UC Davis

This dissertation focuses on the synthesis and characterization of ferriotetrylenes, which are complexes featuring a two-coordinate E(II) (E = Ge, Sn, or Pb) σ-bonded to FeCp(CO)2 (Cp = η5-C5H5) and a terphenyl group. The reactivity of the ferriotrylenes with ammonia is also described. Additionally, the synthesis and characterization of the biscarboranyl complexes (bc)Sn·THF, [(bc)Sn]2KCl, and bc-CH=CH-bc (bc = 1,1′-bis(o-carborane) are also described. Single crystal X-ray crystallography was employed to establish the structural details of the solid-state structures. NMR spectroscopic studies (1H, 11B, 13C, 119Sn, 207Pb) were employed for the spectroscopic characterization of the novel complexes and the characterization of the products of their reactions with ammonia. Spectroscopic methods were also used to determine the energetics of the reversible reaction with ammonia. New compounds were additionally characterized by UV-visible and infrared spectroscopy.The ferriogermylene ArMe6GeFeCp(CO)2 (ArMe6 = −C6H3-(C6H2-2,4,6-CH3)2) was synthesized by salt metathesis of the terphenyl germanium chloride (ArMe6GeCl) with the potassium salt of the iron cyclopentadienyl dicarbonyl anion (K[FeCp(CO)2]). In the solid state, ArMe6GeFeCp(CO)2 can form one of three crystalline polymorphs in green, red, or dichroic red-green crystals. Regardless of polymorph, ArMe6GeFeCp(CO)2 is spectroscopically and structurally similar to its more substituted derivative AriPr4GeFeCp(CO)2 (AriPr4 = −C6H3-(C6H3-2,6-iPr)2). Additionally, it was shown to react with H2O to afford the oxidative addition product ArMe6Ge(OH)(H)FeCp(CO)2. The complexes ArGeFeCp(CO)2 (Ar = ArMe6 or AriPr4) were shown to react with ammonia to afford the insertion products ArGe(NH2)(H)FeCp(CO)2 (Ar = ArMe6 or AriPr4). Salt metathesis was also employed in the synthesis of the two tin derivatives ArMe6SnFeCp(CO)2 and ArMe6SnFeCp*(CO)2 (Cp* = η5-C5Me5). The compound ArMe6SnFeCp(CO)(PMe3) was produced through a phosphine-carbonyl exchange reaction. Spectroscopic and structural comparisons of these ferriostannylenes and the more substituted derivatives ArSnFeCp(CO)2 (Ar = AriPr4 or AriPr6) showed the effect of the substituents on the central Sn atom. Increasing the size of the alkyl substituents on the aryl groups (aryl = terphenyl or cyclopentadienyl) narrows the interligand angle at Sn and causes a corresponding bathochromic shift of the HOMO→LUMO transition in the UV-vis spectra. Changing a CO ligand on the Fe fragment to PMe3 widens the interligand angle at Sn while causing a bathochromic shift of the HOMO→LUMO transition in the UV-vis spectrum. The ferriostannylenes ArSnFeCp(CO)2 (Ar = ArMe6 or AriPr4) were observed to react reversibly with ammonia. Visually, the reactions followed a similar color pattern to the reaction of the ferriogermylenes ArGeFeCp(CO)2 (Ar = ArMe6 or AriPr4) with ammonia. Variable temperature 1H NMR studies determined that the free energy of the reversible reaction of AriPr4SnFeCp(CO)2 with ammonia was essentially thermoneutral and are in good agreement with DFT calculations made by the Goicoechea research group on a phosphine system that displayed a related thermoneutral, reversible activation of ammonia. The ferrioplumbylenes ArPbFeCp(CO)2 (Ar = ArMe6 or AriPr4) were synthesized in the same manner as the Ge and Sn congeners to complete the series. Spectroscopic and structural comparisons of the ArEFeCp(CO)2 (E = Ge, Sn, or Pb; Ar = ArMe6 or AriPr4) series revealed a pattern that is reflected in the ferriotetrylene reactivities towards ammonia. The compound ArMe6PbFeCp(CO)2 was inert in the presence of ammonia.