Trinuclear titanium complexes coordinated by one ligand with three coordination sites have shown properties of mixed valency and a high number of reversible redox steps. Herein we report on the hexaphenyl-substituted derivative (CpTi)(μ-HATNPh) (2). On reaction of 2 with the ferrocenium salt [CpFe]BF, the cationic complexes [(CpTi)(μ-HATNPh)] ( n = 1-3; 3-5) become available in a selective way. Cyclic voltammograms show 10 reversible redox states of the trinuclear species 2 without decomposition. In order to classify the degree of electronic communication between the titanium centers, comproportionation constants K, IVCT bands in NIR spectra, and magnetic measurements were analyzed. These parameters show strong coupling effects between the titanium centers but no full delocalization. In addition, single-crystal X-ray analysis of the neutral complex 2 and its oxidation products (1+ (3), 2+ (4), and 3+ (5)) revealed the geometric structure of the molecule in the solid state. For the cationic species anion-π interactions between the electron-deficient central ring of the HATNPh ligand and BF counterions were found.

Self-assembly reactions with low valent early transition metals, leading to neutral multinuclear complexes are rare. Mostly late transition metals like Pt, Pd or Ru together with Nheterocycles or O-donor-based ligands are used to form supramolecular coordination complexes. This paper reports on selfassembly reactions of low valent titanocene and zirconocene units and five-membered N-heterocycles as bridging ligands. These reactions lead to novel molecular triangles and rectangles with the metal centers marking the vertices. Five different imidazole derivatives and four different metallocene precursors were used. For the first time, molecular triangles and architec-Scheme 1. Molecular quadrangle with pyrazine I and 4,4′-bipyridine II and a combination of both III as bridging ligands.[a]

Multinuclear transition metal complexes bridged by ligands with extended π-electronic systems show a variety of complex electronic transitions and electron transfer reactions. While a systematic understanding of the photochemistry and electrochemistry has been attained for binuclear complexes, much less is known about trinuclear complexes such as hexaphenyl-5,6,11,12,17,18-hexaazatrinaphthylene-tristitanocene [(Cp 2 Ti) 3 HATN(Ph) 6 ]. The voltammogram of [(Cp 2 Ti) 3 HATN(Ph) 6 ] shows six oxidation and three reduction waves. Solution spectra of [(Cp 2 Ti) 3 HATN(Ph) 6 ] and of the electrochemically formed oxidation products show electronic transitions in the UV, visible and the NIR ranges. Density functional theory (DFT) and linear response time-dependent DFT show that the three formally titanium(II) centers transfer an electron to the HATN ligand in the ground state. The optically excited transitions occur exclusively between ligand-centered orbitals. The charged titanium centers only provide an electrostatic frame to the extended π-electronic system. Complete active self-consistent field (CASSCF) calculation on a structurally simplified model compound, which considers the multi-reference character imposed by the three titanium centers, can provide an interpretation of the experimentally observed temperaturedependent magnetic behavior of the different redox states of the title compound in full consistency with the interpretation of the electronic spectra.

The Cover Feature shows the trinuclear [(Cp2Ti)3HATN(Ph)6] complex exhibiting six 1e‐ oxidations and three 1e‐ reductions in voltammetry (Cover art by Luca Gerhards, Carl von Ossietzky University of Oldenburg). First principle calculations on TDDFT and CASSCF levels show that the ground state is formed by spin states of different multiplicity explaining the observed electronic transitions in the UV‐vis‐NIR ranges. More information can be found in the Article by Gunther Wittstock and co‐workers.