As a target, Green Chemistry is the whole process aiming at producing chemical products that reduce or eliminate the use or generation of hazardous substances. Green chemistry goes beyond the synthesis and applies across the life cycle of a chemical product, including its use, and ultimate disposal.
By the judicious study of a desired compound, in our case a metallacarborane with a characteristic 3D shape, and with the formula [3,3’-Co(1,2-C2B9H11)2]− has been possible by applying the concepts of green chemistry to create an alternative procedure to avoid hazardous substances. The process was designed to achieve the targeted metallacarborane at the shortest time while reducing waste and demand on energy.
In the paper cited below, a new, fast and environmentally-friendly solid state reaction for the syntheses of cobaltabis(dicarbollide) derivatives, [3,3’-Co(1,2-R2-1,2-C2B9H9)2]− (R and R’= H, alkyl, aryl) is presented. Our approach is a significant improvement on the traditional syntheses in solution in both speed of reaction and generated yield. We demonstrate that the [3,3’-Co(1,2-C2B9H11)2]− building reaction works well with starting plain, single or double Ccluster-substituted nido [7,8-C2B9H12]- clusters. However, care has to be taken when β-hydride elimination may take place because in this case the resulting [Co(C2B9H11)2]− derivative may be different to the expected one based on the precursor nido cluster due to the β-hydride elimination, as commonly occurs in organometallic chemistry. The presence of substituents bearing a free pair of electrons also influences the complex formation. Meta-isomers also give rise to the corresponding cobaltabis(dicarbollide), [3,3’-Co(1,7-C2B9H11)2]−, but in this case, the reaction time needs to be increased. A suggested mechanism of the complexation reaction is proposed, based on identifying the chemical nature of the evolved gas, the pH of the mixture, the crystal structure of the target complex and the absence of Co2+ dismutation.
The fact that metallacarboranes can find many applications in materials, energy, catalysis, sensors/biosensors and medicine, among others makes this innovative, straightforward and clean route for their flash synthesis very valuable.
3,2,1 and stop! An innovative, straightforward and clean route for the flash synthesis of metallacarboranes
Ines Bennour, Ana M. Cioran, Francesc Teixidor, Clara Viñas
Green Chemistry 21, 1925, 2019
Figure: Schematic view of the valuable 3,2,1 and stop! synthetic procedure to achieve 3D shaped metallacarborane [Co(C2B9H11)2]− derivatives.