Cycloheptatrienyl, alkyl and aryl PCP-pincer complexes: Ligand backbone effects and metal reactivity

Leis, Wolfgang; Mayer, Hermann A.; Kaska, William C.

doi:10.1016/j.ccr.2008.02.002

Cited by 161 publications

(55 citation statements)

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“…R = H (10, 12), COOEt (11,13) Formation of complex 12 was inferred from the 31 P and 1 H NMR spectroscopic data. The 31 Р NMR spectrum exhibits two doublets at δ 158.5 (d, J P,P = 382.5 Hz) and 117.6 (d, J P,P = 382.5 Hz) from two nonequivalent phos phorus atoms.…”

Section: Methodsmentioning

confidence: 99%

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Reactions of iridium bis(phosphinite) pincer complexes with protic acids

et al. 2010

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Iridium pincer complexes [C 6 H 3 2,6 (OPBu t 2 ) 2 ]Ir(H)Cl (10) and [4 EtOOCC 6 H 2 2,6 (OPBu t 2 ) 2 ]Ir(H)Cl (11) react with protic acids undergoing metallation of one of the tert butyl groups to form double cyclometallated products [4 R C 6 H 2 2 (OPBu t 2 ) 6 (OP(Bu t )CMe 2 CH 2 )]IrCl (12, R = H; 13, R = COOEt), which are stable in air. Complex 12 reacts with CO and Bu t NC giving the corresponding 18 electron complexes [C 6 H 3 2 (OP Bu t 2 ) 6 (OP(Bu t )CMe 2 CH 2 )]Ir(L)Cl (14, L = CO; 15, L = CNBu t ). The structure of com pound 14 was established by X ray diffraction analysis.Homogeneous catalytic dehydrogenation of saturated hydrocarbons is one of the most important problems of organometallic chemistry, the solution of which should promote more rational use of hydrocarbon raw materials. 1 At the same time, the solution of this problem will allow one to accomplish functionalization of a wide class of com pounds containing unactivated C-H bonds. 2 Iridium compounds play an important role here. 3 In the field of study of homogeneous catalysts for dehydrogenation, 4 the most prominent results were achieved using complexes of the type A and B (see .Several years ago, we also began our study on dehydro genation of alkanes. We succeded in the development of complexes of the type C containing pincer ligands based on metallocenes (ferrocene and ruthenocene), 9 which ex hibited unprecedent activity in the dehydrogenation of alkanes and at present are the most active catalysts for this reaction.A necessity to compare electronic and steric properties of the pincer ligands obtained by us with analogous prop erties of ligands studied by other researches was the reason for the synthesis and more detailed study of chemical prop erties of complexes of the type B (for example, we de scribed reactions of complex 3 with CO and CNBu t ).In addition, in order to immobilize dehydrogenation catalysts on polymeric (or dendrimeric) supports we in troduced various functional groups (COOR, CONR 2 , CH 2 NR 2 ) into the pincer ligand of complexes of the type B.In the attempt to modify the substituents indicated, it was found that acidic or basic reagents very often react with the iridium atom instead of a functional group to form a mixture of unidentified products. These observations prompted us to more detailed study of the reaction of known 8 iridium bis(phosphinite) complex 10 and its ana logs with various reactive compounds, in particular, with protic acids.

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Section: Methodsmentioning

confidence: 99%

“…11 Currently, we direct our ef forts on the study of specificities in the mechanism of the reaction discovered by us.…”

Section: Methodsmentioning

confidence: 99%

Reactions of iridium bis(phosphinite) pincer complexes with protic acids

et al. 2010

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“…34,36,44 Using the monoanionic quinonate form of the ligand, Heyduk and co-workers synthesized an Fe(III) complex capable of disulfide reductive elimination, where the ligand accepts the two required electrons leaving the metal center's oxidation state unchanged. 34 In contrast, the recently reported 2,2′-(azanediylbis(3-methyl-6,1-phenylene))bis(1,1,1,3,3,3-hexafluoropropan-2-ol) [CF 3 −ONO]H 3 (1) pincer-type ligand features heavily fluorinated alkoxide donors that act as redox insulators, preventing ligand noninnocence (Scheme 1). 31 The combination of these electron-withdrawing features with the central amido donor creates a push−pull electronic effect capable of enhancing the nucleophilicity of W−C multiple bonds.…”

Section: ■ Introductionmentioning

confidence: 98%

Synthesis, Characterization, and Reactivity of Iron(III) Complexes Supported by a Trianionic ONO^3– Pincer Ligand

Pascualini¹,

Russo²,

Quintero³

et al. 2014

Inorg. Chem.

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Synthetic and characterization results of a new family of Fe(III) compounds stabilized by a trianionic [CF3-ONO](3-) pincer-type ligand are reported. The ligand possesses three negatively charged donors constrained to the meridional positions that provide sufficient electron density to stabilize high-valent metal complexes. Using the redox-insulated [CF3-ONO](3-), pentacoordinated square-pyramidal {[CF3-ONO]FeCl2}{LiTHF2}2 (3), dimeric μ-DME{[CF3-ONO]FeDME}2 (4), trigonal bipyramidal [CF3-ONO]Fe(bpy) (5), and octahedral [CF3-ONO]Fe(bpy)H2O (5·H2O) complexes are synthesized. An interesting feature of the [CF3-ONO](3-) pincer-type ligand is its ability to coordinate the metal center in both the more common meridional positions or occupying a face of a trigonal bipyramidal complex. The molecular structure of 3 contains structural features similar to those of a rare square-planar high-spin Fe(II) complex, and the important role of the counterions in stabilizing a square-plane is emphasized. SQUID magnetometry measurements of 3 reveal its high-spin character, and cyclic voltammetry measurements indicate high oxidation state species are unstable. However, all compounds can be reduced, and in particular 5 displays a reversible reduction event at -2255 mV versus ferrocene (Fc(+)/Fc) that can be assigned to either the Fe(I)/Fe(0) couple or 2,2'-bipyridine reduction.

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“…One particular useful subset of multidentate ligands are the pincer-type ligands, used for a variety of applications ranging from sensors to catalysis [1][2][3][4][5]. The stability imparted by these trans-spanning pincer ligands have been shown to be highly effective in preparing tridentate complexes of transition metals, including square-planar, d 8 metal species.…”

Section: Introductionmentioning

confidence: 99%

An unprecedented bonding mode for potassium within a PCP-pincer palladium hydride–K-Selectride® complex

Boro

Duesler

Goldberg

et al. 2008

Inorganic Chemistry Communications

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Cycloheptatrienyl, alkyl and aryl PCP-pincer complexes: Ligand backbone effects and metal reactivity

Cited by 161 publications

References 40 publications

Reactions of iridium bis(phosphinite) pincer complexes with protic acids

Reactions of iridium bis(phosphinite) pincer complexes with protic acids

Synthesis, Characterization, and Reactivity of Iron(III) Complexes Supported by a Trianionic ONO^3– Pincer Ligand

An unprecedented bonding mode for potassium within a PCP-pincer palladium hydride–K-Selectride® complex

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Cycloheptatrienyl, alkyl and aryl PCP-pincer complexes: Ligand backbone effects and metal reactivity

Cited by 161 publications

References 40 publications

Reactions of iridium bis(phosphinite) pincer complexes with protic acids

Reactions of iridium bis(phosphinite) pincer complexes with protic acids

Synthesis, Characterization, and Reactivity of Iron(III) Complexes Supported by a Trianionic ONO3– Pincer Ligand

An unprecedented bonding mode for potassium within a PCP-pincer palladium hydride–K-Selectride® complex

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Product

Resources

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Synthesis, Characterization, and Reactivity of Iron(III) Complexes Supported by a Trianionic ONO^3– Pincer Ligand