Four-coordinate disilyl cobalt(Ⅱ)complexes with NHC ligation:Synthesis,characterization,and reactivity

Silyl cobalt species are putative intermediates in cobalt-catalyzed transformations of hydrosilanes.However,their reactivity has remained poorly understood.Reported here is the investigation on four-coordinate disilyl Co(Ⅱ)complexes with N-hetereocyclic carbene ligation.The reactions of[(ICy)_(2)Co(vtms)](ICy=1,3-dicyclohexylimidazol-2-ylidene,vtms=vinyltrimethylsilane)with primary and secondary hydrosilanes(3 equiv.)furnish the four-coordinate disilyl complexes[trans-(ICy)_(2)Co(SiHRR')_(2)](SiHRR'=SiH_(2)Mes,1;SiH_(2)Ph,2;SiH_(2)Cy,3;SiHPh_(2),4;SiHEt_(2),5)in moderate to good yields.The structures of 1,2 and 4 were established by single-crystal X-ray diffraction.Solution magnetic susceptibility measurement and EPR spectroscopy indicate their low-spin nature(S=1/2).Reactivity studies on 4 led to the establishment of the conversions of 4 to the disilyl dihydride Co(Ⅲ)complex[K(THF)][(ICy)_(2)Co(H)_(2)(SiHPh_(2))_(2)]_n(6)and the fluorosilyl Co(Ⅱ)complex[(ICy)_(2)Co(THF)(SiFPh_(2))][BF_(4)](7)when 4 was treated with excess amount of K and AgBF_(4),respectively,in THF.These conversions hint at the high activity of low-valent and high-valent disilyl cobalt species[trans-(ICy)_(2)Co(SiHPh_(2))_(2)]^(1-)and[trans-(ICy)_(2)Co(SiHPh_(2))_(2)]^(2+).Complex 4 is reactive toward terminal alkynes,but inert toward alkenes and internal alkynes.The reactions of 4 with terminal alkynes CyC≡CH and Me_(3)SiC≡CH(3 equiv.)yield the Co(Ⅱ)complexes[(ICy)_(2)Co(C≡CCy)_(2)](8)and[(ICy)_(2)Co(C≡CSiMe_(3))((SiMe_(3))C=CH_(2))](9),respectively,along with H_(2)SiPh_(2)and alkynylsilanes RC≡CSiHPh_(2)(R=Cy,SiMe_(3)),whereas the reaction with 4-CF_(3)C_(6)H_(4)C≡CH(3 equiv.)produce[(ICy)_(2)Co(C≡CAr)((Ar)C=CH(SiHPh_(2))C=CHAr)](Ar=4-CF_(3)C_(6)H_(4))(10)and H_(2)SiPh_(2).These reactions are proposed to involveσ-bond metathesis reactions between alkyne C(sp)-H bonds and Co-Si bonds in 4.Complexes 6–10 have been characterized by NMR spectroscopy,X-ray diffraction study,and elemental analysis.

Theoretical investigation of photoelectric properties of the four-coordinate organoboron compounds based on diketopyrrolopyrrole derivativ

In order to obtain high efficiency of organic light-emitting diodes and organic solar cells,a series of DPP-based four-coordinate organoboron compounds have been designed for photoelectric functional materials.The effects of electron-donating and-withdrawing substituent on the electronic and optical properties have been investigated by using density functional theory(DFT)and time-dependent DFT(TD-DFT)approaches systematically.It turned out that electron-donating and-withdrawing groups can tune effectively the frontier molecular orbital(FMO)energy level,energy gap,and absorption and fluorescence spectra.The introduction of electron-withdrawing groups for the parent molecule HBDPP(2,5-bis(diphenylboryl)-3,6-bis(pyridin-2-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione)favors the decrease for the FMO energy(E_(LUMO)and E_(HOMO)),HOMO-LUMO gaps(E_(g)),and the downhill energetic driving force(ΔEL-L),while the electron-donating groups can increase E_(LUMO),E_(HOMO),E_(g),andΔEL-L compared with that of HBDPP,respectively.The absorption and fluorescence spectra of the electron-withdrawing substituted derivatives exhibit bathochromic shifts,while the absorption and fluorescence spectra of the electrondonating substituted derivatives show hypsochromic shifts compared with the parent molecule HBDPP,respectively.Furthermore,the stronger the electron-withdrawing/donating ability of group is,the more significant the effect in the optoelectronic properties.

Synthesis and DFT Calculation of a Four- coordinated Manganese Compound Mn_2(BPTC)

A new four-coordinated manganese compound Mn2（BPTC） （BPTC =- biphenyl- 2,4,4＇,6-tetracarboxylate） with flu topology net was synthesized under hydrothermal conditions. Single-crystal X-ray diffraction analysis confirms its crystal belongs to the monoclinic system, space group C2/c with a = 12.2092（11）, b = 14.6932（9）, c = 8.9998（10） A, t= 108.256（12）°, Z= 4, V= 1533.2（2） A3, Dc = 1.889 mg/m3,μ = 1.69, F（O00） = 864, the final R = 0.063 and wR = 0.201 for 1407 observed reflections （I 〉 20（/））. UV-Vis absorption spectrum shows the title compound has a strong absorption at 326 and 238 nm and the optical diffuse reflectance determination shows the band gap of the title compound is 3.15 eV. The theory calculation elucidated that the UV absorptions of the title compound mainly arise from the electron transition from bonding orbitals of BPTC4- ligand to the empty orbitals of BPTC4- and Mn（II） ions.

Synthesis,Structure and Properties of a New Silver Nitrate Complex

A new metal-organic coordination polymer, [Ag（L）（NO3）]H （1, L = β-amino-β- （pyrid-2-yl）acrylonitrile）, has been synthesized by solvent method at ambient temperature and characterized through single-crystal diffraction, Fourier transformed infrared spectrum （FTIR）, elemental analysis, thermogravimetry analysis （TGA） and fluorescent measurements. 1 crystallizes in the triclinic system, space group Pi with a = 7.3600（3）, b = 8.5095（17）, c = 9.2936（14） A, α= 66.65（6）, β = 70.56（7）, γ= 71.59（6）°, V = 492.4（4） A3, μ = 2.043 mm-1, Dc = 2.104 Mg/m3, Z = 2, Mr = 312.01, F（000） = 302, the final R = 0.0347 and wR = 0.0987 for 3924 observed reflections with I 〉 2σ（I）.

A 3-D Selected Solvent Large Aperture MOF

The metal-organic framework（MOF）{[Cu（L1）_（0.5）（CN）]·4H_2O·3DMSO}_n（1） was assembled by 1,4-bis（3？,5？-dicyano-2？,6？-di（pyrid-4-yl）-1？,4？-dihydropyridyl）benzene（L1） together with copper cyanide at room temperature. In 1,the Cu~＋ ions are linked by CN-anions into a 1D helical chain,which is further fused together by tetradentate L1 ligands to build an extended 3D porous framework with two different types of functionalized channels. 1 crystallizes in the monoclinic,space group P21/c with a = 17.8729（6）,b = 8.7298（3）,c = 22.7524（9） ？,β = 96.072（4）o,V = 3530.1（2） ？~3,μ = 0.845 mm-1,Dc = 1.352 Mg/m^3,Z = 4,Mr = 718.35,F（000） = 1500,S = 1.081,the final R = 0.0877 and wR = 0.2275 for 6975 observed reflections with I 〉 2σ（I）.