Hui-Xian Yeong

Nanyang Technological University, Singapore, Singapore

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Publications (8)44.74 Total impact

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    ABSTRACT: The syntheses of a zwitterionic base-stabilized digermadistannacyclobutadiene and tetragermacyclobutadiene supported by amidinates and low-valent germanium amidinate substituents are described. The reaction of the amidinate Ge(I) dimer, [LGe:]2 (1, L=PhC(NtBu)2 ), with two equivalents of the amidinate tin(II) chloride, [LSnCl] (2), and KC8 in tetrahydrofuran (THF) at room temperature afforded a mixture of the zwitterionic base-stabilized digermadistannacyclobutadiene, [L2 Ge2 Sn2 L'2 ] (3; L'=LGe:), and the bis(amidinate) tin(II) compound, [L2 Sn:] (4). Compound 3 can also be prepared by the reaction of 1 with [L(Ar) SnCl] (5, L(Ar) =tBuC(NAr)2 , Ar=2,6-iPr2 C6 H3 ) in THF at room temperature. Moreover, the reaction of 1 with the "onio-substituent transfer" reagent [4-NMe2 -C5 H4 NSiMe3 ]OTf (8) in THF and 4-(N,N-dimethylamino)pyridine (DMAP) at room temperature afforded a mixture of the zwitterionic base-stabilized tetragermacyclobutadiene, [L4 Ge6 ] (9), the amidinium triflate, [PhC(NHtBu)2 ]OTf (10), and Me3 SiSiMe3 (11). X-ray structural data and theoretical studies show conclusively that compounds 3 and 9 have a planar and rhombic charge-separated structure. They are also nonaromatic.
    Chemistry - A European Journal 09/2013; · 5.93 Impact Factor
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    ABSTRACT: The synthesis and reactivity of a silyliumylidene cation stabilized by an amidinate ligand and 4-dimethylaminopyridine (DMAP) are described. The reaction of the amidinate silicon(I) dimer [LSi:]2 (1; L=PhC(NtBu)2 ) with one equivalent of N-trimethylsilyl-4-dimethylaminopyridinium triflate [4-NMe2 C5 H4 NSiMe3 ]OTf and two equivalents of DMAP in THF afforded [LSi(DMAP)]OTf (2). The ambiphilic character of 2 is demonstrated from its reactivity. Treatment of 2 with 1 in THF afforded the disilylenylsilylium triflate [L'2 (L)Si]OTf (3; L'=LSi:) with the displacement of DMAP. The reaction of 2 with [K{HB(iBu)3 }] and elemental sulfur in THF afforded the silylsilylene [LSiSi(H){(NtBu)2 C(H)Ph}] (4) and the base-stabilized silanethionium triflate [LSi(S)DMAP]OTf (5), respectively. Compounds 2, 3, and 5 have been characterized by X-ray crystallography.
    Chemistry - A European Journal 07/2013; · 5.93 Impact Factor
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    ABSTRACT: The synthesis and characterization of new amidinate-stabilized germatrisilacyclobutadiene ylides [L(3)Si(3)GeL'] (L=PhC(NtBu)(2); L'=ËL; Ë=Ge (3), Si (7)) are described. Compound 3 was prepared by the reaction of [LSi-SiL] (1) with one equivalent of [LGe-GeL] (2) in THF. Compound 7 was synthesized by the reaction of 2 with excess 1 in THF. The bisamidinate germylene [L(2)Ge:] (4) is a by-product in both reactions. Moreover, compound 7 was prepared by the reaction of 3 with one equivalent of 1 in THF. Compounds 3 and 7 have been characterized by NMR spectroscopy, X-ray crystallography, and theoretical studies. The results show that compounds 3 and 7 are not antiaromatic. The puckered Si(3) Ge four-membered rings in 3 and 7 have a ylide structure, which is stabilized by amidinate ligands and the electron delocalization within the Si(3) Ge four-membered ring.
    Chemistry - A European Journal 02/2012; 18(9):2685-91. · 5.93 Impact Factor
  • Siew-Peng Chia, Hui-Xian Yeong, Cheuk-Wai So
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    ABSTRACT: The synthesis and characterization of the digermylenes [LGe-GeL] [L = L(1) (3A), L(2) (3B)] supported by the 2,6-diiminophenyl (L(1)) and 2-imino-5,6-methylenedioxylphenyl (L(2)) ligands are described. Their reactivities toward potassium graphite are also reported. The reaction of [LGeCl] [L = L(1) (2A), L(2) (2B)] with KC(8) in tetrahydrofuran (THF) at room temperature afforded the digermylenes [LGe-GeL] [L = L(1) (3A), L(2) (3B)], which are the first examples of diaryldigermylenes stabilized by o-imino donor(s). The treatment of 3A with 2 equiv of KC(8) in Et(2)O, followed by the addition of excess tetramethylethylenediamine (TMEDA), results in cleavage of the Ge(I)-Ge(I) bond to afford the germylidenide anion [L(1)GeK·TMEDA] (4A). Similarly, the reaction of 3B with excess KC(8) in THF afforded the germylidenide anion [L(2)GeK] (4B). The molecular structures of compounds 4A and 4B as determined by single-crystal X-ray diffraction analysis show that the K atoms are η(1)-coordinated with the low-valent Ge atoms. Moreover, the negative charges at the Ge atoms in compounds 4A and 4B are stabilized by electron delocalization in the germanium heterocycles.
    Inorganic Chemistry 12/2011; 51(2):1002-10. · 4.59 Impact Factor
  • Shu-Hua Zhang, Hui-Xian Yeong, Cheuk-Wai So
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    ABSTRACT: The reactivity of the silylsilylene [{PhC(NtBu)(2)}SiSi(Cl){(NtBu)(2)C(H)Ph}] (2) towards diphenylacetylene, azobenzene, 2,6-diisopropylphenyl azide, sulfur, and selenium is described. The reaction of 2 with one equivalent of azobenzene in toluene afforded compound 3, which is the first example of a 1,2-diaza-3,4-disilacyclobutane containing a pentacoordinate silicon center. The formation of 3 can be explained by a [1+2] cycloaddition of the divalent Si center in 2 with PhN=NPh to form a diazasilacyclopropane intermediate, which then undergoes a 1,2-chlorine shift to release the ring strain to form 3. Similarly, the reaction of 2 with one equivalent of diphenylacetylene in toluene afforded the 1,2-disilacyclobutene 4, which contains a pentacoordinate silicon center. The reaction of 2 with 1.6 equivalents of 2,6-diisopropylphenylazide in toluene afforded the silaimine [LSi(=NAr)N(Ar)L'] (5, L=PhC(NtBu)(2) , L'=Si(Cl){(NtBu)(2)C(H)Ph}, Ar=2,6-iPr(2)C(6)H(3)). The formation of 5 can be explained by an oxidative addition of the divalent Si center in 2 with ArN(3) to afford a silaimine intermediate, which then reacts with another molecule of ArN(3) to give compound 5. The reaction of 2 with elemental sulfur in toluene afforded the chlorosilanethione [LSi(S)Cl] (6) and dithiodisiletane [{Ph(H)C(NtBu)(2) }Si(μ-S)](2) (7). Treatment of 2 with elemental selenium in THF afforded the di(silaneselone) [LSi(Se)Si(Se)L] (8). Evidently, the divalent Si center in 2 undergoes oxidative addition with chalcogens to afford a silylsilanechalcogenone intermediate, which then displaces ":Si{(NtBu)(2)C(H)Ph}" and "ClSi{(NtBu)(2) C(H)Ph}" to form 6 and 8, respectively. Moreover, compound 8 was synthesized by the reaction of [{PhC(NtBu)(2)}Si:](2) (10) with elemental selenium in THF. The results show that the reactions of 2 are initiated by oxidative addition of the divalent silicon center, and then the intermediate formed undergoes a rearrangement involving the diaminochlorosilyl substituent to form compounds 3-8. These products have been characterized by NMR spectroscopy and X-ray crystallography.
    Chemistry - A European Journal 02/2011; 17(12):3490-9. · 5.93 Impact Factor
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    ABSTRACT: 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.
    Chemistry - A European Journal 09/2010; 16(33):10250-4. · 5.93 Impact Factor
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    ABSTRACT: The synthesis and characterization of novel cis-1,2-disilylenylethene [cis-LSi{C(Ph)=C(H)}SiL] (2; L=PhC(NtBu)(2)) and a singlet delocalized biradicaloid [LSi(μ(2)-C(2)Ph(2))(2)SiL] (3) are described. Compound 2 was prepared by the reaction of [{PhC(NtBu)(2)}Si:](2) (1) with one equivalent of PhC[triple chemical bond]CH in toluene. Compound 3 was synthesized by the reaction of 1 with two equivalents of PhC[triple chemical bond]CPh in toluene. The results suggest that the reaction proceeds through an [LSi{C(Ph)==C(Ph)}SiL] intermediate, which then reacts with another molecule of PhC[triple chemical bond]CPh to form 3. Compounds 2 and 3 have been characterized by X-ray crystallography and NMR spectroscopy. X-ray crystallography and DFT calculations of 3 show that the singlet biradicals are stabilized by the amidinate ligand and the delocalization within the "Si(μ(2)-C(2)Ph(2))(2)Si" six-membered ring.
    Chemistry - A European Journal 09/2010; 16(43):12956-61. · 5.93 Impact Factor
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    ABSTRACT: 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.
    Inorganic Chemistry 12/2009; 49(2):371-3. · 4.59 Impact Factor

Publication Stats

10 Citations
44.74 Total Impact Points

Institutions

  • 2009–2013
    • Nanyang Technological University
      • • Division of Chemistry and Biological Chemistry (CBC)
      • • School of Physical and Mathematical Sciences
      Singapore, Singapore