FULL PAPER DOI: 10.1002/ejic.200701103 Novel N,N,O Scorpionate Ligands and Transition Metal Complexes Thereof Suitable for Polymerisation Eike Hübner, [a] Gazi Türkoglu, [a] Marion Wolf, [a] Ulrich Zenneck, [a] and Nicolai Burzlaff* [a] Dedicated to the memory of Professor Swiatoslaw Trofimenko Keywords: Solid phase / Immobilisation / Polymerisation / Tripodal ligands / N,N,O ligands / Tricarbonyl complexes Esterification of 2,2-bis(3,5-dimethylpyrazol-1-yl)-3-hydroxy- propionic acid (2) with methacryloyl chloride led to the new κ 3 -N,N,O ligand 2,2-bis(3,5-dimethylpyrazol-1-yl)-3-meth- acrylato-propionic acid (Hbdmpzmp) (3). The κ 3 -N,N,O coor- dination as known from bis(3,5-dimethylpyrazol-1-yl)acetic acid (Hbdmpza, 1) was proven by syntheses of the complexes [Mn(bdmpzmp)(CO) 3 ](4) and [Re(bdmpzmp)(CO) 3 ](5) and the single-crystal X-ray structure of 4. The methacrylic ester functionality makes 3, 4 and 5 suitable for polymerisation. Thus, copolymerisation of 3 with methyl methacrylate (MMA), a combination of MMA and ethylene glycol dimeth- acrylate (EGDMA) or pure EGDMA led to various solid phases (P1a–P1c, P2, P3a, P3b) with incorporated ligand. Polymer-bound manganese and rhenium tricarbonyl com- plexes could be obtained by copolymerisation of 4 and 5 with MMA as well as by a polymer analogous reaction of P1a with appropriate metal salts. In both cases, the facial tripodal Introduction Bis(pyrazol-1-yl)acetic acids, such as bis(3,5-dimethyl- pyrazol-1-yl)acetic acid (Hbdmpza, 1) introduced 1999 by A. Otero, [1–4] are available in a broad variety of sterically less or stronger demanding, chiral and achiral ligands. [5–8] Complexes of these versatile N,N,O donor ligands with vari- ous transition metal complexes reveal their potential in co- ordination chemistry as scorpionate ligands closely related to hydrotris(pyrazol-1-yl)borate (Tp). [5,6,9,10] The N,N,O binding motif is of particular interest not only as tripodal ligand in organometallic and coordination chemistry but as mimic of the active site of enzymes with a 2-His-1-carboxyl- ate motif as well. [6,11–13] Transition metal complexes of Hbdmpza with zinc and iron have proven to be good struc- tural mimics for such metalloenzymes. [6,12] Due to their [a] Institute of Inorganic Chemistry and Interdisciplinary Centre for Molecular Materials (ICMM), University of Erlangen- Nürnberg, Egerlandstraße 1, 91058 Erlangen, Germany Fax: +49-9131-85-27387 E-mail: burzlaff@chemie.uni-erlangen.de Supporting information for this article is available on the WWW under http://www.eurjic.org or from the author. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Eur. J. Inorg. Chem. 2008, 1226–1235 1226 binding behaviour was evidenced by IR spectra of the poly- mer supported transition metal complexes and the uptake of manganese was proven by AAS measurements. Reaction of the soluble deprotonated solid phase P1a with copper(II) chloride led to a deep-blue solid phase (P-Cu-I). The UV/Vis absorption maximum at 715 nm indicates the copper centres to act as crosslinking agent by a similar binding behaviour as in [Cu(bdmpza) 2 ]. In contrast, the heterogeneous reaction of P1b with copper(II) chloride formed a lime-green solid phase (P-Cu-II). The bathochromic shift of the absorption maximum by 78 nm suggests one-sided bound copper centres. EPR spectra do not show exchange narrowing be- tween the copper centres indicating the metal centres to be far enough apart from each other to prevent magnetic inter- actions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) high binding affinity to metal centres, sterically non-de- manding representatives of the bis(pyrazol-1-yl)acetic acids form bisligand complexes with the most bio-relevant transition metals, featuring octahedral coordination (Scheme 1). [6,14] Further reactions with additional ligands or potential substrates are therefore unfavourable. Scheme 1. The formation of bisligand complexes has been success- fully prevented by the introduction of sterically more de- manding substituents, such as tert-butyl, at the pyrazole rings as we reported on before. [6,12] This results in just one