Synthesis, structure and chemistry of low-boron containing molybdaborane: Arachno-[Cp*Mo(CO)₂B₃H₈]

Abstract

Room temperature photolysis of [Cp*Mo(CO)₃Me], 1 with excess of [BH₃·THF] led to the isolation of hydrogen-rich arachno-[Cp*Mo(CO)₂B₃H₈], 2 in good yield. The geometry of arachno-2 consists of a butterfly core similar to that of 7 skeletal electron pairs tetraborane(10). Further, the metal fragment addition reaction of arachno-2 with [Fe₂(CO)₉] yielded a nido-[Cp*Mo(CO)₂B₃H₆Fe(CO)₃], 3 that plays a pivotal role in bringing a change in the geometry from arachno-2 to nido-3. The reaction of arachno-2 with [Ru₃(CO)₁₂], however, yielded known metal carbonyl compound [Cp*Mo(CO)₃]₂, 4. All the new compounds have been characterized in solution by mass spectrometry, IR, ¹H, ¹¹B, ¹³C NMR spectroscopy and the solid state X-ray structures of 2 and 3 were unequivocally established by X-ray diffraction analysis. Additionally, we have studied the bonding nature of compounds 2 and 3 with the help of density functional theory (DFT) calculations.