George 0. Kauffrnan ond POUI F. Vortanian California Stole College Fresno, 93726
I
I
kopoly and Heteropoly Compounds A general chemistry laboratory experiment
O n e of the prrplrxinp prnhlrms fnenl hy know^ ~ x : ~ m p of I r s w h rr:lrtio~~?i is the r o n d ~ n s : ~ l i o ~ ~ tmrhrm of to,i:ty's prnrrnl rl~rmistryroursr is how to of rhrom:~fr ion to form tlw isopoly ilirhrom:~tr ioll, pn~virlrrh:~lltweing nl:~trri:d whirl1 is of f ~ ~ n d n n ~ r n t d:III n111iIihri11n1r c ~ r t i o nt h r rxtrnt of whir11 is (leprnimport:lnrr yrt wlrirl~clocs not cluplir:~tem:~lrri:d nldrnt upon t h r p l l of the systrm rr:dy n ~ : ~ s t r r rhy d s t u c l r ~ ~ with t s superior hip11 srhool ern,=- + 11' = ICrC),Olllh : ~ r k p r o ~ ~ ~Indrccl, ~ l s . rvcw for rollrpr s h d r n t s with 2ICrOrOlll- t IOEr--0-CrOtllllrO I I O prrvims tr:~iningin rhcm~istry,tlw grncwl rhemistry l:~hnr:~tory r:ln nltrw drgrnrratr into :I plnrr whrrr tlw III :wid rnl~ltiont h r complrx ion Cr20,?- p r n l n m i ~ ~ : ~ t r s , S ~ I I ~ ( - Ivrrifiw I~ ( * x l ~ r r i ~ ~ ~ (the ~ ~f:wts ~ t : ~:lIlI yI ~pri~wiplrs w l ~ r r r : ~i lsl h:~sies n l ~ ~ t i othe n simplr inn C'rO,?- is the t11:1t 11:1vr:lIrcwly IICVII rxpI:~innlin trxt X I I ~Irrt~~rc*. prinrip:~lsprrirs. I t is with this prohlrm in mild th:~t(lurinp the inst In hrlrn~l)olyacids t h r rrntr:d :ltom may rnnrdi~lntr drr:ldr wr I I : I ~ P p ~ ~ h l i s h rind ~ t i JWIIS.AI, ~ s :I ront inuwith from lour to six oxy:~nions. T h r l:~ttrrmny b r ing srrirs of pr~lrr:llrllrmistry I:~tmr:ltory rxprrimc.nt.i mono:~nirrns, :IS in l17[l'(11nOt)~],or tri:~nions, :IS in involving srhrrl:~stir:~lly~ ~ r g I ~ * rtyprs t n I of rompo111111s ( \ V 0 ) I ~ ~ r o m p l r t rq)l:~crmrnt c~ of oxyprn : I t r r l ~ ~ i ( q I~ -~ r 111rurh rxprrimrnts the .sf~~rlrnt :ttnms in 0 prnup* I I ~1 0 I I yi(M is givrn :III o p o r t ~ ~ n i t to y ntilizr :I cor~siclrr:~hlr dimws, r.g., ~ O I ' [ O ( ~ I I I O ~ ) ~ II~l ~~t~r r' n~p-n. l yrlrrtrn:1mo11111of his k ~ ~ c ~ \ v lof ~ ~t hI g~ r r t i r : drhemistry : I I ~ Iytrs :Ire t1111s:I I:lrpe ~ I I I I C ~ : I ~ I P If:lmily I ~ : I ~ ol si~lts:IIIII to r s p : ~ ~ ~his c l ~ ~ s ~ ~ lin~itrd i i l l y ~ I I O \ Y I N I ~ Pof dwrriptivc f r r r :~ricls,r:wh mrnmhrr e m t : ~ i n i ~:I ~rompl~.x p :~nionof rhrmi*t ry. TIIPprrscnt e x p r r i m r ~ ~dr:~ls t wit 11 :111ot11rr high molc~ul:~r \wight. As m:my :IS 31; diNerrnt el* r1:ls.i of i n t r i p ~ i ~: ~ np d"rsotir" r o n ~ p n ~ ~fl1:11 ~ ~ d:ire a mrnts hnvr hrcn rrportnl to fr~nrtion:IS crntrnl ntoms ~ w l lON t l l r hr.:~tw tr:~rkof both Irrtr~rr:ind l:~bnr:~- in distinct hrtrropr~ly:~nions(Tt~hlrI). Sinrr m:tny t o r y - i q x ~ l y : I I I ~ h ~ t e r o ~ n ~s:~lts l y : I I I ~ thrir p:Irrnt :~rirls. Two nrt irlrs on t hrsr rompollnds hnvr "11Table 1. Elements Copable of Acting as Central pn~rrclin TIIIS .IOI.IISAI. (7, A'), hut thry :we p11rrIy Atoms in Hetero~olvCom~wnds11 2) t I ~ r o r t i r : ~il I i s : ~ n d 110 nnt clrsrrihr rxprrimrnt:~l ~)rnredt~rw.TIIP prcsrnt :~rtirlr11ot only i11r111drs: ~ r t ~ prcy:~r:~t ~nl ions h11t :IIW int r o d ~ ~ rthe r s hrpi1111i11g st1111r11tto l i q ~ ~ i ( l - l i q ~e ~x it dr n r t i n ~ ~titrntion, , I I~ I ~r:Ir v:~rirty of syntl~rtic inn rxr11:111pr,r o n d ~ ~ r t : ~: ~ , : I I ~:111:1lytir:11t c r l ~ n i q ~ ~ ~ ~ s .
+
Introduction Definition (9-1 9 ) T h r \vr:~li :iriils formnl frnm t h r nmphntrrir mrt:lls of thrse rlrmrnts CIII :wt ns centr:~lntoms in more th:m of G M I I ~VR S (V,S h , T:I) :in11VIB (Cr, 110, \V) of t h r one srrirs of Ilrtrrnlmly :~nions,the n11mhrr of possihlc l'rrio(liv T:~hlr:Ire rh:~rwtrrizr(Ihy tlwir m s r in rollncids nnd s:~ltsis ohvio~wlygrc:it. 1:11rthrrmorr, more i l ( w i l ~ gto form : i n i o ~ ~r m s ~ t : ~ i ~ .WVCT:II ~ i n p mol~c111rsof eomplir:~trd:~niot~s ront:~ininp"hrtrn) :~toms"of t\vo t h r :1ri11 :11111wIridr. S I I ~ IrIn n ~ l r ~ ~ s:wids, w l ront:~ininp diflrrrnt elrments h a r e rercntly hrcn prrpxrnl (?0-9.3). n~llyonr type. of :wid :~~lhydrirlv :lrr known :IS isopoly T h r hrtrropoly :lcid.i rlrrivrd from molyhdir and tunp:will* : ~ n dthrir s:~lts:IS isnpnly s:~lts, T h r s:mr :wid p : ~ r t i c ~ ~ l : ~~r l~y ~ n r r In ~ sthe , com:~nhydridrs?:III rnndrnsr with o t l ~ r r:~ricls,r.p., pl~ns- stir i s r pounds clcserihed in this rsperimrnt are lirnitcrl Inrprly pl~nriror silirir : ~ r i ~ lto s . form hrtrropoly : ~ r i ~ l s . t o these romlmt~nds. 111prinriplr, t h r r o ~ ~ ( l r ~ ~ s :prnrrw ~ t i n n is t h r me for nll r:wrs, viz.. f~rrm:~tion 111O ~ I hrirlgvs I hy tlw eliminaHistory (7, 12-1 6) tion of w : ~ t cfrcm ~ t\vn molcw~lc-sol tl~r\\di wid lh:~t is rnnjug:~trto tllr :wid of t l ~ systrm. r S I I ~ IeIo n d r ~ ~ s : ~ - A l t h o ~ ~ gTsigdinos h (I?) ntt rihutw the prep:~r:~tion l i n ~rr:wl ions pcmrr:~llyt:lkr pl:irr frrrly : ~ n drrvwsihly of the fir-t hrtcropcrly compounds (hctrrnpolymolyhI I i l u t : I I I I I I I I ~ ~ IT hI r simplwt : I I ~ hrst clntrs of Cr(1Il) : I I I ~il.r(IIT)) to S t n ~ v in r 1R.J.l (?.$),he n ~ dO ~ I I C M (7, 19-IC) :~ckno!~Irdg~ thnt :IS wrIy :In IWfi R r r s e l i ~ ~ s(25, Zfi) p r r p : ~ r ~ :~mmonium I 12m o l y b c l ~ ~ l ~ l ~ o s:~~~nld~drtrrmincd nte its rntios (XIolyt11111p:t:1trs, the hmt undertaken, but this lnrli (lid not prrvrnt the elnbornknorvn hrlmqmly rompnund~, :Ire itlso in grnrral tion of u n s u r c r d u l theorim to :~ccount for their rIi:~r~~rtrristic of other nrrirs of hrtrrnpoly romlmudx lllomstrnncl (30-32). Gihhs s t n ~ c t u r r shy 1ilt.in (El), ns ~ v r l l (.3.3), C O ~ R I I(d4, X 3:;) : ~ n dothrnr. Copaux (34, .95) ronsicler~lisopoly ncids :IS hrtcmpoly itrids in whir11 tlouhle water n~olrculw(H,02) were nxqumrtl to he tlw seroncl :u~hyclrielr. Although incorrert, this iclen st:~rtrtl 1:itrr \vnrkrnr r~long the corrret path. Thus I 1!l0i n p p l i ~ lhis cnnrdinntion thmry r n r r ) ( - 4 I the stnrrt:~n. of 12-I11nptosiliric :~citl (1I[Si\VlO0]) nnd its wits by ~ixsun~ingthat the rentml ~ o u inp nu Si0,'- ion surmunilrtl c ~ r t n h ~ l r n l l y by six R\V?O0+ gmups (R = a unipositive iou), four linkrtl by 11rim:ir.v (i~mir)nnrl two l i n k ~ hy l serondi~ry (roordin:itr rowlent) vnlrners. N'ith this system, cliffieultirs wrrr rnrountrrrtl i t :~ricls having II rrntr:~lion with :h v:rlrncc other t l u u ~four or cont:~ininp metal :~nhydritlr sggrrgntio~~swhich ere not mirltiplrs of six. llinl:~tiin IWU (41) and Rosrnheim nnd cn-\vorkrnr ( 1 1 , 4 2 ) , hc.ginning in l ! , x t e n l l \\brncr's idms in nn n t t r n ~ p tto ineluclc n \ v i h variety of rom1n~111ds aud to rxplnin the l : w ~uumhrr of rcplnrc : ~ h l rhyclmgrn ntoms in m:my of thrse iwicls. Acrortliug to thrir thmry enrh hrtrrnpoly arid is clrrivrcl frnm n hypothrtiral pnrrnt nricl HI,,-.,[S"+06] of octahrtlml configurntion by rrl)liwing any number of the oxyprrr :Itoms by v:~rio:~rculic:~ls. Hrtrmpoly nrids or "~~nsntur:~trcl."clepr~~~l~ v r r ~ * r l : ~ . ~ns s i f"sntur:~tcd" ii~l ing on \vhrtl:er or not all the oxygrn :ttonis hncl hwn r t ~ l ~ c lI:or . exnmplr, in the rxse of hcntrrnpoly n~olghtl:~ten ~ u ~tun@ntm, cl the most nurnrrnus and hmt k n o ~ w of surh eornlmuud.i, the rndicnls lfnO,?-, lYO,'-, ll&l?-, or \V?O,t- could rrpI:~rr:dl the oxypcn Hrtrmlmly :inions ni:~yh r rl:~ssilinl:~rronliup111 t h r ntoms of hypnthri'irtil p n r n ~ t:rricls surh as H111'0.1 r:~tioof t h r uumhrr of rrntr:d ntonis to the uumhrr of nnrl Hr[SiOsl t o yirld hrtrrnpoly nrids 11~[1'(\1nO~).], ninlybtlrnum, t u n p t r n . v : ~ n ~ ~ d i urtc. m , :~tnnw. ('omJJ,[P(\VOJa], H ~ [ l ' ( \ l t ~ 0 7 j 6 ] H7[I'(\V207)~], , I18[Si~ o u n d wit11 s t h r s:lnir numhrr nf :Itoms in tlw n n i o ~:1rr ~ (\loo,).], H [ S i ( \ I o O ) , II,[Si(lIodh),l, rind H*[Siusunlly isomorphous nud poswss simihr rhrmirnl (\V?O,)el. The lliol:~ti-RosrnhPim thrnry possrxsrcl ~ ~ r n p r r i i m The . prineip:il arrirs of hrtrropolymolyht h r :ulvantngr* thnt i t ronrrivnl of t h r compounds as datcs nrr shown in T:~hlc2. rlrrtmlyirs : u d plnrrcl t h r eorrrrt toms of positive oxidnt inn stntr in the rorrrrt prnporfiot: in the :winns. Nomenclature (1 1, 12, 5 1 ) It p o w w n l , h o u w r r , the clia:~tlv:u~t:~grs that it. roulcl The nomrnrlnture of thew r o m p u ~ ~ dhas s in t h r not s;~tisf:~rtorily rxplnin nll c o n i ~ ~ o u n tthat l ~ , it clid not pwt hcen rh:~r:~rteriznlhy murh inconsistn~ry. nlwnys prrdirt the rorrrrt m:~ximunihsnirity for ninny ~ s u a l l ythe , ni~nwof the crntrnl ston), with or \vithout nricl.ior t h r lr~rgrnumhrrs of witrr ninlrrulrr rontninrcl Grrrk prrfixcs, wns p r r f i x ~ lto t h r \vortls "molyhcl:~te in such rompounds, and, most import:u~t,thnt it de(tungst:~tr)" or "ninlybdir ( t u t i c ) ' :wid, r.g., pendrcl U ~ O I Ithe cxistcucr of "l~yro" \1?0, groups in "~~l~osl~l~ornolyb~l:~tr" or "cloclrr:~tr~~~gstosilirir nrid." solution, :I f:~ctproven for Cr?Olt- hut not ronrlusivrly 111tlw I(.l';\(' systrni (;;I), l m n r s hrpin wit11 :III ,\r:~hic ~lrmonatr:~trcl for other r:~dir:~ls. it1 of n~nlylxlr~~urn r ~ u m r n rlrsig~:~tir~g ~l t h r simplr*t c~t Srvrr:~lothrr v i r w of tlw stnlrturr of hrtrrnpoly or t u n p t r n tonis is to t h r centml :itom followc~lhy the coml~ounds\vrrc nclr:~nrrdi n suhwqurnt yrnnr, hut t h r Volume 47, Number 3, March 1970
/ 213
Table 2.
Principal Soecies of
I ) If the mwtrnl n t m n is n iwn-Irntndion rlrm~nt,R IIOIIII~IP mnlyhclntr air t w t ~ s t n t ,mny ~ lw di,rnlvcd with n i-olul,lr salt. Rmlniuinz l h ~ v ~ n l r :nt tl # m ~it8 t h ~ ~ t ~ ~ ~ ~ r ~ ~ *trite, ~ ~ r i t ~ l e '21 If Ihe w n t r n l ntom i> 1, tr:an4:i\ ,wlutiw ccmtni~~ing I!W g d Sn:\\'O,.L'IId), 4 rnl of glnrinl lI('JIIO?, nwl .Ill m1 01 wntrr is mMt~~l ~lwly with c~mvtnntstirring t a b a lmili~ngd u t i o n vamtnining 2..i g of C ~ ~ ( C ~ l l , 0 z ~ , ~#me 4 1drop 1 ~ 0 of , ~ I w i n l l ~ ~ ~ l lnud ,ll~, I?..; ml of m t r r . The ~ I I I I I I I I )iu filt(.~.(*l h,.Acndemi? l'rws, S e w S w k , 1965. V d . 2 , p. 1712, 153.1) RdrrrncclS2l. s. 1711.
(2nd
..
:.
R d r r m r r r52I.p. 1739. l,nsr, ,\.,Ir4rf. &:no, Chtm..IS,4.59 11943). IIAILIR. J. ('..ln~wanirSynlh,l~, I,13Z(I9391. S o w r ~E.. . \ . . l n o r p n r ~ r r T ~ , n l h r n e " .I,l~llI!~:l111. S T R ~ V K ~ .
