A fast method for ®tting model electron densities into EM reconstructions is presented. The methodology was inspired by the molecular-replacement technique, adapted to take into account phase information and the symmetry imposed during the EM reconstruction. Calculations are performed in reciprocal space, which enables the selection of large volumes of the EM maps, thus avoiding the bias introduced when de®ning the boundaries of the target density.

The allenylidene complexes [M(CCCR2)(η5-C9H7)L2][PF6] (M = Ru, L = PPh3, L2 = 1,2-bis(diphenylphosphino)ethane (dppe), bis(diphenylphosphino)methane (dppm), R2 = 2 Ph (1a−c), C12H8 (2,2‘-biphenyldiyl) (2a−c); M = Os, L = PPh3, R2 = 2Ph (3), C12H8 (4)) have been prepared by reaction of the complexes [MCl(η5-C9H7)L2] with HC⋮CC(OH)R2 and NaPF6 in refluxing methanol. The crystal structures of [M(CCCPh2)(η5-C9H7)(PPh3)2][PF6]·CH2Cl2 (M = Ru (1a), Os (3)) were determined by X-ray diffraction methods. In the structures the MCCC chains are nearly linear (M−C(1)−C(2) = 168.5(5)° (1a) and 169.3(4)° (3); C(1)−C(2)−C(3) = 168.2(7)° (1a) and 168.0(5)° (3)) with MC(1) distances of 1.878(5) Å (1a) and 1.895(4) Å (3). The indenyl ligand is η5-bonded to the metal with the benzo ring orientated “cis” with respect to the allenylidene group. Extended Hückel molecular orbital calculations have been used to rationalize the preferred “cis” orientation. The reaction of [RuCl(η5-C9H7)L2] (L = PPh3, L2 = dppe, dppm) with HC⋮CCMe(OH)Ph and NaPF6 in refluxing methanol leads to the formation of the allenylidene complexes [Ru{CCC(Me)Ph}(η5-C9H7)L2][PF6] (6a−c) along with the vinylvinylidene isomers [Ru{CC(H)C(Ph)CH2}(η5-C9H7)L2][PF6] (L = PPh3 (5a), L2 = dppe (5b), dppm (5c)). Only complex 6a could be isolated by chromatography (SiO2) from these mixtures along with complex 7a obtained from the deprotonation of the vinylvinylidene complex 5a. The treatment of these reaction mixtures with potassium carbonate yields the neutral σ-enynyl derivatives [Ru{C⋮CC(Ph)CH2}(η5-C9H7)L2] (7a−c). The monosubstituted allenylidene complex [Ru{CCC(H)Ph}(η5-C9H7)(PPh3)2][PF6] (9) has been prepared by the reaction of [RuCl(η5-C9H7)(PPh3)2] with HC⋮CCH(OH)Ph and NaPF6 in methanol. Under similar reaction conditions [RuCl(η5-C9H7)L2] reacts with HC⋮CCH(OH)R and NaPF6 to afford the alkenylmethoxycarbene derivatives [Ru{C(OMe)C(H)CH(R)}(η5-C9H7)L2][PF6] (L2 = dppe, R = Ph (11b); L2 = dppm, R = Ph (11c), H (13)). [RuCl(η5-C9H7)(PPh3)2] also reacts with HC⋮CC(OH)H2 to give the hydroxyvinylidene complex [Ru{CCH(CH2OH)}(η5-C9H7)(PPh3)2][PF6] (12), which is stable toward the dehydration process.

The diphenylallenylidene complexes [Ru(CCCPh2)(η5-C9H7)L2][PF6] (L = PPh3; L2 = 1,2-bis(diphenylphosphino)ethane (dppe), bis(diphenylphosphino)methane (dppm)) (1 a−c) react with NaOMe to yield the methoxyalkynyl derivatives [Ru{C⋮CC(OMe)Ph2}(η5-C9H7)L2] (3 a−c). Protonation of these species gives back the starting allenylidene derivatives. Regioselective additions on the Cγ are also observed when 1 a,b are treated with LiR (R = Me, nBu), giving the alkynyl complexes [Ru{C⋮CC(R)Ph2}(η5-C9H7)L2] (4a,b, 5 a,b). Vinylidene derivatives [Ru{CC(H)C(R)Ph2}(η5-C9H7)(PPh3)2][BF4] (6a, 7a) can be prepared by protonation of complexes 4a and 5a with HBF4. The diphenylallenylidene compound 1c reacts with LitBu to yield the metallacycle (8c). The alkynyl complexes [Ru{C⋮CC(C⋮CR)Ph2}(η5-C9H7)(PPh3)2] (R = Ph, nPr, H) (9a−11a) have been obtained by reaction of 1a with lithium or sodium acetylides. Protonation of these derivatives yields the vinylidene complexes [Ru{CC(H)C(C⋮CR)Ph2}(η5-C9H7)(PPh3)2][BF4] (12a−14a). The crystal structure of [Ru{C⋮CC(C⋮CH)Ph2}(η5-C9H7)(PPh3)2] (11a) was determined by X-ray diffraction methods. In the structure the alkynyl chain is nearly linear (Ru−C(1)−C(2) = 175.0(2)°) with Ru−C(1) and C(1)−C(2) distances of 1.993(2) and 1.209(3) Å, respectively. The monosubstituted allenylidene complex [Ru{CCC(H)Ph}(η5-C9H7)(PPh3)2][PF6] (2a) reacts with PMe3, PMe2Ph, PMePh2, and PPh3 to yield the cationic alkynyl−phosphonio derivatives [Ru{C⋮CC(PR3)(H)Ph}(η5-C9H7)(PPh3)2][PF6] (17a−20a) in a regioselective way. Similarly, allenylidene complexes 1 a−c add PMe3 to give the corresponding alkynyl−phosphonio derivatives 15 a−c. [Ru{C⋮CC(PMe3)Ph2}(η5-C9H7)(dppm)][PF6] (15c) undergoes an isomerization process to yield the thermodynamically more stable allenyl−phosphonio complex [Ru{C(PMe3)CCPh2}(η5-C9H7)(dppm)][PF6] (21c). [Ru{C(PMe2Ph)CCPh2}(η5-C9H7)(dppm)][PF6] (22c) can be obtained directly by addition of PMe2Ph to the Cα atom of 1c. The behavior of the diphenylallenylidene complexes 1 a−c toward sodium 2-methylthiophenolate is also discussed.

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