Synthesis and structural studies of some new rhenium phosphine heptahydride complexes. Evidence for classical structures in solution

Article abstract of DOI:10.1021/ja00168a028

A series of new rhenium phosphine heptahydride complexes ReH₇L₂ (L₂ = a chelating bidentate phosphine) have been synthesized and characterized by IR and ¹H, ³¹P, and ¹³C NMR spectroscopy. The hydride resonances of ReH₇(dppf) (1,dppf = 1,1'-bis(diphenylphosphino)ferrocene), ReH₇dppb) (2, dppb = 1,4-bis(diphenylphosphino)butane),and ReH₇(+)-diop| (3, (+)-diop = (4S,5S)-4,5-bis((diphenylphosphino)methyl)-2,2-dimethyl-1,3-dioxolane) undergo decoalescence upon cooling. The low-temperature hydride patterns suggest classical 9-coordinate tricapped trigonal prismatic structures. Consistent with the classical structures, ¹H NMR spectra of deuterated ReH₇L₂ complexes show very small and temperature-independent upfield isotope shifts in the hydride region and no change in VHP- Sequential treatment of 1, 2, and 3 with NaH and Mc₂SO₄ in the presence of Ph₃SiH leads to ReH₆(SiPh₃)L₂ (L₂ = dppf, dppb, (+)-diop). Variable-temperature ¹H NMR studies of these silyl derivatives provide further support for the classical formulation of their parent heptahydrides. Theoretical 7, (min) values are calculated for some polyhydrides on the basis of different structural models and are compared with the experimental numbers. Precautions to be taken in interpreting T₁ data are discussed.