Structurally Similar, Thermally Stable Copper(I), Silver(I), and Gold(I) Ethylene Complexes Supported by a Fluorinated Scorpionate

Treatment of Li­[PhBH₃] with excess 3-(C₂F₅)­PzH led to the B-phenylated tris­(pyrazolyl)­borate ligand as its lithium salt [PhB­(3-(C₂F₅)­Pz)₃]­Li. This ligand enabled the isolation of thermally stable group 11 metal ethylene adducts [PhB­(3-(C₂F₅)­Pz)₃]­M­(C₂H₄) (M = Au, Ag, Cu). They were characterized by spectroscopy and by X-ray crystallography. These ethylene adducts are structurally similar and feature three-coordinate trigonal-planar metal sites and a κ²-bonded tris­(pyrazolyl)­borate ligand. They are ideal for examining the trends involving ethylene complexes of the group 11 triad. The ethylene ¹³C NMR resonance of the [PhB­(3-(C₂F₅)­Pz)₃]­M­(C₂H₄) adducts in C₆D₁₂ appear at δ 58.9, 101.6, and 85.5 ppm, respectively, for M = Au, Ag, Cu. The M–C and M–N bond distances are largest in the silver complex and smallest in the copper complex

Structurally Similar, Thermally Stable Copper(I), Silver(I), and Gold(I) Ethylene Complexes Supported by a Fluorinated Scorpionate

Treatment of Li­[PhBH₃] with excess 3-(C₂F₅)­PzH led to the B-phenylated tris­(pyrazolyl)­borate ligand as its lithium salt [PhB­(3-(C₂F₅)­Pz)₃]­Li. This ligand enabled the isolation of thermally stable group 11 metal ethylene adducts [PhB­(3-(C₂F₅)­Pz)₃]­M­(C₂H₄) (M = Au, Ag, Cu). They were characterized by spectroscopy and by X-ray crystallography. These ethylene adducts are structurally similar and feature three-coordinate trigonal-planar metal sites and a κ²-bonded tris­(pyrazolyl)­borate ligand. They are ideal for examining the trends involving ethylene complexes of the group 11 triad. The ethylene ¹³C NMR resonance of the [PhB­(3-(C₂F₅)­Pz)₃]­M­(C₂H₄) adducts in C₆D₁₂ appear at δ 58.9, 101.6, and 85.5 ppm, respectively, for M = Au, Ag, Cu. The M–C and M–N bond distances are largest in the silver complex and smallest in the copper complex

Monoanionic, Bis(pyrazolyl)methylborate [(Ph₃B)CH(3,5-(CH₃)₂Pz)₂)]⁻ as a Supporting Ligand for Copper(I)-ethylene, <i>cis</i>-2-Butene, and Carbonyl Complexes

The monoanionic bidentate ligand [(Ph₃B)­CH­(3,5-(CH₃)₂Pz)₂)]⁻ has been prepared from lithium bis­(pyrazolyl)­methanide and triphenylborane. This useful new ligand is closely related to the well-established bis­(pyrazolyl)­borate and bis­(pyrazolyl)­methane ligands but has key differences to both analogues as well. The ethylene, <i>cis</i>-2-butene, and carbon monoxide adducts [(Ph₃B)­CH­(3,5-(CH₃)₂Pz)₂]­Cu­(L) (where L = C₂H₄, <i>cis</i>-CH₃HCCHCH₃, and CO) have been prepared from [(Ph₃B)­CH­(3,5-(CH₃)₂Pz)₂)]­Li­(THF), copper­(I) triflate, and the corresponding coligand. These complexes have been characterized by NMR spectroscopy and X-ray crystallography. In all cases the bis­(pyrazolyl) moiety is bound in κ²<i>N</i> fashion with the BPh₃ group rotated to sit over the metal center, sometimes coordinating to the metal via phenyl carbons as in [(Ph₃B)­CH­(3,5-(CH₃)₂Pz)₂)]­Li­(THF) and [(Ph₃B)­CH­(3,5-(CH₃)₂Pz)₂]­Cu­(CO) or simply hovering above the metal site as in [(Ph₃B)­CH­(3,5-(CH₃)₂Pz)₂)]­Cu­(C₂H₄) and [(Ph₃B)­CH­(3,5-(CH₃)₂Pz)₂)]­Cu­(<i>cis</i>-CH₃HCCHCH₃). The ¹³C and ¹H resonances of the ethylene carbon and protons of [(Ph₃B)­CH­(3,5-(CH₃)₂Pz)₂)]­Cu­(C₂H₄) appear at δ 81.0 and 3.71 ppm in CD₂Cl₂, respectively. The characteristic CO frequency for [(Ph₃B)­CH­(3,5-(CH₃)₂Pz)₂]­Cu­(CO) has been observed at υ̅ 2092 cm^–1 by infrared spectroscopy and is lower than that of free CO suggesting moderate M → CO π-back-donation. A detailed analysis of these complexes has been presented herein

Bonding in Binuclear Carbonyl Complexes M₂(CO)₉ (M = Fe, Ru, Os)

Quantum-chemical density functional theory calculations using the BP86 functional in conjunction with a triple-ζ basis set and dispersion correction by Grimme with Becke-Johnson damping D3­(BJ) were performed for the title molecules. The nature of the bonding was examined with the quantum theory of atoms in molecules (QTAIM) and natural bond order (NBO) methods and with the energy decomposition analysis in conjunction with the natural orbital for chemical valence (EDA-NOCV) analysis. The energetically lowest-lying form of Fe₂(CO)₉ is the triply bridged <i>D</i>_3<i>h</i> structure, whereas the most stable structures of Ru₂(CO)₉ and Os₂(CO)₉ are singly bridged <i>C</i>₂ species. The calculated reaction energies for the formation of the cyclic trinuclear carbonyls M₃(CO)₁₂ from the dinuclear carbonyls M₂(CO)₉ are in agreement with experiment, as the iron complex Fe₂(CO)₉ is thermodynamically stable in these reactions, but the heavier homologues Ru₂(CO)₉ and Os₂(CO)₉ are not. The metal–CO bond to the bridging CO ligands is stronger than the bonds to the terminal CO ligands. This holds for the triply bridged <i>D</i>_3<i>h</i> structures as well as for the singly bridged <i>C</i>₂ or <i>C</i>_2<i>v</i> species. The analysis of the orbital interactions with the help of the EDA-NOCV method suggests that the overall M→CO π backdonation is always stronger than the M←CO σ donation. The bridging carbonyls are more strongly bonded than the terminal CO ligands, and they are engaged in stronger σ donation and π backdonation, but the formation of bridging carbonyls requires reorganization energy, which may or may not be compensated by the stronger metal–ligand interactions. The lower-lying <i>D</i>_3<i>h</i> form of Fe₂(CO)₉ and <i>C</i>₂ structures of Ru₂(CO)₉ and Os₂(CO)₉ are due to a delicate balance of several forces

Coordination and Ligand Substitution Chemistry of Bis(cyclooctyne)copper(I)

Cationic bis­(alkyne)­copper­(I) carbonyl and bis­(alkyne)­copper­(I) isocyanide complexes have been synthesized from the precursor (cyclooctyne)₂CuBr. [Cu­(cyclo­octyne)₂(CO)]­[SbF₆] and [Cu­(cyclooctyne)₂(CN^tBu)]­[SbF₆] have trigonal-planar and three-coordinate copper centers. The copper carbonyl complex [Cu­(cyclooctyne)₂(CO)]­[SbF₆] displays its C–O stretching frequency in the “nonclassical” metal carbonyl region (2171 cm^–1), and the analogous copper­(I) isocyanide complex [Cu­(cyclooctyne)₂(CN^tBu)]­[SbF₆] also has an unusually high CN stretching band at 2230 cm^–1. The reaction of 3,5-Me₂C₆H₃NH₂ and 4-^tBuC₆H₄NH₂ with [Cu­(cyclooctyne)₂(CO)]­[SbF₆] led to CO displacement rather than addition to CO. CN^tBu reacts with [Cu­(cyclooctyne)₂(CO)]­[SbF₆] to afford [Cu­(cyclooctyne)₂(CN^tBu)]­[SbF₆]. The syntheses of [Cu­(cyclooctyne)­(CN^tBu)₂]­[SbF₆] and [Cu­(CN^tBu)₄]­[SbF₆] from the (cyclooctyne)₂CuBr precursor are also reported

Coordination and Ligand Substitution Chemistry of Bis(cyclooctyne)copper(I)

Cationic bis­(alkyne)­copper­(I) carbonyl and bis­(alkyne)­copper­(I) isocyanide complexes have been synthesized from the precursor (cyclooctyne)₂CuBr. [Cu­(cyclo­octyne)₂(CO)]­[SbF₆] and [Cu­(cyclooctyne)₂(CN^tBu)]­[SbF₆] have trigonal-planar and three-coordinate copper centers. The copper carbonyl complex [Cu­(cyclooctyne)₂(CO)]­[SbF₆] displays its C–O stretching frequency in the “nonclassical” metal carbonyl region (2171 cm^–1), and the analogous copper­(I) isocyanide complex [Cu­(cyclooctyne)₂(CN^tBu)]­[SbF₆] also has an unusually high CN stretching band at 2230 cm^–1. The reaction of 3,5-Me₂C₆H₃NH₂ and 4-^tBuC₆H₄NH₂ with [Cu­(cyclooctyne)₂(CO)]­[SbF₆] led to CO displacement rather than addition to CO. CN^tBu reacts with [Cu­(cyclooctyne)₂(CO)]­[SbF₆] to afford [Cu­(cyclooctyne)₂(CN^tBu)]­[SbF₆]. The syntheses of [Cu­(cyclooctyne)­(CN^tBu)₂]­[SbF₆] and [Cu­(CN^tBu)₄]­[SbF₆] from the (cyclooctyne)₂CuBr precursor are also reported

Gold-Mediated Expulsion of Dinitrogen from Organic Azides

Organoazides and their nitrogen expulsion chemistry have attracted the attention of many scientists because they serve as a useful source of nitrene fragments and interesting nitrene rearrangement products. Gold-mediated reactions are also of significant current interest. This manuscript describes several important discoveries based at the intersection of these fields. In particular, we report the first isolable gold organoazides ([(SIPr)­AuN­(1-Ad)­NN]­[SbF₆], [(SIPr)­AuN­(2-Ad)­NN]­[SbF₆] and [(SIPr)­AuN­(Cy)­NN]­[SbF₆]; SIPr = a <i>N</i>-heterocyclic carbene; 1-AdNNN = 1-azido­adamantane; 2-AdNNN = 2-azidoadamantane; CyNNN = azidocyclohexane), and their gold-mediated nitrogen expulsion chemistry, and the isolation of formal nitrene rearrangement products of “1-AdN”, “2-AdN” and “CyN” (including the elusive 4-azahomoadamant-3-ene) as their gold complexes. We have also performed a computational study to understand and explain the observed structure of gold-coordinated 1-AdNNN and 2-AdNNN and their nitrogen elimination pathways, which implies that the conversion of the organoazide complex to the imine is a concerted process without a nitrene/nitrenoid intermediate. Kinetic studies of [(SIPr)­AuN­(2-Ad)­NN]­[SbF₆] from 30 to 50 °C indicate that nitrogen elimination is a first-order process. The experimentally determined activation parameters are in good agreement with the calculated values

Isolable, Copper(I) Dicarbonyl Complexes Supported by <i>N</i>‑Heterocyclic Carbenes

Cationic copper­(I) dicarbonyl complexes supported by <i>N</i>-heterocyclic carbene ligands, SIPr and IPr*, have been synthesized. [(SIPr)­Cu­(CO)₂]­[SbF₆] and [(IPr*)­Cu­(CO)₂]­[SbF₆] have a trigonal planar, three-coordinate copper atom with an average Cu–CO distance of 1.915 Å and display C–O stretching frequencies higher than that of the free CO (2143 cm^–1). The high CO stretching frequencies suggest that the Cu­(I)–CO interaction in these cationic adducts is dominated by electrostatic and OC → Cu σ-donor components. [(SIPr)­Cu­(CO)₂]­[SbF₆] and [(IPr*)­Cu­(CO)₂]­[SbF₆] readily form the corresponding [(SIPr)­Cu­(CO)­(H₂O)]­[SbF₆] and [(IPr*)­Cu­(CO)­(H₂O)]­[SbF₆] with loss of a CO even with traces of water, but they can be converted back to the dicarbonyl adducts using excess CO. The synthesis and structure of [(IPr*)­Cu­(H₂O)]­[SbF₆] are also reported. It is a two-coordinate copper adduct with a Cu–O distance of 1.874(2) Å. It reacts with excess CO to form [(IPr*)­Cu­(CO)₂]­[SbF₆]

Gold-Mediated Expulsion of Dinitrogen from Organic Azides

Organoazides and their nitrogen expulsion chemistry have attracted the attention of many scientists because they serve as a useful source of nitrene fragments and interesting nitrene rearrangement products. Gold-mediated reactions are also of significant current interest. This manuscript describes several important discoveries based at the intersection of these fields. In particular, we report the first isolable gold organoazides ([(SIPr)­AuN­(1-Ad)­NN]­[SbF₆], [(SIPr)­AuN­(2-Ad)­NN]­[SbF₆] and [(SIPr)­AuN­(Cy)­NN]­[SbF₆]; SIPr = a <i>N</i>-heterocyclic carbene; 1-AdNNN = 1-azido­adamantane; 2-AdNNN = 2-azidoadamantane; CyNNN = azidocyclohexane), and their gold-mediated nitrogen expulsion chemistry, and the isolation of formal nitrene rearrangement products of “1-AdN”, “2-AdN” and “CyN” (including the elusive 4-azahomoadamant-3-ene) as their gold complexes. We have also performed a computational study to understand and explain the observed structure of gold-coordinated 1-AdNNN and 2-AdNNN and their nitrogen elimination pathways, which implies that the conversion of the organoazide complex to the imine is a concerted process without a nitrene/nitrenoid intermediate. Kinetic studies of [(SIPr)­AuN­(2-Ad)­NN]­[SbF₆] from 30 to 50 °C indicate that nitrogen elimination is a first-order process. The experimentally determined activation parameters are in good agreement with the calculated values

Copper(I) Ethylene Complexes Supported by 1,3,5-Triazapentadienyl Ligands with Electron-Withdrawing Groups

The fluorinated 1,3,5-triazapentadienyl ligands [N­{(C₃F₇)­C­(2-(NO₂)­C₆H₄)­N}₂]⁻, [N­{(C₃F₇)­C­(4-(NO₂)­C₆H₄)­N}₂]⁻, [N­{(C₃F₇)­C­(2-(CF₃)­C₆H₄)­N}₂]⁻, and [N­{(C₃F₇)­C­(2-F,6-(CF₃)­C₆H₃)­N}₂]⁻ have been used as supporting ligands in copper­(I) ethylene chemistry. [N­{(C₃F₇)­C­(2-(NO₂)­C₆H₄)­N}₂]­Cu­(C₂H₄) (<b>7</b>), [N­{(C₃F₇)­C­(4-(NO₂)­C₆H₄)­N}₂]­Cu­(C₂H₄) (<b>8</b>), [N­{(C₃F₇)­C­(2-(CF₃)­C₆H₄)­N}₂]­Cu­(C₂H₄) (<b>9</b>), and [N­{(C₃F₇)­C­(2-F,6-(CF₃)­C₆H₃)­N}₂]­Cu­(C₂H₄) (<b>10</b>) are easily isolable, thermally stable solids and display their ethylene proton and carbon resonances in the δ 3.68–3.48 and 85.2–87.6 ppm regions, respectively. X-ray crystal structures reveal that <b>7</b>–<b>10</b> feature trigonal-planar copper sites and κ²-bonded, U-shaped triazapentadienyl ligands. The Cu­(I) carbonyl adducts [N­{(C₃F₇)­C­(2-(NO₂)­C₆H₄)­N}₂]­Cu­(CO)­(NCCH₃) (<b>16</b>) and [N­{(C₃F₇)­C­(4-(NO₂)­C₆H₄)­N}₂]­Cu­(CO)­(NCCH₃) (<b>17</b>) have also been synthesized, and they have pseudotetrahedral copper sites. The CO stretching frequencies of the compounds <b>16</b> and <b>17</b> and ethylene ¹³C NMR chemical shift data of <b>7</b>–<b>10</b> suggest that these molecules have rather acidic copper sites and weakly donating triazapentadienyl ligands