13446-57-6Relevant articles and documents
Solid state synthesis, structures and redox properties of the new [Mo 6Bri7TeiBra 6]3- and [Mo6Bri7Se iBra6]3- octahedral cluster units: Crystallochemistry of the Rb2+
Kirakci, Kaplan,Cordier, Stephane,Hernandez, Olivier,Roisnel, Thierry,Paul, Frederic,Perrin, Christiane
, p. 3117 - 3129 (2005)
The solid state synthesis and the structure of the Rb2Mo 6Bri8Bra6 bromide (C2/c, a=20.376(5)A, b=15.297(5)A, c=9.757(5)A, β=115.969(5) °, Z=4, R1=0.037; wR2=0.057) and Rb2+xMo 6Bri8-xYi xBra6 chalcohalides built up from molybdenum octahedral clusters (x=0.5 for Y=Te; 0.25≤x≤0.7 for Y=Se) are presented. The crystallochemistry results are based on combined single-crystal and powder X-ray diffraction investigations from several preparations with different loaded compositions. A continuous solid state solution is evidenced between the two limit compositions Rb2.25Mo6Br13.75Se 0.25 (Pn-3, a=13.999(2)A, Z=4, R1=0.039; wR2=0.058) and Rb 2.7Mo6Br13.3Se0.7 (Pn-3, a=14.144(2)A, Z=4, R1=0.029; wR2=0.048). On the other hand, in the case of tellurium (data: Rb2.5Mo6Br13.5Te 0.5, Pn-3, a=14.0936(5)A, Z=4, R1=0.028; wR2=0.048) no solid state solution is observed as previously reported for Rb2.5Re 6S6.5Cl7.5 and K2.5Re 6S6.5Br7.5. The structural features that act in the stabilization of the new [Mo6Br13Y]3- units (Y=Se, Te) are evidenced and discussed by comparison with those obtained for related compounds in particular in Rb2.5Re6S 6.5Cl7.5, K2.5Re6S 6.5Br7.5, and A2W6Br14 series (A=monovalent cation). The substitution of chalcogen for halogen strongly modifies the intrinsic properties of the M6L14 unit. Indeed, the electrochemistry performed on the [Mo6Br 13Y]3- unit after dissolution of the crude solid samples isolated reveals a new and chemically reversible oxidation process at E1/2=0.46V vs. SCE for [Mo6Br13Se]3- whilst a similar oxidation process centred at 0.38 V is observed for [Mo6Br 13Te]3-.
