A Monometallic Rh(III) Tetraphosphine Complex:  Reductive Activation of CH₂Cl₂ and Selective Meso to Racemic Tetraphosphine Ligand Isomerization

Abstract

The first Rh complex with an eta(4)-coordinated rac-et,ph-P4 ligand [et,ph-P4 = (Et2PCH2CH2)(Ph)PCH2P(Ph)(CH2CH2PEt2)] has been synthesized by reacting [Rh(nbd)2]BF4 with meso- or rac-et,ph-P4 in dichloromethane. The reaction occurs fairly rapidly at room temperature to form [rac-RhCl2(eta(4)-et,ph-P4)](+) in high yields, regardless of whether one starts with mixed or even pure meso-et,ph-P4 ligand. This unusual and highly selective metal assisted isomerization of the meso-et,ph-P4 ligand to its rac-et,ph-P4 disastereomer will be discussed.

Synthesis of Monomeric Fe(II) and Ru(II) Complexes of Tetradentate Phosphines

“…To facilitate the formation of cis-R metal complexes, we focused on the racemic diastereomer of the ligand. Work with related rhodium complexes 32 has shown that coordination of the meso form generates a less stable complex because of unfavorable steric factors.…”

Mechanistic Insights into the One‐Pot Synthesis of Propargylamines from Terminal Alkynes and Amines in Chlorinated Solvents Catalyzed by Gold Compounds and Nanoparticles

“…[7] The activation of CH 2 Cl 2 by late transition metals has been documented for Co I , [8] Rh I , [9] Rh III , [10] Ru II , [11] Pd, [12] and Pt 0 [12] complexes. The activation of the C À Cl bond usually affords M À CH 2 Cl or M À CH 2 À M organometallic compounds.…”

Synthesis, Characterization, and Transition-Metal Complexes of 3,4-Diazaphospholanes

“…For complexes 29 and 27, treatment with hydrogen gas accelerated the chloride abstraction (Scheme 5). Activation of chlorinated solvents by Rh(I) complexes is not unprecedented, [53][54][55][56][57][58][59][60] but most examples yield the product of oxidative addition. [53][54][55][56][58][59][60] Generally, oxidative addition of CH 2 X 2 (X ) Cl, Br, I) to Rh(I) is enhanced by electron-donating ligands, but as our data have established (vide supra), the 3,4-diazaphospholanes are electron deficient, which argues against an oxidative addition pathway.…”

“…[53][54][55][56][58][59][60] Generally, oxidative addition of CH 2 X 2 (X ) Cl, Br, I) to Rh(I) is enhanced by electron-donating ligands, but as our data have established (vide supra), the 3,4-diazaphospholanes are electron deficient, which argues against an oxidative addition pathway. 57,58 Vrieze and co-workers 58 documented a reaction where a [L 3 RhCl] (L ) tridentate amine) complex oxidatively added methylene chloride, the product of which was indefinitely stable under rigorous air-free conditions. Upon exposure to O 2 and water, however, it decomposes to [L 3 RhCl 3 ].…”