TY - JOUR
T1 - High nuclearity ruthenium carbonyl cluster chemistry. 5. Local density functional, electronic spectroscopy, magnetic susceptibility, and electron paramagnetic resonance studies on (carbido)decaruthenium carbonyl clusters
AU - Cifuentes, Marie P.
AU - Humphrey, Mark G.
AU - McGrady, John E.
AU - Smith, Paul J.
AU - Stranger, Robert
AU - Murray, Keith S.
AU - Moubaraki, Boujemaa
PY - 1997/3/19
Y1 - 1997/3/19
N2 - Electronic spectra of 'giant tetrahedral' decaruthenium cluster anions are consistent with a HOMO-LUMO gap of ≤ 1.2 eV, with intense transitions assigned to M-M* → CO 2π* at high energy and weak transitions assigned to M-CO π → M-CO σ* at low energy; the former are relatively insensitive to increasing phosphine substitution or cluster core charge, whereas the latter show some ligand dependence. The first diffuse reflectance UV-vis-NIR spectra of metal carbonyl clusters have been obtained; spectra of [Ru2(μ-H)(μ-NC5H4)2(CO)4(NC5H5)2][Ru10(μ-H)(μ6-C)(CO)2 3(PPh3)] and [ppn]2[Ru10(μ6-C)(CO)24] contain broad absorptions extending to a λ(onset) of 1300 nm with absorption maxima corresponding to those of the solution spectra superimposed. Local density functional (LDF) calculations support the optical spectra assignments and predict a triply degenerate HOMO approximately 1.3 eV below the LUMO. Magnetic susceptibility data for [Ru2(μ-H)(ν-NC5H4)2(CO)4(NC5H5)2][Ru10(μ-H)(μ6-C)(CO)2 3(PPh3)] show a temperature independent susceptibility χ(m) of + 1384 + 10 x 10-6 cm3 mol-1 (diamagnetic correction including decaruthenium valence electrons), arising from Van Vleck paramagnetism; unlike related decaosmium clusters and lower nuclearity ruthenium clusters, no temperature dependent component of the susceptibility exists. Electron paramagnetic resonance (EPR) investigations on three decaruthenium cluster anions reveal a temperature-independent paramagnetic (TIP) signal which does not derive from solid-state packing effects, the nature of the cation, the presence of impurities such as colloids, particles, or oxides, or incipient metallic character ('mesometallic' behavior); this EPR signal, the first reported TIP resonance from a carbonyl cluster, is assigned to the presence of radical decaruthenium clusters due to oxidation of the cluster anions. Unlike high-nuclearity clusters examined previously by EPR, no temperature-dependent response was found for [Ru2(μ-H)(μ-NC5H4)2(CO)4(NC5H5)2][Ru10(μ-H)(μ6-C)(CO)2 4]. The electronic spectroscopy, magnetic susceptibility data, EPR studies, and LDF calculations are consistent with these high-nuclearity carbonyl clusters having 'molecular' rather than 'mesometallic' character.
AB - Electronic spectra of 'giant tetrahedral' decaruthenium cluster anions are consistent with a HOMO-LUMO gap of ≤ 1.2 eV, with intense transitions assigned to M-M* → CO 2π* at high energy and weak transitions assigned to M-CO π → M-CO σ* at low energy; the former are relatively insensitive to increasing phosphine substitution or cluster core charge, whereas the latter show some ligand dependence. The first diffuse reflectance UV-vis-NIR spectra of metal carbonyl clusters have been obtained; spectra of [Ru2(μ-H)(μ-NC5H4)2(CO)4(NC5H5)2][Ru10(μ-H)(μ6-C)(CO)2 3(PPh3)] and [ppn]2[Ru10(μ6-C)(CO)24] contain broad absorptions extending to a λ(onset) of 1300 nm with absorption maxima corresponding to those of the solution spectra superimposed. Local density functional (LDF) calculations support the optical spectra assignments and predict a triply degenerate HOMO approximately 1.3 eV below the LUMO. Magnetic susceptibility data for [Ru2(μ-H)(ν-NC5H4)2(CO)4(NC5H5)2][Ru10(μ-H)(μ6-C)(CO)2 3(PPh3)] show a temperature independent susceptibility χ(m) of + 1384 + 10 x 10-6 cm3 mol-1 (diamagnetic correction including decaruthenium valence electrons), arising from Van Vleck paramagnetism; unlike related decaosmium clusters and lower nuclearity ruthenium clusters, no temperature dependent component of the susceptibility exists. Electron paramagnetic resonance (EPR) investigations on three decaruthenium cluster anions reveal a temperature-independent paramagnetic (TIP) signal which does not derive from solid-state packing effects, the nature of the cation, the presence of impurities such as colloids, particles, or oxides, or incipient metallic character ('mesometallic' behavior); this EPR signal, the first reported TIP resonance from a carbonyl cluster, is assigned to the presence of radical decaruthenium clusters due to oxidation of the cluster anions. Unlike high-nuclearity clusters examined previously by EPR, no temperature-dependent response was found for [Ru2(μ-H)(μ-NC5H4)2(CO)4(NC5H5)2][Ru10(μ-H)(μ6-C)(CO)2 4]. The electronic spectroscopy, magnetic susceptibility data, EPR studies, and LDF calculations are consistent with these high-nuclearity carbonyl clusters having 'molecular' rather than 'mesometallic' character.
UR - http://www.scopus.com/inward/record.url?scp=0030888673&partnerID=8YFLogxK
U2 - 10.1021/ja9602197
DO - 10.1021/ja9602197
M3 - Article
AN - SCOPUS:0030888673
SN - 0002-7863
VL - 119
SP - 2647
EP - 2655
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 11
ER -