David M. Dawson

Synthesis and reactivity of sterically hindered iminopyrrolato complexes of zirconium, iron, cobalt and nickel

The new bis(imino)pyrrole ligand 2,5-C4H2NH(CHNC6H3Pri2)2 (HL11111) reacts with Zr(NMe2)4 to give the 1∶1 complex (L11111)Zr(NMe2)3 (1), whereas the mono(imino)pyrrole 2-C4H3NH(CHNC6H3Pri2) (HL22222) substitutes two amido ligands to give (L22222)2Zr(NMe2)2 (2). The lithium salt LiL11111 reacts with ZrCl4 to give (L11111)ZrCl2(μ-Cl)2Li(OEt2)2 (3), while the reaction of LiL22222 with ZrCl4 or treating 2 with Me3SiCl gives (L22222)2ZrCl2. Iron(II) chloride reacts with LiL11111 to afford the bis(ligand) complex Fe(L11111)2 (5), while only one pyrrolato ligand is incorporated on reacting LiL11111 with CoCl2(thf) to give [Li(thf)4][CoCl2L11111] (6a). On warming, 6a readily loses thf to give [Li(thf)2][CoCl2L11111] (6b). By contrast, LiL22222 reacts with CoCl2 and NiCl2 to give the halide-free complexes Co(L22222)2 and Ni(L22222)2, respectively. The crystal structures of HL11111 and complexes 1, 2 and 5 are reported. In all cases the potentially tridentate ligand L11111 is two-coordinate. Mixtures of the halide-free bis(ligand) complexes with methylaluminoxane do not show any activity for ethene polymerisation; however, 3 and 4 catalyse the polymerisation of ethene, while 6 has moderate activity for the oligomerisation of ethene and propene to linear and branched products.

Calculating material criticality of transparent conductive electrodes used for thin film and third generation solar cells

The supply risk and exposure to supply shortage is becoming an important factor in the consideration of a mass low carbon technology roll-out. This study takes current criticality studies, which analyse the criticality of single raw materials, and extends it to calculate the relative criticality of multiple material transparent conductive electrodes (TCE). It compares the calculated criticality with the TCEs Haacke figure of merit. It is found that more recent TCEs developed to replace the commonly used indium tin oxide, such as flurine doped tin oxide and silver nanowires, can have a higher criticality, even though the materials themselves are currently less expensive.

Preparation of dimolybdenum carbonyl and ditungsten carbonyl complexes containing triple fluoro bridges

The reaction of [WH6(PMe2Ph)3] with HBF4·OEt2, under an atmosphere of carbon monoxide, in tetrahydrofuran gives [{W(CO)2(PMe2Ph)2}2(µ-F)3]BF4. The X-ray crystal structure of this compound reveals that the geometry about each tungsten atom is best considered as having a basal plane containing three fluorine atoms, (W–F)av 2.12(1)A, with the reamining four ligands (two carbon monoxide and two phosphines) forming a second, parallel plane, in which the two carbon monoxide ligands are mutually trans, (W–C)av 1.949(6)A, as are the two phosphines, (W–P)av 2.457(1)A. The spectroscopic characteristics of [{W(CO)2(PMe2Ph)2}2(µ-F)3]+ are discussed and from this the nature of species formed in the reactions of [MoH4(PR3)4](R3= Et3 or MePh2) with HBF4·OEt2 under an atmosphere of carbon monoxide can be inferred.

Preparation and crystal structure of [PHBu3][MoHCl4(PBu3)2]

The preparation of the series of anionic, paramagnetic, hydrido complexes [PHR3][MoHCl4(PR3)2](R = Et, X = Cl or Br; R = Bu, X = Cl; R3= Me2Ph, X = Br) from the reactions of anhydrous HX with [MoH4(PR3)4] in tetrahydrofuran is described. The structure of one example, [PHBu3][MoHCl4(PBu3)2], has been determined by X-ray crystallography. The co-ordination geometry of the anion is best described as a distorted pentagonal bipyramid, with apical chloro-groups [(Mo–Clax)av 2.423(10)A]. The hydride was located in the structure [Mo–H 1.83(4)A] and is displaced 0.31 A out of the equatorial plane towards one of the axial sites. The remaining ligands in the equatorial positions have bond lengths (Mo–Cleq)av 2.485(1) and (Mo–P)av 2.511 (5)A.