The Chemistry of Acylgermanes: Triacylgermenolates Represent Valuable Building Blocks for the Synthesis of a Variety of Germanium-Based Photoinitiators.

The formation of a stable triacylgermenolate as a decisive intermediate was achieved by using three pathways. The first two methods involve the reaction of KOBu or alternatively potassium with tetraacylgermane yielding 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 in nearly quantitative yield. The formation of was confirmed by NMR spectroscopy, UV-vis measurements, and X-ray crystallography. Germenolate 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 -. The UV-vis absorption spectra of - show considerably increased band intensities due to the presence of eight or more chromophores. Moreover, compounds - 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).