Introducing new phosphorus substituents in terminal phosphinidene complexes. An illustration with [(ethoxycarbonyl)phosphinidene]-, (tert-butoxyphosphinidene)-, and (fluorenylphosphinidene)pentacarbonyltungsten complexes

Article abstract of DOI:10.1021/om00098a017

The reaction of ethyl chloroformate with the [(3,4-dimethylphospholyl)lithium(P-W)]pentacarbonyltungsten complex yields the corresponding 1-(ethoxycarbonyl)phosphole complex. Upon reaction with dimethyl acetylenedicarboxylate, this phosphole derivative gives the corresponding 7-phosphanorbornadiene complex which in turn appears to be a good precursor for the transient (ethoxycarbonyl)phosphimdene complex [EtO-C(O)-P=W(CO)₅]. This transient species cleanly reacts with methanol, diethylamme, and tolan to give the expected phosphinite and phosphirene complexes. However, it appears impossible to perform the P-CO₂Et → P-H conversion via the attack of OH^- at the carbonyl group without destroying the phosphinite and phosphirene structures. Thus [EtO-C(O)-P=W(CO)₅] cannot be used as a masked [HP=W(CO)₅]. In order to vary the substituent at phosphorus in the transient phosphimdene complexes, it is possible to start with 1-cyano-3,4-dimethylphosphole which is easily obtained from BrCN and the appropriate phospholyl anion. This 1-cyanophosphole provides for the first time an easy access to 1-alkoxy-, 1-amino- 1-aryl-, and 1-alkynyl-3,4-dimethylphospholes. Using the same basic scheme as with the ethoxycarbonyl substituent, it is possible to prepare from these new phospholes the corresponding 7-phoephanorbornadiene complexes. The precursors of [t-BuO-P=W(CO)₅] and [9-fluorenyl-P=W(CO)₅] are thus prepared and tested as an example.