Bis(η⁶-naphthalene)­molybdenum(0)

The title compound, [Mo(C₁₀H₈)₂], was prepared from the naphthalene radical anion and MoCl₄(thf)₂ (thf is tetra­hydro­furan). In the crystal, the mol­ecule is located on an inversion center. The Mo atom is equally disordered over two positions; the range of Mo—C distances is 2.2244 (19)–2.3400 (17) Å for both components of the disorder.

([2.2.2]Cryptand-κ⁶O)potassium (η⁴-cyclo­octa­diene)bis­(η²-pyrene)cobaltate(1−) pentane hemisolvate

The cation, anion, and solvent in the title compound, [K(C₁₈H₃₆N₂O₆)][Co(C₈H₁₂)(C₁₆H₁₀)₂]·0.5C₅H₁₂, are well separated. The pentane solvent mol­ecules are found in channels along [100] and were modeled as disordered over crystallographic inversion centers. Using the mid-points of the coordinated olefins, the angle between the C_py/C_py–Co–C_py/C_py and the C_cod/C_cod–Co–C_cod/C_cod planes (py is pyrene and cod is cyclo­octa­diene) is 67.6 (2)°. Thus, the overall geometry of the coordination sphere around cobalt is best described as distorted tetra­hedral.

(18-Crown-6)potassium [(1,2,5,6-η)-cyclo­octa-1,5-diene][(1,2,3,4-η)-naph­tha­lene]­ferrate(−I)

The title salt, [K(C₁₂H₂₄O₆)][Fe(C₈H₁₂)(C₁₀H₈)], is the only known naphthalene complex containing iron in a formally negative oxidation state. Each (naphthalene)(1,5-cod)ferrate(−I) anion is in contact with one (18-crown-6)potassium cation via K...C contacts to the outer four carbon atoms of the naphthalene ligand (cod = 1,5-cyclo­octa­diene, 18-crown-6 = 1,4,7,10,13,16-hexa­oxacyclo­octa­deca­ne). When using the midpoints of the coordinating olefin bonds, the overall geometry of the coordination sphere around iron can be best described as distorted tetra­hedral. The naphthalene fold angle between the plane of the iron-coordinating butadiene unit and the plane containing the exo-benzene moiety is 19.2 (1)°.

(2.2.2-Cryptand)potassium tetra­kis­(η²-ethyl­ene)cobaltate(−I)

The title salt, [K(C₁₈H₃₆N₂O₆)][Co(C₂H₄)₄], is one of only two known homoleptic ethyl­enemetalates. The cation and anion are well separated, which gives an unperturbed tetra­hedral anion as is expected for a formally Co^−I d¹⁰ metal center. The considerable elongation of the C=C bonds of the ethyl­ene ligands [average 1.401 (6) Å], relative to that of free ethyl­ene (1.333 Å), is consistent with metal→π* back-bonding models. One arm of the 2.2.2-cryptand (4,7,13,16,21,24-hexa­oxa-1,10-diaza­bicyclo­[8.8.8]hexa­cosa­ne) complexant is disordered and was modeled over two positions with a refined occupancy ratio of 0.559 (2):0.441 (2). In the crystal, the cationic K(2.2.2-cryptand) units are linked via C—H...O hydrogen bonds, forming inversion dimers. There are no other significant inter­molecular inter­actions in the crystal structure.