The preparation of new stable half-sandwich transition metal complexes, having a bulky cyclopentadienyl ligand C5(C6H4-4-Et)5 (Cp(Ar1)) or C5(C6H4-4-nBu)5 (Cp(Ar2)), is reported. The tetrahydrofuran (THF) adduct [Cp(Ar1)Fe(μ-Br)(THF)]2 (1a) was synthesized by reacting K[Cp(Ar1)] with [FeBr2(THF)2] in THF, and its molecular structure was determined by X-ray crystallography. Complex 1a easily loses its coordinated THF molecules under vacuum to form the solvent-free complex [Cp(Ar1)Fe(μ-Br)]2 (1b). The analogous complexes [Cp(Ar1)Co(μ-Br)]2 (2), [Cp(Ar1)Ni(μ-Br)]2 (3), and [Cp(Ar2)Ni(μ-Br)]2 (4) were synthesized from CoBr2 and [NiBr2(1,2-dimethoxyethane)]. The mononuclear, low-spin cobalt(III) and nickel(III) complexes [Cp(Ar2)MI2] (5, M = Co; 6, M = Ni) were prepared by reacting the radical Cp(Ar2) with NiI2 and CoI2. The complexes were characterized by NMR and UV-vis spectroscopies and by elemental analyses. Single-crystal X-ray structure analyses revealed that the dimeric complexes 1a, 1b, and 3 have a planar M2Br2 core, whereas 2 and 4 feature a puckered M2Br2 ring.

Au(I) complexes are studied as precursors for focused electron beam induced processing (FEBIP). FEBIP is an advanced direct-write technique for nanometer-scale chemical synthesis. The stability and volatility of the complexes are characterized to design an improved precursor for pure Au deposition. Aurophilic interactions are found to play a key role. The short lifetime of ClAuCO in vacuum is explained by strong, destabilizing Au–Au interactions in the solid phase. While aurophilic interactions do not affect the stability of ClAuPMe3, they leave the complex non-volatile. Comparison of crystal structures of ClAuPMe3 and MeAuPMe3 shows that Au–Au interactions are much weaker or partially even absent for the latter structure. This explains its high volatility. However, MeAuPMe3 dissociates unfavorably during FEBIP, making it an unsuitable precursor. The study shows that Me groups reduce aurophilic interactions, compared to Cl groups, which we attribute to electronic rather than steric effects. Therefore we propose MeAuCO as a potential FEBIP precursor. It is expected to have weak Au–Au interactions, making it volatile. It is stable enough to act as a volatile source for Au deposition, being stabilized by 6.5 kcal/mol. Finally, MeAuCO is likely to dissociate in a single step to pure Au.

Samarocene sandwich complexes with superbulky penta-arylcyclopentadienyl ligands have been prepared and were structurally characterized: [(4-EtC 6 H 4 ) 5 C 5 ] 2 Sm (1) and [(4-iPrC 6 H 4 ) 5 C 5 ] 2 Sm (2). Analogous to the previously reported synthesis of [(4-nBuC 6 H 4 ) 5 C 5 ] 2 Sm, reaction of (DMAT) 2 Sm• (THF) 2 (DMAT = 2-Me 2 N-α-Me 3 Si-benzyl) and the appropriate Ar 5 C 5 H ligand gave 1 (66% yield) and 2 (59% yield). In contrast to the high reactivity of Cp* 2 Sm, complex 1 has been shown to be surprisingly stable toward reaction with a large variety of reagents. Even under forcing conditions, no reaction with N 2 , CO, CO 2 , pyrazine, trans-stilbene, pyridine, P 4 , and benzophenone was observed. Complex 1 reacts with cuminil ArC(O)C(O)Ar (Ar = 4-iPrC 6 H 4 ) to yield the Sm(III) sandwich complex [(4-EtC 6 H 4 ) 5 C 5 ] 2 Sm[ArC(O)C(O)Ar] (3), which could be isolated in 83% yield as a dark-red crystalline material. Complex 2 reacts with oxygen in the presence of phenazine to yield the bimetallic Sm(III) complex [(4-iPrC 6 H 4 ) 5 C 5 Sm(η 1 -phenazine)] 2 (μ:η 2 -η 2 -O 2 ) 2 (4) in 25% yield as dark-red crystals. The unusually high redox-stability of deca-arylsamarocenes originates from steric hindrance of the Sm metal center.

The 17 valence electron (VE) open-shell nickel gallanediyl complex [Cp(Ar)Ni{Ga(nacnac)}] (3, Ar = C5(C6H4-4-Et)5, nacnac = HC[C(Me)N(C6H3-2,6-iPr2)]2), having an unsupported Ni-Ga bond, was synthesized from [Cp(Ar)Ni(μ-Br)]2 (1) by reducing the adduct [Cp(Ar)Ni(μ-Br){Ga(nacnac)}] (2) or, alternatively, trapping the "Cp(Ar)Ni(I)" synthon with Ga(nacnac); spectroscopic and DFT studies showed that the single unpaired electron in 3 resides mainly at the Ni center.

Attempts to stabilise a TmII metal centre with the bulky β-diketiminate ligand HC[C(Me)=N(DIPP)]2 (BDI) failed (DIPP, 2,6-diisopropylphenyl). Reaction of TmI2 and 2 equiv. (BDI)K gave the TmIII complex (BDI)(BDI-H)Tm (1) in which (BDI-H)2− is a doubly deprotonated ligand. However, following the same route, (BDI)2Sm (2) was isolated in 48% crystalline yield. Complex 2 is highly soluble in aromatic solvents or alkanes and was reacted with various reagents like phenazine, PhSSPh, O2, NO, cuminil and fluorenone. This led to isolation and structural characterisation of the following SmIII complexes: [(BDI)2Sm]2(μ-phenazine) (3), [(BDI)Sm(SPh)(μ-SPh)]2 (4), (BDI)(BDI-H)Sm (5a), (BDI)2Sm(OC13H8) (6) and (BDI)2Sm(NO2) (7). The rich redox reactivity of (BDI)2Sm (2) and its very high solubility in apolar solvents like hexane make it an attractive reducing agent in synthesis.