Organometallic Chemistry: Volume 33 (Specialist Periodical Reports - Organometallic Chemistry, Volume 33) - Hardcover

Hardcover

ISBN 10: 0854043489 ISBN 13: 9780854043484

Publisher: Royal Society of Chemistry, 2007

Synopsis

Organometallic chemistry is an interdisciplinary science which continues to grow at a rapid pace. Although there is continued interest in synthetic and structural studies the last decade has seen a growing interest in the potential of organometallic chemistry to provide answers to problems in catalysis synthetic organic chemistry and also in the development of new materials. This Specialist Periodical Report aims to reflect these current interests reviewing progress in theoretical organometallic chemistry, main group chemistry, the lanthanides and all aspects of transition metal chemistry.

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Organometallic chemistry is an interdisciplinary science which continues to grow at a rapid pace. Although there is continued interest in synthetic and structural studies, the last decade has seen a growing interest in the potential of organometallic chemistry to provide answers to problems in catalysis, synthetic organic chemistry and also in the development of new materials. This Specialist Periodical Report aims to reflect these current interests, reviewing progress in theoretical organometallic chemistry, main group chemistry, the lanthanides and all aspects of transition metal chemistry.

Excerpt. © Reprinted by permission. All rights reserved.

Organometallic Chemistry Volume 33

A Review of the Literature Published During 2003

By M. Green

The Royal Society of Chemistry

Copyright © 2007 The Royal Society of Chemistry
All rights reserved.

ISBN: 978-0-85404-348-4

Contents

Groups 1 and 11: The Alkali and Coinage Metals By S.R. Boss, A.E.H. Wheatley, 1, 
Group 2 (Be-Ba) and Group 12 (Zn-Hg) By Felipe García, Dominic S. Wright, 22, 
Scandium, Yttrium and the Lanthanides By John G. Brennan, Andrea Sella, 38, 
Carboranes, Including Their Metal Complexes By Paul A. Jelliss, Andreas Franken, 81, 
Group III - B, Al, Ga, In, T1 By Simon Aldridge, 102, 
Group 14: Silicon, Germanium, Tin and Lead By Richard A. Layfield, 156, 
Recent Advances in the Chemistry of Phosphaalkynes: Building Blocks for Novel Organophosphorus Compounds By Jason M. Lynam, 170, 
Organo-Transition Metal Cluster Complexes By Mark G. Humphrey, Marie P. Cifuentes, 179, 
Complexes Containing Metal-Carbon σ-Bonds of the Groups Iron, Cobalt and Nickel, Including Carbenes and Carbynes By Philip J. King, 230, 
Organic Aspects of Organometallic Chemistry By Steven D.R. Christie, Adam D. Warrington, 279, 

CHAPTER 1

Groups 1 and 11: The Alkali and Coinage Metals

BY S.R. BOSS AND A.E.H. WHEATLEY

Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW

1 Alkali Metals

1.1 Introduction. – Part 1 of this review is concerned with alkali metals (M+). It is sub-categorized primarily according to the organic anion component (R-) of organometallics of the type Rn- (M+) n. Except in cases of extreme interest, discussion will be limited to compounds that contain at least one carbon-alkali metal interaction. An overview of synthetic and mechanistic investigations of alkali metallated organics is to be found at the start of each section. Structural studies are then arranged by analytical method used; solid-state investigations are followed by solution and gas phase studies in that order.

1.2 Alkyl Derivatives. – The seminal contribution of Snaith to organolithium chemistry has been remembered recently.

The enantioselective addition of methyllithium to imines has been used to demonstrate that the N-centres in newly prepared diamines (based on a cyclohexane diamine core) become stereogenic upon metal chelation. The introduction of MeLi to the first stable methyl-substituted disilene has afforded a solvent-separated silyl-anion species. Meanwhile, MeLi has also been employed in conjunction with LH {L = N,N-(1,3-dimethyl-1,3 -propanediylidene)bis(N,N-diethyl-1,2-ethanediamine} to yield the corresponding lithium salt, LLi. Reaction of this with Br3Tb has yielded the first example of a β-diketiminato complex of terbium. Reaction of {2- MeOC6H4 (H)N}3Al with excess EtLi has led to metallation of the three NH groups and nucleophilic addition to the lithium triimidoaluminate. This yielded a cluster, [{(2-MeO C6H4N)3AlEt} 2Li6]2-, that has been interpreted as containing the highest negative charge observed crystallographically for an imido main group cluster. Intramolecular carbolithiation of lithium carbanions is an accepted route by which to construct carbocycles and it is in this context that BunLi has recently been employed in the generation of α-metallated ω -carbamoyloxy-1-alkynyl carbamates. Subsequent intramolecular anti-selective carbolithiation has enabled the isolation of enantioenriched protected 2-alkylidene-cycloalkane -1,3-diols. n-Butyllithium has been employed synthetically in the preparation of lithium enolates of α-amino acid derivatives. Subsequent asymmetric protonation with α-amino acid-based chiral Brønsted acids has yielded unnatural a-amino acids. The same organolithium substrate has been reacted with the sodium salt of 2'-deoxy-3',5'-bis-O-(tert -butyldimethylsilyl)-5-iodouridine in order to effect regioselective deprotonation at the 5-position. Subsequent application of electrophiles has conveniently afforded 5-substituted 20-deoxyuridines. The use of BusLi-{(-) -sparteine} has allowed the α-lithiation-rearrangement of three cyclic N -toluenesulfonylaziridines with metallation prevailing at the S-aziridine stereocentre. Notably, this sense of asymmetric induction is the opposite to that noted for epoxide reaction.

The aminophosphine (2-NC)C6H4N(H)PPh2 has been lithiated using BunLi to give (2-NC)C6H4 (Ph2P)NLi. This has, in turn, been reacted with Ph2PCl or MeI to give (2-NC)C6H4NQPPh2PPh2 and (2 -NC)C6H4N=PPh2Me · LiI, respectively. Reaction of vinyl(homoallyl)silanes or vinyl(homopropargyl)silanes with BunLi (or ButLi) has yielded new silacyclopentanes via a tandem intermolecular-intra- molecular process involving a 5-exo cyclization. Thioanisole-functionalized secondary phosphine (Me3Si)2C(H)P (C6H4SMe-2) has been treated with BunLi · tmeda to give the s photoactive lithium phosphide {(Me3Si)2C(H)P(C6H4SMe-2)}Li · tmeda or with excess BunLi/tmeda to yield {(Me3Si)2C(H)P(C6H4S-2)}(Li · tmeda) 2. The lithiation, using BunLi, of tris(alkyl- and tris(arylamido)orthophosphates EP{N(H)R}3 (E = O, Se, Se) has been monitored recently and has allowed elucidation of the effects had by imido substituents on PQE bond cleavage processes. Treatment of BunLi with elemental selenium has yielded a butylselenolate capable of reacting with 1-alkynylphosphine oxides and aldehydes to give Se-substituted allenes via a one-pot tandem Michael/aldol/Horner -Wadsworth-Emmons reaction. Total synthesis of the dolabellane diterpene ([+ or -]) -acetoxy odontoschismenol has been allowed utilizing zirconium chemistry, with an in situ generated carbenoid substrate H2CC(H)CH(Cl)Li being used to insert into a zirconacycle intermediate. The creation of lithium diphenylphosphide using BunLi has enabled the synthesis of new lithium tellurophosphinite, ditellurophosphinate and selenotellurophosphinate complexes.

Solvent and temperature effects on lithium-iodine exchange in primary alkyl -iodides have been investigated using ButLi and 1-iodooctane in mixtures of heptane and four dialkylethers {diisopropylether, methyl t-butylether (mtbe), thf, and tetrahydropyran). Exchange, slow in pure hydrocarbon solvent, has been found to be significantly enhanced by the presence of catalytic amounts of etherate co-solvent. At depressed temperatures, the yield of octyllithium has been found to be near quantitative if a 19:1 heptane-mtbe mixture is used as solvent. Organopotassium reaction intermediates of the type R2C(K)C(R)2OK, which are derived from monosubstituted oxiranes by the alkalide K- ,K+ · 2(15-crown-5), have been shown to be unstable at ambient temperature and to undergo several classes of reaction; the most important such process being crown ether ring cleavage. Reaction of PhCH2K with a {But (Me3Si)N}2 Mg/But(Me3Si)NH/BunLi mixture has yielded a mixed lithium-potassium-(bis)magnesium inverse crown molecule whose cavity is vacant. In a similar vein, the employment of benzylpotassium in conjunction with n, s-dibutylmagnesium and diisopropylamine in toluene has led to the formation of {(Pri2N) 2(µ-H)MgK · PhMe}2. 2-C5H4NCH2K has been used in conjunction with zirconium tetrachloride to yield (2-C5H4NCH2)ZrCl2 and this has, in turn, been treated with dipotassium N,N'-(1,2-dimethylene-1,2-ethanediyl)bis(2,6-diisopropylanilide) in order to give {N,N'-(1,2-dimethylene-1,2-ethanediyl)bis(2,6-diisopropylanilido)-κ 2N,N'} bis(2-picolyl)zirconium(IV). This species has been shown to be highly capable of effecting ethylene polymerization when activated with methylaluminoxane.

Alkyllithium substrates have been employed in the preparation of new asymmetrical dianionic polyimido-sulfur(IV)-ylides. Accordingly, the 1:2 reaction of sulfurdiimides (RN=S-NR) with alkyllithium reagents in donor solvents has yielded dimeric C,N-dilithium-methylenediimidosulfite complexes. In a similar vein, the reaction of 3-bromothiophene with BunLi and ButN=S=NBut has given the first example of a dianionic S(IV)-β-ylide.

Tert-butyllithium has been used in conjunction with MeM2Zn/hppH and Me3Al/hppH (hppH = 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2 -a]pyrimidine) mixtures to yield new alkali metal clusters. Whereas the use of Me2Zn affords interstitial hydride complex [ZnBut3] -[(hpp)6 HLi8]+, that of Me3 Al in such a system leads to formation of the hydride-free polyhedral cluster complex {[(But2AlMe2) 2-Li]-}2[(hpp)6Li8]2+. The use of ButLi has also been reported to enable the synthesis of new alkali metal zincates of the type {PhC(O)N(R)ZnR' 2Li · 2thf}2 (R, R' = alkyl) as well as the mixed-anion lithium zincate/lithium amide aggregate {PhC(O)N(Ph)Li · thf}2 · {PhC(O)N(Ph)ZnBut2 Li · thf}2.

(Me3Si)2 NC(NPri)2 Li has been employed in the synthesis of new lanthanide (III) bis(guanidinates). In this context, reaction of {(Me3Si) 2NC(NPri) 2}Nd(µ-Cl)Li · 2thf with MeLi has yielded {(Me3Si) 2NC(NPri)2}Nd(µ-Me)Li · tmeda – a complex that demonstrates high activity for the ring-opening polymerization (rop) of ε-caprolactone. Likewise, MeLi has been used in conjunction with {Dipp (Me3Si)N}2LnCl · thf (Dipp = Pri2-2,6-C6H3) to yield {Dipp(Me3Si)N}2 LnMe(µ -Me)Li · thf for studies into the polymerization of methyl methacrylate. Reaction of the appropriate silyl(trimethylgermyl)methyllithium, Me3Si(Me3Ge)CHLi or Me2PhSi(Me3Ge)CHLi, with the corresponding R3SnCl (R = Me, Ph) substrate has led to the silylgermylstannylmethanes Me3Si(Me3Ge)(R3Sn)CH and Me2 Ph-Si(Me3Ge)(Me3Sn)CH.

The crystal structures of four chiral alkyllithium-{(-)-sparteine} complexes, of MeLi, BunLi, PriLi and ButLi have been reported. The solid-state structure of tris(trimethylsilyl)tetrahedranyllithium has also been presented, with the compound being synthesised by reaction of MeLi with tetrakis (trimethylsilyl)tetrahedranes. The reactivity of tetrahedranyllithium has subsequently been analysed. The solid-state structures of new binolate complexes have been reported. The reaction of racemic 5,5',6,6'-tetramethyl-3,3'-di-tert -butyl-1,1'-biphenyl-2,2'-diol (biphenolate-H2) with BunLi has yielded (µ 3,µ3-biphenolate)2Li4 · (BunLi) 4. This mixed-anion complex has been reacted with 2,4-dimethyl-3-pentanol/thf or /cyclohexene oxide (CyHO) to give the lithium aggregate (µµ-biphenolate)Li2{µ 3-OCH(Pri)2} 2Li2 · 2L (L = thf, CyHO). These complexes, along with Al and Zn analogues, have been tested for rac-lactide polymerization activity. Mixed-anion lithium amide clusters that incorporate BunLi moieties have been reported. The study of multidentate phosphinoalkoxides has yielded a mixed-anion dimer incorporating alkyllithium fragments. Bis{(dimethylphosphino)methyl}methanol has been both lithiated and sodiated to give the corresponding simple metal alcoholate {(Me2PCH2) 2CHOM} 6 (M = Li, Na). Meanwhile, reaction of (Me2PCH2) 3COH with excess BunLi in the absence of solvent has given dimeric {(Me2PCH2) 3COLi · BunLi}2.

The simple monomer of Ph{Me2NSi(Me2)}CHLi · tmeda has been reported. Advances have been made in the understanding of lateral lithiation processes. In this context, 2-ethyl-N,N-diisopropyl-1-naphthamide has been treated with ButLi to yield the laterally metallated derivative. It exists as a tris(thf) solvated monomer with no Li–C interaction and an sp2 hybridized carbanionic centre in the solid-state. Just as reaction of (Me6PCH2)3COH with excess BunLi in the absence of solvent has been shown to yield {(Me2PCH2)3COLi · BunLi}2, so similar reaction in toluene gives a symmetrically tris(phosphino)-substituted trimethylenemethane dianion, as revealed by the mixed-anion cluster {(Me2PCH2)3CO}{(Me2PCH) 3C}Li3. Various crystalline alkali metallated silylmethyls and diastereomerically enriched silylbenzyls have been reported recently. Also lately presented is the structure of (Me3SiN=PPh2)2CHLi · thf in which the metal ion is coordinated by the methanide carbon centre and both imino N-atoms to give strained fourmembered edge-fused metallocycles. This species has been prepared by the treatment of bis(iminophosphorano)methane with BunLi.

The complexes Ph2CHRb · 18-crown-6 and Ph2CHRb · 18-crown-6 · thf have been recently shown to reveal η1- and η6-behaviour of the diphenylmethanide ligand, respectively.

Moving to heterobimetallic arrays, the inclusion of alkyllithium fragments has been recently reported. Sequential reaction of Cl3As with excess 2-PhOC6H4NH2 and BunLi has yielded a bis(imido)organoarsenate cluster based on a 14-membered As2N4C2Li6 motif.

Just as mixed Nd/Yb-Li systems have been prepared in order to study rop processes so, too, have new ansa-bis(allyl) lanthanide systems been targeted in order to facilitate the catalytic polymerization of methyl methacrylate. As part of this work the polymeric complex [Ln{(η3 -C3H3SiMe3)2SiMe2} 2{µ - K · thf}]∞ (Ln = La, Y, Sc) has been characterized. It is a coordination polymer incorporating potassium bridges between allyl units. In a like vein, the reaction of {1,3 -(Me3Si) 2C3H3}K with samarium iodide has yielded the ?rst example of a structurally characterized Sm(II) allyl complex; [{1,3-(Me3Si) 2C3H3}3 (µ-K · 2thf)] 2 reveals η3-allyl support of the group 1 metal ions.

High-field, low-temperature NMR spectroscopic data has been collected on mixtures of isotopically enriched 6-methyllithium and 6-lithium bromide. Results have suggested that the populations of five possible complexes exhibit a near statistical distribution notwithstanding the cluster MeLi(BrLi)3. This species was found to be less populous and density functional theory bore this out. The origin of diastereoselectivity in the addition of alkyllithium substrates to Schiff bases bearing a N-stereogenic centre with no additional heteroatom has been theoretically probed. This has allowed the identification of Schiff bases, derived from 1-phenyl-2-methylpropylamine, that show superior C=N πθ-facial selectivity as compared to those derived from commonly employed 1-phenethylamine.

1.3 Alkenyl, Allyl, Vinyl, Alkynyl and Related Derivatives. – A general method for the stereospecific and regioselective C(3) alkynylation of hindered C-centres in 2,3,3-trisubstituted 2,3-epoxy alcohols and non-functionalized trisubstituted expoxides has been reported. It uses alkynyllithium substrates in conjunction with Me3Al to generate 'ate complexes. The lithium β-diketiminate HC{C(Ph) N(SiMe3)}2Li has been prepared and reacted with group 4 metal salts to afford the α-olefin isomerization and propylene polymerization catalysts HC{C(Ph) N(SiMe3)}2TiCl2 and [HC{C(Ph)N(SiMe3)}]{(Me3Si)C(H)C(Ph)NC(Ph)N (Si-Me3)}ZrCl2.

Potassium enolates of representative β-dicarbonyl compounds have been employed with 2-bromopropanamides with and without silver promoters to enable the formation of new heterocyclic compounds through C–C or C–O alkylation processes.

The crystallographic study of a wide variety of 1-azaallyl- and 1,3-diazaallyllithium aggregates have been recently undertaken, multiple metal coordination modes having been observed. For the metallocyclic trimer of (Me3Si)C(H) C(Ph)N(SiMe2OMe)Li, the 1-azaallyl ligands act as η3 N,C,N'-coordinating ligands.

The solid-state structure of the dipotassium tetraalkynylzincate (HCC)4ZnK2 · 2NH3 has been reported. It reveals tetrahedral zincate fragments that are linked into zigzag chains of edge-sharing distorted (HCC)6 octahedra centred by alkali metal ions.

The solution structures of potassium ion-encapsulating lariat ethers having π-donor sidearms have been studied using NMR spectroscopic methods. Data point to the interaction of triple bond donors with the metal centre in acetonitrile solution.

A theoretical study has offered an expalantion for the stereochemistry observed in 1,5-dimethylpyrrolidin-2-one lithium enolate (Meyers enolate) alkylations. Using density functional theory, computations modelling the enolate in both the gas phase and in thf solution suggest the dominant (498%) isomer to be the stereoisomer that incorporates trans-oriented Me -groups with the metal being η3-supported by both the enolate O-centre and by the π-system.

1.4 Aryl Derivatives. – Ether-soluble N-lithio-N-allyl-2-lithioaniline has been found to undergo cyclization at +5 °C in tmeda to yield a (1-lithio-3 -indolinyl) methyllithium that can be differentially functionalized by the sequential introduction of electrophiles.

From a structural point of view, the ability of aromatic sidechains of amino acids to support alkali metal cations has been the subject of recent review. The syntheses and structural characterizations of lithiated benzenoid aromatics have also been reviewed lately. Meanwhile, aryllithium precursors have proved to be instrumental in the preparation of oxygen-stabilized organoaluminium compounds for action as co-catalysts in Ziegler-Natta olefin polymerization. The precursor phenylthiomethyl-functionalized carbosilane dendrimers Si{(CH2)3SiMe2CH2SPh}4 and Si[(CH2)3Si{(CH2)3SiMe2CH2 SPh}3]4 have been generated and metallated to give lithiomethyl-functionalized dendrimers. A method by which to enable the isolation of these lithated dendrimers has also been presented. Reaction of enantiomerically pure (R or S)-2-Me2NCH(Me)C6H 4Li with (Me3Si)2C(H)PCl2 followed by lithium aluminium hydride reduction has allowed the formation of a 50/50 mixture of epimers (at phosphorus) of diastereomeric secondary phosphane {(Me3Si)2CH}{(R or S)-2 -Me2NCH(Me)C6H4}PH. Conversion of either C-stereoisomer to the to the corresponding lithium phosphanide has also been reported.

(Continues...)

Excerpted from Organometallic Chemistry Volume 33 by M. Green. Copyright © 2007 The Royal Society of Chemistry. Excerpted by permission of The Royal Society of Chemistry.
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Edition details

• Publisher: Royal Society of Chemistry
• Publication date: 2007
• Language: English
• ISBN 10: 0854043489
• ISBN 13: 9780854043484
• Binding: Hardcover
• Edition number: 1
• Number of pages: 332
• Editor: Green M