This thesis reports the preparation of new pentafluorosulfanylimino (SF₅N=) derivatives, which have been synthesized from pentafluorosulfanyl isocyanate, SF₅NCO, pentafluorosulfanylamine, SF₅NH₂, and pentafluorosulfanyliminosulfur difluoride, SF₅N=SF₂. Reactions of SF₅NCO, SF₅N=SF₂, and SF₅NH₂, with appropriate substrates have produced SFN=S(CH₃)₂, SF₅N=CHC₆H₅, SF₅N=SCl₂, (SF5N=)₂C, (SF5N=)₂S and SF₅N=PCl₃, some of which are new compounds and some of which represent improved routes to compounds previously reported. When N,N'-bis(pentafluorosulfanyl)urea, (SF₅NH)₂CO, reacted with carbonyl fluoride SF₅NCO was formed. The reactivity of SF₅NCO in several basic reaction types including nucleophilic substitution, addition, exchange and coupling reactions was examined. Pentafluorosulfanyl isocyanate and dimethyl sulfoxide reacted to produce a crystalline product identified by its H-1 and F-19 nmr and in spectra as SF₅N-S(CH₃)₂. Pentafluorosulfanyl isocyanate and benzaldehyde reacted to produce a yellow solution and carbon dioxide. The solution was determined by spectroscopic mean to contain SF₅N=CHC₆H₅, a novel, electron-deficient Schiff base. Pentafluorosulfanylisocyanate and PCl5 reacted readily at 60-80° producing SF₅N=CCl₂ and POCl₃. A slow reaction between SF₅NCO and excess AgF₂ took place at room temperature. Infrared analysis of the reaction mixture at increasing temperatures gave evidence for formation and subsequent decomposition ofSF₅N=NSF₅. Pentafluorosulfanyliminosulfur difluoride (obtained from irradiation of N≡SF₃) reacted at room temperature with PCl₅ to produce SF₅N=SCl₂, a pale yellow liquid which rapidly attacked mercury, and reacted with AgF₂ (producing SF₅N=SF₂) and with SF₅NH₂(producing SF₅N=S=NSF₅). Pentafluorosulfanylamine, SF₅NH₂, and PCl₅ reacted at room temperature to give SF₅N=PCl₃ a pale yellow liquid which reacted rapidly with mercury. Thiazyl trifluoride reacted with metal carbonyls (Ni(Co)₄ , Fe(CO)₅, Mo(CO)₆, Mn(CO)₆) and ferrocene to produce thiazyl trifluoride - transition metal complexes. Chemical similarities between SF₅NCO and SF₅N=SF₂ with respect to nucleophilic substitution, exchange and coupling reaction reflect the similarity in bonding expected in these two systems. However, the failure of SF₅N=SF₂ and compounds containing the -N=SF₂ group to undergo additional reactions with polar reagents indicates some gross discrepancy from the usual behavior of these multiply bonded systems. Thus, a theoretical study of -N=SF₂ system was undertaken to clarify the role and magnitude of d-orbitals in the bonding of -N=SF₂ compounds. Theoretical calculations (CNDO) of the total energy of SF₅N=SF₂ , CF3N=SF₂ , C₂ F₅N=SF₂ , and FCON=SF₂ as a function of rotation about the N-S(IV) multiple bond showed that each total energy curve possessed a broad, flat minimum. Rotamers derived with only slight excitation would possess equal energy. Therefore, this multiple bond is nonrigid in contrast to the usual concept of the pπ-pπ double bond. The d-orbital contribution accounts for approximately 50% of the total π-bonding and is practically independent of the nature of the substituents on the nitrogen atom. Low temperature F-19 nmr studies showed that splittings occurred which can be explained on the basis of the total energy curves derived from the calculations. / Doctor of Philosophy