Derivatives of [Rh6(CO)13C]2–: solution structure of [Rh6H(CO)13C]– from nuclear magnetic resonance measurements and the X-ray crystal structure of [Rh6(CO)11C(µ-Ph2PCH2CH2PPh2)]2–

Abstract

Multielement n.m.r. measurements (¹H, ¹H-{¹⁰³Rh}, ¹³C, ¹³C-{¹⁰³Rh}, and ¹⁰³Rh) show that protonation of [Rh₆(CO)₁₃C]^2– at low temperature gives [Rh₆H(CO)₁₃C]^– which contains an edge-bridging hydride with the carbonyl distribution being very similar to that found in [Rh₆(CO)₁₃C]^2– Warming this solution to < –20 °C results in complete CO- and H-migration over the Rh₆ octahedron and at –20 °C there is formation of [Rh₆H(CO)₁₅C]^– together with loss of hydrogen to give [Rh₁₂(CO)₂₄(C)₂]^2– which has been spectroscopically characterised. Multielement n.m.r. studies on products resulting from the reaction of [Rh₆(CO)₁₃C]^2–(1 mol equiv.) with diphosphines Ph₂P(CH₂)_nPPh₂[0.5 mol equiv.; n= 1,2 (dppe), 3, or 4] or Ph₂AsCH₂CH₂AsPh₂ suggest that they all have similar structures and an X-ray crystallographic analysis of the dppe derivative shows it to be [Rh₆(CO)₁₁C(µ-dppe)]^2–.