Softer Is Better for Titanium: Molecular Titanium Arsenido Anions Featuring Ti≡As Bonding and a Terminal Parent Arsinidene
Mrinal Bhunia, Jacob S. Mohar, Christian Sandoval‐Pauker, Dominik Fehn, Eric S. Yang, Michael R. Gau, José M. Goicoechea, Andrew Ozarowski, J. Krzystek, Joshua Telser, Karsten Meyer, Daniel J. Mindiola
Abstract
We introduce the arsenido ligand onto the Ti IV ion, yielding a remarkably covalent Ti≡As bond and the parent arsinidene Ti═AsH moiety. An anionic arsenido ligand is assembled via reductive decarbonylation involving the discrete Ti II salt [K(cryptand)][(PN) 2 TiCl] ( 1 ) (cryptand = 222-Kryptofix) and Na(OCAs)(dioxane) 1.5 in thf/toluene to produce the mixed alkali ate-complex [(PN) 2 Ti(As)] 2 (μ 2 -KNa(thf) 2 ) ( 2 ) and the discrete salt [K(cryptand)][(PN) 2 Ti≡As] ( 3 ) featuring a terminal Ti≡As ligand. Protonation of 2 or 3 with various weak acids cleanly forms the parent arsinidene [(PN) 2 Ti═AsH] ( 4 ), which upon deprotonation with KCH 2 Ph in thf generates the more symmetric anionic arsenido [(PN) 2 Ti(As){μ 2 -K(thf) 2 }] 2 ( 5 ). Experimental and computational studies suggest the p K a of 4 to be ∼23, and the bond orders in 2, 3, and 5 are all in the range of a Ti≡As triple bond, with decreasing bond order in 4 .