Preparation and Characterization of Novel Os-Diolefin Dimers:New Entry to Os-Cyclooctadiene Complexes

摘要

The complex [H(EtOH)_2][{OsCl(eta~4-COD)}_2(mu-H)(mu-Cl)_2] (1) has been prepared in high yield by treatment of OsCl_3 centre dot 3H_2O (54% Os) with 1,5-cyclooctadiene in ethanol under reflux.Under air,it is unstable and undergoes oxidation by action of O_2 to afford the neutral derivative {OSCl(ETA~4-COD)}_2(MU-H)(MU-Cl)_2 (2).The terminal chlorine ligands of the anion of 1 are activated toward nucleophilic substitution.Thus,reaction of the salt [NBu_4][{OsCl(eta~4-COD)}_2-(mu-H)(mu-Cl)_2] (1a) with NaCp in toluene gives [NBU_4][{OS(ETA~1-C_5H_5)(ETA~4-COD)}(MU-H)(MU-Cl)_2{OSCl(ETA~4-COD)}] (3) as a result of the replacement of one of the terminal chlorine atoms by the cyclopentadienyl ligand.The CH_2 group of the latter can be deprotonated by the bridging methoxy ligand of the iridium dimer [lr(mu-OMe)(mu~4-COD)]_2.The reaction leads to the trinuclear derivative [NBu_4][{(eta~4-COD)lr(eta~5-C_5H_4-eta~1)Os(eta~4-COD)}(mu-H)(mu-Cl)_2{OsCl(eta~4-COD)}] (4) containing a bridging C_5H_4 ligand that is eta~1 -coordinated to an osmium atom of the dimeric unit and eta~5-coordinated to the Ir(eta~4-COD) moiety.Salt 1a also reacts with LiC ident to CPh.In this case,the reaction produces the substitution of both terminal chlorine ligands to afford the bis(alkynyl) derivative [NBu_4][{Os(C ident to CPh)(eta~4-COD)}_2(mu-H)(mu-Cl)_2] (5).Complexes 1,2,3,and 4 have been characterized by X-ray diffraction analysis.Although the separations between the osmium atoms are short,between 2.6696(4) and 2.8633(5) A,theoretical calculations indicate that only in 2 is there direct metal-metal interaction,as the bond order is 0.5.