Hydrogen bonding in α-ferrocenyl alcohols: structures of 1-ferrocenylethanol, 1-ferrocenyl-2-phenylethanol, 1-ferrocenyl-1-phenylpropan-1-ol, 1-ferrocenyl-1-phenyl-2-methylpropan-1-ol, 1-ferrocenyl-1-phenyl-2,2-dimethylpropan-1-ol, 1-ferrocenyl-1,2-diphenylethanol and diferrocenyl(phenyl)methanol

The structure of 1-ferrocenylethanol (la), C₁₂H₁₄FeO, tetragonal, I4₁cd, a = 23.3334 (18), c = 7.7186 (11) Å, Z = 16, R = 0.025 for 850 observations [I > 3σ(I)], contains spiral chains generated by a 4₁ axis, in which the molecules are connected by O—H...O hydrogen bonds in a motif with graph set C(2) with an O...O distance of 2.724 (3) Å. 1-Ferrocenyl-2-phenylethanol (If), C₁₈H₁₈FeO, orthorhombic, Pnaa, a = 9.8589 (7), b = 15.2800 (17), c = 19.1399 (17) Å, Z = 8, R = 0.036 for 1508 observations [I > 3σ(I)], crystallizes as dimeric aggregates lying across a crystallographic twofold axis and held together by O—H...O hydrogen bonds in a motif with graph set R²₂(4) with an O...O distance of 2.868 (8) Å; there are also intramolecular O—H...π(C₅H₅) interactions. 1-Ferrocenyl-1-phenylpropan-1-ol (2b), C₁₉H₂₀FeO, monoclinic, P2₁/c, a = 10.2443 (13), b = 10.5811 (17), c = 14.2487 (12) Å, β = 100.190 (9)°, Z = 4, R = 0.029 for 2289 observations [I > 3σ(I)], crystallizes as isolated molecules containing O—H...π(C₅H₅) interactions. In 1-ferrocenyl-1-phenyl-2-methylpropan-1-ol (2c), C₂₀H₂₂FeO, monoclinic, Cc, a = 25.387 (4), b = 7.6825 (6), c = 17.803 (3) Å, β = 108.217 (17)°, Z = 8, R = 0.022 for 3286 observations [I > 3σ(I)], there are two molecules in the asymmetric unit, but the structure consists of isolated molecules containing O—H...π(C₅H₅) interactions. 1-Ferrocenyl-1-phenyl-2,2-dimethylpropan-1-ol (2d), C₂₁H₂₄FeO, monoclinic, P2₁/n, a = 8.007 (4), b = 13.002 (2), c = 66.24 (1) Å, β = 91.96 (3)°, Z = 16, R = 0.072 for 4130 observations [I > 3σ(I)], has four molecules in the asymmetric unit, but there is no intermolecular hydrogen bonding. The structure of 1-ferrocenyl-1,2-diphenylethanol (2f), C₂₄H₂₂FeO, monoclinic, C2/c, a = 26.229 (2), b = 5.889 (2), c = 24.553 (2) Å, β = 104.114 (11)°, Z = 8, R = 0.036 for 1733 observations [I > 2.5σ(I)], consists of isolated molecules in which the hydroxyl H atom is disordered unequally over three sites, each of which is trans to one of the C—C bonds involving C1; H atoms in two of these sites are involved in intramolecular O—H...π(C₅H₅) interactions and the H atom in the third is involved in an O—H...π(arene) interaction. The structure of diferrocenyl(phenyl)methanol (2g), C₂₇H₂₄Fe₂O, triclinic, P, a = 9.3999 (11), b = 11.1988 (16), c = 11.9720 (16) Å, a =117.844 (11), β = 98.890 (10), γ = 102.362 (11)°, Z = 2, R = 0.031 for 3435 observations [I > 2.5σ(I)], consists of centrosymmetric dimers held together by O—H...O hydrogen bonds in a motif with graph set R²₂(4) with an O...O distance of 2.926 (4) Å; there are also intramolecular O—H...π(C₅H₅) interactions. Closed dimers containing the R²₂(4) (OH)₂ hydrogen-bonding motif, while unknown for purely organic alcohols, are a common occurrence in α-ferrocenyl alcohols (five examples from 13 known structures).

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