The complex {(η 5 -C 5 H 3 ) 2 (SiMe 2 ) 2 }Ru 2 (CO) 4 (1), which features the doubly linked dicyclopentadienyl ligand (η 5 -C 5 H 3 ) 2 (SiMe 2 ) 2 , reacts with phosphines (PMe 3 , PCy 3 , PPh 3 ) to give {(η 5 -C 5 H 3 ) 2 (SiMe 2 ) 2 }Ru 2 (CO)(µ-CO) 2 (PR 3 ) (2a-c), with halogens X 2 (X ) Cl, Br, I) to give the Ru-Ru-cleaved products {(η 5 -C 5 H 3 ) 2 (SiMe 2 ) 2 }Ru 2 (CO) 4 (X) 2 (3a-c), with X 2 and AgTfO to give [{(η 5 -C 5 H 3 ) 2 (SiMe 2 ) 2 }Ru 2 (CO) 4 (µ-X)] + TfO -(X ) Cl, Br, I; 4a-c), and with SnCl 2 to give {(η 5 -C 5 H 3 ) 2 (SiMe 2 ) 2 }Ru 2 (CO) 4 (µ-SnCl 2 ) (5), resulting from the insertion of SnCl 2 into the Ru-Ru bond. Reduction of 1 with Na/Hg generates [{(η 5 -C 5 H 3 ) 2 (SiMe 2 ) 2 }Ru 2 (CO) 4 ] 2-(6), which reacts with (η 5 -C 5 H 5 ) 2 TiCl 2 to give {(η 5 -C 5 H 3 ) 2 (SiMe 2 ) 2 }Ru 2 (CO) 4 {µ-Ti(η 5 -C 5 H 5 ) 2 } (7). Ultraviolet photolysis of 1 with diphenylacetylene and phenylacetylene yields a series of five dinuclear Ru complexes (8-10, 12, 13) containing one or two bridging acetylene units. The rigidity of the doubly linked (η 5 -C 5 H 3 ) 2 (SiMe 2 ) 2 ligand substantially influences the reactivity and structures of the complexes. Molecular structures of 1, 2a, 3c, 5, 9, 10, and 12 as determined by X-ray diffraction studies are also presented.

Complexes that feature a single NO bound to Fe, as postulated in various carboxylate-rich metalloproteins, were prepared by mixing Fe(II) salts, NO, and the sterically encumbered 2,6-dimesitylbenzoate (Mes2ArCO2-). Among the compounds isolated are the potentially useful heterobimetallic synthon Tl(mu-Mes2ArCO2)3Fe(NO) and a novel cubane Fe4(Mes2ArCO2)4(NO)4(mu3-OH)4 that forms in the presence of added H2O and features syn-[FeNO]2 units.

The dinuclear ruthenium complex {(η 5 -C 5 H 3 ) 2 (SiMe 2 ) 2 }Ru 2 (CO) 3 (C 2 H 4 )H + BF 4 -(1) catalyzes the intermolecular hydroamination of arylalkynes (e.g., phenylacetylene) with arylamines (e.g., p-toluidine) to give imines (e.g., (Ph(Me)CdN(p-MeC 6 H 4 )). Although the catalyst has a limited lifetime (up to 6 turnovers), details of the reaction mechanism have been elucidated by isolation and characterization (X-ray and/or NMR) of six of the seven intermediates and reaction-terminating species. The mechanism is fundamentally different from all previously proposed mechanisms for alkyne hydroamination. The rigid doubly bridged bis((dimethylsilyl)cyclopentadienyl) ligand is an important feature of the catalyst that facilitates this new type of hydroamination mechanism.

The doubly linked dicyclopentadienyl complex {(η 5 -C 5 H 3 ) 2 (SiMe 2 ) 2 }Ru 2 (CO) 4 (1) reacts with H 2 in benzene under broad-spectrum UV-visible photolysis (254 < λ irr < 600 nm) to give the dinuclear {(η 5 -C 5 H 3 ) 2 (SiMe 2 ) 2 }Ru 2 (CO) 4 H 2 (2) and the tetranuclear clusters {(η 5 -C 5 H 3 ) 2 -(SiMe 2 ) 2 } 2 Ru 4 (CO) 3 H 4 (3) with a butterfly structure and {(η 5 -C 5 H 3 ) 2 (SiMe 2 ) 2 } 2 Ru 4 (CO) 4 H 4 (4) with a square-planar structure. The linked {(η 5 -C 5 H 3 ) 2 (SiMe 2 ) 2 } ligand is essential for the formation of the tetranuclear clusters (3 and 4), as unlinked analogues, Cp′ 2 Ru 2 (CO) 4 , give only di-and trinuclear products. Wavelength-dependent photolysis studies suggest that the first step in the reaction of 1 with H 2 involves metal-metal bond cleavage, which is supported by the all-terminal CO ligand geometry of 1, the independent synthesis of 2, and its photochemical reaction in the presence of H 2 to give 3 and 4.