Issue 7, 2019

Synthesis and catalytic activity of tridentate N-(2-pyridylethyl)-substituted bulky amidinates of calcium and strontium

Abstract

Metalation of the formamidine Dipp–N[double bond, length as m-dash]C(H)–N(H)–C2H4–Py (1a) and benzamidine Dipp–N[double bond, length as m-dash]C(Ph)–N(H)–C2H4–Py (1b) with [(thf)2M{N(SiMe3)2}2] (M = Ca, Sr) yields the corresponding homoleptic complexes [M{Dipp–N[double bond, length as m-dash]C(R)–N–C2H4–Py}2] (M/R = Ca/H (2a), Ca/Ph (2b), and Sr/Ph (3b)) regardless of the applied stoichiometry. Only during calciation of Dipp–N[double bond, length as m-dash]C(H)–N(H)–C2H4–Py (1a), the heteroleptic intermediate [{(Me3Si)2N}Ca{Dipp–N[double bond, length as m-dash]C(R)–N–C2H4–Py}]2 (2a′) has been observed. The formamidinate complex of strontium crystallizes as a tmeda adduct of the type [(tmeda)Sr{Dipp–N[double bond, length as m-dash]C(H)–N–C2H4–Py}2] (3a). Metalation of the pivalamidine Dipp–N[double bond, length as m-dash]C(tBu)–N(H)–C2H4–Py (1c) leads to the formation of heteroleptic mononuclear [{(Me3Si)2N}M{Dipp–N[double bond, length as m-dash]C(tBu)–N(H)–C2H4–Py}] (M = Ca (2c) and Sr (3c)) with a side-on bonding of the Dipp group to the alkaline earth metals. Calciation of chiral Dipp–N[double bond, length as m-dash]C(tBu)–N(H)–CH2CH(Me)–Py (R)-1d and (S)-1d with [(thf)2Ca{N(SiMe3)2}2] yields the homoleptic complexes [Ca{Dipp–N[double bond, length as m-dash]C(tBu)–N–CH2CH(Me)–Py}2] with the enantiomeric forms (R,R)-2d and (S,S)-2d regardless of the applied stoichiometry. The complexes 2c and 2d catalyze the intramolecular hydroamination of the aminoalkene 2,2-diphenylpent-4-enylamine yielding 2-methyl-4,4-diphenylpyrrolidine but the stereochemistry cannot be influenced by the chiral compounds (R,R)-2d and (S,S)-2d.

Graphical abstract: Synthesis and catalytic activity of tridentate N-(2-pyridylethyl)-substituted bulky amidinates of calcium and strontium

Supplementary files

Article information

Article type
Paper
Submitted
13 Dec 2018
Accepted
22 Jan 2019
First published
22 Jan 2019

Dalton Trans., 2019,48, 2479-2490

Synthesis and catalytic activity of tridentate N-(2-pyridylethyl)-substituted bulky amidinates of calcium and strontium

S. Krieck, D. Kalden, A. Oberheide, L. Seyfarth, H. Arndt, H. Görls and M. Westerhausen, Dalton Trans., 2019, 48, 2479 DOI: 10.1039/C8DT04905J

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements