Novel behaviour and reactivity in 1,1′-bis(diphenylphosphino)ferrocene and 1,1′-bis(diphenylphosphino)cobaltocene cluster derivatives

• Published in: Journal of organometallic chemistry Vol. 563; no. 1; pp. 113 - 136
• Main Authors: Shephard, Douglas S, Johnson, Brian F.G, Harrison, Andrew, Parsons, Simon, Smidt, Sebastian P, Yellowlees, Lesley J, Reed, David
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 30-07-1998
• Subjects: 1,1′-Bis(diphenylphosphino)cobaltocene; 1,1′-Bis(diphenylphosphino)ferrocene; Ruthenium clusters; 1,1′-Bis(diphenylphosphino)ferrocene; Ruthenium clusters; 1,1′-Bis(diphenylphosphino)cobaltocene
• ISSN: 0022-328X; 1872-8561
• DOI: 10.1016/S0022-328X(98)00565-8

The clusters [Ru
6C(CO)
16{Fe(C
5H
4P(Ph)
2)
2}]
2 and [Ru
6C(CO)
15{
μ-Fe(C
5H
4P(Ph)
2)
2}]
3 have been synthesised from the reaction of the parent cluster [Ru
6C(CO)
17]
1 with 1,1′-bis(diphenylphosphino)ferrocene (dppf) in THF. The related compound [Ru
5C(CO)
13{
μ-Fe(C
5H
4P(Ph)
2)
2}]
4 is produced from
2 and
3 in more forcing conditions. Both clusters
3 and
4 have been structurally characterised by single crystal X-ray analysis. In
3 the dppf ligand is coordinated in the
vicinal form and the cluster core is a highly distorted octahedron. In
4 the
vicinal mode is retained but the dppf ligand is coordinated to adjacent basal atoms of a square-base pyramid. The
31P-NMR spectra of
3 and
4 in CD
2Cl
2 at various temperatures show a high degree of stereochemically non-rigid behaviour. Magnetic susceptibility measurements across a range of temperatures indicate that
3 is paramagnetic at all temperatures. An electrochemical study of
1,
3,
4 and the related [Ru
6C(CO)
15{
μ-dppm}]
5 has demonstrated a significant degree of communication between the redox-active sites in
3 and
4. The cluster [Ru
5C(CO)
13{
μ-Co(C
5H
4P(Ph)
2)
2}]
7 has also been synthesised from the direct reaction of the parent cluster [Ru
5C(CO)
15]
6 with 1,1′-bis(diphenylphosphino)cobaltocene (dppc). Synthesis of the dppc analogue of
3 was attempted but was thwarted by unfavourable redox chemistry. EPR spectra have been obtained for both dppc and
7. The oxidation product of
7 has also been produced (
7
+) and displays a high degree of stereochemically non-rigid behaviour in a fashion similar to
3 and
4. The magnetic suceptibility of
7 has also been measured, showing an extraordinarily large magnetic moment at ambient temperature.