Recent Survey on Organophosphorus, Organoarsenic, and ~olymol~bdates and ~rganoa~imony~olytung~ates Ben-yao Uu,Gao-yang Xie, Yih-tong Ku Fudan University, Shanghai, Chlna
The structures of organophosphorus and organoarsenic polymolybdates were determined by Pope in 1975and 1976, respectively (1.2). They are compounds consisting of a ring of some linked Moos octahedra with two organic handles above and below the molybdenum ring (3), see Figures 1 and 2. In some cases (organoarsenic polymolybdates), a ring of four Moos octahedra are linked together with only one organoarsenie handle protruding (4), see Figure 3. From more acidic solutions (pH about 0.5) the 4:12 anions, dodecamoIvbdotetrakis-(orcanoaraonates) have been isolated and iharacterized (5);Figure 4 shows the structure of this giant anion. They consist offour croups . . of three Moor octahedra bridged by~fourorganoarsenic moieties. Within kach group the octahedra share edpes, and thev share corners between groups. A survey of het&opolymoly-hdates was given in 1977
(6). The organophosphorus and organoarsenic polytungstates were synthesized by Pope in 1981 and 1978, respectively (7,E). Although the crystals of organophosphorus polytungstates have not been obtained yet, the structures of organoarsenic polytungstates have already been determined, see Figure 5. In comparison with molybdenum derivatives, the tungsten derivatives are more difficult toprepare, so that the number of compounds reported in literature is much less. After all, this research field is still in its juvenile stage. Nevertheless, so many new compounds have been synthesized and characterized that some previous speculations must be changed. When the structures of organophosphorus and organoarsenic polymolybdates were first determined in 1976, Kwak et al. stated that only one type of organoarsenic polymolyb-
Figure 3.
Flgure 5.
[(Me)2AsMor0,rH]2-.
[(P~AS)~W~O~~H]~-. Volume 67
Number 10 October 1990
tion studies and elemental analyses show this compound is date [ ( R a ~ ) ~ M o ~ 0was 2 ~ ]formed ~a t pH = 3-5 regardless of different from that reported hv Matsumoto but is isostrucwhether R was an alkyl group or an aryl group (2). They only reported the crystal structural data for a double salt of the tural with its tungiten congener ( C N ~ H ~ ) ~ [ ( C ~ H ~ A S ) Z .6H2O methyl derivative [(CH3)4N]Na2[(CH3As)2M0602J Ws025H].2H20 reported by Wasfi et al. ( 8 ) .I t seems that (2) and took i t for granted that all alkyl- or arylarsenic the ring no longer consists of six edge-sharing Moos octahepolymolybdates belong to the same type. It was soon demondra when the arsenic atoms are connected to phenyl groups. Instead, the ring consists of one face-sharing, two cornerstrated that the situation was not so simple. Two years later sharing, and three edge-sharing MOOGoctahedra. When a Matsumoto reported the crystal and molecular structure of a monosubstituted phenylarsonic acid such as o-, m-, p-nitrog u a n i d i n i u m s a l t of t h e p h e n y l d e r i v a t i v e phenylarsonic acid reacted with sodium molybdate, [(RAs)z (CN3Hs)4[(C6HsAs)2Mo6O2~H2] .4H20 (9).When n-propylarsenic polymolybdates were prepared in our laboratory, we M O ~ O ~ ~type H ] ~of- complexes, not [(RAs)2MosOz414-type, were formed (17). Single-crystal X-ray diffraction studies of found a unique phenomenon: two types of crystals, containins numbers of rine molvhdenum atoms. were . ~different ~ " derivative show that its molecular the o-nitro~henvlarsenic . . formed under thesame pH con;fition'from thesames&tion structure is similar to that of the phenylarsenic derivative 110). The six-molvhdenum comoound (CN?Hc),l(n-CcH, but one molvbdenum atom is five-coordinated (18).Figure 8 - .. shows this particular structure. When henzyl-arsonicacid, A S ) ; M O ~ O ~(11) ~ ] -is consistent k i t h Kwak's prediction, which contains a phew1 group not directly connected to the whereas t h e five-molybdenum compound (CNsHdr arsenic atom, reactedwiih sodium molybdate, the [(RAs)z [(n-C3H7As)zMosOzJ 2H20 (12) is isostructural with organophosphorus polymolybdates (13). I t is the first example Mo6O24I4- type of complexes, which is also consistent with Kwak's prediction, have been synthesized and characterized of arsenic complexes analogous t o [(RP)zMoa02J4-, see Figure 6. (19). In the case of organophosphorus polymolybdates, five new Before 1988 i t was predicted that the corresponding alkylphosphorus polymolybdates have been prepared (20). As.Mos " " anion did not exist due to the larger covalent radius They all belong to the [(RP)zMos021]4-type. Attempts to of arsenic atom. Some papers have also stated that the prepare complexes of [ ( R P ) ~ M O ~ Otype ~ ~have ] ~ - been unsucMo~0.xrine is suitable to accommodate PO4$- or R P O F cessful so far. The crystals of ( C N ~ H ~ ) ~ [ ( R P ) ~ M Owhere ~OZI] g r ~ ; ~ s - a n the d Mo60z4 ring is suitable to accommodate R = n-C8H17,n-C9H19,and nC16H33have not been obtained RAsOnZ- croups (2, 14). After the X-ray crystal structural vet. The crvstal structure of guanidinium pentamolybdoinvestigation of the first example of pentnmolybdohis(ork(n-amyldhosphonate), whichcontains thelongest carbon ganoarsonate), we hoped that some other compounds bechain hitherto known, has been reported (21). The average longing to the [(RAs)zMos021]4- type would soon be synthehond angles 0-P-0 have been estimated if the anion sized and characterized. Shortly afterward the second examI(RP)2Moe02414-can be formed. ple of this type (CN~H~)~[(CH~=CH-CHZAS)~MO~OZ~]~In the caseof organoarsenic polytungstates, the "degradawas isolated (15), see Figure 7. These two examples demontion method" using sodium metatungstate as a starting matestrate that the stable existence of the anions of [(RAsL rial instead of sodium tungstate has been suggested for the Mo5Ozll4- type is by no means a fortuitous phenomenon. preparation of organoarsenic polytungstates. Six guanidinThe larger arsenic atom has a considerable effect on the ium salts of arylarsenic polytungstates have been prepared by geometry of the Mo5015 ring in a very similar way. Furtherthis method (22). They belong to three types of complexes: more. the allvl noups enable this new type of heteropolyan[(RAs)2W6025H]5-where R = %Ha, o-NOnCsH4, mion to be easier-forked and stabilized, a6 that only the fivewhere R = p molvbdenum compound can be isolated. When phenylarN02CsH4, p-N02CsH4, NH2CnHa.and I(RAs)7We07#where R =' 3,4-CsHdNOd sencc po~ymol~bdates were prepared in our laboratory, only . . -~. ( o H ) . ' T ~ ~degradation method has the. advantage in the (CN.jHti)5[(C6H5As)?Mo60~5HI. H2O could he isolated from simplification of reaction products, thus leading to their highthe solution at pH = 3-5 (16). Single-crystal X-ray diff'rac~~~~
~~
~
~
*
-
b Figure 7.
884
Journal of Chemical Education
[(C~H5As).Mo.0.,]4-
Figure 9. [MeAsW,02,H]'-
er yields. The crystal and molecular structure of guanidinium p-aminophenylarsenic polytungstate tetrahydrate has been determined (23). From weakly basic solutions (pH 7-8.5) of RASO~~of WOd-, the anions [ R A s W ? 0 2 7 H l 7 - have been isolated and characterized (24), see Figure 9. The W 7 0 2 4 group comprises a horseshoe of four edge-shared WOs oetahedra linked at four vertices to a triangle of edge-shared odahedra. There is no report of analogow organoantimony "handlelike" complexes in the literature. AU attempts to prepare crystals of arylstibonic polymolybdates or polytungstates from aqueous solution have failed so far (25).We have found, however. an entirely new tme of organostihonic molybdate, the tetra-n-butyl a&noni& salt ofdiphenylstibon&olybdate l(n-CaHs)aNI?I(CfiH~,)~SbO(MoOr)ll. obtained from organicsolvents. 11 Lihe firstknown type of crystalline organostibonic molybdate. Itr anion consists of two Moor tetrahedra bound to two octahedrally coordinated antimony atoms (26), as shown in Figure 10. Summary
A recent survey has been given of the work synthesizing and characterizing many examples of organophosphorus,organoarsenic, and organoantimony polytungstates and polymolyhdates. Although the dimensions of the RPO? and RAs0a2- tetrahedra are very much different from each other, very similar [ ( R P ) 2 M 0 5 0 ~ ~ ] 4 and [ ( R A s ) 2 M o 5 0 2 1 ] ~ - anions can be formed. In addition, the complex anions with the stoichiometries [ ( R A s ) z M o e O 2 a l 4 - , [ ( R A s ) z M o s 0 2 5 H I 5 - , [ ( R A S ) ~ M O I Z ~ and ~ ~ ] ~[RZASMO~OI~H]~-. can also be formed. In the case of organoarsenic polytungstates, the complex anions of t h e types [ R A s W , O ~ ~ H ] ~[-(, R A S ) ~ Ws025H]5-, [ ( R A ~ ) ~ W 6 0 2 5 ] ~ - and , [ ( R A s ) ~ W ~ O Z ~have ]~been characterized. There is no report of "handlelike" analogous organoantimony complexes. An entirely new type of anion f R 2 S b O ( M o 0 3 1 2 2 - has recently heen synthesized and characterized.
Figure 10. [Ph8bO(Mo0,)]*z-.
Lherature Ched 1. Kwak, W.; Pope. M. T.; Seu1ly.T. P. J.Am. C k m . Sac. 1375.97.5735. 2. Kwak, W; Raikovic, L. M i Sfsriek, J K.; Pope. M. T.;Qui&mll, C. 0. inors. Chem. 1976.15,2778. 3. Cotfon,F. A.; Wilkinaan, G. AdurncdInorgonic Chemistry. 4thd.; Wiley: New York, 1980:p859. 4. Barkigia, K. M.: Rajko*c.L. M.: Pope. M. T.: Quickaall, C. 0.J Am. Chem. Soc. 1975, 07 " > A C
5. Barkigie, K. M.;Rajkcm!e, L. M.: Pope, M. T ; Quickdl, C. 0. Inorp. Chem, 1981,20, 23,n
6. Pape,M.T.:Quiclrsdl,C.O.;Kwk,W.:~kovic,L.M.:Stalick,K. J.;Barkigis,K.M.: Sedly,T. F. J. k s s - C m n M&. 1977, M. 129. 7. Sethursman.P. R.:Leparulo,M.A.;Pop,M.T.:ZonnevijUe,F.:Bmnud,C.;Irmerle.J. J.Am. Ckam.Soc. 1981,103,7665. 8. W d . S H.; Kwa*, W.; P0pe.M.T; BarLigia.K. M ; B u t c h h , R J.;QuieMl,C.O. J. Am. Chem. Soc. 1978. IW. 7788. 9. Ma&umoto, K. Y. Bull. Cham. Sot. Jopon 1978,51.192. 1 0 Liu,B. Y;Ku, Y. T ; Wang, M:Zheng,P. J.lnorgChem. 1W27,3388. 11. Wang,M.:Zheng,P. J.:Liu,B. Y.;Ku,Y.T.AetoPhys.-Chim.Sin.1987,3,4sS. 12. Wang, M.; 2heng.P. J.; Liu, B. Y.; Ku, Y.T. Acla Cryrfollogr 1988, C44.1503. 13. Stslick, J. K.:Quiekd. C. 0. Inarg. Chem. 1976,15,1577. 11. Filowifl, M.: Klempemr, W. G.J. Chem. Soc., Chem. commun. 1976,213. 15. Liu.B. Y.: Ku,Y.T.; Wang.X.Inorg. Chim.Acta l989.!61I21,233. 16. Liu.B.Y.;Ku,Y.T.: Wang,M.:Zheng,P. J.ArtoChimSin.EngliahEdifion,inpmm. 17. Liu, B. Y.: Ku. Y. T. Chem. J. Chinese UGu. 1989.10(5).453. 16. Liu.B. Y.; W q , X.;Xie, G. Y.: Xu,Y.T.,submitted for publication inPolyhedmn. 19. Liu,B. Y., Ku, Y. T.: Wu, 0.; Zheng, P.J. Act. Chim. Sin. English Edition 1989.5.4CO 20. Li".B. Y.:Qin,Y.:K",Y.T.lnorg.Chem. (C.C.S.), inp-. 21. Liu, B. Y.: Wang. X.: Ku, Y. T. Chsm..I Chinese Uniu. English Edition, in p-. 22. Liu,B.Y.: Ku,Y.T.; Wang,X.Aefo Chim.Sin.EnglishEdifion, 1989,2,152. 23. Liu, B. Y.; Ku, Y. T.; Wang. X. Aeto Chim. Sin. English Edition, ?npreM. 21. Jameson.G. B.; Pope, M. T.: Waafi. S. H.J Am. Ckem Soc. 19N,107,4911. 25. Ku, Y T ; Llu, B. Y. Ckem. J. C k i m Unjv English Edition 1987,3,1. 26.
Liu,B.Y.;K~.Y.T.;Wang,M.;Wang,B.Y.;Zheng,P.J.J.Ckem.Soc.,Chom.Commun. 1989.10.651.
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