Niobium organometallic compounds

As a part of their quest for species and its organometallic synthon, Cummins and coworker reported that ethylenebis(triphenylphosphine) platinum(O) [(C2H4)Pt(PPh3)2] can act as effective probe for niobium-mediated diphosphorus chemistry [125], Upon treatment by 2equiv. of [(C2H )Pt(PPhj)2], niobium diphosphaazide compound 172 was converted into heteromultimetallic compound 173 which bears a Pt(l)-Pt(l) bond (Scheme 10.75). The Pt Pj diamond-shape core of 173 is in planarity, and the Pt(I)-Pt(l) bond length is 2.6490(13) A (Entry 7, Table 10.12). 

Compounds containing niobium or tantalum in negative formal oxidation states -I and -III are mainly metal carbonyl anions. Although these are organometallic derivatives, the report of efficient procedures for the synthesis of [M(CO)6] since the review of Labinger8 merits mention, as it can be anticipated that these highly reduced and reactive species will be important precursors of a large variety of new coordination compounds and metal clusters. 

Acetyl ligands, in niobium complexes, C-H BDEs, 1, 298 Achiral phosphines, on polymer-supported peptides, 12, 698 Acid halides, indium compound reactions, 9, 683 Acidity, one-electron oxidized metal hydrides, 1, 294 Acid leaching, in organometallic stability studies, 12, 612 Acid-platinum rf-monoalkynes, interactions, 8, 641 Acrylate, polymerization with aluminum catalysts, 3, 280 Acrylic monomers, lanthanide-catalyzed polymerization,... 

Organometallic Niobium ) and Tantalum ) Compounds. Reports this year have concerned two main areas of interest the preparation of alkyl-niobium and tantalum halides and their reactions with donor ligands, and insertion reactions into methyl-metal bonds. The first examples of monomethyl niobium and tantalum compounds have been prepared by the low-temperature methylation of the appropriate halides... 

Kopf-Maier P, Kopf H (1994) Organometallic titanium, vanadium, niobium, molybdenum and rhenium complexes - early transition metal antitumor drugs. In Fricker SP (ed) Metal Compounds in Cancer Therapy. Chapman Hall, London, pp 109-146... 

The number of niobium and tantalum coordination compounds in oxidation states lower than II is limited, and they often are organometallic derivatives involving carbonyl, cyclopentadienyl, or alkenic ligands. 

The most important starting materials for organometallic complexes of niobium and tantalum are their pentachlorides, NbCls and TaCls. The commercially available pentachlorides can be sublimed if further purification is necessary. They are commonly used for access to both high-valency and low-valency compounds. The crystal structure of NbCl5 consists of dimeric Nb2Cl owith two chlorides bridging as shown in Scheme 7.8, and the Ta analogue is presumed to have a similar structure. In non-... 

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