Abstract:The chemistry of the ligand (R 2 PCH 2 SiMe 2 ) 2 N À (R ¼ cyclohexyl and t Bu), '' PNP-R '', on ruthenium is developed, including RuH(PNP-Cy)(PPh 3 ) and (HPNP-R)RuH 3 Cl. The latter contains a protonated nitrogen (i.e., amine as a donor to Ru) and one H 2 ligand (X-ray structure for R ¼ t Bu). This compound can be dehydrohalogenated to give (PNP-Cy)RuH 3 , which undergoes H/D exchange of D 2 into its cyclohexyl rings, and is itself dehydrogenated by excess H 2 C=CHR to give [Cy 2 PCH 2 SiMe 2 NSiMe 2 CH 2 PC… Show more
“…The yield was quantitative by NMR spectroscopy. On standing in solution rapid H/D exchange between the hydride resonance and C 6 D 6 occured, fully consistent with that seen previously for PNP Cy Ru(H) 3 . On use of D 2 , a 1:1:1 triplet for CH 3 D was observed at 0.14 ppm ( J H - D 2.7 Hz).…”
Section: Methodssupporting
confidence: 88%
“…The addition of an excess of H 2 to 1 ultimately produces one new diamagnetic product and methane (confirmed by the observation of CH 3 D with the use of D 2 ). The diamagnetic product ( 31 P{ 1 H} at 84.8 ppm) possesses C 2 v symmetry and has an intensity 3 hydride resonance as a triplet centered at −15.1 ppm ( 2 J P - H = 14 Hz); this is assigned as the polyhydride PNPRu(H) 3 , 5 , on the basis of the close spectroscopic similarity and analogous reactivity to previously synthesized PNP Cy Ru(H) 3 (PNP Cy = (Cy 2 PCH 2 SiMe 2 ) 2 N) . The product from the reaction of 1 and D 2 produces an identical NMR apart from the complete lack of any hydride resonance, confirming all hydrides in 5 originate from dihydrogen.…”
The reaction of PNPRuCl (PNP = (tBu2PCH2SiMe2)2N-) with excess MeLi at −78 °C, followed by
addition of a one-electron oxidant, leads to the thermally stable (at 25 °C), low-spin, five-coordinate
trivalent ruthenium complex PNPRuMe2, 1. For comparison PNPRuI2, 2, was also synthesized and shown
equally to be a low-spin d5 complex. Compound 1 reacts with NO to produce the diamagnetic ruthenium(II)
complex PNPRuMe2(NO), 3, with H2 to give PNPRu(H)3, 5, and with excess CO to produce PNPRu(COMe)CO, 6. The unusual stability of 1 is suggested to arise from the steric encapsulation of the radical
center provided by the extremely bulky pincer ligand, the low coordination number (5), and a non-redox-innocent amide functionality.
“…The yield was quantitative by NMR spectroscopy. On standing in solution rapid H/D exchange between the hydride resonance and C 6 D 6 occured, fully consistent with that seen previously for PNP Cy Ru(H) 3 . On use of D 2 , a 1:1:1 triplet for CH 3 D was observed at 0.14 ppm ( J H - D 2.7 Hz).…”
Section: Methodssupporting
confidence: 88%
“…The addition of an excess of H 2 to 1 ultimately produces one new diamagnetic product and methane (confirmed by the observation of CH 3 D with the use of D 2 ). The diamagnetic product ( 31 P{ 1 H} at 84.8 ppm) possesses C 2 v symmetry and has an intensity 3 hydride resonance as a triplet centered at −15.1 ppm ( 2 J P - H = 14 Hz); this is assigned as the polyhydride PNPRu(H) 3 , 5 , on the basis of the close spectroscopic similarity and analogous reactivity to previously synthesized PNP Cy Ru(H) 3 (PNP Cy = (Cy 2 PCH 2 SiMe 2 ) 2 N) . The product from the reaction of 1 and D 2 produces an identical NMR apart from the complete lack of any hydride resonance, confirming all hydrides in 5 originate from dihydrogen.…”
The reaction of PNPRuCl (PNP = (tBu2PCH2SiMe2)2N-) with excess MeLi at −78 °C, followed by
addition of a one-electron oxidant, leads to the thermally stable (at 25 °C), low-spin, five-coordinate
trivalent ruthenium complex PNPRuMe2, 1. For comparison PNPRuI2, 2, was also synthesized and shown
equally to be a low-spin d5 complex. Compound 1 reacts with NO to produce the diamagnetic ruthenium(II)
complex PNPRuMe2(NO), 3, with H2 to give PNPRu(H)3, 5, and with excess CO to produce PNPRu(COMe)CO, 6. The unusual stability of 1 is suggested to arise from the steric encapsulation of the radical
center provided by the extremely bulky pincer ligand, the low coordination number (5), and a non-redox-innocent amide functionality.
“…DFT calculations suggest an square pyramidal geometry for this compound with the hydride in the apex and the dihydrogen, trans to the N atom, in the base (Chart ). The related compound RuH(η 2 -H 2 ){( t Bu 2 PCH 2 CH 2 ) 2 N} ( 179 ), containing CH 2 instead of SiMe 2 , has been generated by hydrogenation of 62 in the presence of ( t Bu 2 PCH 2 CH 2 ) 2 NH. Under hydrogen atmosphere, complex 179 is in equilibrium with the dihydride-dihydrogen RuH 2 (η 2 -H 2 ){( t Bu 2 PCH 2 CH 2 ) 2 NH} ( 180 ), resulting from the addition of H 2 along the Ru–N bond of 179 .…”
The preparation, structure, dynamic behavior in solution, and reactivity of polyhydride complexes of platinum group metals, described during the last three decades, are contextualized from both organometallic and coordination chemistry points of view. These compounds, which contain dihydrogen, elongated dihydrogen, compressed dihydride, and classical dihydride ligands promote the activation of B-H, C-H, Si-H, N-H, O-H, C-C, C-N, and C-F, among other σ-bonds. In this review, it is shown that, unlike other more mature areas, the chemistry of polyhydrides offers new exciting conceptual challenges and at the same time the possibility of interacting with other fields including the conversion and storage of regenerative energy, organic synthetic chemistry, drug design, and material science. This wide range of possible interactions foresees promising advances in the near future.
“…Such monoanionic PCP ligands have been found to support a number of exciting catalytic and stoichiometric transformations. , Isoelectronic neutral PNP ligands carrying a neutral pyridine donor as the Z group ( B ) have also been used , More recently, several groups, including ours, have been focusing on PNP ligands with a central diarylamido motif ( D ). − 1 …”
Ru complexes of a new neutral PCP pincer ligand containing a central carbene ligand have been prepared (referred to as (P 2 Cd) for emphasis). The ligand precursor P 2 CH 2 can be prepared in good yield in two steps from pyrrole, formaldehyde, and chlorodiisopropylphosphine. The reaction between P 2 CH 2 and [(p-cymene)RuCl 2 ] 2 in the presence of Et 3 N cleanly furnishes (P 2 Cd)RuHCl. The latter possesses a Y-shaped five-coordinate geometry about Ru, as determined in an X-ray diffraction study. Reactions of (P 2 Cd)RuHCl with a series of potential ligands have been examined. Addition of pyridine, MeCN, or ethylene leads to a simple adduct formation and addition of CO leads to coordination of two CO ligands to Ru with concomitant hydride-to-carbene migration, while addition of PMe 3 gives rise to both types of products. (P 2 Cd)RuHCl is a moderately active precatalyst for transfer hydrogenation of ketones. Addition of phenylacetylene leads to the insertion of the triple bond into Ru-H to give (P 2 Cd)Ru(-CPhdCH 2 )-Cl. (P 2 Cd)RuHCl can be converted to (P 2 Cd)RuCl 2 by action of an iminium chloride reagent. (P 2 Cd)RuCl 2 adds one molecule of CO with retention of the carbene moiety, even at elevated temperatures. These results demonstrate the potential of (P 2 Cd) as a robust and electronically distinctive ancillary ligand.
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