Stepwise Synthesis of Siloxane‐Substituted Oligoarsanes and Structural Investigation of Alkaline Earth Metal Derivatives

Molecular Main Group Metal Hydrides

This review serves to document advances in the synthesis, versatile bonding, and reactivity of molecular main group metal hydrides within Groups 1, 2, and 12-16. Particular attention will be given to the emerging use of said hydrides in the rapidly expanding field of Main Group element-mediated catalysis. While this review is comprehensive in nature, focus will be given to research appearing in the open literature since 2001.

Aryl-substituted triarsiranes: synthesis and reactivity

Cyclotriarsanes are rare and described herein is a scalable synthetic protocol towards (AsAr)3, which allowed to study their reactivity towards [Cp2Ti(C2(SiMe3)2)], affording titanocene diarsene complexes, and towards N-heterocyclic carbenes (NHCs) to give straightforward access to a variety of NHC-arsinidene adducts.

Covalency and Ionicity Do Not Oppose Each Other-Relationship Between Si-O Bond Character and Basicity of Siloxanes

Covalency and ionicity are orthogonal rather than antipodal concepts. We demonstrate for the case of siloxane systems [R₃ Si-(O-SiR₂ )_n -O-SiR₃ ] that both covalency and ionicity of the Si-O bonds impact on the basicity of the Si-O-Si linkage. The relationship between the siloxane basicity and the Si-O bond character has been under debate since previous studies have presented conflicting explanations. It has been shown with natural bond orbital methods that increased hyperconjugative interactions of LP(O)→σ*(Si-R) type, that is, increased orbital overlap and hence covalency, are responsible for the low siloxane basicity at large Si-O-Si angles. On the other hand, increased ionicity towards larger Si-O-Si angles has been revealed with real-space bonding indicators. To resolve this ostensible contradiction, we perform a complementary bonding analysis, which combines orbital-space, real-space, and bond-index considerations. We analyze the isolated disiloxane molecule H₃ SiOSiH₃ with varying Si-O-Si angles, and n-membered cyclic siloxane systems Si₂ H₄ O(CH₂ )_n-3 . All methods from quite different realms show that both covalent and ionic interactions increase simultaneously towards larger Si-O-Si angles. In addition, we present highly accurate absolute hydrogen-bond interaction energies of the investigated siloxane molecules with water and silanol as donors. It is found that intermolecular hydrogen bonding is significant at small Si-O-Si angles and weakens as the Si-O-Si angle increases until no stable hydrogen-bond complexes are obtained beyond φ_SiOSi =168°, angles typically displayed by minerals or polymers. The maximum hydrogen-bond interaction energy, which is obtained at an angle of 105°, is 11.05 kJ mol^-1 for the siloxane-water complex and 18.40 kJ mol^-1 for the siloxane-silanol complex.

Synthesis of a Gallaarsene {HC[C(Me)N-2,6- i-Pr2-C6H3]2}GaAsCp* Containing a Ga═As Double Bond

Cp*AsCl₂ (Cp* = C₅Me₅) reacts with one equivalent of LGa (L = HC[C(Me)N(2,6- i-Pr₂C₆H₃)]₂) with formation of L(Cl)GaAs(Cl)Cp* 1, whereas the reaction with two equivalents of LGa yielded gallaarsene LGaAsCp* 2 containing a Ga═As double bond and (η¹-Ga(Cp*)L(η²-GaL)(μ-As₃) 3. Compounds 2 and 3 were structurally characterized by single crystal X-ray diffraction, and the π-bonding contribution in 2 was analyzed by temperature-dependent ¹H NMR spectroscopy (9.65 kcal mol^-1) and by quantum mechanical computation.