Stephen R. Stobart

Pyrazolyl-bridged iridium dimers 15. Synthesis of binuclear cyclopentadienyl Ir(III) complexes and the rhodium analogues: reductive access to the bimetal (II) state

Mononuclear M(III) complexes of formulae [MCp∗Cl(3−n(R2pzH)n](n−1)+ (M = Rh or Ir; n = 1,2) have been prepared through reactions of pyrazole (pzH, i.e. R = H) or substituted pyrazoles (R = Me or t-butyl) with rhodium and iridium cyclopentadienyl or pentamethylcyclopentadienyl precursors; for n = 1, the crystal and molecular structure has been determined by using X-ray diffraction (11, M = Rh, R = H, FW = 377.96 g mol−1, space group P21/n, a = 7.1685(7), b = 15.740(3), c = 13.407(4) A, β = 94.50(3)°). Dinuclear complexes of formulae [M(η5-C5R5)Cl(μ-pz)]2 (18, M = Rh, R = H; 19, M = Rh, R = H; 21, M = Ir, R = H; 20, M = Ir, R = Me; 21, M = Ir, R = H) containing pyrazolyl bridges can be isolated through further reaction of the mononuclear compounds, or more directly from the chloro-bridged dimers [M(η5-C5R5)Cl2]2 by treatment with pyrazole in the presence of Et3N, although the dipyrazole iridium cation [IrCp∗Cl(pzH)2]+ (16) does not undergo this type of dimerization. The dimeric complexes, which possess a ‘chair’ geometry about the 6-membered bridging heterometallocycle, have been shown to undergo a core conformational change (‘chair’: ‘boat’) upon chemical reduction or halide abstraction. Chloride abstraction from 18 yields the binuclear product [{RhCp∗(μ-pz)}2(μ-Cl)]BF4 (23) and reduction of either 18 or the C5H5 analog 19 gives access to the metal-metal bonded binuclear complexes [Rh(η5-C5R5)(μ-pz)]2, 25 (R = Me) and 26 (R = H), which adopt a ‘boat’ core conformation. The reactivity of the metal-metal bonded products has been investigated: a triply-bridged single-fragment oxidative addition product resulting from reaction with H+/MeOH ({[RhCp(μ-pz)]2(μ-OMe)}O2CCF3, 29) has been structurally characterized (FW = 614.2 g mol−1, space group P21/n, a = 12.9647(3), b = 13.805(3), c = 11.593(3) A, β = 90.44(2)°).

Organic chemistry of the iron—ruthenium centre

Abstract The dynamic behaviour (cis/trans isomerisation via CO migration) of [FeRu(CO)2 (μ-CO)2 (η-C5H5)2] in solution, the determination of the molecular structure of trans-[FeRu(CO)2(μ-CO)2(η-C5H5)2] by X-ray diffraction, and the developing organic chemistry of the iron—ruthenium centre are described.

Hydrogenation and rearrangement of coal-related aromatic and hydroaromatic molecules promoted under mild conditions by aluminium trichloride

Abstract The action of AlCl 3 on representative polyaromatic (naphthalene, anthracene, phenanthrene) and hydroaromatic (tetralin, dodecahydrotriphenylene) molecules under inert atmosphere conditions at 20 °C (hexane solution) or 70 °C (heptane solution) has been investigated. Even at these low temperatures conversion to hydrogenated and rearranged structures is significant, giving product distributions resembling those obtained from corresponding reactions conducted at 300–400 °C under hydrogen pressure.

Introduction of per(fluoroorganosilyl) peripheries into carbosilane dendrimers and related core-functionalized monodendrons gives rise to anomalous hydrodynamic and viscosimetric behavior

Platinum-catalyzed hydrosilylation of allyl-terminated ncarbosilane monodendrons using the silanes nSiHMe2[(CH2)nRf] (1a, nn = 2, Rf = n-C6F13; 1b, nn = 3, Rf = −C6F5) yields nfluorous, liquid analogues to [G-3], nBrC6H4(CH2)3SiMe[(CH2 n)3SiMe[(CH2)3SiMe[(CH2) n3SiMe2(CH2)nRf] n2]2]2 (7a, n = 2, Rf = nn-C6F13- ; 7b, n = 3, Rf n= −C6F5), intrinsic viscosities [η] for nwhich are unusually low, resulting in calculated hydrodynamic radii/A n(ca. 6.3, [G-1]; 8.3, [G-2]; 11.5, [G-3]) that imply unusually ncompact structures.