Hohervalente Derivate der d‐Metall‐Sauren, 13. Homoscorpionate als tripodale Ankerliganden chlorfunktioneller Oxo‐ und Imidokomplexe von Elementen der 5.‐7. Gruppe

Abstract

Higher‐Valent Derivatives of the d‐Metal Acids, 13. — Homoscorpionates as Tripodal Anchoring Ligands of Chloro Functionalized Oxo and Imido Complexes of Elements of Group 5–7 Hydridotris(pyrazolyl)borate complexes of elements of group 5–7 have been prepared by reaction of d 0 ‐metalloyl chlorides [M(Y) n Cl m ] x (Y = O, NR) with KTp * (Tp * = κ 3 ‐HB(3,5‐Me 2 pz) 3 ). Thus [NbOCl 3 ] x and [TaOCl 3 ] x are converted into monomeric and well‐characterized oxo complexes [Tp * Nb(O)Cl 2 ] ( 1 ) and [Tp * Ta(O)Cl 2 ] ( 2 ). In a similar way [Tp * Mo(O) 2 Cl] ( 3 ) and [Tp * W(O) 2 Cl] ( 4 ) have been obtained from the oxo chlorides [MoO 2 Cl 2 ] x and [WO 2 Cl 2 ] x , respectively. tert ‐Butylamine reacts with NbCl 5 and TaCl 5 in the presence of pyridine to give the imido pyridine complexes [Nb(N t Bu)Cl 3 (py) 2 ] ( 5 ) and [Ta(N t Bu)Cl 3 (py) 2 ] ( 6 ) in excellent yield. Imido complexes [Tp * V(N t Bu)Cl 2 ] ( 7 ), [Tp * Nb(N t Bu)Cl 2 ] ( 8 ), and [Tp * Ta(N t Bu)Cl 2 ] ( 9 ) are formed by the reaction of KTp * with the precursers [V(N t Bu)Cl 3 ] x or 5 and 6 , respectively. The corresponding imido complexes of group 6, namely [Tp * Cr(N t Bu) 2 Cl] ( 10 ), [Tp * Mo(N t Bu) 2 Cl] ( 11 ), and [Tp * W(NR) 2 Cl] (R = t Bu 12a , 2,4,6‐Mesityl 12b , SO 2 Ph 12c ) are obtained directly from the imidoyl chlorides or their complexes with Lewis bases. 11 and 12 are prone to protonation at the imido ligand to yield cationic amido species [Tp * M(N t Bu)(NH t Bu)Cl]BF 4 (M = Mo 13 , W 14 ). Finally the preparation of cationic imido rhenium complex [Tp * Re(N t Bu) 2 Cl]PF 6 ( 15 ), isoelectronic with 10 – 12 , is described. The molecular structure of 11 has been determined by X‐ray diffraction. Despite of a maximum electron count of 20 valence electrons, all three pyrazolyl groups of the tripodal ligand are facially coordinated. In a way similar to the well‐known ring slippage of analogous cyclopentadienyl complexes, the weakest bound pyrazolyl ligand is asymmetrically attached to molybdenum deviating from the positions expected for local C 3v symmetry.