s-trans-Diene Complexes of a First-Row Transition Metal. Half-Sandwich s-trans-η4-1,3-Diene Nitrosyl Complexes of Chromium

Norman, David; Ferguson, Michael J.; McDonald, Robert; Stryker, Jeffrey M.

doi:10.1021/om050847+

Cited by 5 publications

(3 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The overall molecular geometry of ( iPr PDI)Fe(η 4 -C 4 H 6 ) is similar to ( iPr PDAI)Fe(η 4 -C 4 H 6 ) with both compounds containing a relatively unusual trans-butadiene ligand. 39,40 The bond distances in the bis(aldimino)chelate are consistent with two electron reduction and indicate a ferrous oxidation state. The distortions in N imine -C imine and C imine -C ipso bond distances are comparable to the bis(imino)pyridine variant with a slightly more pronounced C imine -C ipso contraction for the aldimino example.…”

Section: ' Results and Discussionmentioning

confidence: 78%

Synthesis, Electronic Structure, and Catalytic Activity of Reduced Bis(aldimino)pyridine Iron Compounds: Experimental Evidence for Ligand Participation

et al. 2011

View full text Add to dashboard Cite

The two-electron reduction chemistry of the aryl-substituted bis(aldimino)pyridine iron dibromide, ((iPr)PDAI)FeBr(2) ((iPr)PDAI = 2,6-(2,6-(i)Pr(2)-C(6)H(3)-N═CH)(2)C(5)H(3)N), was explored with the goal of generating catalytically active iron compounds and comparing the electronic structure of the resulting compounds to the more well studied ketimine derivatives. Reduction of ((iPr)PDAI)FeBr(2) with excess 0.5% Na(Hg) in toluene solution under an N(2) atmosphere furnished the η(6)-arene complex, ((iPr)PDAI)Fe(η(6)-C(7)H(8)) rather than a dinitrogen derivative. Over time in pentane or diethyl ether solution, ((iPr)PDAI)Fe(η(6)-C(7)H(8)) underwent loss of arene and furnished the dimeric iron compound, [((iPr)PDAI)Fe](2). Crystallographic characterization established a diiron compound bridged through an η(2)-π interaction with an imine arm on an adjacent chelate. Superconducting quantum interference device (SQUID) magnetometry established two high spin ferrous centers each coupled to a triplet dianionic bis(aldimino)pyridine chelate. The data were modeled with two strongly antiferromagnetically coupled, high spin iron(II) centers each with an S = 1 [PDAI](2-) chelate. Two electron reduction of ((iPr)PDAI)FeBr(2) in the presence of 1,3-butadiene furnished ((iPr)PDAI)Fe(η(4)-C(4)H(6)), which serves as a precatalyst for olefin hydrogenation with modest turnover frequencies and catalyst lifetimes. Substitution of the trans-coordinated 1,3-butadiene ligand was accomplished with carbon monoxide and N,N-4-dimethylaminopyridine (DMAP) and furnished ((iPr)PDAI)Fe(CO)(2) and ((iPr)PDAI)Fe(DMAP), respectively. The molecular and electronic structures of these compounds were established by X-ray diffraction, NMR and Mössbauer spectroscopy, and the results compared to the previously studied ketimine variants.

show abstract

Section: ' Results and Discussionmentioning

confidence: 78%

Synthesis, Electronic Structure, and Catalytic Activity of Reduced Bis(aldimino)pyridine Iron Compounds: Experimental Evidence for Ligand Participation

et al. 2011

View full text Add to dashboard Cite

show abstract

“…Although the piperylene fragment exhibited positional disorder in the unit cell (half‐occupancy in either of two orientations), the structure provided unambiguous support for an s‐ trans coordination geometry. As such, ( Me (Et)PDI)Fe(η 4 ‐piperylene), like the parent butadiene complex, is one of few known s‐ trans diene complexes, especially with 3d metals –. Full‐molecule density functional theory using the M06‐L functional reproduced the experimentally observed preference for s‐ trans butadiene and piperylene coordination.…”

Section: Resultsmentioning

confidence: 83%

Pyridine(diimine) Iron Diene Complexes Relevant to Catalytic [2+2]‐Cycloaddition Reactions

et al. 2019

View full text Add to dashboard Cite

The synthesis, characterization, and catalytic activity of pyridine(diimine) iron piperylene and isoprene complexes are described. These diene complexes are competent precatalysts for (i) the selective cross-[2 + 2]-cycloaddition of butadiene or (E)-piperylene with ethylene and α-olefins and (ii) the 1,4hydrovinylation of isoprene with ethylene. In the former case, kinetic analysis implicated the diamagnetic η 4piperylene complex as the resting state prior to rate-determining oxidative cyclization. Variable temperature 1 H NMR and EXSY experiments established that diene exchange from the diamagnetic, 18ecomplexes occurred rapidly in solution at ambient temperature through a dissociative mechanism. The solid-state structure of ð Me ðEtÞPDIÞFe(η 4 -piperylene) ( Me (Et)PDI = 2,6-(2,6-Me 2 -C 6 H 3 N=CEt) 2 C 5 H 3 N) was determined by singlecrystal X-ray diffraction and confirmed the s-trans coordination of the monosubstituted 1,3-diene. Possible relationships between ligand-controlled diene coordination geometry, metallacycle denticity, and chemoselectivity of iron-mediated cycloaddition reactions are discussed.

show abstract

“…The bond distances of the butadiene's erstwhile double bonds (C1-C2 and C1A-C2A, 1.378(4) Å) are identical to the formal single bond distance (C2-C2A, 1.379( 5)), indicating a modest transfer of electron density to the diene, which is consistent with other reported Cr-(η 4 -1,3-butadiene) complexes. [62][63][64][65] However, the relative Cr-C distances still favour a description as a π-complex rather than as the valence tautomeric metallacyclopentene. 66 The room temperature effective magnetic moment of 6, μ eff (295) = 3.8(1)μ B , is consistent with a quartet (S = 3/2) ground state.…”

Section: Dalton Transactions Papermentioning

confidence: 99%

A well-defined model system for the chromium-catalyzed selective oligomerization of ethylene

et al. 2013

View full text Add to dashboard Cite

The chromium(I) dinitrogen complex [(i-Pr2Ph)2nacnacCr]2(μ-η(2):η(2)-N2) catalyzes the selective trimerization of ethylene to 1-hexene at ambient pressure and temperature, and in the absence of any cocatalyst. After the conversion of the substrate, the catalyst cleanly converts to another chromium(I) species, namely [(i-Pr2Ph)2nacnacCr]2(μ-η(2):η(2)-C2H4), which is not catalytically active. Binuclear metallacycles containing Cr(II) have been prepared as candidates for catalytically active intermediates; however they are not kinetically competent to explain the catalysis. Turning thus to mononuclear metallacycles featuring Cr(III), a chromacyclopentane, chromacyclopentene and chromacyclopentadiene have been prepared as models of catalytic intermediates. Of these, the latter also catalyzes the trimerization of ethylene. These results support the proposal that selective ethylene oligomerization catalysis involves an interplay between Cr(I) ethylene complexes and mononuclear Cr(III) metallacycles.

show abstract

s-trans-Diene Complexes of a First-Row Transition Metal. Half-Sandwich s-trans-η⁴-1,3-Diene Nitrosyl Complexes of Chromium

Cited by 5 publications

References 15 publications

Synthesis, Electronic Structure, and Catalytic Activity of Reduced Bis(aldimino)pyridine Iron Compounds: Experimental Evidence for Ligand Participation

Synthesis, Electronic Structure, and Catalytic Activity of Reduced Bis(aldimino)pyridine Iron Compounds: Experimental Evidence for Ligand Participation

Pyridine(diimine) Iron Diene Complexes Relevant to Catalytic [2+2]‐Cycloaddition Reactions

A well-defined model system for the chromium-catalyzed selective oligomerization of ethylene

Contact Info

Product

Resources

About