Electronic and Steric Influences of Pendant Amine Groups on the Protonation of Molybdenum Bis(dinitrogen) Complexes
Labios, LA; Heiden, ZM; Mock, MT
| HERO ID | 4834934 |
|---|---|
| In Press | No |
| Year | 2015 |
| Title | Electronic and Steric Influences of Pendant Amine Groups on the Protonation of Molybdenum Bis(dinitrogen) Complexes |
| Authors | Labios, LA; Heiden, ZM; Mock, MT |
| Journal | Inorganic Chemistry |
| Volume | 54 |
| Issue | 9 |
| Page Numbers | 4409-4422 |
| Abstract | The synthesis of a series of P(Et)P(NRR(')) (P(Et)P(NRR(')) = Et2PCH2CH2P(CH2NRR')2, R = H, R' = Ph or 2,4-difluorophenyl; R = R' = Ph or (i)Pr) diphosphine ligands containing mono- and disubstituted pendant amine groups and the preparation of their corresponding molybdenum bis(dinitrogen) complexes trans-Mo(N2)2(PMePh2)2(P(Et)P(NRR('))) is described. In situ IR and multinuclear NMR spectroscopic studies monitoring the stepwise addition of triflic acid (HOTf) to trans-Mo(N2)2(PMePh2)2(P(Et)P(NRR('))) complexes in tetrahydrofuran at -40 °C show that the electronic and steric properties of the R and R' groups of the pendant amines influence whether the complexes are protonated at Mo, a pendant amine, a coordinated N2 ligand, or a combination of these sites. For example, complexes containing monoaryl-substituted pendant amines are protonated at Mo and the pendant amine site to generate mono- and dicationic Mo-H species. Protonation of the complex containing less basic diphenyl-substituted pendant amines exclusively generates a monocationic hydrazido (Mo(NNH2)) product, indicating preferential protonation of an N2 ligand. Addition of HOTf to the complex featuring more basic diisopropyl amines primarily produces a monocationic product protonated at a pendant amine site, as well as a trace amount of dicationic Mo(NNH2) product that is additionally protonated at a pendant amine site. In addition, trans-Mo(N2)2(PMePh2)2(depe) (depe = Et2PCH2CH2PEt2) was synthesized to serve as a counterpart lacking pendant amines. Treatment of this complex with HOTf generated a monocationic Mo(NNH2) product. Protonolysis experiments conducted on several complexes in this study afforded trace amounts of NH4(+). Computational analysis of trans-Mo(N2)2(PMePh2)2(P(Et)P(NRR('))) complexes provides further insight into the proton affinity values of the metal center, N2 ligand, and pendant amine sites to rationalize differences in their reactivity profiles. |
| Doi | 10.1021/acs.inorgchem.5b00209 |
| Pmid | 25871448 |
| Wosid | WOS:000354075600031 |
| Is Certified Translation | No |
| Dupe Override | No |
| Is Public | Yes |
| Language Text | English |