Syntheses of metal complexes of lower boranes and its development to metal cluster compounds.

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1. B_2H_4・2P(CH_3)_3 has been known to coordinate to a metal through two vicinal hydrogen atoms. However, the central metal ions are only those with d^<10> electron configuration. To elucidate if it can be coordinated to a metal ion with an electron configuration other than d^<10>, we tried to synthesize B_2H_4・2P(CH_3)_3 complexes using photochemical reactions of group 6 transition metal carbonyls. Both [M(CO)_4{B_2H_4・2P(CH_3)_3}] and [M(CO)_5{B_2H_4・2P(CH_3)_3} (M=Cr, Mo, W) were prepared. B_2H_4・2P(CH_3)_3 acts as a bidentate ligand in the former complexes, but as a unidentate in the latter complexes. The latter complexes are not only the first examples in which B_2H_4・2P(CH_3)_3 acts as a unidentate ligand, but also the first ones in which polyborane acts as a unidentate ligand. Dynamic behavior of the complexes in solutions was elucidated using NMR method.2. Although many coordination complexes with anionic monoboranes such as BH_4^-, have been prepared, no complexes in which neu … More tral monoborane is coordinated has been reported yet. Photochemical reaction of group 6 transition metal carbonyls was used for the syntheses of the complexes with neutral monoborane-Lewis base adducts, and complexes, [M(CO)_5(BH_3・L)] (M=Cr, Mo, W ; L=PMe_3. PPh_3, NMe_3) were prepared, and revealed to be unidentate complexes.3. As [Cu{B_2H_4・2P(CH_3)_3}_2]X where Cu (I) was coordinated tetrahedrally by only four hydrogen atoms was synthesized, we investigated to synthesize mixed borane complexes in which Cu (I) is coordinated with only hydrogen atoms. Cu(B_3H_8){B_2H_4・2P(CH_3)_3} was synthesized.4. It was revealed that Wade rule which is effective to predict the structures of cluster compounds is also applicable to the metal complexes obtained in this project. Thus electron-precise borane complexes obtained in our project can also be described as metallaboranes. Unidentate B_2H_4・2P(CH_3)_3 complexes can be regarded model compounds for the parent borane which has not been synthesized yet. Less