Efficient CO2 Insertion and Reduction Catalyzed by a Terminal Zinc Hydride Complex

The terminal zinc hydride complex [Tntm]ZnH ( 2 ; Tntm=tris(6‐tert‐butyl‐3‐thiopyridazinyl)methanide) is an efficient hydrosilylation catalyst of CO₂ at room temperature without the need of Lewis acidic additives. The inherent electrophilicity of the system leads to selective formation of the monosilylated product (MeO)₃SiO₂CH (at room temperature with a TOF of 22.2 h^?1 and at 45 °C with a TOF of 66.7 h^?1). In absence of silanes, the intermediate formate complex [Tntm]Zn(O₂CH) ( 3 ) is quantitatively formed within 5 min. All complexes were fully characterized by ¹H and ¹³C NMR spectroscopy and single‐crystal X‐ray diffraction analyses. Density functional theory (DFT) calculations reveal a high positive charge on zinc and the increased preference of the ligand to adopt a κ³‐coordination mode.     

Extractionsapparate

Ohne Zusammenfassung     

Homologous Silver Bismuth Chalcogenide Halides (N,x)P. II. The (2, x)P and (3, x)P Structure Families of Modular Compounds with Tunable Composition and Structure

The crystal structures of two members of the solid solution series Ag_3xBi_5?3xS_8?6xCl_6x?1 (x = 0.52 (I) , x = 0.67 (II) ) and three compounds of the Ag_4xBi_6?4xQ_10?8xBr_8x?2 series (Q = S: x = 0.70 (III) , x = 0.84 (IV) ; Q = Se: x = 0.72 (V) ) were determined by single‐crystal X‐ray diffraction. The compounds crystallize in the monoclinic space group C2/m (No. 12) with a = 1326.7(3), b = 403.9(1), c = 1176.7(2) pm, β = 107.83(3)° for (I) ; a = 1325.4(3), b = 403.3(1), c = 1170.6(2) pm, β = 108.14(3)° for (II) ; a = 1338.9(4), b = 407.7(1), c = 1426.4(4) pm, β = 113.95(2)° for (III) ; a = 1346.7(4), b = 409.3(1), c = 1440.7(4) pm, β = 114.40(1)° for (IV) ; and a = 1370.9(2), b = 417.64(4), c = 1480.4(2) pm, β = 114.92(2)° for (V) . (I) and (II) adopt the PbBi₄S₇ structure type, (III) to (V) crystallize in the CuBi₅S₈ type. All five compounds belong to the homologous series with general formula [BiQX]₂[Ag_xBi_1?xQ_2?2xX_2x?1]_N+1 (Q = S, Se; X = Cl, Br; 1/2 ≤ x ≤ 1)), which resemble minerals of the pavonite series. They are characterized by the parameters N and x and are denoted ^{(N, x)}P. In the crystal structures, two kinds of layered modules alternate along [001]. Modules of type A uniformly consist of paired rods of face‐sharing monocapped trigonal prisms around Bi atoms with octahedra around mixed occupied metal positions (M = Ag/Bi) between them. Modules of type B are composed of chains of edge‐sharing [MZ₆] octahedra (M = Ag/Bi; Z = Q/X). These NaCl‐type fragments are of thickness N = 2 in Ag_3xBi_5?3xS_8?6xCl_6x?1 and N = 3 in Ag_4xBi_6?4xQ_10?8xBr_8x?2. All structures exhibit Ag/Bi disorder in octahedrally coordinated metal positions and Q/X mixed occupation of some anion positions.     

Homologous Silver Bismuth Chalcogenide Halides (N,x)P. III. The (4, x)P, (5, x)P,and (7, x)P Structure Families of Modular Compounds with Tunable Composition and Structure

The crystal structures of six members of the homologous series with general formula [BiQX]₂[Ag_xBi_1?xQ_2?2xX_2x?1]_N+1 (Q = S, Se; X = Cl, Br; 1/2 ≤ x ≤ 1) and N = 4, 5, or 7 were determined by single‐crystal X‐ray diffraction. The series are characterized by the parameters N and x and are denoted ^{(N, x)}P. Ag₃Bi₄S₆Cl₃ (x = 0.60) (I) , Ag_3.5Bi_3.5S₅Br₄ (x = 0.70) (II) and Ag_3.65Bi_3.35Se_4.70Br_4.30 (x = 0.73) (III) belong to ^{(4, x})P series Ag_5xBi_7?5xQ_12?10xX_10x?3 and adopt the AgBi₆S₉ structure type. The ^{(5, x)}P compound Ag_3.66Bi_4.34S_6.68Br_3.32 (IV) , which corresponds to x = 0.61 in Ag_6xBi_8?6xS_14?12xBr_12x?4, crystallizes isostructurally to AgBi₃S₅. The compounds Ag_4.56Bi_5.44Se_8.88Br_3.12 (x = 0.57) (V) and Ag_5.14Bi_4.86S_7.76Br_4.24 (x = 0.64) (VI) , which are members of ^{(7, x)}P series Ag_8xBi_10?8xQ_18?16xBr_16x?6, adopt the Ag₃Bi₇S₁₂ structure type. In the monoclinic crystal structures (space group C2/m) two kinds of layered modules alternate along [001]. Modules of type A uniformly consist of paired rods of face‐sharing monocapped trigonal prisms around Bi atoms with octahedra around mixed occupied metal positions (M = Ag/Bi) between them. Modules of type B are composed of [MZ₆] octahedra, which are arranged in NaCl‐type fragments of thickness N. All structures exhibit Ag/Bi disorder in octahedrally coordinated metal positions as well as Q/X mixed occupation of some anion positions. Corresponding to their black color, all compounds are narrow‐gap semiconductors (E_g = 0.35 eV for (II) ). General characteristics of the entire class of ^{(N, x)}P compounds are gathered in a catalogue.     

tert‐Amino effect at a coumarin and a 2‐quinolone system: Synthesis of 1,2 fused 5H‐chromeno[4,3‐b]pyridin‐5‐ones and a 6H‐benzo[h][1,6]naphthyridin‐5‐one

Some novel 1,2‐fused 5H‐chromeno[4,3‐b]pyridin‐5‐ones ( 5a,b ) and a 6H‐benzo[h][1,6]naphthyridin‐5‐one ( 5c ) have been synthesized starting from the 4‐chlorocoumarin‐3‐carbaldehyde ( 1a ) or its N‐methyl‐2‐quinolone analogue ( 1b ) via subsequent Knoevenagel condensation and ring closure reaction known as the ‘tert‐amino effect’. These are rare examples of the tert‐amino effect occurring at 2‐pyrone and 2‐pyridone ring. An unusual intramolecular redox reaction of the iminium ion 6 , reported earlier, most probably follows analogous mechanism as the tert‐amino effect reactions leading to 5 .