六聚多酸還存在三元混配體系,比如:pH=4.6,[WVI]=[MoVI]=[VV]=50mmoldm-3體系中存在多種[V2MonW4-nO19]4-物種,通過51VNMR檢測(cè)到12條譜線,說明溶液中有12種不等性V原子,由于2個(gè)V原子總是處于順式位置,下面從六聚結(jié)構(gòu)來分析這12條譜線.n[V2MonW4-nO19]4-1234Typeofvanadiumδ51V(ppm)0[V2W4O19]4-WWWW1-511.461[V2MoW3O19]4-WWWMoWMoWW12-506.80-504.30-513.662[V2Mo2W2O19]4-MoWWMoMoWMoWWMoMoW121-502.61-501.05-507.38-507.163[V2Mo3WO19]4-WMoMoMoMoWMoMo12-503.08-498.24-502.764[V2Mo4O19]4-MoMoMoMo1-497.74122.十聚多酸陰離子

(1)[W10O32]4-(十聚鎢酸)

5H2W6O19+H2O

3H4W10O32

制備：條件：pH1~4,有機(jī)溶劑(如HCN,CH3COCH3)

183WNMR(ppm)

WA(2)

-160.3WB(8)

-16.7

17ONMR(ppm)

OA(2)

-6.5OC1(2),OC2(8)

765.3OB1(8),OB2(8)420.4OB3(4)434.7(2)V10O286-51VNMR(ppm):-412(VB)-506(VA)-524(VC)17ONMR(ppm):1197(OC1,OC2)931(OB3)864(OB4)715(OB2)358(OB1)83(OA)3.Keggin結(jié)構(gòu)

（XM12O40X為雜原子,M一般是W或Mo）（1）α-Keggin結(jié)構(gòu)，結(jié)構(gòu)單元：M3O134個(gè)M3O13通過共角相連圍繞中心雜原子構(gòu)成四面體，其中每個(gè)金屬的兩個(gè)OB分別與分屬于兩個(gè)M3O13的M相連，構(gòu)成α-Keggin

結(jié)構(gòu)，所有的金屬原子都一樣，只有一種（12個(gè)M）M3O13:α-Keggin結(jié)構(gòu)圖：可以畫成更簡單的平面圖（雜原子，OD省略）:M,12個(gè)OOA4個(gè)OB12個(gè)OC12個(gè)OD12個(gè)OAOM3X4個(gè)4178OCOM23*4=12個(gè)OBOMM’6*4/2=12個(gè)ODODM3*4=12個(gè)928936

580,555583,550SiMo12O404-PMo12O403-17ONMR(ppm)(2)β-Keggin結(jié)構(gòu)如果將其中的一個(gè)M3O13旋轉(zhuǎn)600，就成為β-Keggin結(jié)構(gòu).（1）M（2）OOA3個(gè)；OC6個(gè)OA’1個(gè)；OC’3個(gè)OB3個(gè);OC’’3個(gè)OB’3個(gè);OD3個(gè)OB’’6個(gè);OD’6個(gè)

OD’’3個(gè)ME-1,2,3，3個(gè)MF-4~9，6個(gè)MG-10,11,12，3個(gè)(3)缺位結(jié)構(gòu)通過加入控制量的堿可得到缺位型多酸

α-Keggin單缺位：α-XM11O39

β-Keggin單缺位：

去掉一個(gè)MO-ME：β1-XM11O39-MF：β2-XM11O39-MG：β3-XM11O39缺位型多酸是一類重要配體,過渡金屬及某些主族元素均可填入空位,重新形成完整的Keggin結(jié)構(gòu),可以制備種類繁多的取代型多元多酸化合物,可以有效地調(diào)變多酸的酸性,氧化還原性以及表面性質(zhì),是一類重要的多功能催化劑.對(duì)于α-Keggin

結(jié)構(gòu)而言,由于12個(gè)金屬都是一樣的,所以單缺位只有一種類型,即α-XM11,如去掉圖中的M1,金屬的種類將有:4,9;10,12;5,8;6,72,311共計(jì)6種對(duì)于β-結(jié)構(gòu),由于有3種金屬,可以形成3種單缺位結(jié)構(gòu):(1)去掉M1(或M2或M3),得β1-XM11,金屬得種類將有:4,9;5,8;6,7;2,3;10,11;12共計(jì)6種(2)去掉M10(或M11或M12),得β2-XM11,金屬的種類有:5,6;11,12;4,7;8,9;1,3;2共計(jì)6種(3)去掉M4(或M5,M6,M7,M8,M9),得β3-XM11,剩下的11個(gè)金屬自成一類,共計(jì)11種.α-Keggin去掉M3O6-去掉共角如-(8,9,12)-去掉共邊如-(10,11,12)β-Keggin去掉M3O6-去掉共角如-(1,2,3)-去掉共邊如-(1,4,9)β-A-XM9β-B-XM9

α-A-XM9α-B-XM9(1)去掉共角的M3O6,如(8,9,12),得α-A-XM9,金屬的種類有:1,4,10,11,7,3;2,5,6共計(jì)2種-M3O6(2)去掉共邊的M3O6,如(10,11,12),得α-B-XM9,金屬的種類有:4,5,6,7,8,9;1,2,3共計(jì)2種-M3O6(3)去掉共角的M3O6,如(1,2,3),得β-A-XM9,金屬的種類有:4,5,6,7,8,9;10,11,12共計(jì)2種(4)去掉共邊的M3O6,如(1,9,4),得β-B-XM9,金屬的種類有:12;10,11;5,8;6,7;2,3共計(jì)5種(4)多種Keggin結(jié)構(gòu)

如果將α-Keggin結(jié)構(gòu)中的一個(gè)M3O13旋轉(zhuǎn)600，就成為β-Keggin結(jié)構(gòu);如果將α-Keggin結(jié)構(gòu)中的兩個(gè)M3O13旋轉(zhuǎn)600，就成為γ-Keggin結(jié)構(gòu);如果將α-Keggin結(jié)構(gòu)中的三個(gè)M3O13旋轉(zhuǎn)600，就成為δ-Keggin結(jié)構(gòu);如果將α-Keggin結(jié)構(gòu)中的四個(gè)M3O13旋轉(zhuǎn)600，就成為ε-Keggin結(jié)構(gòu).從α-型到ε-型,M3單元之間的排斥增加,穩(wěn)定性逐步下降,以α-和β-為常見結(jié)構(gòu).Howmanytypesofunequalmetalatomsinα-,β-,γ-,δ-,ε-Keggin

polyoxometalates[XM12O40]n-?Answer:α-Keggin,onetype;β-Keggin,threetypes;γ-Keggin,fourtypes;δ-Keggin,threetypes;ε-Keggin,onetype.(5)混配結(jié)構(gòu)在Keggin結(jié)構(gòu)中，金屬配原子可以是W或Mo,或W和Mo混合,也有可能被V,Nb,Ta,Ti部分取代,形成多種幾何異構(gòu)體,大多數(shù)混配多酸是混合物,但合成得到個(gè)別幾何異構(gòu)體也是可能的.以α-[PTi2W10O40]7-的鑒定為例:

它的31PNMR只有一個(gè)單峰:-11.43ppm,說明化合物的純度很高,只含有一種幾何異構(gòu)體;它的183WNMR則有5個(gè)相同強(qiáng)度的峰,說明結(jié)構(gòu)中有五種不等性鎢核,各有2個(gè).(1)12,10(or11)-Ti:1;9,4;11;5,8;7,6;2,3.六種W;(2)12,8(or9)-Ti:7,11;3,10;9;1,4;6;5,2.六種W;(3)12,5(or6)-Ti:

每個(gè)金屬自成一種,十種W;(4)12,1(or3)-Ti:每個(gè)金屬自成一種,十種W;(5)12,2-Ti:10,11,5,6;4,7;8,9,1,3.三種W;(6)12,7(or4)-Ti:8,11;10,3;6,9;1,5;2,4.五種W3,12與12,5相同;1,12與12,6相同.3,12與1,12是對(duì)映異構(gòu)體，即（3）和（4）是對(duì)映異構(gòu)體；理論上有五種幾何異構(gòu)體，

α-[PTi2W10O40]7-為(6).4.Anderson結(jié)構(gòu)，XMo6O24n-6個(gè)MoO6共邊相連圍繞中心雜原子X,X的配位型式為反三角棱柱，每一個(gè)Mo有2個(gè)端氧。結(jié)構(gòu)中有3種氧原子：OB1,6個(gè)(OMoMoX);OB2,6個(gè)(OMoMo)OC,12個(gè)(OMo)雜原子X可以是I,Te,Al,Co,Mn,Ni等，也可以是Mo,這類多酸易發(fā)生質(zhì)子化，質(zhì)子化的位置總是在μ3-O(即OB1)上，17ONMR可以清楚地證明這一點(diǎn)，如：17ONMR化學(xué)位移(ppm)OCOB2OB1TeMo6O246-807383180IMo6O245-825387255H6AlMo6O243-833378--H6CoMo6O243-838382--5.仲鎢酸結(jié)構(gòu)，M7O246-(M=MoorW)酸化法

7MoO42-+8H+→[Mo7O24]6-+4H2O6MoO42-+Cr(H2O)63-+6H+→[Cr(OH)6Mo^O18]3-+6H2O12WO42-+HPO42-+23H+→[P2W12O40]3-+12H2O3.4.3多酸的合成方法2.以其他多陰離子為起始原料

OH-OH-α-[P2W18O62]6-→α2-[P2W17O61]10-→α-[P2W16O59]12-α-[P2W16O59]12-+VO2+→α-[P2W16V2O62]6-α-[P2W12O47+xH2x]2-+WO42-→α1-[P2W17O61]10-

加入試劑的順序：

SiO32-,WO42-,然后H+

-[SiW12O40]4-

WO42-,H+,然后SiO32--[SiW12O40]4-控制溫度或pH值：

WO42-,U4+,pH5~6,80oC[UW10O36]8-

冷卻煮沸

WO42-,

SiO32-,H+

-[SiW9O34]10-

-[SiW9O34]10-

試劑用量：WO42-,H3PO4(過量),H+

[P2W18O62]6-

3.非水溶液合成

WO(OEt)4,NR4OH,H2O→(NR4)2[W6O19]

VO(OBut)4,Bu4nNOH,EtOH→(Bu4N)3H3[V10O28]Na2MoO4.2H2O(DMF),HCl,MeOH→[W6O19]2-一級(jí)結(jié)構(gòu)和二級(jí)結(jié)構(gòu)多酸陰離子結(jié)構(gòu)稱為一級(jí)結(jié)構(gòu)，一級(jí)結(jié)構(gòu)一般較為穩(wěn)定；由多酸陰離子、陽離子和結(jié)晶水或有機(jī)分子排列的三維結(jié)構(gòu)稱為二級(jí)結(jié)構(gòu)，二級(jí)結(jié)構(gòu)易發(fā)生變化，經(jīng)常是某些催化反應(yīng)的“反應(yīng)場(chǎng)”。3.4.4多酸的通性

酸性溶液中比一般的無機(jī)酸酸性要強(qiáng)，在丙酮中所測(cè)的酸強(qiáng)度順序?yàn)椋篜W12>PW11V>PMo12SiW12>PMo11VSiMo12>>HCl,HNO3

固體多酸為Br?nsted酸，Hammett酸度H0<-8.2.H3PW12O40脫水后，H0達(dá)到-13.16,比SO42-/ZrO2、SO42-/TiO2弱，比SiO2-Al2O3、H3PO4/SiO2分子篩（HX、HY)強(qiáng)。3.軟度多酸陰離子屬于軟堿，堿性主要體現(xiàn)在多酸的橋氧原子上，能夠同有機(jī)反應(yīng)物或反應(yīng)物中間體進(jìn)行配位，使有機(jī)分子活化。4.氧化還原性通常多酸中的配原子以最高氧化態(tài)形式存在，具有氧化性。多酸可以經(jīng)歷多電子還原而不改變其結(jié)構(gòu)，還可以加氫或脫氧形成混合價(jià)化合物，催化過程通過電子傳遞或氫和氧的轉(zhuǎn)移來實(shí)現(xiàn)。5.多酸的催化活性具有確定的結(jié)構(gòu)，有利于在分子或原子水平上設(shè)計(jì)或合成催化劑。通常溶于極性溶劑，可用于均相和非均相催化反應(yīng)體系。同時(shí)具有酸性和氧化性，可作為酸和氧化的雙功能催化劑,多酸可與其他金屬取代形成取代型雜多酸化合物，通過有目的選擇組成元素來調(diào)節(jié)多酸的各種性質(zhì)獨(dú)特的反應(yīng)場(chǎng)雜多陰離子的軟性。屬于軟堿，作為金屬離子或有機(jī)金屬等的配體，具有獨(dú)特的配位能力，使反應(yīng)中間產(chǎn)物穩(wěn)定3.3TheNobleGases:Helium,Neon,Argon,Krypton,Xenon,andRadon3.3.1IntroductionOncetheseelementswerecalledasGroupZero,InertgasesandRaregases.Sincethelightermembersarebynomeansrareandtheheavieronesarenotentirelyinert,noblegasesseemsamoreappropriatenameandhascomeintogeneraluseduringthepastfivedecades.Intheearly1960s,NeilBartlettwasstudyingthepropertiesofplatinumhexafluoride,PtF6.ItisanextremelypowerfuloxidizingagentincomparisonwithF2.E0/VΔHelectronaffinity/kJmol-1PtF6>2.87700F22.87328N.Bartlettaccidentallyexposedplatinumhexafluoridetoair,henoticedachangeincolorandhelatterprovedthecompositionofthenewcompoundasO2+PtF6-.Itispossibletoremoveoneelectronfromtheoxygenmoleculeandisolatetheproduct:O2+PtF6→O2+PtF6-(paramagnetic,2.46BM)Bartlettrealizedthatthefirstionizationenergyofmoleculeoxygenisalmostidenticaltothatofxenon.O2I1=12.2eV; XeI1=12.1eVFurthermore,thedioxygenyl

cationshouldberoughlythesamesizeasaXe+ionbecausetheradiusofO2issimilartothatofxenon.Xer=210pm(vanderWaalsradius);O2r=201pm(rO+dO-O/2=140+121/2=201pm)

Hence,thelatticeenergiesofthecorrespondingcompoundsshouldbesimilar.Accordingtohiscalculation,thelatticeenergyofXe+PtF6-wasslightlybiggerthanthatofO2+PtF6-.Ulattice(Xe+PtF6-)>Ulattice(O2+PtF6-)~10kcalmol-1Hequicklyproceededtoshowthatdeep-redPtF6vaporspontaneouslyoxidizedXetoproduceanorange-yellowsolid.Xe+PtF6→Xe+PtF6-Thefirstcompoundofinertgaswasborn.SincePM6:45,March23rd,1962,Noble-gaschemistryhadbegun.3.3.2CompoundsofXenon1.Xe–F2systemWithinafewmonths,threefluoridesofXehadbeensynthesized.Thermalorphotochemicalactivatingthemixtureofxenonandfluorineresultsintheproductionoffluorides:

Xe+F2

→XeF2 K2XeF2+F2

→XeF4 K4XeF4+F2

→XeF6 K6ThermalequilibriumconstantsofXe-F2systemT(oC)K2K4K6251.2310131.3710118.601052508.791041.431030.9443001.021041.551020.2113501.6710327.20.05584003.591024.860.018250029.80.503.3010-3Thesedataindicate:(1)ThethreefluoridesofXearestableunderroomtemperature;(2)Thehightemperaturesareunfavoredforthereactions.However,thereactionsproceedabove250oCinapplicableview;(3)Thenearlypureformofeachcanbeobtainedbydirectreactionbutconditionsneedtobecarefullycontrolled.Theconditionsincludetemperature,molarratioofXeandF2,startingpressure,andcatalyst,etc.TheeffectofXe-F2molarratio

ontheproductdistribution

Xe+F2

→XeF2 K2

abcc=abK2

(1)XeF2+F2

→XeF4 K4

cbdd=cbK4=ab2K2K4 (2)XeF4+F2

→XeF6 K6dbee=dbK6=ab3K2K4K6

(3)Attheequilibrium,a+c+d+e=p (4)(p=nXe0,startingmolarconcentrationofXe)b+c+2d+3e=q (5)(q=nF20,startingmolarconcentrationofF2)(1),(2)and(3)substitutedin(4):a=p/(1+bK2+b2K2K4+b3K2K4K6) (6)(1),(2),(3)and(6)substitutedin(5):b4K2K4K6+b3(K2K4+3pK2K4K6-qK2K4K6)+b2(K2+2pK2K4-qK2K4)+b(1+pK2-qK2)–q=0

(7)(takenotes)Ifthereactionsoccurunder500oC,K2K4K6=0.04917,K2K4=14.9,K2=29.8,andwesuggestp=q=0.1000moll-1,(7)givesout:0.04917b4+14.91b3+31.29b2+b-0.1=0 (8)

Howtosolvethisequation?Inmathematicterm,wedefine:f(b)=0.04917b4+14.91b3+31.29b2+b-0.1

f’(b)=0.1967b3+44.73b2+62.58b+1For0≤b≤0.1,

f’(b)>0,thereforef(b)isincrementalfunction(b≥0).

b=0,f(0)=-0.1<0;b=0.1,f(0.1)>0Thereforef(b)hasasinglevalueintheregionof[0,0.1]tomakef(b)=0Compareeachitemin(8):ifb=0.1,31.29b2+b+(-0.1+0.04917b4+14.91b3)=0(9)0.31290.14.91710-61.49110-2

First,wesolve31.29b2+b-0.1=0b1=0.04277b1substitutedin(-0.1+0.04917b4+14.91b3)=-0.09883:

Then31.29b2+b-0.09883=0b2=0.04245,b3=0.04246,b4=0.04246

Finally[F2]=0.04246,[Xe]=0.04363,[XeF2]=0.05520,[XeF4]=1.17210-3,[XeF6]=1.64210-7moll-1(1)500oC,p=0.1000moll-1,q=0.2000moll-1,b=?(K2K4K6=0.04917,K2K4=14.9,K2=29.8)(2)500oC,p=0.1000moll-1,inordertoprepareXeF4,calculatetheoptimumvalueofq.Answer：(1)b=0.1170moll-1(2)q=0.6550moll-1TheeffectofcatalystNiF2,CoF3,orCaF2canincreasetheratesignificantly;Evenat0oC,Ag2OorNi2O3resultsinexplosivereaction;Selectivecatalyticactivity.

e.g.

MgF2ascatalyst,120oC,productisXeF2eventhestartingmolarratiois1:10ofXe:F2;NiF2,200oC,Xe:F2=1:5,XeF6.Directpreparationmethod:XeF2canbepreparedbyheatingF2withanexcessofXeto400oCinasealednickelvesselorbyirradiatingmixturesofXeandF2withsunlight;XeF4isbestpreparedbyheatinga1:5volumemixtureofXeandF2to400oCunder6atmpressureinanickelvessel;XeF6

isproducedbytheprolongedheatingof1:20volumemixtureofXeandF2at250-300oCunder50-60atmpressureinanickelvessel.PhotochemicalpreparationofXeF2:

F2showsaUVabsorptionbandintheregionof250-350nmwithamaximumat290nm.1000WHighpressuremercurylampwasusedaslightsource.ThekeyisrapidremovalofXeF2fromthevessel,avoidingthefurtherreactiontoXeF4.2.PropertiesofthethreefluoridesofXePropertyXeF2XeF4XeF6VaporPressure(torr),25oC4.62.528.9Density(gcm-3),25oC4.324.043.56mp(oC)12911750Bondenergy(kcalmol-1)31.030.929.7Bondlength(nm)0.197730.19530.1890GeometricconfigurationlinearsquareDistortedoctahedralChemicalshift(19F,ppm)629450310Chemicalshift(129Xe,ppm)-3930-3785--Chargedistribution(qXe)+1.4+2.2+2.4Chargedistribution(qF)-0.7-0.55-0.4

Chemicalproperties(1)StrongoxidantXeFn+n/2H2

→Xe+nHFThisreactionisusedtodeterminethecompositionofxenonfluoride.XeF2+2HCl→Xe+Cl2+2HFXeF4+4KI→Xe+2I2+4KFXeF2+BrO3-+H2O→Xe+BrO4-+2HF(83SeO42-→BrO4-+e-)(2)FluorinatingagentIncomparisonwithXeF4andXeF6,XeF2isamild,stableandsafefluorinatingagentwithhighconversionandselectivitywhichisusuallyusedinthefluorinationoforganiccompounds.XeF2+C6H6

→C6H5F+HF+Xe2XeF6+SiO2→SiF4+2XeOF4(ThisreactionindicatesthatXeF6cannotbehandledinglassorquartzapparatus.)3.OthercompoundsofXenonItisfromthebinaryfluoridesthatothercompoundsofxeonareprepared,byreactionswhichfallmostlyintofourclasses:(1)withF-acceptors,yieldingfluorocationsofxenon(base:F-donor);(2)withF-donors,yieldingfluoroanionsofxenon(acid:F-acceptor);(3)F/HmetathesisbetweenXeF2andananhydrousacid;(4)hydrolysis,yieldingoxofluoridesandoxidesofxenon,andxenates.(1)ReactionwithF-acceptors.

XeF2hasamoreextensiveF-donorchemistrythanhasXeF4;itreactswiththepentafluoridesofP,As,Sb,I,aswellaswithmetalpentafluorides,toformsaltsofthetypes[XeF]+[MF6]-,[XeF]+[M2F11]-,and[Xe2F3]+[MF6]-.

The[XeF]+ionsareapparentlyalwaysweaklyattachedtothecounter-anionformingF-Xe…F-MunitswithoneshortandonelongXe-Fbond.The[Xe2F3]+ionsareV-shaped.

c.f.

iso-shell-electronicI5-withcentralangle95o,therepelbetweentwoXeatomsbigger.XeF2+2SbF5

[XeF]+[Sb2F11]-InpresenceofexcessofSbF5andXe,thebright-greenparamagneticXe2+

cationhasbeenidentified.3Xe+[XeF]+[Sb2F11]-+2SbF5

2[Xe2]+[Sb2F11]-MOF4(M=W,Mo)arealsoweakF-acceptorsandform[XeF]+[MOF5]-,whichagaincontainlinearF-Xe…F-Munits.XeF4formscomplexesonlywiththestrongestF-acceptorssuchasSbF5andBiF5.[XeF3]+[Sb2F11]-

Xe-F:0.183–0.189nmXe-F(Sb2F11):0.250nmXeF6combineswithavarietyofpentafluoridestoyield1:1adducts.InviewofthestructureofXeF6itisnotsurprisingthattheseadductscontainXeF5+

cations,asforinstancein[XeF5]+[AsF6]-and[XeF5]+[PtF6]-.Inasimilarmanner,reactionswithFeF3andCoF3yield[XeF5]+[MF4]-.TheseadductsofXeF2,XeF4,andXeF6showtheorderofstabilityas:XeF6>XeF2>XeF4ThedifferenceofstabilityisusedtopreparepureXeF4:(2)ReactionwithF-donors.F-acceptorbehaviorofxenonfluoridesisevidentlyconfinedtoXeF6whichreactswithalkalimetalfluoridestoformMXeF7(M=Rb,Cs)andM2XeF8(M=Na,K,Rb,Cs).ThesecompoundsloseXeF6whenheated:2MXeF7

M2XeF8+XeF6M2XeF82MF+XeF6Theirthermalstabilityincreaseswithmolecularweight.ThustheCsandRb

octafluorocomplexesonlydecomposeabove400oC,whereastheNacomplexdecomposesbelow100oC.NaFcanthereforeconvenientlybeusedtoseparateXeF6fromXeF2andXeF4,withwhichtheydonotreact,thepurifiedXeF6beingregeneratedonheating.(3)F/HmetathesisbetweenXeF2andananhydrousacid:XeF2+HLF-Xe-L+HFWhereL=OSO2F,OClO3,OTeF5,orOC(O)CF3.Thefluorosulfateandperchloratearecolorlessandtheothersarepaleyellow.Manyofthesecompoundsarethermodynamicallyunstableandtheperchlorate(mp16.5oC)isdangerouslyexplosive.Thefluorosulfate(mp36.6oC)canbestoredformanyweeksat0oCbutdecomposeswithahalf-lifeofafewdaysat20oC:2FXeOSO2FXeF2+Xe+S2O6F2(4)HydrolysisandrelatedreactionsXeF2dissolvesinwatertotheextentof25gdm-3at0oC,thesolutionbeingfairlystable(half-life~7hat0oC)unlessbaseispresent,inwhichcasealmostinstantaneousdecompositiontakesplace:2XeF2+2H2O→2Xe+O2+4HFXeF4ishydrolyzedinstantlybywater:6XeF4+12H2O→2XeO3+4Xe+3O2+24HFHydrolysisofXeF6occurswithgreatvigor:XeF6+H2O→XeOF4

+2HF(incomplete)C4v,squarepyramidal(octahedral,lonepairattheapex)XeF6+2H2O→XeO2F2

+4HF(incomplete)C2v,“see-saw”(trigonal

bipyramidal,alonepairattheequatorialsite)XeF6+3H2O→XeO3

+6HF(complete)C3v,pyramidal(tetrahedral,lonepairattheapex)InaqueoussolutionXeO3isanextremelystrongoxidizingagent(forXeO3+6H++6e-

→Xe+3H2O,E0=2.10V),butmaybekineticallyslow;theoxidationofMnIItakeshourstoproduceMnO2anddaysbeforeMnO4-isobtained.TreatmentofaqueousXeO3withalkaliproducesxenateions:XeO3+OH-HXeO4-K=1.5103ThealkalinesolutionsarenotstableandbegintodisproportionateintoXeVIII(perxenates)andXegasbyroutesuchas:2HXeO4-+2OH-

→XeO64-+Xe+O2+2H2OThemostefficientproductionofperxenateisthetreatmentofXeO3inaqueousNaOHwithozone,whenNa4XeO6precipitatesalmostquantitatively.3XeO3+12NaOH+O3→3Na4XeO6+6H2O

Perxenatesofotheralkalimetals(Li,K)andofseveraldivalentandtrivalentcations(e.g.Ba2+,Am3+)havealsobeenprepared.Theyarecolourlesssolids,thermallystabletoover200oC,andcontainoctahedralXeO64-ions.Theyarepowerfuloxidizingaqents,thereductionofXeVIIItoXeVIinaqueousacidsolutionbeingveryrapid.TheoxidationofMnIItoMnO4-byperxenates,unlikethatbyXeO3,isthusimmediateandisaccompaniedbyevolutionofO2:2H2XeO62-+2H+

→2HXeO4-+O2+2H2OTheadditionofsolidBa2XeO6tocoldconcentratedH2SO4producesthesecondknownoxideofxenon,XeO4.Thisisanexplosivelyunstablegaswhichmaybecondensedinaliquidnitrogentrap.Ba2XeO6+2H2SO4

→XeO4+2BaSO4+2H2O

Td,tetrahedralTheothercompoundscontainingXe-Cl,Xe-N,andXe-Cbondshavealsobeenprimarilystudied.3.3.3CompoundsofothernoblegasesNostablecompoundsofHe,Ne,orArareknown.Radonapparentlyformsfluoridesandsomecomplexes,buttheevidenceisbasedsolelyonradiochemicaltracertechniquessinceRnhasnostableisotopes(Half-lifeofthelongestisotope,222Rn,is3.8d).Theremainingnoblegas,Kr,hasanemergingchemistrythoughthisisfarlessextensivethanthatofXe.ApartfromtheradicalKrF,whichhasbeengeneratedinminuteamountsbygama-radiationofKrF2andexistsonlybelow-153oC,thechemistryofKrisconfinedtothedifluorideanditsderivatives.Thevolatile,colorlesssolid,KrF2,isproducedwhenmixturesofKrandF2arecooledtotemperaturenear-196oCandthensubjectedtoelectricdischarge,orirradiatedwithhigh-energyelectronsorX-rays.KrF2(tetragonalsystem,a=0.6533nm,c=0.5831nm,Z=4)isathermallyunstablecompoundwhichslowlydecomposesevenatroomtemperature.IthasthesamelinearmolecularstructureasXeF2(Kr-F188.9pm)but,consistentwithitslowerstability,isastrongerfluorinatingagentandisrapidlydecomposedbywaterwithoutrequiringtheadditionofabase.ComplexesofKrF2areanalogoustothoseofXeF2andareconfinedtocationicspeciesformedwithF-acceptors.Thus,suchcompoundsas[KrF]+[MF6]-,[Kr2F3]+[MF6]+(M=As,Sb)areknown,and[KrF]+[MoOF5]-and[KrF]+[WOF5]-havebeenpreparedandcharacterizedby19FNMRandRamanspectroscopy.3.5Somecompoundsofp-blockelements3.5.1Pseudohalogens(CN)2(氰,cyanogen):N≡C-C≡NCN-NC-

氰化物,cyanide異氰化物,isocyanide(SCN)2(硫氰,thiocyanogen):N≡C-S-S-C≡NSCN-

硫氰酸鹽,thiocyanideNCS-

異硫氰酸鹽,isothiocyanide(OCN)2(氧氰，oxocyanogen):N≡C-O-O-C≡N-OCN-

氰酸鹽，cyanateH-O-C≡N氰酸，cyanicacid-NCO-

異氰酸，isocyanateH-N=C=O異氰酸，isocyanicacidN3-(疊氮化物，azide):N≡N=N-

H-N=N≡N疊氮酸Thechemicalpropertiesofthesecompoundsoranionscanbeanticipatedbycomparisonwithhalogens:1.FormationofPseudohalogensbyoxidationoftheanions:2SCN-+4H++MnO2

→(SCN)2+2H2O+Mn2+2SCN-+Br2

→(SCN)2+2Br-

2.Disproportionationofthefreepseudohalogenbyabase:(CN)2+2OH-

→CN-+OCN-+H2O3.Precipitationbycertainmetalions:Ag++N3-→AgN3↓Pb2++2CN-→Pb(CN)2↓4.Formationofcomplexionswithmetalions:Zn2++4SCN-→[Zn(NCS)4]2-Hg2++4SCN-→[Hg(SCN)4]2-3.5.2MolecularStructure1.HalogenNo.ofNo.ofloneNo.ofNo.ofHybrizationGeometryExampleσbondelectronpairπbondσbond+

electronpair2204sp3BentICl2+

221BentClO2-312TrigonalpyramidClO3-

403TetrahedronClO4-2305sp3dLinearI3-

320TClF3

410distortedtetrahedronIF4+

411distortedtetrahedronIO2F2-4206sp3d2square-planarICl4-

510squarepyramidBrF5501squarepyramidClOF4-

601octahedronIOF57007sp3d3pentagonalbipyramidIF7ClF3,C2v,T19FNMR:Fa(doublet,2),

Fb(triplex,1)BrF5,C4v,squarepyramid19FNMR:Fa(quintuple,1),Fb(doublet,4)2.SNo.ofNo.ofloneNo.ofNo.ofHybrizationGeometryExampleσbondelectronpairπbondσbond+

electronpair

2123sp2BentSO2

303TriangularSO32204sp3BentH2S

310TrigonalpyramidSF3+311TrigonalpyramidSOCl2

401TetrahedronSOF3+402TetrahedronSO2Cl2

4105sp3dDistortedtetrahedronSF4

50