Identification of the endo,exo isomer of 6,9-(PMe2Ph)2-arachno-B10H12 by nuclear magnetic resonance spectroscopy

Reaction of PMe2Ph with nido-B10H14 results in the formation of the previously unsuspected endo,exo isomer of arachno-B10H12(PMe2Ph)2(ca. 85%) admixed with the expected exo,exo isomer (ca. 15%). Mild heating converts the endo,exo isomer into the exo,exo one. The mixture is readily analysed by multiple resonance and difference n.m.r. spectroscopy.