Only a very few complexes of the type H2Fe(CO)2(PR3)2 have been reported
previously [27] and the only one structurally-characterized is H2Fe(CO)2[dppe]
(dppe=1,2-bis (diphenylphosphino)ethane), which obviously exhibits a cis geometry
of the phosphorus atoms [28]. The now easy access to these complexes according
to Eq. (4) has been confirmed recently [29].
The dihydrides H2Fe(CO)2(PR3)2 react with added phosphine to afford quantitatively
the trisubstituted complexes Fe(CO)2(PR3)3 (Eq. (5)).