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 Å, 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.