Negative ion chemical ionization mass spectra of (η 6 ‐arene)Cr(CO) 3

The negative ion chemical ionization mass spectra, with ammonia and methane as reagent gases, of the (η 6 ‐arene)Cr(CO) 3 complexes, where the arene is C 6 H 5 COCH 3 , C 6 H 5 COC 2 H 5 , C 6 H 5 COC 3 H 7 , C 6 H 5 COC(CH 3 ) 3 , 2‐CH 3 C 6 H 4 COC 3 H 7 , C 6 H 5 COOCH 3 , C 6 H 5 CH 3 , 1,3,5‐(CH 3 ) 3 C 6 H 3 and C 6 H 5 CH 2 COC 2 H 5 , are reported. Similar behaviour is observed with the two reagent gases, but ammonia shows a much higher abundance for the ions produced by reactions of [NH 2 ] − with sample molecules. The compounds containing the C 6 H 5 CO group display an abundant [M] − ˙ , whereas the other compounds exhibit [MH] − as base peak, produced by ion/molecule reactions. A comparison of the negative ion chemical ionization mass spectra of the (η 6 ‐arene)Cr(CO) 3 complexes with those of the corresponding ligands shows the strong electron withdrawing power of the Cr(CO) 3 group in the gas phase.