Crystallographic studies of organoiodinanes, vanadium(IV) complexes with oxygen and sulfur donor ligands, and single crystal decomposition

Chapter I describes the crystal structures of a series of hypercovalent iodine(III) compounds. An unusual packing arrangement and potential secondary contact are observed in the structure of the 1:1 complex of 1-chloro-1,2-benziodoxolin-3(1 H)-one with tetra-n-butyl ammonium chloride. The nature of the coordination about iodine is considered relative to a previously published structure of 1-chloro-1,2-benziodoxolin-3(1H)-one. The crystalline structure of 1-bromo-1,3-dihydro-3-methyl-3-phenyl-1,2-benziodoxole exhibits a rare, stable iodine(III)-bromine hypercovalent bond. The geometry of the bromoiodinane is compared to the analogous iodine(III)-chlorine structure of 1-chloro-1,3-dihydro-3-methyl-3-phenyl-1,2-benziodoxole. Similarly, the structure of 1-azido-1,3-dihydro-3-methyl-3-phenyl-1,2-benziodoxole is compared to the previously published 1-azido-1,3-dihydro-3,3-bis(trifluoromethyl)-1,2-benziodoxole to demonstrate the effect of electron withdrawing axial groups on the 3-center, 4-electron bond. The structures of the acetoxy, trifluoroacetoxy, and tosyloxy derivatives of the 1,3-dihydro-3-methyl-3-phenyl-1,2-benziodoxoles further illustrate these effects. A clear trend is seen between the electronegativity of the external axial ligand and the observed iodine-axial ligand bond distance.; Chapter II focuses on a series of vanadium(IV) complexes with mixed sulfur and oxygen donor ligands. The non-oxo vanadium complex anion, tris(2-mercapto-4-methylphenolato)vanadate(IV), exhibits a geometry intermediate between trigonal prismatic and octahedral with the three oxygen and three sulfur ligands oriented in pseudofacial arrangement. The structure is compared to the previously published dimer complex featuring tris(o-mercaptophenolato)vanadium(IV) units linked through bridging sodium ions. The corresponding oxovanadium(IV) complexes using the 2-mercapto-4-methylphenolato and 4-methylphenolato ligands, mmp2− and mp2− , are also investigated. The complex dianions [VO(mp)₂] 2− and [VO(mmp)₂]2− crystallize in dramatically different modes with the former dimerizing via two bridging sodium ions and the latter polymerizing into one-dimensional chains in which each dianion pair is linked with a sodium ion. The thiovanadyl complex, [VS(mp)₂]2−, exhibits virtually the same dimeric crystal packing mode as its oxo analogue, [VO(mp)₂] 2−. This structure contains the rarely observed V=S2+ ion and provides more evidence for the constant increase in vanadyl bond length upon oxygen/sulfur exchange.; Chapter III describes the X-ray induced decomposition of a 2π _s + 2π_s intramolecular cycloaddition product to its precurser compound, syn-7,8-benzo-9,10-(9′,10 ′-phenanthro)tricyclo[4.2.22,5]dodeca-3,7,9-triene which is itself the product of a 4π_s + 4π_s photocycloaddition of dibenz[a,c]anthracene with 1,3-cyclohexadiene. The decomposition occurs within the single crystal and can be sampled over time through a disordered phase to a final ordered product phase. The structure of the decomposition product yields molecular geometry comparable to a previously reported single crystal structure of the 4π_s + 4π_s photocycloaddition of dibenz[a,c]anthracene with 1,3-cyclohexadiene which crystallized in the same space group but with a very different packing arrangement. Additional slight changes are observed in the packing of the initial structure as compared to the final structure.