Synthesis and spectroscopic (1H NMR, ESR) characterization of new aryloxy-Mn(II) complexes: steric control over O- vs phenyl-p-coordination of ArO- ligands (ArO- = C6H5O-, 4-methyl-C6H4O-, 3,5-dimethyl-C6H3O-, 2,6-di-tert-butyl-C6H3O-, 2,6-dimethyl-C6H3O-) to the "Mn(II)Cp"moiety and their reactivity with carbon dioxide