Polyhe&on Vol. 4, No. II, pp. 1993-1994, 1985 om-5387/85 s3.00+ .oo Printed in Great Britain 0 1985 Pergamon Press Ltd

COMMUNICATION

A 2,3-NAPHTHOQUINODIMETHANE COMPLEX OF RUTHENIUM

WILLIAM FAULKNER, DAVID S. BARRAm, DOMENICO C. CUPERTINO and DAVID J. COLEHAMILTON*

School of Chemistry, University of Liverpool, P.O. Box 147, Liverpool L69 3BX, U.K.

(Received 24 May 1985; accepted 26 May 1985)

Abstract-Treatment of 2,3_dimethylnaphthalene with BuLi * TMED (TMED = tetramethylethylenediamine) gives 2-lithiomethyl-3-methyl-naphthalene - TMED, which in turn reacts with [RuCl,(PMePh,),] to give the 2,3-naphthoquinodimethane complex.

The stabilisation of otherwise unstable organic compounds by coordination to transition elements is an area of particular interest, especially if the organic moiety can be released and undergo subsequent reactions.

A number of reports has recently appearedla on the stabilisation of o-quinodimethane (o-xylylene), which is an important intermediate in the synthesis of a range of organic products.’ Most of these syntheses involve deprotonation2*4 (or oxidation)6 of coordinated hexamethylbenzene complexes or reactions of o-bis(bromomethyl)benzene deriva- tives. ls3 Since these types of precursor are not always readily, available for more complex aromatic systems, complexes of more elaborate analogues of o-quinodimethane have not been prepared.

In contrast, we have reported’ that o- quinodimethane complexes of ruthenium can be obtained directly from o-xylene by deprotonation with BuLi - TMED (TMED = tetramethylethylene- diamine) and reaction of the resulting lithium salt with, for example, [RuCl,(PMe,),]. Since o- dimethylaromatic compounds are often readily available, this reaction should be of more general applicability. We now report the preparation of a 2,3_naphthoquinodimethane complex by this method.

Reaction of 2,3dimethylnaphthalene with BuLi - TMED in light petroleum affords a red oil, presumed to be 1 (see Scheme 1). Reaction ofexcess of

* Author to whom correspondence should be addressed. Present address : Chemistry Department, University of St. Andrews, St. Andrews, Fife KY16 9ST, U.K.

this oil with [RuCI,(PMePh,),] in diethylether affords a red solution from which 2 can be crystallised in 70% yield. Although large crystals of 2 can be obtained, they are soft and do not diffract X- rays, the identification of 2 as the 2,3-naph- thoqinodimethane complex therefore relies on spectroscopic data.

Table 1 shows a comparison of certain features of the ‘H and 31P NMR spectra of 2 and the related q4- o-quinodimethane complex, [Ru(CH,C&H,CH,) (PMePh,),] (3).5 The similarity between the spectra of the two complexes confirms the q4-binding of the 2,3_naphthoqinodimethane complexes, in parti- cular the high field shift of the HA protons is indica-

\ (19 (1)

P = PPh,Me

HB

(2)

Scheme 1. Preparation of 2from 2,3dimethylnaphthalene, BuLi and [RuCl,(PMePh,),]. (i) BuLi, TMED, pet- roleum, 25”C, 6 h. (ii) [RuC12(PMePh2)J, Et,O, 25”C,

48 h.

1993

1994 Communication

Table 1. Selected lH and 31P NMR parameters for 2 and 3 in CD&l,

Chemical shift (ppm)” Coupling constant (Hz)

HA HI% Me(J’d Me(P,) Pfi FB” HAHB H,P H,P P,P,

2 0.73dd 1.74dd 2.16d (7.8Y 1.50 (4.1)d 41.4t 19.5d 4.5 4.5 5.5 4.0 3 0.16dd 1.47dd 2.16d (7.Oy’ 1.53 (4.2)1 35.1s 19.7s 3.8 6.8 5.0 0

@ ‘H relative to tetramethylsilane at 0 ppm. b In C&H,, to high frequency of external 85% H,PO,+. cJ,,. d JeeH -f- JpeW

tive of a butadiene-like coordination5 Further- more, the very low value of J,, rules out the alternative structure involving a five-coordinate complex of a substituted ruthenacyclopentene, but similar low values of Jp,r, have been noted for a range of complexes of the general form [Ru{diene) P,L] (P = PPh,, L = PPhs8 or styrene,g diene = buta-1,3-diene or hexa-1,3-diene; P = L = PMe,- Ph, PMePh,, PMe, or PEt,, diene = o-quinodi- methane5).

The red colour of 2 is somewhat surprising since 18e complexes of ruthenium(0) or (II) are generally yellow, whilst 16e complexes are red.‘9 However, the red colour of 2 arises from an absorption in the visible spectrum at 510 mn (s = 2410), which is close to the position of the major absorption of matrix isolated 2,3-naphthoquinodimethane (541 mn), which is also reported to be red.’ ’

The isolation of this 2,3naphthoqinodimethane complex is somewhat surprising since q4-binding leads to localisation of the bonding in the aromatic sys&zn5 Assuming that this occurs in the naphthoquinodimethane complex, a much larger resonance energy will be lost (resonance energies for benzene and naphthalene are 164 and 315 kJ mol- i, respectively). This demonstrates the very high affinity of ruthenium for diene-like coordination.

Acknowledgements- We thank the SERC for a fellowship (D.S.B.) and studentship (D.C.C.) and Johnson-Matthey Ltd for loans of ruthenium. D.J.C.-H. is the Sir Edward Frankland Fellow of the Royal Society of Chemistry, 19841985.

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REFERENCES

W. R. Roth and J. D. Me&, Tetrahedron L&t. 1967, 2053. M. A. Bennett, I. J. McMshon and T. W. Turney, Angew. Chem., Int. Ed. Engl. 1982,21,379. W. H. Hersh and R. G. Bergman, J. Am. Chem. Sot. 1981,103,6992. J. W. Hull and W. L. Gladfelter, Urganometallics 1982, 1, 1716. S. D. Chappell, D. J. Cole-Hamilton, A. M. R. Galas and M. B. Hursthouse, J. Chem Sot., Dalton Trans. 1982,1867. D. Astruc, private communication. W. Oppoltxer, Angew. Chem.,Znt. EdEngl. 1977,16,10 and references therein. D. J. Cole-Hamilton and 6. Wilkiou, Now. J. Chim. 1977,1,141. B. N. Chandret, D. J. Cole-Hamilton and G. Wilkinson, J. Chem. Sot., Dalton Trans. 1979,1739. B. N. Chat&ret, D. J. Cole-Hamilton, R. S. Nohr and G. Wilkinson, J. Chem. Sot., Dalton Trans. 1977,1546. M. Gisin and J. Wirz, Helu. Chim. Acta 1976,59,2273.