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The reaction between an excess of Fe(CO) 5 with {Cryptand(K + )}(C 60 •- ) produced the salt {Cryptand(K + )} 2 {[Fe(CO) 2 ] 2 -μ 2 -η 2 :η 2 -η 2 :η 2 -(C 60 ) 2 } 2- ·4C 6 H 4 Cl 2 ( 1 ) containing negatively charged iron-bridged fullerene dimers. In these dimers, the C 60 cages are linked via two Fe(CO) 2 fragments, forming short Fe-C(C 60 ) bonds with a length of 2.070(3) Å and via two intercage C-C bonds with a length of 1.566(3) Å. Interfullerene center-to-center distance is short, being 9.02 Å. Thus, the coordination-induced dimerization of fullerenes is observed in 1 . The dimer is negatively charged, with additional negative electron density mainly localized on iron atoms and, to a lesser extent, on the C 60 cages, as revealed by optical and electron paramagnetic resonance spectra. These dimers have a diamagnetic singlet ground state with a small singlet-triplet gap of 25 K; consequently, they transfer to a paramagnetic state with two S = 1/2 spins per dimer above 50 K. Previously, different dimers with isomeric structures were obtained starting from {Cryptand(K + )}(C 60 •- ) and Fe 3 (CO) 12 . However, these dimers exhibit diamagnetic properties, owing to the formation of a Fe-Fe bond. In contrast, in dimer 1 , the Fe atoms are positioned too far apart to form such a bond, preserving the spin on Fe. We assume that both dimers are formed through the same [Fe(CO) 3 ](C 60 •- ) intermediate, but the subsequent interaction of this intermediate with Fe 3 (CO) 12 or its dimerization yields different dimers. Therefore, the starting carbonyls can control the structures and properties of the resulting dimers.

The interaction of {Cryptand(K + )}(C 60 •- ) with Fe 3 (CO) 12 produced {Cryptand(K + )} 2 {Fe(CO) 2 - μ 2 - η 2 , η 2 -C 60 } 2 2- ·2.5C 6 H 4 Cl 2 ( 1 ) as the first negatively charged iron-bridged fullerene C 60 dimer. The bridged iron atoms are coordinated to two 6-6 bonds of one C 60 hexagon with short and long C(C 60 )-Fe bonds with average lengths of 2.042(3) and 2.088(3) Å. Fullerenes are close to each other in the dimer with a center-to-center interfullerene distance of 10.02 Å. Optical spectra support the localization of negative electron density on the Fe 2 (CO) 4 units, which causes a 50 cm -1 shift of the C≡O vibration bands to smaller wavenumbers, and the C 60 cages. Dimers are diamagnetic and electron paramagnetic resonance silent and have a singlet ground state resulting from the formation of an Fe-Fe bond in the dimer with a length of 2.978(4) Å. According to density functional theory calculations, the excited triplet state is higher than the ground state by 6.5 kcal/mol. Compound 1 shows a broad near-infrared band with a maximum at 970 nm, which is attributable to the charge transfer from the orbitals localized mainly on iron atoms to the C 60 ligand.

Metal complexes of trithiadodecaazahexaphyrin (Hhp) that contain M II 3 O clusters inside a π-extended trianionic (Hhp 3- ) macrocycle have been prepared. Studies of the magnetic properties of Ni II 3 O(Hhp) and Cu II 3 O(Hhp) reveal a diamagnetic and EPR-silent trianionic (Hhp 3- ) macrocycle and diamagnetic Ni II 3 (O 2- ) or paramagnetic Cu II 3 (O 2- ) tetracations. The positive charge of M II 3 O(Hhp) is compensated by one acetate anion {M II 3 O(Hhp)} + (CH 3 CO 2 - ). The three-electron reduction of {M II 3 O(Hhp)} + yields {cryptand(Cs + )} 2 {Ni II 2 Ni I O(Hhp 5- )} 2- ·2C 7 H 8 ( 1 ) and {cryptand(Cs + )} 2 {Cu II 3 O(Hhp •6- )} 2- ·C 7 H 8 ( 2 ) crystalline salts. The magnetic properties of 1 reveal the formation of Hhp 5- and the reduction of nickel(II) to the paramagnetic Ni I ion ( S = 1/2), which is accompanied by the formation of the {Ni II 2 Ni I O(Hhp 5- )} 2- dianion. As a result, the magnetic moment of 1 is 1.68 μ B in the 20-220 K range, and a broad EPR signal of Ni I was observed. The Hhp 5- macrocycle has a singlet ground state, but the increase in the magnitude of the magnetic moment of 1 above 220 K is attributed to the population of the triplet excited state in Hhp 5- . The {Ni II 2 Ni I O(Hhp 5- )} 2- dianion is transferred from the doublet excited state to the quartet excited state with an energy gap of 1420 ± 50 K. Salt 1 also shows an unusually strong low-energy NIR absorption, which was observed at 1000-2200 nm. In 2 , a highly reduced Hhp •6- radical hexaanion ( S = 1/2) coexists with a Cu II 3 (O 2- ) cluster ( S = 1/2) in the {Cu II 3 O(Hhp •6- )} 2- dianions. The dianions have a triplet ground state with antiferromagnetic exchange between two S = 1/2 spins with J = -6.4 cm -1 . The reduction of Hhp in both salts equalizes the initially alternated C-N bonds, supporting the increase in the Hhp macrocycle electron delocalization.

Reduction of {Zn II (TPyP)} to the {Zn II (TPyP)} 2- dianions (TPyP: tetra(4-pyridyl)porphyrin) in the presence of Bu 3 MeP + allows one to observe the C-H bond cleavage in the methyl group of Bu 3 MeP + to form (Bu 3 MeP + ){Zn II (CH 2 PBu 3 )(TPyPH)} - ·0.337C 6 H 5 CH 3 ( 1 ). Salt 1 is the first coordination complex of neutral CH 2 PBu 3 ylide and metalloporphyrin. The released hydrogen atom attacks the meso -carbon atom of TPyP 4- forming a TPyPH 3- macrocycle related to phlorins. Decreased symmetry of the TPyPH 3- allows the observation of a strong NIR absorption. We discuss the molecular structure, optical, and magnetic properties of 1 together with its formation pathways.

A diamagnetic complex, {(cis-indigo-N,N) 2- (Cp*Ir III )} (1), in which deprotonated cis-indigo dianions coordinate an iridium center through two nitrogen atoms was obtained. By employment of the ability of the iridium center in 1 to coordinate an additional ligand, the complex [(Bu 4 N + ) 2 {[Sn II (Pc •3- )](cis-indigo-N,N) 2- Cp*Ir III } •- 2 ·0.5(H 2 Indigo)·2.5C 6 H 4 C l2 (2), which has two functional ligands coordinating an Ir III center, was obtained. This complex has a magnetic moment of 1.71 μ B at 300 K, in accordance with an S = 1/2 spin state. The spin density is mainly delocalized over the Pc •3- macrocycle and partially on (cis-indigo-N,N) 2- . Due to an effective π-π interaction, a thermally activated charge transfer from [Sn II (Pc •3- )] •- to (cis-indigo-N,N) 2- is observed, with an estimated Gibbs energy (-ΔG°) of 9.27 ± 0.18 kJ/mol. The deprotonation of indigo associated with the coordination of Ir III by the indigo releases H + ions, which protonate noncoordinating indigo molecules to produce leuco cis-indigo (H 2 Indigo). One H 2 indigo links two (cis-indigo-N,N) 2- dianions in 2 to produce strong N-H···O═C and O-H···O═C hydrogen-bonding interactions.

Coordination of two bridging cobalt atoms to fullerenes by the η(2) type in {Co(dppe)}2{μ2-η(2):η(2)-η(2):η(2)-[(C60)2]}·3C6H4Cl2 [1; dppe = 1,2-bis(diphenylphosphino)ethane] triggers fullerene dimerization with the formation of two intercage C-C bonds of 1.571(4) Å length. Coordination-induced fullerene dimerization opens a path to the design of fullerene structures bonded by both covalent C-C bonds and η(2)-coordination-bridged metal atoms.