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Unprecedented flexibility of the 1,1 '-bis(o-carborane) ligand: catalytically-active species stabilised by B-agostic B-H -> Ru interactionsстатья
Статья опубликована в высокорейтинговом журнале
Информация о цитировании статьи получена из
Web of Science,
Scopus
Статья опубликована в журнале из списка Web of Science и/или Scopus
Дата последнего поиска статьи во внешних источниках: 10 августа 2018 г.
- Авторы: Riley Laura E., Chan Antony P.Y, James Taylor, Man Wing Y., David Ellis, Rosair Georgina M., Welch Alan J., Sivaev Igor B.
- Журнал: Dalton Transactions
- Том: 45
- Номер: 3
- Год издания: 2016
- Издательство: Royal Society of Chemistry
- Местоположение издательства: United Kingdom
- Первая страница: 1127
- Последняя страница: 1137
- DOI: 10.1039/c5dt03417e
- Аннотация: Doubly-deprotonated 1,1’-bis(o-carborane) reacts with [RuCl2(p-cymene)]2 to afford [Ru(κ3-2,2’,3’-{1-(1’-1’,2’-closo-C2B10H10)-1,2-closo-C2B10H10})(p-cymene)] (1) in which 1,1’-bis(o-carborane) acts as an X2-(C,C’)L ligand where “L” is a B3’–H3’⇀Ru B-agostic interaction, fluctional over four BH units (3’, 6’, 3 and 6)at 298 K but partially arrested at 203 K (B3’ and B6’). This interaction is readily cleaved by CO affording [Ru-(κ2-2,2’-{1-(1’-1’,2’-closo-C2B10H10)-1,2-closo-C2B10H10})(p-cymene)(CO)] (2) with the 1,1’-bis(o-carborane)simply an X2(C,C’) ligand. With PPh3 or dppe 1 yields [Ru(κ3-,3’,3-{1-(1’-1’,2’-closo-C2B10H10)-1,2-closo-C2B10H10})(PPh3)2] (3) or [Ru(κ3-2,3’,3-{1-(1’-1’,2’-closo-C2B10H10)-1,2-closo-C2B10H10})(dppe)] (4)via unusually facile loss of the η-(p-cymene) ligand. In 3 and 4 the 1,1’-bis(o-carborane) has unexpectedly transformed into an X2(C,B’)L ligand with “L” now a B3–H3⇀Ru B-agostic bond. Unlike in 1 the B-agostic bonding in 3 and 4 appears non-fluctional at 298 K. With CO the B-agostic interaction of 3 is cleaved and a PPh3 ligand is lost to afford [Ru(κ2-2,3’-{1-(1’-1’,2’-closo-C2B10H10)-1,2-closo-C2B10H10})(CO)3(PPh3)](5), which exists as a 1 : 1 mixture of isomers, one having PPh3 trans to C2, the other trans to B3’. With MeCN the analogous product [Ru(κ2-2,3’-{1-(1’-1’,2’-closo-C2B10H10)-1,2-closo-C2B10H10})(MeCN)3(PPh3)] (6) is formed as only the former isomer. With CO 4 affords [Ru(κ2-2,3’-{1-(1’-1’,2’-closo-C2B10H10)-1,2-closo-C2B10H10})(CO)2(dppe)] (7), whilst with MeCN 4 yields [Ru(κ2-2,3’-{1-(1’-1’,2’-closo-C2B10H10)-1,2-closo-C2B10H10})(MeCN)2(dppe)] (8). In 5 and 6 the three common ligands (CO or MeCN)are meridional, whilst in 7 and 8 the two monodentate ligands are mutually trans. Compound 1 is an 18-e,6-coordinate, species but with a labile B-agostic interaction and 3 and 4 are 16-e, formally 5-co-ordinate,species also including a B-agostic interaction, and thus all three have the potential to act as Lewis acid catalysts. A 1% loading of 1 catalyses the Diels–Alder cycloaddition of cyclopentadiene and methacrolein in CH2Cl2 with full conversion after 6 h at 298 K, affording the product with exo diastereoselectivity (de >77%). Compounds 1–8 are fully characterised spectroscopically and crystallographically.
- Добавил в систему: Сиваев Игорь Борисович