Syntheses, Crystal Structures and Reactivity of Organometallic Tantalum (IV) Phosphinidene Complexes: trans-[{Cp~*TaCl(mu-PR)}_2] (Cp~* = C_5Me_5, R = Cy, tBu, Ph), cis- and trans-[{Cp~*TaCl(mu-PMes)}_2] (Mes = 2,4,6-Me_3C_6H_2) and cis-[{Cp'TaCl(mu-

摘要

The reaction of [Cp~*TaCl_4] (Cp~* = C_5Me_5) with LiPHR (1:1 or 1:2) gives the phosphinidene-bridged tantalum(IV) complexes trans-[{Cp~*TaCl(mu-PR)}_2] [R = Cy (1), tBu (2), Ph(3), 2,4,6-Me_3C_6H_2(Mes)(4b)]. When the reaction with LiPHMes is carried out in a 1:1 ratio, cis-[{Cp~*TaCl(mu-PMes)}_2] (4a) is also formed besides 4b. For comparison, cis-[{Cp'TaCl(mu-PMes)}_2] (5) was prepared from [Cp'TaCl_4] (Cp' = C_5MeH_4) and LiPHMes (1:1). 1-5 are diamagnetic and were characterised spectroscopically (IR, MS; ~1H, ~(31)P, ~(13)C NMR). Crystal structrue determinations on 1-5 showed the presence of dimeric phosphinidene-bridged Ta~(IV) complexes. The phosphinidene-bridged complexes 1,3 and 4b do not react with acetone, benzophenone, acetonitrile, CS_2(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(mu-O)}_3(mu_3-O)(mu_2-O_2PHPH)] (6) in very low yield. With an excess of CyNC, 3 gives [Cp~*TaCl(CNCy)_4]Cl (7), which was characterised by ~1H and ~(13)C NMR spectroscopy and by crystal structure determination. As a minor product, [(Cp~*TaCl_2)_2(mu_2-O)(eta~2,mu_2-P_2Cy_2)] (8) was also obtained in the reaction of [Cp~*TaCl_4] with LiPHCy. 6 and 8 were only charasterised by crystal structure determination.