Syntheses, Structures, and Reactions of Cyclopentadienyl Metal Complexes with Bridging Sulfur Ligands

Abstract

Homogeneous cyclopentadienyl complexes of molybdenum and rhenium that contain sulfido and/or disulfido ligands have been synthesized. The structures and reactivities of the complexes are compared, and reactions which are relevant to those of heterogeneous metal sulfide catalysts are discussed.An intriguing feature of the heterogeneous transition metal sufides is their ability to participate in organometallic chemistry by virtue of their reactivity with hydrogen and with organic substrates. The most prominent class of reactions catalyzed by metal sulfide surfaces is the commercially important hydrotreating process, in which the hydrogenolysis of C-S and C-N bonds in aromatic heterocycles is effected (1-8). While a molybdenum sufide based system is the catalyst used most widely in industry, other metal sulfides have been shown to be more active than the molybdenum system in this process (9). Additional reactions for metal sulfides have also been characterized, either as a part of the hydrotreating sequence or in independent studies (1,2). These include hydrogen activation and hydrogen/deuterium exchange, the hydrogénation and isomerization of olefins, and the dehydrogenation of alkanes. Reactions with carbon monoxide have been identified for molybdenum sulfide surfaces, including the reduction of CO to methane or to alcohols (10-13), and its conversion to C0 2 in the water gas shift reaction (14). Despite this extensive range of reactivity, examples of homogeneous metal complexes with sulfido ligands that react with dihydrogen and with organic molecules are still relatively rare (75). In this paper we focus on two of the metal sulfides, those of molybdenum and rhenium. We briefly compare characteristics of M0S2 and ReS 2 that contribute to their catalytic chemistry, and we describe molecular derivatives of molybdenum and rhenium that permit us to probe reactions related to those of the heterogeneous systems. Heterogeneous Molybdenum and Rhenium SulfidesBoth M0S2 and ReS 2 crystallize as layered sulfides, but there are significant 1

Syntheses and structures of chalcogen-bridged binuclear group 5 and 6 metal complexes

“…(Cp 0 = g 5 -C 5 Me 4 Et) showed interesting structures and reactivity. 13 The facile reactivity of [Cp 2 Mo 2 S 4 ] towards H 2 under ambient conditions yielded bis(hydrosulfide) complex [Cp 2 Mo 2 (l-S) 2 (l-SH) 2 ]. 14 The reactions of alkenes or alkynes with [Cp 2 Mo 2 (l-S) 2 (l-g 2 -SH) 2 ] generated bis-dithiolate complexes with exciting structural aspects.…”

Molecular Design of Cyclopentadienyl Tantalum Sulfide Complexes

“…The incorporation of sulfur groups to cyclopentadienyl transition metal moieties affords an accessible entry to di- and polynuclear sulfide transition metal complexes, , where the distinctive chemical and electronic properties of the cyclopentadienyl ring make a better isolation and spectroscopic characterization possible, and therefore, reactivity on these sulfide species can be further explored.…”

Binding of Alkenes to ReS4-

“…[20][21][22] In principle, isoelectronic metal sulfides could be used to effect the corresponding addition of sulfur across the double bond of alkenes. [23][24][25] Aside from synthetic implications, this alkene sulfidation reaction would contribute new insights into the energetics and mechanism of the oxidation process. It is also reasonable to expect that such sulfidation reactions would shed light on the organic chemistry of metal sulfides, which is highly relevant to the hydrodesulfurization process.…”