Jerome B. Keister

Protonation of (μ-H)3Ru3(μ3-CR)(CO)9. Evidence for the formation of an agostic metalhydrogencarbon bond

Abstract Protonation of (μ-H)3M3(μ3-CR)(CO)9 (M = Ru, R = Et or M = Os, R = Me) by dissolution in HSO3CF3 yields H3M3(HCR)(CO)9+, containing a Mue5f8Hue5f8C bridge. The products were characterized by 1H and 13C NMR spectroscopy. Decompositions of other protonated methylidyne clusters from CH3R and a variety of metal-containing products.

Ligand additivity in 47-electron clusters. Electrochemistry of (μ-H)Ru3(μ3-η3-XCCRCR′)(CO)9−n(PPh3)n and reactions with electrophiles: one-electron oxidation and adduct formation

Abstract Reactions of clusters HRu 3 ( μ 3 - η 3 -XCCRCR′)(CO) 9− n (PPh 3 ) n (X=OMe, R=R′=Me, n =1, 2, 3; X=MeO, R=H, R′=EtO, n =2, 3; X=Et 2 N, R=H, R′=Me, n =1, 2) with electrophilic reagents proceed either by 1-electron transfer or by Lewis acid-base adduct formation. The HOMO for the cluster series is Ru–Ru bonding with contributions from all three Ru atoms. Cyclic voltammograms of HRu 3 ( μ 3 - η 3 -XCCRCR′)(CO) 9− n (PPh 3 ) n ( n =2, 3) display in each case an electrochemically reversible to quasi-reversible, 1-electron oxidation, followed by an irreversible, 1-electron oxidation at a significantly more positive potential. The potential for the first oxidation is lowered both by an increasing degree of PPh 3 substitution and an increasing pi donor capability of the allylidene substituents. The dependence of the oxidation potential upon substitution of the metal and carbon framework atoms is analyzed as an example of ligand additivity in cluster systems. Radical cations derived from the di- and tri-substituted 1,3-dimetalloallyl clusters can be generated by oxidation with tris(4-bromophenyl)aminium hexachloroantimonate. These radical cations decompose within a few minutes at room temperature but are stable for long periods at temperatures below −40°C. Electrophilic addition of E=H 1+ , Ag 1+ or Au(PPh 3 ) 1+ to the Ru–Ru bonds is observed. Adducts [ERu 3 H( μ 3 - η 3 -XCCRCR′)(CO) 9− n (PPh 3 ) n ] 1+ have been characterized by IR and 1 H- and 31 P-NMR spectroscopies. The Au(PPh 3 ) moiety is found to bridge two or three Ru–Ru bonds in these adducts. Substitutional isomerism is induced by electrophilic addition.

Structural studies on ruthenium carbonyl hydrides. X: Crystal structure of (μ-H)Ru3(CO)10(μ-SEt)

The complex (μ-H)Ru3(CO)10(μ-SEt) crystallizes in the centrosymmetric orthorhombic space group Pbca (No. 61) with a 17.361(2), b 12.804(4), c 17.484(3) A, V 3886.5(14) A3 and Z = 8. Diffraction data (Mo-Kα, 2θ = 4.0-45.0°) were collected with a Syntex P21 automated diffractometer and the structure was solved and refined to R 5.9% for 1800 reflections with |Fo| > 3σ(| Fo|) (R4.1% for those 1413 reflections with |F0| > 6σ(|F0|)). The complex contains a triangular cluster of ruthenium atoms in which Ru(2) and Ru(3) are each linked to three terminal carbonyl ligands while Ru(1) is linked to four. Additionally Ru(2) and Ru(3) are bridged by a SEt ligand [Ru(2)ue5f8S 2.389(4), Ru(3)ue5f8S 2.391(4) A and Ru(2)ue5f8Sue5f8Ru(3) 73.0(1)°] and a hydride ligand. The di-bridged Ruue5f8Ru linkage (Ru(2)ue5f8Ru(3) 2.843(1) A is slightly longer than the non-bridged bonds (Ru(1)-Ru(2) 2.831(2) and Ru(1)ue5f8Ru(3) 2.825(1) A).

KINETICS AND MECHANISM FOR INTRAMOLECULAR ISOMERIZATION OF HRu3 (μ3-η3-EtSCCMeCMe)(CO)9 TO Ru3(μ-SEt) (μ3-η3-CCMeCHMe)(CO)9

Abstract The kinetics for isomerization of HRu3 (μ3-η3-EtSCCMeCMe)(CO)9 TO Ru3(μ-SEt) (μ3-η3-CCMeCHMe)(CO)9, were determined. The overall process involves C[sbnd]H elimination, C[sbnd]S and Ru[sbnd]Ru bond cleavage and Ru2(μ-S) bond formation. Activation parameters were determined from the temperature dependence (ΔH‡ = 127(3) kJ/mol, ΔS‡= 56(11) J/mol-K) and from the pressure dependence (0[sbnd]207 MPa, ΔV‡ 0 +12.7(1.1) cm3/mol, Δβ‡ = +0.037(0.012) cm3/(mol-MPa)) of the rate constant. The data are consistent with an intramolecular reaction involving significant metal-metal or carbon-sulfur bond cleavage in the transition state. The activation volume is too large to be accommodated by C[sbnd]H elimination alone and CO dissociation is not involved.

Structural studies on ruthenium carbonyl hydrides: XIV. Synthesis, characterization, and crystal structure of (μ-H)2Ru3(η3-η2-CHC(O)OCH3)(CO)8(PPh3). An example of cis-labilization by an oxygen donor ligand☆

Abstract The reaction of PPh 3 with (μ-H( 2 Ru 3 (μ 3 -η 2 -CHC(O)OCH 3 )(CO) 9 displaces a CO ligand, rather than the coordinated oxygen atom of the acyl moiety, thereby generating (μ-H) 2 Ru 3 (μ 3 -η 2 -CHC(O)OCH 3 )(CO) 8 (PPh 3 ). A single-crystal X-ray study of (μ-H) 2 Ru 3 (η 3 -η 2 -CHC(O)OCH 3 )(CO) 8 (PPh 3 ) has been performed. This complex crystallizes in the triclinic space group P 1 with a 9.360(1), b 11.442(1), c 15.192(1) A, α 84.554(7), β 78.729(8), γ 83.023(3)°, V 1579.6(3) A 3 and Z = 2. Data for 2θ 5.0–50.0° (Mo- K α ) were collected on a Syntex P2 1 automated four-circle diffractometer and the structure was refined to R F 4.6% for all 5601 reflections ( R F 3.4% for those 4962 reflections with | F ° | > 3σ(| F °| ). The crystal structure establishes that PPh 3 substitution occurs cis to the coordinated oxygen in that equatorial site which is trans to the non-hydrido-bridged Ruue5f8Ru bond. The high rate of CO displacement from (μ-H) 2 Ru 3 (μ 3 -η 2 -CHC(O)OCH 3 )(CO) 9 , as compared with that for (μ-H) 3 Ru 3 (μ 3 -CC(O)OCH 3 )(CO 9 , is attributed to cis labilization by the oxygen donor atom.

LIGAND SUBSTITUTION ON HRu3(μ-NC5H3CO2Me)(CO)10 AND H2Ru3(μ-NC5H3CO2Me)2(CO)8. CRYSTAL STRUCTURES OF (μ-H)Ru3(μ-η2-NC5H3CO2Me)(CO)9(PPh3)AND (μ-H)2Ru3(μ-η2-NC5H3CO2Me)2(CO)7(PPh3)∗

Abstract Clusters of the series HRu3(μ-NC5H3CO2Me)(CO)10-n (PPh3) n (n = 0, 1) and H2Ru3(μ-NC5H3CO2Me)2(CO)8-n (PPh3) n (n = 0, 1) have been prepared. X-ray crystallographic studies of HRu3(μ-NC5H3-5-CO2Me)(CO)9(PPh3) and H2Ru3(μ-NC5H3-5-CO2Me)2(CO)7(PPh3) have been performed. The regiochemistry of PPh3 substitution in both is consistent with greater cis labilization by the N-donor atom compared with the C-donor atom of the nicotinyl ligand. The monohydrido-methyl nicotinate derivative. (μ-H)Ru3(μ-η2-NC5H3CO2Me)(CO)9(PPh3), crystallizes in the orthorhombic space group Pbca (No. 61) with a = 22.891(3), b = 12.641(1), c = 24.694(3)A, V = 7145.6(14)A3 and Z = 8. The structure was solved and refined to R = 2.60% for 2191 data with |F 0| ue421 6[sgrave](F 0). The Ru3 triangle has interatomic distances (in increasing order) of Ru(l)-Ru(3) = 2.854(l). Ru(2)-Ru(3) = 2.861(l) and Ru(l)-Ru(2) = 2.910(1)A. The nicotinate ligand bridges the cluster through axial sites on Ru(l) and Ru(2), with Ru(l)-N(l) = 2.136(6) A and ...

ELECTROPHILIC ADDITION TO [Rh17S2(CO)32]3−

Abstract Reactions of electrophiles with [Rh17S2(CO)32]3− produce the adducts [Rh17S2(CO)32E]2−, E = Au(PPh3), Au(PPh2Me), Ag, Rh(COD), Pt(COD)Cl, and Pd(COD)Cl, characterized by spectroscopic methods. The 13C NMR spectrum of [Rh17S2(CO)32Au(PPh3)]2− suggests that addition of the electrophile occurs at a Rh-Rh edge between the basal and internal Rh4 planes. Cyclic voltammograms for [Rh17S2(CO)32]3− and [Rh17S2(CO)32AuL]2− show several irreversible oxidation processes but two 1-electron reductions, the first of which is nearly reversible.