Ruthenium Dihydridobis(pyrazolyl)borate Complexes Adopting a κ<SUP>3</SUP> N,N,H, κ<SUP>2</SUP> N,H, or κ<SUP>2</SUP> 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) (<BO>1a</BO>) with 2 equiv of bulky phosphines PR<INF>3</INF> under 3 bar of H<INF>2</INF> produces the hydrido(dihydrogen) complexes (Bp^(CF3)2)RuH(H<INF>2</INF>)(PR<INF>3</INF>)<INF>2</INF> (R = Cy, <BO>2a</BO>; R = ⁱPr, <BO>3a</BO>). X-ray structural analysis of <BO>3a</BO> confirms a κ² N,H bonding mode of the Bp^(CF3)2 ligand. In the absence of dihydrogen, the monohydride complex (Bp^(CF3)2)RuH(COD)(PCy<INF>3</INF>) (<BO>4a</BO>) is isolated. Upon pressurization to 3 bar H<INF>2</INF>, <BO>4a</BO> converts into (Bp^(CF3)2)RuH(H<INF>2</INF>)(PCy<INF>3</INF>) (<BO>5a</BO>) with rechelation of the pendant pyrazolyl ring and hydrogenation of the COD ligand. Addition of 2 equiv of PPh<INF>3</INF> or Ppyl<INF>3</INF> to <BO>1a</BO> under 3 bar of H<INF>2</INF> leads to the formation of the corresponding hydrido complexes (Bp^(CF3)2)RuH(PR<INF>3</INF>)<INF>2</INF> (R = Ph, <BO>6a</BO>; R = pyl, <BO>7a</BO>). Under similar conditions, <BO>1a</BO> reacts with 2 equiv of ^tBuNH<INF>2</INF> to produce the amine adduct (Bp^(CF3)2)RuH(^tBuNH<INF>2</INF>)<INF>2</INF> (<BO>8a</BO>). By addition of 1 equiv of MeI to <BO>8a</BO>, the iodo complex (Bp^(CF3)2)RuI(^tBuNH<INF>2</INF>)<INF>2</INF> (<BO>9a</BO>) is isolated and characterized by an X-ray structural determination. The analogous chloro complex (Bp^(CF3)2)RuCl(^tBuNH<INF>2</INF>)<INF>2</INF> (<BO>10a</BO>) can be prepared by stirring a dichloromethane solution of <BO>8a </BO>for 18 h. In the absence of dihydrogen, <BO>1a</BO> reacts with a large excess of ^tBuNH<INF>2</INF> to give (Bp^(CF3)2)RuH(COD)(^tBuNH<INF>2</INF>) (<BO>11a</BO>). The structure with a κ² 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 <BO>8a</BO>, we could not isolate any complex. However upon N<INF>2</INF> atmosphere, the dinuclear species with a μ²-bridging dinitrogen ligand [(Bp^(CF3)2)RuH(ⁱPr<INF>2</INF>NH)]<INF>2</INF>(N<INF>2</INF>) (<BO>12a</BO>) could be isolated and characterized by a single-crystal X-ray determination. Addition of mesitylene to <BO>1a</BO> produces the arene complex (Bp^(CF3)2)RuH(η⁶-C<INF>6</INF>H<INF>3</INF>Me<INF>3</INF>) (<BO>13a</BO>). The X-ray structure determination gave conclusive evidence for the κ² N,N bonding mode of the Bp^(CF3)2 ligand. When exposing <BO>1a</BO> to a CO atmosphere, the new acyl(dicarbonyl) complex (Bp^(CF3)2)Ru(COC<INF>8</INF>H<INF>13</INF>)(CO)<INF>2</INF> (<BO>14a</BO>) 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) (<BO>1b</BO>) as starting material. The analogous complexes <BO>2b</BO>,<BO> 4b</BO>−<BO>6b</BO>, and<BO> 14b</BO> 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.