Square-Planar and Butterfly Tetranuclear Ruthenium Clusters Incorporating the Doubly Linked Bis(dimethylsilylcyclopentadienyl) Ligand

Abstract

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.

Syntheses, Characterization, and Reactivity of Diruthenium Hydrido Complexes

“…The ruthenium dication in 2 lies on a crystallographic mirror plane that coincides with C­(Me) 2 groups of the dicyclopentadienyl ligand and the bridging hydride ligands. The Ru–Ru distance in 2 is 3.0183(4) Å, which is in the same range as other Ru–Ru single bonds (2.927–3.1107 Å) in complexes with a bridging hydride and a doubly linked Cp ligand . The assignment of a Ru–Ru bond helps explain the diamagnetic nature of the complex given that the formal oxidation state of each ruthenium is +3 with a d 5 electron configuration.…”

“…The Ru−Ru distance in 2 is 3.0183(4) Å, which is in the same range as other Ru−Ru single bonds (2.927−3.1107 Å) in complexes with a bridging hydride and a doubly linked Cp ligand. 9 The assignment of a Ru−Ru bond helps explain the diamagnetic nature of the complex given that the formal oxidation state of each ruthenium is +3 with a d 5 electron configuration. For the dicyclopentadienyl ligand, the angle between Cp planes is 139.45(7)°.…”

Synthesis of Ruthenium Carbonyl Complexes with Phosphine or Substituted Cp Ligands, and Their Activity in the Catalytic Deoxygenation of 1,2-Propanediol

“…The dinuclear complex{[(C 5 H 3 ) 2 (SiMe 2 ) 2 ]Ru 2 (CO) 4 (μ-H)} + BF 4 − , in which the two Cp ligands are joined by two SiMe 2 bridges, has been synthesized and studied in detail by Angelici and co-workers . This complex exhibits essentially no catalytic activity for deoxygenation of 1,2-propanediol, producing less than 2% n -propanol after 71 h (not shown in Figure ).…”

Photochemically Induced Metallization of Surface Silicon Using Dinuclear Metal Carbonyl Compounds. Anchoring of Ruthenium to a Si(111) Surface through Covalent Ru−Si Bond Formation

“…Silicon Metallization Mechanism. Near-UV photolysis of the diruthenium compounds Cp 2 Ru 2 (CO) 4 and [HB(pz) 3 ] 2 Ru 2 (CO) 4 in benzene solution leads to the disruption of the initial ruthenium dimer and production of the ruthenium-centered radicals CpRu(CO) 2 and [HB(pz) 3 ]Ru(CO) 2 due to population of the Ru−Ru σ* orbital. ,, The resulting ruthenium radicals are pivotal in the activation of the protective hydrogen layer associated with the Si(111) surface by hydrogen atom abstraction, which in turn produces reactive silicon radicals and the corresponding ruthenium hydrides CpRu(CO) 2 H and [HB(pz) 3 ]Ru(CO) 2 H . The transient silicon radicals are then free to participate in a radical combination reaction with the ruthenium-centered radicals, whose concentration far exceeds that of the surface silicon radicals, or react with adventitious oxygen.…”

“…Several dinuclear ruthenium carbonyl complexes were examined for their ability to functionalize hydrogen-terminated Si(111) surfaces. Optical excitation within the σ→σ* manifold belonging to the metal−metal bond in Cp 2 Ru 2 (CO) 4 (where Cp = η 5 -MeC 5 H 4 , η 5 -C 5 Me 5 ) and [HB(pz) 3 ] 2 Ru 2 (CO) 4 [where HB(pz) 3 = hydrotris(1-pyrazolyl)borate] leads to homolytic cleavage of the Ru−Ru bond and production of the reactive ruthenium-centered radicals CpRu(CO) 2 and [HB(pz) 3 ]Ru(CO) 2 . , The surface modification process has been studied by total internal reflection FTIR, X-ray photoelectron spectroscopy (XPS), and Rutherford backscattering spectrometry (RBS). The Ru−silicon bond is relatively stable toward air oxidation, and our data suggest that the steric properties of the surface-bound LRu(CO) 2 [where L = Cp, HB(pz) 3 ] entities strongly influence the degree to which the Si surface is covered.…”