Answer Happy

N N N N 7. (15 points) A recent JACS paper by researchers at Los Alamos studied two polymeric coordination complexes [Fe(Htrz)3].[CIO]zn (1) and [Ni(Htrz)a).[CIO4)2 (2), with the structure shown below (Nguyen et al. J. Am. Chem. Soc. 2020, 142(10) 4842-4851). The authors report that when the Fe(II) compound (1) has a thermally-induced spin crossover, it becomes impact sensitive. The spin transition is reversible, leading to a new class of switchable explosive materials. a. Complexes 1 and 2 both have octahedral H coordination of the metal center with L-type [CIO Alan triazolate ligands. Sketch a d orbital splitting diagram for each octahedral complex, and fill in the correct number of d electrons for the Fe(II) and Ni(II) complexes. For the Fe(II) complex 1, sketch the diagram for both the low-spin and high-spin configurations. b. The researchers observed a spin crossover event for complex 1, where the complex switched from the low-spin state to the high-spin state. What H would the spin-only magnetic moment us be for the M = Fe (1), Ni (2) low-spin and high-spin states of complex 1? c. Complex 2 was synthesized as a "control" with no spin crossover behavior. Why does complex 2 not exhibit a spin transition similar to 1? d. The researchers predicted that the metal-ligand bonds would lengthen as a result of the spin crossover in complex 1, which is what caused it to become impact sensitive (and useful as a switchable explosive material). Why would the bond length increase upon the transition from low spin to high spin? (Read the paper for a hint!) U 'N