CHEMISTRY OF RING-BRIDGED BIS (ETA-5-CYCLOPENTADIENYL) LIGANDS - DERIVATIVES OF ALPHA, ALPHA'-DICYCLOPENTADIENYL-META-XYLENE

The synthesis of the ligand α, α-dicyclopentadienyl-m-xylene (1) is reported, I was found to polymerize readily; however, reaction with sodium hydride, before extensive polymerization had occurred, gave the dianion of disodium (m-phenylenedimethylene)dicyclopentadienide (2). 2 was used to prepare additional derivatives of the type m-C6H4(CH2C5H4R)2, where R=CH3 or Si(CH3)3. The thermolysis of Mo(CO)6 and the photolysis of W(CO)6 with dianion 2 in tetrahydrofuran generated m-C6H4(CH2C5H4M(CO)3)22-, where M=Mo (5) and W (6). These metallo dianions were reacted with alkyl halides to prepare m-C6H4(CH2C5H4M(CO)3R)2, where M=Mo and W and R=CH3 and CH2CH3. The chemistry of the bridged molybdenum derivatives was examined in more detail with R=H, I derivatives being prepared. The hydrido derivative was found to reduce 1, 3-pentadiene and phenylacetylene with the subsequent formation of complex 14, m-C6H4[CH2C5H4Mo(CO)3]2. A better preparation of 14 involved the reaction of 1, 2-dibromoethane with dianion 5 in a 1:1 ratio. Photolysis of the methylmolybdenum derivative in the presence of triphenylphosphine affords m-C6H4-[CH2C5H4Mo(CO)2CH3P(C6H5)3]2. © 1979, American Chemical Society. All rights reserved.