A series of titanium amidinato complexes were synthesized by stoichiometric insertion reactions of carbodiimides into bis(pi-eta 5:sigma-eta 1-pentafulvene)titanium complexes. NMR studies and single-crystal X-ray diffraction showed kappa 1N coordination of the former carbodiimides to the metal center. DFT calculations were performed, confirming the clear preference for a single nitrogen atom coordinating to the metal center with a high energy transition state for the formation of a chelating heteroallyl ligand. Depending on the pentafulvene ligand, additional insertion reactions of carbodiimides into the remaining Ti-Cexo bond were observed. This allows for a stepwise insertion of the corresponding carbodiimides and offers the possibility to further functionalize the complexes. The reactivity of the remaining pentafulvene ligand is further demonstrated in reactions with H-acidic and multiple bond substrates.

The syntheses of side-on Ti(III) triazenido complexes via the ethylene complexes Cp*Ti(eta(2)-C2H4)(eta(5)-C5H4CR2H) and side-on Ti(IV) triazenido complexes via bis(pi-eta(5) : sigma-eta(1)-pentafulvene) titanium complexes are reported. The deprotonation of the triazene N - H function occurs under mild conditions either by reduction of the proton to hydrogen mediated via the masked titanocene (II) of the ethylene complex or by the nucleophilic Cexo atom of the pentafulvene moiety. The structures of the paramagnetic Ti(III) complexes were confirmed by single-crystal X-ray diffraction, whereas the diamagnetic Ti(IV) complexes were characterized via NMR spectroscopy and additionally, Ti2 c by single-crystal X-ray diffraction. The structure of complex Ti2 c reveals one of the smallest bent angles known for titanium pentafulvene complexes.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Bis(eta(5):eta(1)-(di-para-tolyl)pentafulvene)niobium chloride (1) reacts with methyl lithium via salt metathesis to the methylated bis(pentafulvene)niobium complex 2, and with lithium 2,6-diisopropylanilide addition and subsequent N-H bond activation to the imido mono(pentafulvene)niobium complex 3. Avoiding the competing protonation of the chloride, bis(pentafulvene)niobium complex 2 reacts with primary aromatic and aliphatic amines to form terminal niobocene imido complexes, and with water to form the analog terminal oxo complex. Secondary methyl amines undergo a simultaneous N-H and C-H activation to form niobaaziridines under mild conditions. In contrast to other reported examples, 3 can be employed to investigate the uncontested reactivity of mono(pentafulvene)niobium complexes. Reaction with 4-tert-butylphenol selectively yields a niobocene phenolate complex. Unprecedented for mono(pentafulvene)niobium complexes, treating 3 with multiple-bond-containing substrates (nitriles, isocyanates) smoothly results the insertion into the Nb-C-exo sigma-bond, forming the corresponding alkylidene amido and imidato complexes.

Addition of the parent allene H2C=C=CH2 to the bis(pentafulvene)titanium complexes Ti1a,b results in the formal nucleophilic attack of one of the exocyclic quaternary carbon atoms (C-q,C-exo) of one pentafulvene ligand at the central propa1,2-diene carbon atom to form the titanium complexes Ti2a,b bearing both one intact pentafulvene ligand and a bidentate cyclopentadienyl-/allyl-based ligand, whose functionalities are spaced by a C-1 linker. Investigations into the nature of the Ti-allyl interaction is established by multinuclear NMR spectroscopy, single crystal X-ray diffraction, and combined computational studies. A first glimpse of the reactivity of Ti2a,b is demonstrated showing that both the intact pentafulvene ligand and the allyl unit can be modified.