ABSTRACT
The title compound, [Mn(C7H7)(C6H5O2)]PF6 or [(Cht)Mn(Cp'CO2H)]PF6, with Cht = cyclo-hepta-trienyl and Cp' = C5H4, is an air-stable, purple, heteroleptic, cationic sandwich complex with manganese in oxidation state +I and π-coordinating cyclo-hepta-trienyl and cyclo-penta-dienyl ligands. The latter ligand carries the carb-oxy-lic acid functionality. This 'tromancenium-8-carb-oxy-lic acid' with hexa-fluorido-phosphate as counter-ion represents a rare case of a cationic carb-oxy-lic acid. Structurally, this organometallic carb-oxy-lic acid displays the common motif of planar Osp 2â¯H-Osp 3/Osp 3-Hâ¯Osp 2 hydrogen-bonded carb-oxy-lic acid dimers with anti-oriented metallocenyl moieties, the cationic charge of which is balanced by octa-hedrally shaped hexa-fluorido-phosphate anions. Positional disorder is observed in the cyclo-hepta-trienyl ring and the PF6 - anion.
ABSTRACT
New clathrochelate complexes of manganese, iron and cobalt containing peripheral organometallic manganese moieties cymantrene or tromancenium were synthesized via self-assembly from di/tri-topic dioximes, metal templates and cymantrene/tromancenium boronic acid pinacol esters. These air-stable, highly colored, oligometallic complexes are composed of various combinations of MnIFeIIMnI, MnICoIIMnI, MnIMnIIMnIIMnI and MnICoIICoIIMnI metal assemblies with corresponding complicated magnetic and electrochemical properties. Full spectroscopic and structural characterization by 1H/11B/13C NMR, HRMS, IR, UV-vis, single crystal XRD and CV (cyclic voltammetry) is provided. Tetrametallic complexes containing tromanceniumyl substituents with two CoII or MnII central metals exhibit promising anticancer properties against different tumor cell lines.
ABSTRACT
In continuation of our study of the chemistry of cationic (cycloheptatrienyl)(cyclopentadienyl)manganese(I) sandwich complexes, so-called "tromancenium" salts, we report here on their boron-substituted derivatives focusing on useful boron-mediated synthetic applications. Transmetalation of lithiated tricarbonyl(cyclopentadienyl)manganese ("cymantrene") with boric or diboronic esters affords monoborylated cymantrenes that are converted by advanced high-power LED photosynthesis followed by oxidation with tritylium to their 8-boron-substituted tromancenium complexes. These new functionalized tromancenium salts are fully characterized by 1H/11B/13C/19F/55Mn NMR, IR, UV-vis, HRMS spectroscopy, single-crystal structure analysis (XRD) and cyclic voltammetry (CV). IR spectra were thoroughly analyzed by density functional theory (DFT) on the harmonic approximation in qualitative agreement of calculated vibrations with experimental values. Uncommon chemical reactivity of these borylated tromancenium salts is observed, due to the strongly electron-withdrawing cationic tromancenium moiety. No Suzuki-type cross-coupling reactions proved so far achievable, but unusual copper-promoted amination with sodium azide under microwave irradiation is possible. Diazoniation of aminotromancenium affords an extremely reactive dicationic tromanceniumdiazonium salt, which is too labile for standard Sandmeyer reactions, in contrast to analogous chemistry of cobaltocenium salts. Overall, borylated tromancenium salts display unexpected and intriguing chemical properties with the potential for novel synthetic applications in future work.
