Synthesis and crystal structure of [Cs([2.2.2]crypt)] 2 [Mo(CO) 5 ]

Reduction of the heteroleptic metal carbonyl complex Mo(CO) 3 (η 5 -Cp)H with the metallic salt Cs 5 Bi 4 in the presence of [2.2.2]crypt (= 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane) in liquid ammonia led to single crystals of bis[(4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane)caesium] pentacarbonylmolybdate, [Cs(C 18 H 36 N 2 O 6 )] 2 [Mo(CO) 5 ] or [Cs([2.2.2]crypt)] 2 [Mo(CO) 5 ]. The twofold negatively charged anionic complex corresponds to the 18 valence electron rule. It consists of an Mo atom coordinated by five carbonyl ligands in a shape intermediate between trigonal–bipyramidal and square-pyramidal. The Mo—C distances range from 1.961 (3) to 2.017 (3) Å, and the C[triple-bond]O distances from 1.164 (3) to 1.180 (4) Å.