Photochemistry of Cymantrenyl Scorpionates: Formation of a Novel Tritopic Cyclopentadienyl/Scorpionate Hybrid Ligand

The ditopic 1,3-cymantrenediyl-bridged scorpionate K2[(OC)3Mn(C5H3(Bpz3)2)] (3) is available in three steps and good yields starting from cymantrene. Its THF adduct [3(THF)2]2 crystallizes in the form of macrocyclic dimers. Reaction of 3 with BrMn(CO)5 gives access to the trinuclear MnI complex [(OC)3Mn(C5H3(Bpz3Mn(CO)3)2)] (4). Irradiation of 3 in CD3CN for 30 min with a high-pressure mercury lamp (λmax = 510 nm) results in the liberation of one CO molecule and intramolecular Mn-pyrazolyl coordination (mono-ansa-complex K2[(OC)2Mn(C5H3(B(μ-pz)pz2)(Bpz3)]; 5). Upon further irradiation, 5 undergoes demetalation, and the free cyclopentadienyl/scorpionate hybrid ligand K2[C5H4(Bpz3)2] (7) can be isolated from the reaction mixture. 7 has been structurally characterized both as a THF adduct (coordination polymer [7a(THF)2]∞) and as a THF/18-crown-6 adduct (dimer [7a(18-c-6)(THF)2]2).