(2.2.2-Cryptand)potassium tetra­carbonyl­cobaltate(-I)

The title salt, [K(C₁₈H₃₆N₂O₆)][Co(CO)₄], is an example of a classical carbonyl­metalate. The asymmetric unit contains one cation and one tetrahedral anion, both in general positions. Based on comparison of the four carbonyl C-O bond lengths and C-Co-C angles, the anion is unperturbed by the cation, which is normal for an alkali metal fully encased by a cryptand cage.

(η⁴-Cyclo­octa­tetra­ene)(η⁸-cyclo­octa­tetra­ene)iodido­tantalum(V)

The title complex, [Ta(η⁴-C₈H₈)(η⁸-C₈H₈)I], lies across a crystallographic mirror plane that includes the Ta^V atom and the iodide ligand. One cyclo­octa­tetra­ene (cot) ring is η⁴-coordinating and is bis­ected by the mirror plane. The fold angle between the plane of the coordinating butadiene portion and the middle plane of the ring is 27.4 (4)°. An additional minor fold angle of 9.3 (7)° exists between the final plane in the ring and the middle plane. The other cot ring is η⁸-coordinating and is also cut by the mirror plane. In this case, the ring is disordered over the mirror plane, and one position is modeled with appropriate restraints and constraints with respect to distances, angles and displacement parameters (the second position is generated by symmetry). This ring is nearly planar, with an r.m.s. deviation of only 0.05 Å when all eight C atoms are included in the calculation. Pairs of inter­molecular η⁸-cot rings are parallel stacked and slightly off center, with a centroid–centroid distance of 3.652 Å. No other significant inter­molecular inter­actions are observed. The compound is of inter­est as the first structurally characterized mixed halogen–cot complex of the group 5 metals and contains the longest terminal Ta—I distance [3.0107 (5) Å] reported to date.

Bis{bis­[1-meth­oxy-2-(2-meth­oxy­eth­oxy)ethane-κ³O,O′,O′′]sodium} 1,1,2,2-tetra­phenyl­ethane-1,2-diide

Crystals of the title salt, [Na(C₆H₁₄O₃)₂]₂(C₂₆H₂₀), were grown from a tetra­hydro­furan/diglyme/Et₂O solvent mixture [diglyme is 1-meth­oxy-2-(2-meth­oxy­eth­oxy)ethane]. The cations and dianion are separated in the crystal structure, unlike in the other three structurally characterized dialkali metal tetra­phenyl­ethyl­ene salts. The asymmetric unit contains one [Na(diglyme)₂]⁺ cation and one half of the [Ph₂CCPh₂]²⁻ dianion. The latter lies on a twofold rotation axis. C—C bond-length redistribution displays that excessive electron density of the dianion is predominantly located at the C atoms of a former double bond and at all eight ortho positions. The studied crystal was a twin, with the ratio of two major components being 0.2143 (9):0.7857 (9). The twin operation is a twofold rotation around the a axis.

Crystal structure of [(1,2,3,4,11,12-η)-anthracene]tris­(tri­methyl­stann­yl)cobalt(III)

The first reported structure of a cobalt complex containing an η⁶-anthracene ligand is presented. The anthracene ligand is nearly flat and coordinates the metal asymmetrically, such that the ring junction carbon atoms are slightly further from the cobalt center than are the other four.