Single addition of the nucleophiles X-= H-, CN-or OH-t o (q6-arene) (q6-[2.2]paracyclophane)-ruthenium(r1) tetrafluoroborate (arene = benzene, p-cymene, 1,4-diisopropylbenzene or hexamethylbenzene) and the osmium(1i) q6-C6H6 analogue produces the (q5-cyclohexadienyl) (q6-[2.2] paracyclophane)metal(it) complexes as the sole products. These compounds have been identified by l H NMR and by infrared spectroscopy. The expected isotope shift is observed when Na[BD,] is used in place of Na [BH,]. The steric factors influencing the site of nucleophilic attack are discussed and nucleophilic addition to [ R~( q~-C ,~t i~~) , ] [BF,], is also examined. Both single and double nucleophilic addition to co-ordinated arenes is of significant interest as a synthetic route to arene functionalisation and a single nucleophilic attack is a key initial step in the recently reported synthesis of ( f )-dihydroxyserrulatic acid.' While bis(arene)ruthenium complexes are expected ' to be around thirty times less electrophilic than their iron analogues they display a number of advantages which make them the more attractive alternative in this type of work. These advantages include (a) the ready availability, uiu the Bennett and Rybinskaya 5.6 syntheses, of unsymmetrical complexes and (6) the elimination of interfering electrontransfer reactions 7-9 which can occur on the addition of carbondonor nucleophiles and result in the formation and often rapid decomposition of unstable nineteen-and twenty-electron species. Use of the highly sterically hindered [2.2]paracyclophane ligand has recently been shown to direct nucleophilic attack onto less-hindered arenes co-ordinated to the same metal centre" to produce q4-diene complexes such as [Ru(q6-cyclohexa-1,4-diene). In addition, protonation of an q4-C2.2)paracyclophane compound gives a co-ordinated q '-cyclophane with the added hydrogen atom in the endo position." That reaction is believed to involve the initial formation of a metal hydride foliowed by proton transfer to the carbocyclic ring. We now report the use of the [2.2]paracyclophane ligand to direct singk nucleophilic attack onto a number of q6-arenes and examine the question of exo or endo addition by a study of the effects of deuterium isotopic substitution on solid-state infrared and solution 'H NMR spectra. A preliminary report ofpart of this work has been published. ' ' c 1 gH 1 6)(q4-C6Me6H2)](C6Me6H2 = 1,2,3,4,5,6-hexamethyI- spaced doublet resonance ('JHH = 13.5 Hz) is observed at 6 2.06 and is assigned to He,, Results and Discussio
