The synthesis and structural characterization of three-coordinate iron(II) and cobalt(II) complexes supported by new N-phosphinoamidinate ligands is reported, along with the successful application of these complexes as precatalysts for the challenging room-temperature hydrosilylation of carbonyl compounds to afford alcohols upon workup. Under the rigorous screening conditions employed (0.015 mol % Fe) for the reduction of acetophenone, the well-defined iron(II) amido precatalyst 2b, featuring bulky N-2,6-diisopropylphenyl and di-tert-butylphosphino moieties within the N-phosphinoamidinate ligand, exhibited exceptional catalytic performance. Further experimentation revealed that the yield achieved in the hydrosilylation of acetophenone employing 2b was unaltered when conducting reactions in the absence of light, in the presence of excess mercury, or under solvent-free conditions. Notably, precatalyst 2b was found to exhibit the broadest substrate scope reported to date for such room-temperature iron-catalyzed carbonyl hydrosilylations en route to alcohols, enabling the chemoselective reduction of structurally diverse aldehydes and ketones, as well as for the first time esters, at remarkably low loadings (0.01−1.0 mol % Fe) and using only 1 equiv of phenylsilane reductant.

A series of N-heterocyclic carbene (NHC) complexes of Ge(II) were synthesized and structurally characterized. Unlike previous observations, the carbenic carbon-germanium bond length does not vary systematically with the electronic demands of the substituents on the germanium center. Computational analysis of the energetic and structural metrics of model compounds is consistent with a lack of a substituent effect on the carbenic carbon-germanium bond length.

The first example of PSiN mixed-donor silyl pincer ligation is described. Studies involving platinum group metal complexes of [(2-(t)Bu(2)PC(6)H(4))(2-Me(2)NC(6)H(4))SiMe](-) ((t)Bu-PSiN-Me) confirmed that the ligand amino donor is labile. Within the coordination sphere of Ru, (t)Bu-PSiN-Me is transformed into a PSiC ligand via multiple C-H bond activation events.

The synthesis and characterization of a series of structurally varied N-phosphinoamidinate-ligated cobalt complexes is described, along with the successful application of these and a related iron complex as precatalysts in the isomerization–hydroboration of terminal, geminal, and internal alkenes. These reactions proceed under mild conditions (23–65 °C), at relatively low base-metal loadings (1–5 mol %), typically without cosolvent, and with high terminal hydroboration selectivity across a broad spectrum of branched alkenes. With some of the alkene substrates examined, the N-phosphinoamidinate-ligated precatalysts employed herein are shown to provide alternative terminal selectivity versus other previously reported precatalyst classes for such transformations. Reports of terminal-selective metal-catalyzed alkene isomerization–hydroboration disclosed thus far in the literature employ pinacolborane (HBPin); while effective in the system herein, we also report the first examples of such transformations employing either 1,3-dimethyl-1,3-diaza-2-boracyclopentane or benzo-1,3,2-diazaborolane. The application of these 1,3,2-diazaborolanes in place of HBPin in some instances enables novel terminal selectivity in the isomerization–hydroboration of branched alkenes.

Single defluorination of aryl polyfluoromethyl functionalities is achieved by both intra- and intermolecular silylium cation/phosphine Lewis pairs. Phosphine-captured aryl fluoromethyl cations are then treated with Brønsted base to complete the first mono-hydrodefluorinations of PhCF , Ph CF , and PhCF .