Mendeleev Communications Electronic Version, Issue 4, 2001 (pp. 125.164) Generation of the metallonium cations [1,2-(CH2)2C5Me3OsC5Me5]2+, [1,1'-(CH2C5Me4)2Os]2+ and [1,2-(CH2)2C5Me3Os(1'-CH2C5Me4)]3+ in the CF3SO3H.O2 system Margarita I. Rybinskaya, Alla A. Kamyshova,* Arkadii Z. Kreindlin and Pavel V. Petrovskii A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 117813 Moscow, Russian Federation.Fax: +7 095 135 5085; e-mail: kreindlin@ineos.ac.ru 10.1070/MC2001v011n04ABEH001456 The title dications and trication were generated from decamethylosmocene and [C5Me5OsC5Me4CH2]+, respectively, by the interaction with dioxygen in CF3SO3H solutions. Previously,1.3 we found that strong protic acids can promote the oxidation of methyl substituents in the decamethylmetallocenes (C5Me5)2M (M = Ru or Os) under certain conditions. Decamethylruthenocene can be oxidised by molecular oxygen in the superacid CF3SO3H to form mono-, di- or even trications.In this work, we examined this reaction by the example of decamethylosmocene 1 and salt¢Ó [C5Me5OsC5Me4CH2]+BF4 . 2 as the product of its one-electron oxidation. The behaviour of compound 1 in CF3SO3H (98%, Fluka) in an inert atmosphere of argon was preliminarily studied by 1H NMR spectroscopy.It was found that, in contrast to (C5Me5)2Ru, which forms the monohydride [(C5Me5)2RuH]+ under these conditions, decamethylosmocene 1 affords dihydride [(C5Me5)2OsH2]2+ 3. The monohydride [(C5Me5)2OsH]+ is usually formed in weaker acids.1 In the case of monocation 2 in a CF3SO3H solution in an inert atmosphere, dication [C5Me5Os(H)C5Me4CH2]2+ 4 was formed as the product of monoprotonation.The reactions of 1 and 2 with oxygen in CF3SO3H solutions were performed in NMR tubes (0.7 ml) with bubbling oxygen¢Ô at regular intervals, as described previously3 for the reaction with (C5Me5)2Ru. The course of the reaction was monitored by 1H NMR spectroscopy.The formation of dihydride 3 (from 1) and protonated monocation 4 (from 2) was detected at the first step. Previously described5,6 dications [1,2-(CH2)2C5Me3OsC5Me5]2+ 5 and [1,1'-(CH2C5Me4)2Os]2+ 6, as well as a new species that corresponds to trication [1,2-(CH2)2C5Me3Os(1'-CH2C5Me4)]3+ 7, were identified among the reaction products. The completion of the reaction was judged from the disappearance of dihydride 3 or dication 4 in the oxidation of 1 or 2, respectively.A comparison between the ratios of products obtained in the oxidation of 1 demonstrates that dications 5 (62%) and 6 (34%) were primarily formed, and the portion of trication 7 was as low as 4%. The yield of trication 7 cannot be increased by further passing of oxygen (Scheme 1).In the case of oxidation of compound 2 (Scheme 2), trication 7 was the main reaction product (81% on a basis of identified products), whereas dications 5 and 6 were formed in minor amounts (19%) (5:6 ~ 1.4:1) (Scheme 1). The structures of the products were supported by 1H and 13C NMR data.¡× Thus, the 1H NMR spectrum of dihydride 3 exhibits two singlet signals, and the ratio between the integral intensities of methyl protons and the signal of an OsH proton is equal to 15:1.All signals in the spectrum of dication 4 are broadened (.n1/2 ¡í 22.24 Hz for the signals of Me groups of the C5Me4 ring and the CH2 group, and .n1/2 ¡í 6.7 Hz for the signals of Me groups of the C5Me5 ring and the signal of OsH). Similarly to [C5Me5Re(H)C5Me4CH2]+,7 the protons of the CH2 group are non-equivalent, as well as the protons of Me groups of the C5Me4CH2 ring (four signals of 3H).The 1H NMR spectra of dications 5 and 6 are consistent with the spectra of dications obtained by the protonation of corresponding dicarbinols.5,6 The assignment of signals in the spectrum of trication 7 presented no special problems because all of the signals exhibited the same behaviour as those of the trication [1,2-(CH2)2C5Me3Ru(1'-CH2- C5Me4)]3+.3 Thus, the spectrum contained three signals of the same intensity (2H) from three CH2 groups, and the chemical shifts of these signals [d = 5.04 (d), 5.66 (d) and 5.49 (s) ppm] are almost equal to the values published for the Ru-containing trication.3 The appearance of signals due to three CH2 groups as two doublets and a singlet indicates that trication 7 exhibits a plane of symmetry and does not contain a C5Me5 ring.The equality of .dAB differences for trication 7 (0.62 ppm) and 1,2-dication 5 (0.62 ppm) is indicative of the 1,2-arrangement of CH2 groups in the C5Me3(CH2)2 ring of trication 7. The 13C NMR spectra of all complexes also support the structures. Thus, the carbon atoms of two 1,2-CH2 groups of trication 7 exhibit a chemical shift of 71.32 ppm in the 13C NMR spectrum and appear as a triplet with 1JCH = 172 Hz. The carbon atom of the 1'-CH2 group gives an upfield triplet (d = 65.75 ppm, 1JCH 157 Hz).Note that two CH2 groups in the Ru-containing trication exhibit a chemical shift of 88.57 ppm (1JCH = 172 Hz), whereas the chemical shift and 1JCH of the third 1'-CH2 group are consistent with the corresponding values for the 1'-CH2 group in trication 7.It is known8 that the great difference between the electronegativities of transition metal complexes and O2 induces the formation of bridging or nonbridging oxo compounds. Com- ¢Ó Complex 2 was prepared from C5Me5OsC5Me4CH2OH using HBF4 etherate.4 ¢Ô A solution of ~0.1 mmol of complex 1 or ~0.02 mmol of complex 2 in CF3SO3H (~3 mmol) was placed in a tube. Oxygen (~1 l) was bubbled through the solution for 2.3 h at ambient temperature. Os Os H H 2+ CF3SO3H, O2 20 ¡ÆC Os 2+ Os 2+ 1 3 5 6 Scheme 1 ¡× The NMR spectra were measured on a Bruker AMX-400 spectrometer (400.13 and 100.61 MHz for 1H and 13C, respectively).An external standard was used for CF3SO3H solutions (d C6D5H 7.25 and 127.96 ppm for 1H and 13C, respectively). 3: 1H NMR, d: 2.68 (s, 30H, C5Me5), .14.58 (s, 2H, OsH). 13C NMR, d: 8.77 (¥ã-Me), 106.32 (CCp). 4: 1H NMR, d: 2.57 (s, 15H, C5Me5), 2.17, 2.31, 2.51 and 2.98 (4s, 4¡¿3H, ¥á- and ¥â-Me), 5.17, 5.79 (2s, 2¡¿1H, CH2), .15.40 (s, 1H, OsH). 13C NMR, d: 9.29 (¥ã-Me), 8.55 (¥á-Me), 9.35 (¥â-Me), 66.50 (CH2), 107.06 (C1), 96.39, 102.74, 108.4 (CCp), 105.53 (¥ã-CCp). 5: 1H NMR, d: 2.57 (s, 15H, C5Me5), 2.14 (s, 6H, ¥á-Me), 2.57 (s, 3H, ¥â-Me), 4.90 and 5.52 (2d, 2¡¿2H, CH2 AB, 2Jgem HH 2.7 Hz); cf. ref. 5. 13C NMR, d: 10.00 (¥ã-Me), 9.41 (¥á-Me), 10.23 (¥â-Me), 70.92 (CH2, 1JCH 171 Hz), 134.66 (C1), 105.53, 115.06 (CCp), 107.58 (¥ã-CCp); cf. ref. 5. 6: 1H NMR, d: 2.19, 2.31, 2.41 and 2.83 (4¡¿6H, ¥á,¥á',¥â,¥â'-Me), 5.43, 5.87 (2d, 2¡¿2H, CH2); cf.ref. 6. 13C NMR, d: 6.83, 8.64 (¥á,¥á'-Me), 8.89, 10.90 (¥â,¥â'-Me), 73.31 (CH2, 1JCH 170 Hz), 99.86, 105.71, 111.51, 116.07, 116.53 (CCp). 7: 1HNMR, d: 2.19, 2.50, 2.71 and 3.03 (3¡¿6H, 3H, ¥á,¥á',¥â,¥â'-Me), 5.04, 5.66 (2d, 2¡¿2H, CH2 AB, 2Jgem HH 2.3 Hz), 5.49 (s, 2H, CH2). 13CNMR, d: 8.67, 8.71, 9.28 (3¡¿2Me), 9.47 (Me), 65.75 (CH2, 1JCH 157 Hz), 71.32 (2CH2, 1JCH 172 Hz), 93.20, 102.70, 106.93, 108.45, 116.80, 135.12 (CCp).Mendeleev Communications Electronic Version, Issue 4, 2001 (pp. 125–164) plexes having a free coordination site let O2 bind the metal in end-on and edge-on modes. The unprecedented mode of C–H activation of permethyl ligands (for example, ç6-arene) implies a monoelectronic transfer from an organometallic complex to O2 followed by the deprotonation of O2 · –, a ligand activated by the cationic metal moiety:9 The transformation of O2 into the radical anion is due to a low redox potential of this passage (E1/2 = –0.7 V/SCE).8 Now, we can only say that dication [C5Me5Os(H)C5Me4CH2]2+ 4 is an obligatory synthon on the way to trication 7 because the protonation of [C5Me5OsC5Me4CH2]+BF4 – 2 and the formation of trication 7 in the CF3CO2H–O2 system do not take place.Thus, trication 7 can be generated by the oxidation of monocation 2 with oxygen in CF3SO3H. At the same time, the oxidation of osmocene 1 with O2 in CF3SO3H can be considered as a method for generating dications 5 and 6. This work was supported by the Russian Foundation for Basic Research (grant no. 00-03-32894). References 1 A. A. Kamyshova, A. Z. Kreindlin, M. I. Rybinskaya and P. V. Petrovskii, Izv. Akad. Nauk, Ser. Khim., 1999, 587 (Russ. Chem. Bull., 1999, 48, 581). 2 A. A. Kamyshova, A. Z. Kreindlin, M. I. Rybinskaya and P. V. Petrovskii, Izv. Akad. Nauk, Ser. Khim., 2000, 517 (Russ. Chem. Bull., 2000, 49, 520). 3 M. I. Rybinskaya, A. A. Kamyshova, A. Z.Kreindlin and P. V. Petrovskii, Mendeleev Commun., 2000, 85. 4 A. Z. Kreindlin, P. V. Petrovskii and M. I. Rybinskaya, Izv. Akad. Nauk SSSR, Ser. Khim., 1987, 1620 (Bull. Acad. Sci. USSR, Div. Chem. Sci., 1987, 36, 1489). 5 A. Z. Kreindlin, E. I. Fedin, P. V. Petrovskii, M. I. Rybinskaya, R. M. Minyaev and R. Hoffmann, Organometallics, 1991, 1206. 6 M. I. Rybinskaya, A. Z. Kreindlin, P. V. Petrovskii, R. M. Minyaev and R. Hoffmann, Organometallics, 1994, 3903. 7 F. G. N. Cloke, J. P. Day, J. C. Green, C. P. Morley and A. C. Swain, J. Chem. Soc., Dalton Trans., 1991, 789. 8 L. I. Simandi, Catalytic Activation of Dioxygen by Metal Complexes, Kluwer, Dordrecht, 1992. 9 D. Astruc, J.-R. Hamon, E. Roman and P. Michaud, J. Am. Chem. Soc., 1981, 103, 7502. Os 2 CF3SO3H, O2 20 °C Os 4 H 2+ Os 7 3+ Scheme 2 MRH + O2 MRH+O2 · – MR – HO2 Received: 28th March 2001; Com. 01/1782