Reaction of (h5-C5Me5)Fe(CO)2P:PR [[Fe]P:PR R = C6H2(CMe3)3-2,4,6] with a 5-fold excess of N-methylmaleimide leads to cleavage of the P:P bond. Phosphidoiron complex I (same R) is formed, which features a P atom with a succinimidyl and a bicyclo[3.1.0]-1-aza-4-phosphahexane-2,6-dion-3-yl substituent. Two diastereoisomers of I were distinguished by NMR spectroscopy. The crystal and mol. structure of I were detd. by x-ray anal.