This paper describes a cooperative iron–thiolate catalyst Cp*Fe­(1,2-Ph2PC6H4S)­(NCMe) (Cp*– = C5Me5 –, [1(NCMe)]) for regioselective hydroboration of aryl epoxide by pinacolborane (HBpin). The critical catalytic step involves the direct addition of epoxide to the catalyst rather than activation of the B–H bond of HBpin. Through iron–thiolate cooperation, [1(NCMe)] opens the aryl epoxide rings affording ferrous–alkoxide compounds. Notably, the ferrous–alkoxide intermediate (4) was structurally characterized after its isolation from the reaction of [1(NCMe)] with trans-2,3-diphenyloxirane. The more Lewis acidic hydroboranes such as H3B·THF and 9-BBN (BBN = bora­bicyclo­nonane) can also be captured by [1(NCMe)]. The resulting iron–borane adducts [1H­(BH2)] and [1H­(BBN)] feature an agnostic Fe···B–H interaction. DFT calculations indicate that the addition of HBpin across the iron–thiolate sites is endergonic by 12.9 kcal/mol, whereas it is exergonic by 20.2 kcal/mol with BH3 and 4.6 kcal/mol with 9-BBN. Combining the experimental data with theoretical studies, a mechanism of the substrate activation by [1(NCMe)], followed by HBpin addition, is proposed for the catalysis.

An iron dichloride complex [Fe]­Cl2 supported by a pincer phosphine–pyridine–imidazoline (PNNimid) ligand {[Fe]­Cl2 = (PNNimid)­FeCl2}, upon activation with NaHBEt3, catalyzes the isomerization of 1,1-disubstituted alkenyl boronates to synthetically valuable but previously difficult-to-access trisubstituted (Z)-alkenyl boronates with excellent regio- and stereoselectivity. The loading of the catalyst activator relative to iron was found to affect the selectivity and catalytic efficiency. In situ solvent-assisted electrospray ionization mass (SAESI-MS) studies revealed the generation of two catalytically competent species depending on the Fe/NaHBEt3 ratios: the reaction of [Fe]­Cl2 with 1.5 equiv NaHBEt3 predominantly formed a monohydride chloride [Fe]­HCl, while treatment with 3 equiv NaHBEt3 furnished a dihydride [Fe]­H2. In addition, the iron alkyl intermediates resulting from the insertion of the alkenyl boronate into the Fe–H bonds of [Fe]­HCl and [Fe]­H2 were successfully captured by SAESI-MS. The iron hydride catalysts are sensitive to the steric properties of the alkene substrates: the monohydride [Fe]­HCl is efficient for the synthesis of less hindered alkyl-bearing trisubstituted (Z)-alkenyl boronates, whereas the dihydride [Fe]­H2 is a favorable catalyst for generation of sterically more demanding aryl-substituted products. The synthetic utility of these trisubstituted (Z)-alkenyl boronate products was demonstrated by stereoselective synthesis of multisubstituted conjugated dienes and cyercene A.

Hydrido ruthenium complexes (POCNP)­RuH­(NBD) (NBD = norbornadiene) supported by N/O-bridged pincer ligands have been synthesized and characterized. The Ru complex containing a pincer ligand with an indolol scaffold exhibits high catalytic activity for the intermolecular aliphatic C–H bond silylation of amides and carbamides. The reaction proceeds selectively at the C–H bonds adjacent to the nitrogen atom to efficiently afford α-silyl amides and carbamides.