RESUMEN
The reactions of NHB-stabilized disilyne (NHB)Si≡Si(NHB) (1, NHB = [ArN(CMe)2NAr]B, Ar = 2,6-iPr2C6H3) with internal alkynes were described. Reaction of disilyne 1 with one equivalent of bis(trimethylsilyl)acetylene led to a reversible [1 + 2] cycloaddition of one of the Si atoms with the alkyne and the insertion of the other Si into one of Ar rings with the formation of a silirenyl-silepin 2, whereas reaction of 1 with two equivalents of Me3SiCCSiMe3 resulted in the formal addition of the Csp-Si bond to the Si≡Si triple bond to give disilene (NHB)(Me3Si)Si=Si(CCSiMe3)(NHB). Reaction of 1 with 1,3-diyne Me3SiCCCCSiMe3 yielded a 1,2-disilacyclobut-3-ene via cycloaddition, ring expansion, and NHB 1,2-shift sequence. The initial [1 + 2] cycloaddition of one of the silicon atoms with an alkyne was strongly supported by DFT calculations. The results demonstrated the significant bis(silylene) character and rich synthetic potential of bis(boryl) disilyne 1.
RESUMEN
The synthesis, structures, and reactivity of the first neutral 2π-aromatic Si4 rings [LSiSiAr(X)]2 (3: X = Br; 4: X = Cl; L = PhC(NtBu)2, Ar = 2,4,6-Me3C6H2) were described. Compounds 3 and 4 were obtained by 1,3-halogenation of tetrasilacyclobutadiene (LSiSiAr)2 (2), which was prepared by the reductive cross-coupling of trisilane (ArSiCl2)2SiHAr with two equiv of chlorosilylene LSiCl. The reaction of 3 with two equiv of PhLi yielded the corresponding substitution Si4 ring [LSiSiAr(Ph)]2 (5). Single-crystal X-ray diffraction analysis of 3 disclosed that it adopts both puckered (3a) and planar (3b) structures in the solid state, whereas 4 and 5 exhibit only a puckered structure. DFT calculations suggested that the puckered 3a features almost the same electronic structure with fully delocalized 2π planar 3b. The dominant 2π-aromaticity of 3 in a σ-frame has been demonstrated by DFT calculations, providing the first example of aromatics featuring both planar and puckered structures.
RESUMEN
Reaction of solid NHB-stabilized disilyne (NHB)Si≡Si(NHB) (1, NHB = [ArN(CMe)2NAr]B, Ar = 2,6-iPr2C6H3) with 1 atm of carbon monoxide yielded the first 1,2-disilicon dicarbonyl complex (NHB)(OC)SiSi(CO)(NHB) (2). Hydrolysis and methanolysis of 2 led to the C-C coupling and protonation of two CO oxygen atoms giving disilacyclobutene derivatives 3 and 4. In contrast, reaction of 2 with iodomethane resulted in the oxidative addition to the silicon atoms with the formation of 1,2-diiodo-disilane 5 with the liberation of CO molecules. Single-crystal X-ray diffraction analysis of 2 disclosed the coordination of CO to the two silicon atoms with a unique 1,2-dicarbonyl-disilane skeleton, in which the pronounced backbonding from the lone pairs of silicon p orbitals to CO π* orbitals was elucidated by DFT calculations.
RESUMEN
Reaction of the silaamidinate nickel bromide LSi(NAr)2NiBr2Li(thf)(OEt2) (L = PhC(NtBu)2, Ar = 2,6-iPr2C6H3, 1) with NaHBEt3 led to intramolecular C-H activation with the formation of the µ-1,2-dinitrogen dinickel pincer complex [LSi(NAr)(NAr)Ni]2(µ-1,2-N2) (Ar = 2-C(CH3)2-6-iPrC6H3, 2). Single-crystal X-ray diffraction analysis of 2 disclosed a square planar Ni(II) atom bridged by N2. Reaction of 2 with carbon monoxide and 2,6-dimethylphenyl isocyanide yielded square planar carbonyl and isocyanide complexes 3 and 4 with release of N2. These results provide new approaches for the coordination of N2 with nickel(II) species.
RESUMEN
The synthesis of low-valent silicon compounds that enable the activation of small molecules has been of great current interest. Reduction of N-heterocyclic boryltribromosilane (NHB)SiBr3 (2, NHB=[ArN(CMe)2 NAr]B, Ar=2,6-iPr2 C6 H3 ) with three equiv. of lithium in diethyl ether yielded the NHB-stabilized disilyne (NHB)Si≡Si(NHB) (3). Disilyne 3 slowly reacted with toluene, leading to the activation of one benzylic C-H bond and one C=C double bond with the formation of 4. Treatment of 3 with dihydrogen under 1â atm at room temperature resulted in the exclusive formation of the first boryl-stabilized 1,2-dihydrodisilene. Compounds 3-5 have been characterized by single-crystal X-ray diffraction studies, which indicated the co-planarity of the B-Si-Si-B plane with the NHB rings in compounds 3 and 5. DFT calculations indicated the significant π electron delocalization of the Si-Si multiple bonds to the B-N bonds in NHB rings.
RESUMEN
A Pd(ii) chloride complex supported by a Yamashita-Nozaki PBP pincer ligand, [C6H4-1,2-(NCH2PtBu2)2B]PdCl (1a), was synthesized. The structure, properties and catalytic activity of complex 1a were compared with those of the corresponding POCOP pincer complex [C6H3-2,6-(OPtBu2)2]PdCl (2a). It was found that the Pd centre in complex 1a is more electron rich and easier to be oxidized than that in complex 2a; complex 1a is a much better catalyst for Suzuki-Miyaura cross-coupling reactions than complex 2a. Starting from complexes 1a and 2a, two series of Pd(ii) pincer complexes bearing a SH, BH4, N[combining low line]CS, N[combining low line]CSe or N3 covalent ligand, [C6H4-1,2-(NCH2PtBu2)2B]PdY (Y = SH, 1b; BH4; 1c; N[combining low line]CS, 1d; N[combining low line]CSe, 1e; and N3, 1f) and [C6H3-2,6-(OPtBu2)2]PdY (Y = SH, 2b; BH4, 2c; N[combining low line]CS, 2d; N[combining low line]CSe, 2e; and N3, 2f), were synthesized and fully characterized. Single crystal X-ray diffraction analysis indicated that the Pd centre is less tightly chelated in PBP pincer complexes. The strong σ-donor ability of the PBP pincer ligand has little influence on the structure of the covalent ligand possessing both σ-donor and π-acceptor properties. However, the stretching vibrational frequencies of N[combining low line]CS, N[combining low line]CSe and N3 ligands and the coordination mode of the BH4 ligand are significantly different in these two types of palladium pincer complexes.
RESUMEN
Organometallic chemists usually like to use the word robust to describe pincer ligand frameworks in metal pincer complexes. Although most transition metal pincer complexes are thermally stable, the pincer backbone frameworks can still decompose under certain circumstances. In order to explore the stability of the bis(phosphinite) (POCOP) pincer backbone in transition metal pincer complexes, group 10 metal POCOP pincer complexes were exposed to different nucleophilic and electrophilic conditions, respectively. It was found that the POCOP pincer backbone is stable under intermolecular nucleophilic conditions but cannot survive intramolecular nucleophilic attack; the POCOP pincer backbone is also stable under weak electrophilic conditions but the backbone can be completely destroyed by strong Lewis acids such as AlCl3. Possible decomposition/reconstruction pathways of the POCOP pincer ligand framework were proposed.
RESUMEN
Functional self-assemblies derived from noncovalent interactions such as lipid vesicles and DNA chiral double helices are a typical feature of natural life activity. Because of this phenomenon, a self-assembly approach for various functional organic particles is a desirable objective in supramolecular chemistry. Here, we report the discovery of enantiomeric conformers from a twisted macrocyclic host (MH), which was obtained from an achiral precursor by Schiff base reaction. Further studies suggest that a series of unexpected and stable core-shell-based organic micro/nanospheres can be directly precipitated from a simple reaction solution with high yield. A single-crystal X-ray diffraction analysis of MH revealed that the unusual C-H···π interaction triggered self-assembly of the enantiomeric forms in the solid state plays an important role in the formation of the core-shell-shaped organic particles.