POCN Ni(ii) pincer complexes: synthesis, characterization and evaluation of catalytic hydrosilylation and hydroboration activities

Abstract

(POCN)Ni(ii) complexes were found to mediate a variety of carbonyl hydroboration reactions, including chemoselective hydroboration of benzaldehyde and hydroborative reduction of amides.

Deoxygenation of Primary Amides to Amines with Pinacolborane Catalyzed by Ca[N(SiMe3)2]2(THF)2

“…The catalytic hydroboration of carbonyl moieties, such as aldehydes, ketones, and esters, with HBpin has been widely documented. − In striking contrast, the reduction of amides by hydroboration remains rarely explored. To date, only a limited range of metal-based catalysts, (Tris­(4,4-dimethyl-2-oxazolinyl)­phenylborate)­MgMe, {κ 2 -[Ph 2 P­(S)-NC 9 H 6 N]­Al­(Me) 2 }, POCN pincer Ni­(II), (2,2′:6′,2″-terpyridine)­V­(CH 2 SiMe 3 ) 2 , [(aNHC)­KN­(SiMe 3 )] 2 , Ln­[N­(SiMe 3 ) 2 ] 3 , , La 4 O­(acac) 10 , Cp* 2 ThMe 2 , and KO t Bu/BEt 3 , have been reported to be capable of promoting amide reduction through hydroboration (Scheme d). It is noteworthy that catalysts normally demonstrate activity only for reducing tertiary and secondary amides, and the catalysts that enable mediation of the challenging process of deoxygenative hydroboration of primary amides remain extremely scarce. ,,− …”

Hydrosilylation of Carbonyl Compounds Catalyzed by a Nickel Complex Bearing a PBP Ligand

“…To date, most reports on catalytic hydrosilylation have been focused on precious metals such as Ru, Rh, Ir or Pt; [2] however the scarcity and high cost of these metals press the need for cheaper and more abundant alternatives. Accordingly, over the past decade, we have witnessed the development of efficient catalysts based on first‐row transition metals, [5] being iron the metal that dominates the field, whereas studies with other metals such as nickel are less common [6–22] …”

“…To our knowledge, apart from Guan's catalyst, only three nickel pincer complexes have been tested in the catalytic hydrosilylation of aldehydes or ketones (Figure 1). [8,10,21,22] It is worth mentioning that all these catalysts proved to be quite active for the hydrosilylation of aldehydes, being Guan's system the most active one, but showed very low (if any) catalytic activity with ketones.…”

Deoxygenative hydroboration of primary, secondary, and tertiary amides: Catalyst‐free synthesis of various substituted amines

“…6 Recently, Khalimon et al reported the nickel catalyst (i-PrPOCNAr)NiMe]-promoted hydroboration of amides (acetamide and N-phenylpropanamide) using HBpin to produce borylamines. 7 Panda et al reported an efficient protocol for the Al-catalyzed hydroboration of tertiary amides at room temperate, 8 while Chen et al reported the hydroboration of secondary and tertiary amides using HBPin (2.4-6.0 equiv) in the presence of an yttrium catalyst Y[N(TMS) 2 ] 3 under heating (100-120 C). 9 Findlater et al reported the lanthanum (La 4 (O)(acac) 10…”