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The 1,3-diene 2,3-dimethylene-5,6,7,8-dibenzobicyclo[2.2.2] octane (ddbo, C18H14, 6) forms complexes Ir(eta-C5H5)(C18H14) (7), M(eta-C5Me5)(C18H14) [M = Rh (8), Ir (9)], and M(eta-1,3,5-C6H3Me3)(C18H14) [M = Ru (10), Os (11)], which react with aqueous HPF6 or triflic acid to give fluxional monoprotonated cations [Ir(eta-C5H5)(C18H15)]+ (14), [Rh(eta-C5Me5)(C18H15)]+ (12), [Ru(eta-C6H3Me3)(C18H15)]+ (13), and [Os(eta-C6H3Me3)(C18H15)]+ (15). Crystals of 13.PF6 are orthorhombic, space group P2(1)2(1)2(1), with a = 14.243 (2) angstrom, b = 13.554 (2) angstrom, c = 12.894 (2) angstrom, and Z = 4. The structure was solved by heavy-atom methods and refined by least-squares analysis to R = 0.034 and R(w) = 0.043 for 2020 unique observed reflections. The C18H15 moiety is bound to a (eta-6-mesitylene)ruthenium unit through a eta-3-enyl linkage [Ru-C(1) = 2.180 (8) angstrom, Ru-C(2) = 2.196 (7) angstrom, Ru-C(17) = 2.148 (7) angstrom] and a two-electron, three-center interaction Ru-H(18C)-C(18) to the terminal methyl group of the butenyl moiety [Ru-C(18) = 2.357 (9) angstrom, C(18)-H(18C) = 0.98 (8) angstrom, Ru-H(18C) = 1.81 (8) angstrom, angle C(17)-C(18)-H(18C) = 108 (5)-degrees, angle C(18)-H(18C)-Ru = 112 (6)-degrees]. The NMR (H-1, C-13) spectra of the rhodium complex 12 at-60-degrees-C are consistent with a similar ground-state agostic eta-3-methallyl structure, but unexpectedly, the H-1 NMR spectrum of 13 at -100-degrees-C resembles that expected for a hydrido (1,3-diene) structure. It is suggested that in 13 reversible C-H bond cleavage occurs more easily than M-H bond cleavage, whereas 12 shows the more usual reverse behavior. The NMR and IR spectra of 14 show this complex to have a hydrido 1,3-diene structure; the same is probably true for 15, although a eta-3-methallyl structure with a strong agostic interaction cannot be excluded. Treatment of 13 and 15 with tert-butyl isocyanide causes irreversible hydride transfer to ddbo, giving [M(eta-C6H3Me3)(C18H15)(CN-t-Bu)]PF6 [M = Ru (17), Os (16)].

Treatment of the arene endo-dicyclopentadiene complexes of zerovalent ruthenium and osmium M(e-arene)(e4-C10H12) (M = Ru, arene = C6Me6; M = Os, arene = C6H3Me3-1,3,5) with HPF6 gives monoprotonated salts [M(C10H13)(e-arene)]PF6. Similar salts are obtained by treatment of the complexes Rh(e-C5R5)(e4-C10H 12) (R = H, Me) and Ir(e-C5Me5)(e4-C10H 12) with HPF6. The salt [Os(C10H13)(e-C6H3Me 3)]PF6 crystallizes in two modifications, 2a and 2b. The former belongs to space group P21/n, with a = 11.584 (2) A, b = 12.235 (2) A, c = 13.990 (2) A, b = 88.40 (2)d, and Z = 4, and the latter to space group P21, with a = 12.484 (2) A, b = 10.124 (2) A, c = 7.611 (1) A, b = 95.54 (2)d, and Z = 2. The structures of both forms have been solved by heavy-atom methods and refined by least-squares analysis to R = 0.042 and Rw = 0.055 for 2150 unique reflections (I g 3s) (2a) and to R = 0.041 and Rw = 0.041 for 3065 unique reflections (I g 3s) (2b), the derived metrical data for 2a being more precise and reliable than those for 2b. The cation consists of a (e6-mesitylene)osmium(II) unit attached to dicyclopentadiene by a s-bond to one of the norbornene carbon atoms [Os-C(5) = 2.19 (2) A] and by an e2-olefin bond to the cyclopentene fragment [Os-C(1) = 2.20 (2) A; Os-C(2) = 2.25 (2) A]. Although not located directly, the added proton probably bridges the osmium atom and the second norbornene carbon atom C(6) by a two-electron-three-center interaction [Os-C(6) = 2.30 (2) A]. This is supported by an examination of the bonding geometry about C(6), by R factor analysis, and by 1H and 13C NMR spectroscopic studies on all the protonated dicyclopentadiene complexes. Assuming the bridging hydrogen atom to be tetrahedrally disposed at 0.95 A from C(6) (undoubtedly an underestimate), the calculated Os-H distance is 1.81 A in 2a [1.90 A in 2b] and the C-H-Os angle is 110d in 2a (104d in 2b).

The syntheses of some new chloromethyl complexes are reported. The reactions of these and other chloromethyl complexes with triphenylphosphine have been investigated. Fe(Cp)(CO) 2 CH 2 Cl and W(Cp)(CO) 3 CH 2 Cl yield the cationic ylide complexes [Fe(Cp)(CO) 2 CH 2 PPh 3 ] + and [W(Cp)(CO) 3 CH 2 PPh 3 ] + . Some new methoxymethyl complexes are also described.

The reactions of Na[Mn(CO)5] or Na[Mn(CO)4(PPh3)] with CH2ClI yield the new chloromethyl complexes Mn(CO)5CH2Cl and Mn(CO)4(PPh3)CH2Cl. Reaction of Na[Re(CO)5] or Na[CpRu(CO)2] with ClCH2OMe yields Re(CO)5CH2Cl and CpRu(CO)2CH2Cl respectively, in addition to the corresponding methoxymethyl complexes (Cp = η5-C5H5). Reaction of CpRu(CO)2CH2OMe with HCl yields the corresponding chloromethyl complex.