The complexes (C Me ) Th(EHTipp) , (E=P or As; Tipp=2,4,6-triisopropylphenyl), provide a ligand framework that results in facile access to rare Th-E multiple bonds. The reaction of (C Me ) Th(EHTipp) with KN(SiMe ) , proceeds cleanly to the desired bridging phosphinidiide or arsinidiide complex, [{(C Me ) Th(μ -ETipp)(μ -EHTipp)}K] under ambient conditions. In the absence of a chelating agent, the potassium cation of one monomeric unit interacts with the aryl ring of a second monomer to form a bridged dimer. In the presence of 2,2,2-cryptand, the terminal phosphinidene complex, [(C Me ) Th=PTipp(PHTipp)][K(2,2,2-cryptand)] is isolated. Using X-ray crystallographic analysis, we have determined these complexes display the shortest Th-P and Th-As bond lengths reported.
We report intramolecular proton transfer reactions to functionalize carbon monoxide and tert‐butyl nitrile from a bis(phosphido) thorium complex. The reaction of (C5Me5)2Th[PH(Mes)]2, Mes=2,4,6‐Me3C6H2, with 1 atm of CO yields (C5Me5)2Th(κ2‐(O,O)‐OCH2PMes‐C(O)PMes), in which one CO molecule is inserted into each thorium–phosphorus bond. Concomitant transfer of two protons, formerly coordinated to phosphorus, are now bound to one of the carbon atoms from one of the inserted CO molecules. DFT calculations were employed to determine the lowest energy pathway. With tert‐butyl nitrile, tBuCN, only one nitrile inserts into a thorium–phosphorus bond, but the proton is transferred to nitrogen with one phosphido remaining unperturbed affording (C5Me5)2Th[PH(Mes)][κ2‐(P,N)‐N(H)C(CMe3)P(Mes)]. Surprisingly, reaction of this compound with KN(SiMe3)2 removes the proton bound to nitrogen, not phosphorus.
A study of the comparative
reactivity of CO, CO2, tBuCN, and tBuNC with (C5Me5)2An[P(H)Mes]2 (An = Th, U) has been undertaken.
While CO2 and tBuNC form identical products
with both metals, namely (C5Me5)2An[κ2(O,O)-O2CPH(Mes)]2 and (C5Me5)2An[η2(tBuNCPMes](CNtBu), respectively, differing results are obtained with CO
and tBuCN. The reaction of tert-butylnitrile
with (C5Me5)2U[P(H)Mes]2 in a 2:1 ratio leads to double insertion into the U–P bonds
and elimination of H2PMes, forming the diketimido complex
(C5Me5)2U[κ2(N,N)-(NCtBu)2P(Mes)]. This is a case in which the analogous reaction with (C5Me5)2Th[P(H)Mes]2 affords
a different product, (C5Me5)2Th[PH(Mes)][κ2(P,N)-N(H)C(CMe3)P(Mes)]. The reaction of 1 atm of CO with (C5Me5)2U[P(H)Mes]2 results in double insertion with
proton migration from one phosphido ligand to one of the CO carbons
to form (C5Me5)2U[(κ2(O,O)-OCPMesC(O)(H)P(H)Mes].
This is in contrast to the previously published result of the reaction
between (C5Me5)2Th[P(H)Mes]2 and CO, in which the product is similar, but both protons from the
phosphido ligands migrate to one carbon atom, resulting in (C5Me5)2Th[κ2(O,O)-OC(H)2P(Mes)C(O)P(Mes)].
Density functional theory calculations demonstrate that the mechanisms
are quite similar and therefore a similar product is formed, except
uranium is less acidic, and the final C–H bond formation does
not occur.
A series of metallocene thorium complexes with mono- and bis(phosphido) ligands have been investigated with varying hues: (CMe)Th(Cl)[P(Mes)] (Mes = mesityl = 2,4,6-(CH)CH; dark red-purple), (CMe)Th[P(Mes)(CH)] (dark red-purple), (CMe)Th(CH)[P(Mes)] (dark red-purple), (CMe)Th(CH)[P(Mes)(SiMe)] (orange), (CMe)Th(Cl)[P(Mes)(SiMe)] (orange), (CMe)Th[P(Mes)(SiMe)] (orange), and (CMe)Th[PH(Mes)] (pale yellow). While all of these complexes bear a mesityl group on phosphorus, the electronic structure observed differs depending on the other substituent (mesityl, methyl, trimethylsilyl, or hydrogen). This sparked an investigation of the electronic structure of these complexes using P NMR and electronic absorption spectroscopy in concert with time-dependent density functional theory calculations.
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