes, the use of thiuram disulfides as a convenient source for the delivery of a dithiocarbamate ligand(s) stands out for its convenience [17]. Using this strategy, Karim and Hogarth isolated a series of mononuclear osmium(II)-bis(dithiocarbamate) complexes of the general formula [Os(CO)2{κ2(S,S)-S2CNR2}2] instead of the desired triosmium complexes [Os3(CO)10,9{κ2(S,S)-S2CR2}] from the reactions of [Os3(CO)10L2] (L = CO, MeCN) with thiuram disulfides [16], as illustrated in Scheme 2. Surprisingly, no polynuclear osmium compounds were found in these reactions that were conducted under relatively mild conditions. These results indicate that the expected Os3-based intermediates are not stable under the temperatures employed in the reaction, decomposing to the mononuclear [Os(CO)2{κ2(S,S)-S2CNR2}2] species. Wishing to probe the nature of the initial substitution product in the reaction of [Os3(CO)10(NCMe)2] with a thiuram ligand, we have reinvestigated this reaction using tetramethylthiuram disulfide as the sulfur-delivery agent at room temperature. In addition, we have also investigated the reaction between [Os3(CO)10(μ-H)2] and [(Me2NCS2)2] in order to synthesize the Me2NCS2 analogues of the hydrido clusters as shown in Scheme 1. Herein we report the successful isolation and structural characterization of five new polynuclear osmium complexes in addition to the known mononuclear compound [Os(CO)2{κ2(S,S)-S2CNMe2}2] (4).
Section snippets
General remarks
All reactions were carried out under an inert atmosphere of nitrogen using standard Schlenk techniques unless otherwise stated, and reagent grade solvents were dried by the standard methods and freshly distilled prior to use. [Os3(CO)12] was purchased from Strem Chemical Inc. and used without further purification. Tetramethylthiuram disulfide [(Me2NCS2)2, tmtd] was purchased from Acros Organics and used as received. The starting cluster [Os3(CO)10(NCMe)2] [18] was prepared according to the
Reaction of [Os3(CO)10(NCMe)2] with tetramethylthiuram disulfide [(Me2NCS2)2]
The labile cluster [Os3(CO)10(NCMe)2] reacts with two equivalents of tetramethylthiuram disulfide [(Me2NCS2)2] at room temperature to give the three new polynuclear osmium complexes [Os3(CO)10{κ2(S,S)-S2CNMe2}2] (1), [Os4(CO)12{κ2(S,S)-S2CNMe2}2{μ3-η1(C),κ2(O,O)-CO2}(μ3-S)] (2) and [Os3(CO)9{μ3-η1(C),κ1(S)-SCNMe2}{μ-κ1(S)-SC(O)NMe2}] (3) in 20, 16, and 10% yield, respectively (Scheme 3). All three new complexes were structurally characterized by single-crystal X-ray diffraction analysis and in
Conclusions
Five new polynuclear osmium complexes namely [Os3(CO)10{κ2(S,S)-S2CNMe2}2] (1), [Os4(CO)12{κ2(S,S)-S2CNMe2}2{μ3-η1(C),κ2(O,O)-CO2}(μ3-S)] (2), [Os3(CO)9{μ3-η1(C),κ1(S)-SCNMe2}{μ-κ1(S)-SC(O)NMe2}] (3), [Os3(CO)10{μ-κ1(S)-S2CNMe2}(μ-H)] (5), and [Os3(CO)9{μ3-κ2(S,S)-S2CNMe2}(μ-H)] (6) have been isolated from the room temperature reactions of [Os3(CO)10(NCMe)2] and [Os3(CO)10(μ-H)2] with tetramethylthiuram disulfide (tmtd), and the molecular structure of each new product, except for 5, was
Acknowledgments
Financial support from the Ministry of Education, the Government of the People’s Republic of Bangladesh (SG and SEK) and the Robert A. Welch Foundation (Grant B-1093-MGR) is acknowledged. The DFT calculations were performed at UNT through CASCaM, which is an NSF-supported facility (CHE-1531468).
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Reactions of [HOs<inf>3</inf>(CO)<inf>10</inf>(µ-L)] (L = saccharinate, thiosaccharinate) with Ph<inf>3</inf>SnH and Ph<inf>3</inf>GeH
2021, Journal of Organometallic ChemistryNew iron-sulphur clusters containing thiocarboxamide, amino-carbyne and amino-carbene ligands
2021, Journal of Organometallic ChemistryCitation Excerpt :We did this with the aim of cleaving all three C-S bonds to generate both the stable iron(III) complex [Fe(S2CNEt2)3] together with the putative triradical, 1,3,5-(CH2)3C6Me3, which we hoped would be trapped and stabilised at the triiron centre. Unfortunately, we could not isolate any such product and rather generated predominantly the known sulfido-capped cluster [Fe3(CO)9(μ3-S)2] (2) [9] in addition to small amounts of two new iron-sulphur clusters, [Fe4(CO)12(μ-η1,κ1-SCNEt2)(μ-η1-CNEt2)(μ4-S)] (3) and [Fe3(CO)8(η1-CHNEt2)(μ3-S)2] (4). In a separate experiment we also unexpectedly isolated a further amino-carbene cluster [Fe3(CO)8(µ3-S)2(η2-CH3CNH2)] (5) closely related to 4 from the thermal reaction of Fe3(CO)12 with thioacetamide and herein we report details of these preparations along with the molecular structures of the three new clusters 3–5 each having been characterised by single-crystal X-ray diffraction studies.