Bis(3,5‐dimethyl‐4‐vinylpyrazol‐1‐yl)acetic Acid: A New Heteroscorpionate Building Block for Copolymers that Mimic the 2‐His‐1‐carboxylate Facial Triad

Abstract

AbstractThe new N,N,O ligand bis(3,5‐dimethyl‐4‐vinylpyrazol‐1‐yl)acetic acid (Hbdmvpza) (4) suitable for copolymerisation was synthesised in a multi‐step synthesis starting from bis(3,5‐dimethylpyrazol‐1‐yl)methane (1). The κ3‐N,N,O facial coordination behaviour of 4 was verified by synthesis and characterisation of the tricarbonyl compounds [Mn(bdmvpza)(CO)3] (5) and [Re(bdmvpza)(CO)3] (6), the ruthenium bisphosphane complex [Ru(bdmvpza)Cl(PPh3)2] (7), as well as the complex [Cu(bdmvpza)2] (8). Copolymerisation of 4 with methyl methacrylate (MMA) or ethylene glycol dimethacrylate (EGDMA) led to solid phases P1a, P1b and P2 with different amounts of incorporated ligand 4. Furthermore, a homopolymer H1 of ligand 4 was successfully synthesised. Copolymer‐bound manganese and rhenium tricarbonyl complexes P1a‐Mn, P1a‐Re, P2‐Mn and P2‐Re have been obtained by reaction of P1a and P2 with the metal precursors [MnBr(CO)5] and [ReBr(CO)5], respectively. The κ3‐N,N,O coordination of the manganese and rhenium centres was verified by IR spectroscopy and the amount of incorporated metal complex was determined by AAS or ICP‐AES measurements. Treatment of the deprotonated copolymer P1a or P2 with copper(II) or iron(II) led to polymers P1a‐Cu, P1a‐Fe and P2‐Fe. A bathochromic shift in the UV spectrum of P1a‐Cu compared to the absorption maximum of the homogeneous complex 8 by 64 nm indicates copper centres with one ligand moiety bound only. AAS analysis of P1a‐Fe and P2‐Fe show that up to 64 % of the ligand sites can be accessed withiron(II). Furthermore, two 2‐oxocarboxylato complexes [Ru(bdmvpza)(BF)(PPh3)] (9) (BF = benzoylformato) and [Ru(bdmvpza)(NOG)(PPh3)] (10) (NOG = N‐oxalylglycine) have been synthesised that mimic the shape of the active sites of 2‐oxoglutarate dependent iron oxygenases. The successful copolymerisation of 9 and 10 with EGDMA was proven by UV spectroscopy.