Catalytic Hydrodefluorination of Fluoroarenes Using Ru(IMe₄)₂L₂H₂ (IMe₄ = 1,3,4,5-Tetramethylimidazol-2-ylidene; L₂ = (PPh₃)₂, dppe, dppp, dppm) Complexes

The all-trans isomer of Ru­(IMe₄)₂(PPh₃)₂H₂ (<b>ttt-4</b>; IMe₄ = 1,3,4,5-tetramethylimidazol-2-ylidene) reacts with C₆F₆ at 70 °C to afford the hydride fluoride complex Ru­(IMe₄)₂(PPh₃)₂HF (<b>ttt</b>-<b>6</b>). At room temperature, <b>ttt</b>-<b>6</b> reacts with Et₃SiH to give a mixture of products, one of which is assigned as the silyl trihydride complex Ru­(IMe₄)₂(PPh₃)­(SiEt₃)­H₃ (<b>8</b>) by comparison to the isolated and structurally characterized analogue Ru­(IMe₄)₂(PPh₃)­(SiPh₃)­H₃ (<b>9</b>). As <b>ttt-4</b> was re-formed cleanly upon heating <b>ttt</b>-<b>6</b> with Et₃SiH, it was tested in the catalytic hydrodefluorination (HDF) of C₆F₆ (10 mol %, 90 °C), along with <b>9</b>, Ru­(IMe₄)₂(P-P)­HF (P-P = Ph₂P­(CH₂)₂PPh₂ (dppe, <b>cct</b>-<b>13</b>), Ph₂P­(CH₂)₃PPh₂ (dppp, <b>cct</b>-<b>14</b>), Ph₂PCH₂PPh₂ (dppm, <b>cct</b>-<b>15</b>)), Ru­(IEt₂Me₂)₂(PPh₃)₂HF (<b>cct</b>-<b>7</b>; IEt₂Me₂ = 1,3-diethyl-4,5-dimethylimidazol-2-ylidene)), and Ru­(IEt₂Me₂)₂(dppe)₂HF (<b>cct</b>-<b>16</b>) for comparison. Both <b>cct</b>-<b>13</b> and <b>cct</b>-<b>14</b> brought about near-quantitative conversion to C₆FH₅ in 24 h, in comparison to ca. 50% conversion with <b>ttt-4</b> in 144 h

Copper Diamidocarbene Complexes: Characterization of Monomeric to Tetrameric Species

Treatment of CuCl with 1 equiv of the in situ prepared <i>N</i>-mesityl-substituted diamidocarbene 6-MesDAC produced a mixture of the dimeric and trimeric copper complexes [(6-MesDAC)­CuCl]₂ (<b>1</b>) and [(6-MesDAC)₂(CuCl)₃] (<b>2</b>). Combining CuCl with isolated, free 6-MesDAC in 1:1 and 3:2 ratios gave just <b>1</b> and <b>2</b>, respectively, while increasing the ratio to >5:1 allowed the isolation of small amounts of the tetrameric copper complex [(6-MesDAC)₂(CuCl)₄] (<b>3</b>). Efforts to bring about metathesis reactions of <b>1</b> with MO^tBu (M = Li, Na, K) proved successful only for M = Li to afford the spectroscopically characterized ate product [(6-MesDAC)­CuCl·LiO^tBu·2THF] (<b>5</b>). Attempts to crystallize this species instead gave a 1:1 mixture of <b>1</b> and the monomer [(6-MesDAC)­CuCl] (<b>6</b>). The X-ray structures of <b>1</b>–<b>3</b> and <b>1</b> + <b>6</b>, along with the cation [Cu­(6-MesDAC)₂]⁺ (<b>4</b>), have been determined

Synthesis and Small Molecule Reactivity of <i>trans</i>-Dihydride Isomers of Ru(NHC)₂(PPh₃)₂H₂ (NHC = N‑Heterocyclic Carbene)

Addition of IMe₄ (1,3,4,5-tetra­methyl­imidazol-2-ylidene) to Ru­(PPh₃)₃­HCl (in the presence of H₂) or Ru­(PPh₃)₄­H₂ gave the all-trans isomer of Ru­(IMe₄)₂­(PPh₃)₂­H₂ (<b>1a</b>), whereas 1,3-diethyl-4,5-dimethylimidazol-2-ylidene (IEt₂­Me₂) reacted with Ru­(PPh₃)₄­H₂ to form <i>cis</i>,<i>cis</i>,<i>trans</i>-Ru­(IEt₂­Me₂)₂­(PPh₃)₂­H₂ (<b>2b</b>). H/D exchange of <b>1a</b> with C₆D₆ (elevated temperature) or D₂ (room temperature) gave Ru­(IMe₄)₂­(PPh₃)₂­HD (<b>1a-HD</b>) and Ru­(IMe₄)₂­(PPh₃)₂­D₂ (<b>1a-D</b>_<b>2</b>). CO reacted with <b>1a</b> to give a mixture of Ru­(IMe₄)₂­(PPh₃)­(CO)­H₂ (<b>3</b>) and Ru­(IMe₄)₂­(CO)₃ (<b>4</b>); <b>2b</b> reacted in a similar manner, although more slowly, allowing isolation of the monocarbonyl species Ru­(IEt₂­Me₂)₂­(PPh₃)­(CO)­H₂ (<b>5</b>). Insertion of CO₂ into one of the Ru–H bonds of <b>1a</b> and <b>2b</b> generated mixtures of major and minor isomers of the κ²-formate complexes Ru­(IMe₄)₂­(PPh₃)­(OCHO)H (<b>7</b>/<b>8</b>) and Ru­(IEt₂Me₂)₂(PPh₃)­(OCHO)H (<b>9</b>/<b>10</b>). The hydridic nature of <b>1a</b> and <b>2b</b> was apparent by their reactivity toward MeI, which gave [Ru­(IMe₄)₂­(PPh₃)₂­H]I (<b>11</b>), Ru­(IEt₂­Me₂)₂­(PPh₃)­HI (<b>12</b>), [Ru­(IEt₂­Me₂)₂­(PPh₃)₂­H]I (<b>13</b>), and Ru­(IEt₂­Me₂)­(PPh₃)₂­HI (<b>14</b>). Complexes <b>1a</b>, <b>2b</b>, <b>5</b>, <b>9</b>, <b>11</b>, <b>13</b>, and <b>14</b> were structurally characterized

Rh–FHF and Rh–F Complexes Containing Small <i>N</i>‑Alkyl Substituted Six-Membered Ring N‑Heterocyclic Carbenes

Heating the six-membered ring N-heterocyclic carbenes 6-Me and 6-Et with Rh­(PPh₃)₄H afforded the rhodium monocarbene hydride complexes Rh­(6-NHC)­(PPh₃)₂H as a mixture of cis- and trans-P,P isomers (<b>4a</b>/<b>b</b>, NHC = 6-Me; ratio = 1:20; <b>5a</b>/<b>b</b>, NHC = 6-Et; ratio = 1:9). Reaction of <b>4a</b>/<b>b</b> with Et₃N·3HF gave only the trans-P,P isomer of the bifluoride complex Rh­(6-Me)­(PPh₃)₂(FHF) (<b>6b</b>), whereas <b>5a</b>/<b>b</b> reacted to form Rh­(6-Et)­(PPh₃)₂(FHF) as a mixture of cis- and trans-phosphine isomers (<b>7a</b>/<b>b</b>). Variable temperature ¹H and ¹⁹F NMR spectroscopy showed that <b>6b</b> and the previously reported 6-ⁱPr carbene analogue cis-Rh­(6-ⁱPr)­(PPh₃)₂(FHF) (<b>2a</b>; Organometallics 2012, 41, 8584) were fluxional in solution. ¹⁹F Magnetization transfer experiments revealed F exchange in both compounds and afforded similar Δ<i>H</i>^⧧ values (<b>2a</b>, 51 ± 5 kJ mol^–1; <b>6b</b>, 60 ± 6 kJ mol^–1) but somewhat different values of Δ<i>S</i>^⧧ (<b>2a</b>, −70 ± 17 J mol^–1 K^–1; <b>6b</b>, −27 ± 18 J mol^–1 K^–1). The fluoride complexes cis-Rh­(6-Me)­(PPh₃)₂F (<b>8a</b>), cis-/trans-Rh­(6-Et)­(PPh₃)₂F (<b>9a</b>/<b>b</b>), and the previously reported 6-ⁱPr analogue <b>3a</b> could be formed upon C–F activation of CF₃CFCF₂ by <b>4a</b>/<b>b</b>, <b>5a</b>/<b>b</b>, and Rh­(6-ⁱPr)­(PPh₃)₂H (<b>1a</b>/<b>b</b>), respectively. Complex <b>3a</b> reacted slowly with H₂ to partially reform <b>1a</b>/<b>b</b> but rapidly with CO to give Rh­(6-ⁱPr)­(PPh₃)­(CO)F (<b>10</b>) and Rh­(PPh₃)₂(CO)­F, and also quickly with Me₃SiCF₃ to form cis-Rh­(6-ⁱPr)­(PPh₃)₂(CF₃) (<b>11a</b>). Complexes <b>4b</b>, <b>5b</b>, <b>6b</b>, <b>7b</b>, and <b>11a</b> were structurally characterized

Ring-Expanded N‑Heterocyclic Carbene Complexes of Rhodium with Bifluoride, Fluoride, and Fluoroaryl Ligands

Thermolysis of Rh­(PPh₃)₄H in the presence of the six-membered N-heterocyclic carbene 1,3-bis­(2-propyl)-3,4,5,6-tetrahydropyrimidin-2-ylidine (6-ⁱPr) gave the monocarbene complex Rh­(6-ⁱPr)­(PPh₃)₂H as a 1:2 mixture of the cis- and trans-phosphine isomers <b>1a</b> and <b>1b</b>. This same isomeric mixture was formed as the ultimate product from treating Rh­(PPh₃)₃(CO)H with 6-ⁱPr at room temperature, although pathways involving both CO and PPh₃ loss were observed at initial times. Treatment of <b>1a</b>/<b>1b</b> with Et₃N·3HF generated the bifluoride complex <i>cis</i>-Rh­(6-ⁱPr)­(PPh₃)₂(FHF) (<b>2a</b>), which upon stirring with anhydrous Me₄NF was converted to the rhodium fluoride complex <i>cis</i>-Rh­(6-ⁱPr)­(PPh₃)₂F (<b>3a</b>). Thermolysis of <b>1a</b>/<b>1b</b> with C₆F₆ resulted in C–F bond activation to afford a mixture of <b>3a</b> and the pentafluorophenyl complex <i>trans</i>-Rh­(6-ⁱPr)­(PPh₃)₂(C₆F₅) (<b>5b</b>). Complexes <b>1b</b>,<b> 2a</b>, <b>3a</b>, and <b>5b</b> were structurally characterized

Ring-Expanded N‑Heterocyclic Carbene Complexes of Rhodium with Bifluoride, Fluoride, and Fluoroaryl Ligands

Thermolysis of Rh­(PPh₃)₄H in the presence of the six-membered N-heterocyclic carbene 1,3-bis­(2-propyl)-3,4,5,6-tetrahydropyrimidin-2-ylidine (6-ⁱPr) gave the monocarbene complex Rh­(6-ⁱPr)­(PPh₃)₂H as a 1:2 mixture of the cis- and trans-phosphine isomers <b>1a</b> and <b>1b</b>. This same isomeric mixture was formed as the ultimate product from treating Rh­(PPh₃)₃(CO)H with 6-ⁱPr at room temperature, although pathways involving both CO and PPh₃ loss were observed at initial times. Treatment of <b>1a</b>/<b>1b</b> with Et₃N·3HF generated the bifluoride complex <i>cis</i>-Rh­(6-ⁱPr)­(PPh₃)₂(FHF) (<b>2a</b>), which upon stirring with anhydrous Me₄NF was converted to the rhodium fluoride complex <i>cis</i>-Rh­(6-ⁱPr)­(PPh₃)₂F (<b>3a</b>). Thermolysis of <b>1a</b>/<b>1b</b> with C₆F₆ resulted in C–F bond activation to afford a mixture of <b>3a</b> and the pentafluorophenyl complex <i>trans</i>-Rh­(6-ⁱPr)­(PPh₃)₂(C₆F₅) (<b>5b</b>). Complexes <b>1b</b>,<b> 2a</b>, <b>3a</b>, and <b>5b</b> were structurally characterized

Structure and Reactivity of [Ru–Al] and [Ru–Sn] Heterobimetallic PPh₃‑Based Complexes

Treatment of [Ru(PPh3)(C6H4PPh2)2H][Li(THF)2] with AlMe2Cl and SnMe3Cl leads to elimination of LiCl and CH4 and formation of the heterobimetallic complexes [Ru(C6H4PPh2)2{PPh2C6H4AlMe(THF)}H] 5 and [Ru(PPh3)(C6H4PPh2)(PPh2C6H4SnMe2)] 6, respectively. The pathways to 5 and 6 have been probed by variable temperature NMR studies, together with input from DFT calculations. Complete reaction of H2 occurs with 5 at 60 °C and with 6 at room temperature to yield the spectroscopically characterized trihydride complexes [Ru(PPh2)2{PPh2C6H4AlMe}H3] 7 and [Ru(PPh2)2{PPh2C6H4SnMe2}H3] 8. In the presence of CO, 6 forms the acylated phosphine complex, [Ru(CO)2(C(O)C6H4PPh2)(PPh2C6H4SnMe2)] 9, through a series of intermediates that were identified by NMR spectroscopy in conjunction with 13CO labeling. Complex 6 undergoes addition and substitution reactions with the N-heterocyclic carbene 1,3,4,5-tetramethylimidazol-2-ylidene (IMe4) to give [Ru(IMe4)2(PPh2C6H4)(PPh2C6H4SnMe2)] 10, which converted via rare N-Me group C–H activation to [Ru(IMe4)(PPh3)(IMe4)′(PPh2C6H4SnMe2)] 11 upon heating at 60 °C and to a mixture of [Ru(IMe4)2(IMe4)′(PPh2C6H4SnMe2)] 12 and [Ru(PPh3)(PPh2C6H4)(IMe4-SnMe2)′] 13 at 120 °C

Structure and Reactivity of [Ru–Al] and [Ru–Sn] Heterobimetallic PPh₃‑Based Complexes

Treatment of [Ru(PPh3)(C6H4PPh2)2H][Li(THF)2] with AlMe2Cl and SnMe3Cl leads to elimination of LiCl and CH4 and formation of the heterobimetallic complexes [Ru(C6H4PPh2)2{PPh2C6H4AlMe(THF)}H] 5 and [Ru(PPh3)(C6H4PPh2)(PPh2C6H4SnMe2)] 6, respectively. The pathways to 5 and 6 have been probed by variable temperature NMR studies, together with input from DFT calculations. Complete reaction of H2 occurs with 5 at 60 °C and with 6 at room temperature to yield the spectroscopically characterized trihydride complexes [Ru(PPh2)2{PPh2C6H4AlMe}H3] 7 and [Ru(PPh2)2{PPh2C6H4SnMe2}H3] 8. In the presence of CO, 6 forms the acylated phosphine complex, [Ru(CO)2(C(O)C6H4PPh2)(PPh2C6H4SnMe2)] 9, through a series of intermediates that were identified by NMR spectroscopy in conjunction with 13CO labeling. Complex 6 undergoes addition and substitution reactions with the N-heterocyclic carbene 1,3,4,5-tetramethylimidazol-2-ylidene (IMe4) to give [Ru(IMe4)2(PPh2C6H4)(PPh2C6H4SnMe2)] 10, which converted via rare N-Me group C–H activation to [Ru(IMe4)(PPh3)(IMe4)′(PPh2C6H4SnMe2)] 11 upon heating at 60 °C and to a mixture of [Ru(IMe4)2(IMe4)′(PPh2C6H4SnMe2)] 12 and [Ru(PPh3)(PPh2C6H4)(IMe4-SnMe2)′] 13 at 120 °C

Evaluation of the Asthma Friendly Schools program

This thesis examined what makes schools want to embrace the Asthma Friendly Schools program. It also investigated the limitations and barriers of the Asthma Friendly Schools program and explored it\u27s uptake by schools and the implications of the findings for the redesign of the program

Multinuclear Copper(I) Guanidinate Complexes

A series of multinuclear Copper­(I) guanidinate complexes have been synthesized in a succession of reactions between CuCl and the lithium guanidinate systems Li­{<b>L</b>} (<b>L</b> = Me₂NC­(^<i>i</i>PrN)₂ (<b>1a</b>), Me₂NC­(CyN)₂ (<b>1b</b>), Me₂NC­(^<i>t</i>BuN)₂ (<b>1c</b>), and Me₂NC­(DipN)₂ (<b>2d</b>) (^<i>i</i>Pr = iso-propyl, Cy = cyclohexyl, ^<i>t</i>Bu = <i>tert</i>-butyl, and Dip = 2,6-<i>di</i>sopropylphenyl) made in situ, and structurally characterized. The <i>di</i>-copper guanidinates systems with the general formula [Cu₂{<b>L</b>}₂] (<b>L</b> = {Me₂NC­(^<i>i</i>PrN)₂} (<b>2a</b>), {Me₂NC­(CyN)₂} (<b>2b</b>), and {Me₂NC­(DipN)₂} (<b>2d</b>) differed significantly from related amidinate complexes because of a large torsion of the dimer ring, which in turn is a result of transannular repulsion between adjacent guanidinate substituents. Attempts to synthesis the <i>tert</i>-butyl derivative [Cu₂{Me₂NC­(^<i>t</i>BuN)₂}₂] result in the separate formation and isolation of the <i>tri</i>-copper complexes [Cu₃{Me₂NC­(^<i>t</i>BuN)₂}₂(μ-NMe₂)] (<b>3c</b>) and [Cu₃{Me₂NC­(^<i>t</i>BuN)₂}₂(μ-Cl)] (<b>4c</b>), both of which have been unambiguously characterized by single crystal X-ray diffraction. Closer inspection of the solution state behavior of the lithium salt <b>1c</b> reveals a previously unobserved equilibrium between <b>1c</b> and its starting materials, LiNMe₂ and <i>N,N</i>′-di-<i>tert</i>-butyl-carbodiimide, for which activation enthalpy and entropy values of Δ<i>H</i>^⧧ = 48.2 ± 18 kJ mol^–1 and Δ<i>S</i>^⧧ = 70.6 ± 6 J/K mol have been calculated using 1D-EXSY NMR spectroscopy to establish temperature dependent rates of exchange between the species in solution. The molecular structures of the lithium complexes <b>1c</b> and <b>1d</b> have also been determined and shown to form tetrameric and dimeric complexes respectively held together by Li–N and agostic Li···H–C interactions. The thermal chemistry of the copper complexes have also been assessed by thermogravimetric analysis