Synthesis of some very bulky N,N′-disubstituted amidines and initial studies of their coordination chemistry †

Boeré, René T.; Klassen, Vicki; Wolmershäuser, Gotthelf

doi:10.1039/a805548c

Cited by 115 publications

(172 citation statements)

References 14 publications

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“…The largest lanthanum complex 2-La showed the highest activity. THF seemed to be a better solvent than benzene or toluene for this reaction ( Table 2, entries [10][11][12]. Thus, in the presence of 1 mol % of 2-La, the reaction of Ph 2 PH with iPrN=C=NiPr in THF at 80 8C yielded the corresponding phosphaguanidine 3 a quantitatively within 1 h ( Table 2, entry 13).…”

Section: Resultsmentioning

confidence: 91%

Half‐Sandwich o‐N,N‐Dimethylaminobenzyl Complexes over the Full Size Range of Group 3 and Lanthanide Metals. Synthesis, Structural Characterization, and Catalysis of Phosphine PH Bond Addition to Carbodiimides

Zhang

Nishiura

Mashiko

et al. 2008

Chemistry A European J

103

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The acid-base reactions between the rare-earth metal (Ln) tris(ortho-N,N-dimethylaminobenzyl) complexes [Ln(CH2C(H4NMe2-o)3] with one equivalent of the silylene-linked cyclopentadiene-amine ligand (C5Me4H)SiMe2NH(C6H2Me3-2,4,6) afforded the corresponding half-sandwich aminobenzyl complexes [{Me2Si(C5Me4)(NC6H2Me3-2,4,6)}Ln(CH2C6H4NMe2-o)(thf)] (2-Ln) (Ln=Y, La, Pr, Nd, Sm, Gd, Lu) in 60-87 % isolated yields. The one-pot reaction between ScCl(3) and [Me2Si(C5Me4)(NC6H2Me3-2,4,6)]Li2 followed by reaction with LiCH2C6H4NMe2-o in THF gave the scandium analogue [{Me2Si(C5Me4)(NC6H2Me3-2,4,6)}Sc(CH2C6H4NMe2-o)] (2-Sc) in 67 % isolated yield. 2-Sc could not be prepared by the acid-base reaction between [Sc(CH2C6H4NMe2-o)3] and (C5Me4H)SiMe2NH(C6H2Me3-2,4,6). These half-sandwich rare-earth metal aminobenzyl complexes can serve as efficient catalyst precursors for the catalytic addition of various phosphine P--H bonds to carbodiimides to form a series of phosphaguanidine derivatives with excellent tolerability to aromatic carbon-halogen bonds. A significant increase in the catalytic activity was observed, as a result of an increase in the metal size with a general trend of La>Pr, Nd>Sm>Gd>Lu>Sc. The reaction of 2-La with 1 equiv of Ph2PH yielded the corresponding phosphide complex [{Me2Si(C5Me4)(NC6H2Me3-2,4,6)}La(PPh2)(thf)2] (4), which, on recrystallization from benzene, gave the dimeric analogue [{Me2Si(C5Me4)(NC6H2Me3-2,4,6)}La(PPh2)]2 (5). Addition of 4 or 5 to iPrN=C=NiPr in THF yielded the phosphaguanidinate complex [{Me2Si(C5Me4)(NC6H2Me3-2,4,6)}La{iPrNC(PPh2)NiPr}(thf)] (6), which, on recrystallization from ether, afforded the ether-coordinated structurally characterizable analogue [{Me2Si(C5Me4)(NC6H2Me3-2,4,6)}La{iPrNC(PPh2)NiPr}(OEt2)] (7). The reaction of 6 or 7 with Ph2PH in THF yielded 4 and the phosphaguanidine iPrN=C(PPh2)NHiPr (3a). These results suggest that the catalytic formation of a phosphaguanidine compound proceeds through the nucleophilic addition of a phosphide species, which is formed by the acid-base reaction between a rare-earth metal o-dimethylaminobenzyl bond and a phosphine P--H bond, to a carbodiimide, followed by the protonolysis of the resultant phosphaguanidinate species by a phosphine P--H bond. Almost all of the rare earth complexes reported this paper were structurally characterized by X-ray diffraction studies.

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Section: Resultsmentioning

confidence: 91%

Half‐Sandwich o‐N,N‐Dimethylaminobenzyl Complexes over the Full Size Range of Group 3 and Lanthanide Metals. Synthesis, Structural Characterization, and Catalysis of Phosphine PH Bond Addition to Carbodiimides

Zhang

Nishiura

Mashiko

et al. 2008

Chemistry A European J

103

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“…In other work [11b] we found that iminoyl chlorides 1 [17] are very convenient and useful electrophilic reagents which react quantitatively with N-H nucleophiles. They also convert imidazole and benzimidazole to the corresponding Niminoyl heterocycles 2a and 2b in very good yield.…”

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confidence: 99%

[1,2]‐Rearrangement of Imino‐N‐heterocyclic Carbenes − Synthesis and Structures of Chelating Iminoimidazole Pd and Ni Complexes

et al. 2004

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Imidazolium and benzimidazolium salts with an N-iminoyl and an NЈ-alkyl group are potential precursors for new bidentate [N,C] ligands which are of interest as novel steering ligands for applications of their metal complexes in homogeneous catalysis. Deprotonation of these azolium salts with potassium hydride does indeed occur, however, the initially formed imino-N-heterocyclic carbenes rearrange spontaneously under migration of the N-iminoyl group from the nitrogen to the former carbene carbon with the formation of 2-iminoyl(benz)imidazoles. These rearranged compounds are

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“…Interestingly, although not unprecedented for guanidines or amidines, [13] the crystal structure of uncoordinated hppH reveals the presence of dimers that interact strongly through NH···N contacts, which results in a disorder of the NH atoms over two positions and a delocalised binding situation. [14] As a consequence, the C1-N1 and C1-N2 bond lengths (see Scheme 2 for the atom numbering) in crystalline hppH are almost equal (133.1 and 132.8 pm), whereas C1-N3 is significantly longer (136.7 pm).…”

Section: Cis-[(nhmentioning

confidence: 97%

“…13 [24] (71 mg, 0.168 mmol) and hppH (72 mg, 0.518 mmol) were dissolved in 15 mL of CH 2 Cl 2 . The resulting pale-yellow solution was stirred at room temperature for 20 h. The solvent was then removed in vacuo, and the pale-yellow oily residue was washed two or three times with toluene and filtered through a 1-cm silica frit.…”

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confidence: 99%

Synthesis and Structural Characterisation of cis‐ and trans‐[(hppH)₂PtCl₂], [(hppH)₃PtCl]⁺Cl^– and Some New Salts of the [hppH₂]⁺ Cation (hppH = 1,3,4,6,7,8‐Hexahydro‐2H‐pyrimido[1,2‐a]pyrimidine): The Importance of Hydrogen Bonding

et al. 2008

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The reaction between the guanidine derivative hppH (hppH = 1,3,4,6,7,8‐hexahydro‐2H‐pyrimido[1,2‐a]pyrimidine) and K2PtCl4 in H2O affords the salt [hppH2]2[PtCl4], which reacts further with Li(hpp) in thf to give cis‐[(hppH)2PtCl2]. The corresponding trans isomer is obtained from the reaction between [(dmso)2PtCl2] and hppH. hppH easily replaces another chlorido ligand to give [(hppH)3PtCl]+Cl–. [hppH2]Cl is formed as a hygroscopic side‐product in the synthesis of [(hppH)2PtCl2] and takes up 1 equiv. of H2O to give [hppH2]Cl·H2O. We report the crystal structures of cis‐ and trans‐[(hppH)2PtCl2], [(hppH)3PtCl]+Cl– and some salts of the [hppH2]+ cation, namely [hppH2]2[PtCl4] and the Pt‐free salts [hppH2][BPh4], [hppH2]Cl and [hppH2]Cl·H2O, which have an increasing degree of directed intermolecular hydrogen contacts. The crystal structure of [hppH2]Cl·H2O features helical chains of Cl–·H2O connected via [hppH2]+ cations. The effects of hydrogen bonding on the structures of these compounds in the solid state are discussed. Finally, quantum chemical calculations provide further insight into the structures and properties of some of these compounds. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

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Synthesis of some very bulky N,N′-disubstituted amidines and initial studies of their coordination chemistry †

Cited by 115 publications

References 14 publications

Half‐Sandwich o‐N,N‐Dimethylaminobenzyl Complexes over the Full Size Range of Group 3 and Lanthanide Metals. Synthesis, Structural Characterization, and Catalysis of Phosphine PH Bond Addition to Carbodiimides

Half‐Sandwich o‐N,N‐Dimethylaminobenzyl Complexes over the Full Size Range of Group 3 and Lanthanide Metals. Synthesis, Structural Characterization, and Catalysis of Phosphine PH Bond Addition to Carbodiimides

[1,2]‐Rearrangement of Imino‐N‐heterocyclic Carbenes − Synthesis and Structures of Chelating Iminoimidazole Pd and Ni Complexes

Synthesis and Structural Characterisation of cis‐ and trans‐[(hppH)₂PtCl₂], [(hppH)₃PtCl]⁺Cl^– and Some New Salts of the [hppH₂]⁺ Cation (hppH = 1,3,4,6,7,8‐Hexahydro‐2H‐pyrimido[1,2‐a]pyrimidine): The Importance of Hydrogen Bonding

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Synthesis of some very bulky N,N′-disubstituted amidines and initial studies of their coordination chemistry †

Cited by 115 publications

References 14 publications

Half‐Sandwich o‐N,N‐Dimethylaminobenzyl Complexes over the Full Size Range of Group 3 and Lanthanide Metals. Synthesis, Structural Characterization, and Catalysis of Phosphine PH Bond Addition to Carbodiimides

Half‐Sandwich o‐N,N‐Dimethylaminobenzyl Complexes over the Full Size Range of Group 3 and Lanthanide Metals. Synthesis, Structural Characterization, and Catalysis of Phosphine PH Bond Addition to Carbodiimides

[1,2]‐Rearrangement of Imino‐N‐heterocyclic Carbenes − Synthesis and Structures of Chelating Iminoimidazole Pd and Ni Complexes

Synthesis and Structural Characterisation of cis‐ and trans‐[(hppH)2PtCl2], [(hppH)3­PtCl]+Cl– and Some New Salts of the [hppH2]+ Cation (hppH = 1,3,4,6,7,8‐Hexahydro‐2H‐pyrimido[1,2‐a]pyrimidine): The Importance of Hydrogen Bonding

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Synthesis and Structural Characterisation of cis‐ and trans‐[(hppH)₂PtCl₂], [(hppH)₃PtCl]⁺Cl^– and Some New Salts of the [hppH₂]⁺ Cation (hppH = 1,3,4,6,7,8‐Hexahydro‐2H‐pyrimido[1,2‐a]pyrimidine): The Importance of Hydrogen Bonding