A Mononuclear and High-Spin Tetrahedral Ti II Complex

• Published in: Inorganic chemistry Vol. 59; no. 24; pp. 17834 - 17850
• Main Authors: Reinholdt, Anders, Pividori, Daniel, Laughlin, Alexander L, DiMucci, Ida M, MacMillan, Samantha N, Jafari, Mehrafshan G, Gau, Michael R, Carroll, Patrick J, Krzystek, J, Ozarowski, Andrew, Telser, Joshua, Lancaster, Kyle M, Meyer, Karsten, Mindiola, Daniel J
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society (ACS) 21-12-2020
• Subjects: INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Ions; Ligands; Mathematical methods; Molecular structure; Redox reactions
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.0c02586

A high-spin, mononuclear Ti
complex, [(Tp
)TiCl] [Tp
= hydridotris(3-
-butyl-5-methylpyrazol-1-yl)borate], confined to a tetrahedral ligand-field environment, has been prepared by reduction of the precursor [(Tp
)TiCl
] with KC
. Complex [(Tp
)TiCl] has a
A
ground state (assuming
symmetry based on structural studies), established
a combination of high-frequency and -field electron paramagnetic resonance (HFEPR) spectroscopy, solution and solid-state magnetic studies, Ti K-edge X-ray absorption spectroscopy (XAS), and both density functional theory and ab initio (complete-active-space self-consistent-field, CASSCF) calculations. The formally and physically defined Ti
complex readily binds tetrahydrofuran (THF) to form the paramagnetic adduct [(Tp
)TiCl(THF)], which is impervious to N
binding. However, in the absence of THF, the Ti
complex captures N
to produce the diamagnetic complex [(Tp
)TiCl]
(η
,η
;μ
-N
), with a linear Ti═N═N═Ti topology, established by single-crystal X-ray diffraction. The N
complex was characterized using XAS as well as IR and Raman spectroscopies, thus establishing this complex to possess two Ti
centers covalently bridged by an N
unit. A π acid such as CNAd (Ad = 1-adamantyl) coordinates to [(Tp
)TiCl] without inducing spin pairing of the d electrons, thereby forming a unique high-spin and five-coordinate Ti
complex, namely, [(Tp
)TiCl(CNAd)]. The reducing power of the coordinatively unsaturated Ti
-containing [(Τp
)TiCl] species, quantified by electrochemistry, provides access to a family of mononuclear Ti
complexes of the type [(Tp
)Ti═E(Cl)] (with E
= NSiMe
, N
CPh
, O, and NH) by virtue of atom- or group-transfer reactions using various small molecules such as N
SiMe
, N
CPh
, N
O, and the bicyclic amine 2,3:5,6-dibenzo-7-azabicyclo[2.2.1]hepta-2,5-diene.