CONVENIENT SYNTHESIS OF NEW BINUCLEATING LIGANDS DERIVED FROM 1,3-DIACETYLBENZENE - POSSIBLE PRECURSORS FOR OLIGOMERIC ORGANOMETALLIC MATERIALS

Bis-phosphine 1,3-bis(diphenylphosphinoacetyl)benzene (LH2) is obtained in high yield by reacting Ph2PCl with bis(lithium anolate) derived from 1,3-diacetylbenzene in tetrahydrofuran. Its oxidation by air gives quantitatively the corresponding double beta-ketophosphine oxide. The ligand LH2 reacts with [(omicron-C6H4CH2NMe2)PdCl]2 to give the binuclear complex [{(omicron-C6H4CH2NMe2)PdCl}2(mu-LH2)] in which the bis-phosphine behaves as a bridging ligand. The latter complex is conveniently converted by prolonged treatment with sodium hydride in tetrahydrofuran into the bis-enalto complex [{(omicron-C6H4CH2NMe2)Pd}2(mu-L)] in which the bridging ligand L contains two chelating subunits. Reaction of LH2 with [Pd(acac)2] leads to oligomeric material of formula (PdL)n. Mass spectroscopic measurements suggest the presence of a tetrameric species, (PdL)4, present in the reaction mixture.