Degradation and Modification of Metallaboranes:  Reactions of the Hexaborane(10) Analoguenido-(PPh₃)₂(CO)OsB₅H₉with Phosphines and the Crystal and Molecular Structure of [2,2,2-(PPh₃)₂(CO)-nido-2-OsB₄H₇-3-BH₂·PPh₂Me]

Abstract

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-η2-3,2-(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 been further modified at the free phosphine end of the ligand, to form [2,2,2-(PPh3)(CO)-nido-2-OsB4H7-3-(BH2·dppp·BH3)] (5).

Substitution of the laser borane anti-B18H22 with pyridine: a structural and photophysical study of some unusually structured macropolyhedral boron hydrides

“…The loss of boron vertices is obviously a key part of the process to give 3a. Clues for the mechanism may derive from the reaction of [(PPh3)2(CO)OsB5H9] with phosphines L, which quantitatively and reversibly afford [(PPh3)2(CO)OsB4H7(BH2L)] in solution 38,39 -here, in the formation of the cluster-bound exopolyhecral {BH2L} moiety, the two-electron ligand L has clearly engendered an extrusion of a boron vertex. In macropolyhedral systems, reaction of PMe2Ph with S2B17H17 results in loss of a boron vertex to give [S2B16H14(PMe2Ph)2] and [S2B16H16(PMe2Ph)]; of these, the latter has some structural similarities to compound 3a.…”

[BH3·PPh2CH2C6H4CH2PPh2·Ru(p-cym)Cl2]: A New Bifunctional Compound and Prototype of a Linked Borane/Metal Cluster Species

“…23, 1999 5469 the dppf (1,1′-bis(diphenylphosphino)ferrocene) ligand, which has been shown to chelate metals coordinating to boron atoms in B 3 H 7 12 and, in studies pertinent to this one, link a series of identical borane species ranging from BH 3 to systems such as SB 9 H 11 and C 2 B 10 H 12 . 13 Our formation of 3 relates to other work in our laboratory involving the formation of linked cluster systems, 14,15 and we intend to report on these soon.…”

Reaction of 2‐Butyne with nido ‐[1,2‐(Cp*RuH) 2 B 3 H 7 ]: Improved Kinetic Control Leads to Metallacarboranes of Novel Composition and Structure

“…The NMR spectra and the structure data show that the BH 2 fragment forms a BHB interaction with the terminal hydrogen atom of the basal boron atom it bridges, thus, 2 can also be considered to possess an exopolyhedral BH 3 unit. Although 2 is unique, related compounds are: a metallaborane with a terminal BH 2 PR 3 fragment;13 a ferraborane with a BH 3 unit replacing the hydrogen atom of a B‐H‐B bridge;14 and a compound with a BX fragment bridging two metal atoms 15…”