Neutron Counter for Analytical Applications

Layered Zn2[Co(CN)6](CH3COO) double metal cyanide: a two-dimensional DMC phase with excellent catalytic performance

“…Double metal cyanides (DMCs) are inorganic coordination polymers containing two metal atoms connected by cyanide groups. They have been used industrially as solid catalysts for the ring opening polymerization of epoxides since the 1960s, [1][2][3] and their potential as Lewis acid catalysts for other organic transformations such as co-polymerization of epoxides and CO 2 , 4,5 hydroamination, 6-8 transesterication 9 and coupling reactions 10,11 has recently been uncovered. DMCs can generally be described as polynuclear transition metal cyanides with the structural formula M u [M 0 (CN) n ] v $xH 2 O (M and M 0 are two metal cations), which oen crystallize with a cubic unit cell.…”

“…The charge imbalance between these ions produces vacancies that occur at one in three [M 0 (CN) 6 ] 3À sites. [13][14][15] Even though the cubic phase is the most common, the occurrence of other phases, for example a monoclinic and a rhombohedral phase for Zn 3 [Co(CN) 6 ] 2 , has also been observed. 16,17 In all the aforementioned phases, however, the pores are too narrow to allow the diffusion of the majority of aromatic compounds, which for DMC-catalyzed reactions of these molecules signies that the reaction takes place on the outer surface.…”

“…7 In the light of this, many strategies have been suggested in order to increase the accessibility and availability of the catalytically active sites. For example, we recently showed that by dispersing the catalytically active Zn 3 [Co(CN) 6 ] 2 DMC on silica, its activity can be vastly improved in hydroamination and epoxide polymerization reactions because of the increased accessibility of the active sites. 8 Furthermore, Robertson et al 18 proposed layered Co(H 2 O) 2 [M 0 (CN) 4 ] DMCs (M 0 ¼ Ni, Pd or Pt) as high surface area catalysts for the propylene oxide (PO) homopolymerization and PO/CO 2 copolymerization.…”