Noble‐Gas Difluoride Complexes of MOF4 (M=Mo, W); Syntheses, Structures and Bonding of NgF2 ⋅ MOF4 and XeF2 ⋅ 2MOF4 (Ng=Kr, Xe)

The NgF₂  ⋅ MOF₄ (Ng=Kr, Xe; M=Mo, W) and XeF₂  ⋅ 2MOF₄ complexes were synthesized in anhydrous HF (aHF) solvent and melts, respectively. Their single-crystal X-ray diffraction (SCXRD) structures show NgF₂  ⋅ MOF₄ and XeF₂  ⋅ 2MOF₄ have F_t -Ng-F_b - - -M arrangements, in which the NgF₂ ligands coordinate to MOF₄ through Ng-F_b - - -M bridges. The XeF₂ ligands of XeF₂  ⋅ 2MOF₄ also coordinate to F₃ OM-F_b '- - -M'OF₄ moieties through Xe-F_b - - -M bridges to form F_t -Xe-F_b - - -M(OF₃ )-F_b '- - -M'OF₄ , where XeF₂ coordinates trans to the M=O bond and F_b ' coordinates trans to the M'=O bond. The Ng-F_t , Ng-F_b , and M- - -F_b bond lengths of NgF₂  ⋅ nMOF₄ are consistent with MOF₄ and F₃ OM-F_b '- - -M'OF₄ fluoride-ion affinity trends: CrOF₄ <MoOF₄ <WOF₄ ≈F₃ OMo-F_b '- - -Mo'OF₄ <F₃ OW-F_b '- - -W'OF₄ . The [- -(F₄ OMo)(μ₃ -F)H- - -(μ-F)H- -]_∞ solvate was also synthesized in aHF and characterized by SCXRD. Quantum-chemical calculations show the M- - -F_b bonds of NgF₂  ⋅ MOF₄ and XeF₂  ⋅ 2MOF₄ are predominantly electrostatic, σ-hole type bonds.