Hydroamination of isocyanates and isothiocyanates by alkaline earth metal initiators supported by a bulky iminopyrrolyl ligand†
Abstract
A series of new heteroleptic alkaline earth (Ae) metal complexes of general formula [{(Ph2CHN![[double bond, length as m-dash]](https://www.rsc.org/images/entities/char_e001.gif)
CH)2C4H2N}AeI(THF)3] {Ae = Ca (2), Sr (3), and Ba (4)} were synthesized via salt metathesis by reacting potassium salt of ligand 1-K [{(Ph2CHNCH)2C4H2N}K(THF)2] with anhydrous alkaline earth metal diiodides (AeI2). The homoleptic calcium and barium complexes [{(Ph2CHNCH)2C4H2N}2Ae] [Ae = Ca (5), Ba (6)] were prepared by treating metal bis-hexamethyldisilazide [Ae{N(SiMe3)2}2(THF)2] with the protic ligand 1-H [(Ph2CH–NCH)2C4H2NH] in a 1 : 2 molar ratio. Calcium complex 5 was used as an active pre-catalyst for the addition of N–H bond of arylamines across the heterocumulenes such as phenylisocyanate (PhNCO) and phenylisothiocyanate (PhNCS) under neat conditions, and up to 99% yields of the corresponding urea and thiourea derivatives were obtained.
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