Synthese und Charakterisierung heterobimetallischer Bis(trimethylsilyl)phosphanide von Barium und Zinn

Synthesis and Characterization of Hetero-bimetallic Bis(trimethylsilyl)phosphanides of Barium and Tin The reaction of barium bis[bis(trimethylsilyl)amide] with one equivalent of bis(trimethylsilyl)phosphane in 1,2-dimethoxyethane (dme) yields the heteroleptic dimeric (dme)barium bis(trimethylsilyl)amide bis(trimethylsilyl)phosphanide. This colorless compound crystallizes in the monoclinic space group P2₁/n with a = 1 259.1(3), b = 1 822.7(4), c = 1 516.1(3) pm, β = 110.54(3)° and Z = 4. The central moiety of the centrosymmetric molecule is the planar Ba₂P₂-cycle with Ba? P-bond lengths of 329 and 334 pm. In the presence of bis[bis(trimethylsilyl)amino]stannylene hetero-bimetallic bis(trimethylsilyl)phosphanides of tin(II) and barium are isolated. If the reaction of Ba[N(SiMe₃)₂]₂ and Sn[N(SiMe₃)₂]₂ in the molar ratio of 1:2 with six equivalents of HP(SiMe₃)₂ is performed in toluene, barium bis{tin(II)-tris[bis(trimethylsilyl)phosphanide]} can be isolated. This compound crystallizes in the orthorhombic space group P2₁2₁2₁ with a = 1 265.1(1), b = 2 290.1(3), c = 2 731.9(3) pm and Z = 4. The anions {Sn[P(SiMe₃)₂]₃}^? bind as two-dentate ligands to the barium atom which shows the extraordinary low coordination number of four. The addition of tetrahydrofuran (thf) to the above mentioned reaction solution leads to the elimination of tris(trimethylsilyl)phosphane and the formation of thf complexes of barium bis{tin(II)-bis(trimethylsilyl)phosphanide-trimethylsilylphosphandiide}. The derivative crystallizes from toluene in the monoclinic space group P2₁/c with a = 1 301.9(2), b = 2 316.3(3), c = 3 968.7(5) pm, β = 99.29(1)° and Z = 8.     

Komplexkatalyse. XIX. Zur Synthese von Nitrosylkomplexen des Wolframs und deren Eignung als Präkatalysatoren für die Olefinmetathese

Complex Catalysis. XIX. Synthesis of Nitrosyl Complexes of Tungsten and their Usefulness as Precatalysts for Olefin Metathesis Nitrosylating reduction of WCl₆ with NO leads to WCl₃(NO)₄ that on addition of different donor ligands L yields complexes of the types WCl₃(NO)L₂ (L = OOh₃, HMPT, pyridine) and WX₂(NO)₂ L₂ (L = PPh₃, X = Cl; XL = acac) or mixtures of products (L = Dipy, RCN, Et₄NCl), respectively. Whereas by carbonylation of WCl₃(NO)(OPPh₃)₂ in the presence of EtAlCl₂ only chloro carbonyl tungsten complexes are formed, the reaction of W(CO)₆ with NOAlCl₄ and subsequent addition of PPh₃ gives, in analogy to molybdenum, the nitrosyl carbonyl complexes W(NO)(CO)₄(AlCl₄) and WCl(NO)(CO)₂(PPh₃)₂. All the nitrosyl tungsten complexes in combination with EtAlCl₂ catalyze the metathesis of pent-2-ene, however, with a significantly lower activity than the corresponding nitrosyl molybdenum systems.