Solution structures and behavior of trans ‐RuH(η 1 ‐BH 4 ) (binap)(1,2‐diamine) complexes

The solution structures of a number of trans ‐RuH(η 1 ‐BH 4 )[( S )‐tolbinap](1,2‐diamine) precatalysts [TolBINAP = 2,2′‐bis(di‐4‐tolylphosphino)‐1,1′‐binaphthyl; 1,2‐diamine( S,S )‐ or ( R,R )‐1,2‐diphenylethylenediamine (DPEN), ethylenediamine (EN), and ( S )‐1,1‐di(4‐anisyl)‐2‐isopropylethylenediamine (DAIPEN)] have been determined using 2D NMR ( 1 H 1 H DQF‐COSY, 1 H 13 C HMQC, 1 H 31 P HSQC, and 1 H 15 N HSQC), and a double‐pulsed field‐gradient spin‐echo (DPFGSE) NOE technique. All the octahedral Ru complexes adopt a trans configuration with respect to the BH 4 and hydride ligands. Amine protons of trans ‐RuH(η 1 ‐BH 4 )[( S )‐tolbinap](1,2‐diamine) complexes undergo H/D exchange in (CD 3 ) 2 CDOD. This inherent high acidity, coupled with the lability and chemical properties of the BH 4 ligand, allows for precatalyst activation without the need for an added base, in contrast to trans ‐RuCl 2 [( S )‐tolbinap](1,2‐diamine) precatalysts, which require a strong base for generation of a catalytic species. The H/BH 4 complex in a 2‐propanol solution is converted to catalytically active [ trans ‐RuH{( S )‐tolbinap}{(S,S)‐dpen}(ROH)] + [(RO)(ROH) n ] − (R = (CH 3 ) 2 CH), a loosely associated ion pair of the discrete (solvated) cationic fragment and anionic species. Copyright © 2006 John Wiley & Sons, Ltd.