Syntheses, Crystal Structures and Reactivity of Organometallic Tantalum(IV) Phosphinidene Complexes: trans-[{Cp*TaCl(μ-PR)}2] (Cp* = C5Me5, R = Cy, tBu, Ph), cis- and trans-[{Cp*TaCl(μ-PMes)}2] (Mes = 2,4,6-Me3C6H2) and cis-[{Cp′TaCl(μ-PMes)}2] (Cp′ = C5H4Me)

Abstract

The reaction of [Cp*TaCl4] (Cp* = C5Me5) with LiPHR (1:1 or 1:2) gives the phosphinidene-bridged tantalum(IV) complexes trans-[{Cp*TaCl(μ-PR)}2] [R = Cy (1), tBu (2), Ph (3), 2,4,6-Me3C6H2 (Mes) (4b)]. When the reaction with LiPHMes is carried out in a 1:1 ratio, cis-[{Cp*TaCl(μ-PMes)}2] (4a) is also formed besides 4b. For comparison, cis-[{Cp′TaCl(μ-PMes)}2] (5) was prepared from [Cp′TaCl4] (Cp′ = C5MeH4) and LiPHMes (1:1). 1−5 are diamagnetic and were characterised spectroscopically (IR, MS; 1 H, 31P, 13C NMR). Crystal structure determinations on 1−5 showed the presence of dimeric phosphinidene-bridged TaIV complexes. The phosphinidene-bridged complexes 1, 3 and 4b do not react with acetone, benzophenone, acetonitrile, CS2 (1, 3), acetaldehyde (4b), or ethylaluminum dichloride (3). 3 reacts with moist acetone in the presence of traces of air to give the trinuclear cluster [{Cp*TaCl(μ2−O)}3(μ3-O)(μ2-O2PHPh)}] (6) in very low yield. With an excess of CyNC, 3 gives [Cp*TaCl(CNCy)4]Cl (7), which was characterised by 1H and 13C NMR spectroscopy and by crystal structure determination. As a minor product, [(Cp*TaCl2)2(μ2-O)(η2,μ2-P2Cy2)] (8) was also obtained in the reaction of [Cp*TaCl4] with LiPHCy. 6 and 8 were only characterised by crystal structure determination. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)