David A. Kort

Hafnium halide compounds of methyl substituted allyl ligands. Synthesis, crystal structure and dynamics of (η5-C5Me5)(η3-1,2,3-Me3allyl)HfBr2 and (η5-C5Me5)(η3-1,1,2-Me3allyl)HfBr2

Abstract The reaction of Cp*HfCl3 with (1,2,3-Me3allyl)MgBr or (1,1,2-Me3allyl)MgBr and excess MgBr2 yields Cp*(1,2,3-Me3allyl)HfBr2 and Cp*(1,1,2-Me3allyl)HfBr2. X-ray crystallography of these compounds shows a bent-metallocene-type geometry, with steric congestion in the asymmetrically methylated compound causing the greatest distortion yet observed of an η3-allyl ligand towards an η1binding mode for an early-transition metal complex. For Cp*(1,2,3-Me3allyl)HfBr2: cell constants a=14.581(7), b=14.725(8), c=8.291(3) A; space group Pcmn; R=0.0425, Rw=0.0397. For Cp*(1,1,2-Me3allyl)HfBr2: cell constants a=9.158(2), b=13.141(4), c=14.575(3) A, β=101.06(2)°; space group P21/n; R=0.0383, Rw=0.0401. A variable temperature 1H NMR study indicates that the allyl ligand in (1,1,2-Me3allyl)HfBr2 undergoes η3-η1 isomerization (ΔG‡(−53 °C)=40.9± 1 kJ/mol).

Reactions of the dirhenium(II) complexes Re 2 X 4 (μ-dppm) 2 (X=Cl, Br; dppm =Ph 2 PCH 2 PPh 2 ) with isocyanides: Part XX1For Part XIX see Ref. [1].1. Oxidation of the complexes Re2X4(μ-dppm)2(L) (X=Cl or Br; dppm=Ph2PCH2PPh2; L=t-BuNC, XylNC or CO) to the edge-sharing bioctahedral dirhenium(III) cations [Re2(μ-X)2(μ-dppm)2X3(L)]+

Abstract The reactions of the halogens X2 (X=Cl or Br) with the diamagnetic dirhenium(II) complexes Re2X4(μ-dppm)2(L), where dppm=Ph2PCH2PPh2, X=Cl or Br, and L=XylNC (xylyl isocyanide), t-BuNC or CO, and with salts of the edge-sharing bioctahedral species [Re2X3(μ-dppm)2(CO)(NCMe)2]+, provide convenient routes to the dirhenium(III) species [Re2X5(μ-dppm)2(L)]+. These cations, where L=XylNC, t-BuNC or CO, have been isolated as their halide (Cl− or Br3−), [PF6]− and [O3SCF3]− salts. IR spectroscopy shows that terminal RNC and CO ligands are present, and a crystal structure determination of the complex [Re2Cl5(μ-dppm)2(CO)]PF6 confirms that the cation has the edge-sharing bioctahedral structure [Re2(μ-Cl)2(μ-dppm)2Cl3(CO)]+ with a formal ReRe bond (ReRe distance=2.6607(4) A). 31P-NMR spectroscopy indicates that these salts are weakly paramagnetic, with their P resonances exhibiting unusually large upfield shifts.

Reactions of the dirhenium(II) complexes Re2X4(μ-dppm)2 (X=Cl, Br; dppm =Ph2PCH2PPh2) with isocyanides

Abstract The reactions of the halogens X2 (X=Cl or Br) with the diamagnetic dirhenium(II) complexes Re2X4(μ-dppm)2(L), where dppm=Ph2PCH2PPh2, X=Cl or Br, and L=XylNC (xylyl isocyanide), t-BuNC or CO, and with salts of the edge-sharing bioctahedral species [Re2X3(μ-dppm)2(CO)(NCMe)2]+, provide convenient routes to the dirhenium(III) species [Re2X5(μ-dppm)2(L)]+. These cations, where L=XylNC, t-BuNC or CO, have been isolated as their halide (Cl− or Br3−), [PF6]− and [O3SCF3]− salts. IR spectroscopy shows that terminal RNC and CO ligands are present, and a crystal structure determination of the complex [Re2Cl5(μ-dppm)2(CO)]PF6 confirms that the cation has the edge-sharing bioctahedral structure [Re2(μ-Cl)2(μ-dppm)2Cl3(CO)]+ with a formal ReRe bond (ReRe distance=2.6607(4) A). 31P-NMR spectroscopy indicates that these salts are weakly paramagnetic, with their P resonances exhibiting unusually large upfield shifts.