TpRu Hydride and Dihydrogen Complexes Bearing Bidentate Phosphinoamine Ligands. NMR Study of Proton Transfer to [TpRuH(L)] (L = R,R-dippach, dippae; Tp = Hydrotris(pyrazolyl)borate)

Abstract

The diastereomerically pure complexes [TpRuX(R,R-dippach)] (X ) Cl (1a), H (2a); R,Rdippach ) (R,R)-1,2-bis((diisopropylphosphino)amino)cyclohexane) as well as the nonchiral derivatives [TpRuX(dippae)] (X ) Cl (1b), H (2b); dippae ) 1,2-bis((diisopropylphosphino)amino)ethane) have been prepared and characterized. The reaction of either 1a or 1b with H 2 and NaBAr′ 4 (Ar′ ) 3,5-bis(trifluoromethyl)phenyl) in fluorobenzene yields the corre-No significant intramolecular interaction between the amino protons and the hydrogen atoms bound to the metal has been observed in any of these compounds. Both 3a and 3b react readily with dinitrogen, furnishing the complexes [TpRu(N 2 )(R,Rdippach)][BAr′ 4 ] (4a) and [TpRu(N 2 )(dippae)][BAr′ 4 ] (4b). The X-ray crystal structures of 3b and 4b were determined. The proton-transfer processes over the monohydrides 2a and 2b with HBF 4 ‚OEt 2 have been studied by NMR spectroscopy. Dicationic dihydrogen complexes [TpRu(H 2 )(R,R-dippachH)] 2+ (5a) and [TpRu(H 2 )(dippaeH)] 2+ (5b) result from the protonation of 2a and 2b at one of the NH groups of the respective phosphinoamine ligands by an excess (>10 equiv) of HBF 4 . These species undergo slow tautomerization to their monohydride isomers [TpRuH(R,R-dippachH 2 )] 2+ (5a) and [TpRuH(dippaeH 2 )] 2+ (5b). Intermediates having short hydride (T 1 ) min values have been detected in the course of the proton transfer reactions, which possibly involve the formation of dihydrogen-bonded complexes and/or contact ion pairs between the monohydride complex and the proton donor. Finally, the reaction of 2a with less than 1 equiv of HBF 4 at -80 °C generates a hydride species having an extremely short (T 1 ) min value of 0.5 ms at -62 °C and 400 MHz. The causes for this fast relaxation phenomenon are so far unknown.

Synthesis, Reactivity, X‐ray Crystal Structures and Electrochemical Behaviour of Water‐Soluble [Tris(pyrazolyl)borato]ruthenium(II) Complexes of 1,3,5‐Triaza‐7‐phosphaadamantane (PTA)

“…Yield: 262 mg (86 %). C 33 Crystallographic Studies: Data were collected with a Siemens Smart CCD area-detector diffractometer with graphite-monochromated Mo-K α radiation. Absorption correction was carried out using SA-DABS.…”

“…Attempts to prepare this hydride according to the more standard method [33] using NaBH 4 as hydride source failed due to partial boronation of PTA. Similarly, the reaction of 2 with LiHBEt 3 or LiAlH 4 did not afford reproducible results and generally resulted in extensive decomposition.…”

Protonation of transition-metal hydrides: a not so simple process

“…The study was then extended to TpRu hydrides bearing bidentate phosphinoamine ligands (Tp = hydridotris-(pyrazolyl)borate). 29 Scheme 8 Reaction of (C 5 R 5 )Ru(H)(L) with an excess of HBF 4 . 28 quantitative formation of a piperidinium group, the dihydrido part of the molecule being unchanged.…”

Towards a Rational Design of Ruthenium CO2 Hydrogenation Catalysts by Ab Initio Metadynamics

“…[59][60][61][62][63] Figure 7 shows the FES of the H 2 insertion to the cis-monoformate complex (2 to 10) and of the backward reaction, i.e. the formic acid reaction with the cis-dihydride catalyst resulting in the formation of the formate complex and H 2 (10 to 2).…”