Basicities of Transition Metal Complexes from Studies of Their Heats of Protonation: A Guide to Complex Reactivity

Angelici, Robert J.

doi:10.1021/ar00050a001

Cited by 145 publications

(143 citation statements)

References 57 publications

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“…Electronic effects will also be different to those observed in complexes of simple phosphines; the distortion caused by chelate formation increases the basicity of the metal centre, 10 this effect increasing as the size of the chelate ring decreases. Since iridium complexes of the most basic phosphines are of limited value, 11 it was expected that the best results would be obtained using complexes with bis(phosphines) of moderate basicity.…”

Section: Exchange Using Complexesmentioning

confidence: 90%

An improved bidentate complex of iridium as a catalyst for hydrogen isotope exchange

Herbert

Kohler

McNeill

2005

J Label Compd Radiopharm

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SummaryIridium(I) complexes 1, containing bidentate phosphines, and 3, with arsine ligands, are generated in situ. These species mediate hydrogen isotope exchange in a variety of aromatic substrates including benzyl ketones. Although the catalytic activities of complexes 1 and 3 are generally unexceptional, a logical step leads to the use of [ethylene-1,2-bis(diphenylarsine)](cyclooctadiene)iridium(I) tetrafluoroborate (5), which is an efficient catalyst for both aryl and benzyl ketones, and mediates exchange to a substantial extent in other substrates also.

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Section: Exchange Using Complexesmentioning

confidence: 90%

An improved bidentate complex of iridium as a catalyst for hydrogen isotope exchange

Herbert

Kohler

McNeill

2005

J Label Compd Radiopharm

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“…For related aspects see refs. [215,216]. 24 21 Positive Mulliken-population charges on carbon in CO are typically obtained with commonly available software.…”

Section: A-3 Ionic Approximation Against Brønsted-lowry Aciditymentioning

confidence: 99%

“…However, TMs by virtue of their incompletely filled d-orbitals are inherently ambivalent and can act also as electron donors, especially late TMs of low-OS that are electron-rich. The concept of TM basicity has long been recognized [216,305,306], and indeed it is of crucial importance in several important organometallic reactions, such as oxidative addition [307] and C-H activation [308,309]. The ability of a TM to donate electrons manifests itself in the classical back-bonding to typical π-acid ligands, but this secondary bonding component is, by convention, ignored under OS assignment.…”

Section: Appendix A: Ionic-approximation Criteria Not Suited For Osmentioning

confidence: 99%

Toward a comprehensive definition of oxidation state (IUPAC Technical Report)

Karen

McArdle

Takats

2014

Pure and Applied Chemistry

111

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A generic definition of oxidation state (OS) is formulated: "The OS of a bonded atom equals its charge after ionic approximation". In the ionic approximation, the atom that contributes more to the bonding molecular orbital (MO) becomes negative. This sign can also be estimated by comparing Allen electronegativities of the two bonded atoms, but this simplification carries an exception when the more electronegative atom is bonded as a Lewis acid. Two principal algorithms are outlined for OS determination of an atom in a compound; one based on composition, the other on topology. Both provide the same generic OS because both the ionic approximation and structural formula obey rules of stable electron configurations. A sufficiently simple empirical formula yields OS via the algorithm of direct ionic approximation (DIA) by these rules. The topological algorithm works on a Lewis formula (for a molecule) or a bond graph (for an extended solid) and has two variants. One assigns bonding electrons to more electronegative bond partners, the other sums an atom's formal charge with bond orders (or bond valences) of sign defined by the ionic approximation of each particular bond at the atom. A glossary of terms and auxiliary rules needed for determination of OS are provided, illustrated with examples, and the origins of ambiguous OS values are pointed out. An electrochemical OS is suggested with a nominal value equal to the average OS for atoms of the same element in a moiety that is charged or otherwise electrochemically relevant.

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“…9(8) 108.3(4) 109.1(4) C(17)-C(18)-C(19) 121.7 (13) 114 (1) 112.6(5) 113.0(5) Fe(2)-C (18)-C(19) 71. 3(6) 66.8(7) 67.1(3) 68.3(3) Fe(2)-C(19)-C (1) 71.6(7) 73.5(3) 71.6(3) Fe(2)-C(19)-C (18) 68.7(6) 72.6(7) 73.0(3) 71.9(3) Fe(2)-C(13)-C (12) 101. 6(8) 109.1(3) 98.1(3) Fe(1)-C(1)-C (2) 132.7(7) 129.5(9) 128.8(4) 128.9(3) Fe (2) (11) 125 (1) 126.0(6) 122.5(5) C(15)-C(16)-C(17) 129.7 (11) 124 (1) 124.…”

Section: Methodsmentioning

confidence: 99%

“…[9] The bridging COT ligand in these bridging alkoxycarbene complexes participates in a novel two-electron, three-center Fe-CFe interaction, similar to that in the starting material [Fe 2 (CO) 5 (h It is well known that nucleophiles such as amines attack a carbon atom of coordinated alkenes in transition-metal complexes if the metal is sufficiently electropositive to promote such an attack. [11] While the COT ligand in [Fe 2 {m-C(OC 2 H 5 )Ar}(CO) 4 (h 8 -C 8 H 8 )] is not sufficiently electropositive to undergo attack by nucleophiles, we thought that protonation [12] of the iron centers would make such an attack possible. Thus, we studied the reaction of diiron-bridging alkoxycarbene complexes with acids such as HBF 4 , but instead of the proton-addition product they gave highly electrophilic, cationic, bridging carbyne complexes [Fe 2 (mCAr)(h 8 -C 8 H 8 )(CO) 4 ]BF 4 , the COT ligand of which are activated towards attack by nucleophiles.…”

Section: Introductionmentioning

confidence: 99%

Remarkable Reactions of Cyclooctatetraene Diiron‐Bridging Carbyne Complexes with Amino and Amido Compounds: Nucleophilic Addition to and Breaking of the Cyclooctatetraene Ring

Zhang

Sun

et al. 2003

Chemistry A European J

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The reactions of the cationic, diiron-bridging carbyne complexes [Fe(2)(mu-CAr)(CO)(4)(eta(8)-C(8)H(8))]BF(4) (1, Ar=C(6)H(5); 2, Ar=p-CH(3)C(6)H(4); 3, Ar=p-CF(3)C(6)H(4)) with LiN(C(6)H(5))(2) in THF at low temperature gave novel N-nucleophilic-addition products, namely, the neutral, diiron-bridging carbyne complexes [Fe(2)(mu-CAr)(CO)(4)(eta(7)-C(8)H(8)N(C(6)H(5))(2))] (4, Ar=C(6)H(5); 5, Ar=p-CH(3)C(6)H(4); 6, Ar=p-CF(3)C(6)H(4))). Cationic bridging carbyne complexes 1-3 react with (C(2)H(5))(2)NH, (iC(3)H(7))(2)NH, and (C(6)H(11))(2)NH under the same conditions with ring cleavage of the COT ligand to produce the novel diiron-bridging carbene inner salts [Fe(2)[mu-C(Ar)C(8)H(8)NR(2)](CO)(4)] (7, Ar=C(6)H(5), R=C(2)H(5); 8, Ar=p-CH(3)C(6)H(4), R=C(2)H(5); 9, Ar=p-CF(3)C(6)H(4), R=C(2)H(5); 10, Ar=C(6)H(5), R=iC(3)H(7); 11, Ar=p-CH(3)C(6)H(4), R=iC(3)H(7); 12, Ar=p-CF(3)C(6)H(4), R=iC(3)H(7); 13, Ar=C(6)H(5), R=C(6)H(11); 14, Ar=p-CH(3)C(6)H(4), R=C(6)H(11), 15, Ar=p-CF(3)C(6)H(4), R=C(6)H(11)). Piperidine reacts similarly with cationic carbyne complex 3 to afford the corresponding bridging carbene inner salt [Fe(2)[mu-C(Ar)C(8)H(8)N(CH(2))(5)](CO)(4)] (16). Compound 9 was transformed into a new diiron-bridging carbene inner salt 17, the trans isomer of 9, by heating in benzene. Unexpectedly, the reaction of C(6)H(5)NH(2) with 2 gave a novel COT iron-carbene complex [Fe(2)[=C(C(6)H(4)CH(3)-p)NHC(6)H(5)](mu-CO)(CO)(3)(eta(8)-C(8)H(8))] (18). However, the analogous reactions of 2-naphthylamine with 2 and of p-CF(3)C(6)H(4)NH(2) with 3 produce novel chelated iron-carbene complexes [Fe(2)[=C(C(6)H(4)CH(3)-p)NC(10)H(7)](CO)(4)(eta(2):eta(3):eta(2)-C(8)H(9))] (19) and [Fe(2)[=C(C(6)H(4)CF(3)-p)NC(6)H(4)CF(3)-p](CO)(4)(eta(2):eta(3):eta(2)-C(8)H(9))] (20), respectively. Compound 18 can also be transformed into the analogous chelated iron-carbene complex [Fe(2)[=C(C(6)H(4)CH(3)-p)NC(6)H(5)](CO)(4)(eta(2):eta(3):eta(2)-C(8)H(9))] (21). The structures of complexes 6, 9, 15, 17, 18, and 21 have been established by X-ray diffraction studies.

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Basicities of Transition Metal Complexes from Studies of Their Heats of Protonation: A Guide to Complex Reactivity

Cited by 145 publications

References 57 publications

An improved bidentate complex of iridium as a catalyst for hydrogen isotope exchange

An improved bidentate complex of iridium as a catalyst for hydrogen isotope exchange

Toward a comprehensive definition of oxidation state (IUPAC Technical Report)

Remarkable Reactions of Cyclooctatetraene Diiron‐Bridging Carbyne Complexes with Amino and Amido Compounds: Nucleophilic Addition to and Breaking of the Cyclooctatetraene Ring

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