Versatile Supramolecular Coordination Behaviour of a Bis(bidentate) Tetraphosphane

New Rigid Polycyclic Bis(phosphane) for Asymmetric Catalysis

A simple, highly efficient synthesis of a series of novel chiral non-racemic rigid tetracyclic phosphorus ligands, applicable in important chemical asymmetric transformations, was performed. In a tandem cross-coupling/C-H bond activation reaction, a well-recognised and readily available ligand (R,R)-NORPHOS was used as the starting material. The palladium complexes of new ligands were obtained and characterised on the example of a crystalline dichloropalladium complex of [(1R,2R,9S,10S,11R,12R)-4-phenyltetracyclo[8.2.1.0^2,9.0^3,8]trideca-3,5,7-triene-11,12-diyl]bis(diphenylphosphane). A notably high activity and stereoselectivity of the palladium catalysts based on the new ligands were confirmed in a model asymmetric allylic substitution reaction. Herein, we discuss the geometry of the palladium complexes formed and its impact on the efficiency of the catalysts. A comparison of their geometric features with other bis(phosphane) ligand complexes found in the Cambridge Structural Database and built density functional theory (DFT) commutated models is also presented and rationalised.

Photochemical Synthesis of cis,trans,cis-1,2,3,4-Tetrakis(diphenylphosphanyl)buta-1,3-diene and Its Metal Coordination

The new bis(bidentate) tetraphosphane cis,trans,cis‐1,2,3,4‐tetrakis(diphenylphosphanyl)buta‐1,3‐diene (dppbd) (7) was obtained by applying a photochemical synthetic protocol. The key step of the photochemical reaction consisted of an intramolecular [2+2] cycloaddition involving a C–C double and triple bond of the Pt‐dimer species of the formula [Pt₂Cl₄(dppa)(trans‐dppen)] (2) {dppa = 1,2‐bis(diphenylphosphanyl)acetylene and dppen = 1,2‐bis(diphenylphosphanyl)ethene} leading to [Pt₂Cl₄(dppbd)] (5). The asymmetrically bridged precursor complex 2 was obtained by combinatorial chemistry. Single crystal X‐ray structure analyses of 2 and 5 proved that the intramolecular photochemical reaction occurred. Cyanolysis of 5 gave 7, which was oxidized to dppbdO4 (8). Compounds 7, 8, and the Pd^II dimer complex [Pd₂Cl₄(dppbd)] (9) were characterized in the solid state by a single‐crystal X‐ray structure analysis. Interesting photophysial properties emerged from the UV/Vis spectra acquired for 7 and the dimer Os complexes meso‐Δ,Λ/Λ,Δ‐[Os₂(bpy)₄(dppbd)](PF₆)₄ (10) and rac‐Δ,Δ/Λ,Λ‐[Os₂(bpy)₄(dppbd)](PF₆)₄ (11).

Crystal structure of r-1,c-2-dibenzoyl-t-3,t-4-bis-(2-nitro-phen-yl)cyclo-butane

The condensation reaction of aceto-phenone (1-phenyl-ethan-1-one) with 2-nitro-benzaldehyde in the molten state yielded the expected chalcone, (E)-3-(2-nitro-phen-yl)-1-phenyl-prop-2-en-1-one, and, unexpectedly, the title compound, C30H22N2O6, which results from the syn head-to-head [2 + 2] cyclo-addition of the chalcone. The mol-ecular structure of the dimer shows that the four benzene rings of the substituents are oriented in such a way that potential steric hindrance is minimized, whilst allowing some degree of inter-molecular π-π inter-actions for crystal stabilization. In the mol-ecule, one nitro group is disordered over two positions, with occupancies for each part of 0.876 (7) and 0.127 (7).

Unusual stability of dyads during photochemical hydrogen production

Heterodimetallic dyads containing Os and Pd are connected by a bis(bidentate) phosphine and show an excellent stability for the water splitting application.