On Tetrachlorophosphonium Chlorometallates of Rhenium and Molybdenum: Syntheses, Crystal Structures, and Magnetism of [PCl 4 ] 2 [Re 2 Cl 10 ] and [PCl 4 ] 3 [ReCl 6 ] 2 , and the Magnetic Properties of [PCl 4 ] 2 [Mo 2 Cl 10 ]

MoCl 4 , ReCl 4 , and ReCl 5 react with PCl 5 in sealed glass ampoules at temperatures between 220° and 320° to [PCl 4 ] 2 [Mo 2 Cl 10 ] ( 1 ) [PCl 4 ] 2 [Re 2 Cl 10 ] ( 2 ), and [PCl 4 ] 3 [ReCl 6 ] 2 ( 3 ). 2 crystallizes isotypically to the previously reported 1 and the respective titanium and tin containing analogues. The structure (triclinic, P 1, Z  = 1, a  = 897.3(2), b  = 946.0(2), c  = 687.13(9) pm, α = 95.59(2)°, β = 95.80(2)°, γ = 101.07(2)°, V = 565.4(2) 10 6  pm 3 ) is built of tetrahedral [PCl 4 ] + and edge sharing double octahedral [Re 2 Cl 10 ] 2– ions and can be derived from a hexagonal closest packing of Cl – ions with tetrahedral and octahedral holes partially filled by P(V) and Re(IV), respectively. 3 crystallizes isotypically to [PCl 4 ] 3 [PCl 6 ][MCl 6 ] (M = Ti, Sn) (tetragonal, P  4 2 / mbc , Z  = 4, a  = 1496.2(1), c  = 1363.2(2) pm). Because no evidence was found for the presence of [PCl 6 ] – ions, Re in 3 has to be of mixed valency with Re IV and Re V sharing the same crystallographic site. The structure can be derived from a cubic closest packing or alternatively from an only sparsely distorted body centered cubic arrangement of Cl – ions which is rarely found for anion arrays. The tetrahedral and octahedral holes are partially filled by P V and M IV/V , respectively. Magnetic measurements show all three compounds to be paramagnetic and confirm the oxidation state IV for Mo and Re in 1 and 2 and the mixed valence (IV/V) for Re in 3 .