“…These features distinguish 2b from all the other known phosphine-monosubstituted RuCo 3 clusters, where Co is always the preferred coordination site, with the exception of RuCo 3 (CO) 11 (PMe 2 Ph)(μ 3 -AuPPh 3 ), in which the phosphine ligand PMe 2 Ph was established by X-ray diffraction to be bound to Ru . In this case, however, steric effects might be at work.…”
We have studied the metallosite selectivity of substitution reactions at heterometallic
tetranuclear clusters of the type HMCo3(CO)12 (M = Fe, Ru). Monosubstitution with PCyH2
occurs with a different metalloselectivity as a function of M. When M = Fe, substitution of
a Co-bound CO ligand occurs whereas when M = Ru, the phosphine ligand is bound to Ru.
Introduction of a second substituent (PCyH2 or NMe3) occurs in both cases at cobalt and, in
the case of HFeCo3(CO)11(PCyH2), at a cobalt that does not carry the PCyH2 substituent.
The clusters HMCo3(CO)11(PCyH2) (2a, M = Fe; 2b, M = Ru) transform in solution to give
the corresponding μ3-phosphinidene-capped heterotrinuclear clusters MCo2(μ3-PCy)(CO)9 (4a,
M = Fe; 4b, M = Ru). The μ4-phosphinidene-capped intermediate RuCo4(μ4-PCy)(μ-CO)2(CO)11 (5b) could be fully characterized, whereas the analogous species could not be isolated
when M = Fe. The transformation of 2a,b was accelerated by addition of Me3NO. This work
demonstrates that a reaction which represents a partial cluster fragmentation, with a
nuclearity change from 4 to 3, may occur via the intermediacy of a larger cluster, of nuclearity
5. Reactions and products were studied by IR and 1H, 31P{1H}, and 59Co NMR spectroscopic
methods, and the clusters 4b and 5b have been characterized by X-ray diffraction.
“…These features distinguish 2b from all the other known phosphine-monosubstituted RuCo 3 clusters, where Co is always the preferred coordination site, with the exception of RuCo 3 (CO) 11 (PMe 2 Ph)(μ 3 -AuPPh 3 ), in which the phosphine ligand PMe 2 Ph was established by X-ray diffraction to be bound to Ru . In this case, however, steric effects might be at work.…”
We have studied the metallosite selectivity of substitution reactions at heterometallic
tetranuclear clusters of the type HMCo3(CO)12 (M = Fe, Ru). Monosubstitution with PCyH2
occurs with a different metalloselectivity as a function of M. When M = Fe, substitution of
a Co-bound CO ligand occurs whereas when M = Ru, the phosphine ligand is bound to Ru.
Introduction of a second substituent (PCyH2 or NMe3) occurs in both cases at cobalt and, in
the case of HFeCo3(CO)11(PCyH2), at a cobalt that does not carry the PCyH2 substituent.
The clusters HMCo3(CO)11(PCyH2) (2a, M = Fe; 2b, M = Ru) transform in solution to give
the corresponding μ3-phosphinidene-capped heterotrinuclear clusters MCo2(μ3-PCy)(CO)9 (4a,
M = Fe; 4b, M = Ru). The μ4-phosphinidene-capped intermediate RuCo4(μ4-PCy)(μ-CO)2(CO)11 (5b) could be fully characterized, whereas the analogous species could not be isolated
when M = Fe. The transformation of 2a,b was accelerated by addition of Me3NO. This work
demonstrates that a reaction which represents a partial cluster fragmentation, with a
nuclearity change from 4 to 3, may occur via the intermediacy of a larger cluster, of nuclearity
5. Reactions and products were studied by IR and 1H, 31P{1H}, and 59Co NMR spectroscopic
methods, and the clusters 4b and 5b have been characterized by X-ray diffraction.
“…To separate the product by TLC, the original reaction mixture was first treated with [AuCl(PPh 3 )] and TlPF 6 . This transforms the anionic products into neutral ones by substituting NEt 4 + with the Au(PPh 3 ) + fragment; this fragment (isolobal with H + ) generally coordinates in a μ 3 mode to the cobalt triangle to give a triangular bipyramidal AuCo 3 Ru core (Scheme ). , 6 …”
The reactivity of [HMCo3(CO)12] and [Et4N][MCo3(CO)12] (M = Fe, Ru) toward phosphine selenides such as Ph3PSe, Ph2P(Se)CH2PPh2, Ph2(2-C5H4N)PSe, Ph2(2-C4H3S)PSe, and Ph2[(2-C5H4N)(2-C4H2S)]PSe has been studied with the aim to obtain new selenido-carbonyl bimetallic clusters. The reactions of the hydrido clusters give two main classes of products: (i) triangular clusters with a mu3-Se capping ligand of the type [MCo2(mu3-Se)(CO)(9-x)L(y)] resulting from the selenium transfer (x = y = 1, 2, with L = monodentate ligand; x = 2, 4, and y = 1, 2, with L = bidentate ligand) (M = Fe, Ru) and (ii) tetranuclear clusters of the type [HMCo3(CO)12xL(y)] obtained by simple substitution of axial, Co-bound carbonyl groups by the deselenized phosphine ligand. The crystal structures of [HRuCo3(CO)7(mu-CO)3(mu-dppy)] (1), [MCo2(mu3-Se)(CO)7(mu-dppy)] (M = Fe (16) or Ru (2)), and [RuCo2(mu3-Se)(CO)7(mu-dppm)] (12) are reported [dppy = Ph2(2-C5H4N)P, dppm = Ph2PCH2PPh2]. Clusters 2, 12, and 16 are the first examples of trinuclear bimetallic selenido clusters substituted by phosphines. Their core consists of metal triangles capped by a mu3-selenium atom with the bidentate ligand bridging two metals in equatorial positions. The core of cluster 1 consists of a RuCo3 tetrahedron, each Co-Co bond being bridged by a carbonyl group and one further bridged by a dppy ligand. The coordination of dppy in a pseudoaxial position causes the migration of the hydride ligand to the Ru(mu-H)Co edge. In contrast to the reactions of the hydrido clusters, those with the anionic clusters [MCo3(CO)12]- do not lead to Se transfer from phosphorus to the cluster but only to CO substitution by the deselenized phosphine.
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