HIGHLIGHTS Distorted Sandwich Compounds: [ l]Ferrocenophanes and Ruthenocenophanes** Max Herberhold* lic compounds are potential monomers for ringopening pol!.nierization. and strained metallocenophanes have consequcntl) attracted interest as precursors for polymcrs containing iI;insition metals such as Fe or R u in the cage of sanduich unit\ t h a t are incorporated into the macroinolecule.[llThe propensity towards polyinerization depends on the ring strain. ;IS may be seen for the sila[ii]ferrocenophanes['] fc[ (SiMe,),,] with / r = I ( I ) and / I = 2 (2). Whereas 1 polymerizes i n the melt above I30 C ' to give silaferrocenylene polymers.[312 requires temperatures above 350 C to undergo ring-opening polymerization.l'. Nevertheless. i t is easy to oxidize fc[(SiMel),] 2 to I .3-bis( diinet ti).lsila)-2-oxa-ferroceiiophane fc[ (SiMel)lO] uhich. like te[(SiMcZ),]3, is strain-free and therefore not prone t o poI!iiieriL;ltion." es. for example in the series 4-6. To date [Ijtkrrocenophanes containing elements of the second row of the periodic table (E = B. C. N . 0) as bridges have noi been synthesized. The smallest bridging element possible appears to be sulfur. and the Fe SiPhZ PPh Fe Fe 0 S L3 fc[SiPhZ] (red) 4 Pal fc[PPh] (red-purple) 171 a = 269" a = 192" b= 167 3" p = 40" B = 99 l( 3) " 1598" p = 32 3" O = 90 7(2)O 1s. fc[S] (violet) 6 151 (x = 31 05(10)" i i = 156 9(1)" p= 288,291" t)= 89 03(9)" (Very similar an les are given in ref$bl) fc[SiMe,] fc[Si2Me4] 1 u = 20 8(5)" 2 "' 6 = 164 74(8)" a = 4 19(2)" (4 3" 121) 6 = 176 48(3)" The ring strain i n [ l]ferrocenophanes. which contain just a single bridging atom as it link between the two cyclopentadienyl ligand\. i b coineniently described by the tilt angle c1 o f the rings a n d the defortnaiion angle (iat the metal between the midpoints o f t h e rings. (Fig. 1, cf. ref. [ 3 ] ) The . tilt angle c1 increases as the size (ix. the co\alent radius) ofthe bridging element E decreas- new thia[l]ferrocenophane fc[S] 6. prepared by Ian Manners and co-workers,[5Jholds the present world record thr the largest tilt angle in [l]ferrocenophanes with x = 31.05( 10) . The conformation of the two cyclopentadienyl rings in 1 atid 4 - 6 is almost exactly eclipsed. As expected, the ring strain is reduced when the bridging atom is ;I heavier homologue. a s for example in diphenylgerma[llferrocenophane fc[GePh,] ( X = 16.6. (5 = 170. /i= 32.5, and 11 = 90.6 )("l and in the substituted phenylarsa[ 1 jferrocenophane f~'[AsPh] (fc' = (C,H,)Fe(C,H,R). R = CHMeNMe?; x = 22.9. Ci =162.5. /I = 32.8. and (I = X7.90(7) )."I Apparently only u single inetalla[l]ferrocenophane has been structurally characterized: f~[Zr(C,H,rBu)~l7 (3 = 6.0. t i : 177.27(8) ):['I the inetal-metal separation. tl(Fe-Zr) = 796.21(5) pin. might indicate a weak bonding interaction. 4 fc[Zr( CsH4tBu)~l 7 Pi u=60" 6 = 177 28(8)" MCp2 8a M = Fe ( d = 332 prn) 8b M = R u ( d = 368 prn) 8c M = 0 s ( d = 371 pm) Whereas it h i r number of [ I]ferrocenophane\ are now available. the isolation of the first [llruthenocenoph~ine.rc[SiMe,], was mentioned onl! in 19Y4.r'1 and the first 1-u~Iienocenoph~tnes have been described by Ian Manners and his group only recent- HIGHLIGHTS ly. ' l o , ''I As the intramolecular ring-ring distance in the parent metallocenes MCpz 8a-c expands on going from ferrocene to ruthenocene and osmocene, the distortion in the corresponding - and metallocenophanes must similarly increase. This might explain why dimethyldichlorosilane Me,SiCI, reacts with 1,l'-dilithioferrocene fcLi, to give fc[SiMe,] 1,[''] while the corresponding reaction with 1.1'-dilithioruthenocene rcLiL leads preferentially to oligomers and polymers. The binuclear bis(dimethylsila)[l .l]metallocenophanes 9a,b were prepared by a different route [Eq. (a)];['31 it is conceivable that small amounts of the strained mononuclear monomers fc[SiMe,] 1 and r~[SiMe,]['~are formed under these conditions as well. e 2 S I M e ? e LI LI + 2 MCl2. nL e S i M e 2 - 4 LlCl M ____) (THV &s, n S GS e S i M e 2 (M = Fe , nL = 2thf, 9a : fc(SiMe,),fc M = Ru , nL = 4dmso) 9b rc(SiMe2)2rc1131 14 R = H : fc[S,] "'I -CMe2 M I (R = H, nBu, Wu) a= 285" S = 177.7" macromolecules 14; again substituents on the rings are required to obtain soluble products. When 4-tert-butyl-I ,1',2,2bis(l.2,3-trithia)ferrocenophane(15) is used as the monomer, giant three-dimensional networks contain(a) ing disulfide bridges can be obtained.[2'] In spite of the synthetic achievements in the chemistry of distorted sandwich compounds, some questions still remain open. Thus, points of discussion are the disturbed intramolecular interactions between e-, [MI / &E 15 M n 13 In all cases (2, 10- 12) where analogous ferrocenophanes and ruthenocenophanes have been structurally characterized, the ruthenium complex is always the more strained.[l3] As expected, an almost linear correlation exists between the distortion angles a and 6 in [I]- and metallocenophanes. 6Yb - nBu3PS * M *SiMe2 M . 16 E = S, Se, Te [MI = metal complex fragment I eCb eCMe2 eSiMe2 IOa : M = Fe a = 21.6(5)" l l a M=Fe"" a = 23' S = 163.4(6)" 12a : M = Fe a = 4.19(2)" '= 176.48(3)" 10b . M = Ru a = 29.6(5)" 6 = 159.3(2)" l l b : M= Ru"~] a = 30.6/31.5" S = 159.21158.3" 12b : M = Ru [''I a = 7.8(5)" 6 = 174.2(2)" (two independent molecules in the cell) monomer fc[S] 6 is expected to lead to poly(ferroceny1ene sulfide) [fcsln. A yellow product Of this was Obtained earlier from the reaction of 1,l'-diiodoferrocene fcI, with the copper salt of 1,l'-dimercaptoferrocene fc(SCu), in boiling pyridine;"71 it is insoluble in all common The presence Of substituents on the rings is amarentlv necessary to obtain tractable sulfur-bridged ferrocene polymers, which might be new materials with special properties due to the regularly arranged Fe centers. A modified ring-opening polymerization leading to POIY(ferrocenylene disulfide) [fcS,], 14 (R = H) was discovered by T. B. Rauchfuss and co-workers [Eq. (b)] . [ 1 y - 2 2 1 Starting from the unstrailled 1'2'3-trithia[31ferrocenophanes 13, abstraction Of the central sulfur atom using PnBu, generates one-dimensional I Y . I iron and the cyclopentadienyl rings or the possible contacts of iron to the bridge elements. An attractive synthetic target for the near future will be the preparation of polymeric materials with different metals, either from metalla[l]ferro~enophanes[~. 231 or from ferrocenophanes 16, which contain transition metal complex fragments in the bridge system (cf. ref. ). German version: A I ~ , ~ EChew. I I . . 1995, 107, 1985-1987 Keywords: iron compounds . metallocenophanes . polymerization ruthenium compounds . sandwich complexes to 7iuii.siritin Meld-Bused P o l i ~ m ~ (rAs d v . Orgonomet. Chcm. 1995, 37. 168); I. Manners. Pho.\phorus Su/fiir Silicon 1994, 93/94. 143-151 I3 1 ~ [?] V, V, Dementrev. F, Cervantes-Lee. L, parkany,, H , Sharma, K , H. pannell, M. T. Nguyen. A. Didz. Orgunotn~ru//ics1993, 12, 1983-1987.  W. Finckh. B:Z. Tang. D. A. Foucher, D. B. Zamble. R. Ziembinski. A. Lough. I. Manners, OrgunomrlciNic.t 1993, 12, 823-829.  C. Angelakos. D. B. Zamble. D. A. Foucher. 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M , Herberhold, Farrociwophunc Cornpounrlt Conriiinin~qI ~ r r r r o i ~ l m n r ninl . ~Fivrocpne.p. Hornopwous Cutcrlwis - O r p n i c Swrhcsi>- Mir/n.iu/.\ S c i e n w (Eds. : .A. Togni. T. Hayashi). VCH, Weinheim. 1995. pp. 219 27X. Woollins, J. D. (ed.) Inorganic Experiments 1994. XV, 286 pages with 86 figures and 8 tables. Hardcover. DM 148.00 ISBN 3-521-29235-1 Renew your inorganic chemistry lab course! This book offers detailed descriptions of more than 60 experiments ranging from undergraduate to graduate level. covering organometallic, main group, solid state and coordination chemistry. Almost all reaction types, laboratory techniques and classes of com- pounds which constitute current curricula are exemplarily represented. Experiments have been contributed from university teachers all over Europe. Each experiment has been thoroughly tested. Special safety instructions are always provided, hazardous substances have been substituted by less harmful ones wherever possible. Products are characterized by modern spectroscopic techniques. Also included are excercises, questions and hints to further reading. The experiments illustrate modern research directions: many compounds have only very recently been described in key journals here you learn how to prepare them in your lab course.