Reactivity of Triruthenium Furyne and Thiophyne Clusters: Multiple Additions of Thiolato and Selenolato Ligands through Oxidative Addition of S–H and Se–H Bonds

Reactions of 50-electron furyne and thiophyne clusters Ru₃(CO)₇(μ-H)­(μ₃-η²-C₄H₂E)­{μ-P­(C₄H₃E)₂}­(μ-dppm) (<b>1</b>, <b>2</b>; E = O, S) with thiols, dithiols, and benzeneselenol leads to the oxidative addition of the E–H bonds followed by concomitant elimination of the alkyne (probably as the alkene) to afford a range of new thiolato and selenolato triruthenium complexes. Addition of PhSH or ⁱPrSH in boiling benzene affords the 48-electron clusters Ru₃(CO)₅(μ-SR)₂{μ-P­(C₄H₃E)₂}­(μ-dppm)­(μ-H) (<b>3</b>–<b>6</b>; E = O, S; R = Ph, ⁱPr) resulting from the addition of 2 equiv of thiol. In contrast, analogous reactions with 1,2-ethanedithiol and 1,3-propanedithiol yield the 50-electron clusters Ru₃(CO)₃{μ-S­(CH₂)_<i>n</i>S)₂{μ-P­(C₄H₃E)₂}­(μ-dppm)­(μ-H) (<b>7</b>–<b>10</b>; E = O, S; <i>n</i> = 2, 3), in which four S–H bonds have been activated. A similar multiple addition reaction is seen upon addition of PhSeH to <b>1</b>, affording the tetraselenolato complexes Ru₃(CO)₄(κ¹-SePh)­(μ-SePh)₃{μ-P­(C₄H₃O)₂}­(μ-dppm)­(μ-H) (<b>11</b>) and Ru₃(CO)₃(μ-SePh)₄{μ-P­(C₄H₃O)₂}­(μ-dppm)­(μ-H) (<b>12</b>). Reaction of <b>2</b> with PhSeH gave the tetraselenolato complex Ru₃(CO)₄(κ¹-SePh)­(μ-SePh)₃{μ-P­(C₄H₃S)₂}­(μ-dppm)­(μ-H) (<b>13</b>) together with bis­(seleno)-capped Ru₃(CO)₅{PPh­(C₄H₃S)₂}­(μ₃-Se)₂(μ-SePh)₂(μ-dppm) (<b>14</b>) resulting from further cleavage of two selenium–carbon bonds and formation of a new carbon–phosphorus bond. The new clusters have been characterized by a combination of analytical and spectroscopic methods, and the molecular structures of <b>3</b>, <b>4</b>, <b>7</b>, <b>8</b>, and <b>11</b> have been determined by single-crystal X-ray diffraction studies. Complexes <b>7</b>–<b>10</b> are examples of 50-electron clusters containing three apparent metal–metal bonds; however, DFT calculations carried out for <b>7</b> show that the longest metal–metal interaction of 3.119 Å is actually held in place by the bridging thiolato and diphosphine ligands and does not represent a direct metal–metal bonding interaction

Following the Creation of Active Gold Nanocatalysts from Phosphine-Stabilized Molecular Clusters

The phosphine-stabilized gold cluster [Au₆(Ph₂P-<i>o</i>-tolyl)₆]­(NO₃)₂ is converted into an active nanocatalyst for the oxidation of benzyl alcohol through low-temperature peroxide-assisted removal of the phosphines, avoiding the high-temperature calcination process. The process was monitored using in situ X-ray absorption spectroscopy, which revealed that after a certain period of the reaction with tertiary butyl hydrogen peroxide, the phosphine ligands are removed to form nanoparticles of gold which matches with the induction period seen in the catalytic reaction. Density functional theory calculations show that the energies required to remove the ligands from the [Au₆L_<i>n</i>]²⁺ increase significantly with successive removal steps, suggesting that the process does not occur at once but sequentially. The calculations also reveal that ligand removal is accompanied by dramatic rearrangements in the topology of the cluster core

Ring-Closing Metathesis and Nanoparticle Formation Based on Diallyldithiocarbamate Complexes of Gold(I): Synthetic, Structural, and Computational Studies

The gold­(I) complexes [Au­{S₂CN­(CH₂CHCH₂)₂}­(L)] [L = PPh₃, PCy₃, PMe₃, CN^<i>t</i>Bu, IDip] are prepared from KS₂CN­(CH₂CHCH₂)₂ and [(L)­AuCl]. The compounds [L₂(AuCl)₂] (L₂ = dppa, dppf) yield [(L₂)­{AuS₂CN­(CH₂CHCH₂)₂}₂], while the cyclic complex [(dppm)­{Au₂S₂CN­(CH₂CHCH₂)₂}]­OTf is obtained from [dppm­(AuCl)₂] and AgOTf followed by KS₂CN­(CH₂CHCH₂)₂. The compound [Au₂{S₂CN­(CH₂CHCH₂)₂}₂] is prepared from [(tht)­AuCl] (tht = tetrahydrothiophene) and the diallyldithiocarbamate ligand. This product ring-closes with [Ru­(CHPh)­Cl₂­(SIMes)­(PCy₃)] to yield [Au₂(S₂CNC₄H₆)₂], whereas ring-closing of [Au­{S₂CN­(CH₂CHCH₂)₂}­(PR₃)] fails. Warming [Au₂{S₂CN­(CH₂CHCH₂)₂}₂] results in formation of gold nanoparticles with diallydithiocarbamate surface units, while heating [Au₂(S₂CNC₄H₆)₂] with NaBH₄ results in nanoparticles with 3-pyrroline dithiocarbamate surface units. Larger nanoparticles with the same surface units are prepared by citrate reduction of HAuCl₄ followed by addition of the dithiocarbamate. The diallydithiocarbamate-functionalized nanoparticles undergo ring-closing metathesis using [Ru­(CHC₆H₄O^<i>i</i>Pr-2)­Cl₂(SIMes)]. The interaction between the dithiocarbamate units and the gold surface is explored using computational methods to reveal no need for a countercation. Preliminary calculations indicate that the Au–S interactions are substantially different from those established in theoretical and experimental studies on thiolate-coated nanoparticles. Structural studies are reported for [Au­{S₂CN­(CH₂CHCH₂)₂}­(PPh₃)] and [Au₂{S₂CN­(CH₂CHCH₂)₂}₂]. In the latter, exceptionally short intermolecular aurophilic interactions are observed

Ring-Closing Metathesis and Nanoparticle Formation Based on Diallyldithiocarbamate Complexes of Gold(I): Synthetic, Structural, and Computational Studies

The gold­(I) complexes [Au­{S₂CN­(CH₂CHCH₂)₂}­(L)] [L = PPh₃, PCy₃, PMe₃, CN^<i>t</i>Bu, IDip] are prepared from KS₂CN­(CH₂CHCH₂)₂ and [(L)­AuCl]. The compounds [L₂(AuCl)₂] (L₂ = dppa, dppf) yield [(L₂)­{AuS₂CN­(CH₂CHCH₂)₂}₂], while the cyclic complex [(dppm)­{Au₂S₂CN­(CH₂CHCH₂)₂}]­OTf is obtained from [dppm­(AuCl)₂] and AgOTf followed by KS₂CN­(CH₂CHCH₂)₂. The compound [Au₂{S₂CN­(CH₂CHCH₂)₂}₂] is prepared from [(tht)­AuCl] (tht = tetrahydrothiophene) and the diallyldithiocarbamate ligand. This product ring-closes with [Ru­(CHPh)­Cl₂­(SIMes)­(PCy₃)] to yield [Au₂(S₂CNC₄H₆)₂], whereas ring-closing of [Au­{S₂CN­(CH₂CHCH₂)₂}­(PR₃)] fails. Warming [Au₂{S₂CN­(CH₂CHCH₂)₂}₂] results in formation of gold nanoparticles with diallydithiocarbamate surface units, while heating [Au₂(S₂CNC₄H₆)₂] with NaBH₄ results in nanoparticles with 3-pyrroline dithiocarbamate surface units. Larger nanoparticles with the same surface units are prepared by citrate reduction of HAuCl₄ followed by addition of the dithiocarbamate. The diallydithiocarbamate-functionalized nanoparticles undergo ring-closing metathesis using [Ru­(CHC₆H₄O^<i>i</i>Pr-2)­Cl₂(SIMes)]. The interaction between the dithiocarbamate units and the gold surface is explored using computational methods to reveal no need for a countercation. Preliminary calculations indicate that the Au–S interactions are substantially different from those established in theoretical and experimental studies on thiolate-coated nanoparticles. Structural studies are reported for [Au­{S₂CN­(CH₂CHCH₂)₂}­(PPh₃)] and [Au₂{S₂CN­(CH₂CHCH₂)₂}₂]. In the latter, exceptionally short intermolecular aurophilic interactions are observed

Active Nature of Primary Amines during Thermal Decomposition of Nickel Dithiocarbamates to Nickel Sulfide Nanoparticles

Although [Ni­(S₂CNBuⁱ₂)₂] is stable at high temperatures in a range of solvents, solvothermal decomposition occurs at 145 °C in oleylamine to give pure NiS nanoparticles, while in <i>n</i>-hexylamine at 120 °C a mixture of Ni₃S₄ (polydymite) and NiS results. A combined experimental and theoretical study gives mechanistic insight into the decomposition process and can be used to account for the observed differences. Upon dissolution in the primary amine, octahedral <i>trans-</i>[Ni­(S₂CNBuⁱ₂)₂(RNH₂)₂] result as shown by <i>in situ</i> XANES and EXAFS and confirmed by DFT calculations. Heating to 90–100 °C leads to changes consistent with the formation of amide-exchange products, [Ni­(S₂CNBuⁱ₂)­{S₂CN­(H)­R}] and/or [Ni­{S₂CN­(H)­R}₂]. DFT modeling shows that exchange occurs via nucleophilic attack of the primary amine at the backbone carbon of the dithiocarbamate ligand(s). With hexylamine, amide-exchange is facile and significant amounts of [Ni­{S₂CN­(H)­Hex}₂] are formed prior to decomposition, but with oleylamine, exchange is slower and [Ni­(S₂CNBuⁱ₂)­{S₂CN­(H)­Oleyl}] is the active reaction component. The primary amine dithiocarbamate complexes decompose rapidly at ca. 100 °C to afford nickel sulfides, even in the absence of primary amine, as shown from thermal decomposition studies of [Ni­{S₂CN­(H)­Hex}₂]. DFT modeling of [Ni­{S₂CN­(H)­R}₂] shows that proton migration from nitrogen to sulfur leads to formation of a dithiocarbimate (S₂CNR) which loses isothiocyanate (RNCS) to give dimeric nickel thiolate complexes [Ni­{S₂CN­(H)­R}­(μ-SH)]₂. These intermediates can either lose dithiocarbamate(s) or extrude further isothiocyanate to afford (probably amine-stabilized) nickel thiolate building blocks, which aggregate to give the observed nickel sulfide nanoparticles. Decomposition of the single or double amide-exchange products can be differentiated, and thus it is the different rates of amide-exchange that account primarily for the formation of the observed nanoparticulate nickel sulfides