Unprecedented μ3-Oi face-capping ligand in a [Mo6Bri6Li2Bra6] (L = 0.5 O + 0.5 Br) molybdenum cluster unit: crystal structure of the Cs3Mo6Br13O oxybromide

The new Cs
3
Mo
6
Br
13
O oxybromide, synthesized by solid-state chemistry, crystallizes in the trigonal system (
R




3


_




c
space group;
a
 = 15.5784(2) Å,
c
 = 19.5103(5) Å,
V
 = 4100.5(1) Å
3
and
Z
 = 6). It is based on a [Mo
6
L
14
] unit that contains an unprecedented
μ
3
face-capping oxygen. The crystal structure determined by single crystal X-ray diffraction is built up from discrete face-capped [Mo
6
Br
i
6
L
i
2
Br
a
6
]
3–
(
L
 = 0.5 O + 0.5 Br) anionic units in which two inner positions are randomly occupied by one bromine and one oxygen whereas the other ligand positions are fully occupied by bromine. The cesium cations randomly occupy two close crystallographic positions generated by the
A-B-C-A
′
-B
′
-C
′ close-packed stacking of the units. The cesium site occupancy is related to the random distribution of oxygen and bromine on the L
i
inner positions. .