Denis George Harold Ballard

Alkyl-bridged complexes of the d- and f-block elements. Part 2. Bis[bis(η-cyclopentadienyl)methylmetal(III)] complexes, and the crystal and molecular structure of the yttrium and ytterbium species

The reaction of [(η-C5H5)2MMe2AlMe2](M = Y, Dy, Ho, Er, Tm, or Yb) and pyridine in equimolar amounts gives a series of complexes [{M(η-C5H5)2Me}2] assigned a dimeric structure on the basis of 1H and 13C n.m.r. (M = Y) and i.r. data, and by crystal and molecular structural determinations of [{M(η-C5H5)2Me}2](M = Y or Yb). A similar reaction of [(η-C5H5)2ScMe2AlMe2] with a Lewis base L gives [Sc(η-C5H5)2Me(L)](L = pyridine or tetrahydrofuran). Other reactions described are of [{Y(η-C5H5)2Me}2] with Lewis bases (an amine, phosphine, or phosphine oxide) or with a Lewis acid [Al2MenCl6 –n](n= 2, 4, or 6). A single-crystal X-ray analysis of the isostructural [{M(η-C5H5)2Me}2] has been carried out to R 0.048 (Y) or 0.066 (Yb) and R′ 0.055 (Y) or 0.061 (Yb); the complexes have an approximately tetrahedral metal environment (space group P21/n) with the YMe2Y unit in the yttrium complex remarkably similar to AlMe2Al in [Al2Me6]. Important average bond lengths (A) and angles for the yttrium complex (Yb in parentheses) are: Y–C (cyclopentadienyl) 2.655(18)[2.613(13)] and Y–Me 2.545(11)[2.511(35)]; Y–C–Y 87.7(3)[86.6(3)] and Me–Y–Me 92.3(3)[93.4(4)].

A biotech route to polyphenylene

Starting from benzene and oxygen and using the genetically modified bacteria Pseudominium putida as an oxidation catalyst compound (6) is readily obtained; derivative of the latter are soluble in organic solvents and polymerise to give a soluble precursor (5) which can be used to make fibres and films which on heating are converted into polyphenylene fibres and films.

Alkyl-bridged complexes of the d- and f-block elements. Part 1. Di-µ-alkyl-bis(η-cyclopentadienyl)metal(III)dialkylaluminium(III) complexes and the crystal and molecular structure of the ytterbium methyl species

Reaction of [{M(η-C5H5)2Cl}2] with Li[AlR4], or in some cases Mg[AlR4]2, affords the novel crystalline complexes [(η-C5H5)2M(µ-R)2AlR2](M = Sc, Y, Gd, Dy, Ho, Er, Tm, or Yb, R = Me; or M = Sc, Y, or Ho, R = Et). The yttrium, unlike the scandium, complexes are fluxional at 40 °C, but at –40 °C bridging and terminal alkyl groups give distinct n.m.r. signals; ΔG‡ for site exchange in [(η-C5H5)2Y(µ-Me)2AlMe2] is 15.9 kcal mol–1 at 392 K. A di-µ-alkyl-bridged structure is confirmed by i.r. (bridging CH3 band at 1 250 and 1 235 cm–1), variable-temperature 1H and 13C n.m.r. (M = Sc or Y), and X-ray studies (M = Yb). Additional data are given on the less stable [(η-C5H5)2Ti(µ-Me)2AlMe2], [Ti(η-C5H5)2(AlMe3Cl)], and [(η-C5H5)2Ti(µ-H)2AlMe2](structure deduced in part from e.s.r. spectra). A single-crystal X-ray analysis of [(η-C5H5)2Yb(µ-Me)2AlMe2] has been carried out to R 0.036 and R′ 0.042; the complex has an approximately tetrahedral Yb and Al environment (space group Pna21) with the YbMe2Al unit strikingly similar to AlMe2Al in [Al2Me6]. Important bond lengths (t = terminal, b = bridge) and angles are: Yb–C (cyclopentadienyl, average) 2.61(3), Yb–Cb 2.59(3), Al–Cb 2.18(5), and Al–Ct 2.00(1)A; Yb–C–Al 79.9(1.6) and C–Al–C 113.3(8)°.

Alkyl bridged complexes of the group 3A and lanthanoid metals as homogeneous ethylene polymerisation catalysts

The fully characterised group 3A and lanthanoid metal complexes [M(η-C5H4R)2Me]2(M;Y or Er, RH, Me, or SiMe3, and MYb, RH or Me) and [M(η-C5H4R)2Me2AlMe2](MY, Er, Ho, or Yb RH or Me, and MY, RSiMe3) are active homogenous ethylene polymerisation catalysts; they show an intramolecular deactivation process involving abstraction of a cyclopentadinyl hydrogen which is completely suppressed with peralkylated derivatives.

Kinetically-Stable Lanthanide Metal Alkyls and Bridging Methyls

This paper presents results on three topics concerning synthetic, structural, and chemical studies relating to three new classes of lanthanide metal (M) alkyl: (i) methyl-bridged complexes involving the moiety \({\text{M}}_{\backslash Me/}^{/Me\backslash }AlM{e_2}\) (ii) methyl-bridged complexes involving the unit \({\text{M}}_{\backslash Me/}^{/Me\backslash }M\) and (iii) neutral, [MR3(thf)2], and anionic, [MR4]− or [M(CI)R’3]−, silylmethyl [R = Me3SiCH2, R’ = (Me3Si)2CH] complexes. Topic (iii) is not described herein (but was included in the lecture) (the reader is referred to the paper by J. L. Atwood, W. E. Hunter, R. D. Rogers, J. Holton, J. McMeeking, R. Pearce, and M. F. Lappert, J. C. S. Chem. Comm., 1978, 140). (Also covered in the lecture were results on alkyls of the early transition elements.)

Polymerisation of vinyl monomers with benzyl zirconium compounds

The photo-induced polymerisation of styrene by tetrabenylzirconium proceeds by two mechanisms depending on the wavelength of the radiation used.