Abstract
Charge-assisted hydrogen bonding plays a significant role in the crystal structures of solvates of ionic com-pounds, especially when the cation or cations are primary ammonium salts. We report the crystal structures of four ammonium salts of molybdenum halide cluster solvates where we observe significant hydrogen bonding between the solvent molecules and cations. The crystal structures of bis-(anilinium) octa-μ3-chlorido-hexa-chlorido-octa-hedro-hexa-molybdate N,N-di--methyl-formamide tetra-solvate, (C6H8N)2[Mo6Cl8Cl6]·4C3H7NO, (I), p-phenyl-enedi-ammonium octa-μ3-chlorido-hexa-chlorido-octa-hedro-hexa-mol-yb-date N,N-di-methyl-formamide hexa-solvate, (C6H10N2)[Mo6Cl8Cl6]·6C3H7NO, (II), N,N'-(1,4-phenyl-ene)bis-(propan-2-iminium) octa-μ3-chlorido-hexa-chlo-rido-octa-hedro-hexa-molybdate acetone tris-olvate, (C12H18N2)[Mo6Cl8Cl6]·3C3H6O, (III), and 1,1'-dimethyl-4,4'-bipyridinium octa-μ3-chlo-rido-hexa-chlorido-octa-hedro-hexa-molybdate N,N-di-methyl-formamide tetra-solvate, (C12H14N2)[Mo6Cl8Cl6]·4C3H7NO, (IV), are reported and described. In (I), the anilinium cations and N,N-di-methyl-formamide (DMF) solvent mol-ecules form a cyclic R 4 2(8) hydrogen-bonded motif centered on a crystallographic inversion center with an additional DMF mol-ecule forming a D(2) inter-action. The p-phenyl-enedi-ammonium cation in (II) forms three D(2) inter-actions between the three N-H bonds and three independent N,N-di-methyl-formamide mol-ecules. The dication in (III) is a protonated Schiff base solvated by acetone mol-ecules. Compound (IV) contains a methyl viologen dication with N,N-di-methyl-formamide mol-ecules forming close contacts with both aromatic and methyl H atoms.
Highlights
Charge-assisted hydrogen bonding plays a significant role in the crystal structures of solvates of ionic compounds, especially when the cation or cations are primary ammonium salts
We report the crystal structures of four ammonium salts of molybdenum halide cluster solvates where we observe significant hydrogen bonding between the solvent molecules and cations
In (I), the anilinium cations and N,N-dimethylformamide (DMF) solvent molecules form a cyclic R24(8) hydrogen-bonded motif centered on a crystallographic inversion center with an additional DMF molecule forming a D(2) interaction
Summary
The unique photochemistry of the molybdenum and tungsten halide clusters [M6X8Y6]2À (M = Mo, W; X, Y = Cl, Br, I) has been known for over 30 years (Maverick et al, 1983) and researchers continue to explore the tunabilty of the redox potentials, crystal structures and photochemical properties of cluster-containing compounds via variation of the bridging and terminal ligands and the counter-ion (Mikhailov et al, 2016; Saito et al, 2017; Akagi et al, 2018) Metal clusters, such as molybdenum halides, consist of an inner [Mo6X8]4+ core surrounded by six axial ligands which are more labile than the core ligands, making the preparation of mixed-ligand cluster complexes relatively straightforward. We have prepared a series of ammonium salts of the [Mo6Cl8Cl6]2À complex anion, each containing cations ‘solvated’ by either dimethylformamide or acetone through strong CAHBs
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