Structure and dynamical properties of Rh4(CO)12 in solution: 13C nuclear magnetic resonance study

Abstract

Rh,(CO),, has been shown by I3C n.m.r. to have i.r. spectrum2 of Rh,(CO),, when compared urith that of the same structure in solution as in the crystal, and the CO,(CO),, strongly suggests that the C,, structure persists changes in line shape as a function of temperature are in solution, conclusive evidence has been lacking. A consistent with a CO scrambling mechanism which has the carbon-13 n.m.r. study from about 0" to + 60" showed that fully symmetric (Td) structure as an intermediate. rapid intramolecular equilibration of the carbonyl groups O C C U~S ,~ as previously p~s t u l a t e d ,~ but fell short of affording either structure proof or direct evidence for the mechanism of the scrambling of CO groups. We now report a low THE structure of Rh,(CO),, in the crystal has been demonstrated to possess idealised C,, symmetry (1).1 While the

Metal Clusters in Catalysis III. — Clusters as Models for Chemisorption Processes and Heterogeneous Catalysis

“…64 The high temperature quintet signifies that on the nmr time scale all carbonyl groups have become equivalent and are equally spin coupled with all four rhodium atoms.…”

Spectral resolution of fluxional organometallics. The observation and FTIR characterization of all-terminal [Rh4(CO)12]

“…In particular, their structures and fluxional behavior in solution have generated considerable discussion. [1][2][3][4][5][6][7] Three primary all-terminal geometries [M 4 (CO) 12 ] obeying the 18erule for closed polyhedra have been discussed, namely the (1) T d symmetric cubeoctahedral, (2) the T symmetric icosahedron and (3) the C 3v anticubeoctahedron. 5,8,9, 10 In addition two bridged species have been discussed, (4) the C 3v symmetric icosahedral [M 4 (CO) 9 (l-CO) 3 ] and (5) the D 2d symmetric [M 4 (CO) 8 (l-CO) 4 ].…”

Intracluster ligand mobility. 4. Solution structures and dynamics of Ir4(CO)12-x(PPh2Me)x (x = 1-4)

“…These signals shift ~10 ppm further downfield for each substitution at an adjacent iridium atom. (ii) Signals for terminal carbonyls positioned approximately in the basal plane (radial positions d, d', f) are [7][8][9][10][11][12][13][14][15] ?3-f in 6), and 3/pc = 14-15 Hz, when both ligands are in basal-radial positions (e.g., P2/P2z-f in 5). However, the coupling is weaker for ligands attached to the same iridium atom, 2/pc 5 9 Hz.…”