C25

Journnl of Organometailic Chemistry, 153 (1978) C25-C27 0 Ekevier Sequoia Sk, La usauue - Printed in Tbe Netherlands

Preliminarg communication

MARTIN k BENNETT*and TREVOR W. MATHESON

Research School of Chemistry, Australian National University, P-0. Box 4. Canberra 2600 (Australia)

(Received February 24tb, 1978)

Convenient syntheses of arene-olefin complexes of iron(O) and ruthenium(O), e.g. M($-C6Mes)(~4-diene) (M = Fe, Ru, diene = 1,3-cyclohexadiene or 1,5-cyclo- octadiene), Fe($-&Me$)(q”-C,H,) (C7H8 = 1,3,5-cycloheptene) and Ru(v6-C,Me,)(C,H,), are given, and some protonation reactions are described_

Arene-olefin complexes of zerovalent iron and ruthenium are of interest as potential catalysts for olefin oligomerization and for comparison with the well- known tricarbonyl diene complexes of these elements, but few convenient

synthetic routes are available. The l,&cyclohexadiene complexes M(C,H,)(C,H,-) (M = Fe, Ru, OS) [l-3] and the tetiahapfo-hexamethylbenzene komplex Ru(@-C6Mes)(q4-CgMe6) [4] have been known for some time and, more recently, the 1,5-cyclooctadiene complex Ru(C&H,)(C,H,,) has been isolated in poor yield fpom the reaction of [RuCI~(C~H~)]~ with the diene in the presence of isopropyl- Grignard reagent [5]. Other complexes of the type Ru(arene)(CsH,,) are formed by displacement of $3,5-cyclqoctatriene from Ru(1,3,5-C8H10)(C8H12) [6], which is itself readily accessible from the reaction of “RuCI, - 3H,O” with 1,5- cyclooctadiene and zinc dust in ethanol [7].

We have shown [S] that tetrahupto-cyclooctatetraene complexes Ru(arene)- (1-4-q-C8H8) are readily prepared by reaction of cyclooctatetraene dianion with the readily available [RuCl,(arene)], complexes (arene = benzene, mesitylene or hexamethylbenzene) [9-111, and we now report that the latter react with l,&cydooctadiene or 1,3-cyclohexadiene in the presence of ethanol and either base (Na2C03 ) or zinc dust to give yellow, air-sensitive complexes Ru(arene)- (diene) in yields of ca. 60%. The 1,3-cyclohexadiene complex Ru(C6Me6)(C6Hs)* is also isolated from the same reaction using 1,4_cyclohexadiene. The reaction

between [RuCl,(C,Me,)],, cycloheptatriene and sodium carbonate does not give

*Except where stated otherwise, satisfactory elemental analyses and spectroscopic data have been obtained for all new compounds described herein.

I_c26’-.g .:__:_y ‘1:. ._. : :.~. _:_ -.: .- -_ .. _- ;__

.i ; -; __ -_- _.. y

: ..‘~ _

; I.‘-_ -:___:_.__. . . :.

” the ‘&ova&it complex. Ru(&Me~)(l~~-C,Hs ) but its protonation .product ::.: ..: ._ _- .I: [R~(~,M~k)(l_5~~C,H,-)]f;- isolated: as its PFBY_or~BFq_-s< These reactions

r;tii;i?al~ the’~~~s~~nalo~_ib,etwe~~ [Ru_CIz(arene)] z and the isoelectronic penta- c rn~~yi$~~~fn~~~ny~ho~~(~)- complex [RhCl,(q 5-CsMes)], [12-14] _ Reactionbetieen--[RuCl,(CsMe,)],; aqueous ethanolic Na$Os and ethylene gives the’tari; @r-sensitive ruthenium(O) bis(ethylene) complex Ru(C,Me,)(C,H,+)2 (!H.NMR; .CiD6,..320C: 6 (ppm) 1.70 (s, 18H, CsMe6), 1.48 (m, 4H, &I&), 1.04 (m,: 4H; C&l+)] in ci 49% yield- Although the ethylene resonances are

‘broadenedcorisiderably at 116°C in C;F,Br, complete codtiscence is not observed, ixxlititig a higher barrier to ethylene rotation than in the analogous iso- electronic rhodium(I)Icomplexes Rh(C;R,)(C,H+), (R = H; CH, ) [12,15].

-Some related iron(O) complexeshave been obtained by reduction of salts of [Fe(arene),]*+ with cyclooctatetraene dianion CsHs*- or with sodium amalgam iq tetrahydrofuran. Thus, addition of either of these reducing agents to f-Fe(CaMe,),] (PF,), gives a brown-black solution of bis(hexamethylbenzene)-

iron(O), Fe(&Me,), [16] *, which on reaction with cycloheptatiene at 40°C for 16 h, givesthe orange com&?x Fe(CiMe,)(l-4-n-&H,) in 51% yield; Under similar conditions both 1,3- and 1,4cyclohexadiene give the 1,3-c@lohexadiene complex Fe(C,@e6)(C,Hs), and 1,5-cyclooctadiene gives a not fully character&d, the&ally unstable orangered complex which is probably Fe(CBMee)(l,5-CsH12).

The new complexes show the expected reactivity towards electrophiles. Protona~on(HBF4 or HPFs) at the free double bond of Fe(C,Me,)(C,H,) gives the l--5+cycloheptadienyl complex [Fe(CsMe6)(1-5-v-C,H,)‘J+ and addition of Ph,C+ BFi- gives the corresponding trityl-substituted cation [Fe(CBMe,)(l-5-q- C,H&Ph,)]* without abstraction of hydride ion; similar reactions of cyclo- heptatrieneiron tricarbonyl are well known [l&19]_ Protonation (HPF, ) of the 1,8cyclohexadiene complex Ru(C&Ie6)(CsH8) gives a salt which, in the solid state; appears to be the coordinately unsaturated, 16-electron 1-3-77-cycle- hexenyl species [Ru(C,Me,)(l-3-@Z&)]PF6. However, the ‘H NMR spectrum (C&cl,, 32°C: 6 (ppm) 2.30 (s, 18H, &Me&), 2.97 (approx. q, 6H, eazo-CH,), -2.90 (approx. spt, 3H, endo-CHz + RuEI)) indicates that endo-methylene hydrogen atoms migrate rapidly on the NMR time-scale between carbon and ruthenium (eq. 1).

At L80°Cf&esignals at6 2_97and-2-90 ppmhavealmostdisappeared buta. limiting spe&mm could not be reached. This behaviour is entirely analogous to that repc$ed for the isoelectronic complex [ Rh(q ’ -C,H,)( l-3-rl-CsHs)]+ generated by protonation of Rh(CSH5)(C,H8) 1201. Addition of CO gives the

-co_o&inately saturated complex [Ru(C,Me,)(l-3-n-C,Hg)(CO)]+ which&bits the expected ‘II NMR spectrum for a static .r13-allyl complex.

We are currently extending the scope of these preparative routes to other olefins ar@ are investigating electrophilic and nucleophilic reactions of the result- ing complexes.

, -

-During the course of otiaork the preparation of Fe<C$Aes)z by sodium naphthalene reduction of fFe(C,Me6),l<PF,), and the reaction of Fe<C,Meb), with 1.3-cyclohexbiiene were reported independently C171.

C27

Me

Me Me Me Me

Me

-

Hendo

Hexo

Me Me

R’u+ -H

H

H H

(1)

References

7 8

D. Jones. L. Pratt and G. Wilkinson. J. Chem. Sot.. (1962) 4458. E-0. Fischer and J. Miiller. Z. Naturforsch. B. 17 (1962) 774. E-0. Fischer and J. Miiller. Chem. Ber.. 96 (1963) 3217. E-0. Fischer and C. Elschenhroich. Chem. Ber.. 103 (1970) 162. J. Miiller. C-G. Kreiter. B. Mertschenk and S. Schmitt, Chem. Ber., 108 (1975) 2i3. P. Pertici. G.-P. Simonelli, G. VituUi. G. Deganello. P.-L. Sandrini and A. Mantovti. J. Chem. Sot.. Chem. Commua. (1977) 132. P. Pertici. G. Vitulliand L. Porri. J. Chem. Sot.. Chem. Commun.. (1975) 846. M.A. Bennett, T.W. Matheson, G.B. Robertso& A-K. Smith and P.A. Tucker. J. 0rganometa.l. Cbem.. 1210976) C18.

9 G. Winkhaus and H. Singer. 3. OrganometaL Chem.. 7 (1967) 487. 10 R-k Zelonka and M_C. Baird. Canad. J. Chem.. 50 (1972) 3063. 11 M.A. Bennett and AX. Smith, J. Chem. Sot., Dalton Trans., (1974) 233. 12 K. Moseley. J.W. Kangand P.M. Maitlis, J. Chem. Sot. A, <1970> 2875. 13 K. Moseley and PM_ Maitlis. I Chem. Sot_ A. (1970) 2884. 14 H.-B. Lee, K. Moseley. C. White and P.M. Maitlis. J. Chem. Sot.. Dalton Trans.. (1975) 2322. 15 R. Cramer, J.B. Kline and J.D. Roberts. J_ Amer. Chem. Sot., 91<1969) 2519. 16 E-0. Fischer and F- Rchrscheid. 2. Naturforsch. B. 17 (1962) 433. 17 S.R. Weber and H.H. Brintzinger. J. Organometal. Chem.. 127 (1977) 45. 18 H_J. Dauben and D.J. Bertelli, J. Amer. Chem. Sot.. 83 (1961) 497. 19 R Burton. L. Pratt and G. W-on, J. Chem. Sot.. <1961) 594. 20 B.F.G. Johnson, J. Lewis and D.J. Yarrow. J. Cbem. Sot., Dalton TEans.. <X972) 2084_