Synthesis and N M R Study of ( rf - l , 4 - diphenyl - l , 3 - butadiene ) tricarbonyl - chromium ( O )

Arenes have been widely used as 7r-accepting ligand in organometallic chemistry. Particularly, arene complexes of the tricarbonylchromium frag­ ment have found applications as catalyst in the synthesis of organic compounds including several biochemical interest [1] and therefore been studied extensively [2]. Complexes of conjugated diene of the tetracarbonylchromium fragment are also well characterised compounds [3] of potential interest for the catalytic reactions of dienes, like hydroge­ nation [4], Complexes of a ligand containing both the aromatic ring and a conjugated diene unit also seem to be interesting for catalytic applications as well as for a structural study. 1,4-Diphenyl-1,3-bu­ tadiene (1 ) is one of the representatives for such ligands. 1 has been found to coordinate to the tricarbonyliron(O) moiety through its diene unit [5] and to tricarbonyl-chromium(O) units through one or both of its phenyl rings [6, 7]. However, both of these early reports on (rj61,4-diphenyl1,3-butadiene)tricarbonylchromium(O) (2) and {rf'.rf1,4diphenyl1,3-butadiene)bis(tricarbonylchromium(0)) (3) lack on N M R spectroscopic data which would provide further structural information. This prompted us some years ago to study the coordi­ nation properties of 1 towards carbonylmetal frag-