Dispersion Forces and Counterintuitive Steric Effects in Main Group Molecules: Heavier Group 14 (Si–Pb) Dichalcogenolate Carbene Analogues with Sub-90° Interligand Bond Angles

Abstract

The synthesis, spectroscopic and structural characterization of an extensive series of acyclic, monomeric tetrylene dichalcogenolates of formula M(ChAr)2 (M = Si, Ge, Sn, Pb; Ch = O, S, or Se; Ar = bulky m-terphenyl ligand) are described. They were found to possess several unusual features-the most notable of which is their strong tendency to display acute interligand, Ch-M-Ch, bond angles that are often well below 90°.Furthermore, and contrary to normal steric expectations, the interligand angles were 2 found to become narrower as the size of the ligand was increased. Experimental and structural data in conjunction with high-level DFT calculations, including corrections for dispersion effects, led to the conclusion that dispersion forces play a key role in stabilizing their acute interligand angles.

Reactions of GeCl2 with the Thiolate LiSC(SiMe3)3: From thf Activation to Insertion of GeCl2 Molecules into C−S Bonds

“…[7,11] The GeÀ Sb ond lengths in 1 are nearly the same with valueso fa bout 222.7 pm and are therefore shorter with respect to the GeÀS bonds found in solid GeS (244 pm), [12] but they are comparable to GeÀSb ond lengths in the thiolated germylenes Ge(SAr Me6 ) 2 with bond lengthst hat range from 224 to 229 pm as well as the GeÀSb ond lengths in solid GeS 2 (221.2 pm). [7,13] Slightly shorter are the GeÀSb ond lengths in Jutzi and co-workers' bis(thiolatogermylene) chromium complex [Cr(CO) 5 Ge(SC 6 H 2 -2,4,6-Me 3 ) 2 ]w ith an average of 218.7 pm. [14] Since compound 1 has C 2v point-group symmetry,t he shape of the molecular orbitals of the s-bonding frame at the germanium atom obtainedb yq uantum chemical calculations is quite similar to simple well-known molecular-orbital (MO) diagrams of molecules like H 2 O.…”

“…The special feature of 3 is the surrounding of the second germanium atom, in whichathf molecule is boundt hrough ac arbon atom and not through the oxygen atom as as imple donorg roup. This orientation could be clarified by ad istinct identification of the hydrogen-atom positions (7), Ge1ÀS2 242.00 (7), S1ÀC1 188.4(3), Li1ÀS1 250.8(5), Li1ÀS2 252.0(5),L i1ÀO1 190.6(5);S1-Ge1-S2 86.10(2), S2-Ge1-S3 87.46(2), S3-Ge1-S1 88.30 (2), Ge1-S1-C1 123.06(9), S1-Li1-S28 1.86(1), Ge1-S1-Li17 7.4(1).…”

“…[6] Structurally characterized thiolated germylenes are rare in the literature.I n2 013, Power and co-workers presentedanumber of stable acyclic, monomeric tetrylene dichalcogenates of the formula M(ChAr) 2 (M = Si, Ge, Sn, Pb;C h = O, S, Se, Ar = bulky m-terphenyl ligand), whichd isplay acute interligand bond angles. [7] To synthesizeg ermylenes, the GeCl 2 ·dioxane complex is widely used as ap recursorf or substitution reactions. [8] In addition, GeCl 2 can undergo oxidative insertion reactions into different kinds of bonds.…”

Reactions of Alkenes and Alkynes with an Acyclic Silylene and Heavier Tetrylenes under Ambient Conditions

“…12 The cyclization results in shortened Si1−S1 distances (Si1−S1 2.1264 (6)) and longer C−S1 distances S1−C1 1.8014(19) for 1 and has little effect on the Si1−S1 distance in 2 (Si1−S1 2.1398(4)) in comparison to those in the precursor silylene (2.137 (1) and 1.775(2) Å for Si1-S1 and S1-C1 bonds, respectively).…”

“…Si(SAr Me 6 )2 11 and Si(SAr iPr 4 )2 12 to the alkenes ethylene and norbornadiene, we obtained the silirane compounds (Ar iPr 4 S)2Si(CH2)2 and (Ar Me 6 S)2Si(C7H8). The first species features unique reversible binding to ethylene in toluene solutions with a Gibbs free energy of association (ΔGassn) of −24.9 ± 2.5 kJ mol −1 , 13 a value low enough to be greatly affected by entropic effects.…”