|Budget Amount *help
¥1,900,000 (Direct Cost : ¥1,900,000)
Fiscal Year 1991 : ¥600,000 (Direct Cost : ¥600,000)
Fiscal Year 1990 : ¥1,300,000 (Direct Cost : ¥1,300,000)
Two axial sites of transition metal complexes of syn-crown thioethers are stereochemically different environments ; the site surrounded by the ring carbon atoms is congested, while the opposite site is uncongested. Therefore, two Pi-acids or anionic ligands possessing different steric demands are expected to be discrimianted on axial coordination. This was achieved by trans-Mo (eta^2-O, C-PhNCO) (eta^2-C, NPhNCO) (syn-Me_8aneS_4), where the bulky eta^2-O, C-PhNCO coordinates specifically at the uncongested site. The novel recognition of the C=O and C=N bondds of PhNCO was proved be steric in origin by EHMO and molecular mechanics calculations. The ring size effect of crown thioethers upon the discrimination of axial ligands was demonstrated cleary by trans-RuH (Cl) L (L=Me_4aneS_4, Me_6aneS_4, Me_8aneS_4). The hydrido and Cl ligands in the Me_4aneS_4 and Me_6aneS_4, complexes occupy the congested axial site respectively, while the axial sites in the Me_8aneS_4 complex failed to discriminate the two anionic ligands. The X-ray structures of the two former complexes suggest that the attractive van der Waals interactions between the axial ligand at the congested site and axial CH_2 hydrogen atoms are responsible for the recognition. Stereospecific alkylation of the terminal sulfide located at the congested axial site in trans-Mo (S)_2 (syn-Me_8aneS_4) with Mel and PhCH_2Br took place readily to give novel MoS_6 complexes trans-Mo (S) (SR) (syn-Me_8aneS_4) (R=Me, PhCH_2) containing the three distinctive types of sulfur donors, thiolate, terminal sulfide, and thioether. A protonlation with HBF_4 took place similarly to give trans-(Mo (S) (F) (syn-Me_8aneS_4) )^+ and (MO_2 (S)_2 (mu-S) (syn-Me_8aneS_4)_2)^<2+>. The x-ray structural study and electronic spectrum show that the latter complex contains a novel extended linear S=Mo*S*Mo=S conjugated linkage.