Brian T. Heaton

Stereochemical non-rigidity of a metal polyhedron; carbon-13 and platinum-195 fourier transform nuclear magnetic resonance spectra of [Ptn(CO)2n]2- (n = 3, 6, 9, 12 or 15)

Abstract Platinum-195 spectra are reported for [Ptn(CO)2n]2- (n = 3, 6, 9, 12 and 15) and carbon-13 spectra are reported for n = 6, 9 and 12 over a range of temperatures. The spectra provide evidence for (a) intramolecular rotation of the Pt3-triangles about the principal three-fold axis, (b) inter-exchange of Pt3-triangles, (c) lack of terminal/edge carbonyl exchange within the Pt3(CO)3(μ-CO)3 group. Evidence is also presented for the formation of [Ni3Pt3(CO)12]2- on mixing [Pt6(CO)12]2- [Ni6(CO)12]2-.

Structural studies of Rh4(CO)12 derivatives in solution and in the solid state

Abstract The crystal structures of Rh4(CO)10(PPh3)2 and Rh4(CO)9P(OPh)33 are reported. 31P-1H NMR studies on Rh4(CO)12-x {P(OPh)3}x(X ue5fb 1, 2 and 3) show that each derivative exists as only one isomer in solution whereas the analogous triphenylphosphine derivatives can exist as different isomers. A quantitative redistribution of triphenylphosphites occurs on mixing Rh4-(CO)12-xLx with Rh4(CO)12-yLy (L ue5fb P(OPh)3; x ue5fb 0, 1, 2, y ue5fb x + 2; x ue5fb 0, y ue5fb x + 4) to give Rh4(CO)12-zLz[z ue5fb 1 2 (x + y)]; a related rapid intermolecular randomisation of carbonyls occurs on mixing Rh4(12CO)12 with Rh4(13CO)12.

An NMR study of carbide clusters

Abstract 13C and13C-103Rh} data on [Rh6(CO)15C]2− and [Rh6(CO)13C]2− are reported and compared. [Rh6(CO)13C]2− undergoes a unique facile intramolecular CO migration around the equator of the Rh6 octahedron; at 25°C, [Rh6(CO)15C]2− undergoes preferential intermolecular CO exchange at sites which have the longest Rhue5f8CO bonds and direct exchange of terminal carbonyls is easier than edge-bridging carbonyls with approximately similar Rhue5f8CO bond lengths.

Fluxional behaviour of Rh4(CO)8{P(OPh)3}4: A 13C-{31P, 1H} NMR study

Abstract Variable temperature 13 C-{ 31 P, 1 H} NMR studies on Rh 4 (CO) 8 {P(OPh) 3 } 4 show that the solid state structure is maintained in solution at low temperature; at higher temperatures carbonyl migration occurs around the metal polyhedron with the lowest energy migration occurring via a Cotton type mechanism which also involves a rocking motion about the unique rhodium in the basal plane. At +82°C, the fast exchange limiting 13 C-{ 31 P, 1 H} and 31 P spectra exhibit a quintet and doublet of quartets, respectively.

Synthesis, NMR, and structural characterization of the [Ni9Pt3(CO)21H4-n]n− (n = 4, 3, 2) anionic clusters

Abstract The preparations of bimetallic carbonyl clusters having the general formula [Ni 9 Pt 3 (CO) 21 H - n ] n − ( n = 4, 3, 2) are described. X-ray studies on [NEt 4 ] 3 [Ni 9 Pt 3 (CO) 21 H] show that it is isostructural with [Ni 12 (CO) 21 H] 3− , with the platinum atoms occupying the inner triangle of the central Ni 3 Pt 3 planar triangulated array. The interstitial coordination of the hydride atoms in these compounds is inferred from 1 H and 195 Pt NMR and X-ray data.

13C-{103Rh} double resonance spectra of rhodium(I) and rhodium(-I) carbonyl complexes

Abstract 103 Rh Chemical shifts of a variety of mono- and di-nuclear rhodium carbonyl complexes are reported together with the modifications to the probe and decoupler unit of a JEOL PS-100 PFT spectrometer which enable these 103 Rh-decoupled 13 C NMR measurements to be made. These data are discussed in conjunction with 13 C NMR data on other rhodium carbonyls.

31P and 195Pt NMR spectra of [Pt(PPh32(μ-η2-C2H4−nXn)] (n = 0 … 4; X = CN, COOMe)

Abstract 31 P and 195 Pt NMR measurements on compounds of the type [Pt(PPh 3 ) 2 (μ-η 2 -C 2 H 4− n X n )] ( n = 0…4; X = CN, COOMe) are reported and discussed.

Preparation and properties of acetyliodotricarbonylcobaltate; a novel product from the reaction of methyl iodide with tetracarbonylcobaltate

Abstract The reaction of PPN[Co(CO) 4 ] with an excess of methyl iodide in THF at 0°C gives almost quantitatively PPN[Co(CO) 3 {C(O)CH 3 })I], which has been shown by X-ray crystallography and spectroscopic measurements to adopt a trigonal bipyramidal structure with three carbonyls in the equatorial plane; it reacts with hydrogen or with sulfuric acid to give acetaldehyde, and with methanol/pyridine to give methyl acetate. The new anion is of interest as a potential intermediate in the cobalt/iodine catalyzed carbonylation or hydrocarbonylation of methanol.

13C{103Rh} nuclear magnetic resonance of [Rh7(CO)16]3−

Abstract Specific 103 Rh spin-decoupling has been used to make a complete assignment of the 13 C NMR spectrum of [Rh 7 (CO) 16 ] 13− . At room temperature 3 μ 2 -carbonyls exchange with 3 μ 1 -carbonyls; it is shown that this carbonyl exchange occurs around the outside of the metal polyhedron rather than rotation of part of the metal skeleton within the carbonyl polyhedron. The rhodium chemical shifts show a large alternation from low to high field along the C 3 -axis of the cluster.

Platinum(II) complexes containing 2-(alkenyl)pyridines

The ligands 2-(allyl)pyridine(APy), and 2-(1-methallyl)pyridine (1-MAPy) react with [Pt2X4(PEt3)2] (X = Cl or Br), in acetone solution to give complexes of the type [PtX(PEt3)L] [PtX3(PEt3)], (L = APy or 1-MAPy), which contain a bidentate 2-(alkenyl)pyridine, whereas the same reaction in benzene solution gives trans-[PtBr2(PEt3)L], (L = APy or 1-MAPy), which contains a monodentate 2-(alkenyl)pyridine; 1H NMR spectra indicate that both types of product undergo olefin exchange in solution. The same reaction with 2-(3-methallyl)-pyridine [2-(2-butenyl)pyridine] (3-MAPy), 2-(3,3-dimethylallyl)pyridine [2-(3-methyl-2-butenyl)pyridine] (3,3-DMAPy), and 2-(3-butenyl)pyridine (BPy), in either acetone or benzene solution, gives only trans-[PtBr2(PEt3)L]. The reaction of trans-[PtBr2(PEt3)L] (L = APy or 3-MAPy) with AgClO4 gives [PtBr(PEt3)L]ClO4. Complexes of the type [PtCl2L], which contain bidentate 2-(alkenyl)pyridines, result on reaction of L = APy, 3-MAPy, 3,3-DMAPy, BPy, MBPy with [Pt2Cl4(C2H4)2].