57137-73-2Relevant articles and documents
E-H Bond Activations and Hydrosilylation Catalysis with Iron and Cobalt Metalloboranes
Nesbit, Mark A.,Suess, Daniel L. M.,Peters, Jonas C.
, p. 4741 - 4752 (2015/10/28)
An exciting challenge in transition metal catalyst design is to explore whether earth-abundant base metals such as Fe, Co, and Ni can mediate two-electron reductive transformations that their precious metal counterparts (e.g., Ru, Rh, Ir, and Pd) are better known to catalyze. Organometallic metalloboranes are an interesting design concept in this regard because they can serve as organometallic frustrated Lewis pairs. To build on prior studies with nickel metalloboranes featuring the DPB and PhDPBMes ligands in the context of H2 and silane activation and catalysis (DPB = bis(o-diisopropylphosphinophenyl)phenylborane, PhDPBMes = bis(o-diphenylphosphinophenyl)mesitylborane), we now explore the reactivity of iron, [(DPB)Fe]2(N2), 1, and cobalt, (DPB)Co(N2), 2, metalloboranes toward a series of substrates with E-H bonds (E = O, S, C, N) including phenol, thiophenol, benzo[h]quinoline, and 8-aminoquinoline. In addition to displaying high stoichiometric E-H bond activation reactivity, complexes 1 and 2 prove to be more active catalysts for the hydrosilylation of ketones and aldehydes with diphenylsilane relative to (PhDPBMes)Ni. Indeed, 2 appears to be the most active homogeneous cobalt catalyst reported to date for the hydrosilylation of acetophenone under the conditions studied.
Catalytic enantioselective hydrosilylation of ketones with rhodium- phosphite complexes containing a TADDOLate and a dihydrooxazole unit
Heldmann, Dieter K.,Seebach, Dieter
, p. 1096 - 1110 (2007/10/03)
New types of chiral phosphorus/nitrogen ligands, capable of forming six- membered-ring metal chelates have been prepared from α,α,α',α'-tetraaryl- 1,2-dioxolane-4,5-dimethanols (TADDOLs), PCl3, and dihydrooxazole alcohols (from amino acids) (7 in Scheme 1). The X-ray crystal structure of a Rh complex of one of these ligands, 8b, has been determined (Scheme 2 and Fig.). Enantioselective hydrosilylations of dialkyl and aryl alkyl ketones with Ph2SiH2/0.01 equiv. Rh1·7 have been studied and found to provide secondary alcohols in enantiomer ratios of up to 97:3 (Scheme 3 and Table). The ligand prepared from (R,R)-TADDOL and the (R)-valine-derived (R)-α,α- dimethyl-4-isopropyl-4,5-dihydrooxazole-2-methanol gives better results than the (R,R,S)-isomer (7d vs. 7c in Scheme 3), and an i-Pr group on the 4,5- dihydrooxazole ring gives rise to a slightly better selectivity than a Ph group. With the (R,R,R)-ligands the hydrogen transfer occurs from the Re face of the oxo groups (Scheme 4).
