Boranyl-Functionalized [Ge9 ] Clusters: Providing the Idea of Intramolecular Ge/B Frustrated Lewis Pairs

The unique three-dimensional structure of spherical, homoatomic nine-atom germanium clusters opens various possibilities for the spatial arrangement of functional groups. Ligands comprising lone pairs have recently been introduced in the cluster sphere, and we now report the addition of a boranyl group to the cluster featuring a Ge-B exo-cluster bond. The reaction of the twofold-silylated cluster [Ge9 {Si(TMS)3 }2 ]2- (TMS=trimethylsilyl) with 2-chloro-1,3,2-diazaborolidines DABR -Cl leads to the first boranyl-functionalized [Ge9 ] clusters [Ge9 {Si(TMS)3 }2 DABR ]- (R=methyl (1 a), iso-propyl (2 a), ortho-tolyl (3 a)). The anions 2 a and 3 a were structurally characterized as [NHCDipp Cu]+ complexes (NHCDipp =1,3-di(2,6-diisopropylphenyl)imidazolylidine) through single crystal X-ray structure determination. Quantum-chemical calculations manifest the frustrated Lewis pair (FLP) character of the boranyl-functionalized cluster [Ge9 {Si(TMS)3 }2 BCy2 ]- (4 a).

Synthesis, Structure, Solid-State NMR Spectroscopy, and Electronic Structures of the Phosphidotrielates Li3 AlP2 and Li3 GaP2

The lithium phosphidoaluminate Li9 AlP4 represents a promising new compound with a high lithium ion mobility. This triggered the search for new members in the family of lithium phosphidotrielates, and the novel compounds Li3 AlP2 and Li3 GaP2 , obtained directly from the elements via ball milling and subsequent annealing, are reported here. It was unexpectedly found through band structure calculations that Li3 AlP2 and Li3 GaP2 are direct band gap semiconductors with band gaps of 3.1 and 2.8 eV, respectively. Rietveld analyses reveal that both compounds crystallize isotypically in the orthorhombic space group Cmce (no. 64) with lattice parameters of a=11.5138(2), b=11.7634(2) and c=5.8202(1) Å for Li3 AlP2 , and a=11.5839(2), b=11.7809(2) and c=5.8129(2) Å for Li3 GaP2 . The crystal structures feature TrP4 (Tr=Al, Ga) corner- and edge-sharing tetrahedra, forming two-dimensional∞ 2 T r P 2 3 - layers. The lithium atoms are located between and inside these layers. The crystal structures were confirmed by MAS-NMR spectroscopy.

Fast Lithium Ion Conduction in Lithium Phosphidoaluminates

Solid electrolyte materials are crucial for the development of high-energy-density all-solid-state batteries (ASSB) using a nonflammable electrolyte. In order to retain a low lithium-ion transfer resistance, fast lithium ion conducting solid electrolytes are required. We report on the novel superionic conductor Li9 AlP4 which is easily synthesised from the elements via ball-milling and subsequent annealing at moderate temperatures and which is characterized by single-crystal and powder X-ray diffraction. This representative of the novel compound class of lithium phosphidoaluminates has, as an undoped material, a remarkable fast ionic conductivity of 3 mS cm-1 and a low activation energy of 29 kJ mol-1 as determined by impedance spectroscopy. Temperature-dependent 7 Li NMR spectroscopy supports the fast lithium motion. In addition, Li9 AlP4 combines a very high lithium content with a very low theoretical density of 1.703 g cm-3 . The distribution of the Li atoms over the diverse crystallographic positions between the [AlP4 ]9- tetrahedra is analyzed by means of DFT calculations.

N-Hydroxysuccinimide-Modified Ethynylphosphonamidates Enable the Synthesis of Configurationally Defined Protein Conjugates

Herein, the application of N-hydroxysuccinimide-modified phosphonamidate building blocks for the incorporation of cysteine-selective ethynylphosphonamidates into lysine residues of proteins, followed by thiol addition with small molecules and proteins, is reported. It is demonstrated that the building blocks significantly lower undesired homo-crosslinking side products that can occur with commonly applied succinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxylate (SMCC) under physiological pH. The previously demonstrated stability of the phosphonamidate moiety additionally solves the problem of premature maleimide hydrolysis, which can hamper the efficiency of subsequent thiol addition. Furthermore, a method to separate the phosphonamidate enantiomers to be able to synthesize protein conjugates in a defined configuration has been developed. Finally, the building blocks are applied to the construction of functional antibody-drug conjugates, analogously to FDA-approved, SMCC-linked Kadcyla, and to the synthesis of a functional antibody-protein conjugate.