Unexpected Reactions of 2,5-Dimethylthiophene (2,5-Me₂T) in Cp*Ir(η⁵-2,5-Me₂T)²⁺, Cp*Ir(η⁴-2,5-Me₂T), and Cp*Ir(C,S-2,5-Me₂T) with Cobaltocene

Abstract

The reaction of Cp*Ir(η5-2,5-Me2T)2+ (1) (Cp* = η5-C5Me5) with the reducing agent Cp2Co yields Cp*Ir(η4-2,5-Me2T) (2) and Cp*Ir(C,S-2,5-Me2T) (3), as well as the unexpected Cp*Ir(η4-2,5-Me2T·C5H4) (4), which can also be prepared by reacting 1 with Cp-. An X-ray diffraction study of 4 shows the η4-2,5-Me2T·C5H4 ligand to be a ring-opened 2,5-Me2T allyl thiolate conjugated to a cyclopentadienylidene unit. The reduced products 2 and 3 react with Cp2Co to give a ferrole-type product Cp*[IrC(Me)CHCHC(Me)]CoCp in which the planar iridacyclopentadiene ring is π-bonded to the cobalt, as established by a structural investigation. The Cp*Co analog of 5 is prepared by the reaction of 2 or 3 with Cp*Co(CH2CH2)2. These studies demonstrate that cobaltocene and Cp*Co(CH2CH2)2 readily desulfurize the 2,5-dimethylthiophene ligand in 2 and 3, which supports a previously proposed mechanism for thiophene hydrodesulfurization.

Thiophenes in Organotransition Metal Chemistry: Patterns of Reactivity

“…The Cp*Ir(η 5 -2,5-Me 2 T) 2+ dication has also been observed to undergo reactions with other nucleophiles with acidic protons. Thus, - CH(CO 2 Me) 2 and cyclopentadienide react to give the products shown in eqs 32 94 and 33 . The acidic protons in the proposed intermediates are removed by a second mole of nucleophile to give the products, whose structures were established crystallographically and are very similar to that of the related acylthiolate Cp*Ir(η 4 -SC 3 H 2 MeC(O)Me) .…”

Hydrogenation, Hydrogenolysis, and Desulfurization of Thiophenes by Soluble Metal Complexes: Recent Achievements and Future Directions

“…Recent examples of desulfurization of thiophenes by polynuclear complexes have been reported by Curtis,30 Angelici, 31 Rauchfuss, 32 Jones, 29 and Bianchini. 28 Among these, the overall degradation of T assisted by the cluster Cp′ 2 Mo 2 Co 2 S 3 (CO) 4 (Cp′ ) CH 3 C 5 H 4 ) is the model reaction that, in our opinion, best resembles the heterogeneous counterparts, particularly those classified as "Co/Mo/S" phase, 1a in terms of both structural motif and HDS activity (the hydrogen atoms necessary for the hydrogenolysis step are in fact externally added and not already incorporated into the organometallic precursor) (Scheme 9a).…”

Synthesis of Dimanganese Ruthenium Complexes from the Reaction of Ruthenium-Coordinated Thiophenes and Selenophene with [(1-Methylnaphthalene)Mn(CO)3]BF4and Cp2Co

“…There have been several reports on μ 3 -bound complexes, some of which are η 4 ,S-μ 3 -bound thiophene complexes that are prepared from the reaction of a η 4 -thiophene complex with dinuclear complexes. 1b, This observation may relate to the binding modes of sulfur-containing hydrocarbons to a metal-sulfide surface, intermediates in the HDS reaction, and homogeneous reactions containing a promoter. Examples of desulfurization of thiophenes by polynuclear complexes have been reported by Curtis, Angelici, Rauchfuss, Jones, Suzuki, and Bianchini …”