Organometallic Complexes of Bulky, Optically Active, C₃-Symmetric Tris(4S-isopropyl-5,5-dimethyl-2-oxazolinyl)phenylborate (To^P*)

Abstract

A bulky, optically active monoanionic scorpionate ligand, tris(4S-isopropyl-5,5-dimethyl-2-oxazolinyl)phenylborate (ToP*), is synthesized from the naturally occurring amino acid l-valine as its lithium salt, Li[ToP*] (1). That compound is readily converted to the thallium complex Tl[ToP*] (2) and to the acid derivative H[ToP*] (3). Group 7 tricarbonyl complexes ToP*M(CO)3(M = Mn (4), Re (5)) are synthesized by the reaction of MBr(CO)5 and Li[ToP*] and are crystallographically characterized. The νCO bands in their infrared spectra indicate that π back-donation in the rhenium compounds is greater with ToP* than with non-methylated tris(4S-isopropyl-2-oxazolinyl)phenylborate (ToP). The reaction of H[ToP*] and ZnEt2 gives ToP*ZnEt (6), while ToP*ZnCl (7) is synthesized from Li[ToP*] and ZnCl2. The reaction of ToP*ZnCl and KOtBu followed by addition of PhSiH3 provides the zinc hydride complex ToP*ZnH (8). Compound 8 is the first example of a crystallographically characterized optically active zinc hydride. We tested its catalytic reactivity in the cross-dehydrocoupling of silanes and alcohols, which provided Si-chiral silanes with moderate enantioselectivity. Disciplines Chemistry CommentsReprinted (adapted) with permission from Organometallics 34 (2015) (5)) are synthesized by the reaction of MBr(CO) 5 and Li[To P *] and are crystallographically characterized. The ν CO bands in their infrared spectra indicate that π back-donation in the rhenium compounds is greater with To P * than with non-methylated tris(4S-isopropyl-2-oxazolinyl)phenylborate (To P ). The reaction of H[To P *] and ZnEt 2 gives To P *ZnEt (6), while To P *ZnCl (7) is synthesized from Li[To P *] and ZnCl 2 . The reaction of To P *ZnCl and KOtBu followed by addition of PhSiH 3 provides the zinc hydride complex To P *ZnH (8). Compound 8 is the first example of a crystallographically characterized optically active zinc hydride. We tested its catalytic reactivity in the cross-dehydrocoupling of silanes and alcohols, which provided Si-chiral silanes with moderate enantioselectivity.

Design and synthesis of coordination polymers with chelated units and their application in nanomaterials science

“…92,93,188,189 It is important that chiral CPs can be developed controllably by targeted choice of ligands or metal centers. 30,[190][191][192][193] Among the developed by now methods of designing chiral materials, it is worth noticing incorporation of chiral ligands, chiral templates, or chiral ancillary agents, and also spontaneous resolution without chiral auxiliary. 194 From this view, the most rational method of design of chiral CPs is integration of a chiral center into the structure, such as a chiral ligand; however, this process is not always convenient because of difficulty of a chiral ligand synthesis.…”

Hydrosilane σ‐Adduct Intermediates in an Adaptive Zinc‐Catalyzed Cross‐dehydrocoupling of Si−H and O−H Bonds

“…Basic catalysts such as sodium hydroxide overcome this limitation but are restricted to secondary and tertiary silanes, [21,22] as are B(C 6 F 5 ) 3 -catalyzed reactions. [23] Hydridozinc species also catalyze these crossdehydrocouplings; [24][25][26][27][28][29] however, a divergent picture of the fundamental nature of hydridozinc catalysts has emerged, obscuring design principles. In particular, catalytic product formation is observed with coordinatively saturated (ZnX 2 L 2 , 8electron) hydride and super-saturated (ZnX 2 L 3 , 10-electron) alkoxide pre-catalysts, as well as with dimeric hydride-bridged N-heterocyclic carbene-coordinated zinc pre-catalysts [24] which likely access lower coordinate catalytic sites (ZnX 2 L, 6-electron).…”

Synthesis and Characterization of Tris(oxazolinyl)borato Copper(II) and Copper(I) Complexes

“…In contrast, the neighboring tetrahedral zinc(II) hydride congeners are isolable as scorpionate‐supported species [30–35] and even as an NHC‐supported dihydride [36,37] . Some of these hydride compounds are inert, for example, to O 2 , and others are reactive in catalytic chemistry such as dehydrocoupling of silanes and alcohol [31,38] or hydrosilylation [39,40] .…”