Synthesis and Reactivity of Ru(PPh₃)₃(CO)HF and the N-Heterocyclic Carbene Derivatives Ru(NHC)(PPh₃)₂(CO)HF

Abstract

The reaction of Ru(PPh 3 ) 3 (CO)H 2 with excess Et 3 N‚3HF at elevated temperature affords the hydride fluoride complex Ru(PPh 3 ) 3 (CO)HF (1). This reacts with a series of N-heterocyclic carbenes (NHCs) at ambient temperature to form the mono-NHC products Ru(NHC)(PPh 3 ) 2 (CO)HF (NHC ) IMe 4 (2), IEt 2 -Me 2 (3), ICy (4), I i Pr 2 Me 2 (5)). Complexes 2-4 convert from the trans-to cis-phosphine isomers in solution over weeks (relative rates 2 > 3 . 4), while 5 undergoes both isomerization and disproportionation to yield cis-Ru(I i Pr 2 Me 2 )(PPh 3 ) 2 (CO)HF ( 6), 1, and Ru(I i Pr 2 Me 2 ) 2 (PPh 3 )(CO)HF ( 7) in a matter of hours. The molecular structures of compounds 1-4 have been determined by X-ray crystallography.

Synthesis and Reactivity of Ru(NHC)(dppp)(CO)H2 and Ru(NHC)(dppp)(CO)HF Complexes: C–H and C–F Activation

“…The compound displayed a distorted-octahedral geometry with the two, trans-phosphanes being tilted towards the hydrido ligand [P(1)-Ru(1)-P(3) 168.09(3)°; P(4)-Ru(2)-P(5) 171.20(3)°]. [12,13] The Ru-F bond lengths for the two molecules in the unit cell [2.1005(18), 2.0943(18) Å] are comparable to other hydrido fluorido Ru complexes in the literature [14,15] and in fact identical to the Ru-F distance in [Ru(PPh 3 ) 3 (CO)HF] [9] (unsurprisingly given that in both cases the π-donor fluorido ligand is trans to the π-acceptor CO group).…”

“…The spectroscopic properties of 1 were found to be similar to those of [Ru(PPh 3 ) 3 (CO)HF], with a multiplet hydride resonance observed at δ = -4.18 (cf. δ = -5.05 for [Ru(PPh 3 ) 3 -(CO)HF]), [9] which through a combination of broadband and selective 31 P-decoupling experiments yielded coupling constants of 117.1 (trans-J H,P ), 25.0 (cis-J H,P ), 16.9 (cis-J H,P ) and 4.2 Hz (J H,F ). The 31 P{ 1 H} NMR spectrum consisted of an ABX pattern, while the 19 F spectrum showed only a low frequency (δ -381) multiplet for the Ru-F resonance.…”

“…C 6 F 6 , C 6 F 5 H, C 6 F 5 CF 3 , C 6 F 4 HCF 3 , C 5 F 5 N, C 5 F 4 HN and Et 3 SiH were dried with activated molecular sieves (3 Å) and stored under argon. [Ru(PPh 3 ) 3 (CO)HF], [9] [Ru(PPh 3 )(dppp)(CO)H 2 ], [37] [Ru-(IMes)(dppp)(CO)H 2 ] (4), [5] IMes, [38] IEt 2 Me 2 [39] and ICy [40] were prepared via literature methods. NMR spectra were recorded on Bruker Avance 400 and 500 spectrometers at 25°C unless otherwise stated, with 1 H and 13 C chemical shifts referenced to internal solvent references.…”

“…[8] We recently reported that the ruthenium NHC hydrido fluorido species [Ru(NHC)(PPh 3 ) 2 -(CO)HF] [NHC = IMe 4 (1,3,4,5-tetramethylimidazol-2-ylidene), IEt 2 Me 2 (1,3-diethyl-4,5-dimethylimidazol-2-ylidene), IiPr 2 Me 2 (1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) and ICy (1,3-dicyclohexylimidazol-2-ylidene)] could be prepared at room temperature upon substitution of PPh 3 in [Ru(PPh 3 ) 3 (CO)HF] by the free carbenes. [9] All four of the carbene complexes proved to be relatively unstable in solution; [Ru(IMe 4 )(PPh 3 ) 2 3 (CO)HF], within a matter of hours. We reasoned that further studies of hydrido fluorido ruthenium species should incorporate a chelating phosphane ligand in place of the two PPh 3 groups as this should prevent isomerisation/disproportionation, allowing a more detailed investigation of reactivity to be undertaken.…”

Liquid injection field desorption/ionization of transition metal fluoride complexes

“…The following compounds were prepared by literature syntheses: 2,3,5,6-tetrafluoro-4-methoxypyridine [30], 2,3,5,6-tetrafluoro-4-dimethylaminopyridine [30], Ni(PEt 3 ) 2 (C 5 F 4 N)F (3) [2], Ni(PEt 3 ) 2 (C 5 F 3 HN)F (4) [2], Ni(PEt 3 ) 2 (C 6 F 5 )F (5) [2], (Cp * ) 2 TiF 2 (6) [31], Ru(PPh 3 ) 3 (CO)(H)F (8) [32] and Rh(PPh 3 ) 3 F (9) [1].…”