Electrophilic Substitution of Nitrogen Heterocycles by Molybdenum Sulfide Complexes

Abstract

The electrophilic tetranuclear complex [(Cp′Mo(µ-S)) 2 (S 2 CH 2 )] 2 (BF 4 ) 2 (1: Cp′ ) C 5 H 5 (1a), C 5 H 4 Me (1b)), in which two dinuclear complexes are joined by a sulfur-sulfur bond, reacts with the electron-rich nitrogen heterocycles pyrroles and indoles at room temperature. The reactions involve heterolytic scission of the disulfide bond by the nucleophiles followed by proton transfer, and the products areThe reactions have been characterized for pyrrole, 1-methylpyrrole, 1,2,5-trimethylpyrrole, and 1-methylindole. The regiochemistry of the reactions depends on pyrrole substituents. Complex 1 also reacts readily with the coordinated pyrrolyl ligand in (PMe 2 Ph) 3 Cl 2 Re(NC 4 H 4 ). The electrophilic substitution occurs on the 3-position of the heterocycle to form [(Cp′Mo) 2 (S 2 CH 2 )(µ-S)(µ-SC 4 H 3 N)ReCl 2 (PMe 2 Ph) 3 ]BF 4 (7). Complex 7 undergoes a further reaction with 1 to give the hydrogen abstraction product [(Cp′Mo) 2 (S 2 CH 2 )(µ-S 2 C 4 H 2 N)ReCl 2 (PMe 2 Ph) 3 ]BF 4 ( 8). An X-ray diffraction study of 8b confirms that the 3-and 4-carbons of the pyrrolyl ligand are coordinated to the µ-sulfido ligands of the molybdenum dimer. The new products suggest that there are a number of ways in which electron-rich heterocycles might interact with a sulfided molybdenum catalyst in the hydrodenitrogenation reactions. Reactions of 1 with other nucleophiles have also been surveyed.

Reactions of Dithiolate Ligands in Mononuclear Complexes of Rhenium(V)

“…For example the allylic C−H bond in many alkenes adds across the disulfide ligand to form new C−S and S−H bonds under mild conditions. In a second example the complex [(CpMoμ-S) 2 (S 2 CH 2 )] 2 2+ served as an oxidant for the conversion of benzylamine to benzylimine (hydrolyzed to benzaldehyde) and of benzyl alcohol to benzaldehyde . In addition, heterogeneous rhenium and other metal sulfides function as dehydrogenation (and hydrogenation) catalysts .…”

Free Energy Landscapes for S−H Bonds in Cp*2Mo2S4 Complexes

“…Homogeneous Mo 2 S 4 complexes have been widely studied as a result of the prevalence of molybdenum sulfides in both hydrogenation and hydrodesulfurization (HDS) − catalysts and enzymes. − Investigations of these homogeneous Mo 2 S 4 complexes cover a broad range of topics, including catalysis and electrocatalysis, − a wide variety of bond forming reactions, − free radical reactivity, − photolytic reactions, and the preparation of heterometallic sulfide clusters. − In spite of the importance of molybdenum sulfide chemistry and the extensive research into Mo 2 S 4 complexes, very few S−H bond energies have been determined for MoS−H bonds, , even though they are key to a fundamental understanding of homogeneous and heterogeneous catalysis of hydrogen transfer pathways.…”

Binding Small Molecules to a cis-Dicarbonyl 99TcI-PNP Complex via Metal–Ligand Cooperativity

“…Pyrrolide and pyrazolide complexes 11 and 12 with 99 Tc are the first of their kind. Only two pyrrolide complexes have been reported for Re 47,48 and one pyrazolide complex for Mn within the manganese triad. 49…”