Diphosgene is far from a safe compound. It is a very noxious heavy liquid (density = 1.65 g / cm3), with a vapour pressure of 10 mm Hg at 20 °C.
It is produced by the photochlorination of
ClCOOCH3 or HCOOCH3
Furthermore, it isn't a stable molecule: it tends to decompose into phosgene ... (Fe2O3 cathalyses the decomposition and I think also pyridine - if my memory serves me right).
Triphosgene is the safe alternative, since it is a crystalline compound (easy to work with) and the most important: it is stable. One molecule of triphosgene is equivalent to three molecules of phosgene. I used it once to make some isocyanate.
Why don't you use one of those fine coupling reagentia they use in peptide chemistry (TBTU, DCC, BOP, pyBOP, water soluble carbodiimide to name a few). These reagents are far more convenient than those nasty phosgene compounds.
Veerle //