有機合成化学グループ： 鈴木(教)研究室（＆旧 増山研究室）

Organic Synthesis Group, Sophia University

abstracts_2014_1

Haptotropic Shift of [5]Cumulenes in Zirconocene Complexes and Effects of Steric Factors
Noriyuki Suzuki,*Takao Yoshitani,Shota Inoue,Daisuke Hashizume,Hajime Yoshida,Meguru Tezuka,Keisuke Ida,Sayoko Nagashima,Teiji Chihara,Osamu Kobayashi,Shinkoh Nanbu,Yoshiro Masuyama
Organometallics, 2014, 33, 5220-5230.
DOI: 10.1021/om500536c

Zirconium complexes of some[5]cumulene derivatives were studied for their variable coordination modes andhaptotropic shifts. Some [5]cumulene compounds reacted with zirconocene(II) species to afford 1-zirconacyclopent-3-yne complexes that have five-memberedcycloalkyne structures. Only a few [5]cumulene compounds affordedh2-coordinated complexes in the presence of neutral ligands such as trimethylphosphine andtert-butyl isocyanide. Interconversion between the five-membered structure and the eta2-complexwas observed. Investigation on [5]cumulene derivatives of various cycloalkylidene moieties indicated that the eta2-complexwas preferred when the [5]cumulene has bulkier substituents. A [5]cumulene with 2,2,6,6-tetramethylcyclohexylidene groups much preferred the1-zirconacyclopent-3-yne structure to eta2-coordination. In sharp contrast, eta2-coordinated complex was favored for a [5]cumulene with 2,2,7,7-tetramethylcycloheptylidene groups in the presence of PMe3. Small differences in steric environments caused totally different reactivity in [5]cumulene complexes. DFTcalculations on the formation enthalpy were consistent with the experimental results, although that cannot fully rationalize the difference.


[5]クムレン類のジルコノセン錯体におけるハプトトロピックシフトと立体効果
鈴木 教之、吉谷孝雄、井上翔太、橋爪大輔、吉田　一、手塚　還、井田圭亮、長島佐代子、千原貞次、小林　理、南部伸孝、増山芳郎
Organometallics, 2014, 33, 5220-5230.
DOI: 10.1021/om500536c.
ジルコニウムと[5]クムレン類縁体が形成する錯体において、その配位形態の変換について検討した。[5]クムレン類はジルコニウムに配位して五員環アルキン錯体14と、η2-配位錯体15を取りえることがわかった。[5]クムレン上の置換基とシクロペンタジエニル基間の立体反発が大きい場合15を形成しやすい。[5]クムレンの末端にわずかに異なる嵩高さをもつシクロアルキリデン基を導入し反応を比較したところ、六員環14dと七員環14eとでその反応性が著しく異なることが明らかとなった。トリメチルホスフィンを加えたところ14dは全く変化しなかった一方、14eは高収率で15eを与えた。