2,2'-Biphosphinines and 1,4-Diphosphadienes as 8-Electron Donors towardManganese Carbonyl

Article abstract of DOI:10.1021/ic00124a024

The reaction of 3,3',4,4'-tetramethyl-2,2'-biphosphinine (tmbp) with Mn2(CO)10 at 140°C affords [Mn2(tmbp)(CO)6], a complex where tmbp acts as a 8-electron donor through its central P=C-C=P 1,4-diphosphadieneunit. An X-ray crystal structure analysis of this complex shows a delocalized 5-membered C2MnP2 ring π-complexed to a second Mn(CO)3 unit, which results in a disruption of the aromaticity of the two phosphinine rings. Similar behavior is observed upon reaction of 1,2-dihydro-1,2-diphosphetes with Mn2(CO)10. The initial product involves the incorporation of Mn(CO)4 and Mn(CO)3 units into the P-P bond of the ring and coordination of the C=C double bond of the diphosphete to the Mn(CO)3 unit. Loss of CO occurs upon heating, to yield a 1,4-diphosphadiene-Mn2(CO)6 complex whose structure is strictly analogous to the central unit of [Mn2(tmbp)(CO)6].