Aj. Welch et As. Weller, SYNTHESIS AND REACTIVITY OF 7,9-DIPHENYL-NIDO-CARBAUNDECABORANES - REARRANGEMENT PROCESSES IN CARBAPLATINABORANES REVISITED, Journal of the Chemical Society. Dalton transactions, (7), 1997, pp. 1205-1212
A number of synthetic routes towards diphenyl nido-carbaborane [7,9-Ph
-2-7,9-nido-C2B9H10](-) have been elucidated. Base-induced degradation
of 1,7-Ph-2-1,7-closo-C2B10H10 afforded two isolable products [NEt3H]
-[7,9-Ph-2-x-OEt-7,9-nido-C2B9H9] (x = 3 1a or 2 1b), both of which co
ntain an ethoxide-substituted cage. The structural identity of la was
established by a single-crystal X-ray diffraction study. Fluoride-indu
ced degradation gave a product assigned as [NBu4][7,9-Ph-2-10-OH-7,9-n
ido-C2B9H9] 2, also studied crystallographically. Heating a solid samp
le of Cs[7,8-Ph-2-7,8-nido-C2B9H10] in a sealed tube under vacuum for
4 h at 300 degrees C afforded the target species [NEt3H][7,9-Ph-2-7,9-
nido-C2B9H10] 3, after cation metathesis. Deprotonation of 3 and react
ion with [PtCl2(PMe2Ph)(2)] afforded the new compound 1,1-(PMe2Ph)(2)-
2,4-Ph-2-1,2,4-closo-PtC2B9H9 4. Compound 4 has been characterised by
multinuclear (H-1, B-11 and P-31-{H-1}) NMR spectroscopy as well as a
single-crystal X-ray diffraction study. The isolation of this stable (
in refluxing toluene) compound having a 1,2,4-MC2B9 cage architecture
indicates that a hextuple-concerted diamond-square-diamond mechanism c
annot be operating in the spontaneous isomerisation of 1,2-Ph-2-3,3-(P
Me2Ph)(2)-3,1,2-closo-PtC2B9H9 below ambient temperature to afford 1,1
-(PMe2Ph)(2)-2,8-Ph-2-1,2,8-closo-PtC2B9H9. The new compounds 1,1-(PR3
)(2)-2,4-Ph-2-7-OEt-closo-1,2,4-PtC2B9H8 (R-3 = Me2Ph 5a or Et-3 5b),
both fully characterised by multinuclear NMR spectroscopy; have also b
een synthesized.