Synthetic routes to dibenzylcalcium or para-substituted dibenzylcalcium complexes are described. Crystal structures of trans-(p-tBu-benzyl) 2 Ca‚(THF) 4 and cis-(benzyl) 2 Ca‚(THF) 4 show similar Ca-C and Ca-O bond distances. The observation of different geometries (cis/ trans) is explained by packing effects (DFT methods calculate less than 2 kcal/mol energy difference between cis-and trans-geometries). The strongly basic dibenzylcalcium complexes are useful precursors in calcium chemistry. Triphenylmethane was deprotonated, and the highly symmetric structure of [Ph 3 C -] 2 [Ca 2+ ‚(THF) 6 ] is discussed.

The formation of a stable triacylgermenolate 2 as a decisive intermediate was achieved by using three pathways. The first two methods involve the reaction of KO t Bu or alternatively potassium with tetraacylgermane 1 yielding 2 via one electron transfer. The mechanism involves the formation of radical anions (shown by EPR). This reaction is highly efficient and selective. The third method is a classical salt metathesis reaction toward 2 in nearly quantitative yield. The formation of 2 was confirmed by NMR spectroscopy, UV–vis measurements, and X-ray crystallography. Germenolate 2 serves as a starting point for a wide variety of organo-germanium compounds. We demonstrate the potential of this intermediate by introducing new types of Ge-based photoinitiators 4b – 4f . The UV–vis absorption spectra of 4b – 4f show considerably increased band intensities due to the presence of eight or more chromophores. Moreover, compounds 4d – 4f show absorption tailing up to 525 nm. The performance of these photoinitiators is demonstrated by spectroscopy (time-resolved EPR, laser flash photolysis (LFP), photobleaching (UV–vis)) and photopolymerization experiments (photo-DSC measurements).

The possibility to utilize electromagnetic irradiation above 400 nm for the initiation of polymerization reactions provides several advantages such as a lower energy demand and higher curing depths in pigmented reactive systems. Recent developments of PIs based on phosphorus and group 14 elements as well as other selected concepts for Type I visible light initiators are outlined and discussed within this review.

Acylgermanes are known as highly efficient photoinitiators. In this contribution, we present the synthesis of new diacylgermanes 4a-e via a multiple silyl abstraction methodology. The method outperforms the state-of-the-art approach...

Dedicated to Professor Frank Uhlig on the occasion of his 60 th birthdayIsolable stannenolates LKSn[(CO)R] 3 (R = 2,4,6-trimethylphenyl (1 a, b), L = DME for (1 a) or 18-crown-6 for (1 b)), a new building block for the synthesis of effective Sn-based photoinitiators, were synthesized. The formation of these derivatives was confirmed by NMR spectroscopy, UV/Vis spectroscopy as well as X-ray crystallographic analysis. Compound 1 a is employed as a synthon in main group chemistry through reactions with two different types of electrophiles (acid chlorides and alkyl halides). All investigated electrophiles react via the salt metathesis reaction and gave rise to novel acylstannanes in good to excellent yields. The applicability as visible light photoinitiators is demonstrated by photobleaching (UV/Vis absorption spectroscopic studies) as well as through application in photo-DSC studies.