Complexes of Lanthanide Nitrates with Tri Tert Butylphosphine Oxide

Reaction of lanthanide nitrates with ^tBu₃PO (=L) lead to the isolation of complexes Ln­(NO₃)₃L₂·H₂O·<i>n</i>EtOH (Ln = La (<b>1</b>), Nd­(<b>2</b>)), Ln­(NO₃)₃L₂ ·<i>n</i>EtOH (Sm­(<b>3</b>), Eu­(<b>4</b>)), and Ln­(NO₃)₃L₂ (Dy­(<b>5</b>), Er­(<b>6</b>), Lu­(<b>7</b>)). These have been characterized by elemental analysis, infrared and NMR­(¹H, ¹³C and ³¹P) spectroscopy and single-crystal X-ray diffraction. The structures show L to be positioned on opposite sides of the metal with the nitrates forming an equatorial band. When Ln = Dy, Er, and Lu two distinct molecules are present in the unit cell. A major isomer (70%) has a (P)­O–Ln–O­(P) angle of less than 180° with one of the nitrate ligands twisted out of the plane of the other nitrates while the lower abundance isomer is more symmetric with the (P)­O–Ln–O­(P) angle of 180° and the nitrate ligands coplanar giving a hexagonal bipyramidal geometry. These isomers cannot be observed by variable temperature solution ³¹P NMR measurements but are clearly seen in the solid-state NMR spectrum of the Lu complex. Variable temperature solid-state NMR indicates that the isomers do not interconvert at temperatures up to 100 °C. Attempts to prepare cationic species [Ln­(NO₃)₂L₃]⁺[PF₆]⁻ have not been totally successful and led to the isolation of crystals of Lu­(NO₃)₃L₂ and Tb­(NO₃)₃L₂.CH₃CN (<b>8</b>)

Complexes of Lanthanide Nitrates with Tri Tert Butylphosphine Oxide

Reaction of lanthanide nitrates with ^tBu₃PO (=L) lead to the isolation of complexes Ln­(NO₃)₃L₂·H₂O·<i>n</i>EtOH (Ln = La (<b>1</b>), Nd­(<b>2</b>)), Ln­(NO₃)₃L₂ ·<i>n</i>EtOH (Sm­(<b>3</b>), Eu­(<b>4</b>)), and Ln­(NO₃)₃L₂ (Dy­(<b>5</b>), Er­(<b>6</b>), Lu­(<b>7</b>)). These have been characterized by elemental analysis, infrared and NMR­(¹H, ¹³C and ³¹P) spectroscopy and single-crystal X-ray diffraction. The structures show L to be positioned on opposite sides of the metal with the nitrates forming an equatorial band. When Ln = Dy, Er, and Lu two distinct molecules are present in the unit cell. A major isomer (70%) has a (P)­O–Ln–O­(P) angle of less than 180° with one of the nitrate ligands twisted out of the plane of the other nitrates while the lower abundance isomer is more symmetric with the (P)­O–Ln–O­(P) angle of 180° and the nitrate ligands coplanar giving a hexagonal bipyramidal geometry. These isomers cannot be observed by variable temperature solution ³¹P NMR measurements but are clearly seen in the solid-state NMR spectrum of the Lu complex. Variable temperature solid-state NMR indicates that the isomers do not interconvert at temperatures up to 100 °C. Attempts to prepare cationic species [Ln­(NO₃)₂L₃]⁺[PF₆]⁻ have not been totally successful and led to the isolation of crystals of Lu­(NO₃)₃L₂ and Tb­(NO₃)₃L₂.CH₃CN (<b>8</b>)

Synthesis, Structures, and Stereodynamic Behavior of Novel Pentacoordinate Fluorosilanes: Fluorosilyl Derivatives of Proline

The (O→Si)-chelate <i>N</i>′-(dimethylfluorosilylmethyl))-<i>N</i>′-methyl-<i>N</i>-(organosulfonyl)­prolinamides RSO₂-Pro-N­(Me)­CH₂SiMe₂F (<b>2a</b>–<b>f</b>, R = Me (<b>a</b>), Ph (<b>b</b>), 4-MeC₆H₄ (<b>c</b>), 4-ClC₆H₄ (<b>d</b>), 4-BrC₆H₄ (<b>e</b>), 4-NO₂C₆H₄ (<b>f</b>)) were synthesized from the corresponding disiloxanes <b>1a</b>–<b>f</b> using Et₂O·BF₃. According to the NMR and IR data, the extent of dimerization of fluorosilanes <b>2a</b>–<b>f</b> in solution is negligible, while the O→Si coordination in solution is weaker than that in the solid state. Comparative CP/MAS NMR and X-ray diffraction studies revealed that in solution the coordination Si–O bond length varies in a narrow range (2.22–2.24 Å) that is 0.02–0.11 Å longer than in the crystalline state. Dynamic NMR (DNMR) studies of the fluorides revealed a fine structure of the ¹⁹F signals in the 0–20 °C temperature range, which was related to the structural features of the coordination set in these complexes. The temperature dependence of the SiMe₂ signals in the ¹H DNMR spectra was attributed to a permutational isomerization process involving a positional exchange of equatorial ligands. The narrow range of activational barriers of the process (23–24 kcal mol^–1 and more) and high negative values of the entropy of activation are similar to those observed earlier for Si-substituted <i>N</i>-(dimethylsilylmethyl) and <i>N</i>-(methylphenylsilylmethyl) amides and lactams, which suggests similar permutational processes in all cases. Gas-phase quantum chemical studies demonstrate that the solvation of F^– reduces the activation barrier

Synthesis, Structures, and Stereodynamic Behavior of Novel Pentacoordinate Fluorosilanes: Fluorosilyl Derivatives of Proline

The (O→Si)-chelate <i>N</i>′-(dimethylfluorosilylmethyl))-<i>N</i>′-methyl-<i>N</i>-(organosulfonyl)­prolinamides RSO₂-Pro-N­(Me)­CH₂SiMe₂F (<b>2a</b>–<b>f</b>, R = Me (<b>a</b>), Ph (<b>b</b>), 4-MeC₆H₄ (<b>c</b>), 4-ClC₆H₄ (<b>d</b>), 4-BrC₆H₄ (<b>e</b>), 4-NO₂C₆H₄ (<b>f</b>)) were synthesized from the corresponding disiloxanes <b>1a</b>–<b>f</b> using Et₂O·BF₃. According to the NMR and IR data, the extent of dimerization of fluorosilanes <b>2a</b>–<b>f</b> in solution is negligible, while the O→Si coordination in solution is weaker than that in the solid state. Comparative CP/MAS NMR and X-ray diffraction studies revealed that in solution the coordination Si–O bond length varies in a narrow range (2.22–2.24 Å) that is 0.02–0.11 Å longer than in the crystalline state. Dynamic NMR (DNMR) studies of the fluorides revealed a fine structure of the ¹⁹F signals in the 0–20 °C temperature range, which was related to the structural features of the coordination set in these complexes. The temperature dependence of the SiMe₂ signals in the ¹H DNMR spectra was attributed to a permutational isomerization process involving a positional exchange of equatorial ligands. The narrow range of activational barriers of the process (23–24 kcal mol^–1 and more) and high negative values of the entropy of activation are similar to those observed earlier for Si-substituted <i>N</i>-(dimethylsilylmethyl) and <i>N</i>-(methylphenylsilylmethyl) amides and lactams, which suggests similar permutational processes in all cases. Gas-phase quantum chemical studies demonstrate that the solvation of F^– reduces the activation barrier

Synthesis, Structures, and Stereodynamic Behavior of Novel Pentacoordinate Fluorosilanes: Fluorosilyl Derivatives of Proline

The (O→Si)-chelate <i>N</i>′-(dimethylfluorosilylmethyl))-<i>N</i>′-methyl-<i>N</i>-(organosulfonyl)­prolinamides RSO₂-Pro-N­(Me)­CH₂SiMe₂F (<b>2a</b>–<b>f</b>, R = Me (<b>a</b>), Ph (<b>b</b>), 4-MeC₆H₄ (<b>c</b>), 4-ClC₆H₄ (<b>d</b>), 4-BrC₆H₄ (<b>e</b>), 4-NO₂C₆H₄ (<b>f</b>)) were synthesized from the corresponding disiloxanes <b>1a</b>–<b>f</b> using Et₂O·BF₃. According to the NMR and IR data, the extent of dimerization of fluorosilanes <b>2a</b>–<b>f</b> in solution is negligible, while the O→Si coordination in solution is weaker than that in the solid state. Comparative CP/MAS NMR and X-ray diffraction studies revealed that in solution the coordination Si–O bond length varies in a narrow range (2.22–2.24 Å) that is 0.02–0.11 Å longer than in the crystalline state. Dynamic NMR (DNMR) studies of the fluorides revealed a fine structure of the ¹⁹F signals in the 0–20 °C temperature range, which was related to the structural features of the coordination set in these complexes. The temperature dependence of the SiMe₂ signals in the ¹H DNMR spectra was attributed to a permutational isomerization process involving a positional exchange of equatorial ligands. The narrow range of activational barriers of the process (23–24 kcal mol^–1 and more) and high negative values of the entropy of activation are similar to those observed earlier for Si-substituted <i>N</i>-(dimethylsilylmethyl) and <i>N</i>-(methylphenylsilylmethyl) amides and lactams, which suggests similar permutational processes in all cases. Gas-phase quantum chemical studies demonstrate that the solvation of F^– reduces the activation barrier

Synthesis, Structures, and Stereodynamic Behavior of Novel Pentacoordinate Fluorosilanes: Fluorosilyl Derivatives of Proline

The (O→Si)-chelate <i>N</i>′-(dimethylfluorosilylmethyl))-<i>N</i>′-methyl-<i>N</i>-(organosulfonyl)­prolinamides RSO₂-Pro-N­(Me)­CH₂SiMe₂F (<b>2a</b>–<b>f</b>, R = Me (<b>a</b>), Ph (<b>b</b>), 4-MeC₆H₄ (<b>c</b>), 4-ClC₆H₄ (<b>d</b>), 4-BrC₆H₄ (<b>e</b>), 4-NO₂C₆H₄ (<b>f</b>)) were synthesized from the corresponding disiloxanes <b>1a</b>–<b>f</b> using Et₂O·BF₃. According to the NMR and IR data, the extent of dimerization of fluorosilanes <b>2a</b>–<b>f</b> in solution is negligible, while the O→Si coordination in solution is weaker than that in the solid state. Comparative CP/MAS NMR and X-ray diffraction studies revealed that in solution the coordination Si–O bond length varies in a narrow range (2.22–2.24 Å) that is 0.02–0.11 Å longer than in the crystalline state. Dynamic NMR (DNMR) studies of the fluorides revealed a fine structure of the ¹⁹F signals in the 0–20 °C temperature range, which was related to the structural features of the coordination set in these complexes. The temperature dependence of the SiMe₂ signals in the ¹H DNMR spectra was attributed to a permutational isomerization process involving a positional exchange of equatorial ligands. The narrow range of activational barriers of the process (23–24 kcal mol^–1 and more) and high negative values of the entropy of activation are similar to those observed earlier for Si-substituted <i>N</i>-(dimethylsilylmethyl) and <i>N</i>-(methylphenylsilylmethyl) amides and lactams, which suggests similar permutational processes in all cases. Gas-phase quantum chemical studies demonstrate that the solvation of F^– reduces the activation barrier

Synthesis, Structures, and Stereodynamic Behavior of Novel Pentacoordinate Fluorosilanes: Fluorosilyl Derivatives of Proline

The (O→Si)-chelate <i>N</i>′-(dimethylfluorosilylmethyl))-<i>N</i>′-methyl-<i>N</i>-(organosulfonyl)­prolinamides RSO₂-Pro-N­(Me)­CH₂SiMe₂F (<b>2a</b>–<b>f</b>, R = Me (<b>a</b>), Ph (<b>b</b>), 4-MeC₆H₄ (<b>c</b>), 4-ClC₆H₄ (<b>d</b>), 4-BrC₆H₄ (<b>e</b>), 4-NO₂C₆H₄ (<b>f</b>)) were synthesized from the corresponding disiloxanes <b>1a</b>–<b>f</b> using Et₂O·BF₃. According to the NMR and IR data, the extent of dimerization of fluorosilanes <b>2a</b>–<b>f</b> in solution is negligible, while the O→Si coordination in solution is weaker than that in the solid state. Comparative CP/MAS NMR and X-ray diffraction studies revealed that in solution the coordination Si–O bond length varies in a narrow range (2.22–2.24 Å) that is 0.02–0.11 Å longer than in the crystalline state. Dynamic NMR (DNMR) studies of the fluorides revealed a fine structure of the ¹⁹F signals in the 0–20 °C temperature range, which was related to the structural features of the coordination set in these complexes. The temperature dependence of the SiMe₂ signals in the ¹H DNMR spectra was attributed to a permutational isomerization process involving a positional exchange of equatorial ligands. The narrow range of activational barriers of the process (23–24 kcal mol^–1 and more) and high negative values of the entropy of activation are similar to those observed earlier for Si-substituted <i>N</i>-(dimethylsilylmethyl) and <i>N</i>-(methylphenylsilylmethyl) amides and lactams, which suggests similar permutational processes in all cases. Gas-phase quantum chemical studies demonstrate that the solvation of F^– reduces the activation barrier

Synthesis, Structures, and Stereodynamic Behavior of Novel Pentacoordinate Fluorosilanes: Fluorosilyl Derivatives of Proline

The (O→Si)-chelate <i>N</i>′-(dimethylfluorosilylmethyl))-<i>N</i>′-methyl-<i>N</i>-(organosulfonyl)­prolinamides RSO₂-Pro-N­(Me)­CH₂SiMe₂F (<b>2a</b>–<b>f</b>, R = Me (<b>a</b>), Ph (<b>b</b>), 4-MeC₆H₄ (<b>c</b>), 4-ClC₆H₄ (<b>d</b>), 4-BrC₆H₄ (<b>e</b>), 4-NO₂C₆H₄ (<b>f</b>)) were synthesized from the corresponding disiloxanes <b>1a</b>–<b>f</b> using Et₂O·BF₃. According to the NMR and IR data, the extent of dimerization of fluorosilanes <b>2a</b>–<b>f</b> in solution is negligible, while the O→Si coordination in solution is weaker than that in the solid state. Comparative CP/MAS NMR and X-ray diffraction studies revealed that in solution the coordination Si–O bond length varies in a narrow range (2.22–2.24 Å) that is 0.02–0.11 Å longer than in the crystalline state. Dynamic NMR (DNMR) studies of the fluorides revealed a fine structure of the ¹⁹F signals in the 0–20 °C temperature range, which was related to the structural features of the coordination set in these complexes. The temperature dependence of the SiMe₂ signals in the ¹H DNMR spectra was attributed to a permutational isomerization process involving a positional exchange of equatorial ligands. The narrow range of activational barriers of the process (23–24 kcal mol^–1 and more) and high negative values of the entropy of activation are similar to those observed earlier for Si-substituted <i>N</i>-(dimethylsilylmethyl) and <i>N</i>-(methylphenylsilylmethyl) amides and lactams, which suggests similar permutational processes in all cases. Gas-phase quantum chemical studies demonstrate that the solvation of F^– reduces the activation barrier