Convenient Solution Route To Alkylated Pentalene Ligands: New Metal Monoalkylpentalenyl Complexes

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• 作者：Simon C. Jones ; Paul Roussel ; Tony Hascall ; and Dermot O'Hare
• 刊名：Organometallics
• 出版年：2006
• 出版时间：January 2, 2006
• 年：2006
• 卷：25
• 期：1
• 页码：221 - 229
• 全文大小：176K
• 年卷期：v.25,no.1(January 2, 2006)
• ISSN：1520-6041

文摘

Carbene-induced rearrangement of 8,8-dibromobicyclo[5.1.0]octa-2,4-dienes and subsequent in situdeprotonation of the dihydropentalenes formed represents a straightforward and versatile solution routeto pentalene ligands for use in organometallic chemistry. We report here the synthesis of 6-alkyl-substituted8,8-dibromobicyclo[5.1.0]octa-2,4-dienes and their rearrangement to give correspondingly substitutedpentalene ligands. Generation of methyl-substituted dihydropentalenes from 8,8-dibromo-6-methylbicyclo[5.1.0]octa-2,4-diene followed by monodeprotonation with TlOEt gives methylhydropentalenyl salts, Tl(C₈H₆Me), as a mixture of isomers. Formation of both 1-Me and 3-Me isomers of Re(C₈H₆Me)(CO)₃from these Tl species shows that monodeprotonation of the dihydropentalenes occurs at the unsubstitutedring. No evidence for the 2-Me isomer is observed, consistent with the rearrangement mechanism reportedin the literature. Likewise, rearrangement of 8,8-dibromo-6-alkylbicyclo[5.1.0]octa-2,4-dienes (R = Me,Et, ⁱPr) and subsequent double deprotonation with ⁿBuLi in the presence of DME affords the pentalenylsalts Li₂(C₈H₅R)·xDME. X-ray crystallographic studies of the dinuclear Mn organometallics anti-[Mn(CO)₃]₂(C₈H₅R) synthesized from the Li salts confirm that these alkylated pentalene ligands are substitutedat the 1-position exclusively. The crystal structure of a model hydropentalenyl complex, Re(C₈H₇)(CO)₃,is also reported.