Carbon compounds of the transition metals. Part XIV. The crystal structure of tricarbonyl-exo-7-phenylcyclohepta-1,3,5-trienechromium

Abstract

Tricarbonyl-exo-7-phenylcyclohepta-1,3,5-trienechromium crystallises in the spacegroup P21/n with four molecules in a unit cell of dimensions a= 10·21 ± 0·02, b= 14·01 ± 0·03, c= 9·96 ± 0·02 A, and β= 105° 20′± 10′. The structure has been determined from 993 visually estimated intensities and refined by least-squares methods to final R values of 7·5 and 9·9%(non-zero and all data respectively). The structure consists of discrete molecules of formula C16H12CrO3. The C–C distances in the ring, except for those to the methylene carbon, show an alternation in distance typical of a system of conjugated single and double bonds. The conjugated portion is almost planar and the chromium atom is trans to the methylene carbon.