A molecular orbital comparison of molybdenum-sulfur dimers with sulfido ligands bridged by CH2 and FeCp fragments

Abstract

An extensive reactivity with hydrogen and unsaturated molecules has been characterized for the /t-sulfide ligands in (CpMo)2(M-S)2S2CH2 (2). However, the bridging disulfide ligand in the heteronuclear cluster [(CpMo)2(M-S2)(M-S2FeCp)]+ (3) was not reactive toward hydrogen or olefins. Extended Huckel molecular orbital calculations have been carried out for 2 and for the hypothetical Fe-Mo cluster with bridging sulfides rather than a disulfide ligand [(CpMo)2(/t-S)2(S2FeCp)]+ (3'). The electronic structures of complexes 2 and 3' are analyzed in terms of the CP2M02S4 and methylene and the FeCp+ fragment orbitals, respectively. This approach leads to a qualitative understanding of the reasons for the structural and reactivity differences between 2 and 3.

Dinuclear μ-Sulfido Complexes of Molybdenum with (Dimethylamino)ethyl-Substituted Cyclopentadienyl Ligands

“…Although a M−M‘ bonding interaction cannot be assigned solely on the basis of distance, the asymmetry, which does not appear to be a result of packing forces, suggests that there may be a weak bonding interaction between Cu and Mo(2). The distance is similar to previously reported Cu−Mo distances in mixed-metal M 4 S 4 cubane and M 3 S 3 incomplete cubane structures. , Examples of Mo−M‘ bonding interactions have been observed previously for clusters derived from the Mo 2 S 4 core, and extended Huckel calculations have provided a bonding description for one such system …”

“…Although the reactivity of the dinuclear methanedithiolate-bridged derivatives of molybdenum has been extensively studied, a crystal structure of one of these derivatives has not been reported previously. Previous molecular orbital calculations on this complex (unsubstituted Cp ligand) indicated that the extensive sulfur-based reactivity observed for the structure was consistent with the presence of two bridging sulfido atoms rather than a μ 2 −η 2 disulfido ligand . The calculations also indicated that there was an antibonding interaction between these two bridging ligands.…”

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

“…[3][4][5] Investigations of these homogeneous Mo 2 S 4 complexes cover a broad range of topics, including catalysis and electrocatalysis, [6][7][8][9][10][11] a wide variety of bond forming reactions, [12][13][14][15][16][17][18][19] free radical reactivity, [20][21][22][23][24] photolytic reactions, 25 and the preparation of heterometallic sulfide clusters. [26][27][28][29][30][31] 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, 6,32 homogeneous and heterogeneous catalysis of hydrogen transfer pathways.…”

“…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.…”