Cascade Activation of SiH, CH, and SiC Bonds at a Rhodium β-Diiminate Complex

σ-Silane Platinum(II) Complexes as Intermediates in C-Si Bond-Coupling Processes

Platinum complexes [Pt(NHC')(NHC)][BAr^F ] (in which NHC' denotes a cyclometalated N-heterocyclic carbene ligand, NHC) react with primary silanes RSiH₃ to afford the cyclometalated platinum(II) silyl complexes [Pt(NHC-SiHR')(NHC)][BAr^F ] through a process that involves the formation of C-Si and Pt-Si bonds with concomitant extrusion of H₂ . Low-temperature NMR studies indicate that the process proceeds through initial formation of the σ-SiH complexes [Pt(NHC')(NHC)(HSiH₂ R)][BAr^F ], which are stable at temperatures below -10 °C. At higher temperatures, activation of one Si-H bond followed by a C-Si coupling reaction generates an agostic SiH platinum hydride derivative [Pt(H)(NHC'-SiH₂ R)(NHC)][BAr^F ], which undergoes a second Si-H bond activation to afford the final products. Computational modeling of the reaction mechanism indicates that the stereochemistry of the silyl/hydride ligands after the first Si-H bond cleavage dictates the nature of the products, favoring the formation of a C-Si bond over a C-H bond, in contrast to previous results obtained for tertiary silanes. Furthermore, the process involves a trans-to-cis isomerization of the NHC ligand before the second Si-H bond cleavage.

On the non-innocence of “Nacnacs”: ligand-based reactivity in β-diketiminate supported coordination compounds

While β-diketiminate (BDI or ‘nacnac’) ligands have been widely adopted to stabilize a wide range of metal ions in multiple oxidation states and coordination numbers, in several occurrences these ligands do not behave as spectators and participate in reactivity.

Rhodium(ii) dimers without metal–metal bonds

Oxidation of (^MeBDI)Rh(cyclooctene) (^MeBDI = [2,6-Me₂C₆H₃NCMe]₂CH) with Br₂ or I₂ produces paramagnetic halide-bridged Rh^II dimers [(^MeBDI)Rh]₂(μ-X)₂ without a direct Rh–Rh bond.