Synthesis, characterization, and reactivity of titanocene cyclic organohydroborates; synthesis, spectroscopic studies, and structures of lanthanide(II)-cobalt carbonyl complexes

Part I. Low valent, paramagnetic titanocene (Ti(III)) cyclic organohydroborates Cp₂Ti{lcub}(μ-H)₂BR₂{rcub} (R₂ = C₄H₈, C₅H₁₀, C₈H₁₄) were synthesized, and their chemistry was explored. This family of complexes possess electron deficient Ti-H-B bridges that are by the Lewis acidic reagent B(C₆F₅)₃. Depending on the coordinating ability of the solvent, one of two distinct products is formed: Cp₂Ti{lcub}(μ-H)₂B(C₆F₅) ₂{rcub} from the noncoordinating solvent toluene and [Cp₂Ti(L) ₂] [HB(C₆F₅)₃] (L = Et₂O, THF) from the coordinating solvents Et₂O and THF. The labile Et ₂O ligands of [Cp₂Ti(OEt₂)₂] [HB(C ₆F₅)₃] are displaced in THF and toluene. The titanocene cyclic organohydroborates react with Lewis bases to cleave the double hydrogen bridge. Symmetrical bridge division is induced by PMe₃, which provides Cp₂TiH(PMe₃). Ammonia primarily splits the bridge in an unsymmetrical fashion, which leads to [Cp₂Ti(NH₃) ₂] [H₂B(C₆F₅)₂]. The new chlorine-bridged titanocene cation [Cp₂Ti(μ-Cl)₂TiCp ₂]+ was also produced.; Part II. Novel lanthanide(II)-cobalt carbonyl complexes were prepared and structurally characterized (IR and 59Co NMR spectroscopies, single-crystal X-ray diffraction, laser desorption/ionization mass spectrometry). The transmetalation reaction between Ln and Hg[Co(CO) ₄]₂ in coordinating solvent is a facile route toward two types of heterometallic compounds, solvent-separated ion pairs and isocarbonyls. Product formation is dictated by the relative nucleophilicities of the solvent and [Co(CO)₄]−. Transmetalation in strong (Pyr) or moderately strong (THF, DME) coordinating solvents affords discrete ion pairs [Ln(L)_x] [Co(CO)₄]₂ . Isocarbonyls [(L)_xYb{lcub}(μ-CO) _yCo(CO)_4−y{rcub} ₂·zTol]_∞ with 2-D sheetlike structures are produced by dissolving the salts [Yb(L)₆] [Co(CO) ₄]₂ in toluene. Transmetalation in the weak donating solvent Et₂O generates 2-D isocarbonyl polymeric arrays, {lcub}(Et₂O) ₃Ln[Co₄(CO)₁₁]{rcub}_∞. The [Co ₄(CO)₁₁]2− anion, undiscovered until now, results from oxidation/condensation of [Co(CO)₄]− . Two isomers of [Co₄(CO)₁₁]2− (pseudo-C_3υ and C_2υ symmetries) were observed. The compound {lcub}(Et₂O)₃Yb[Co ₄(CO)₁₁]{rcub}_∞ is unstable in Lewis basic solvents, and the cluster undergoes disproportionation.