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Highly Chemoselective Hydroboration of Alkynes and Nitriles Catalyzed by Group 4 Metal Amidophosphine-Borane Complexes

Highly Chemoselective Hydroboration of Alkynes and Nitriles Catalyzed by Group 4 Metal Amidophosphine-Borane Complexes

Jayeeta Bhattacharjee, Adimulam Harinath, Kulsum Bano, Tarun K Panda

ACS Omega. 2020 Jan 10;5(3):1595-1606.

PMID: 32010834

Abstract:

We report a series of titanium and zirconium complexes supported by dianionic amidophosphine-borane ligands, synthesized by amine elimination and salt metathesis reactions. The TiIV complex [{Ph2P(BH3)N}2C6H4Ti(NMe2)2] (1) was obtained by the reaction between tetrakis-(dimethylamido)titanium(IV) and the protic aminophosphine-borane ligand [{Ph2P(BH3)NH}2C6H4] (LH2) at ambient temperature. Both the heteroleptic zirconium complexes-[η5-(C5H5)2Zr{Ph2P(BH3)N}2C6H4] (2) and [[{Ph2P(BH3)N}2C6H4]ZrCl2] (3)-and the homoleptic zirconium complex [[{Ph2P(BH3)N}2C6H4]2Zr] (4) were obtained in good yield by the salt metathesis reaction of either zirconocene dichloride [η5-(C5H5)2ZrCl2] or zirconium tetrachloride with the dilithium salt of the ligand [{Ph2P(BH3)NLi}2C6H4] (LLi2), which was prepared in situ. The molecular structures of the complexes 1, 2, and 4 in their solid states were confirmed by single-crystal X-ray diffraction analysis. Of these complexes, only titanium complex 1 acts as an effective catalyst for the facile hydroboration of terminal alkynes, yielding exclusive E-isomers. The hydroboration of organic nitriles yielded diborylamines with a broad substrate scope, including broad functional group compatibility. The mechanism of hydroboration occurs through the formation of titanium hydride as an active species.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP19756048	Tetrakis(dimethylamido)zirconium(IV)		19756-04-8	Price

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