Recent Progress in Oxo‐ and Fluorometalate Chemistry

About a quarter of a century ago a review article having almost the same title appeared in this journal [1] . Since then many hundreds of new fluorides and oxides of metals have been synthesized, and repeatedly subjected to detailed investigation. Why, and to what end are such compounds still studied [2] ? Has our knowledge been not only widened but also deepened? What advances have been made in synthetic chemistry in this sector? Have new ideas led to unforeseen results and have unexpected findings forced the revision of tested concepts? This area of research belongs to solid state chemistry, and in the meantime has become almost unsurveyable even for a committed researcher. In this paper, therefore, an attempt is made to outline any relevant advances that have been made and to present open questions and new aspects using selected examples, mainly from the chemistry of the first row of the transition metal series. Those not directly involved in this area may be surprised to find that even substances with a simple composition are also cited. They might ask whether such compounds mentioned in text books are not already understood. Although it is a widely‐held view that such compounds are well known, this is incorrect: Probably no‐one has ever prepared a sample of CrF 2 or Na 2 O whose composition “adequately” exactly corresponded to the quoted formula [3] . Typical examples which demonstrate the considerable effort necessary for finally proving what others long ago already assumed to know, can be taken from the area of inorganic chemistry (e.g. : As 2 O   5 [4] ) as well as from organic chemistry (e.g. C 4 [C(CH 3 ) 3 ]   4 [5] ).