Titanium complexes of amidophosphinimide ligands

Alhomaidan, Osamah; Beddie, Chad; Bai, Guangcai; Stephan, Douglas W.

doi:10.1039/b816184d

Cited by 10 publications

(6 citation statements)

References 41 publications

(108 reference statements)

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“…22 . n-BuLi (22.66 mmol, 1.7 M in THF, 13.3 mL) was added dropwise to a solution of N,N 0 -dimethylethylenediamine (1.0 g, 11.34 mmol) in THF (20 mL).…”

Section: ' Experimental Sectionmentioning

confidence: 95%

Nickel(II) and Palladium(II) Bis-Aminophosphine Pincer Complexes

Gwynne

Stephan

2011

Organometallics

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Chelating ligands have proven instrumental in the development of new catalysts; furthermore trans-chelating "pincer" ligands have garnered considerable attention over the years. 1À13 The most extensively investigated pincer complexes feature ligands based on a meta-substituted arene skeleton (PCP). Variations of the PCP-pincer framework have been shown to alter the electronic and steric properties of the corresponding metal complexes, resulting in unique reactivity. 14,15 Aminophosphine chelating ligands of the form (linker)-(NR 0 PR 2 ) 2 have also garnered attention, as such ligands are readily prepared from diamines and chlorophosphines. 5,16 While linked diaminophosphine ligands such as (CH 2 N(R 0 )PR 2 ) 2 (R 0 = H, alkyl; R = alkyl, aryl) have been reported by Wollins, 17 Gusev, 9 Vogt, 16 and others, 18À21 investigations of PCP aminophosphine-based pincer ligand complexes have received less attention. 10 We were drawn to these systems, as such ligands offer adjacent P and N donors, suggesting the possibility of unique binding modes and thus subsequent reactivity. In this regard, the only report in which the N atom of an aminophosphine has been shown to participate in binding to a metal was recently reported by Palacios et al. In this case a bis-aminophosphine ligand was shown to bind to Ru via both P atoms as well as one of the amino NH groups, affording the Ru cation [Cp*Ru(k 3 P,N,P-(iPr 2 PNH) 2 C 6 H 10 ] + . 21 In this paper, we describe the synthesis and characterization of Ni and Pd complexes of bis-aminophosphine chelating ligands. Interestingly, these ligands are shown to readily adopt two tridentate binding modes. Participation of the secondary N adjacent to P affords k 3 P,N,P ligands that incorporate three-membered NPM metallacycles. Alternatively, metalation of the alkyl chain in the ligand backbone affords k 3 P,C,P pincer complexes.

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“…22 . n-BuLi (22.66 mmol, 1.7 M in THF, 13.3 mL) was added dropwise to a solution of N,N 0 -dimethylethylenediamine (1.0 g, 11.34 mmol) in THF (20 mL).…”

Section: ' Experimental Sectionmentioning

confidence: 95%

Nickel(II) and Palladium(II) Bis-Aminophosphine Pincer Complexes

Gwynne

Stephan

2011

Organometallics

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“…What makes these ligands so intriguing is their unique electronic structure; they can act as both strong σ- and π-donors due to their ylide-like structure. , Therefore, it was thought that phosphinimines and/or phosphinimides would be well suited for stabilizing high oxidation state, coordinatively unsaturated ruthenium carbene complexes that are common intermediates during OM. Additionally, phosphinimides have been used in place of cyclopentadienyl ligands for d 0 metallocene olefin polymerization catalysts. − A significant benefit seen for phosphinimide ligands was that they provided steric protection to the catalysts, but they also facilitated alkene binding because the bulkiness of the ligand was further removed from the metal due to the nitrogen spacer . It was anticipated that phosphinimine ligands would retain many of the same steric advantages as their anionic forms, and therefore, these species were targeted for further study.…”

Section: Introductionmentioning

confidence: 69%

Ruthenium Phosphinimine Complex as a Fast-Initiating Olefin Metathesis Catalyst with Competing Catalytic Cycles

2022

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A ruthenium-based olefin metathesis (OM) catalyst bearing a monodentate triphenylphosphinimine ligand, Ru1, was synthesized, characterized, and its activity for the homocoupling of terminal alkenes was investigated. Utilizing 1-hexene as a model substrate, the empirical rate law for Ru1 was found to be first-order in alkene and complex (indicating that both species were involved in the rate-limiting step), with a rate constant of 0.697 ± 0.050 M–1 s–1. Moreover, the experimentally determined activation parameters ΔS ⧧ and ΔH ⧧ (−48.7 ± 5.1 eu and 3.19 ± 0.15 kcal/mol, respectively) were consistent with an associative or associative interchange ligand substitution reaction. When considering the ΔG ⧧ (298 K) value of 17.7 kcal/mol, Ru1 ranked among the fastest initiating ruthenium-based OM catalysts reported in the literature. Density functional theory (DFT) calculations were also performed to explore potential catalytic mechanisms. Two pathways were considered: a traditional mechanism where the phosphinimine ligand de-coordinated and an alternative mechanism where the phosphine donor de-coordinated. Although the energy differences between the two pathways were typically fairly small (1.4–3.5 kcal/mol), the alternative pathway with phosphine de-coordination was energetically more favorable. It is anticipated, however, that both cycles are working in tandem during the catalytic reaction. In addition to kinetic studies, the stability of Ru1 was explored using 1-hexene as a model substrate. The phosphinimine catalyst was found to be mildly oxygen-sensitive and moisture-tolerant. Furthermore, Ru1 was determined to be prone to bimolecular decomposition, through the crystallographic characterization of a key degradation product. There was also strong evidence for NH exchange between the tricyclohexylphosphine and triphenylphosphinimine moieties. Lastly, the substrate scope of Ru1 in regard to α-olefins was explored. Catalytic efficiency dropped with more electron-deficient alkenes, as well as with increasing steric bulk on the substrate, which was consistent with the proposed catalytic mechanism.

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“…The Staudinger reaction with TMS‐N 3 is well documented for the preparation of alkyl‐ or aryl‐substituted species such as Ph 3 P=N–SiMe 3 , Me 3 P=N–SiMe 3 or t Bu 3 P=N–SiMe 3 which have been used as precursors for strongly electron‐donating phosphiniminato ligands, finally for proazaphosphatrane N(CH 2 CH 2 NCH 3 ) 3 P …”

Section: Resultsmentioning

confidence: 99%

“…The Staudinger reaction with TMS-N 3 is well documented for the preparation of alkyl-or aryl-substituted species such as Ph 3 P=N-SiMe 3 , [26] Me 3 P=N-SiMe 3 [27] or tBu 3 P=N-SiMe 3 [28] which have been used as precursors for strongly electron-donating phosphiniminato ligands, finally for proazaphosphatrane N(CH 2 CH 2 NCH 3 ) 3 P. [29] P-amino-substituted derivatives include (Me 2 N) 3 P=N-SiMe 3 , [21,30] [(CH 2 ) 4 N] 3 P=N-SiMe 3 [31] and (Et 2 N) 3 P=N-SiMe 3 . [32] The stability of initially formed phosphazides (R 2 N) 3 P=N-N=N-SiMe 3 with respect to loss of molecular nitrogen depends on the bulkiness of substituents at the phosphorus atom.…”

Section: (R 2 N) 3 P=n-sime 3 Derivativesmentioning

confidence: 99%

Mono‐Phosphazenyl Phosphines (R₂N)₃P=N–P(NR₂)₂ – Strong P‐Bases, P‐Donors, and P‐Nucleophiles for the Construction of Chelates

Kögel

Ullrich

Kovačević

et al. 2020

Zeitschrift anorg allge chemie

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We present a convenient three‐step synthesis of amino substituted phosphazenyl phosphines of the general formula (R2N)3P=N–P(NR2)2 [NR2 = N(CH2)4, N(CH2)5, N(CH2)6]. These easily accessible mixed valent compounds display a surprisingly high proton affinity and basicity in the same range as the corresponding Schwesinger diphosphazene (Me2N)3P=N–P=NEt(NMe2)2 (Et‐P2) and Verkade's proazaphosphatrane superbases. Within the central [PIII–N=PV] scaffold, the phosphine PIII and not the phosphazene NIII atom is the center of highest proton affinity, basicity and donor strength. As P‐bases, the title compounds display calculated proton affinities between 265.8 (NR2 = NMe2) and 274.7 kcal·mol–1 [NR2 = N(CH2)4] and pKBH+ values between 26.4 (NR2 = NMe2) and 31.5 [NR2 = N(CH2)4] on the acetonitrile scale. As P‐nucleophiles, they are key intermediates in the synthesis of hyperbasic bis(diphosphazene) proton sponges, chiral bis(diphosphazene) proton pincers, bisphosphazides, and superbasic P2‐bisylides. Their Staudinger reactions as nucleophile towards 1,8‐diazidonaphthalene leading to 1,8‐naphthalene‐bisphosphazides is described in detail. The donor strength of the title compounds towards fragments [Se] and [Ni(CO)3] is in the same range as that of N‐heterocyclic carbenes.

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Titanium complexes of amidophosphinimide ligands

Cited by 10 publications

References 41 publications

Nickel(II) and Palladium(II) Bis-Aminophosphine Pincer Complexes

Nickel(II) and Palladium(II) Bis-Aminophosphine Pincer Complexes

Ruthenium Phosphinimine Complex as a Fast-Initiating Olefin Metathesis Catalyst with Competing Catalytic Cycles

Mono‐Phosphazenyl Phosphines (R₂N)₃P=N–P(NR₂)₂ – Strong P‐Bases, P‐Donors, and P‐Nucleophiles for the Construction of Chelates

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Titanium complexes of amidophosphinimide ligands

Cited by 10 publications

References 41 publications

Nickel(II) and Palladium(II) Bis-Aminophosphine Pincer Complexes

Nickel(II) and Palladium(II) Bis-Aminophosphine Pincer Complexes

Ruthenium Phosphinimine Complex as a Fast-Initiating Olefin Metathesis Catalyst with Competing Catalytic Cycles

Mono‐Phosphazenyl Phosphines (R2N)3P=N–P(NR2)2 – Strong P‐Bases, P‐Donors, and P‐Nucleophiles for the Construction of Chelates

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Mono‐Phosphazenyl Phosphines (R₂N)₃P=N–P(NR₂)₂ – Strong P‐Bases, P‐Donors, and P‐Nucleophiles for the Construction of Chelates