Issue 40, 2022

Insertion chemistry of iron(ii) boryl complexes

Abstract

Iron(II) boryl complexes of the pyrrole-based pincer ligand, CyPNP (CyPNP = anion of 2,5-bis(dicyclohexylphophinomethyl)pyrrole) have been synthesized and their insertion reactivity interrogated. Compounds of the type [Fe(BE)(CyPNP)] (E = pinacholato or catecholato) can be generated by treatment of the precursors, [Fe(OPh)(py)(CyPNP)] or [FeMe(CyPNP)], with B2E2. The boryl complexes are meta stable, but permit additional reactivity with several unsaturated substrates. Reaction with alkynes, RC[triple bond, length as m-dash]CR′, leads to rapid insertion into the Fe–B bond to generate stable vinyl boronate complexes of the type [Fe(C{R}C{R′}BE)(CyPNP)] (R, R′ = H, Me, Ph, –C[triple bond, length as m-dash]CPh). Each of the compounds is five-coordinate in the solid state by virtue of coordination of one of the oxygen atoms of the boronate ester. Similar reaction with nitriles, RC[triple bond, length as m-dash]N (R = Ph, Me), results in facile de-cyanation to produce the correpsonding hydrocarbon complexes, [FeR(CyPNP)]. In the case of the bulky nitrile 1-AdCN, the insertion intermediate, [Fe(C{Ad}NBpin)(CyPNP)], has been isolated and structurally characterized. Treatment of the boryl complexes with styrene derivatives results in initial insertion to give an alkylboronate complex followed by either β-H elimination or protonation to give the products of C–H borylation and hydroboration, respectively.

Graphical abstract: Insertion chemistry of iron(ii) boryl complexes

Supplementary files

Article information

Article type
Paper
Submitted
02 Sep 2022
Accepted
21 Sep 2022
First published
26 Sep 2022

Dalton Trans., 2022,51, 15475-15483

Author version available

Insertion chemistry of iron(II) boryl complexes

A. L. Narro, H. D. Arman and Z. J. Tonzetich, Dalton Trans., 2022, 51, 15475 DOI: 10.1039/D2DT02879D

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