J. CHEM. SOC. DALTON TRANS. 1994 393Cyclohexadiene and Benzene Derivatives of [ Ru,C(CO),,]tDario Braga,**e Piera Sabatino,B Paul J. Dyson,b Alexander J. Blakeb andBrian F. G. Johnson*,ba Dipartimento di Chimica 'G. Ciarnician: Universita di Bologna, Via Selmi 2, 40726 Bologna, ItalyDepartment of Chemistry, The University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, UKThe reaction of [Ru,C(CO),,] 1 with cyclohexa-l,3-diene and three equivalents of Me,NO yielded thenew compound [Ru,C(CO),,(~~-C,H,)~] 2 and also [Ru,C(CO),,(p,-qZ:q2:q2-C6H,)] 3 and [Flu,-C(CO),,(q6-C6H6)] 4 in approximately equal yields. The molecular structure of 2 has been established bysingle-crystal X-ray diffraction. The two cyclohexadiene ligands are terminally bound on oppositebasal ruthenium atoms of the square-pyramidal metal framework.Compound 2 may be converted to 3 byreaction with carbon monoxide. The isomeric pair [R~,C(C0),,(p,-q~:q~: q2-C,H6) (p-q2: q2-C,H,)] 5and [Ru,C(CO),,(q6-C6H,) (p-qz:q2-C6H8)] 6 may be prepared from 3 and 4, respectively, upon reactionwith cyclohexa-1.3-diene and two equivalents of Me,NO. Clusters 5 and 6 have also been studied bysingle-crystal X-ray diffraction. In both molecules the cyclohexadiene ligand bridges a basal edge of thesquare pyramid, while the benzene fragment is in face-capping and terminal bonding mode, respectively.The octahedral [Ru,C(CO) ,] and the square-pyramidal[Ru,C(CO),,] clusters have proved to be ideal startingcompounds in the preparation of arene-bound clusters.Theinterstitial carbido atom tends to confer stability to the clusterframework, so that the metal core remains intact duringreaction.In the case of the hexaruthenium system,' a wide variety ofboth mono- and bis-(arene) derivatives have been preparedand characterized, as well as a number of stable cyclohexadieneintermediates produced on route to these corn pound^.^.^ For[Ru,C(CO), 5 ] both 1,3- and 1 ,Ccyclohexadiene intermediatecompounds have been ~bserved.~,~ These may be readilyconverted to the appropriate benzene products. However, anadditional feature of this system is the ability of the centralcluster unit to undergo rearrangement by edge-cleavage to abridged-butterfly species on reaction with certain nucleophilicreagents. Consequent removal of the nucleophilic source re-sults in regeneration of the square-pyramidal cluster unit.Thishas been documented for the reaction [Ru,C(CO),,(q6-to be an important step in many of the mechanisms involvedin this chemistry.In this paper we report studies of the reactions of thispentaruthenium cluster with Me3N0 in the presence ofcyclohexa- 1,3-diene to form both cyclohexa-l,3-diene andbenzene derivatives. It would appear that the formation of thebenzene compounds, which occur via the intermediacy of acyclohexadienyl compound, may occur via a rearrangementprocess of the type described above.C,H,)] [RU,C(C0),3(q6-C,H,)],5 but iS ah0 believedResults and DiscussionThe reactions outlined herein are illustrated in Scheme 1. Thedropwise addition of a solution of three molar equivalentsof Me,NO in dichloromethane to a solution of the square-pyramidal cluster [Ru,C(CO), ,] 1 also in dichloromethanecontaining a large excess of cyclohexa-l,3-diene afforded threeproducts in approximately equal yields.Isolation was achievedby column chromatography on silica gel, eluting withdichloromethane*thyl acetate-hexane (10: 5 : 85, v/v). In orderi Supplementury data available: see Instructions for Authors, J. Chem.Soc., Dalton Trans., 1994, Issue 1 , pp. xxiii-xxviii.4$b 1v 2 3 45 6Scheme 1 (i) Me,NO (3 mol equivalents) added dropwise to aCH,Cl,+yclohexa-l .3-diene solution; (ii) CO bubbled through aCH,Cl, solution; (iii) refluxing hexane for 4 h; (iu) Me,NO (2mol equivalents) added dropwise to a CH,Cl,-cyclohexa- 1,3-dienesolution; (v) refluxing toluene for 8 hofelution the products have been identified as [Ru,C(CO), l(q4-(CO)12(r(6-CgH6)] 4. While compounds 3 and 4 have beenreported previ~usly,~ the bis(q4-diene) cluster is new and hasbeen characterized by both spectroscopic and single-crystalX-ray diffraction analyses.The mass spectrum of compound 2is easily interpreted. A parent peak is observed at m/z 986(calculated 986) followed by the strongest peak in the spectrum,m/z ca. 906, corresponding to the loss of one cyclohexadienering. Thereafter, eleven carbonyl groups are lost in succession.The 'H NMR spectrum of compound 2 in CDCl, is somewhatmore complicated. At room temperature (296 K) three broadsignals are observed, centred at approximately 6 5.9, 3.5 and2.2, with relative intensities 1 : 1 : 2, respectively. The chemicalshift of the first two signals may be attributed to the olefinicprotons of the diene, while the signal at 6 2.2 is consistent withthe aliphatic cyclohexa- 1,3-diene protons.On cooling to 2 12 K,C,H,),] 2, [Ru5C(CO)1,(p3-q2 q2 : 'l12-C,H,)] 3 and [RUsC394 J. CHEM. SOC. DALTON TRANS. 1994O(11)Fig. 1 Solid-state molecular structure of compound 2Table 1 Relevant bond distances (A) and angles (“) for compound 2Ru( l)-Ru(2)Ru( l)-Ru(3)Ru(~)-Ru( 3)Ru(2)-Ru(4)Ru(3gRu(4)Ru( 1 )-C( 12)Ru(2)-C( 12)Ru(2)-C(2 1)Ru(3)-C-(21)Ru( 1)-CRu(2)-CRu(3)-C2.785( 1)2.8U( 1)2.785( 1)2.897( 1)2.760( 1)2.10(1)2.01(1)2.05(1)2.12( 1)1.99(1)2.06(1)2.17(1)1.97( 1)2.21(1)2.27( 1)2.19(1)2.17(1)1.55(2)1.41(1)1.55( 1)1.42( 1)1.54(1)l.U( 1)Ru( 1 t C ( 1 2)-Ru( 2) 85.1(3) Ru( I)-C-Ru(4) 169.2(4)Ru(2)-C(21)-Ru(3) 83.8(3) Ru( 2)-C-R U( 4) 91.8(3)Ru( 1 tC-Ru(2) 86.7(3)eight signals of equal relative intensity at 6 6.41,5.38,4.45,2.87,2.79, 2.08, 1.97 and 1.55 are observed, while on warming to329 K four multiplets (at 6 5.97, 3.72, 2.31 and 1.99), also ofequal relative intensity, emerge.For both the low and hightemperature spectra, the first half of the signals corresponds toolefinic protons, and the remaining signals to the aliphaticprotons. Variation of the width and number of the signals withtemperature suggest some fluxionality, and in this case it wouldappear that coalescence occurs at 296 K.While the precisefluxional processes taking place cannot be identified, the signalsobtained at 212 K probably correspond to the eight chemicallyinequivalent protons of the dienes, while at 329 K there is aplane of symmetry bisecting each diene moiety; hence, fourchemically equivalent proton pairs, illustrated by the foursignals seems most likely. At 296 K rapid rotation and flippingof the cyclohexadiene ligands can be speculated.The molecular structure of compound 2 in the solid state isdepicted in Fig. 1. A crystallographic mirror plane bisects themolecule passing through the apical and two opposite basalruthenium atoms. Relevant structural parameters are listed inTable 1 .In the family of benzene and cyclohexadiene deriv-atives of [Ru,C(CO), ’1, compound 2 possesses some uniquestructural features. Although the metal framework is thefamiliar square pyramid of [Ru,C(CO), bearing a C(carbido)atom almost in the middle of the square base, the liganddistribution is uncommon. First, the cyclohexadiene ligands arebound in termal fashion (q4-bonding mode) on two oppositecorners of the square base, secondly a complex pattern of CObridges is observed. In [Ru~C(CO)~~] and most of its deriv-atives the CO ligands are usually found to adopt only terminalco-ordination. In 2, two bridging CO ligands span two con-secutive edges of the square base, while two others span twobase-apex edges of the pyramid. In such a way, two rutheniumatoms bear two terminal CO and are involved in two bridginginteractions, one basal ruthenium atom carries only threeterminal ligands {as in [Ru,C(CO), ,I}, while the remainingtwo basal ruthenium atoms involved in the interaction with thecyclohexadienes bear only two CO.This ‘geometrically uneven’ligand distribution, however, achieves (at least formally) ahomogeneous ligand-to-metal electron distribution with eachruthenium atom formally receiving 6 electrons from the ligands.The Ru-Ru bond lengths range from 2.760( 1) to 2.897( 1) A, theCO-bridge bonds show an intermediate length [2.786(1) A],while the shortest bond is the base-apex Ru(3)-Ru(4) distance[2.760( 1) A]. The C(carbide) atom shows lon er distances fromthe substituted ruthenium atom [2.062(7) 11 than from theunsubstituted one [1.995(7) A].The CO bridges show other-wise shorter bonds from Ru(2) than from the unsubstitutedatoms.Perhaps the simplest mechanistic pathway to compound 2may be taken to involve the systematic removal of co-ordinatedCO (by oxidation to CO,) which is then followed by additionof the diene to the vacant co-ordination sites to produce[Ru,C(CO), $q4-c6H8)], as yet unobserved. This can theneither isomerize to [Ru,C(CO), 3(p-q2 : q2-C6H6)], the pre-cursor to 3 (and ultimately 4), also obtained in this reaction, orreact with further Me,NO. This process must then occur againto form [Ru,C(CO), 1(q4-C6H8),] 2, which is transformedinto 3 in good yield upon reaction with CO. In this reactionone diene must be displaced, one CO added, and ‘dehydro-genation’ of the remaining cyclohexa-l,3-diene to a benzenemust also occur.There are two possible mechanisms by whichthe displacement of the q4-C6H8 may occur. First, andmost obviously, direct displacement; a reaction in which theq4-bonded diene moves to an q2-co-ordinated mode andeventually displacement by further CO. Secondly, and themechanism we prefer, a reaction sequence of the type previouslyobserved’ for the reaction of [RU,C(CO),~(~~-C,H~)] 4 withCO, in which a square-pyramidal bridged-butterfly rearrange-ment of the cluster core occurs. In this process, addition ofCO occurs at one of the basal ruthenium atoms of thJ. CHEM. SOC. DALTON TRANS. 1994 395[Ru,C(CO), 1(q4-C6H8)2] unit to generate a bridged-butterflyarrangement of metal atoms followed by reclosure to thesquare-pyramidal structure with the ejection of one of the q4-C6H, ligands.From here, the method by which 3 forms shouldparallel that described for its formation from [RU~C(CO)~,-(p-q' : q2-C6H8)] on reaction with Me,NO.Extending the synthetic sequence described originally forthe preparation of the benzene clusters 3 and 4 from[Ru,C(CO),,],~ 3 and 4 have been treated with two molarequivalents of Me,NO in dichloromethane in the presence ofcyclohexane- 1,3-diene yielding a pair of benzene-diene clusters[Ru5C(CO),o(p3-q2: q2 q2-C6H6)(ji-q2: q2-C6H8)] 5 and[Ru5C(CO),,(q6-C6H6)(p-q2 : q2-c6H8)] 6, respectively. For-mulation of 5 and 6 was initially based upon mass and 'H NMRspectra.Both clusters exhibit strong parent peaks at m/z 956(calculated 956) together with the loss of ten CO groups. The'H NMR spectrum of 5 is simpler than that of 6 due to greatersymmetry within the molecule. In 5 and 6 singlets at 6 4.14 and5.85 can be assigned to the face-capping and q6-terminalbenzene ligands, in the respective compounds. In compound 5the diene gives rise to four signals of relative intensity 1 : 1 : 1 : 1.The signals at 6 5.57 and 4.57 are consistent with the olefinicprotons of the diene, while those at 6 2.84 and 2.03 arise fromthe aliphatic protons of the diene ring. The asymmetry inmolecule 6 gives rise to eight signals of equal relative intensityat 6 5.33, 5.07, 4.43, 4.09, 2.60, 2.55, 1.72 and 1.69, once againfour corresponding to the olefinic and four to the aliphaticprotons of the diene.Selectively decoupling each signal hasallowed for their unambiguous assignment. The spectra areshown in Fig. 2 together with a sketch illustrating the assignmentof the protons (HA-HH) in the cyclohexa-l,3-diene moiety.The solid-state molecular structures of the isomers 5 and 6are closely related and will be discussed together. Figs. 3 and 4show sketches of the two molecular structures and the labellingschemes. Relevant bond distances and angles are reported inTable 2 for 5 and 6, respectively. The structures of 5 and 6 differessentially in the mode of co-ordination of the benzene ligand.In 5 this ligand caps the square-pyramid triangular faceopposite to the Ru-Ru bond carrying the p-q2 :q2-cyclohexa-diene ligand, while in 6 the benzene ligand is terminally bound(q6-co-ordination mode) to one basal ruthenium atom.Thesebonding modes have already been observed in the otherisomeric pairs characterized so far, namely [Ru,C(CO), 2(p3-hexanuclear octahedral clusters [Ru,C(CO), l(q6-C&,)2] andpound 2, no bridging CO ligands are present in 5 and 6, while inboth molecules the cyclohexadiene ligand spans one basal edgetaking the place of two radial CO ligands with respect to theq2 :q2 :q2-c6H6)] and [RU5C(CO),2(q6-C6H6)] and the[RU6C(CO), 1(p3-q2 q2 q2-C6H6)(?16-C6H6)].3 Unlike COm-$QHE HA HFHH..i5.4 5.0 4.6 4.2 3.8 3.4 3.0 2.6 2.2 1.86Fig. 2 The 'H NMR decoupling spectra for compound 6 recorded at 212 K.Signals are labelled A-H and their assignment shown. The arrowsindicate the sites of irradiation and the resonances marked * and i indicate affected sites and impurities, respectivel396 J. CHEM. SOC. DALTON TRANS. 1994Fig. 3 Solid-state molecular structure of compound 5(7 VWO(41)Fig. 4 Solid-state molecular structure of compound 6parent [Ru,C(CO), J. Metal-metal bonds range from 2.804( 1)to 2.881(1) in 5 and from 2.744(1) to 2.855(1) A in 6. Thebenzene ligand in 6 is disordered over two sites with siteoccupation factors in the ratio 7 : 3. This disorder is, very likely,dynamic in nature. It has been demonstrated in many crystal-line arene complexes and clusters that a disc-like benzene ligandbound in delocalized manner to one (or more) metal centrescannot be easily locked in place by the surrounding molecules.6The barrier to reorientation is usually fairly small (less than50 kJ mol-').An estimate of the reorientational barrier forjumps of the benzene atoms can be obtained by means of theatom-atom potential energy method.6 In 6 the potential-energyprofile presents the expected sinusoidal shape with minimaevery 60" separated by rather low potential-energy barriers(maximum ca. 6 kJ mol-'). Intermediate minima correspondingto the alternative orientation are not detected probably becauseof the low sensitivity of the computational method in thepresence of very low reorientational barriers. Finally, it isinteresting to relate the disorder observed in crystalline 6 to thepresence of two independent molecules in the asymmetric unitof [Ru,C(CO),~(~~-C~H~)] 4.In this latter case, the twomolecules differ essentially in the rotameric orientation of theterminally-bound benzene ligands.In contrast to previous observations in which the faciallybound benzene ring in 3 migrates to a q6-co-ordination modewith relative ease, and nearly quantitatively, the correspondingisomerization process from 5 to 6 requires high temperaturesand is accompanied by extensive decomposition. Attempts tJ. CHEM. SOC. DALTON TRANS. 1994 397Table 2 Comparison of relevant bond distances (A) for compounds 5 and 6Ru( l)-Ru(3)Ru( l)-Ru(4)Ru( 1)-Ru(5)Ru(2)-Ru(3)R U( 2)-Ru(4)Ru(2)-Ru( 5 )Ru(3)-Ru(5)Ru( I)-CRu(2)-CRu(3)-CRu(4)-CRu(5)-CC( 18)-C( 19)C( 19)-C(20)Ru(4)-Ru( 5)C(2O>-C(21)C(21)-C(22)C(22)-C(23)C( 18)-C(23)5 62.804( 1)2.8 17( 1)2.88 1 (1)2.829( 1)2.872(1)2.866(1)2.852( 1)2.837(1)1.984(3)2.004(3)2.004( 3)2.0 14( 3)2.083(3)1.46(1)1.46( 1)1.43( I )1.32( 1)1.36(1)1.35(1)2.838( 1)2.799( 1)2.827( 1)2.849( 1)2.775(1)2.855( 1)2.744( 1)2.842( 1 )1.896( 1)2.02(1)2.06( 1)2.00( 1)2.15(1)Ru( 1)-C( 13)Ru( 1 )-C( 14)Ru(3)-C( 12)Ru(3)-C( 17)Ru(2)-C( 19)Ru(2)-C(20)Ru(4)-C(21)Ru(4)-C( 2 2)Ru( 5)-C( 18)Ru( 5)-C(23)C( 12)-C( 13)C(13)-C(14)C( 14)-C( 1 5 )C( 1 5)-C( 16)C( 16>-C( 17)C( 12)-C( 17)52.289(4)2.3 17( 3)2.254(4)2.285(4)2.383(5)2.2 1 6(4)2.3 18(5)2.233(5)2.210(4)2.395(5)1.45( 1)1.38( 1)1.49( 1)1.47( 1)1.52( 1)1.39( 1)Ru( 2)-C( 2D)Ru(2)-C( 3D)Ru(4)-C( 1 D)Ru(4)-C(6D)Ru( 1)-C( 1 B)Ru( 1)-C(2B)Ru( 1)-C(3B)Ru( 1)-C(4B)Ru(l)-C(SB)Ru( 1)-C(6B)C(2D)-C(3D)C( 3D)-C(4D)C(4D)-C(5D)C( 1 D)-C(6D)C( 1 D)-C(2D)C( 5D)-C(6D)62.30( 1)2.30(1)2.27( 1 )2.3 1( 1)2.22(1)2.21( 1 )2.20(1)2.22( 1)2.22( 1)2.19( 1)1.45(2)1.40(2)1.49(2)1.54(2)1.52(2)1.38(2)prepare bis(benzene) adducts from clusters 5 and 6 have alsoproved unsuccessful, with decomposition occurring and onlysmall amounts of starting material being recovered.ExperimentalAll reactions were carried out with the exclusion of air usingfreshly distilled solvents under a nitrogen atmosphere.Sub-sequent work-up of products was achieved with standardlaboratory-grade solvents without precautions to exclude air.Infrared spectra were recorded on a Perkin Elmer 1600 seriesFTIR spectrometer in CH,Cl, using NaCl cells. Positive fast-atom-bombardment mass spectra were obtained using a KratosMS5OTC spectrometer, with CsI as calibrant. Proton NMRspectra were recorded in CDCI, using a Bruker AM360instrument, referenced to internal SiMe,. Thin-layer chromato-graphy (TLC) was carried out on plates supplied by Merckcoated with a 0.25 mm layer of Kieselgel 60F254. The[Ru,C(CO), 5] cluster was prepared according to the literatureprocedure.' Cyclohexa- 1,3-diene was purchased from Aldrichand used without further purification.Trimethylamine N-oxide(Me,NO) was sublimed prior to use.Reaction of [Ru,C(CO),,] 1 with Cyclohexa-l,3-diene andTrimethylamine N-Oxide.-Synthesis of compounds 2-4. Com-pound 1 (500 mg) was dissolved in dichloromethane (50 cm3),and cyclohexa-1,3-diene (2 cm3), and the solution cooled to- 78 OC. A solution of Me,NO (124 mg, 3.1 mol equivalent) indichloromethane (1 5 cm3) was added dropwise over a period of5 min. The mixture was stirred for a further 30 min while thesolution was brought to room temperature. IR spectroscopyindicated complete consumption of the starting material. Thesolvent was removed in uacuo and the residue separated bycolumn chromatography on silica (60 mesh) using a solution ofethyl acetate-dichloromethane-hexane (5 : 10: 85, v/v) as eluent.Three products were obtained and characterised spectro-(Found: C, 29.15;H, 1.70.Calc.fOrC2,H16011Ru5: C,29.25;H,[Ru,C(CO),,(q6-C6H6)] 4 (black, 67 mg) in order of elution.Spectroscopic data for 2. IR (CH,Cl,): v(C0) 2058w, 2039vs, 2015s, 1981m and 1846m cm-'. 'H NMR (CDCI,, 212 K):6 6.41 (m, 1 H), 5.38 (m, 1 H), 4.45 (m, 1 H), 2.87 (m, 1 H), 2.79(m, 1 H), 2.08 (m, 1 H), 1.97 (m, 1 H) and 1.55 (m, 1 H) (all signalsare broad at room temperature). Mass spectrum: m/z 986( M ') (calc. 986).SCOpiCally as [Ru5C(CO)1 1(q4-C6H8)2] 2 (black, 78 mg)1.60%), [ R U ~ C ( C O ) ~ ~ ( P ~ - T ~ ~ q2 : q2-C6H6)] 3 (red, 84 mg) andSpectroscopic details for compounds 3 and 4 are in goodagreement with those reported previously.Reaction of [Ru5C(CO), l(q4-c6H8)2] 2 with c 0 .-Compound 2 (10 mg) was dissolved in dichloromethane (20cm3) and CO was slowly passed through the solution for 10min. The reaction vessel was sealed under the CO atmosphereand stored at -20 "C for 18 h. The solution changed fromblack to dark red during this period. Removal of the solvent inuacuo, followed by TLC using a solution of dichloromethane-hexane (30 : 70) as eluent resulted in the isolation of a major redproduct characterized spectroscopically as [Ru,C(CO), &,-q2:7]2:r]2-C6H6)] 3 (7 mg).Reaction of [Ru5C(CO)12(p3-q2 : q2 : q2-c6H6)] 3 with CyCbhexa-l,3-diene.-Synthesis of compound5. Compound 3 (30 mg)was dissolved in dichloromethane (20 cm'), and cyclohexa- 1,3-diene (1 cm3), and the solution cooled to - 78 "C.A solution ofMe,NO (5 mg, 2.1 mol equivalent) in dichloromethane (5 cm3)was added dropwise over a period of 5 min. The mixture wasstirred for an additional 25 min while the solution was broughtto room temperature. IR spectroscopy indicated completeconsumption of the starting material. The solvent was removedin V ~ C U O and the residue separated by TLC using a solution ofethyl acetatedichloromethane-hexane ( 5 : 10 : 85) as eluent.The major orange band was extracted and characterizedmg). IR (CH2C12): v(C0) 2046w, 2020s, 1988s and I942w cm-' .'H NMR (CDCl,): 6 5.57 (m, 2 H), 4.57 (m, 2 H), 4.14 (s, 6 H),2.84 (m, 2 H) and 2.03 (m, 2 H). Mass spectrum: mjz 956 ( M +)(calc. 956).as [Ru,C(CO),o(p3-q2: q2 :172-C6H&-772 :r]'-C,H,)] 5 (13Reaction of [Ru5C(CO),,(q6-C6H6)] 4 with Cyclohexa-1,3-diene.-Synthesis of compound 6 .A solution of compound 4(50 mg) in dichloromethane (25 cm3) and cyclohexa-l,3-diene(15 cm3) was cooled to -78 OC. A solution of Me,NO(8 mg, 2.1 mol equivalent) in dichloromethane (5 cm3) wasadded dropwise. The solution was warmed slowly to roomtemperature over 30 min. IR spectroscopy indicated completeconsumption of the starting material. The solvent was removedin uacuo and the products extracted by TLC eluting withhexane-dichloromethane (70 : 30). The major black band wasextracted and characterized as [Ru,C(CO) , o(q 6-c6H6)(P-and 1985w(br) cm-'. 'H NMR (CDCl,): 6 5.85 (s, 6 H), 5.33(m, 1 H), 5.07 (m, 1 H), 4.43 (m, 1 H), 4.09 (m, 1 H), 2.60 (m, 1l12:q2-C6H8)] 6 (17 mg).IR (CHZCl,): v(c0) 2052m, 1997398 J. CHEM. soc. DALTON TRANS. 1994Table 3 Crystal data and details of measurements for compounds 2 , 5 and 62Formula C*,H1,O11RusA4 985.7TIK 150Crystal size/mmCrystal system OrthorhombicSpace group Pnma0.16 x 0.19 x 0.19alA 13.355(3)blAC I Aai"Pi"rl"1 3.996( 3)14.593(3)u p 2727( 1)z 4F(000) 1696h(Mo-Ka)/A 0.710 73p(Mo-Ka)/cm-' 26.80 Range/" 2.5-22.5Measured reflections 2700Unique observed reflections [lo > 20(Zo)] 1667Hi hest peak in final difference synthesis 1.3Goodness of fit on F2R, wR'R," wR',"~~ goodness of fit on FaOctants explored (hkl) - 14 to 14,615, 6 1 5No. of refined parameters 2021 - 30.035, 0.043, 1.29" Refinement on F, with SHELX 76.8b Weighting scheme: w-l = 0 2 ( F ) + 0.0004 P5955.72930.25 x 0.15 x 0.35TriclinicPT9.68 7 (7)16.474(4)9.036(1)92.68(2)116.01(3)78.95(4)1270(1)29040.710 6929.6C23H1 Ci01ORuS2.5-25-11 to 11, -19t0 19,610478338573440.56c2 3H 1 do 1 ORuS955.71500.23 x 0.27 x 0.51Monoclinic13.724(3)12.086(3)15.457(2)p2 1 lc95.77(2)2551( 1)418080.710 7328.72.5-22.5- 14 to 14,O-13,0-16353229442241.41.060.021, 0.0640.054,0.057, 0.97Table 4 Fractional atomic coordinates of compound 2 with estimatedstandard deviations (e.s.d.s) in parenthesesX0.175 89(6)0.267 43(4)0.370 35(6)0.356 49(6)0.257 2(6)0.053 9(8)0.175 6(6)0.136 O(4)0.145 2(10)0.127 6(8)0.380 2(6)0.428 4(5)0.370 3(8)0.372 9(7)0.497 8(7)0.576 7(6)0.284 6(9)0.237 9(7)0.439 l(6)0.485 4(5)0.270 O(7)0.171 7(7)0.317 O(7)0.169 9(6),0.014 2(5)0.11 1 7(7)Y0.250.395 77(5)0.250.250.250.250.250.399 9(7)0.454 9(4)0.250.250.401 O(6)0.456 9(5)0.250.250.250.250.250.250.348 8(9)0.412 6(7)0.556 l(7)0.598 O(7)0.530 O(7)0.538 8(7)0.461 4(6)Z0.051 58(5)0.037 44(6)- 0.049 27(4)- 0.168 65(6)-0.068 5(7)- 0.000 6(9)- 0.038 4(8)0.063 3(6)0.1 17 8(4)0.193 2(9)0.275 8(7)0.042 2(6)0.079 O(6)0.18 1 6(8)0.265 l(6)0.014 2(8)- 0.000 2(7)-0.288 5(8)- 0.356 6(6)- 0.206 8(6)- 0.229 8(5)-0.025 O(10)-0.031 7(10)-0.1 13 3(7)-0.104 l(8)- 0.155 6(7)H), 1.72 (m, 1 H) and 1.69 (m, 1 H).Mass spectrum: m/z 956( M + ) (calc. 956).~ h a W Z O ~ ~ S i S O~[RU,C(CO),&~-V~~ : V12 : ?2-C6H6)(p-?2: q2-C6H,)] 5.-Compound 5 (8 mg) in toluene (20 cm3) was heatedto reflux for 8 h. During this period the reaction mixture wasmonitored by IR spectroscopy, which indicated a dramaticchange from the starting material. The toluene was removed inuucuo and the products extracted by TLC eluting with hexane-dichloromethane (70: 30). A single product was isolated andTable 5 Fractional atomic coordinates of compound 5 with e.s.d.sX0.309 81(3)0.218 59(3)0.067 79(3)0.278 97(3)0.427 4(5)0.495 7(4)0.198 5(5)0.123 2(5)-0.101 7(5)-0.034 29(3)-0.205 9(5)- 0.306 8(4)- 0.147 2(4)0.070 5(5)0.223 4(5)0.227 l(5)-0.101 9(5)0.147 6(5)0.190 5(5)0.469 2(5)0.587 3(4)0.384 7(5)0.452 9(4)0.137 O(4)0.470 2(4)0.519 4(4)0.488 9(4)0.429 5(4)0.357 9(7)0.383 O(5)0.160 4(8)0.012 3(11)-0.021 8(4)-0.204 l(5)-0.115 8(6)-0.085 8(7)0.051 l(8)0.174 7(7)Y0.736 03(2)0.770 79(2)0.849 63(2)0.650 83(2)0.677 lO(2)0.643 4(3)0.588 6(2)0.779 O(3)0.803 6(3)0.824 O(3)0.856 5(2)0.843 5(2)0.890 7(2)0.938 9(3)0.991 8(2)0.900 7(3)0.932 O(2)0.684 8(3)0.706 6(3)0.566 7(3)0.517 9(2)0.612 2(3)0.573 l(2)0.716 8(3)0.736 8(2)0.753 l(2)0.854 7(3)0.793 9(2)0.8 13 6(2)0.900 5(2)0.960 O(3)0.932 O(2)0.601 2(5)0.658 6(3)0.656 7(3)0.600 2(3)0.549 8(3)0.553 2(3)Z0.069 67(3)-0.377 31(3)-0.193 12(3)-0.121 86(4)-0.246 57(3)0.222 8(5)0.313 6(5)0.189 9(5)0.254 8(5)- 0.352 4(5)-0.323 3(5)- 0.574 2(5)- 0.682 6(4)- 0.184 3(5)- 0.179 5(5)-0.377 l(5)- 0.482 9(4)- 0.070 6(6)-0.038 8(6)0.046 3(5)0.151 5(5)-0.01 1 7(4)- 0.098 2(5)-0.354 4(5)-0.417 6(4)- 0.156 8(4)- 0.024 3(5)0.108 6(5)0.242 9(4)0.269 2(4)0.127 6(6)-0.023 5(5)-0.455 9(9)-0.546 l(6)-0.503 3(7)-0.372 3(7)- 0.299 O(6)- 0.330 7(7J.CHEM. SOC. DALTON TRANS. 1994 399Table 6 Fractional atomic coordinates of compound 6 with (e.s.d.s) inX0.247 47(7)0.302 52(7)0.391 88(7)0.152 22(7)0.197 71(7)0.278 l(8)0.371 2(10)0.41 1 O(7)0.391 9(9)0.442 5(7)0.470 2( 1 1)0.517 9(8)0.396 l(10)0.397 2(7)0.499 3(11)0.559 6(8)0.188 l(10)0.214 8(8)0.030 6( 1 1)0.071 6(10)0.250 7(10)0.281 3(7)0.167 7(10)0.147 8(7)0.253 7(18)0.336 5(18)0.326 2( 18)0.233 O(18)0.150 2(18)0.160 5(18)0.202 O(40)0.140 O(40)0.180 O(40)0.282 O(40)0.343 O(40)0.303 O(40)0.091 6(10)0.165 O(10)0.240 5(10)0.230 l(11)0.181 6(10)- 0.040 3(8)- 0.007 4(7)Y0.128 22(8)0.065 76(8)0.049 61(8)- 0.147 28(8)-0.075 75(8)- 0.007 2( 10)-0.181 3(11)-0.205 l(8)-0.210 7(10)- 0.244 4(9)0.030 2(12)0.009 6(9)0.219 8(12)0.312 2(7)0.049 7( 12)0.040 8(9)-0.108 3(12)- 0.127 9(9)- 0.008 2( 12)0.038 9(10)0.001 l(12)- 0.028 4(9)0.023 3(12)0.011 l(8)0.201 3(12)0.294 6(7)0.145 9(10)0.195 5(10)0.276 4(10)0.307 6(10)0.258 O(10)0.177 l(10)0.158 3(23)0.223 l(23)0.298 8(23)0.309 7(23)0.244 9(23)0.169 2(23)-0.224 l(11)- 0.250 O( 12)-0.323 7(11)- 0.393 9( 12)-0.337 7(12)70.378 70(7)0.260 1 l(7)0.268 93(7)0.353 85(7)0.207 67(6)0.325 7(8)0.162 6(8)0.103 3(6)0.346 O(6)0.402 2(7)0.178 l(10)0.122 9(8)0.247 5(9)0.231 6(7)0.358 O(9)0.412 4(9)0.468 6(9)0.541 4(6)0.370 8(9)0.383 5(9)0.172 4(9)0.143 9(8)0.034 9(6)0.201 2(8)0.191 4(6)0.522 l(7)0.493 6(7)0.429 O(7)0.392 7(7)0.421 2(7)0.485 8(7)0.509 2(21)0.452 3(21)0.397 6(21)0.399 9(2 1)0.456 8(21)0.51 1 4(21)0.276 O(9)0.21 7 9(9)0.245 l(8)0.323 2(9)0.397 2(9)0.101 O(10)Primed atoms are those of the minor image of the benzene ligand.characterised spectroscopically as [RU,C(CO),o(r76-CsH6)(CL-q2: q2-C,H,)] 6 ( > 1 mg).Crystal Structure Determination of Compounds 2, 5 and 6.-Crystal data and details of measurements for compounds 2, 5and 6 are summarized in Table 3 .Diffraction intensities werecollected by the 03-20 scan method, at 150 K for 2 and 6 and atroom temperature for 5, on an Enraf-Nonius CAD-4 or aStadi-4 diffractometer equipped with Mo-Ka radiation. Thestructures were solved by direct methods and refined by full-matrix least squares. For all calculations the crystallographicprograms SHELX 86,8u, SHELX 76 8b and SHELXL 92 8c wereused. Anisotropic thermal parameters were applied to all non-Hatoms of 2 and 5 and to all Ru and 0 atoms of 6.In this lattercompound, the occupancy factor for the major image of thedisordered benzene ring, upon refinement, converged to0.69(3). In all species hydrogen atoms were added in calculatedpositions and refined ‘riding’ on the corresponding C atoms. Inall compounds single isotropic parameters for the aromatic,methylenic and methylic H groups were refined. Fractionalatomic coordinates of 2, 5 and 6 are reported in Tables 4-6,respectively .Additional material available from the Cambridge Crystallo-graphic Data Centre comprises H-atom coordinates, thermalparameters and remaining bond lengths and angles.AcknowledgementsFinancial support by the Minister0 dell’universita’ e dellaRicerca Scientifica e Tecnologica is acknowledged. B. F. G. J.and D. B. thank NATO for a travel grant and P. J. D. the SERCand British Petroleum for financial support.References1 D. Braga, F. Grepioni, S. Righi, P. J. Dyson, B. F. G. Johnson,P. Bailey and J. Lewis, Organometallics, 1992, 11,4042.2 P. J. Dyson, B. F. G. Johnson, J. Lewis, D. Braga andP. Sabatino, J. Chem. Soc., Chem. Commun., 1993,301.3 P. J. Dyson, B. F. G. Johnson, J. Lewis, M. Martinelli, D. Bragaand F. Grepioni, J. Am. Chem. Soc., 1993,115,9602.4 P. J. Dyson, B. F. G. Johnson, D. Reed, D. Braga, F. Grepioniand E. Parisini, J. Chem. Soc., Dalton Trans., 1993, 2817.5 D. Braga, F. Grepioni, P. Sabatino, P. J. Dyson, B. F. G. Johnson,J. Lewis, P. J. Bailey, P. R. Raithby and D. Stalke, J. Chem. Soc.,Dalton Trans., 1993,985.6 D. Braga, F. Grepioni, B. F. G. Johnson, J. Lewis and M. Martinelli,J. Chem. Soc., Dalton Trans., 1990,1847; D. Braga, Chem. Rev., 1992,92, 633.7 B. F. G. Johnson, J. Lewis, J. N. Nicholls, J. Puga, P. R. Raithby,M. J. Rosales, M. McPartlin and W. Clegg, J. Chem. SOC., DaltonTrans., 1983, 277.8 G. M. Sheldrick, (a) SHELXS 86, Acta Crystallogr., Sect. A, 1990,46, 467; (b) SHELX 76, Program for Crystal Structure Deter-mination, University of Cambridge, 1976; (c) SHELXL 92, Programfor Crystal Structure Determination (Gamma-test version), Univer-sity of Gottingen, 1992.Received 12th July 1993; Paper 3/04045