%0 DATA
%A Wesley A., Hoffert
%A Anthony K., Rappé
%A Matthew P., Shores
%D 2010
%T Unusual Electronic Effects Imparted by Bridging Dinitrogen: an Experimental and Theoretical Investigation
%U https://acs.figshare.com/articles/Unusual_Electronic_Effects_Imparted_by_Bridging_Dinitrogen_an_Experimental_and_Theoretical_Investigation/2721094
%R 10.1021/ic101528d.s001
%2 https://acs.figshare.com/ndownloader/files/4397047
%K RC
%K quintet ground states
%K Electronic structure calculations
%K doublet ground state
%K quartet
%K Unusual Electronic Effects Imparted
%K dmpe
%K Cp
%K 3 exhibits temperature
%K orbital
%K complex
%K Cr oxidation states
%K B 3LYP
%K model
%X We describe the preparation, structural and magnetic characterizations, and electronic structure calculations for a redox-related family of dinitrogen-bridged chromium acetylide complexes containing the [RC_{2}Cr(μ-N_{2})CrC_{2}R]^{n+} (R = Ph−, ^{i}Pr_{3}Si−; *n* = 0, 1, 2) backbone: [(dmpe)_{4}Cr_{2}(C_{2}Ph)_{2}(μ-N_{2})] (**1**), [(dmpe)_{4}Cr_{2}(C_{2}Si^{i}Pr_{3})_{2}(μ-N_{2})] (**2**), [(dmpe)_{4}Cr_{2}(C_{2}Si^{i}Pr_{3})_{2}(μ-N_{2})]BAr^{F}_{4} (**3**), and [(dmpe)_{4}Cr_{2}(C_{2}Si^{i}Pr_{3})_{2}(μ-N_{2})](BAr^{F}_{4})_{2} (**4**). Compounds **3** and **4** are synthesized via chemical oxidation of **2** with [Cp_{2}Co]^{+} and [Cp*_{2}Fe]^{+}, respectively. X-ray structural analyses show that the alteration of the formal Cr oxidation states does not appreciably change the Cr−N−N−Cr skeletal structures. Magnetic data collected for **2** and **4** are consistent with high-spin triplet and quintet ground states, respectively. The mixed-valent complex **3** exhibits temperature dependent magnetic behavior consistent with a quartet ⇌ doublet two-center spin equilibrium. Electronic structure calculations (B3LYP) performed on the full complexes in **2** and **4** suggest that the high-spin states arise from singly occupied orthogonal π* orbitals coupled with a variable occupation of dδ orbitals. Significant N−N and Cr−N π-bonding pins the occupation of the π manifold, leading to variable occupation of the dδ space. In contrast, mixed-valent **3** is not well described by a B3LYP hybrid density functional model. A [9,11] CAS-SORCI study on a simplified model of **3** reproduces the observed Hund’s rule violation for the *S* = 1/2 ground state and places the lowest quartet 1.45 kcal/mol above the doublet ground state.