Organocatalyzed Phospha-Michael Addition: A Highly Efficient Synthesis of Customized Bis(acyl)phosphane Oxide Photoinitiators.

Addition of the P-H bond in bis(mesitoyl)phosphine, HP(COMes)2 (BAPH), to a wide variety of activated carbon-carbon double bonds as acceptors was investigated. While this phospha-Michael addition does not proceed in the absence of an additive or catalyst, excellent results were obtained with stoichiometric basic potassium or caesium salts. Simple amine bases can be employed in catalytic amounts, and tetramethylguanidine (TMG) in particular is an outstanding catalyst that allows the preparation of bis(acyl)phosphines, R-P(COMes)2 , under very mild conditions in excellent yields after only a short time. All phosphines RP(COMes)2 can subsequently be oxidized to the corresponding bis(acyl)phosphane oxides, RPO(COMes)2 , a substance class belonging to the most potent photoinitiators for radical polymerizations known to date. Thus, a simple and highly atom economic method has been found that allows the preparation of a broad range of photoinitiators adapted to their specific field of application even on a large scale.

Dibismuthates as Linking Units for Bis-Zwitterions and Coordination Polymers.

Adducts of bismuth trihalides BiX3 (X = Cl, Br, I) and the PS3 ligand (PS3 = P(C6H4-o-CH2SCH3)3) react with HCl to form inorganic/organic hybrids with the general formula [HPS3BiX4]2. On the basis of their solid-state structures determined by single-crystal X-ray diffraction, these compounds exhibit discrete bis-zwitterionic assemblies consisting of two phosphonium units [HPS3]+ linked to a central dibismuthate core [Bi2X8]2- via S→Bi dative interactions. Remarkably, the phosphorus center of the PS3 ligand undergoes protonation with hydrochloric acid. This is in stark contrast to the protonation of phosphines commonly observed with hydrogen halides resulting in equilibrium. To understand the important factors in this protonation reaction, 31P NMR experiments and DFT computations have been performed. Furthermore, the dibismuthate linker was utilized to obtain the coordination polymer {[AgPS3BiCl3(OTf)]2(CH3CN)2}∞, in which dicationic [Ag(PS3)]22+ macrocycles containing five-coordinate silver centers connect the dianionic [Bi2Cl6(OTf)2]2- dibismuthate fragments. The bonding situation in these dibismuthates has been investigated by single-crystal X-ray diffraction and DFT calculations (NBO analysis, AIM analysis, charge distribution).