Hong-Wei Xi

Hydrosilylation of a Silicon(II) Hydride: Synthesis and Characterization of a Remarkable Silylsilylene

The synthesis and characterization of novel monomeric silylsilylenes [{PhC(NtBu)(2)}Si--Si{(NtBu)(2)C(H)Ph}R] (R=Cl (2), H (4)) are described. Compound 2 was prepared by the treatment of [{PhC(NtBu)(2)}SiHCl(2)] (1) with two equivalents of potassium graphite, whereas compound 4 was synthesized by the treatment of 1 with four equivalents of potassium graphite. The results suggest that silicon(II) hydride intermediate [{PhC(NtBu)(2)}SiH] was formed in the reduction, which underwent a hydrosilylation with the amidinate ligand of [{PhC(NtBu)(2)}SiR] (R=Cl or H) to form 2 and 4, respectively. The existence of [{PhC(NtBu)(2)}SiH] in solution was demonstrated by the treatment of [{PhC(NtBu)(2)}SiCl] (3) with [K{HB(iBu)(3)}]. Compounds 2 and 4 have been characterized by X-ray crystallography and NMR spectroscopy. The results show that compounds 2 and 4 are stable in solution or the solid state, and do not dimerize to form the corresponding disilene. DFT calculations show that the Si--Si bonds in 2 and 4 do not have multiple-bond character.

Reactivity of a Disilylene [{PhC(NBut)2}Si]2 toward Bromine: Synthesis and Characterization of a Stable Monomeric Bromosilylene

The reaction of the disilylene [{PhC(NBu(t))(2)}Si](2) (1) with 1 equiv of bromine in toluene afforded novel monomeric bromosilylene [{PhC(NBu(t))(2)}SiBr] (2). The result shows that the Si(I)-Si(I) bond in 1 was cleaved by bromine. An X-ray structure of compound 2 has been determined.

Group II Metal Complexes of the Germylidendiide Dianion Radical and Germylidenide Anion

The two-electron reduction of a Group 14-element(I) complex [RË⋅] (E=Ge, R=supporting ligand) to form a novel low-valent dianion radical with the composition [RË:]˙(2-) is reported. The reaction of [LGeCl] (1, L=2,6-(CH=NAr)2C6H3, Ar=2,6-iPr2C6H3) with excess calcium in THF at room temperature afforded the germylidenediide dianion radical complex [LGe]˙(2-)⋅Ca(THF)3(2+) (2). The reaction proceeds through the formation of the germanium(I) radical [LGe⋅], which then undergoes a two-electron reduction with calcium to form 2. EPR spectroscopy, X-ray crystallography, and theoretical studies show that the germanium center in 2 has two lone pairs of electrons and the radical is delocalized over the germanium-containing heterocycle. In contrast, the magnesium derivative of the germylidendiide dianion radical is unstable and undergoes dimerization with concurrent dearomatization to form the germylidenide anion complex [C6H3-2-{C(H)=NAr}Ge-Mg-6-{C(H)-NAr}]2 (3).

Delocalized Hypervalent Silyl Radical Supported by Amidinate and Imino Substituents

The reaction of the amidinato silylsilylene with a functionalized diaminochlorosilyl substituent, [LSiSi(Cl){(NtBu)2C(H)Ph}] (1; L = PhC(NtBu)2), with ArN═C═NAr (Ar = 2,6-iPr2C6H3) in toluene afforded the delocalized hypervalent silyl radical [LSi•(μ-CNAr)2Si{(NtBu)2C(H)Ph}] (2). It possesses a hypervalent silyl radical that delocalizes throughout the Si2C2 ring.

CCDC 850083: Experimental Crystal Structure Determination

Related Article: Shu-Hua Zhang, Hong-Wei Xi, Kok Hwa Lim, Qingyong Meng, Ming-Bao Huang, Cheuk-Wai So|2012|Chem.-Eur.J.|18|4258|doi:10.1002/chem.201103351