Synthesis and electrochemistry of (CO)2(PMe3)Fe(.mu.2-tert-Bu2P)(.mu.2-CO)Rh(PMe3)L(Fe-Rh) (L = CO, PMe3). Digital simulation of modified ECE mechanism. X-ray crystal structures of (CO)2(PMe3)Fe(.mu.2-tert-Bu2P)(.mu.2-CO)Rh(PMe3)2 and [Me3PO.cntdot.Na(15-crown-5)]+[(CO)3Fe(.mu.2-tert-Bu2P)Rh(PMe3)(CO)]-