Chemical analysis of bicyclo(1.1.1) (R2E)3Bi2 complexes

In a recent study researchers Drs. Monakhov and Gourlaouen (University of Strasbourg) investigated fundamental bonding and electronic structure aspects of heteroelemental (R₂E)₃Bi₂ bicyclo(1.1.1)pentane complexes (E = C, Si, Ge, Sn, Pb; R = H) and their ML₂-functionalized derivatives (M = Ni, Pd, Pt; L = PH₃). These were used as models for experimentally characterized compounds (R’₂Ge)₃Bi₂ and (R’₂Ge)₃Bi₂PtL₂ and computationally analyzed in order to understand a broad spectrum of heteronuclear E-Bi, E-M, and Bi-M bonding interactions. This insight could guide synthesis of novel compounds with intriguing bonds.

Insight into the electronic structure of model compounds was obtained with various chemical analysis tools in ADF. Natural bond order (NBO), electron localization function (ELF), and energy decomposition analysis (EDA) indicated that in the non-carbon containing bicyclo(1.1.1) compounds, bonding arises from three carbenoid H₂E: units (E = Si, Ge, Sn, Pb) interacting with two Bi(0) atoms. Especially (H₂Si)₃Bi₂ and its (H₂Si)₃Bi₂[ML₂] derivatives formed upon the carbenoid-like insertion of ML₂ into the Si-Bi bond, show great stability, and are thus attractive synthetic target classes.

Top: ELF surfaces and contours of the ionically bonded (H₂C)₃Bi₂ and covalently bonded (H₂Ge)₃Bi₂ complexes (ηiso plot is 0.65) show, respectively, the absence and existence of E-Bi basins for the former and the latter and demonstrate the absence of any E-E and Bi-Bi bonding interactions. Bottom: Quantitative MO diagrams for (H₂Ge)₃Bi₂ (left) and its Pt-functionalized derivative (H₂Ge)₃Bi₂[Pt(PH₃)₂] (right) with most relevant MOs shown (±0.03 isosurface value).

K. Yu. Monakhov and C. Gourlaouen, On the insertion of ML2 (M = Ni, Pd, Pt; L = PH3) into the E-Bi bond (E = C, Si, Ge, Sn, Pb) of a bicyclo[1.1.1]pentane motif: A case for a carbenoid-stabilized Bi(0) species? Organometallics 31, 4415-4428 (2012)