Phosphine–imine and –enamido ligands for acceptorless dehydrogenation catalysis

Abstract

A highly tunable phosphine-imine ligand family is introduced. Following metallation with ruthenium, deprotonation of the ligand affords a phosphine-enamido species. Complexes with the ligand in both the imine and enamido forms are active toward acceptorless dehydrogenation reactions.

C(sp3)–C(sp3) Coupling with a Pd(II) Complex Bearing a Structurally Responsive Ligand

“…We hypothesized that a structurally responsive 1-azaallyl ligand could engender unusual and unexpected reactivity. To this end, we designed phosphine imine ligand 1 H (Scheme , left), a proligand to a phosphine 1-azaallyl ligand ( 1 ), by deprotonation at C 2 . Previously, we showed that an octahedral ruthenium complex with 1 exhibited only a κ 2 -P,N coordination mode.…”

“…The proligand 1 H reacts rapidly at room temperature with PdCl­(Me)­(COD) to give 2 , the structure of which was confirmed by single-crystal X-ray crystallography (Scheme ). The complex has a slightly distorted square planar geometry, as evidenced by a τ 4 value of 0.10 (for a perfect square plane, τ 4 = 0).…”

“…A 1 H– 13 C HSQC NMR experiment reveals a correlation from each methyl to the quaternary carbon C 2 at 117.2 ppm (see Scheme for numbering). The location of this signal suggests that the carbon atoms of the 1-azaallyl moiety are not bound to the metal center. ,,, A 1 H DOSY NMR analysis (Figure S24) of 3 revealed that the compound diffuses at a rate similar to that of a related dimer ( 5 , vide infra) and slower than that of a monomer ( 4 , vide infra). This supports the assignment of 3 as a dimer in solution.…”

Changes in ligand coordination mode induce bimetallic C–C coupling pathways

“…40–75 ppm (Table S1†). 36,47 Rather, the chemical shift is only ca. 3 ppm downfield from the analogous signal in 1 that has a μ-N binding mode of the 1-azaallyl fragment.…”

Operationally unsaturated ruthenium complex stabilized by a phosphine 1-azaallyl ligand

“…23 We have previously reported the synthesis and coordination chemistry of a ligand [Ph 2 P(C 6 H 4 )NCHC(CH 3 ) 2 ] − (L1) bearing phosphine and 1-azaallyl donor groups. [24][25][26] This ligand exhibits a broad range of coordination modes that depend on the metal, metal oxidation state, and the presence of additional L-donor ligands. In the presence of pyridine, a κ 2 -P,N mode was enforced to give coordinatively saturated Ru(II) or Pd(II) complexes (F and G, respectively).…”