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See detailUnderstanding ferroelectricity in layered perovskites: new ideas and insights from theory and experiments
Benedek, Nicole; Rondinelli, James; Djani-Ait, Hania ULg et al

in Dalton Transactions (Cambridge, England : 2003) (2015), 44(23), 10527-10890

ABO3 perovskites have fascinated solid-state chemists and physicists for decades because they display a seemingly inexhaustible variety of chemical and physical properties. However, despite the diversity ... [more ▼]

ABO3 perovskites have fascinated solid-state chemists and physicists for decades because they display a seemingly inexhaustible variety of chemical and physical properties. However, despite the diversity of properties found among perovskites, very few of these materials are ferroelectric, or even polar, in bulk. In this Perspective, we highlight recent theoretical and experimental studies that have shown how a combination of non-polar structural distortions, commonly tilts or rotations of the BO6 octahedra, can give rise to polar structures or ferroelectricity in several families of layered perovskites. We discuss the crystal chemical origin of the polarization in each of these families – which emerges through a so-called ‘trilinear coupling’ or ‘hybrid improper’ mechanism – and emphasize areas in which further theoretical and experimental investigation is needed. We also consider how this mechanism may provide a generic route for designing not only new ferroelectrics, but also materials with various other multifunctionalities, such as magnetoelectrics and electric field-controllable metal-insulator transitions. [less ▲]

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See detailDithiocarboxylate complexes of ruthenium(II) and osmium(II)
Naeem, Saira; Thompson, Amber L; White, Andrew J P et al

in Dalton Transactions (Cambridge, England : 2003) (2011), 40(14), 3737-3747

The ruthenium(II) complexes [Ru(R)(kappa(2)-S2C center dot IPr)(CO)(PPh3)(2)](+) (R = CH=CHBut, CH CHC6H4Me-4, C(C CPh)=CHPh) are formed on reaction of IPr center dot CS2 with [Ru(R)Cl(CO)(BTD)(PPh3)(2 ... [more ▼]

The ruthenium(II) complexes [Ru(R)(kappa(2)-S2C center dot IPr)(CO)(PPh3)(2)](+) (R = CH=CHBut, CH CHC6H4Me-4, C(C CPh)=CHPh) are formed on reaction of IPr center dot CS2 with [Ru(R)Cl(CO)(BTD)(PPh3)(2)] (BTD = 2,1,3-benzothiadiazole) or [Ru(C(C CPh)=CHPh)Cl(CO)(PPh3)(2)] in the presence of ammonium hexafluorophosphate. Similarly, the complexes [Ru(CH=CHC6H4Me-4)(kappa(2)-S2C center dot ICy)(CO)(PPh3)(2)](+) and [Ru(C(C CPh)=CHPh)(kappa(2)-S2C center dot ICy)(CO)(PPh3)(2)](+) are formed in the same manner when ICy center dot CS2 is employed. The ligand IMes center dot CS2 reacts with [Ru(R)Cl(CO)(BTD)(PPh3)(2)] to form the compounds [Ru(R)(kappa(2)-S2C center dot IMes)(CO)(PPh3)(2)](+) (R = CH=CHBut, CH=CHC6H4Me-4, C(C CPh)=CHPh). Two osmium analogues, [Os(CH CHC(6)H4(M)e-4)(kappa(2)-S2C center dot IMes)(CO)(PPh3)(2)](+) and [Os(C(C CPh)=CHPh)(kappa(2)-S2C center dot IMes)(CO)(PPh3)(2)](+) were also prepared. When the more bulky diisopropylphenyl derivative IDip center dot CS2 is used, an unusual product, [Ru(kappa(2)-SC(H)S(CH= CHC6H4Me-4)center dot IDip)Cl(CO)(PPh3)(2)](+), with a migrated vinyl group, is obtained. Over extended reaction times, [Ru(CH=CHC6H4Me-4)Cl(BTD)(CO)(PPh3)(2)] also reacts with IMes center dot CS2 and NH4PF6 to yield the analogous product [Ru{kappa(2)-SC(H)S(CH=CHC6H4Me-4)center dot IMes}Cl(CO)(PPh3)(2)](+) via the intermediate [Ru(CH=CHC6H4Me-4)(kappa(2)-S2C center dot IMes)(CO)(PPh3)(2)](+). Structural studies are reported for [Ru(CH=CHC6H4Me-4)(kappa(2)-S2C center dot IPr)(CO)(PPh3)(2)]PF6 and [Ru(C(C CPh)=CHPh)(kappa(2)-S2C center dot ICy)(CO)(PPh3)(2)]PF6. [less ▲]

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