The heteronuclear cluster chemistry of the group 1B metals. Part 9. Stereochemical non-rigidity of the metal skeletons of cluster compounds in solution. 109Ag-{1H} INEPT nuclear magnetic resonance studies on [Ag2Ru4(µ3-H)2{µ-Ph2P(CH2)nPPh2}(CO)12](n= 1, 2, or 4) and X-ray crystal structure of [Ag2Ru4(µ3-H)2(µ-Ph2PCH2PPh2)(CO)12]

Abstract

A combination of spectroscopic data and an X-ray diffraction study on [Ag₂Ru₄(µ₃-H)₂(µ-Ph₂PCH₂PPh₂)(CO)₁₂][Ag–Ag 2.756(6), Ag–Ru 2.820(6)–3.151(6), Ru–Ru 2.775(7)—2.998(6)Å] shows that the clusters [Ag₂Ru₄(µ₃-H)₂{µ-Ph₂P(CH₂)_nPPh₂}(CO)₁₂](n= 1–6) all adopt a capped trigonal-bipyramidal metal core geometry. However, although there are two distinct silver sites in the ground-state structures, ambient temperature ¹⁰⁹Ag-{¹H} INEPT n.m.r. spectra of the clusters in which n= 1, 2, or 4 show a single averaged silver resonance in each case. These studies provide the first direct evidence for stereochemical non-rigidity of the metal skeletons of Group 1B metal heteronuclear clusters in solution. In addition, values of ¹J(^107,109Ag^107,109Ag) have been measured for the first time. The results of ³¹P-{¹⁰⁹Ag} and ¹⁰⁹Ag INEPT and DEPT n.m.r. studies on [AgRu₄(µ₃-H)₃(CO)₁₂(PPh₃)] are also reported.