ORGANOMETALLIC TANTALUM COMPLEXES WITH PHOSPHINE, PHOSPHANIDO AND PHOSPHINIDENE LIGANDS - SYNTHESES AND CRYSTAL STRUCTURES OF [CP'TACL4(PH2(2,4,6-PR(3)(I)C6H2))], [CP'TA(MU-PPH(2))(PPH(2))](2)-CENTER-DOT-C7H8 AND TACL(MU-P(2,4,6-PR(3)(I)C6H2))](2)-CENTER-DOT-C7H8 (CP'=C(5)H(4)ME)

The reaction of [Cp'TaCl4] (Cp' = C(5)H(4)Me) with KPPh(2)(dioxane)(2) (1:1) in diethyl ether at room temperature gave the phosphanido-bridg ed tantalum(III) complex [Cp'Ta(mu-PPh(2))(PPh(2))](2) (1). C7H8 as bl ack crystals. [Cp'TaCl4] reacted with 2,4,6-triisopropylphenylphosphin e with formation of the adduct [Cp'TaCl4{PH2(2,4,6-(Pr3C6H2)-C-i)}] (2 ). Attempts to eliminate HCl from 2 with DBU (DBU = 1,8-diazabicyclo-[ 5,4,0]-undec-7-ene) gave the phosphinidene-bridged tantalum(IV) comple x [Cp'TaCl{mu-P(2,4,6-(Pr3C6H2)-C-i)}](2) (3). C7H8. It was shown inde pendently that DBU acts as a base and as a reducing agent. 1-3 were ch aracterized spectroscopically (IR, MS, NMR) as well as by crystal stru cture determinations. Copyright (C) 1996 Elsevier Science Ltd