199Hg NMR of mercury-bridged transition metal clusters

Abstract

The 199Hg NMR data for the series of complexes (μ 3-η 2-C 2 tBu)(CO) 9Ru 3(μ-Hg)X (X = Cl, Br, I) and (μ 3-η 2-C 2 tBu)Ru(μ 3-Hg)M (M = MoC 5H 5(CO) 3, Mn(CO) 5, Re(CO) 5, FeC 5H 5(CO) 2, RuC 5H 5(CO) 2, Co(CO) 4) and the phosphine derivative P(C 6H 5) 3(CO) 8(μ 3-η 2-C 2 tBu)Ru 3(μ 3-Hg)MoC 5H 5(CO) 3 are reported. The 199Hg chemical shifts vary over a relatively large range for the series (∼ 1500 ppm) with some of the mixed transition series showing the largest downfield shifts (relative to Hg(CH 3) 2) reported to date. The data are discussed in light of previously reported 199Hg shifts for related complexes and although there is no correlation between HgM bond lengths in this isostructural series some general correlations of the chemical shifts with the expected polarity of the HgM bond based on the reactivity of the complexes and the qualitative theory of 199Hg chemical shifts can be made. A very large variation in line width is also observed which correlates well with the expected efficiency of quadrupole relaxation mechanisms.