Examining the Modular Synthesis of [Cp*Rh] Monohydrides Supported by Chelating Diphosphine Ligands

[Cp*Rh] hydride complexes are invoked as intermediates in certain catalytic cycles, but few of these species have been successfully prepared and isolated, contributing to a relative shortage information on the properties such species. Here, synthesis, isolation, characterization two hydrides reported; supported by chelating diphosphine ligands bis(diphenylphosphino)methane (dppm) 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (Xantphos). In both systems, reduction precursor Rh(III) chloride with Na(Hg) results clean formation isolable, formally 18e– Rh(I) species, subsequent protonation addition near-stoichiometric quantities anilinium triflate returns high yields desired monohydride complexes. Single-crystal X-ray diffraction data for compounds provide evidence direct Rh–H interactions, confirmed complementary infrared spectra showing stretching frequencies at 1982 cm–1 (for dppm-supported hydride) 1936 Xantphos-supported hydride). Findings from comprehensive multinuclear NMR experiments reveal unique especially rich spin systems hydride; multifrequency studies concert spectral simulations enabled full splitting patterns attributable couplings involving heterotopic methylene protons this complex. When they taken together prior reports related monohydrides, show that reduction/protonation reaction sequence is modular preparation monohydrides diverse spanning four- eight-membered rhodacycles.