Because of the toxicity of lead, searching for a lead-free halide perovskite semiconducting material with comparable optical and electronic properties is of great interest. Rare-earth-based halide perovskite represents a promising class of materials for this purpose. In this work, we demonstrate the solution-phase synthesis of single-crystalline CsEuCl3 nanocrystals with a uniform size distribution centered around 15 nm. The CsEuCl3 nanocrystals have photoluminescence emission centered at 435 nm, with a full width at half-maximum of 19 nm. Furthermore, CsEuCl3 nanocrystals can be embedded in a polymer matrix that provides enhanced stability under continuous laser irradiation. Lead-free rare-earth cesium europium halide perovskite nanocrystals represent a promising candidate to replace lead halide perovskites.

A range of new iminoborylcomplexes of the type [L(n)M-B[triple bond]N-R], which are isoelectronic with sigma-alkynyl complexes [L(n)M-C[triple bond]C-R], was obtained by systematically varying the metal M, the coligands L, and the nitrogen bound substituent R. Selected examples include, for example, trans-[(Cy3P)2(Br)Pt(B[triple bond]N iBu)], which is characterized by a sterically less demanding N-R group or the unprecedented rhodium species cis,mer-[(Br)2(Me3P)3Rh(B[triple bond]NSiMe3)]. All compounds were fully characterized in solution by multinuclear NMR spectroscopy and, where appropriate, in the solid state by X-ray crystallography. Subsequent reactivity studies revealed that particularly the combination of smaller N-R groups with Pt-B linkages of increased stability opens up opportunities for novel reactivity patterns of this class of compounds. Within the scope of these study, we inter alia succeeded in synthesizing the unusual bridged boryl species 1,4-trans-[{(Cy3P)2(Br)Pt(B{NH iBu}NH)}2C6H4] and a complex bearing both an acetylide ligand and an iminoboryl ligand, respectively.

Reaction of [(eta5-C5H4Li)(eta7-C7H6Li)Cr]tmeda with a variety of dialkyl(dichloro)silanes in aliphatic solvents afforded the corresponding [1]silatrochrocenophanes. Structural characterization by X-ray diffraction analysis of the [1]silatrochrocenophanes bearing Me2Si, (iPr)2Si, and silacyclobutane bridges revealed tilt angles alpha of 15.56(12) degrees , 15.8(1) degrees , and 16.33(17) degrees , respectively. Analogously, a [2]silatrochrocenophane (6) was prepared in excellent yield by reaction of [(eta5-C5H4Li)(eta7-C7H6Li)Cr]tmeda with 1,2-dichloro-1,1,2,2-tetramethyldisilane. This complex also was characterized structurally and exhibited a tilt angle alpha of 2.60(15) degrees. The [1]silatrochrocenophane bearing the Me2Si bridge underwent facile and regioselective carbon-silicon bond cleavage with [Pt(PEt3)4] to give a very high yield of an oxidative addition product. The ring-opening polymerization of these novel [1]silatrochrocenophanes afforded ring-opened chromium-based polymers.

Heterodinuclear bridged borylene complexes are synthesized via oxidative addition of the B-Br bond of bromoboryl complex precursors to an electron-rich palladium species. The synthetic protocol grants access to the first compound featuring the reactive bromoborylene ligand.

The first cationic metallaborylene complexes, [{(OC)5Mn}2(μ‐B)][BArf4] and [{(η5‐C5H4R)(OC)2Fe}2(μ‐B)][BArf4] (R=H, Me; see structure) were synthesized by halide abstraction from bridged haloborylene complexes and structurally characterized. The boron atom is located in the coordination sphere of two transition‐metal centers and is highly unsaturated.

Transition metal dihaloboryl complexes of the types [(η 5 -C 5 R 5 )Fe(CO) 2 BX 2 ] (R ) H, Me; X ) F, Cl, Br), [(η 5 -C 5 H 4 Me)Ru(CO) 2 BX 2 ] (X ) Cl), and [(OC) 5 MnBX 2 ] (X ) Cl, Br) were prepared via salt elimination reactions. Comparison of the CO stretching frequencies indicates a higher degree of Fe-B d π -p π back-bonding in the dibromoboryl complexes [(η 5 -C 5 R 5 )Fe(CO) 2 BBr 2 ] with respect to their -BCl 2 and -BF 2 analogues. This finding is constistent with the p π -p π back-bonding abilities of the halides (F > Cl > Br). Reactions of [(η 5 -C 5 Me 5 )Fe(CO) 2 BX 2 ] (X ) Cl, Br) with 4-methylpyridine were performed, leading to the formation of the corresponding Lewis-base adducts and, with base in excess, to the first metal-substituted boronium cation [(η 5 -C 5 Me 5 )Fe(CO) 2 BBr(NC 5 H 4 -4-Me) 2 ] + .

Transition metal complexes that feature the ferrocenyl(bromo)boryl ligand, -B(Fc)Br, were prepared utilizing salt-elimination and B-Br bond oxidative addition strategies. The stabilizing interaction that causes bending of the boron atom toward the ferrocenyl iron center in the FcBBr 2 precursor (1) weakens upon coordination of boron to the [(η 5 -C 5 R 5 )-(OC) 2 Fe] and trans-[(Cy 3 P) 2 PtBr] fragments. The efficient π-back-bonding capability of the latter is reflected in the absence of any Fe-B interaction in crystalline trans-[(Cy 3 P) 2 Pt-(Br){B(Fc)Br}] (7), the first platinum haloboryl complex featuring a non-heteroatom-stabilized boryl ligand to be fully characterized and structurally authenticated. In the half-sandwich complexes [(η 5 -C 5 R 5 )(OC) 2 Fe{B(Fc)Br}] (R ) H, 2; R ) Me, 3) different relative orientations of the [(η 5 -C 5 R 5 )(OC) 2 Fe] and -B(Fc)Br groups are accompanied by different degrees of bending within the boryl ligand. The sensitivity of this parameter to the electronic environment at boron offers an indirect qualitative estimation of the π-bonding component of the TM-B bond. † Dedicated to Prof. Dr. Johann Weis on the occasion of his 60th birthday.

ansa‐[2]Borabis(benzene)chromophane and ansa‐[2]boraferroarenophane were treated with alkynes in the presence of catalytic amounts of platinum or palladium/charcoal (see example) to afford the corresponding ansa‐bis(boryl)alkenes in excellent yields and without detectable side products. The use of Pt and Pd are the first examples of diboration reactions of alkynes to be conducted under heterogeneous conditions.