1579211-45-2Relevant academic research and scientific papers
Inner- and Outer-Sphere Roles of Ruthenium Phosphido Complexes in the Hydrophosphination of Alkenes
Belli, Roman G.,Burton, Krista M. E.,Rufh, Stephanie A.,McDonald, Robert,Rosenberg, Lisa
, p. 5637 - 5646 (2015)
An inner-sphere synthetic cycle for the hydrophosphination of alkenes is proposed, based on observed [2 + 2] cycloaddition of a wide range of alkenes at a coordinatively unsaturated Ru=PR2 complex. Key intermediates in the cycle were prepared, and their reactions with various organic acid/base pairs were examined to identify both new ruthenium precursors and base cocatalysts that allow turnover of the proposed cycle. Two new cationic ruthenium indenyl phosphine complexes were isolated and structurally characterized. Although preliminary screening studies show the moderate activity of these and related neutral phosphido complexes for catalytic hydrophosphination of acrylonitrile by both HPPh2 and HPCy2, and comparable activity for the hydrophosphination of tert-butyl acrylate by HPPh2, no activity was observed for the analogous hydrophosphination of 1-hexene. This is attributed to strong binding of the substrate phosphine to the unsaturated, planar Ru - PR2 fragment generated in situ, which inhibits the inner-sphere, alkene cycloaddition mechanism. An alternative, outer-sphere Michael addition process, involving a saturated complex with a strongly nucleophilic pyramidal Ru-PR2 ligand, is proposed to rationalize the observed selectivity for catalytic hydrophosphination of activated, but not simple, alkenes. Implications for further catalyst development are discussed.
Hydrophosphination of Activated Alkenes by a Cobalt(I) Pincer Complex
Nolla-Saltiel, Roberto,Geer, Ana M.,Taylor, Laurence J.,Churchill, Olivia,Davies, E. Stephen,Lewis, William,Blake, Alexander J.,Kays, Deborah L.
supporting information, p. 3148 - 3157 (2020/06/08)
Herein we report the synthesis of three heteroleptic first-row transition metal(II) complexes containing carbazolido NNN pincer ligands and conversion to the corresponding metal(I)-carbonyl complexes via a reductive carbonylation route. These complexes are precatalysts for the hydrophosphination of activated alkenes, affording a cobalt-catalysed hydrophosphination process that solely and selectively yields the β addition (anti-Markovnikov) product. The scope of this transformation has been investigated using a variety of activated alkenes. Isolation and characterisation of substrate-coordinated intermediates reveal available coordination sites, which provide insight into the proposed catalytic cycle. (Figure presented.).
Visible Light Photocatalysis Using a Commercially Available Iron Compound
Pagano, Justin K.,Bange, Christine A.,Farmiloe, Sarah E.,Waterman, Rory
supporting information, p. 3891 - 3895 (2017/10/30)
[CpFe(CO)2]2 (1) (Cp = η5-C5H5) is an effective precatalyst for the hydrophosphination of alkenes with Ph2PH under visible light irradiation, which appears to be a unique way to promote metal-catalyzed hydrophosphination. Additionally, 1 is a photocatalyst for the dehydrogenation of amine boranes and formation of siloxanes from tertiary silanes. These reactions have similar, if not improved, reactivity over the same transformations using 1 or related CpFeMe(CO)2 under UV irradiation, consistent with the notion that hydrophosphination with 1 proceeds via formation of CpFe(CO)2?. These results demonstrate that catalyst selection can avail the use of commercially available LED bulbs as photon sources, potentially replacing mercury arc lamps or other energy intensive processes in known or new catalytic reactions.
Reactivity of ruthenium phosphido species generated through the deprotonation of a tripodal phosphine ligand and implications for hydrophosphination
Sues, Peter E.,Lough, Alan J.,Morris, Robert H.
, p. 4746 - 4760 (2014/04/17)
The fragmentation of the 1,1,2-tris(diphenylphosphino)ethane ligand in [RuCp((Ph2P)2CHCH2PPh2)][PF 6] (1) was explored through treatment with base under aprotic conditions. The neutral phosphido complex RuCp(PPh2CH - CHPPh 2)(PPh2) (2) with a (Z)-1,2-bis(diphenylphosphino)ethene (dppen) ligand was generated through a base-facilitated dehydrophosphination reaction. Installation of a bis(p-tolyl)phosphido ligand was attempted by combining bis(p-tolyl)phosphine with RuCp(dppen)Cl in the presence of KOtBu, but surprisingly, the unsymmetrical diphenylphosphido compound RuCp(Ph 2PCHCHP(p-tol)2)(PPh2) (5) was generated instead. The ligand rearrangement reaction was driven by the greater electron density on the bis(p-tolyl)phosphido moiety. Density functional theory calculations showed that fragmentation to the 1,2-disubstituted ligand was thermodynamically favored over the 1,1-disubstituted ligand and that intramolecular phosphido exchange was kinetically accessible at room temperature. The greater basicity of the bis(p-tolyl)phosphido ligand was experimentally verified by the measured pKaTHF of 28 for the acid/base pair [RuCp(Ph2P(o-C6H4)PPh2)(P(p-tolyl) 2H)]+/RuCp(Ph2P(o-C6H 4)PPh2)(P(p-tolyl)2) versus 25 for the acid/base pair [RuCp(Ph2P(o-C6H4)PPh 2)(PPh2H)]+/RuCp(Ph2P(o-C 6H4)PPh2)(PPh2) (7). For comparison, the approximate pKa THF values for free P(p-tolyl)2H/[K(crypt)]P(p- tolyl)2 and free PPh2H/[K(crypt)]PPh2 are 43 and 38, respectively. This is the first quantitative measurement of the large effect that coordination to a metal center, in this case ruthenium(II), has on the acidity of secondary phosphines. This is useful information for designing and understanding hydrophosphination catalysts. Complexes 2 and 7 are catalysts for the addition of PPh2H to acrylonitrile, but they deactivate fairly rapidly. The pKa THF measurements are consistent with a catalytic cycle involving a Michael addition step. Complex 2 in solution underwent a slow, unprecedented rearrangement of P-C, C-C, and C-H bonds to give crystalline Ru(C5(CH3)4(CH2C6H 5))(Ph2PCH2CH2PPh(o-C 6H4)PPh) (9) in high yields, demonstrating the unpredictable reactivity of phosphido ligands.
