Bonding Situation of σ‐E−H Complexes in Transition Metal and Main Group Compounds

Abstract

The ambiguous bonding situation of σ-EÀ H (E = Si, B) complexes in transition metal compounds has been rationalized by means of Density Functional Theory calculations. To this end, the combination of the Energy Decomposition Analysis (EDA) method and its Natural Orbital for Chemical Valance (NOCV) extension has been applied to representative complexes described in the literature where the possible η 1 versus η 2 coordination mode is not unambig-uously defined. Our quantitative analyses, which complement previous data based on the application of the Quantum Theory of Atoms in Molecules (QTAIM) approach, indicate that there exists a continuum between genuine η 1 and η 2 modes depending mainly on the strength of the backdonation. Finally, we also applied this EDA-NOCV approach to related main-group species where the backdonation is minimal.

σ-GeH and Germyl Cationic Pt(II) Complexes

“…Similar to 1.2·HSiEt 3 , the σ(Ge–H) σ*(Pt–C) interaction is significantly stronger (Δ E orb (1) = −40.8 kcal mol –1 ) than the d(Pt) → σ*(Ge–H) backdonation (Δ E orb (2) = −17.6 kcal mol –1 , Figure 4 ). These values are rather similar to those reported for the analogous platinum σ-SiH complex (Δ E orb (1) = −41.8 kcal mol –1 and Δ E orb (2) = −20.7), 13 thus indicating that the donor and acceptor abilities of the σ(Ge–H) bond strongly resembles those of σ(Si–H) bonds. Despite that, it becomes evident that the backdonation in this germane complex is substantial, which suggests a coordination mode intermediate between the extreme situations represented by η 1 (i.e., no backdonation) and η 2 bonding modes.…”

“…This methodology has been chosen to enable a direct comparison with the data recently reported by us for its silicon counterpart σ-SiH complex 1.2·HSiEt 3 . 13 Once again, it is confirmed that the main contribution to the total interaction (Δ E int ) between the [Pt] + and HGeEt 3 fragments in complex 1.2·HGeEt 3 comes from the electrostatic attractions (Δ E elstat ), which represent ca. 57% of the total attractive interactions, and are almost twice as strong as the orbital interactions (Δ E orb ), contributing ca.…”

X-type silyl ligands for transition-metal catalysis

“…30 DFT calculations have been conducted to elucidate the bonding situations in transition-metal hydrosilane complexes, which indicate a continuum of electronic structures between genuine Z 1 -SiH and Z 2 -SiH modes depending mainly on the strength of the backdonation. 27,[31][32][33][34] The ready availability of hydrosilanes, combined with the unique reactivity of silyl-metal complexes, has greatly inspired chemists to explore silyl ligands and silyl-metal complexes for transition-metal catalysis, particularly for the catalytic activation of molecules having H-H, C-H, B-H, or Si-H bonds. 17,29 The silyl groups acting as supporting ligands can significantly change or enhance the catalytic performance of metal complexes, especially in the case of bidentate and pincer forms.…”

“…30 DFT calculations have been conducted to elucidate the bonding situations in transition-metal hydrosilane complexes, which indicate a continuum of electronic structures between genuine η 1 -SiH and η 2 -SiH modes depending mainly on the strength of the backdonation. 27,31–34…”