The present volume describes acyclic Sulfur-nitrogen compounds with sulfur of the oxida- tion number II. The first chapter deals with sulfur imide (S=NH), N-organyl-sulfur imides (S=NR, R = or- ganyl), and metal complexes of sulfur imides. N-Organyl-sulfur imides have not been isolated, but they can be trapped, for example, by cycloaddition and stabilized by coordination to transi- tion metals. 11 The following chapter present a detailed survey of other 8 -N compounds with one- coordinate sulfur, e.g., dithionitrous acid (S=N-SH) and derivatives, the salts of the dithionitryl ion (1 +) ([S=N=S]+), and N-thionitroso-diorganyl-amines (S=NNR , R = organyl). Only the reac- 2 tions of [S=N=S]+ AsF5, among the known [S=N=S]+ salts, have been extensively studied. Cycloadditions with alkenes and triple bonded compounds produce 1 ,3,2-dithiazolium salts and their derivatives. S=NN(CH )z and S=NN(C H )z form transition metal complexes. The 3 6 5 Iigand is coordinated via the S atom in a monodentate manner.

PF3, (CH3)3SiCl -> (CH3)3SiF, and RC(O)Cl -> RC(O)F. Others include the conversion of (C6H5)3P into (C6H5)3PF2 and of (R3NC(S)S)2 into R2NCF3, R=alkyl. In organic chemistry, fluorides are easily accessible from alcohols, geminal fluorides RR'CF2 from the respective aldehydes or ketones, and acyl fluorides RC(O)F from carboxylic acides by using DAST. Because DAST is easy to handle and gives clean reactions in syntheses, this Gmelin volume devotes much space to the description of the chemical and physical properties od DAST.

The present volume describes organoberyllium compounds containing at least one berylli um-carbon bond, except the beryllium carbides and cyanides. It covers the literature com pletely to the end of 1986 and includes most of the references up to mid-1987. This Gmelin volume is different from all other volumes of the series on organometallic compounds in that it is dedicated to an area of research which has virtually come to a complete standstill. Organoberyllium chemistry has never been a very popular field, and only few workers have contributed to its slow growth, as is seen by the relatively small number of publications in the field. This very modest development became stagnant in the early 1970's and was followed by a rapid decline. This exceptional fate of a branch of organometallic chemistry is only partly due to the very limited number of potential application~ of beryllium and its compounds. The compounds of this element are, in principle, at least as interesting and intriguing to scientists as those of other metals in the Periodic Table. No doubt the main reason for the apparent ban of all experimental organoberyllium chemistry is to be found in the established, and alleged, hazardous properties of beryllium compounds. Although similar hazards have been established for other organometallics where active research is still in process, e. g. , mercury and lead, these observations were absolutely lethaI for organoberyllium research.