442640-62-2Relevant articles and documents
Chelate complexes of functionalized cycloheptatrienyl ligands: 17- And 18-Electron molybdenum complexes with linked cycloheptatrienyl-phosphane ligands and their use in transition metal catalysis
Tamm, Matthias,Baum, Kim,Luegger, Thomas,Froehlich, Roland,Bergander, Klaus
, p. 918 - 928 (2002)
The synthesis of P-functionalized molybdenum chelate complexes incorporating the linked cycloheptatrienyl-phosphane ligand [2-(diphenylphosphanyl)phenyl]cycloheptatrienyl, o-Ph2P-C6H4-C7H6, is described. The air-stable ligand precursor [2-(cyclohepta-2,4,6-trienyl)phenyl]diphenylphosphane (2) can be obtained in large quantities by addition of lithiated 2-BrC6H4PPh2 (1) to the tropylium cation C7H7+. Hydride abstraction employing the trityl cation, Ph3C+, results in the formation of the tricyclic phosphonium salt 3. The P-functionalized cycloheptatriene 2 acts as an eight-electron ligand on reaction with Mo(CO)6 to afford the cycloheptatriene-phosphane complex [(o-Ph2PC6H4-n 6C7H7)Mo(CO)2(P-Mo)] (4) as a single, chiral regioisomer, which undergoes clean hydride abstraction on treatment with (Ph3C)BF4. The resulting cationic cycloheptatrienyl-phosphane complex 5 reacts with sodium bromide to yield the uncharged "chiral-at-metal" complex [(o-Ph2PC6H4-n 7C7H6)Mo(CO)Br(P-Mo)] (6). This 18-electron complex can be oxidized with 0.5 equiv. of Br2 to give the paramagnetic dibromo complex 7, which is a versatile starting material for the preparation of the 17-electron mono- and dialkyl complexes [(o-Ph2PC6H4-n7- (C7H6)Mo(CH2SiMe3)X(P-Mo)] (X = Br, 8; X = CH2SiMe3, 9), In combination with Me3SiCH2MgCl, complexes 7 and 9 prove to be active catalysts for the ring-opening metathesis polymerization of norbornene. In addition, the X-ray crystal structures of 2, 4, 5·CH2Cl2, 7·CHCl3, 8, and 9·C6H14 are reported.
