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

The ditopic 1,3-cymantrenediyl-bridged scorpionate K-2[(OC)(3)Mn(C5H3(BPz(3))(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 Mn-I complex [(OC)(3)Mn(C5H3(Bpz(3)Mn(CO)(3))(2)] (4). Irradiation of 3 in CD3CN for 30 min with a high-pressure mercury lamp (lambda(max) = 510 nm) results in the liberation of one CO molecule and intramolecular Mn-pyrazolyl coordination (mono-ansa-complex K-2[(OC)(2)Mn(C5H3(B(mu-pz)pz(2))(BPz(3))]; 5). Upon further irradiation, 5 undergoes demetalation, and the free cyclopentadienyl/scorpionate hybrid ligand K-2[C5H4(BPz(3))(2)] (7) can be isolated from the reaction mixture. 7 has been structurally characterized both as a THF adduct (coordination polymer [7a(THF)(2)](infinity)) and as a THF/18-crown-6 adduct (dimer [7a(18-c-6)(THF)(2)](2)).