Regio- and Stereoselective 1,3-Dipolar Cycloaddition of Cyclic Azomethine Imines to Platinum(IV)-Bound Nitriles Giving Δ²‑1,2,4-Triazoline Species

The complex <i>trans-</i>[PtCl₄(EtCN)₂] (<b>14</b>) reacts smoothly at 25 °C with the stable cyclic azomethine imines R¹CHN^<i>a</i>NC­(O)­CH­(NHC­(O)­C₆H₄R³)­C^<i>b</i>H­(C₆H₄R²)^{(<i>a</i>−<i>b</i>)} [R¹/R²/R³ = <i>p-</i>Me/H/H (<b>8</b>); <i>p-</i>Me/<i>p-</i>Me/H (<b>9</b>); <i>p-</i>Me/<i>p-</i>MeO/H (<b>10</b>); <i>p-</i>Me/<i>p-</i>Cl/<i>p-</i>Cl (<b>11</b>); <i>p-</i>MeO/<i>p-</i>Me/H (<b>12</b>); <i>p-</i>MeO/<i>p-</i>Cl/<i>m-</i>Me (<b>13</b>)], and the reaction proceeds as stereoselective 1,3-dipolar cycloaddition to one of the EtCN ligands accomplishing the <i>mono</i>cycloadducts <i>trans-</i>[PtCl₄(EtCN)­{N^<i>a</i>C­(Et)­<i>N</i>^<i>b</i>C­(O)­CH­(NHC­(O)­C₆H₄R³)­CH­(C₆H₄R²)­<i>N</i>^<i>c</i>C^<i>d</i>HR¹}])^{(<i>a–d;b–c</i>)} [R¹/R²/R³ = <i>p-</i>Me/H/H (<b>15</b>); <i>p-</i>Me/<i>p-</i>Me/H (<b>16</b>); <i>p-</i>Me/<i>p-</i>MeO/H (<b>17</b>); <i>p-</i>Me/<i>p-</i>Cl/<i>p-</i>Cl (<b>18</b>); <i>p-</i>MeO/<i>p-</i>Me/H (<b>19</b>); <i>p-</i>MeO/<i>p-</i>Cl/<i>m-</i>Me (<b>20</b>)]. Inspection of the obtained and literature data indicate that the cycloaddition of the azomethine imines to the C≡N bonds of HCN and of Pt^IV-bound EtCN has different regioselectivity leading to Δ²-1,2,3-triazolines and Δ²-1,2,4-triazolines, respectively. Platinum­(II) species <i>trans-</i>[PtCl₂(EtCN)­{N^<i>a</i>C­(Et)­<i>N</i>^<i>b</i>C­(O)­CH­(NHC­(O)­C₆H₄R³)­CH­(C₆H₄R²)­<i>N</i>^<i>c</i>C^<i>d</i>HR¹}]^{(<i>a–d;b–c</i>)} [R¹/R²/R³ = <i>p-</i>Me/H/H (<b>21</b>); <i>p-</i>Me/<i>p-</i>Me/H (<b>22</b>); <i>p-</i>Me/<i>p-</i>MeO/H (<b>23</b>); <i>p-</i>Me/<i>p-</i>Cl/<i>p-</i>Cl (<b>24</b>); <i>p-</i>MeO/<i>p-</i>Me/H (<b>25</b>); <i>p-</i>MeO/<i>p-</i>Cl/<i>m-</i>Me (<b>26</b>)] were obtained by a one-pot procedure from <b>14</b> and <b>8</b>–<b>13</b> followed by addition of the phosphorus ylide Ph₃PCHCO₂Me. Δ²-1,2,4-Triazolines N^<i>a</i>C­(Et)<i>­N</i>^<i>b</i>C­(O)­CH­(NHC­(O)­C₆H₄R³)­CH­(C₆H₄R²)­<i>N</i>^<i>c</i>C^<i>d</i>HR^{1(<i>a–d;b–c</i>)} [R¹/R²/R³ = <i>p-</i>Me/H/H (<b>27</b>); <i>p-</i>Me/<i>p-</i>Me/H (<b>28</b>); <i>p-</i>Me/<i>p-</i>MeO/H (<b>29</b>); <i>p-</i>Me/<i>p-</i>Cl/<i>p-</i>Cl (<b>30</b>); <i>p-</i>MeO/<i>p-</i>Me/H (<b>31</b>); <i>p-</i>MeO/<i>p-</i>Cl/<i>m-</i>Me (<b>32</b>)] were liberated from <b>21</b>–<b>26</b> by the treatment with bis­(diphenylphosphyno)­ethane (dppe). Platinum­(II) complexes <b>21</b>–<b>26</b> were characterized by elemental analyses (C, H, N), high-resolution electrospray ionization mass spectrometry (ESI-MS), and IR and ¹H and ¹³C­{¹H} NMR spectroscopies and single crystal X-ray diffraction in the solid state for <b>25</b>·CH₃OH, <b>26</b>·(CHCl₃)_0.84. The structure of <b>26</b> was also determined by COSY-90 and NOESY NMR methods in solution. Quantitative evaluation of several pairs of interproton distances obtained by NMR and X-ray diffraction agrees well with each other and with those obtained by the MM+ calculation method. Platinum­(IV) complexes <b>15</b>–<b>20</b> were characterized by ¹H NMR spectroscopy. Metal-free 6,7-dihydropyrazolo­[1,2-<i>a</i>]­[1,2,4]­triazoles (<b>27</b>–<b>32</b>) were characterized by high-resolution ESI-MS and IR and ¹H and ¹³C­{¹H} NMR spectroscopies and single crystal X-ray diffraction for <b>29</b>·CDCl₃. Theoretical density functional theory calculations were carried out for the investigation of the reaction mechanism, interpretation of the reactivity of Pt-bound and free nitriles toward azomethine imines and analysis of the regio- and stereoselectivity origin

Intensely Luminescent Homoleptic Alkynyl Decanuclear Gold(I) Clusters and Their Cationic Octanuclear Phosphine Derivatives

Treatment of Au­(SC₄H₈)Cl with a stoichiometric amount of hydroxyaliphatic alkyne in the presence of NEt₃ results in high-yield self-assembly of homoleptic clusters (AuC₂R)₁₀ (R = 9-fluorenol (<b>1</b>), diphenylmethanol (<b>2</b>), 2,6-dimethyl-4-heptanol (<b>3</b>), 3-methyl-2-butanol (<b>4</b>), 4-methyl-2-pentanol (<b>4</b>), 1-cyclohexanol (<b>6</b>), 2-borneol (<b>7</b>)). The molecular compounds contain an unprecedented catenane metal core with two interlocked 5-membered rings. Reactions of the decanuclear clusters <b>1</b>–<b>7</b> with gold–diphosphine complex [Au₂(1,4-PPh₂–C₆H₄–PPh₂)₂]²⁺ lead to octanuclear cationic derivatives [Au₈(C₂R)₆(PPh₂–C₆H₄–PPh₂)₂]²⁺ (<b>8</b>–<b>14</b>), which consist of planar tetranuclear units {Au₄(C₂R)₄} coupled with two fragments [AuPPh₂–C₆H₄–PPh₂(AuC₂R)]⁺. The titled complexes were characterized by NMR and ESI-MS spectroscopy, and the structures of <b>1</b>, <b>13</b>, and <b>14</b> were determined by single-crystal X-ray diffraction analysis. The luminescence behavior of both Au^I₁₀ and Au^I₈ families has been studied, revealing efficient room-temperature phosphorescence in solution and in the solid state, with the maximum quantum yield approaching 100% (<b>2</b> in solution). DFT computational studies showed that in both Au^I₁₀ and Au^I₈ clusters metal-centered Au → Au charge transfer transitions mixed with some π-alkynyl MLCT character play a dominant role in the observed phosphorescence

Sky-Blue Luminescent Au^I–Ag^I Alkynyl-Phosphine Clusters

Treatment of the (AuC₂R)_<i>n</i> acetylides with phosphine ligand 1,4-bis­(diphenylphosphino)­butane (PbuP) and Ag⁺ ions results in self-assembly of the heterobimetallic clusters of three structural types depending on the nature of the alkynyl group. The hexadecanuclear complex [Au₁₂Ag₄(C₂R)₁₂(PbuP)₆]⁴⁺ (<b>1</b>) is formed for R = Ph, and the octanuclear species [Au₆Ag₂(C₂R)₆(PbuP)₃]²⁺ adopting two structural arrangements in the solid state were found for the aliphatic alkynes (R = Bu^t (<b>2</b>), 2-propanolyl (<b>3</b>), 1-cyclohexanolyl (<b>4</b>), diphenylmethanolyl (<b>5</b>), 2-borneolyl (<b>6</b>)). The structures of the compounds <b>1</b>–<b>4</b> and <b>6</b> were determined by single crystal X-ray diffraction analysis. The NMR spectroscopic studies revealed complicated dynamic behavior of <b>1</b>–<b>3</b> in solution. In particular, complexes <b>2</b> and <b>3</b> undergo reversible transformation, which involves slow interconversion of two isomeric forms. The luminescence behavior of the titled clusters has been studied. All the compounds exhibit efficient sky-blue room-temperature phosphorescence both in solution and in the solid state with maximum quantum yield of 76%. The theoretical DFT calculations of the electronic structures demonstrated the difference in photophysical properties of the compounds depending on their structural topology

Sky-Blue Luminescent Au^I–Ag^I Alkynyl-Phosphine Clusters

Treatment of the (AuC₂R)_<i>n</i> acetylides with phosphine ligand 1,4-bis­(diphenylphosphino)­butane (PbuP) and Ag⁺ ions results in self-assembly of the heterobimetallic clusters of three structural types depending on the nature of the alkynyl group. The hexadecanuclear complex [Au₁₂Ag₄(C₂R)₁₂(PbuP)₆]⁴⁺ (<b>1</b>) is formed for R = Ph, and the octanuclear species [Au₆Ag₂(C₂R)₆(PbuP)₃]²⁺ adopting two structural arrangements in the solid state were found for the aliphatic alkynes (R = Bu^t (<b>2</b>), 2-propanolyl (<b>3</b>), 1-cyclohexanolyl (<b>4</b>), diphenylmethanolyl (<b>5</b>), 2-borneolyl (<b>6</b>)). The structures of the compounds <b>1</b>–<b>4</b> and <b>6</b> were determined by single crystal X-ray diffraction analysis. The NMR spectroscopic studies revealed complicated dynamic behavior of <b>1</b>–<b>3</b> in solution. In particular, complexes <b>2</b> and <b>3</b> undergo reversible transformation, which involves slow interconversion of two isomeric forms. The luminescence behavior of the titled clusters has been studied. All the compounds exhibit efficient sky-blue room-temperature phosphorescence both in solution and in the solid state with maximum quantum yield of 76%. The theoretical DFT calculations of the electronic structures demonstrated the difference in photophysical properties of the compounds depending on their structural topology