Syntheses, Characterization, and Reactivity of Diruthenium Hydrido Complexes

The reaction of [<i>cis-</i>{(η⁵-C₅H₃)₂(CMe₂)₂}­Ru₂(κ²-4,4′-di-<i>tert</i>-butyl-2,2′-bipyridine)₂­(MeCN)₂]­[OTf]₂, <b>1</b>, with H₂ yields a μ-dihydrido complex, [<i>cis-</i>{(η⁵-C₅H₃)₂(CMe₂)₂}­Ru₂(κ²-4,4′-di-<i>tert</i>-butyl-2,2′-bipyridine)₂­(μ-H)₂]­[OTf]₂, <b>2</b>, in 79% yield. The reaction of <b>2</b> with Et₃SiH affords a mono<i>-</i>μ-hydrido complex, <i>cis-</i>{(η⁵-C₅H₃)₂(CMe₂)₂}­Ru₂(κ²-4,4′-di-<i>tert</i>-butyl-2,2′-bipyridine)₂­(μ-H)]­[OTf], <b>3</b>. The reaction of either <b>2</b> or <b>3</b> (1–2 mol %) with C₆H₆ and Et₃SiH results in the catalytic cleavage of the C–H bond in benzene along with the cleavage of the Si–Et bond to form PhEt₂SiH (23–27% conversion) and C₂H₆. The reaction of <b>2</b> or <b>3</b> (1 mol %) with THF and Et₃SiH results in the cleavage of the C–H bond in THF followed by the insertion of the SiEt₂ group into the C–O bond, forming 2,2-diethyl-1-oxa-2-silacyclohexane (14% conversion) as one of the products

Syntheses, Characterization, and Reactivity of Diruthenium Hydrido Complexes

The reaction of [<i>cis-</i>{(η⁵-C₅H₃)₂(CMe₂)₂}­Ru₂(κ²-4,4′-di-<i>tert</i>-butyl-2,2′-bipyridine)₂­(MeCN)₂]­[OTf]₂, <b>1</b>, with H₂ yields a μ-dihydrido complex, [<i>cis-</i>{(η⁵-C₅H₃)₂(CMe₂)₂}­Ru₂(κ²-4,4′-di-<i>tert</i>-butyl-2,2′-bipyridine)₂­(μ-H)₂]­[OTf]₂, <b>2</b>, in 79% yield. The reaction of <b>2</b> with Et₃SiH affords a mono<i>-</i>μ-hydrido complex, <i>cis-</i>{(η⁵-C₅H₃)₂(CMe₂)₂}­Ru₂(κ²-4,4′-di-<i>tert</i>-butyl-2,2′-bipyridine)₂­(μ-H)]­[OTf], <b>3</b>. The reaction of either <b>2</b> or <b>3</b> (1–2 mol %) with C₆H₆ and Et₃SiH results in the catalytic cleavage of the C–H bond in benzene along with the cleavage of the Si–Et bond to form PhEt₂SiH (23–27% conversion) and C₂H₆. The reaction of <b>2</b> or <b>3</b> (1 mol %) with THF and Et₃SiH results in the cleavage of the C–H bond in THF followed by the insertion of the SiEt₂ group into the C–O bond, forming 2,2-diethyl-1-oxa-2-silacyclohexane (14% conversion) as one of the products

Selective Dialkylation of a Doubly Linked Dicyclopentadiene Ligand and the Ensuing Ruthenium Complexes

The selective alkylation (Me or <i>tert</i>-butyl) of a doubly linked dicyclopentadiene ligand is presented. The reaction of (C₅H₃(<i>t</i>-Bu))₂(CMe₂)₂ (<b>4a</b>,<b>b</b>), the di-<i>tert</i>-butyl-substituted ligand, with RuCl₃·3H₂O in MeOH at 140 °C for 15 min, followed by heating in CHCl₃, gave the chloro-bridged complex <i>cis</i>-{(η⁵-C₅H₂(<i>t</i>-Bu))₂(CMe₂)₂}­Ru₂(μ-Cl)₂Cl₂ (<b>5</b>) in 28% yield. Reduction of <b>5</b> with Zn in MeCN gave the chloro-bridged tetrakis­(acetonitrile) complex <i>cis</i>-[{(η⁵-C₅H₂(<i>t</i>-Bu))₂(CMe₂)₂}­Ru₂(MeCN)₄(μ-Cl)]⁺ (<b>6</b>) in 62% yield. Addition of AgOTf to <b>6</b> in MeCN removed the bridging chloro ligand and gave [<i>cis</i>-{(η⁵-C₅H₂(<i>t</i>-Bu))₂(CMe₂)₂}­Ru₂(MeCN)₆]­[OTf]₂ (<b>7</b>) in 38% yield. The X-ray crystal structures of <b>5</b> and <b>6</b> are reported

Diruthenium Naphthalene and Anthracene Complexes Containing a Doubly Linked Dicyclopentadienyl Ligand

The reaction of <i>cis</i>-{(η⁵-C₅H₃)₂(CMe₂)₂}­Ru₂(CO)₄Br₂ with naphthalene affords the <i>syn</i>-facial [<i>cis</i>-{(η⁵-C₅H₃)₂(CMe₂)₂}­Ru₂(μ-η⁶,η⁶-C₁₀H₈)]­[OTf]₂, (<b>2</b>^<b>2+</b>), a complex that appears to be two electrons short of the 18-electron rule. Density functional theory (DFT) calculations suggest that the Ru atoms satisfy their missing valence by a combination of a weak metal–metal bond and sharing electrons from the central π bond of the naphthalene. The one-electron reduction of <b>2</b>^<b>2+</b> yields <b>2</b>^<b>+</b>, a Class II mixed-valence complex, while the two-electron reduction of <b>2</b>^<b>2+</b> causes a hapticity change from η⁶ to η⁴ on one of the naphthalene rings and yields <i>cis</i>-{(η⁵-C₅H₃)₂(CMe₂)₂}­Ru₂(μ-η⁶,η⁴-C₁₀H₈<b>)</b> (<b>2</b>^<b>0</b>), a zwitterionic complex. The DFT calculations predict that the <i>C</i>_<i>s</i> isomer of <b>2⁰</b> is 4.69 kcal/mol lower in energy than the <i>C</i>_2<i>v</i> isomer, which is a transition state. Reaction of <i>cis</i>-{(η⁵-C₅H₃)₂(CMe₂)₂}­Ru₂(CO)₄Br₂ with anthracene affords the analogous <i>syn</i>-facial anthracene complex, [<i>cis</i>-{(η⁵-C₅H₃)₂(CMe₂)₂}­Ru₂(μ-η⁶,η⁶-C₁₄H₁₀)]­[OTf]₂, (<b>4</b>), and the tetranuclear dianthracene complex, [<i>cis</i>-{(η⁵-C₅H₃)₂(CMe₂)₂}­Ru₂(μ-η⁶,η⁶-C₁₄H₁₀)]₂[OTf]₄, (<b>5</b>). <b>2</b>^<b>2+</b>, <b>2</b>^<b>0</b>, and <b>5</b> were structurally characterized by X-ray diffraction

Diruthenium Naphthalene and Anthracene Complexes Containing a Doubly Linked Dicyclopentadienyl Ligand

The reaction of <i>cis</i>-{(η⁵-C₅H₃)₂(CMe₂)₂}­Ru₂(CO)₄Br₂ with naphthalene affords the <i>syn</i>-facial [<i>cis</i>-{(η⁵-C₅H₃)₂(CMe₂)₂}­Ru₂(μ-η⁶,η⁶-C₁₀H₈)]­[OTf]₂, (<b>2</b>^<b>2+</b>), a complex that appears to be two electrons short of the 18-electron rule. Density functional theory (DFT) calculations suggest that the Ru atoms satisfy their missing valence by a combination of a weak metal–metal bond and sharing electrons from the central π bond of the naphthalene. The one-electron reduction of <b>2</b>^<b>2+</b> yields <b>2</b>^<b>+</b>, a Class II mixed-valence complex, while the two-electron reduction of <b>2</b>^<b>2+</b> causes a hapticity change from η⁶ to η⁴ on one of the naphthalene rings and yields <i>cis</i>-{(η⁵-C₅H₃)₂(CMe₂)₂}­Ru₂(μ-η⁶,η⁴-C₁₀H₈<b>)</b> (<b>2</b>^<b>0</b>), a zwitterionic complex. The DFT calculations predict that the <i>C</i>_<i>s</i> isomer of <b>2⁰</b> is 4.69 kcal/mol lower in energy than the <i>C</i>_2<i>v</i> isomer, which is a transition state. Reaction of <i>cis</i>-{(η⁵-C₅H₃)₂(CMe₂)₂}­Ru₂(CO)₄Br₂ with anthracene affords the analogous <i>syn</i>-facial anthracene complex, [<i>cis</i>-{(η⁵-C₅H₃)₂(CMe₂)₂}­Ru₂(μ-η⁶,η⁶-C₁₄H₁₀)]­[OTf]₂, (<b>4</b>), and the tetranuclear dianthracene complex, [<i>cis</i>-{(η⁵-C₅H₃)₂(CMe₂)₂}­Ru₂(μ-η⁶,η⁶-C₁₄H₁₀)]₂[OTf]₄, (<b>5</b>). <b>2</b>^<b>2+</b>, <b>2</b>^<b>0</b>, and <b>5</b> were structurally characterized by X-ray diffraction