856617-73-7Relevant academic research and scientific papers
Linear Hybrid Aminoborane/Phosphinoborane Chains: Synthesis, Proton-Hydride Interactions, and Thermolysis Behavior
Jaska, Cory A.,Lough, Alan J.,Manners, Ian
, p. 1090 - 1099 (2008/10/09)
The reaction of the lithiated phosphine-borane adducts Li[PPhR· BH3] or Li[CH2-PR2·BH3] with Me2NH·BH2Cl afforded the hybrid linear species Me2NH-BH2-PPhR-BH3 (1, R = Ph; 2, R = H) or Me2NH-BH2-CH2-PR2-BH3 (3, R = Ph; 4, R = Me). Single-crystal X-ray diffraction studies on 1 and 3, the first for linear hybrid aminoborane/phosphinoborane adducts, confirmed the expected four-coordinate N-B-P-B and N-B-C-P-B frameworks. In addition, interactions between the protic N-H and hydridic B-H hydrogen atoms resulted in short intermolecular H?H contacts for 1, whereas 3 was found to possess an exceptionally short intramolecular H?H distance of 1.95 A?. Solution and solid state infrared studies on 3 and 4 also suggest that these dihydrogen interactions were maintained even in dilute solution. Hydrogen bond strengths in the range of 7.9 to 10.9 kJ mol-1 indicate the presence of a relatively weak interaction. The thermal and catalytic dehydrocoupling reactivities of 1-4 were also investigated. Chain cleavage reactions were observed for 1 and 2 upon thermolysis at 130 °C to afford species such as Me2NH·BH3, [Me2N-BH2] 2, PhPRH·BH3 (R = Ph, H), PhPRH (R = Ph, H), Ph2PH-BH2-PPh2-BH3, and also the low molecular weight polyphosphinoborane [PhPH-BH2]n (Mw ～ 5000). Similar products were observed for the attempted catalytic dehydrocoupling reactions but under milder reaction conditions (50 °C). Thermolysis of 3 at 130 °C yielded the six-membered ring [BH 2-CH2-PPh2]2 (5), which presumably results from the dissociation of Me2NH·BH3 from 3. Thermolysis of 4 at 90 °C afforded Me2NH·BH3 and Me3P·BH3, in addition to a product tentatively assigned as [BH2-CH2-PMe2]2 (6).
