| Reactions between bidentate phosphines of the type PPh2(CH 2)nPPh2 and the air stable hexaborane(10) analogue nido-[(PPh3)2(CO)OsB5H9], generate the species [2,2,2-(PPh3)2(CO)nido -2-OsB4H7-3-BH2·PPh 2(CH2)nPPh2] (1) In solution species 1 undergoes intramolecular substitution to generate [2,2-(PPh3)(CO)-nido-2-OsB4H7 -η2-3,2-(BH2·PPh 2(CH2)aPPh2)] (2) and release free PPh3. This intramolecular substitution is observed when n = 2 and 3, but not when n = 1.; Species 1 can then undergo further reactions at the distal end of the attached phosphine with a series of electrophiles such as BH3·thf and [Ru(p-cym)X2]2 (X = Cl, I) to produce the bifunctional adducts [2,2,2-(PPh3)2(CO)- nido-2-OsB4H7-3-BH2·PPh 2(CH2)nPPh2·BH3] (3) and [2,2,2-(PPh3)2(CO)-nido -2-OsB4H7-3-BH2·PPh 2(CH2)nPPh2·Ru(p-cym)X 2] (4) respectively. Species 4 can be also be generated from the reaction of the mono-functionalized bidentate phosphines of the type [PPh2(CH2)nPPh2·Ru( p-cym)X2] (5) with 1.1H NMR spectroscopy indicated that the nidoosmapentaborane cluster was influencing the p-cymene ligand attached to the ruthenium center such that it exhibited diastereotopic behavior. This was confirmed by comparison of the 1 H NMR spectrum for 4 with those of the analogous species 5 and the bifunctional species [BH3PPh2(CH2)n PPh2·Ru(p-cym)X2] ( 6), which do not exhibit such behavior. The influence of the chiral osmaborane cluster was further confirmed by use of a chiral borane, which gave similar effects.; In an effort to avoid intramolecular substitution a modified approach was utilized. In a series of experiments, bidentate phosphines of the type PPh2XPPh2 (X = C6H4, CH2 C6H4CH2 and Fe(CSH4) 2) were used in an attempt to preclude the formation of species 2. This approach did indeed preclude the formation of species 2. However rather than a single product being isolated, three products were obtained. These were [2,2,2-(PPh3)2(CO)- nido-2-OsB4H7-3-BH2·PPh 2XPPh2] (7), a ‘dimeric’ species of the type [(2,2,2-(PPh3)2(CO)-nido-2-OsB 4H7-3-BH2)2PPh2XPPh 2] (8) and a bis-borane adduct of the type [2,2,2-(PPh3)2(CO)-nido-2-OsB 4H7-3-BH2·PPh2XPPh2·BH 3] (9). Species 7 is analogous to that obtained from bidentate phosphines containing an alkyl backbone, in that there is present a phosphine amenable to further derivatization. In solution, 7 then reacts further with a second molecule of (PPh3)2(CO)OsB 5 |
