An order-disorder transition in Sr2IrD5: Evidence for square pyramidal IrD5 units from powder neutron diffraction data

Structure and Electron Counting in Ternary Transition Metal Hydrides

“…The topology of Li 4 RhH 5 corresponds to such an expulsion of a coordinated hydride from RhH 5 4to yield a square planar RhH 4 3ion (i.e., 4Li + {H -}[RhH 2 2H -] with two two 3c-4ebonds and sd hybridization). Similar to Sr 2 RhH 5 , the neutron diffraction structures of Mg 2 CoH 5 30 and Sr 2 IrH 5 27 demonstrate monovacant O h geometries of [MH 5 ] nfragments consistent with monocationic Sr (see Table 1). In contrast, the structures of A 3 PdH 5 20 and A 3 PtH 5 19 (A ≡ K, Rb, or Cs) exhibit square planar metal hydride complexes with one "expelled" interstitial hydride per formula unit.…”

X-ray and neutron diffraction studies of the polyhydrido complex FeH6Mg4Br3.5Cl0.5(C4H8O)8: discussion of binary transition-metal hydride anions of the type [MHx]n-

“…Hence, the crystal structure of Sr2IrD5 may be viewed as containing square-pyramidal [IrDy]4-anionic units that are sixfold disordered in the high-temperature phase and twofold disordered in the low-temperature modification. 45 As in FeH6Mg4X4(THF)8 and Sr2RuD6, the alkaline-earth atoms in Sr2IrD5 are located over the triangular faces of each octahedron of deuterium atoms. Eu2IrH5 is isostructural with Sr2IrH5,44 but powder neutron diffraction studies of Eu2IrD5 indicate no deuterium-ordering transition down to a temper- ature of 9 K.46 Systems.…”

Raman, FTIR, Photoacoustic-Infrared, and Inelastic Neutron Scattering Spectra of Ternary Metal Hydride Salts A2MH5, (A = Ca, Sr, Eu; M = Ir, Rh) and Their Deuterides

“…Sr 2 IrH 5 spectra were measured at 15 K (363 to 2065 cm –1 ) and at 135 and 210 K (363 to 1024 cm –1 ). These temperatures were chosen to cover the region of the phase transition . Ca 2 RhH 5 spectra were measured at 4 K (309 to 2065 cm –1 ) and at 300 K (328 to 1170 cm –1 ).…”

“…The structure and vibrational spectra have been reported for this compound , and other ternary metal hydride salts of the group 8 transition metals, A 2 MH 6 (A = alkaline earth and lanthanide and M = Ru, Os), have been extensively studied. − The isoelectronic metal hydrido- anions of the neighboring group 9 transition metals, Co, Rh, and Ir, (A 2 MH 5 ), are unusual in that they are pentacoordinated with square-pyramidal molecular structures. The preparation, properties, and structures of the hydrides of iridium and rhodium with calcium, strontium, and europium, − including the mixed salts with Ca–Eu and Sr–Eu, , have been reported. Neutron diffraction studies have shown that the room-temperature crystal structures are face-centered cubic with the K 2 PtCl 6 structure, space group Fm 3 m , but disordered such that the six octahedral sites have 5/6 occupancy. , Transitions to the ordered low-temperature tetragonal structures, space group I 4/ mmm , occur for the calcium and strontium salts where the unit cell is approximately half the volume and contains two formula units instead of four. ,, The four basal (equatorial) positions are fully occupied, the apical (axial) sites are half occupied and the structure is disordered along the c axis.…”

“…The preparation, properties, and structures of the hydrides of iridium and rhodium with calcium, strontium, and europium, − including the mixed salts with Ca–Eu and Sr–Eu, , have been reported. Neutron diffraction studies have shown that the room-temperature crystal structures are face-centered cubic with the K 2 PtCl 6 structure, space group Fm 3 m , but disordered such that the six octahedral sites have 5/6 occupancy. , Transitions to the ordered low-temperature tetragonal structures, space group I 4/ mmm , occur for the calcium and strontium salts where the unit cell is approximately half the volume and contains two formula units instead of four. ,, The four basal (equatorial) positions are fully occupied, the apical (axial) sites are half occupied and the structure is disordered along the c axis. The transition in the calcium salt occurs between 295 and 275 K and in the strontium salt between 200 and 140 K (but is still incomplete at 4 K).…”