Complexes featuring tridentate iminophosphorane ligands: Synthesis, reactivity, and catalysis

Multielectron Bond Cleavage Processes Enabled by Redox-Responsive Phosphinimide Ligands

“…In addition, the P–C Aryl bonds found in 2 are ∼0.05 Å shorter than those in 1 (Table S1). These latter differences suggest that the degree of covalency between chromium and nitrogen modulates the hyperconjugation within the σ*­(C–P) orbitals . Collectively, the bonding interactions between the PN ligands and the metal center can be interpreted as a rebalancing of the contributions of resonance structures classically ascribed to metal complexes of these ligands (Scheme ).…”

“…These latter differences suggest that the degree of covalency between chromium and nitrogen modulates the hyperconjugation within the σ*(C−P) orbitals. 12 Collectively, the bonding interactions between the PN ligands and the metal center can be interpreted as a rebalancing of the contributions of resonance structures classically ascribed to metal complexes of these ligands (Scheme 2). 13 In compound 1, resonance forms Attempts to prepare heteroleptic chromium(oxo)(imido) species via nitrosobenzene (PhNO) addition to 1 entailed complex metal speciation, consistent with competing N�O bond cleavage and N�N bond coupling reactions.…”

“…These ligands benefit from pronounced electronic and steric tunability via the selection of appropriate phosphorus substituents. Since the bonding interactions between the P and N atoms are influenced by negative hyperconjugation with the adjacent σ*­(C–P) orbitals, the identity of these substituents can markedly influence the electronic properties of N-coordinated metal ions. − In conjunction with the usage of sterically encumbering phosphorus substituents, these features have enabled the development of mononuclear Ti-based olefin polymerization catalysts , and electron-deficient lanthanide and actinide complexes. − We are specifically interested in the utility of PNs to stabilize redox-active, first-row transition-metal complexes and have found that iron and cobalt complexes of tripodal, multidentate PN frameworks engage in a range of single-electron-transfer reactivity. − For example, PN-ligated iron­(II) species readily mediate the inner sphere one-electron reduction of O 2 , and stoichiometric oxidation of (PN)-ligated iron­(III) species enables hydrogen atom abstraction processes to proceed at the PN nitrogen atom . In both cases, structural and computational studies evidence perturbations to the metal–PN bonding interactions upon one-electron reduction or oxidation of the complexes, suggesting that these ligands markedly influence the redox properties of their cognate-bound metal ion.…”

Probing the donor strength of yldiide ligands: synthesis, structure and reactivity of rhodium complexes with a PCylideN pincer ligand

“…Previous studies on the bis(iminophosphoranyl)methane ligand H 2 BIPM Tol ( L1 ) and related ligands have shown that their metallated derivatives may undergo substitution either at one of the nitrogen or at the methanide carbon atom. 20 a–f ,21,22 We assumed that this reactivity may be used for the convenient synthesis of an ylide ligand with an aminophosphonium group through substitution at the nitrogen atom. Indeed, phosphorylation of H 2 BIPM Tol ( L1 ) 23 to ligand L2 (PC Y (H)N) (Scheme 1 and the ESI†) was accomplished either via a step-wise or a one-pot reaction protocol: the first pathway involves the deprotonation of L1 with 1 equivalent of n -butyllithium and isolation of HBIPM Tol -Li, ( L1–Li ), followed by reaction with 1.1 equiv.…”

Electronic Effects in Phosphino‐Iminophosphorane PdII Complexes upon Varying the N Substituent

“…Iminophosphoranes behave as strong σ and π donors and have no acceptor character, so unlike imines, they are not reduced in presence of low‐valent metals [9] . Even if they remain significantly less investigated than their carbon congeners, some of their potential in transition‐metal catalyzed reactions has been explored [6,8b,10] . Earlier this year, we were interested in comparing the electronic properties of phosphonium ylides and iminophosphoranes focusing on square planar dicarbonyl Rh I complexes featuring a mixed phosphine‐ylide ligand built on a rigid ortho‐phenylene skeleton.…”