Hayes, Paul

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    Alkylamido lutetium complexes as prospective lutetium imido precursors: synthesis, characterization and ligand design
    (Royal Society of Chemistry, 2025) Knott, Jackson P.; Hsiang, Shou-Jen; Hayes, Paul G.
    Mixed alkylamido lutetium complexes, LiPrLu(CH2SiMe3)(NHCPh3) (7CPh3) and LiPrLu(CH2SiMe3)(NHDipp) (7Dipp) (LiPr = 2,5-[iPr2P = N(4-iPrC6H4)]2C4H2N−), were synthesized by addition of a bulky primary amine, NH2R (R = CPh3, Dipp) (Dipp = 2,6-iPr2C6H3) to the dialkyl complex LiPrLu(CH2SiMe3)2 (6). Unlike complexes supported by the related pincer ligand LPh (LPh = 2,5-[Ph2P = N(4-iPrC6H4)]2C4H2N−) these species proved resistant to C–H cyclometalative processes. Attempts to access lutetium imdes via addition of 4-dimethylaminopyridine (DMAP) to 7CPh3 and 7Dipp promoted disproportionation, affording 0.5 equivalents of the corresponding bisamide complexes LiPrLu(NHCPh3)2 (8CPh3) and LiPrLu(NHDipp)2 (8Dipp), respectively, as well as 0.5 equivalents of LiPrLu(CH2SiMe3)2, which decomposed in the presence of DMAP. Incorporation of internal Lewis bases was accomplished by replacing the N-aryl substituents in LiPr with 4,6-dimethylpyrimidine groups (LPm, 11). The correspondng dialkyl lutetium complex LPmLu(CH2SiMe3)2 (12) was prepared, from which loss of SiMe4 occured over a period of hours in benzene-d6 solution.
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    Rhodium-mediated assembly of new heterocycles: from borylenes to oxaboroles
    (Wiley, 2025) Hsiang, Shou-Jen; Hayes, Paul G.
    Base-stabilized rhodium borylene complex κ2-L(CO)Rh(BMes), 2; κ2-L=κ2-NN’-Rh,κ1-N−B-(2,5-[iPr2P=N(4-iPrC6H4)]2-N’(C4H2)−); Mes=mesityl, reacts with a series of alkynes (PhC≡C—R; R=Ph, Me, CO2Et, H) to yield unique structures whereby the alkyne has regioselectively added across boron and the carbon atom of a CO ligand. The resulting complexes, LRh[C(O)C(Ph)C(R)B(Mes)], 3R, react with additional CO to afford cycle-containing products, L(CO)Rhmathematical equation ), 5R, that ultimately release highly functionalized organic heterocycles of the form mathematical equation =NPipp (Pipp=4-iPrC6H4), 6. These oxaboroles, which were assembled from a primary hydroborane, CO, an alkyne, and an azide-generated NPipp, are structurally analogous to two of the five boron-containing therapeutics approved by the FDA.
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    Rhodium-mediated dehydrogenation of hydroboranes and group 14 compounds: base-stabilized silylene and germylene complexes vs. transmetalation
    (Wiley, 2024) Hayes, Paul G.; Hsiang, Shou-Jen
    Monocarbonyl rhodium complex LRh(CO), 1, which is stabilized by a pyrrole-based bis(phosphinimine) pincer ligand (L=k3- NNN’=2,5-[iPr2P=N(4-iPrC6H4)]2-N’(C4H2)􀀀 ), serves as a versatile platform for the dehydrogenation of group 14 substrates. Reaction with primary and secondary silanes and germanes (MesSiH3, Et2SiH2, Ph2GeH2, tBuGeH3; Mes=mesityl) liberates H2 and yields base-stabilized tetrylene compounds of the form k2- L(CO)Rh(ER2) (E=Si: R=Mes, H, 2; R=Et, 5; E=Ge: R=Ph, 6; R= tBu, H, 8). The “:ER2” fragment in these species bridges between the rhodium center and a phosphinimine donor. Preliminary reactions between pinacol (Pin) and k2-L(CO)Rh(ER2), E=Si, Ge, indicate that such complexes can serve as silylene and germylene synthons, releasing :ER2 and catalytically generating PinER2. In contrast, combination of complex 1 and MesGeH3 does not yield the anticipated dehydrogenation product, but rather, transmetalation similar to that observed upon reaction between 1 and 3,5-dimethylphenylborane prevails.
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    X-ray crystal structure of [L2Ag3]+[OTf]−·5C6D6: a monoanionic bis­­phosphinimine ligand supported tris­­ilver complex
    (2021) Drescher, Sam L.; Forfar, Christopher P.; Boeré, René T.; Hayes, Paul G.
    The compound bis­{μ3-2,5-bis­[N-(4-iso­propyl­phen­yl)-P,P-di­phenyl­phospho­r­im­i­do­yl]pyrrol-1-ido-κ3N:N′:N′′}tris­ilver(I) tri­fluoro­methane­sulfonate deuterated benzene penta­solvate, [Ag3(C46H44N3P2)2](CF3O3S)·5C6D6, (I), was synthesized from two equivalents of NaL [L = 2,5-(4-iPrC6H4N=PPh2)C4H2N] and three equivalents of AgOTf (OTf = OSO2CF3). High-quality crystals of (I) formed with five deuterated benzene solvent mol­ecules in the asymmetric unit. Notably, the bond lengths and angles between the three silver atoms are markedly different, unlike in most other reported tris­ilver complexes that tend to form three equivalent metal centers. Additionally, to the best of our knowledge, this is the first report of a tris­ilver complex with six nitro­gen donors from two bis­phosphinimine ligands.
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    Triamidoamine-supported zirconium: hydrogen activation, Lewis acidity, and rac-lactide polymerization
    (Royal Society of Chemistry, 2016) Leshinski, Sarah E.; Wheaton, Craig A.; Sun, Hongsui; Roering, Andrew J.; Tanski, Joseph M.; Fox, Daniel J.; Hayes, Paul G.; Waterman, Rory
    Investigation of a triamidoamine-supported zirconium hydride intermediate, important to a range of catalytic reactions, revealed the potential Lewis acidity of [k5-N,N,N,N,C-(Me3SiNCH2CH2)2NCH2CH2NSiMe2CH2]Zr (1). A preliminary study of 1 as a precursor for the polymerization of rac-lactide showed modest activity but indicated that five-coordinate zirconium complexes with tetra-N donor ligands may be an avenue for further development in group 4 metal lactide polymerization catalysis.