- Cationic Group 4 Complexes (M = Ti, Zr, Hf): Modifications and Limitations in the Design of Tridentate Cp,O,P-Ligand Frameworks Built Directly in the Coordination Sphere of the Metal
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The reactions of monopentafulvene complexes Ti1, Zr1, and Hf1 with bidentate O,P-ligand precursors L1–L3 to form the corresponding cationic complexes employing an established three-step synthetic protocol [insertion, methylation, activation with B(C6F5)3] are investigated. Ligands L1–L3 are designed to have different sized spacers between the carbonyl and diphenylphosphine functional groups. The attempts to react Ti1, Zr1, and Hf1 with acetyldiphenylphosphine (L1) proved to yield undesired products at various steps in the synthetic sequence. When Ti1 is used, Ti2 is formed and diphenylphosphine is released at the same time. Compound Ti2, with the exocyclic double bond, is the formal product of insertion of the smallest ketene (H2C=C=O) into the Ti–Cexo bond. Starting with Zr1 results in isolation of the insertion product Zr2 without loss of diphenylphosphine, but a byproduct is formed during the reaction with L1. Subsequent methylation with methyllithium yields a complex reaction mixture. Hf1 reacts cleanly with L1 to the insertion product Hf2. Also, the methylation reaction selectively yields Hf3 as the result of chloride/methyl exchange, but final activation with B(C6F5)3 causes decomposition and release of diphenylphosphine. The use of the ligand precursors L2 and L3 with two methylene groups or an aryl group as linkers between the functional groups selectively provides the desired cationic complexes Ti6, Zr6, Hf6, and Ti9 in good to excellent overall yields.
- Fischer, Malte,Jaugstetter, Maximilian,Schaper, Raoul,Schmidtmann, Marc,Beckhaus, Rüdiger
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supporting information
p. 5146 - 5159
(2018/11/23)
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- Highly chemoselective and versatile method for direct conversion of carboxylic acids to ketones utilizing zinc Ate complexes
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Various carboxylic acids were directly transformed into the corresponding ketones by utilizing organozinc ate complexes, which provide high chemoselectivity without any overreaction to the undesired tertiary carbinol, owing to formation of a stable tetrahedral zincioketal intermediate. This method offers good overall atom/step/pot economy and operational simplicity. No need to overreact: Various carboxylic acids were directly transformed to the corresponding ketones by utilizing organozinc ate complexes, which provide high chemoselectivity without any overreaction to undesired tertiary carbinol, owing to formation of a stable tetrahedral zincioketal intermediate. This method offers good overall atom/step/pot economy and operational simplicity.
- Murata, Ryo,Hirano, Keiichi,Uchiyama, Masanobu
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supporting information
p. 1286 - 1290
(2015/06/08)
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- Variable coordination behaviour of pyrazole-containing N,P and N,P(O) ligands towards palladium(ii)
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Three bidentate, mixed-donor ligands based on a triphenylphosphine unit bearing a pyrazole group in the ortho-position of one phenyl ring have been synthesised; the N,P ligand [2-(3-pyrazolyl)phenyl]diphenylphosphine pzphos has been synthesised and transf
- Kealey, Steven,Long, Nicholas J.,Miller, Philip W.,White, Andrew J. P.,Hitchcock, Peter B.,Gee, Antony
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p. 2823 - 2832
(2008/02/10)
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- Novel phosphine ligands bearing 3(5)-pyrazolyl and 4-(2-amino)pyrimidinyl groups: Synthesis and coordination chemistry
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Novel triphenyl phosphine ligands bearing pyrazole or 2-aminopyrimidine groups in the ortho or meta position of one or three of the phenyl rings were obtained starting from the corresponding acyl derivatives Ph2P(o- C6H4-C
- Sun, Yu,Hienzsch, Antje,Grasser, Jens,Herdtweck, Eberhardt,Thiel, Werner R.
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p. 291 - 298
(2007/10/03)
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- Novel sulfinyl imine ligands for asymmetric catalysis
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(Matrix presented) A novel class of P,N-sulfinyl imine ligands has been prepared that incorporates chirality solely at sulfur. The Pd complex of ligand 14 catalyzes the allylic alkylation reaction with high enantioselectivity (94%), and the first crystal structure of a Pd-bound sulfinyl imine provides insight into binding mode and origins of stereoselectivity.
- Schenkel, Laurie B.,Ellman, Jonathan A.
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p. 545 - 548
(2007/10/03)
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- Water Soluble Phosphanes, XIV [1]. Hydrophilic Derivatives of Triphenylphosphane with NH2, COOH and P(O)(OR)2 Functionalized Side Chains
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Nucleophilic phosphanylation of ortho-fluorophenylacetic acid or ortho-fluorobenzylamine with PhPH2 using KOtBu as the base affords the hydrophilic tertiary phosphanes 3 and 4a with terminal CH2-COOH and CH2-NH2 substituents. The corresponding secondary phosphane ligands 2 or 5 may be obtained by Pd-catalyzed P-C coupling of ortho-iodophenylacetic acid with PhPH2 or selective nucleophilic phosphanylation of ortho-fluorophenylacetic acid. Novel phosphonatomethyl derivatives 7a, 7b of triphenylphosphane have been obtained in a two stage synthesis using ortho-iodobenzylchloride or meta-iodobenzylbromide as starting materials. Arbusov reaction with P(OEt)3 and Pd-catalyzed P-C coupling reactions with Ph2PH gave the esters 7a, 7b. Purification of 7a was achieved via its BH3 adduct 8a. Deprotection, hydrolysis and neutralisation with NaOH affords the water soluble sodium salts 9a,9b. α-Hydroxy and α-benzylamino derivatives 12 and 14 of ortho-diphenylphosphanobenzyl phosphonate (e.g. 7a) and the corresponding Me2P(O) analogs 13 and 16 are accessible in a straightforward manner by addition of (MeO)2P(O)H or Me2P(O)H to ortho-phosphanobenzaldehyde 11a or its benzaldimino derivative 15, respectively. An improved synthesis for 11a-11c has been developed. Reaction of 11a with the Wittig reagent Ph3P=C(H)COOEt and subsequent hydrolysis of the intermediate ester 17a affords ortho-diphenylphosphano cinnamic acid 17. The catalytical activity of 1, 9a, 9b and related ligands in Suzuki-type coupling reactions has been investigated.
- Liek, Christian,Machnitzki, Peter,Nickel, Thomas,Schenk, Stefan,Tepper, Michael,Stelzer, Othmar
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p. 1532 - 1542
(2007/10/03)
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