From Saturated BN Compounds to Isoelectronic BN/CC Counterparts: An Insight from Computational Perspective

In the present study, the inorganic analogues of alkanes as well as their isoelectronic BN/CC counterparts that bridge the gap between organic and inorganic chemistry are comparatively studied on the grounds of static DFT and Car–Parrinello molecular dynamics simulations. The BN/CC butanes CH 3 CH 2 BH 2 NH 3 , BH 3 CH 2 NH 2 CH 3 , and NH 3 CH 2 BH 2 CH 3 were considered and compared with their isoelectronic counterparts NH 3 BH 2 NH 2 BH 3 and CH 3 CH 2 CH 2 CH 3 . In addition, systematical replacement of the NH 2 BH 2 fragment by the isoelectronic CH 2 CH 2 moiety is studied in the molecules H 3 N(NH 2 BH 2 ) 3– m (CH 2 CH 2 ) m BH 3 (for m =0, 1, 2, or 3) and H 3 N(NH 2 BH 2 ) 2– m (CH 2 CH 2 ) m BH 3 (for m =0, 1, or 2). The DFT and Car–Parrinello simulations show that the isosteres of the BN/CC butanes CH 3 CH 2 BH 2 NH 3 , BH 3 CH 2 NH 2 CH 3 , and NH 3 CH 2 BH 2 CH 3 and of larger oligomers of the type (BN) k (CC) l where k ≥ l are stable compounds. The BN/CC butane H 3 NCH 2 CH 2 BH 3 spontaneously produces molecular hydrogen at room temperature. The reaction, prompted by very strong dihydrogen bonding NH⋅⋅⋅HB, undergoes through the neutral, hypervalent, pentacoordinated boron dihydrogen complex RBH 2 (H 2 ) [R=(CH 2 CH 2 ) n NH 2 ]. The calculations suggest that such intermediate and the other BN/CC butanes CH 3 CH 2 BH 2 NH 3 , BH 3 CH 2 NH 2 CH 3 , and NH 3 CH 2 BH 2 CH 3 as well as larger BN/CC oligomers are viable experimentally. A simple recipe for the synthesis of CH 3 CH 2 BH 2 NH 3 is proposed. The strength of the dihydrogen bonding appeared to be crucial for the overall stability of the saturated BN/CC derivatives.