“…Since there are no experimental data with which to compare, one can only state that the bond lengths are reasonable; for example, the O−H bond in Rh and Pt is about 1 Å. For comparison, the OH bond length in trimethylplatinum(IV) hydroxide is 0.93 Å . The M−O bond length increases to 2.27 Å for Rh and 2.50 Å for Pt, compared to 2.20 Å in trimethylplatinum(IV) hydroxide.…”
The bonding of atomic oxygen on Pt(111) and Rh(111) was examined using density functional theory in order to understand their different chemical properties. The oxygen-surface interactions were modeled by bonding atomic oxygen to 10-atom clusters of Pt and Rh designed to model the (111) surface. Density functional theory was applied using the local density and generalized gradient approximations; results were obtained for both double-and triple-basis sets. Optimized geometries and binding energies were computed and favorably compared to available experimental values. Interestingly, the ionic bonding in the two cases is nearly the same, based on the similarities in the charge on oxygen. The Hirshfeld charges on oxygen were -0.225 and -0.207 for Rh 10 -O and Pt 10 -O , respectively, using the double-basis set. A more detailed analysis of the covalent bonding using crystal orbital overlap populations indicated that the 2p orbitals of oxygen interact in a greater bonding fashion with both the sp and d orbitals of Rh than with those of Pt. Additional calculations with adsorbed hydroxyl on these metal clusters show differences in covalent bonding similar to that of oxygen. In this case, however, differences in ionic bonding play a role; oxygen in hydroxyl has a greater charge on Pt than Rh. This leads to smaller differences in the interaction energies of hydroxyl on Rh and Pt compared with oxygen, resulting in differences in chemical reactivity between the two metals, especially with respect to reactions involving hydrogen transfer.
“…Since there are no experimental data with which to compare, one can only state that the bond lengths are reasonable; for example, the O−H bond in Rh and Pt is about 1 Å. For comparison, the OH bond length in trimethylplatinum(IV) hydroxide is 0.93 Å . The M−O bond length increases to 2.27 Å for Rh and 2.50 Å for Pt, compared to 2.20 Å in trimethylplatinum(IV) hydroxide.…”
The bonding of atomic oxygen on Pt(111) and Rh(111) was examined using density functional theory in order to understand their different chemical properties. The oxygen-surface interactions were modeled by bonding atomic oxygen to 10-atom clusters of Pt and Rh designed to model the (111) surface. Density functional theory was applied using the local density and generalized gradient approximations; results were obtained for both double-and triple-basis sets. Optimized geometries and binding energies were computed and favorably compared to available experimental values. Interestingly, the ionic bonding in the two cases is nearly the same, based on the similarities in the charge on oxygen. The Hirshfeld charges on oxygen were -0.225 and -0.207 for Rh 10 -O and Pt 10 -O , respectively, using the double-basis set. A more detailed analysis of the covalent bonding using crystal orbital overlap populations indicated that the 2p orbitals of oxygen interact in a greater bonding fashion with both the sp and d orbitals of Rh than with those of Pt. Additional calculations with adsorbed hydroxyl on these metal clusters show differences in covalent bonding similar to that of oxygen. In this case, however, differences in ionic bonding play a role; oxygen in hydroxyl has a greater charge on Pt than Rh. This leads to smaller differences in the interaction energies of hydroxyl on Rh and Pt compared with oxygen, resulting in differences in chemical reactivity between the two metals, especially with respect to reactions involving hydrogen transfer.
“…On the basis of all this spectroscopic evidence, a possible structure can be proposed for this new carbonyl species based on “Os(CO) 3 (μ-OSiEt 3 ) 2 (OSiEt 3 )(H)Os(CO) 2 ” units such as These units may aggregate via OSiEt 3 bridges, in agreement with the 18-electron rule. The evidence of a dimer, given by the ESI+ mass spectrum, would suggest a cubane structure similar to that of the Os(II) complex [(CO) 3 OsO] 4 and common to many complexes with a metal having a low-spin d 6 configuration such as Pt(IV) ([Me 3 PtCl] 4 , [Me 3 PtOH] 4 ), Mn(I) ([(CO) 3 MnSR] 4 ), and Re(I) ([(CO) 3 ReSR] 4 , [(CO) 3 ReOH] 4 ). …”
The reactivity (e.g., toward hydrolysis, alcoholysis, reduction by CO or H2) of various [Os3(CO)10(μ-H)(μ-OSiPh2R‘)] (R‘ = Ph, OH, OSiPh2OH) clusters and the thermal behavior of
[Os3(CO)10(μ-H)(μ-OSiEt3)] have been studied with the aim of clarifying by a molecular
approach some aspects of the surface chemistry of silica-anchored [Os3(CO)10(μ-H)(μ-OSi⋮)].
Their easy and selective reduction to [Os3(CO)12] (under CO) and to [H4Os4(CO)12] (under
H2) suggests that [Os3(CO)10(μ-H)(μ-OSi⋮)] does not require, as a reactive intermediate, a
previous hydrolysis to the more reactive molecular species [Os3(CO)10(μ-H)(μ-OH)] in order
to generate different osmium carbonyl clusters in their silica-mediated synthesis starting
from OsCl3 or [Os(CO)3Cl2]2. The thermal behavior of [Os3(CO)10(μ-H)(μ-OSiEt3)] dissolved
in triethylsilanol (to mimic a silica surface with many available surface silanols) or triglyme
(to mimic a highly dehydroxylated silica surface) gives an answer to the controversy on the
nature of the products formed by thermal degradation on the silica surface of [Os3(CO)10(μ-H)(μ-OSi⋮)]. In triethylsilanol, oxidation occurs to give a Os(II) hydrido carbonyl species
which, on the basis of chemical and spectroscopic evidence, we suggest to be [Os(CO)3(μ-OSiEt3)2(OSiEt3)(H)Os(CO)2]
n
(n = probably 2), whereas in triglyme an aggregation to high-nuclearity clusters such as [H4Os10(CO)24]2- and [H5Os10(CO)24]- occurs. Therefore, it is shown
for the first time that molecular models not only are a tool to define structural aspects but
also may be a springboard to understand and clarify by a molecular approach aspects of the
reactivity of organometallic species on the silica surface.
“…As part of their seminal studies of platinum alkyls, Pope and Peachy synthesized the compound later established as the first metallo hydroxy cubane, [PtMe 3 (OH)] 4 . − More recent examples of hydroxy cubane compounds have been characterized for the elements Cr, Mo, W, Mn, Re, − Ru, − Ni, Cu, and Cd . The corner-vacant trinuclear fragment [NEt 4 ][Re 3 (CO) 9 (OH) 4 ] ( Re 3 ) has been used as a tripodal ligand to form heterobimetallic complexes with a fused “double-cubane” structure .…”
The heterobimetallic hydroxy cubanes {Re(CO)3}4
-
n
{PtMe3}
n
(OH)4 (n = 1−3) have been synthesized and characterized by analytical and spectroscopic data. The structures of Re
3
Pt and RePt
3
have been determined by X-ray crystallography.
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