Synthesis and transition metal complexes of novel N,N,O scorpionate ligands suitable for solid phase immobilisation

Introduction of an allyl or a hydroxymethyl group to bis(3,5-dimethylpyrazol-1-yl) acetic acid (1) at the bridging carbon atom leads to the new tripodal N,N,O ligands 2,2-bis(3,5-di-methylpyrazol-1-yl)pent-4-enoic acid (Hbdmpzpen) (2) and 2,2-his (3,5 -dimethylpyrazol-1-yl)-3-hydroxypropionic acid (Hbdmpzhp) (3). These hgands exhibit similar chemical behaviour to that of 1, but they have the additional possibility to be immobilised to a solid phase. Esterification of the hydroxymethyl linker of 3 yields 2,2-bis(3,5-dimethylpyrazol-1-yl)-3-acetatopropionic acid (Hbdmpzap) (4). The molecular structures of 2, 3 and 4 all exhibit intramolecular hydrogen bridges. Introduction of a hydroxymethyl group to methyl bis (3,5-dimethylpyrazol-1 -yl) acetate (5) yields methyl 2,2-bis(3,5-dimethylpyrazol-1-yl)-3-hydroxypropionate (Mebdmpzhp) (6), which can be immobilised on Merrifield polymer to yield modified resin P-6. To investigate the reactivity of these new ligands, manganese and rhenium complexes of 2, 3 and 4 have been studied. The molecular structures of the two manganese complexes [Mn(bdmpzpen)-(CO)(3)] (7) and [Mn(bdmpzap) (CO)(3)](8) have been confirmed by single-crystal X-ray structure determination. Saponification of polymer resin P-6 and subsequent reaction with [ReBr(CO)(5)]yields rhenium. tricarbonyl complexes anchored on Merrifield polymer (P-Re). Solid phase immobilisation of the [Mn(bdmpzpen)(CO)(3)](7) and [Re(bdmpzpen)(CO)(3)](9) complexes on 3-mercaptopropyl functionalised silica is initialised by AIBN. The tripodal coordination of manganese and rhenium in these functionalised Merrifield resins (P-Re) and silica (S-Mn, S-Re) is proven by a single A, and two E signals in the IR spectra that are typical for unsymmetrical "piano stool" type carbonyl complexes. (c) Wiley-VCH Verlag GmbH & Co.