186084-08-2Relevant articles and documents
Degradation and Modification of Metallaboranes: Reactions of the Hexaborane(10) Analogue nido-(PPh3)2(CO)OsB5H9 with Phosphines and the Crystal and Molecular Structure of [2,2,2-(PPH3)2(CO)-nido-2-OsB4H7-3-BH2.PPh2.Me]
McQuade, Paul,Hupp, Kevin,Bould, Jonathan,Fang, Hong,Rath, Nigam P.,et al.
, p. 5415 - 5424 (2008/10/08)
The reaction between the osmahexaborane [2,2,2-(PPh3)2(CO)-nido-2-OsB5H9] (1) and bases such as PPh3, PPh2Me, and PMe3 in refluxing CH2Cl2 affords unique adducts of the type [2,2,2-(PPh3)2(CO)-nido-2-OsB4H7-3-BH2.PR3] (2) for which spectroscopic data suggest the presence of a pendent boryl group. This was confirmed by a crystal structure determination for the PPh2Me adduct which shows that 2 is a nido-osmapentaborane with a terminal BH2.PPh2Me moiety on a basal boron atom adjacent to the metal. The reaction is reversible in the case of PPh3 and to a lesser extent PPh2Me, but not for PMe3. Heating the PPh3 adduct affords the osmahexaborane 1, liberating PPh3, but degradation to the osmapentaborane [2,2,2-(PPh3)2(CO)-nido-2-OsB4H8] (6) and BH3.PPh3 competes. The tendency to degrade to phosphine.borane increases markedly down the series R3 = Ph3, Ph2Me, and Me3. When the bidentate bases [1,2-(PPh2)2(CH2)2] and [1,3-(PPh2)2(CH2)3] (abbreviated as dppe and dppp, respectively) are used, two major products are observed in each case. One (3a) [2,2,2-(PPh3)2(CO)-nido-2-OsB4H7-3-(BH2.dppe)] (or 3b, BH2.dppp) is analogous to 2 with one end of the bidentate phosphine donor uncoordinated. In the other (4a) [2,2-(PPh3)(CO)-nido-2-OsB4H7-η(2)-3,2-(BH2.dppe)] (or 4b, BH2.dppp), the free end of the bidentate ligand has replaced a PPh3 group on Os. In the reaction of [(PPh2)2(CH2)] (abbreviated as dppm) with 1, only a species analogous to 3 is observed. The species 3b, the one involving dppp, has beenfurther modified at the free phosphine end of the ligand, to form [2,2, 2-(PPh3)2(CO)-nido-2-OsB4H7-3-(BH2.dppp.BH3)] (5).
