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High-spin face-capped deltahedra in divanadadicarbaboranes are very different from the singlet structures of chromium
Horaţiu Casian1, Alexandru Lupan1, R Bruce King2
1Faculty of Chemistry and Chemical Engineering, Babeş-Bolyai University, Cluj-Napoca, Romania. alexandru.lupan@ubbcluj.ro.
Abstract:
Using density functional theory (DFT), divanadadicarbaboranes Cp2V2C2Bn-4Hn-2 are found to have very different low-energy structures than the corresponding dichromadicarbaboranes Cp2Cr2C2Bn-4Hn-2. Thus, the low-energy divanadadicarbaborane structures with n vertices have triplet or quintet states rather than singlet spin states, frequently based on an (n - 1)-vertex VC2Bn-4 deltahedron having a face capped by the second vanadium atom bearing most of the spin density. Such structures are analogous to the low-energy structures of dimanganaboranes Cp2Mn2Bn-2Hn-2, even though the vanadium and manganese systems are not isoelectronic with each other. Most of the low-energy 8-vertex Cp2V2C2B4H6 structures are based on the hexagonal bipyramid, whereas most of the low-energy 9- and 10-vertex structures are based on the 9-vertex isocloso deltahedron. The bicapped square antiprism capped by a high-spin vanadium vertex is characteristic of the low-energy 11-vertex Cp2V2C2B7H9 structures. Similarly, an 11-vertex closo deltahedron capped by a high-spin vanadium vertex is the lowest energy Cp2V2C2B8H10 structure by a substantial margin of ∼18 kcal mol-1.
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