Heteroscorpionate ligands

In our quest to find suitable N,N,0- igands as models for the active sites of the facial 2-His-l-carboxylate triad in iron and zinc containing enzymes, heteroscorpionate ligands like bis(3,5-dimethylpyrazol-... 

Besides direct solid phase fixation, the functional OH-group of 49 may be used for further transformations. Esterification with acetyl chloride at the OH-linker (Scheme 27) leads to 50, providing a heteroscorpionate ligand with the protected OH-linker. An intramolecular hydrogen bridge is found in the X-ray structure [d(01-N21) = 2.478 (3) A] between the carboxylic acid and the pyrazole nitrogen (Fig. 32b). 

To examine the chemical behavior of these new ligands 48-50 in coordination chemistry, tricarbonyl complexes with manganese and rhenium were synthesized from [MnBr(CO)s] and [ReBrCCOls] as described earlier for the other heteroscorpionate ligands (Scheme 28). The purpose of these tricarbonyl complexes was to verify tripodal binding of the solid-bound ligand. The protected OH linker in 50 acts as model for the solid phase bound ligand. 

Ligand 50 reacts with the metal carbonyls as it is well known for the heteroscorpionate ligand Hbdmpza. This is also observed with the allyl-functionalized ligand 48 (Scheme 28). 

Otero, A., Femandez-Baeza, J., Antinolo, A. et al. (2008) Scandium and yttrium complexes supported by NNCp heteroscorpionate ligands synthesis, structure, and polymerization of E-caprolactone. Organometallics, 27, 976. 

Heteroscorpionate ligands based on bis(pyrazolyl)methane systems with various pendant arms as supports for Mg, Zn, Al/ and rare-earth metals have been... 

The Bp ligand is the simplest of all the heteroscorpionate ligands. It is basically bidentate, forming the typical boat-shaped H2B( x-pz)2M ring, in which the pseudoaxial B-H may form an agostic bond with the metal.4,5 [M(Bp)2] complexes of first row transition metals are usually square planar or tetrahedral.6,7 Some octahedral anionic [M(Bp)3]-species of low stability can be also isolated.8,9 Five-coordinate anionic species [MX(Bp)2]- (M = Cr, Mn X = halides or pseudohalides) have been also known.10,11... 

Metal complexes with heteroscorpionate ligands based on the bis(pyra-zol-l-yl)methane moiety Catalytic chemistry 13CCR1806. 

Arene)Ru(II) complexes containing third-generation heteroscorpionate ligands, namely, tris(pyrazolyl)methanesulfonates (Fig. 21.11) have been reported by us together with a detailed characterization, also by X-ray techniques and electrochemical studies that allowed to compare the electron-donor character of the scorpionate and arene ligands (aiene = p-cymene, benzene, hexamethylbenzene) [27]. 

Related tridentate N,N,0 heteroscorpionate ligands provided intricate Ru-vinylidene complexes endowed with a challenging architecture. This strategy was further extended to bi- and tri-metaUic Ru-vinylidene complexes, obtained in high yields, but their metathesis activity has not been Mly illustrated. ... 

Schofield AD, Barros ML, Cushion MG, Schwarz AD, Mountford P. Sodium, magnesium and zinc complexes of mono(phenolate) heteroscorpionate ligands. Dalton Trans. 2009 38 85-96. 

Otero A, Lara-Sanchez A, Femandez-Baeza J, et al. New achiral and chiral NNE heteroscorpionate ligands. Synthesis of homoleptic lithium complexes as well as halide and alkyl scandium and yttrium complexes. Dalton Trans. 2010 39 930-940. 

Sanchez-Barba LF, Alonso-Moreno C, Garces A, et al. Synthesis, structures and ringopening polymerization studies of new zinc chloride and amide complexes supported by amidinate heteroscorpionate ligands. Dalton Trans. 2009 38 8054-8062. 

Castro-Osma JA, Alonso-Moreno C, Lara-Sanchez A, et al. Catalytic behaviour in the ring opening polymerisation of organoaluminiums supported by bulky heteroscorpionate ligands. Dalton Trans. 2014 43 12388-12400. 

The family of heteroscorpionate ligands tailored around acetamidinate fragments disclosed by Smchez-Barba and coworkers constimtes another useful class of nitrogen-containing ancillaries particularly suited to the synthesis of heteroleptic Mg complexes, fri a first study [67], they prepared tbpamd MgR (R = C3H5, 31 ... 

---