Systematic Investigation of the Molecular and Electronic Structure of Thorium and Uranium Phosphorus and Arsenic Complexes

In continuing to examine the interaction of actinide-ligand bonds with soft donor ligands, a comparative investigation phosphorus and arsenic was conducted. A reaction (C5Me5)2AnMe2, An = Th, U, 2 equiv H2AsMes, Mes 2,4,6-Me3C6H2, forms primary bis(arsenido) complexes, (C5Me5)2An[As(H)Mes]2. Both exhibit thermal instability at room temperature, leading elimination H2, formation diarsenido species, (C5Me5)2An(η2-As2Mes2). The analogous diphosphido (C5Me5)2An(η2-P2Mes2), could not be synthesized via same route, even upon heating bis(phosphido) species 100 °C in toluene. However, they were accessible dimesityldiphosphane, MesP(H)P(H)Mes, (C5Me5)2AnMe2 70 When is reacted 1 bridging μ2-arsinidiide complexes [(C5Me5)2An]2(μ2-AsMes)2 are formed. Upon (C5Me5)2UMe2 H2PMes, phosphinidiide [(C5Me5)2U(μ2-PMes)]2 isolated. thorium leads phosphido C–H bond activation methyl on mesityl group, forming {(C5Me5)2Th[P(H)(2,4-Me2C6H2-6-CH2)]}2. reactivity [(C5Me5)2An(μ2-EMes)]2 investigated OPPh3 an effort produce terminal phosphinidene or arsinidene complexes. For E As, U(III) cation–anion pair [(C5Me5)2U(η2-As2Mes2)][(C5Me5)2U(OPPh3)2] [(C5Me5)2Th(μ2-AsMes)]2 does result but, instead, eliminates PPh3 yield arsinidiide/oxo complex, [(C5Me5)2Th]2(μ2-AsMes)(μ2-O). Finally, combination yields phosphinidene, (C5Me5)2U(═PMes)(OPPh3), featuring short U–P distance 2.502(2) Å. Electrochemical measurements uranium pnictinidiide demonstrate only 0.04 V difference as slightly better donor. Magnetic show more excited-state mixing therefore higher magnetic moments arsenic-containing compounds but no deviation from uncoupled U(IV) behavior. quantum theory atoms molecules analysis shows highly polarized actinide-pnictogen similar bonding characteristics, supporting electrochemical between actinide-phosphorus actinide-arsenic bonds.