Tethered Boryl and Base-Stabilized Borylene Osmium Complexes from the Reaction of Os(BCl2)Cl(CO)(PPh3)2 with 2-Aminopyridine

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• 作者：Clifton E. F. Rickard ; Warren R. Roper ; Alex Williamson ; and L. James Wright
• 刊名：Organometallics
• 出版年：2002
• 出版时间：October 28, 2002
• 年：2002
• 卷：21
• 期：22
• 页码：4862 - 4872
• 全文大小：229K
• 年卷期：v.21,no.22(October 28, 2002)
• ISSN：1520-6041

文摘

Reaction between Os(BCl₂)Cl(CO)(PPh₃)₂ and 2-aminopyridine in the presence of ethanolleads to a mixture of two products. In the first, replacement of one chloride on thedichloroboryl ligand through condensation with the amino function and coordination of thepyridine nitrogen atom to osmium leads to the tethered, six-coordinate boryl complex Os[BCl(NHC₅H₄N)]Cl(CO)(PPh₃)₂ (1). In the second, the direction of addition of the aminopyridine is reversed, leading to the tethered, pyridine-stabilized borylene complex Os[B(OEt)(NC₅H₄NH)]Cl(CO)(PPh₃)₂ (2). The five-membered chelate ring formed in 1 is stable andpersists through reactions involving replacement of chloride both at osmium and at boron.When 1 is treated with NaBr or with NaBH₄, replacement of chloride at osmium occursexclusively, leaving the B-Cl bond intact and giving Os[BCl(NHC₅H₄N)]Br(CO)(PPh₃)₂ (3)or Os[BCl(NHC₅H₄N)]H(CO)(PPh₃)₂ (4), respectively. Replacement of chloride at boronrequires the assistance of AgSbF₆, and the following derivatives of 1 have been characterized: Os[B(OH)(NHC₅H₄N)]Cl(CO)(PPh₃)₂ (5) (with 1 equiv of AgSbF₆), [Os{B(OH)(NHC₅H₄N)}(CO)(MeCN)(PPh₃)₂]SbF₆ (6) (with 2 equiv of AgSbF₆ in MeCN), and [Os{B(OEt)(NHC₅H₄N)}(CO)₂(PPh₃)₂]SbF₆ (7) (with 2 equiv of AgSbF₆ and CO in the presence of EtOH). Reactionbetween Os(BCl₂)Cl(CO)(PPh₃)₂ and 2-(methylamino)pyridine leads to only one product, thetethered, pyridine-stabilized borylene complex Os[BCl(NC₅H₄NMe)]Cl(CO)(PPh₃)₂ (8). Fourfurther pyridine-stabilized borylene complexes have been derived from 8. Reaction of 8 withNaBH₄ gives Os[BCl(NC₅H₄NMe)]H(CO)(PPh₃)₂ (9), and 9 is hydrolyzed by water to Os[B(OH)(NC₅H₄NMe)]Cl(CO)(PPh₃)₂ (10). Ethanol converts 8 to Os[B(OEt)(NC₅H₄NMe)]Cl(CO)(PPh₃)₂ (11), and 2 equiv of AgSbF₆ in acetonitrile converts 8 to [Os{B(OEt)(NC₅H₄NMe)}(CO)(MeCN)(PPh₃)₂]SbF₆ (12). Crystal structures of complexes 2-6 and 9 are reported.