X-ray crystal structures of complex metallates containing the sterically demanding 1,3,5-tri(tert-butyl)tropylium cation

The X-ray crystal structures of anionic transition metal complexes containing the sterically demanding 1,3,5-tri-tert-butyltropylium cation, [1,3,5-C(7)H(4)tBu(3)](+), as the compensating ion are presented. Bis(1,3,5-tri-tert-butyltropylium) hexachlorodiferrate(II), [1,3,5-C(7)H(4)tBu(3)](2)[Fe2Cl6] (4), was obtained from the reaction of the 1,3,5-tri-tert-butyltropylium hydrogendichloride, [1,3,5-C(7)H(4)tBu(3)][HCl2] (3), with FeCl2, whereas the 1,3,5-tri-tert-butyltropylium tetrabromooxomolybdate(V) [1.3,5-C(7)H(4)tBu(3)][trans-Mo(O)Br-4(CH3CN)] (7) was isolated from the reaction of the cycloheptatrienyl complex [(eta(7)-1,3,5-C(7)H(4)tBu(3))Mo(CO)(2)Br] (6) with elemental bromine. The crystal structures of 3, 4, 7 and 7 center dot CH3CN show in each case well separated anions and cations and the absence of any covalent anion-cation interactions. However, close inspection of the crystal packing reveals that the 1,3,5-tri-tert-butyltropylium cation can act as a CH-proton donor towards the counterion leading to the formation of weak C-H center dot center dot center dot Cl-M and C-H center dot center dot center dot O=M hydrogen bonds in 4 and in 7 and 7 center dot CH3CN, respectively.