Tale of Three Molecular Nitrides: Mononuclear Vanadium (V) and (IV) Nitrides As Well As a Mixed-Valence Trivanadium Nitride Having a V 3 N 4 Double-Diamond Core.

Transmetallation of [VCl 3 (THF) 3 ] and [TlTp t Bu,Me ] afforded [(Tp t Bu,Me )VCl 2 ] ( 1 , Tp t Bu,Me = hydro-tris(3- tert- butyl-5-methylpyrazol-1-yl)borate), which was reduced with KC 8 to form a C 3v symmetric V II complex, [(Tp t Bu,Me )VCl] ( 2 ). Complex 1 has a high-spin ( S = 1) ground state and displays rhombic high-frequency and -field electron paramagnetic resonance (HFEPR) spectra, while complex 2 has an S = 3/2 4 A 2 ground state observable by conventional EPR spectroscopy. Complex 1 reacts with NaN 3 to form the V V nitride-azide complex [(Tp t Bu,Me )V≡N(N 3 )] ( 3 ). A likely V III azide intermediate en route to 3 , [(Tp t Bu,Me )VCl(N 3 )] ( 4 ), was isolated by reacting 1 with N 3 SiMe 3 . Complex 4 is thermally stable but reacts with NaN 3 to form 3 , implying a bis-azide intermediate, [(Tp t Bu,Me )V(N 3 ) 2 ] ( A ), leading to 3 . Reduction of 3 with KC 8 furnishes a trinuclear and mixed-valent nitride, [{(Tp t Bu,Me )V} 2 (μ 4 -VN 4 )] ( 5 ), conforming to a Robin-Day class I description. Complex 5 features a central vanadium ion supported only by bridging nitride ligands. Contrary to 1 , complex 2 reacts with NaN 3 to produce an azide-bridged dimer, [{(Tp t Bu,Me )V} 2 (1,3-μ 2 -N 3 ) 2 ] ( 6 ), with two antiferromagnetically coupled high-spin V II ions. Complex 5 could be independently produced along with [(κ 2 -Tp t Bu,Me ) 2 V] upon photolysis of 6 in arene solvents. The putative {V IV ≡N} intermediate, [(Tp t Bu,Me )V≡N] ( B ), was intercepted by photolyzing 6 in a coordinating solvent, such as tetrahydrofuran (THF), yielding [(Tp t Bu,Me )V≡N(THF)] ( B - THF ). In arene solvents, B-THF expels THF to afford 5 and [(κ 2 -Tp t Bu,Me ) 2 V]. A more stable adduct ( B-OPPh 3 ) was prepared by reacting B-THF with OPPh 3 . These adducts of B are the first neutral and mononuclear V IV nitride complexes to be isolated.