Pyrazole as a Donor Function in Neopentane-Based Tripod Ligands RCH2C(CH2pyrazol-1-yl)3n(CH2PR2)n – Synthesis and Coordination Chemistry

Jacobi, Albrecht; Hüttner, Gottfried; Winterhalter, Ute; Cunskis, Sven

doi:10.1002/(sici)1099-0682(199806)1998:6<675::aid-ejic675>3.3.co;2-d

Cited by 7 publications

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“…Three condensed eight-membered rings of a hypothetical 1:1 complex would exhibit significantly lower stability than the more common five-, six-, or seven-membered rings of tris(pyrazolyl) or tris(phosphine) ligands and, thus, likely is entropically disfavored. Similarly, the tris(pyrazolyl) analogue of the TIME Me ligand, 1,1,1-[tris(pyrazol-1-yl)methyl]ethane, reportedly acts as a bidentate chelator …”

Section: Resultsmentioning

confidence: 99%

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Group 11 Metal Complexes of N-Heterocyclic Carbene Ligands: Nature of the MetalCarbene Bond

et al. 2004

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The silver complex of the tripodal N-heterocyclic carbene ligand TIME Me , [(TIME Me ) 2 Ag 3 ]-(PF 6 ) 3 (3), reacts with copper(I) bromide and (dimethyl sulfide)gold(I) chloride to yield the corresponding D 3 -symmetrical copper(I) and gold(I) complexes [(TIME Me ) 2 Cu 3 ](PF 6 ) 3 (4) and [(TIME Me ) 2 Au 3 ](PF 6 ) 3 (5). Single-crystal X-ray diffraction, spectroscopic, and computational studies of this series of metal NHC complexes are described. The group 11 metal complexes of the TIME Me ligand exhibit isostructural geometries, with three metal ions bridging two of the TIME Me ligands. Each metal ion is linearly coordinated to two carbene centers, with each of the carbenoid carbons stemming from a different ligand. Overall, the molecules possess D 3 symmetry. The electronic structure of these newly synthesized compounds was elucidated with the aid of DFT calculations. In contrast to the common assumption that NHCs are pure σ-donor ligands, our calculations reveal the existence of both σ-and π-type interactions between the metal ions and the carbenoid carbons. A study of the closely related D 2d -symmetrical species Pd(CN 2 Bu t 2 C 2 H 2 ) 2 (6) and the simplified D 2h -symmetrical model complexes M(IM Me C:) 2 (8-10; M ) Ag, Cu, Au) allowed for quantitative comparison of the two different types of bonding interactions. It was found that π-back-bonding interactions in these diaminocarbene model species contribute to approximately 15-30% of the complexes' overall orbital interaction energies.

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Section: Resultsmentioning

confidence: 99%

“…Similarly, the tris(pyrazolyl) analogue of the TIME Me ligand, 1,1,1-[tris(pyrazol-1-yl)methyl]ethane, reportedly acts as a bidentate chelator. 44 DFT Studies. All calculations were carried out using the ADF program suite at the BP86 level with relativistic effects accounted for by ZORA.…”

Section: Resultsmentioning

confidence: 99%

Group 11 Metal Complexes of N-Heterocyclic Carbene Ligands: Nature of the MetalCarbene Bond

et al. 2004

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“…The Mo-N distance is 2.264(2) Å which is significantly shorter than those reported for a closely related compound [Mo(CO) 4 (Ph 2 PC 6 H 4 NH 2 )], 2.326(2) Å, and other molybdenum tetracarbonyl complexes of P-N ligands. 14, 15 The Mo-C distances for the carbonyls trans to the phosphorus and nitrogen are 1.997(3) and 1.945(3) Å respectively. The significant shortening of the Mo-C (CO) bond trans to the imidazolyl nitrogen donor reflects the higher donor : Table 2 Selected bond lengths (Å) and angles (Њ) for compound 1 acceptor ratio of the nitrogen donor relative to a phosphine ligand.…”

Section: Crystallographic Studies Of Complexes 1 Andmentioning

confidence: 99%

A convenient method for selective substitutions at the backbone of a co-ordinated imidazolylphosphine P–N ligand. Single crystal X-ray analyses of [Mo(CO)4(MeImCH2PPh2)] and its ethyl substituted derivative [Mo(CO)4(MeImCHEtPPh2)] †

Jalil¹,

Fujinami²,

Nishikawa³

1999

J. Chem. Soc., Dalton Trans.

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The complex [Mo(CO) 4 (PN)] 1 was synthesized by refluxing [Mo(CO) 6 ], with 2-(diphenylphosphinomethyl)-1methylimidazole (PN) in ethanol in the presence of NaBH 4 . The co-ordinated PN is selectively deprotonated to afford a carbanion [Mo(CO) 4 (MeImCHPPh 2 )] Ϫ 1a when 1 is treated with strong bases such as methyllithium or n-butyllithium at room temperature. The carbanion 1a readily reacted with deuterium oxide, methyl iodide, ethyl iodide, allyl bromide, and trimethylsilyl chloride to give [Mo(CO) 4 (MeImCHRPPh 2 )] (R = D 2, Me 3, Et 4, CH 2 ᎐ ᎐ CHCH 2 5 or SiMe 3 6). Treatment of 1a with chlorodiphenylphosphine and benzoyl chloride gave the corresponding derivatives [Mo(CO) 4 {MeImCH(PPh 2 ) 2 }]ؒ0.5H 2 O 7 and [Mo(CO) 4 {MeImCH(COPh)PPh 2 }]ؒH 2 O 8 respectively, both containing an additional free donor site. However, slow addition of acetyl chloride to a tetrahydrofuran solution of 1a gave the O-acetyl enolate derivative [Mo(CO) 4 {MeImC᎐ ᎐ CMe(OCOMe)PPh 2 }]ؒ0.5H 2 O 9 instead of an acetyl derivative. The 1 H and 31 P NMR spectra indicated the presence of two geometric isomers (Z and E) for complex 9. All of these complexes were fully characterized by IR, 1 H and 31 P NMR. The molecular structures of complex 1 and its ethyl substituted derivative 4 have also been studied by single crystal X-ray analyses.

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“…Much of our research has focused on the synthesis and coordination chemistry of tridentate percarbene ligands anchored to either a single atom such as boron, carbon, and nitrogen or a trifunctionalized arene moiety . We present here an unprecedented tripodal N-heterocyclic carbene ligand system with a carbon anchor and important silver precursors that give access to synthetic routes for the isolation of a new generation of potentially catalytically active metal−carbene complexes.…”

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confidence: 99%

Silver Complexes of a Novel Tripodal N-Heterocyclic Carbene Ligand: Evidence for Significant Metal−Carbene π-Interaction

et al. 2003

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Pyrazole as a Donor Function in Neopentane-Based Tripod Ligands RCH2C(CH2pyrazol-1-yl)3n(CH2PR2)n – Synthesis and Coordination Chemistry

Cited by 7 publications

References 0 publications

Group 11 Metal Complexes of N-Heterocyclic Carbene Ligands: Nature of the MetalCarbene Bond

Group 11 Metal Complexes of N-Heterocyclic Carbene Ligands: Nature of the MetalCarbene Bond

A convenient method for selective substitutions at the backbone of a co-ordinated imidazolylphosphine P–N ligand. Single crystal X-ray analyses of [Mo(CO)4(MeImCH2PPh2)] and its ethyl substituted derivative [Mo(CO)4(MeImCHEtPPh2)] †

Silver Complexes of a Novel Tripodal N-Heterocyclic Carbene Ligand: Evidence for Significant Metal−Carbene π-Interaction

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