Missing link: PCP pincer ligands containing P–N bonds and their Pd complexes

Ozerov, Oleg V.; Guo, Chengyun; Foxman, Bruce M.

doi:10.1016/j.jorganchem.2006.07.018

Cited by 38 publications

(23 citation statements)

References 17 publications

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“…The precipitation of the formed salt promotes the latter reaction. Further addition of the metal source to the reaction mixture leads to regioselective bis ortho ‐cyclometalation affording the corresponding pincer metal complexes with Ni, [ 30–32 ] Pd, [ 33,34 ] Co, [ 35 ] Ir, [ 36,37 ] Fe, [ 38 ] and Ru, [ 39 ] in good to excellent yields. [ 20 ]…”

Section: Poczp‐aryl Pincer Metal Complexesmentioning

confidence: 99%

“…The precipitation of the formed salt promotes the latter reaction. Further addition of the metal source to the reaction mixture leads to regioselective bis ortho-cyclometalation affording the corresponding pincer metal complexes with Ni, [30][31][32] Pd, [33,34] Co, [35] Ir, [36,37] Fe, [38] and Ru, [39] in good to excellent yields. [20] Recently, Morales-Morales et al described an alternative route for the synthesis of POCSP pincer metal complexes, start-EurJIC European Journal of Inorganic Chemistry ing from a disulfide precursor instead of 3-mercaptophenol (Scheme 4).…”

Section: Introductionmentioning

confidence: 99%

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Hybrid POCZP Aryl Pincer Metal Complexes and their Catalytic Applications

et al. 2020

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The use of XCX‐aryl pincer metal complexes as catalysts started immediately after their discovery in 1976. Nowadays pincer metal complexes are commonly used as a new platform for the development and improvement of known and novel catalytic reactions. More recently, pincer metal complexes with hybrid pincer backbones of the type POCZP (Z = CH2, NH or S) have attracted much attention because of their facile preparation and outstanding catalytic performances. For instance, these complexes have been successfully used in cross‐coupling, transfer hydrogenation, and borylation reactions. In many cases, showing enhanced catalytic activities compared with POCOP‐ or PZCZP‐aryl pincer metal analogues. Hence, in this Minireview we summarize the available synthetic routes to produce POCZP aryl pincer ligands and their metal complexes as well as their applications as catalysts in different organic transformations.

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Section: Poczp‐aryl Pincer Metal Complexesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Hybrid POCZP Aryl Pincer Metal Complexes and their Catalytic Applications

et al. 2020

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“…The chemistry of E,C,E‐coordinating (E = donor atom) pincer‐type ligands is of ongoing interest. Since our previous report on the phosphorus‐containing non‐symmetric O,C,S‐coordinating pincer‐type ligand {3‐ t Bu‐5‐[P(S)Ph 2 ]C 6 H 3 }P(O)(O i Pr) 2 a number of novel such pincer‐type ligands have been published and randomly selected examples are shown in Scheme . The classic pincer‐type ligands are based on aromatic backbones to which the donor functions are linked by spacers of different lengths.…”

Section: Introductionmentioning

confidence: 99%

A Novel Ferrocene‐Backboned Unsymmetrical Pincer‐Type Proligand and Its Organotin Derivatives

et al. 2019

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In this contribution we report the synthesis of the novel unsymmetrical ferrocene‐based pincer‐type proligand η5‐CpFeη5‐C5H2‐1‐Br‐2‐PPh2‐5‐CH2NMe2 (1). Its reactivity is demonstrated by isolation of related organotin derivatives η5‐CpFeη5‐C5H2‐1‐SnR3‐2‐PPh2‐5‐CH2NMe2 (3, R = Ph; 4, R = Me). The reactions of compounds 3 and 4 with H2O2 and elemental sulfur gave the corresponding ferrocenylphosphane oxide (5) and the sulfides (6, 7), respectively. Most remarkably, an unprecedented reaction of the organotin derivative 3 with elemental iodine was observed, providing the ammonium salt [η5‐CpFeη5‐C5H2‐1‐SnPh2I‐2‐P(O)Ph2‐5‐CH2NHMe2]I (8). The compounds are characterized by elemental analyses, 1H, 13C, 31P, 119Sn NMR spectroscopy, electrospray ionization mass spectrometry, and single‐crystal X‐ray diffraction analyses (3–8). Also reported are the solid‐state structures of the hydrolysis products [η5‐CpFeη5‐C5H2‐1‐SnPh2(OH)‐2‐P(O)Ph2‐5‐CH2NHMe2]·0.5H2O (9a) and [η5‐CpFeη5‐C5H2‐1‐SnPh(OH)‐2‐P(O)Ph2‐5‐CH2NMe2]2[I3]2 (9b) that were isolated by serendipity.

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“…164 There has also been spectroscopic evidence for transient species formed at elevated temperatures that have been postulated to be cis monomers. 75,169 However, it was highly unlikely that the species observed here was 46 as such structures are rarely formed at room temperature, as they are highly strained due to the formation of a rigid, eight-membered chelate ring. 164 In contrast, there are many examples in the literature of dimeric complexes like 47 forming at room temperature, many of which have been isolated and fully characterised by NMR methods.…”

Section: Platinum(ii) Complexes Of Dpypmxmentioning

confidence: 88%

Late Transition Metal Complexes of Pyridyldiphosphines

Vaughan¹

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<p>This thesis provides an account of research into the properties of pyridyldiphosphines with o-xylene and m-xylene backbones. The coordination behaviour of the o-xylene based ligand with platinum, palladium, silver, rhodium and iridium metal centres has been studied, with an emphasis on whether the presence of the pyridyl rings affects the products formed. Platinum and palladium pincer complexes have been synthesised and the intermediates investigated. The formation of trimetallic complexes with these ligands acting as bridging ligands has also been explored. Two new pyridyldiphosphines, o-C₆H₄(CH₂PPy₂)₂ (3) and m-C₆H₄(CH₂PPy₂)₂ (4), and one known pyridyldiphosphine, PPy₂(CH₂)₃PPy₂ (5), have been synthesised via an improved method. Tris(2-pyridyl)phopshine was reacted with a lithium dispersion to give LiPPy₂, which was then reacted with the appropriate dichloride or dibromide compound to yield the desired ligand. The phosphine selenides of 3 and 4 were synthesised and the ¹J PSe values of 738 and 742 Hz indicated these ligands were less basic than PPh₃. While the ligands themselves were not water-soluble, protonation by a strong acid, such as HCl or H₂C(SO₂CF₃)₃, rendered them soluble in water. A series of [MX₂(PP)] complexes (where M = Pt, X = Cl, I, Me, Et, PP = 3, 5; M = Pd, X = Cl, Me PP = 3, 5) were synthesised. Complexes of 3 displayed dynamic behaviour in solution which was attributed to the backbone of the ligand inverting. When [PtMeCl(PP)] (27) was reacted with NaCH(SO₂CF₃)₂ no evidence for the coordination of the pyridyl nitrogens was observed. The synthesis of a series of unsymetrical [PtMeL(PP)]⁺ complexes enabled the comparison of the cis and trans influences of a range of ligands. The following cis influence series was compiled based on ³¹P NMR data of these complexes: Py ≈ Cl > SEt₂ > PTA > PPh₃. Reaction of 27 with NaCH(SO₂CF₃)₂ and carbon monoxide slowly formed an acyl complex, where the CO had inserted in the Pt–Me bond. The bis-chelated complexes [M(PP)₂] where M = Pt, Pd, and [Ag(PP)₂]⁺ were formed. In these complexes 3 acted as a diphosphine ligand and there was no evidence for any interaction between the pyridyl nitrogen atoms and the metal centre. Reaction of 3 with [Ir(COD)(μ-Cl)]₂ formed [IrCl(PP)(COD)] (42). When the chloride ligand in 42 was abstracted, the pyridyl nitrogens were able to interact with the iridium centre faciliating the isomerisation of the 1,2,5,6-ƞ⁴-COD ligand to a 1-к-4,5,6-ƞ³-C₈H₁₂ ligand. The X-ray crystal structure of [Ir(1-к-4,5,6-ƞ³-C₈H₁₂)(PPN)]BPh₄ (43) confirmed the P,P,N chelation mode of the ligand. In solution, 43 displayed hemilabile behaviour, with the pyridyl nitrogens exchanging at a rate faster than the NMR time scale at room temperature. The coordinated pyridyl nitrogen was able to be displaced by carbon monoxide to form [Ir(1-к-4,5,6-ƞ³-C₈H₁₂)(CO)(PP)]⁺. A series of [PtXY(μ-PP)]₂ complexes, where X = Y = Cl, Me, X = Cl, Y = Me and PP = 4, were formed initially when 4 was reacted with platinum(II) complexes. When heated, the dimers containing methyl ligands eliminated methane to form [PtX(PCP)] pincer complexes, X = Cl (49), Me (51). When the chloride ligand in 49 was abstracted no evidence of pyridyl nitrogen coordination was observed. Protonation of 49 did not yield a water-soluble pincer complex. The [PdCl₂(μ-PP)]₂ complex readily metallated when heated to give the pincer complex [PdCl(PCP)]. Given pyridyl nitrogen atoms are known to be good ligands for “hard” metal centres, the ability of the pyridyl nitrogens in 3 and 4 to coordinate to metal centres was investigated. While complexes with chloride ligands were found to form insoluble products, the synthesis of [(PtMe₂)₃(PP)], from the reaction of either 3 or [PtMe₂(PP)] (17) with dimethyl(hexa-1,5-diene)platinum, proceeded smoothly through a dimetallic intermediate. The same reactivity was observed in the synthesis of [(PtMe₂)₂PtMe(PCP)]. In contrast, the cationic heterotrimetallic complexes [{M(COD)}₂PtMe(PP)]²⁺ and [{M(COD)}₂PtMe(PCP)]²⁺, where M = Rh or Ir, were synthesised without the detection of any intermediates. However, dimetallic complexes were formed as part of a mixture when 17 or 51 was reacted with one equivalent of the appropriate metal complex.</p>

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Missing link: PCP pincer ligands containing P–N bonds and their Pd complexes

Cited by 38 publications

References 17 publications

Hybrid POCZP Aryl Pincer Metal Complexes and their Catalytic Applications

Hybrid POCZP Aryl Pincer Metal Complexes and their Catalytic Applications

A Novel Ferrocene‐Backboned Unsymmetrical Pincer‐Type Proligand and Its Organotin Derivatives

Late Transition Metal Complexes of Pyridyldiphosphines

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