Crystal structures and solid-state reactivity of metal carboxylates and related acid salts

This thesis reports an investigation of the crystal structures and solid-state reactivity of metal carboxylates and related acid salts. Chapter One contains a summary of the research reported in this thesis. Chapter Two covers the crystal structures and photo-induced cyclodimerization of group Ia metal cinnamates and related acid salts. The metal salts studied include lithium cinnamate, potassium cinnamate and rubidium cinnamate. The acid salts studied include potassium hydrogen dicinnamate, rubidium hydrogen dicinnamate, ammonium hydrogen dicinnamate and diacid salt sodium dihydrogen tricinnamate. Upon exposure to UV light, the metal salts, acid salts and diacid salts undergo [2+2] photocycloaddition, and afford various photodimers (beta-truxinate derivatives, delta-truxinate derivatives and epsilon-truxillate derivates). Inspection of the crystal structures indicates that the cinnamate moieties in these materials are all arranged in a head-to-head orientation, consistent with the observed formation of the major product (beta-truxinate). The potentially reactive double bonds are arranged in a crisscross fashion; double bond disorder occurs in the acid salts where M = Rb or NH4+. In Chapter Three, the crystal structures and solid-state reactivity of metal acetylenedicarboxylates are reported and correlations between structure and solid-state reactivity are explored. Upon exposure to 60Co gamma-rays, solid metal acid acetylenedicarboxylates (M: Li, Na, K, Rb, Mg, Ca) and metal acetylenedicarboxylates (M: Li, Na, K, Rb, Zn) undergo a solid-state polymerization (each to a different extent), presumably to form conjugated acetylenic oligomers or polymers. Studies of the structures and solid-state reactivity indicate that the shorter the offset distance between acetylene groups, the faster chain growth the compound exhibits upon gamma-irradiation. Compounds with twist angles in the range (0-15°) are more reactive than those in the range (55-70°), when offset distances are similar. Chapter Four reports the crystal structures and solid-state reactivity of alkali metal hydrogen di-trans-2-butenoates (M= K, Rb) and ammonium trans-2-butenoate. Upon gamma-irradiation, potassium hydrogen di-trans-2-butenoate affords two products: potassium hydrogen (5R*)-5-methyl-2-heptenedioate and potassium hydrogen ( E)-5-ethyl-2-hexenedicarboxylate, while rubidium hydrogen di- trans-2-butenoate affords three products: rubidium hydrogen ( cis, trans)-nepetate, rubidium hydrogen (5R*)-5-methyl-2-heptenedioate and rubidium hydrogen 3-methyl-2-vinyl-pentanedioate. Inspection of the crystal structures shows that rubidium hydrogen di-trans-2-butenoate packs in a layer structure and potassium hydrogen di-trans-2-butenoate packs in a bilayer structure. Both structures contain multiple sets of short contacts between reactive groups. Reaction may take place either in one organic layer, as in the formation of cyclodimer, or between organic layers, where the reactants interpenetrate in an antiparallel or head-to-tail fashion, to form a dimer via Michael addition. In Chapter Five, the DOS and Windows versions of the program INTERLOBE DISTANCE are presented. The interlobe distance (referred to as "offset" above and in Chapter Two) is a measure of the overlap between a pair of orbitals and their orientation with respect to each other. Values for the sum of the two interlobe distances ≤ 3.5 A or single interlobe distances ≤ 1.8 A are good indicators for predicting solid-state reactions. The research presented in this thesis suggests that when predicting solid-state reactivity, interatomic distance and interlobe distance should both be considered. If both interatomic distance and interlobe distance are within the threshold values, the probability of reaction will be significantly greater.