Ruthenium Dihydridobis(pyrazolyl)borate Complexes Adopting a κ3 N,N,H, κ2 N,H, or κ2 N,N Bonding Mode

Ruthenium complexes containing the dihydridobis(3,5-bis(trifluromethyl)pyrazolyl)borate ligand Bp (CF3)2 have been prepared and structurally characterized. Reaction of (Bp (CF3)2 )RuH(COD) ( 1a ) with 2 equiv of bulky phosphines PR 3 under 3 bar of H 2 produces the hydrido(dihydrogen) complexes (Bp (CF3)2 )RuH(H 2 )(PR 3 ) 2 (R = Cy, 2a; R = i Pr, 3a ). X-ray structural analysis of 3a confirms a κ 2 N,H bonding mode of the Bp (CF3)2 ligand. In the absence of dihydrogen, the monohydride complex (Bp (CF3)2 )RuH(COD)(PCy 3 ) ( 4a ) is isolated. Upon pressurization to 3 bar H 2, 4a converts into (Bp (CF3)2 )RuH(H 2 )(PCy 3 ) ( 5a ) with rechelation of the pendant pyrazolyl ring and hydrogenation of the COD ligand. Addition of 2 equiv of PPh 3 or Ppyl 3 to 1a under 3 bar of H 2 leads to the formation of the corresponding hydrido complexes (Bp (CF3)2 )RuH(PR 3 ) 2 (R = Ph, 6a; R = pyl, 7a ). Under similar conditions, 1a reacts with 2 equiv of t BuNH 2 to produce the amine adduct (Bp (CF3)2 )RuH( t BuNH 2 ) 2 ( 8a ). By addition of 1 equiv of MeI to 8a, the iodo complex (Bp (CF3)2 )RuI( t BuNH 2 ) 2 ( 9a ) is isolated and characterized by an X-ray structural determination. The analogous chloro complex (Bp (CF3)2 )RuCl( t BuNH 2 ) 2 ( 10a ) can be prepared by stirring a dichloromethane solution of 8a for 18 h. In the absence of dihydrogen, 1a reacts with a large excess of t BuNH 2 to give (Bp (CF3)2 )RuH(COD)( t BuNH 2 ) ( 11a ). The structure with a κ 2 N,H coordination of the Bp (CF3)2 ligand is confirmed by an X-ray determination. Using the more sterically demanding diisopropylamine in the same conditions used for the formation of 8a, we could not isolate any complex. However upon N 2 atmosphere, the dinuclear species with a μ 2 -bridging dinitrogen ligand [(Bp (CF3)2 )RuH( i Pr 2 NH)] 2 (N 2 ) ( 12a ) could be isolated and characterized by a single-crystal X-ray determination. Addition of mesitylene to 1a produces the arene complex (Bp (CF3)2 )RuH(η 6 -C 6 H 3 Me 3 ) ( 13a ). The X-ray structure determination gave conclusive evidence for the κ 2 N,N bonding mode of the Bp (CF3)2 ligand. When exposing 1a to a CO atmosphere, the new acyl(dicarbonyl) complex (Bp (CF3)2 )Ru(COC 8 H 13 )(CO) 2 ( 14a ) is isolated in very high yield. Its structure is fully characterized on the basis of 2D homonuclear and heteronuclear correlation NMR data and by an X-ray structural determination. Similar reactions have been performed using the nonfluorinated complex (Bp Me2 )RuH(COD) ( 1b ) as starting material. The analogous complexes 2b, 4b − 6b, and 14b have been obtained. The variation of of the hapticity of the Bp ligand plays a crucial role in this chemistry, but the fluorinated substituents have a limited influence.