Reactivity of Dicoordinated Stannylones (Sn⁰) versus Stannylenes (Sn^II): An Investigation Using DFT‐Based Reactivity Indices

Abstract

The reactivity of dicoordinated Sn(0) compounds, stannylones, is probed using density functional theory (DFT)-based reactivity indices and compared with the reactivity of dicoordinated Sn(II) compounds, stannylenes. For the former compounds, the influence of different types of electron-donating ligands, such as cyclic and acyclic carbenes, stannylenes and phosphines, on the reactivity of the central Sn atom is analyzed in detail. Sn(0) compounds are found to be relatively soft systems with a high nucleophilicity, and the plots of the Fukui function f(-) for an electrophilic attack consistently predict the highest reactivity on the Sn atom. Next, complexes of dicoordinated Sn compounds with different Lewis acids of variable hardness are computed. In a first part, the double-base character of stannylones is demonstrated in interactions with the hardest Lewis acid H(+). Both the first and second proton affinities (PAs) are high and are well correlated with the atomic charge on the Sn atom, probing its local hardness. These observations are also in line with electrostatic potential plots that demonstrate that the tin atom in Sn(0) compounds bears a higher negative charge in comparison to Sn(II) compounds. Stannylones and stannylenes can be distinguished from each other by the partial charges at Sn and by various reactivity indices. It also becomes clear that there is a smooth transition between the two classes of compounds. We furthermore demonstrate both from DFT-based reactivity indices and from energy decomposition analysis, combined with natural orbitals for chemical valence (EDA-NOCV), that the monocomplexed stannylones are still nucleophilic and as reactive towards a second Lewis acid as towards the first one. The dominating interaction is a strong σ-type interaction from the Sn atom towards the Lewis acid. The interaction energy is higher for complexes with the cation Ag(+) than with the non-charged electrophiles BH(3), BF(3), and AlCl(3).

Bonding in Heavier Group 14 Zero‐Valent Complexes—A Combined Maximum Probability Domain and Valence Bond Theory Approach

“…The calculated geometries are in good agreement with the previously published results: Frenking et al. reported L−E−L bond angles of 95.0, 92.8, 88.5 and 87.0, respectively, for 2Si – 2Pb (our values are 94.7, 92.2, 87.5 and 85.3, respectively); for compounds 1Sn , 2Sn , 4Sn and 5Sn , L−Sn lengths of 2.650, 2.249, 2.778 and 2.239, respectively, correspond very well with the values of 2.628, 2.240, 2.765 and 2.221, respectively, found by De Proft and co‐workers . Notably, a strong dissymmetry in C−E bond lengths was observed for heavier analogues of tetraaminoallene (TAA) 3E .…”

“…This is also in line with the theoretical results of De Proft et al. revealing that there is a smooth transition between stannylenes and stannylones . For the sake of clarity, the resonance structures in Figure are depicted with both the conventional Lewis model and the donor–acceptor formalism.…”

“…This feature was also reported for the TAA adduct of GaCl 3 in the experimental work by the group of Gandon, in contrast to the theoretical studies of De Proft et al. dealing with a similar heavier analogue of TAA with a slightly different substituents at the nitrogen atom (Me vs. H) for which no such bonding pattern was revealed …”

Reactivity of low-oxidation state tin compounds: an overview of the benefits of combining DFT Theory and experimental NMR spectroscopy

“…These compounds were shown to have bent geometries. [18][19][20]22,35 Figure 6 depicts the several possible Lewis structures for a prototypical stannylone with two carbene ligands CR 2 . Lewis structure (a) in Fig.…”

“…The final part of this review is devoted to a theoretical analysis of a series of stannylones, focusing on their reactivity properties that are compared with those of representative Sn(II) compounds. 35 Overall this overview should reinforce insights into the reactivity of dicoordinated tin compounds from both the theoretical and experimental point of view. Another example of this synergy between theoretical and experimental approaches towards the elucidation of structure, bonding, and reactivity is the recent contribution by Macdonald and coworkers, who investigated the stabilization of Sn(II) by a series of acyclic and crown ether ligands by structural, spectroscopic, and computational methods.…”