Thiophene and Butadiene−Thiolate Complexes of Molybdenum:  Observations Relevant to the Mechanism of Hydrodesulfurization

Abstract

Mo(PMe3)6 reacts with thiophene to give the eta5-thiophene complex (eta5-C4H4S)Mo(PMe3)3 and the eta5-butadiene-thiolate complex (eta5-C4H5S)Mo(PMe3)2(eta2-CH2PMe2), which are the first examples of (i) eta5-thiophene coordination and (ii) C-S cleavage and hydrogenation by a molybdenum compound. Deuterium labeling studies suggest that the hydrogenation of thiophene may involve an alkylidene intermediate, an observation that has ramifications for the mechanisms of hydrodesulfurization.

Spontaneous Si–C bond cleavage in (TriphosSi)-nickel complexes

“…Most notable is the W(PMe 3 ) 3 (η 2 -CH 2 PMe 2 )H complex, which was reported as an electron-rich and highly reactive complex for the hydrodesulfurization of thiophenes. 13,32 Due to the high π-character of the P-C bond, we expected that 5 would react with heterocumulenes and exam- ined the reaction of 5 with CO 2 under 10 bar/70°C as was reported by Bennett et al for [(dcpe)NiCl(C(vCHCO 2 Me)PPh 2 -κP,C 1 )] (dcpe = bis(dicyclohexylphosphino)ethane). 36 Contrary to our expectations, no reaction was observed.…”

“…The high reactivity of L 4 M(CH 2 PMe 2 ) complexes (M = Co, Fe) and other phosphino methanide complexes 3,6,7,13,15,25,[31][32][33][34][35] prompted us to investigate the reactivity of the unprecedented complex 5. Most notable is the W(PMe 3 ) 3 (η 2 -CH 2 PMe 2 )H complex, which was reported as an electron-rich and highly reactive complex for the hydrodesulfurization of thiophenes.…”

Catalysis and Organometallic Chemistry of Monometallic Species

“…120 In the field of C-H activation theoretical studies of the spin crossover transition states for the addition of methane to a series of group 6 metallocenes including ansaderivatives, 121 127 and chromium() radical initiated C-S cleavage in dithiocarbamate and thiocarbenoind complexes. 128 Molybdenum nitrogen and sulfur heterocycle complexes relevant to hydrodenitrogenation 129 and hydrodesufurisation 130 respectively have also been prepared and structurally characterised.…”

Reversible Oxidative-Addition and Reductive-Elimination of Thiophene from a Titanium Complex and Its Thermally-Induced Hydrodesulfurization Chemistry

“…27 Moreover, the formation of 2 under mild conditions differs from the synthesis of nearest-neighbor Group 6 ring-opened thiophene derivatives which typically require photolysis or heating to promote thiophene activation, 26,[28][29][30][31][32] with the exception of Mo(PMe3)6 which reacts with thiophene at room temperature to give (η 5 -C4H5S)Mo(PMe3)2(η 2 -CH2PMe2). 33 Photolyzing aromatic solutions of 2 with blue LED light leads to the formation of 1 and thiophene as shown by monitoring the reactions by 1 H NMR and UV-vis spectroscopies (Figures 2, S6 and S9). The complete reversion is only possible in dilute solutions (ca.…”