Clara Viñas

Carboranylphosphinic acids a new class of purely inorganic ligands: Aiming towards future multifunctional materials

Clara Viñas,¹* Francesc Teixidor¹ and Elena Oleshkevich.¹

¹Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus de la UAB, E-08193, Bellaterra (Barcelona), Spain.

clara@icmab.es

Organophosphorous compounds are of remarkable technological interest, e.g. organophosphines are important ligands in catalysis and asymmetric synthesis; phosphonates have found applications as, among others, herbicides and medicine. Phosphinates have also been applied as herbicides. Both phosphonates and phosphinates are good chelating agents of interest as metal extractants. In the organophosphorus compounds, the carbon atom linked to the phosphorus is part of an organic functional group. In this work, the C is a member of a boron cluster: a carborane, which are icosahedral boron clusters presenting 3D aromatic character,¹ high thermal and chemical stability, hydrophobicity and low toxicity in biological systems (Figure 1).

Recently purely inorganic carboranyl phosphinates were prepared, and the influence of the cluster on the reactivity of phosphinate group was studied.² Carboranylphosphinic acids are principally new coordination reagents in boron cluster chemistry. Although, few carboranylphosphinic acids have been previously synthesized, their coordination chemistry, together with their physical and chemical properties, remained unexplored. Obviously, no examples of carboranylphosphinic acid complexes have been found; hence no coordination polymers with this motif have been described until now.

Having all this in mind and our previous research on the coordination chemistry of 1-COOH-2-R-1,2-closo-C₂B₁₀H₁₀(R= Me, H) with Mn²⁺, Cu²⁺ and Co²⁺,³ we proceed synthesizing air-stable fully inorganic coordination polymers of Mn²⁺ and Cd²⁺ as well as the molecular complexes with Zn²⁺, Ni²⁺ and Co²⁺using the carboranylphosphinate ligand 1-P(H)O(OH)-1,7-closo-C₂B₁₀H₁₂.⁴ Then, the ability of carboranylphosphinates to coordinate on surface of magnetite/maghemite (Fe₃O₄/γ-Fe₂O₃) nanoparticles,⁵ as well as its ability to control the size of CdSe Quantum Dots was discovered.⁶

Figure 1. Schematic representation of 3D carboranylphosphinic acid and the magnetic nanoparticles stabilized with the pure inorganic phosphinic acid.

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