σ-GeH and Germyl Cationic Pt(II) Complexes

Abstract

The low electron count Pt(II) complexes [Pt(NHC′)(NHC)]-[BAr F ] (where NHC is a N-heterocyclic carbene ligand and NHC′ its metalated form) react with tertiary hydrogermanes HGeR 3 at room temperature to generate the 14-electron platinum(II) germyl derivatives [Pt(GeR 3 )(NHC) 2 ][BAr F ]. Low-temperature NMR studies allowed us to detect and characterize spectroscopically some of the σ-GeH intermediates [Pt(η 2 -HGeR 3 )(NHC′)(NHC)][BAr F ] that evolve into the platinum-germyl species. One of these compounds has been characterized by X-ray diffraction studies, and the interaction of the H−Ge bond with the platinum center has been analyzed in detail by computational methods, which suggest that the main contribution is the donation of the H−Ge to a σ*(Pt−C) orbital, but backdonation from the platinum to the σ*(Ge−H) orbital is significant. Primary and secondary hydrogermanes also produce the corresponding platinum-germyl complexes, a result that contrasts with the reactivity observed with primary silanes, in which carbon−silicon bond-forming reactions have been reported. According to density functional theory calculations, the formation of Pt−Ge/C−H bonds is both kinetically and thermodynamically preferred over the competitive reaction pathway leading to Pt−H/C−Ge bonds.

Synthesis and Base Pairing Properties of Platinum(II) Nucleosides Based on Uracil

“…27 We were unable to calculate the JC,H coupling due to partial overlap with the phosphine signals. Although a wide variety of organometallic compounds with agostic interactions have been reported, [28][29][30][31][32][33][34][35][36] this is the first example of a nucleobase complex with such interaction.…”

“…Agostic interactions are "3-center-2electron interactions involving M−H−C", with the M•••H bond being mostly covalent 27 and are frequent in Pt compounds. [28][29][30][31][32] Indeed, in the 1 H NMR (DMSO-d6) of the pyrimidine complexes 1-4 the platinum satellites indicate a JPt,H couplings of 58-66 Hz. The H-6 signal, when compared with that of the ligand precursors, undergoes a significant upfield shift upon metalation (1.70 ppm) for 1 and 2, and a similar tendency is also observed for the 13 C of C6.…”

Synthesis and Base Pairing Properties of Platinum(II) Nucleosides Based on Uracil

“…Agostic interactions are "3-center-2electron interactions involving M−H−C", with the M•••H bond being mostly covalent 27 and are frequent in Pt compounds. [28][29][30][31][32] Indeed, in the 1 H NMR (DMSO-d6) of the pyrimidine complexes 1-4 the platinum satellites indicate a JPt,H couplings of 58-66 Hz. The H-6 signal, when compared with that of the ligand precursors, undergoes a significant upfield shift upon metalation (1.70 ppm) for 1 and 2, and a similar tendency is also observed for the 13 C of C6.…”

“…27 We were unable to calculate the JC,H coupling due to partial overlap with the phosphine signals. Although a wide variety of organometallic compounds with agostic interactions have been reported, [28][29][30][31][32][33][34][35][36] this is the first example of a nucleobase complex with such interaction. Self-Base-Pairing Interestingly, the chemical shift for the NH group of complex 1 in CDCl3 is highly dependent on the concentration.…”