title: Fourth generation scorpionates: coordination behavior of a new class of conformationally flexible mixed-donor (pyrazol-1-yl)borates.
abstract: The coordination behavior, the conformational flexibility, and the stability of the novel (pyrazol-1-yl)borate ligands [Ph(pz)B(mu-N(Me))(mu-pz)B(pz)Ph](-) ([L(1)](-)), [Ph(pz)B(mu-O)(mu-pz)B(pz)Ph](-) ([L(2)](-)), and [Ph(pz)B(mu-O)(mu-OB(Ph)O)B(pz)Ph](2-) ([L(3)](2-)) have been experimentally assessed by investigating the following compounds: [Li(thf)L(1)], [Li(thf)L(2)], [Mg(Cl)(thf)(x)L(1)], [Mg(Cl)(thf)(2)L(2)], [Mn(CO)(3)L(2)], K(thf)[Mn(CO)(3)L(3)], [CoCl(2)(HL(1))], [L(1)Co(mu-Cl)(2)CoL(1)], [Zn(Br)L(1)], [Cu(Cl)L(1)], [Cu(Cl)L(2)]. The L(1)-complexes were prepared from a mixture of HL(1) and the appropriate metal salt by addition of a base. HCl elimination from [CoCl(2)(HL(1))], which gives [L(1)Co(mu-Cl)(2)CoL(1)], does not necessarily require the assistance of a base, but happens spontaneously when a solution of the complex is stored at room temperature for several days. K(thf)[Mn(CO)(3)L(3)] was obtained via in situ hydrolysis of HL(1)/[Mn(CO)(5)Br] in the presence of K(2)CO(3). In some other cases, formation of the coordination compounds proceeded with decomposition of a part of the ligand molecules and yielded pyrazole (e.g., [Zn(Cl)(Hpz)L(2)]) or pyrazolide (e.g., [L(2)Co(mu-Cl)(mu-pz)CoL(2)]) complexes. As evidenced by the crystal structure analyses of [Zn(Br)L(1)]/[Mg(Cl)(thf)(2)L(2)]/[Mn(CO)(3)L(2)] on the one hand and [L(1)Mg(mu-Cl)(2)Mg(thf)L(1)]/[Cu(Cl)L(1)]/[Cu(Cl)L(2)](2) on the other, [L(1)](-) and [L(2)](-) are able to adopt both a facial and a meridional conformation. Moreover, while many of the established design principles of scorpionate chemistry are still valid for [L(1)](-), [L(2)](-), and [L(3)](2-), the bonding situation of the central donor moiety (N(Me) in [L(1)](-); O in [L(2)](-), [L(3)](2-)) is distinctly different from the way the pyrazolyl rings are attached to the molecule, so that donor scrambling is not an issue in these [N,N,N] and [N,O,N] mixed-donor ligands.
authors.affiliation: Institut für Anorganische und Analytische Chemie, Goethe-Universität Frankfurt, Max-von-Laue-Strasse 7, D-60438 Frankfurt (Main), Germany.
authors.forename: Elena V
authors.initials: EV
authors.lastname: Mutseneck
authors.forename: Susanne
authors.initials: S
authors.lastname: Bieller
authors.forename: Michael
authors.initials: M
authors.lastname: Bolte
authors.forename: Hans-Wolfram
authors.initials: HW
authors.lastname: Lerner
authors.forename: Matthias
authors.initials: M
authors.lastname: Wagner
mesh_terms: D001881:Borates / Q000737:chemistry*; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008968:Molecular Conformation; D011720:Pyrazoles / Q000737:chemistry*
chemical_list: D001881:Borates; D011720:Pyrazoles; C031280:pyrazole