Earl L. Muetterties

Arene transition metal chemistry : III. Arene exchange phenomena

Abstract Arene exchange between free arene and an arene—transition metal complex is reviewed with respect to structure, thermodynamics, kinetics and reaction mechanism. Catalysis of such arene exchange is also examined. Experimental results are presented for arene exchange between arene and the arene—metal complexes: η 6 -arene-1,5-cyclooctadieneruthenium, the cationic η 6 -arene-1,5-cyclooctadieneiridium and η 6 -arenetricarbonylmolybdenum. Mechanistic features of these exchange reactions are discussed.

Metal carbide clusters synthesis systematics for heteronuclear species

Abstract The strategies in the synthesis of metal carbide cluster are examined and the full synthesis procedures for a number of heteronuclear metal carbide clusters are presented. Specific classes of carbide clusters prepared are octahedral Fe 5 MC(CO) x y- and Fe 4 M 2 C(CO) x y- clusters and square pyramidal Fe 4 MC(CO) x y- clusters. One synthesis strategy was polyhedral expansion based on [Fe 4 C(CO) 12 2- ] or [Fe 5 C(CO) 14 2- ] reactions with coordinately unsaturated metal complexes or labile complexes that readily yield coordinately unsaturated complexes. Selected oxidative degradations of these octahedral carbide clusters provided a synthesis step comprising elision of an iron center to yield square pyramidal Fe 4 MC(CO) x y- clusters.

Molecular Metal Clusters as Catalysts

Abstract In earlier analyses [1–8] we have established a correlation between metal clusters and metal surfaces with chemisorbed molecules in the specific contexts of (1) the metal frameworks wherein the metal cluster core structures are fragments of cubic and hexagonal close packed or body centered cubic metal bulk structures; (2) ligand stereochemistry where the geometric features of ligands bound to clusters and to metal surfaces are similar; (3) thermodynamic features where the average bond energies for ligand-metal and metal-metal bonds are comparable, for a specific metal, in the metal cluster and the metal surface regime; and (4) mobility of ligands bonded to metal cluster frameworks and to metal surfaces. Nevertheless, there are sharp distinctions between surfaces and clusters. The average coordination numbers for metal-metal interactions and for metal-ligand interactions are distinctly different for clusters and for surfaces: generally, the former are larger for surfaces and the latter are larger ...

Arene C-H bond activation: reaction of (Me3P)3Rh(Me) with toluene to give (Me3P)3Rh(Ar) where Ar is o-, m- and p-tolyl

Abstract The square-planar rhodium (I) compound, (Me 3 P) 3 Rh(Me), reacts with benzene or toluene at 70° to give (Me 3 P) 3 Rh(Ph) or (Me 3 P) 3 Rh(Ar) where Ar is o -, m -, p -tolyl along with methane. These aryl compounds were prepared independently and characterized by 1 H, 13 C{ 1 H}, and 31 P{ 1 H} NMR spectroscopy. The benzyl compound, prepared from PhCH 2 Li and (Me 3 P) 3 RhCl, is formulated as an η 3 -benzyl, is not formed in detectable amounts in the arene activation studies. The benzyl compound rearranges on heating to (Me 3 P) 3 Rh( o -tolyl) in near quantitative yield at 70°C. The four-coordinate compound, (Me 3 P) 3 Rh(Me), is fluxional at +20° though the fluxional process is stopped at −20°C. The five-coordinate compound, (Me 3 P) 4 Rh(Me), also is fluxional at +20°C though stereochemical rigid at −65°C. The geometry of the latter compound is based upon a trigonal bipyramid with the methyl group on the axial site.

Bridging alkyls in d-transition metal chemistry: Reactions of (cod) 2M2(μ-R)2 with organolithium reagents to give (cod)2M2(R)4Li2, where M is Rh or Ir, and the crystal structure of (cod)2Rh2(CH2SiMe3)4Li2 and (cod) Rh( CH2SiMe3)2Li(Me2NCH2CH2NMe2)

Abstract The bridging alkyls, (cod) 2 Rh 2 (μ-R) 2 where R is Me or Me 3 SiCH 2 , react with one molar equivalent of RLi to generate the thermally stable dialkylrhodates, (cod)Rh(R) 2 Li, which may be crystallized from hydrocarbons. X-Ray crystallography of the compound with R = CH 2 SiMe 3 shows that the complex is a centrosymmetric dimer with space group C 2/ c , a 24.370(6), b 9.946(2), c 17.791(5) A, γ 106.62(2)°, and V 4132(2) A 3 . The dimer is cleaved by reaction with the Lewis base, Me 2 NCH 2 CH 2 NMe 2 , to give (cod)Rh(CH 2 SiMe 3 )2Li(tmed) as shown by X-ray crystallography. The space group is Pbca , a 16.532(5), b 19.239(5), c 18.141(4), and V 5770(3) A 3 . The coordination geometry about the square planar Rh I atom is similar in both compounds; Rh I is bonded to cod and two CH 2 SiMe 3 groups and the lithium atom is oriented ca. 30° off a normal to the rhodium atom towards the CH 2 SiMe 3 groups with a Li … Rh distance of ca. 2.6 A. Solution NMR spectroscopy as a function of temperature and solvent on these and the related iridates, (cod)Ir(CH 2 SiMe 3 ) 2 Li(tmed) and (cod)Ir(R) 2 Li where R is Me or CH 2 SiMe 3 , are interpreted relative to the solid state structures.

Bridging alkyls in d-transition metal chemistry: reaction of (cod)2 RH2 (μ-R)2 with Lewis bases to give (cod)Rh(R)(L) and their reaction with aromatic hydrocarbons

Abstract Low temperature (−70°C) reaction of (cod) 2 Rh 2 2 (μ-Cl) 2 with two molar equivalents of RLi in diethyl ether gives (cod) 2 Rh 2 (μ-R) 2 where R = Me, Me 3 SiCH 2 . Even though the bridging alkyls are air and moisture sensitive, they may be stored for prolonged periods at −30°C. The bridging alkyls are fluxional at + 20°C and the NMR spectra are consistent with a dimer of idealized D 2 h symmetry. Low temperature NMR spectroscopic studies suggest that the dimers have idealized C 2 v symmetry as found by X-ray studies described earlier. The bridging alkyls readily react with Lewis bases to give monomeric (cod)Rh(R)(L) where R = Me and L = PMe 3 , PEt 3 , P(NMe 2 ) 3 , P(OMe) 3 , py and R = Me 3 SiCH 2 , L = P(OMe) 3 . The five coordinate, fluxional complex, (cod)RhMe(PMe 3 ) 2 also may be isolated. The four coordinate (cod)RhMe(PEt 3 ), slowly reacts with toluene to give (cod)Rh( m -tolyl)(PEt 3 ), (cod)Rh( p -tolyl)(PEt 3 ), and methane and (cod)RhMe(PMe 3 ) slowly reacts with benzene to give (cod)Rh(Ph)(PMe 3 ) and methane.

The preparation and X-ray crystal structure of W3(μCN)3(NO)3(CO)9

Abstract The nitrosation of Na[W(CO)5CN] using amyl nitrite and sulphuric acid in a two phase water— diethyl ether system gives the trinuclear compound W3(μCN)3(NO)3(CO)9. A single crystal X-ray diffraction study showed that the compound contains a nine-membered ring of three tungsten atoms and three bridging cyanide groups. The terminal carbonyl and nitrosyl ligands were not distinguishable.