Abstract The reaction between rac-(benzocyclobutenone) tricarbonylchromium (rac-1) and lithium diisopropylphosphide (LDP) or lithium di-tert-butylphosphide, unlike its reaction with lithium diisopropylamide (LDA), results in a distal ring-opening, with formation of acylphosphane derivatives. The tricarbonylchromium complex rac-6 of 2- methylbenzoyldiisopropylphosphane has been structurally characterized. The reaction ...