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The donor-free silanimines tBu2Si=N-SiRtBu2 (R = tBu, Ph), which are prepared from tBu2ClSiN3 and NaSiRtBu2 at −78 ◦C inBu2O, decompose in benzene at room temperature with the formation of isobutene. Products of ene reactions of isobutene and tBu2Si=N-SiRtBu2 (R = tBu, Ph) are formed. X-Ray quality crystals of H2C=C(CH2SitBu2-NH-SiPhtBu2)2 (monoclinic, space group C2/c, Z = 4) were grown from a benzene solution at ambient temperature, whereas single crystals of H2C=C(CH2SitBu2-NH-SitBu3)2 (monoclinic, space group P21, Z = 2) were obtained by recrystallization from THF.
The bis(trimethyl)silylamido complex Na(THF){Fe[N(SiMe3)2]3} and the disilane tBu3SiSitBu3 were obtained from the reaction of Fe[N(SiMe3)2]3 with the sodium silanide Na(THF)2[SitBu3] in a mixture of benzene and THF. Single crystals of Na(THF){Fe[N(SiMe3)2]3} suitable for X-ray diffraction were grown from the reaction solution at ambient temperature (orthorhombic, C2221, Z = 4). The solid-state structure features a contact-ion pair with two short N-Na contacts. The THF adducts {M(THF)2[N(SiMe3)2]2} reacted with 2,2´-bipyridine to give the corresponding complexes {M(2,2´bipy)[N(SiMe3)2]2} (M= Mn; Fe). Their structures (M= Fe: orthorhombic, Pca21, Z = 8; M = Mn: orthorhombic, Pbca, Z = 8) feature monomeric units. The cyclic voltammogram of Fe[N(SiMe3)2]3 revealed a reversible redox transition with the potential of -0;523 V (E½), which was assigned to the Fe(III)[N(SiMe3)2]3 → Fe(II)[N(SiMe3)2]-3 redox transition, whereas the compounds {Fe(THF)2[N(SiMe3)2]2} (Eox = -0;379 V) and {Fe(2,2´bipy)[N(SiMe3)2]2} (Eox = -0;436 V) featured irreversible oxidation waves. The related manganese bis(trimethylsilyl)amido complexes {Mn(THF)2[N(SiMe3)2]2} (Eox = -0;458 V) and {Mn(2,2´bipy)[N(SiMe3)2]2} (Eox = -0513 V) also underwent irreversibile electron transfer processes.
The thermolabile triazenides M[tBu3SiNNNSiMetBu2] (M = Li, Na) are accessible from the reaction of tBu2MeSiN3 with the silanides MSitBu3 (M = Li, Na) at −78 °C in THF. At r. t. N2 elimination from the triazenides M[tBu3SiNNNSiMetBu2] (M = Li, Na) takes place with the formation of M[N(SiMetBu2)(SitBu3)] (M = Li, Na). X-Ray quality crystals of Li(THF)[N(SiMetBu2)(SitBu3)] (orthorhombic, Pna21) are obtained from a benzene solution at ambient temperature. In contrast to the structures of the unsolvated silanides MSitBu3 (M = Li, Na), the THF adduct Li(THF)3SitBu3 is monomeric in the solid state (orthorhombic, Pna21).
The intriguing (μ-hydrido)diboranes(4) with their prominent pristine representative [B2H5]− have mainly been studied theoretically. We now describe the behavior of the planarized tetraaryl (μ-hydrido)diborane(4) anion [1H]− in cycloaddition reactions with the homologous series of heterocumulenes CO2, iPrNCO, and iPrNCNiPr. We show that a C=O bond of CO2 selectively activates the B−B bond of [1H]−, while the μ-H ligand is left untouched ([2H]−). The carbodiimide iPrNCNiPr, in contrast, neglects the B−B bond and rather adds the B-bonded H− ion to its central C atom to generate a formamidinate bridge across the B2 pair ([3]−). As a hybrid, the isocyanate iPrNCO combines the reactivity patterns of both its congeners and gives two products: one of them ([4H]−) is related to [2H]−, the other ([5]−) is an analog of [3]−. We finally propose a mechanistic scenario that rationalizes the individual reaction outcomes and combines them to a coherent picture of B–B vs. B–H bond activation.