• Daniele, Stéphane
• Decams, Jean-Manuel
• Lecocq, Sylvain
• Vaissermann, Jacqueline
• Hubert-Pfalzgraf, Liliane G.

Abstract

he reactions between lithium bis(trimethyl)phenylenediamide and niobium or tantalum pentachlorides at low temperature afforded [{4,5-Me2-C6H2(NSiMe3)2}2MCl] (M=Nb (1), Ta (2)) independently of the stoichiometry used, 1:1 or 2:1. The reaction between tantalum pentachloride and N,N′-bis(trimethylsilyl)-o-dimethylphenylene diamide o-C6H2Me2(NSiMe3)2 in Et2O–DME at −78 °C leads to a tantalum(V) imide 3. Monosubstitution with diamides was achieved on tantalum with the more rigid 1,8-diamido-naphtalene. The various compounds were characterized by elemental analysis, FT-IR and NMR. Compounds 1 and 3 were characterized also by single crystal X-ray diffraction. The metal is pentacoordinated for 1 bearing two bidentate o-phenylenediamide ligands and a chlorine in the apical position of a distorted square-tetragonal pyramid. The salient features are a disymmetrical coordination mode of the diamide ligand with two quite different Nb–N distances namely 1.981(2) and 2.053(3) A, as well as short Nb–C distances with the phenyl ring [2.495(3) and 2.471(3) A]. The diamide ligand is thus coordinated in a η4-fashion in the solid state. The salient feature of the structure of 3 is the presence in the metal coordination sphere of the functional imido ligand [Me2C6H2N(SiMe2Cl)(NSiMe3−xClx)]2− (x=1 or 0) which was generated by N–Si bond cleavage and Si–Me/Si–Cl scrambling. Tantalum is six-coordinate, linked to the bulky imido ligand, three chlorine and a bidentate dimethoxyethane. The surrounding of the metal is distorted with a TaN bond distance of 1.706(5) A and a large Ta–N(2)–C(2) angle [170.7(5)°]. The thermal behavior as well as the reactivity as soluble α-olefin polymerization catalyst were evaluated for 1.

Topics

• impedance spectroscopy
• compound
• single crystal X-ray diffraction
• single crystal
• Lithium
• Nuclear Magnetic Resonance spectroscopy
• tantalum
• elemental analysis
• niobium