Ruthenium hydride complexes with a heteroscorpionate ligand derived from methane: 2-phenoxy-bis(pyrazol-1-yl)methane. The hemilabile role of the ligand in substitution and proton transfer reactions

Abstract The complex [RuH(κ 3 -bpzmPhO)(cod)] ( 1 ) was synthesized by the reaction of [RuH(cod)(NH 2 NMe 2 ) 3 ][BPh 4 ] with the potassium salt of 2-phenoxy-bis(pyrazol-1-yl)methane (bpzmPhOK). This ligand adopts a κ 3 - N , N , O coordination on the metal center that is reminiscent of the situation usually observed in trispyrazolylborate complexes. Complex 1 exists in solution as a mixture of two diastereoisomers that are in equilibrium. The reaction of 1 with different phosphines (PMe 3 , PMe 2 Ph, PMePh 2 and PPh 3 ) has been studied. The reaction product depends not only on the nature of the phosphine but also on the complex:L ratio and the temperature. Diphosphine derivatives of stoichiometries [RuH(κ 1 - O -bpzmPhO)(cod)L 2 ] (L=PMe 3 , PMe 2 Ph) and [RuH(κ 3 -bpzmPhO)L 2 ] (L=PMe 3 , PMe 2 Ph, PMePh 2 , PPh 3 ) were prepared. Similarly, tetraphosphine derivatives of formula [ cis - O , H -RuH(κ 1 - O -bpzmPhO)L 4 ] (L=PMe 3 , PMe 2 Ph) were obtained. The complex with PMe 2 Ph can be transformed into the respective trans isomer by heating the solution. The reaction of 1 with five equivalents of PMe 3 gives rise to a pentaphosphine derivative with complete decoordination of the anionic bpzmPhO ligand. This ligand exhibits hemilabile behavior that involve a reversible coordination of the pyrazole fragments. Proton transfer reactions from HBF 4 to 1 have also been studied both in acetone-d 6 and in methanol-d 4 . In all of these processes the proton is selectively transferred to the oxygen of the bpzmPhO ligand, which remains coordinated through at least the N-donor centers. Three hydride derivatives are formed in these reactions and they differ either in the relative orientation of the ligands or in the coordination of the OH group of the ligand.