N-H cleavage as a route to new pincer complexes of high-valent rhenium.
A novel PNN-type pincer ligand has been accessed via imine reduction with LiAlH4to provide the phosphine diamino proligand, PNHNH(1). The ligand, 1, as well as PNHP can be metallated directly, via N-H cleavage, with L2ReOX2(OEt) precursors to access six-coordinate (PNP)ReOCl2(2) and (PNNH)ReOX2(3-Cl, X = Cl; 3-Br, X = Br) in good yield. 3-Cl and 3-Br undergo dehydrohalogenation upon treatment with NEt3, furnishing the five-coordinate phosphine/diamido PNN-type compounds (PNN)ReOX (4-Cl, X = Cl; 4-Br, X = Br) in excellent yield, presenting as a mixture of rotameric diasteromers. The reversibility of this deprotonation, and the coordinative unsaturation of 4-Cl is shown in reactions with HCl(aq)and PMe3providing 3-Cl and 4-PMe3, respectively. Treatment of 4-Cl with AgOAc, AgOTf, or NaHBEt3lead to formation of (PNN)ReO(OAc) (4-OAc), (PNN)ReO(OTf) (4-OTf), and (PNN)ReO(H) (4-H), all isolated in excellent yields in varying diasteromeric ratios. The nature of the isomerism was analyzed based on solid-state structural studies and solution NMR data.
Department of Chemistry, Texas A&M University, TAMU - 3255, College Station, TX 77842, USA. ozerov@chem.tamu.edu.
Alex J
AJ
Kosanovich
Department of Chemistry, Texas A&M University, TAMU - 3255, College Station, TX 77842, USA. ozerov@chem.tamu.edu.
Wei-Chun
WC
Shih
Department of Chemistry, Texas A&M University, TAMU - 3255, College Station, TX 77842, USA. ozerov@chem.tamu.edu.
Rodrigo
R
Ramírez-Contreras
Department of Chemistry, Texas A&M University, TAMU - 3255, College Station, TX 77842, USA. ozerov@chem.tamu.edu.
Oleg V
OV
Ozerov