A number of new arenetricarbonylchromium compounds have been synthesized in which the arene ring is substituted with a number of large groups such as t-butyl. Also prepared were the Ph3PCr(CO)2 and (PhO)3PCr(CO)2 analogues of these compounds and of more lightly substituted arenes, and a number of chelate compounds incorporating a short chain attached at C1 of the arene and bonded to chromium by phosphine, phosphite or phosphinite phosphorus atoms. The 13C n.m.r. spectra of these compounds have been recorded, and examined for evidence of stereo- specific influences of phosphorus on the chemical shifts of the arene ring carbons, but no such effects were found. 31P n.m.r. chemical shifts are also reported for these compounds.