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 th… Show more
“…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.…”
The advances and problems associated with the preparation, properties and structure of coordination polymers with chelated units are presented and assessed.
“…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.…”
The advances and problems associated with the preparation, properties and structure of coordination polymers with chelated units are presented and assessed.
“…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).…”
Three-coordinate Ph BOX Me 2 ZnR ( Ph BOX Me 2 = phenyl-(4,4-dimethyl-oxazolinato; R=Me: 2 a, Et: 2 b) catalyzes the dehydrocoupling of primary or secondary silanes and alcohols to give silyl ethers and hydrogen, with high turnover numbers (TON; up to 10 7 ) under solvent-free conditions. Primary and secondary silanes react with small, medium, and large alcohols to give various degrees of substitution, from monoto tri-alkoxylation, whereas tri-substituted silanes do not react with MeOH under these conditions. The effect of coordinative unsaturation on the behavior of the Zn catalyst is revealed through a dramatic variation of both rate law and experimental rate constants, which depend on the concentrations of both the alcohol and hydrosilane reactants. That is, the catalyst adapts its mechanism to access the most facile and efficient conversion. In particular, either alcohol or hydrosilane binds to the open coordination site on the Ph BOX Me 2 ZnOR catalyst to form a Ph BOX Me 2 ZnOR(HOR) complex under one set of conditions or an unprecedented σ-adduct Ph BOX Me 2 ZnOR(HÀ SiR' 3 ) under other conditions. Saturation kinetics provide evidence for the latter species, in support of the hypothesis that σ-bond metathesis reactions involving four-centered electrocyclic 2σ-2σ transition states are preceded by σ-adducts.
“…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] .…”
The reaction of ToMTl (ToM=tris(4,4‐dimethyl‐2‐oxazolinyl)phenylborate) and CuBr2 in benzene at 60 °C provides ToMCuBr (1) as an entry‐point into tris(oxazolinyl)phenylborato copper chemistry. ToMCuOtBu (2) and ToMCuOAc (3) are prepared by the reactions of ToMCuBr with KOtBu and NaOAc, respectively. ToMCuOtBu is transformed into (ToMCuOH)2 (4) through hydrolysis. NMR, FT‐IR, and EPR spectroscopies are used to determine the electronic and structural properties of these copper(II) compounds, and the solid‐state structures were characterized by X‐ray crystallography. Reduction of copper is observed upon treatment of ToMCuOtBu with phenylsilane in an attempt to synthesize monomeric copper(II) hydride. ToMCu (5) and ToM2Cu (6) were independently synthesized and characterized for comparison.
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