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.