Di-, hexa- and poly-nuclear molybdenum(II) carboxylates containing quadruply bonded [Mo2]4+ units: crystal structures of [Mo2(O2CCHF2)2(bpy)2 (MeCN)(BF4)][BF4] and [Mo6(O2CCHF2)12(bpy)4 ] (bpy = 2,2′-bipyridine)

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Abstract
The reaction of [Mo 2 (O 2 CMe) 4 ] with an excess of CHF 2 CO 2 H resulted in the formation of [Mo 2 (O 2 CCHF 2 ) 4 ]·MeCN 1. Treatment of 1 with Et 3 O + gave [Mo 2 (O 2 CCHF 2 ) 2 (MeCN) 4 ][BF 4 ] 2 2, which was converted into [Mo 2 (O 2 CCHF 2 ) 2 (bpy) 2 (MeCN)(BF 4 )][BF 4 ] 3 on addition of 2,2′-bipyridine (bpy). The reaction of 1 and 3 (1∶2) in the presence of CHF 2 CO 2 - gave the `trimer-of-dimers' complex [Mo 6 (O 2 CCHF 2 ) 12 (bpy) 4 ] 4 in which two [Mo 2 (O 2 CCHF 2 ) 4 (bpy) 2 ] units are the two axial ligands to a central [Mo 2 (O 2 CCHF 2 ) 4 ] unit. The related reaction of 1 and 3 at a 1∶1 ratio in the presence of CHF 2 CO 2 - gave [Mo 4 (O 2 CCHF 2 ) 8 (bpy) 2 ] n 5, which was concluded to be a one-dimensional polymer consisting of alternating [Mo 2 (O 2 CCHF 2 ) 4 (bpy) 2 ] and [Mo 2 (O 2 CCHF 2 ) 4 ] units identical to those in 4.