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Synthesis, Characterization, and Reactivity of Titanocene Cyclic Organohydroborates; Synthesis, Spectroscopic Studies, and Structures of Lanthanide(II)-Cobalt Carbonyl Complexes

by Plecnik, Christine Emily

Abstract (Summary)
PART I: Low valent, paramagnetic titanocene (Ti(III)) cyclic organohydroborates Cp 2 Ti{(?-H) 2 BR 2 } (R 2 = C 4 H 8 , C 5 H 10 , C 8 H 14 ) were synthesized, and their chemistry was explored. This family of complexes possess electron deficient Ti-H-B bridges that are reactive towards Lewis acids and bases. Bridging hydride ion is abstracted by the Lewis acidic reagent B(C 6 F 5 ) 3 . Depending on the coordinating ability of the solvent, one of two distinct products is formed: Cp 2 Ti{(?-H) 2 B(C 6 F 5 ) 2 } from the noncoordinating solvent toluene and [Cp 2 Ti(L) 2 ] [HB(C 6 F 5 ) 3 ] (L = Et 2 O, THF) from the coordinating solvents Et 2 O and THF. The labile Et 2 O ligands of [Cp 2 Ti(OEt 2 ) 2 ] [HB(C 6 F 5 ) 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 PMe 3 , which provides Cp 2 TiH(PMe 3 ). Ammonia primarily splits the bridge in an unsymmetrical fashion, which leads to [Cp 2 Ti(NH 3 ) 2 ] [H 2 B(C 6 F 5 ) 2 ]. The new chlorine-bridged titanocene cation [Cp 2 Ti(?-Cl) 2 TiCp 2 ] ^+ was also produced. PART II: Novel lanthanide(II)-cobalt carbonyl complexes were prepared and structurally characterized (IR and ^59 Co 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) x Yb{(?-CO) y Co(CO) 4-y } 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 Et 2 O generates 2-D isocarbonyl polymeric arrays, {(Et 2 O) 3 Ln[Co 4 (CO) 11 ]} ? . The [Co 4 (CO) 11 ] 2- anion, undiscovered until now, results from oxidation/condensation of [Co(CO) 4 ] - . Two isomers of [Co 4 (CO) 11 ] 2- (pseudo-C 3v and C 2v symmetries) were observed. The compound {(Et 2 O) 3 Yb[Co 4 (CO) 11 ]} ? is unstable in Lewis basic solvents, and the cluster undergoes disproportionation. PART I: Low valent, paramagnetic titanocene (Ti(III)) cyclic organohydroborates Cp 2 Ti{(?-H) 2 BR 2 } (R 2 = C 4 H 8 , C 5 H 10 , C 8 H 14 ) were synthesized, and their chemistry was explored. This family of complexes possess electron deficient Ti-H-B bridges that are reactive towards Lewis acids and bases. Bridging hydride ion is abstracted by the Lewis acidic reagent B(C 6 F 5 ) 3 . Depending on the coordinating ability of the solvent, one of two distinct products is formed: Cp 2 Ti{(?-H) 2 B(C 6 F 5 ) 2 } from the noncoordinating solvent toluene and [Cp 2 Ti(L) 2 ] [HB(C 6 F 5 ) 3 ] (L = Et 2 O, THF) from the coordinating solvents Et 2 O and THF. The labile Et 2 O ligands of [Cp 2 Ti(OEt 2 ) 2 ] [HB(C 6 F 5 ) 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 PMe 3 , which provides Cp 2 TiH(PMe 3 ). Ammonia primarily splits the bridge in an unsymmetrical fashion, which leads to [Cp 2 Ti(NH 3 ) 2 ] [H 2 B(C 6 F 5 ) 2 ]. The new chlorine-bridged titanocene cation [Cp 2 Ti(?-Cl) 2 TiCp 2 ] ^+ was also produced. PART II: Novel lanthanide(II)-cobalt carbonyl complexes were prepared and structurally characterized (IR and ^59 Co 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) x Yb{(?-CO) y Co(CO) 4-y } 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 Et 2 O generates 2-D isocarbonyl polymeric arrays, {(Et 2 O) 3 Ln[Co 4 (CO) 11 ]} ? . The [Co 4 (CO) 11 ] 2- anion, undiscovered until now, results from oxidation/condensation of [Co(CO) 4 ] - . Two isomers of [Co 4 (CO) 11 ] 2- (pseudo-C 3v and C 2v symmetries) were observed. The compound {(Et 2 O) 3 Yb[Co 4 (CO) 11 ]} ? is unstable in Lewis basic solvents, and the cluster undergoes disproportionation.
Bibliographical Information:

Advisor:

School:The Ohio State University

School Location:USA - Ohio

Source Type:Master's Thesis

Keywords:titanocene organohydroborate lanthanide cobalt carbonyl

ISBN:

Date of Publication:01/01/2003

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