Formation of [(diphenylphosphino)cyclopentadienyl]thallium and its utility in the synthesis of heterobimetallic titanium-manganese complexes: the molecular structure of (.eta.5-cyclopentadienyl)dicarbonyl[(.eta.5-cyclopentadienyl)[.eta.5-(diphenylphosphino)cyclopentadienyl]dichlorotitanium-P]manganese

Rausch, Marvin D.; Edwards, Bruce H.; Rogers, Robin D.; Atwood, Jerry L.

doi:10.1021/ja00350a024

Cited by 72 publications

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“…Many mono- and persubstituted cyclopentadienylthallium compounds are reported in the literature, and their utility as synthetic intermediates makes them highly useful reagents . Their relative stability and their ease of purification by vacuum sublimation are in contrast to analogous organosodium and organolithium reagents.…”

Section: Resultsmentioning

confidence: 99%

Pendent Aminoalkyl-Substituted Monocyclopentadienyltitanium Compounds and Their Polymerization Behavior

1998

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A series of new aminoalkyl-substituted monocyclopentadienyltitanium trichloride compounds have been prepared that contain pyridyl (2-picolyl), diisopropylaminoethyl, dimethylaminoethyl, and phenylethyl ligands. Incorporation of these pendent ligands to corresponding (cyclopentadienyl)triisopropoxytitanium and (indenyl)triisopropoxytitanium complexes are also described. The utility of these complexes for the polymerization of ethylene, propylene and styrene has been investigated.

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Section: Resultsmentioning

confidence: 99%

Pendent Aminoalkyl-Substituted Monocyclopentadienyltitanium Compounds and Their Polymerization Behavior

1998

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“…Scheme outlines the preparation of homologous chelates 1a , b . Without purification of intermediates, thallium salts 2 were formed in 56−60% overall yield from salts Br(CH 2 ) n NH 3 Br by monoalkylation of CpLi (2 equiv), 6d− protection of the amino nitrogen, and deprotonation of the resulting cyclopentadiene mixture using TlOEt 7b. Metathesis between 2 and [Cl(μ-Cl)Ru(η 6 -arene)] 2 and exchange to the noncoordinating PF 6 - anion 5a provided sandwich complexes 3 , which were deprotected by hydrogenolysis. 5e, Photolysis of 4 in CH 3 CN produced 1 .…”

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High Arenophilicity and Water Tolerance in Direct Derivatization of Peptides and Proteins by Metal π-Coordination

et al. 1998

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Site-specific modification of proteins leads to invaluable structural and reactivity information for biochemical and medicinal studies and to new biotherapeutics. 1 Modification frequently depends on reaction of electrophilic reagents with nucleophilic atoms of the protein. 1 Classic examples include reaction of BrCN at S, 2a RNCS at N, 2b and electrophilic halogens at the tryptophan π-system. 2c The organic reagents which react with tryptophan or tyrosine react much more slowly or not at all with the less electron-rich phenylalanine. Moreover, the same electrophilic or oxidizing reagents also enter into unwanted side reactions with nucleophilic S-or N-donors. 1 Here we show that metal π-complexation to the arene-containing amino acid phenylalanine can succeed even in the face of S-and N-donor ligands found in methionine, cystine, or histidine, leaving these residues unchanged. Metal π-complexation to amino acids and dipeptides has been studied in nonaqueous solvents, 3 and metals have been covalently attached to proteins indirectly, by using organic ligands which are attached to mercapto or amino sites. 4 In contrast, here we report the attachment of a metal directly to an arene ring in a protein in water. Our strategy for reversible derivatization of aryl amino acids exploits the capability of CpRu + and Cp*Ru + fragments to bind to arenes, 3,5 providing air-stable products from which arene subsequently can be released on photolysis. We have made chelates 1, which unlike CpRu + and Cp*Ru + derivatives are new compounds featuring a bound amino ligand, 6 a nucleophile or water-solubilizing group locked by coordination until release by an incoming aryl amino acid. A series of experiments culminating with reaction of the small protein secretin at 10 -4 M concentrations demonstrate high arenophilicity and water tolerance in rapid room-temperature reactions, promising conditions for applications to proteins.Scheme 1 outlines the preparation of homologous chelates 1a,b. Without purification of intermediates, thallium salts 2 were formed in 56-60% overall yield from salts Br(CH 2 ) n NH 3 Br by monoalkylation of CpLi (2 equiv), 6d-8 protection of the amino nitrogen, and deprotonation of the resulting cyclopentadiene mixture using TlOEt. 7b Metathesis between 2 and [Cl(µ-Cl)Ru(η 6 -arene)] 2 and exchange to the noncoordinating PF 6 -anion 5a provided sandwich complexes 3, which were deprotected by hydrogenolysis. 5e,9 Photolysis of 4 in CH 3 CN produced 1. The rate of reaction was greater for the longer side chain (n ) 3) and for the smaller arene. 10a Conversely, arene complexation to 1 in CD 3 NO 2 is about 2 times faster for the shorter side chain, comparisons which may indicate that the chelate ring in 1a is more strained. 10b Arenes (Scheme 2) of widely disparate steric demand, such as 1,3-dimethylbenzene (5a) and 1,4-di-tert-butylbenzene (5b) readily opened chelate 1a under similar conditions (CD 3 NO 2 or CD 3 -OD, 60°C, 1-6 h), to give sandwich complexes 6. Amino acid derivatives 5c-h could also be used, ...

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Titanium: Organometallic Chemistry

Mintz

2005

Encyclopedia of Inorganic Chemistry

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The majority of titanium organometallic chemistry involves complexes in which the titanium is in its highest oxidation state (+4) with cyclopentadienyl derivatives as ancillary ligands. However, considerable chemistry has also been developed for complexes with titanium in the +3 and +2 oxidation state, with lesser amounts of chemistry developed for titanium in lower oxidation states (+1, 0). Since the early 1980s, chemists have placed considerable emphasis on the fine‐tuning of the structure and reactivity of titanium organometallic complexes. Particular emphasis has been devoted to tailoring the structure and reactivity of bis(cyclopentadienyl)titanium derivatives by incorporating electron‐donating, electron‐withdrawing, sterically demanding, or chiral substituents on the cyclopentadienyl ring. Considerable effort has gone into preparing ansa‐metallocenes with a wide variety of bridging groups and substituents to fine‐tune the reactivity catalysts prepared from them. In a similar manner, considerable effort has gone into the development of constrained geometry complexes. Several types of chiral substituted cyclopentadienyl, annulated cyclopentadienyl, ansa ‐metallocenes, and constrained geometry complexes have been prepared and applied to olefin polymerization and organic synthesis. Additional efforts at modifying the structure and reactivity by focusing on varying the oxidation state or coordination geometry at the titanium center have expanded over the past decade.

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Cited by 72 publications

References 2 publications

Pendent Aminoalkyl-Substituted Monocyclopentadienyltitanium Compounds and Their Polymerization Behavior

Pendent Aminoalkyl-Substituted Monocyclopentadienyltitanium Compounds and Their Polymerization Behavior

High Arenophilicity and Water Tolerance in Direct Derivatization of Peptides and Proteins by Metal π-Coordination

Titanium: Organometallic Chemistry

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