Organometallic Chemistry: Volume 23 (Specialist Periodical Reports - Organometallic Chemistry, Volume 23) - Hardcover

Hardcover

ISBN 10: 0851867111 ISBN 13: 9780851867113

Publisher: Royal Society of Chemistry, 1994

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. Specialist Periodical Reports provide systematic and detailed review coverage of progress in the major areas of chemical research. Written by experts in their specialist fields the series creates a unique service for the active research chemist, supplying regular critical in-depth accounts of progress in particular areas of chemistry. For over 80 years the Royal Society of Chemistry and its predecessor, the Chemical Society, have been publishing reports charting developments in chemistry, which originally took the form of Annual Reports. However, by 1967 the whole spectrum of chemistry could no longer be contained within one volume and the series Specialist Periodical Reports was born. The Annual Reports themselves still existed but were divided into two, and subsequently three, volumes covering Inorganic, Organic and Physical Chemistry. For more general coverage of the highlights in chemistry they remain a 'must'. Since that time the SPR series has altered according to the fluctuating degree of activity in various fields of chemistry. Some titles have remained unchanged, while others have altered their emphasis along with their titles; some have been combined under a new name whereas others have had to be discontinued. The current list of Specialist Periodical Reports can be seen on the inside flap of this volume.

About this title

About the Author

Professor Abel is an Emeritus Professor at the University of Exeter.

Excerpt. © Reprinted by permission. All rights reserved.

Organometallic Chemistry Volume 23

A Review of the Literature Published During 1993

By E. W. Abel

The Royal Society of Chemistry

Copyright © 1994 The Royal Society of Chemistry
All rights reserved.

ISBN: 978-0-85186-711-3

Contents

CHAPTER 1 Group I: The Alkali and Coinage Metals By J.L. Wardell, 1, 
CHAPTER 2 Group II: The Alkaline Earths and Zinc and its Congeners By J.L. Wardell, 13, 
CHAPTER 3 Carbaboranes, Including their Metal Complexes By C.E. Housecroft, 23, 
CHAPTER 4 Group III: Boron, Aluminium, Gallium, Indium, and Thallium By K.C. Molloy, 41, 
CHAPTER 5 Group IV: The Silicon Group By D.A. Armitage, 78, 
CHAPTER 6 Group V: Arsenic, Antimony, and Bismuth By J.L. Wardell, 138, 
CHAPTER 7 Metal Carbonyls By J.A. Timney, 144, 
CHAPTER 8 Organometallic Compounds Containing Metal-Metal Bonds By G. Hogarth, 171, 
CHAPTER 9 Complexes Containing Metal-Carbon σ-Bonds of the Groups Scandium to Manganese, Including Carbenes and Carbynes By M.L. Turner and M.J. Winter, 221, 
CHAPTER 10 Complexes Containing Metal-Carbon σ-Bonds of the Groups Iron, Cobalt, and Nickel, Including Carbenes and Carbynes By M.J. Morris, 281, 
CHAPTER 11 Hydrocarbon-Metal π-Complexes, Other than π-Cyclopentadienyl and π-Arene Complexes By D.G. Evans, 325, 
CHAPTER 12 π-Cyclopentadienyl, π-Arene and Related Complexes By I.R. Butler, 376, 

CHAPTER 1

Group I: The Alkali and Coinage Metals

BY J. L. WARDELL

1 Alkali Metals

1.1 General. Reviews have been published on (i) polar allyl type organometallics as key intermediates in regio and stereo-controlled reactions: (ii) structures of organoalkali metal species and (iii) synthesis and reactions of organolithium species. More reports have been made on superbases, i.e. RLi/R'OK combinations; these reports include (i) the effects of lithium alkoxides on deprotonations by BuLi/t-C5H11OK and (ii) the differences in regioselectivities of metallation of RSC6H4OMe by ButLi/ButOK combinations and by BuLi. In cyclopentane, ButLi and ButOH react to form the aggregates [(ButO)ButLi4] and [(ButO)6- nButnLi6] (n=1 or 2) as shown by 13C and 6Li NMR spectroscopy. Two-dimensional 6Li,1H shift correlation experiments based on multiple quantum spectroscopy and polarization transfer have been proposed as new tools for the investigation of organolithium structures. The assignment of the δ6Li values in [o-LiC6H4CH=CHLi-(Z)] was made from the 6Li,1H spin-spin coupling constants. The stabilizing influence of intermolecular Li----H-C contacts in solid organolithium aggregates has been strongly stressed.

1.2 Alkyl species. The structure, 1H, 7Li and 13C NMR spectra, and heat of combustion of [MeLi.THF]4 have been reported. Crystal structures have also been presented for (i) [(BuLi)4.TMED]: BU4Li4 cubane cores linked into polymeric zig-zag chains, by bridging TMED groups; two Li centres are 4 coordinate and two are 3 coordinate, (ii)[BuLi.TMED]2: 4 coordinate Li, (iii) [(BuLi.THF)]4.hexane: each Li atom in the (BuLi)4 units is coordinated to 1 THF, (iv) DME units link (BuLi)4 cores into a polymeric network: each Li is 4-coordinate, (v) (BuLi)6: distorted octahedral units, similar to structure of (cyclohexyl-Li)6, (vi) (ButLi)4 and (viii) [ButLi.Et2O]2: 3 coordinate Li.

The crystal structure determinations of (Me3Si)3CLi.TMED and (Me3Si)3CLi.2THF revealed that they have ionic structures, [Li(TMED)2][direct sum][Li{C(SiMe3)3}2][??] and [Li(THF)4][direct sum][Li{C(SiMe3)3}2][??], in the solid state. Other forms also exist in solution as shown by a multinuclear NMR study. In the solid state [(Me2CCNNa.TMED)4], obtained from metallation of Me2CHCN by BuNa, contain N-Na, rather than C-Na linkages and a (NNa)4 cubane-type core. 1-Lithio-perfluoroadamantane (1) obtained by H/Li exchange using MeLi in Et2O, is thermally stable to 0 °C; of interest, 2-lithio-perfluoroadmantane rapidly converts to (1) below -60 °C.

α-Aminoalkyl-lithiums, e.g. MeOCH2CH2NMeCHRLi (R=C5H11 or Pri), obtained by Sn/Li exchanges, are configurationally stable for short times at -78 °C; 2-lithio-N-methyl-piperidines and pyrrolodines are configurationally stable for up to 45 minutes at -40 °C in the presence of TMED. The barriers to racemisation of PhCH2CHLiSeAr in THF-d8/C6D6 were calculated to be 12.4 and >14.5 k cal mol-1 for Ar=Ph and 2,3,5,6-Me4C6H respectively; the rate determining step for racemisation was suggested to be the rotation about the carbanion-heteroatom bond. A similar finding was deduced from an NMR study of (PhMe2Si)CHLi(YPh) (Y=S or Se).

α-Lithiated ethers, RCHLi(OR') (2), react with R2Li to give RR2CHLi. This finding, plus the value of δ13Cα in (2) being downfield of that in RCH2OR', gave support to the view that (2) can be classed as oxygen carbenoids. A very large primary isotope effect (kH/kDca 70) was found in reactions of (2) with BuLi.TMED at -78 °C, equation 1.

In aromatic solvents, 1,2-dilithio[tetrakis(trimethylsilyl)]ethane has a similar doubly bridged structure to that found in the solid state; in contrast the compound in THF exists as s.s.i.p. [Li(THF)4]+ [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]. 1,1-Dilithiocyclopropane (4) has been calculated [3-21G//Dunning basis set level] to be more stable with a planar rather than a tetrahedral geometry. The preparation of (4), from 1,1-Br2-cyclopropane and Naph-·,Li+ has been reported. Reaction of 7,7- dihalonorcaranes (R2CX2) with [p- ButC6H4C6H4But-p]-·,Li+ at -80 ° has been shown to produce R2CXLi, R2CLi2 and R2CLiCLiR2 in amounts depending on X, T °C and added ligands. The reaction of 7,7- dilithionorbomane with butyl halides at -100 °C provides 7,7'-dilithio-7,7'-dinorbomyl (5); (5) undergoes ready loss of Li2 (i.e. oxidation) to give 7,7'-norbornylidene.

Calculations have been carried out on CLi8, CLi10 and CLi12 [SCF level: 3-21 G, DZ(P), DZP and TZ2P basis sets].

1.3 Benzylic species. Crystal structures have been determined for (i) [Ph3CK.THF.PMDT]: monomeric c.i.p. species; K+ is η6-coordination to one phenyl ring (there is no K coordination to the benzylic carbon); (ii) [Ph3CRb.PMDT]n: 1-d polymer with Rb+ bridging Ph3C groups by η6-coordination to two phenyl groups and (iii) [Ph3CCs.PMDT]n: 1-d polymer; Cs+ is η6- bonded to one phenyl group of a Ph3C unit as well as interacting with all three phenyl rings and the benzylic carbon of another Ph3C group.

In solid [PhCH(NMe2)Li.OEt2]2, lithium centres bridge benzylic carbon atoms; additional bonding to each lithium involves the amino and ether groups. In [(S)-PhCH[NMeCOBut)Li.(-)- sparteine], lithium is bonded to carbon, oxygen and the two nitrogens of the sparteine ligand. Crystal structures have also been determined for [Ph2C(C5H4N-o)Li.2OEt2], [Ph2C(C5H4N-o)Na.3THF] and [Ph2C(C5H4N-o)K.PMDT].

1.4 Aryl derivatives. A d-functional theory calculation has been carried out on C6Li6; a MNDO calculation has been conducted on lithiabenzene. A solid state 7Li NMR study of phenyl-lithium aggregates has been reported. A good agreement was generally found between the quadrupole splitting constant values determined in the solid state and in solution, i.e. the solid state structure is basically retained in solution. Crystal structures have been determined for the following unsolvated aryl-lithiums: (i) t2,4,6-Pri3C6H2Li]4: near planar array of lithium atoms; each Li is η1,σ-bonded to one aryl ring and η6,π-bonded to another; (ii) [2,6-(2,4,6- Me3C6H2)2C6H3Li]2: lithium atoms bridge ipso carbons, with secondary lithium contacts with carbons of the mesityl groups; and (iii) [BuLi(2,4,6-But3C6H2)Li]2: near planar array of lithium atoms bridged alternatively by η1-μ2-butyl and η6,η6-μ2-aryl groups.

In solid [3-I-2-Li-1-methylindole.2THF]2, lithium atoms bridge ipso carbons and each is additionally coordinated to two THF ligands. The compound, [{2,6-(Me2NCH2CH2NMeCH2) 2C6H3}Li2Br], (6; ArLi2Br) obtained from ArBr and 2 equivalents of BuLi, has been characterized by X-ray crystallography and by NMR spectroscopy; (6) has a novel Li2ArBr core, in which Br bridges the two lithium centres and Cipso is involved in 3 centre 2 electron bonds with the 2 Li. The coordination sphere of each Li is completed by coordination with 2N atoms.

A theoretical treatment of the ortho-lithiation of PhF by LiH has been reported. ortho-Lithiations of iodopyridines have been achieved using LiNPri2 at low temperature; subsequent rearrangements may occur, e.g. as shown by 2-F-3-I-pyridine on successive reactions with LiNPri2/THF at -75 °C and D2O giving 2-F-3-D-4-I-pyridine. The ortho-directing abilities of -CONHR, - CONR2 and -CRR'OH have been further investigated. The formation of α-lithio- and o-α-dilithio N-phenylpyrrole on lithiation by BuLi/complexing ligand have been reported; dimetallation is kinetically but not thermodynamically favoured. Lithium/chloride exchanges occur on reactions of chloroarenes with lithium in the presence of naphthalene. Substrates which contain both an acidic hydrogen and an aryl bromide group (e.g. bromoanilides) preferentially undergo initial deprotonation on reaction with organolithiums.

Theoretical studies have been made on LiC2H2 and NaC2H2; from an ab initio calculation {[UMP2/6-311 ++ G(d,p)], for geometries and PUMP/6-311 ++ Gd(d,p) + ZPE level (for relative energies)}, it was concluded that these species have cis-bent bridged geometries and 2B2 ground electronic states. Complexation of HC[equivalent to]CH or H2C=CH2 by lithium has also been studied by ESR spectroscopy. Complexation of semibullvalene by Li+ has been calculated to reduce the barrier to Cope rearrangement to zero.

As shown by 13C, 7Li coupling constants and multiplicities in the NMR spectra, vinyl-lithium exists in a dimer-tetramer equilibrium in THF. The tetramer undergoes an intra-aggregate C-Li bond exchange process. A comprehensive analysis of the NMR spin-spin coupling constants was made. The 1Jc,c values in vinyl-lithium were determined to be very small, viz 35.0 Hz for the dimer and 36.3 Hz for the tetramer.

The crystal structure of the carbenoid [(p-ClC6H4)2C=CClLi.TMED.THF].THF has been determined at -115 °C; Li is bonded to C, O and 2N. Of interest, the C-Cl bond in (7) [1.855(7) Å] is much longer than that in non-lithiated vinyl chlorides (average value 1.729 Å). The preparation of (Z)- LiCH=CHC6H4Li-o from reaction of (Z)-LiCH=CHPh and ButLi/TMED has been reported. 1H and 13C NMR spectral studies of H2C=CH- CH(Li)SiMe2CH2N(CH2CH2OMe)2 in THF and toluene indicate an equilibrium mixture of endo- and exo-silyl species in which Li is tridentately complexed to the pendant ligand. The value of ΔH‡ for rotation about the SiC1-C2 allyl bond was found to be 16 ± 0.5 kcal mol-1.

The 13C NMR spectra of Me3SnCH2CLi=C=CH2 (7), H2C=C(SnMe3)-CLi=CH2 (8) and LiCH2C[equivalent to]CCH2Li have been reported; (7) and (8) were the initial products of reaction of MeLi with Me3SnCH2-C[equivalent to]C-CH2SnMe3, and H2C=C(SnMe3)-C(SnMe3)=CH2. The role of s.s.i.p. and c.i.p. species, as well as 'ate' complexes, in the electrophilic reactions of the organolithium compounds generated by Sn/Li exchanges of PriC(SiR3)=C=CH2 or PriC[equivalent to]CCH2SnR3 have been studied. Solid, 1-(Z)-3-(Z)-(TMED)LiC(SiMe3)=CH-CH=C(SiMe3)Li(TMED), has a double bridged structure, similar to that predicted by ab initio calculations on LiCH=CH-CH=CHLi. Spectroscopic (13C NMR,6Li,1H-HOESY NMR and IR) studies of, and ab initio calculations on, H2C=C=C(OMe)Li indicate it is a 1,3-bridged dimeric compound in THF and a tetramer in Et2O.

Theoretical studies have been conducted on the carbometallation of cyclopropene and ethene by MeLi, MeCu and Me2Cu[??]. Intramolecular carbolithiations of undec-10-en-5-ynyl-lithium, H2C=CCH2CH2CH(CH2Li)CH2CH2 (to give l-norbomylmethyl- lithium) and PhSO2CR'LiCH2CH2C[equivalent to]CXR2 (X=S or O) have been reported.

Solid state 23Na and 13C NMR spectra of CpNa.TMED have been presented, as have the solution NMR spectra of C(C5H4Li)4, obtained from BuLi and Cp4C at -78 °C in THF. The formation from CpNa and PhCO2Et in refluxing THF and characterization of η5-(PhCOC5H4)Na have been reported. The air- and moisture-sensitive complexes [R2C=O.LiC5(SiMe2H)5] (9; R=Ph or But) have been synthesized from R2CO and THF.Li[C5(SiMe2H)5]; δ7Li = -7.51 and -7.55 ppm for (9; R=Ph) and (9; R=But) respectively. The Li+ ion in solid (9; R=Ph) is 1.818 Å above the centre of the cyclopentadienyl ring; the Li-O bond length is 1.822 Å. In solid, c-i-p [(η5-Cp)2Tl-, Li+(TMED)], one of the Cp ligands, bound to Tl, is additionally π-bonded to Li(TMED) (Li-Cp centroid = 2.25 Å).

Dilithio species, {[Li(TMED)]2[o-C6H4CH2B(NR)CH2]}, (10) obtained from lithiation of 2-R2N-2-boraindanes, have triple decked structures consisting of aromatic 10π-electron 2-benzoborole dianions and two [Li(TMED)]+ moieties facially bonded to the borole ring.

The crystallisation of potassium fluorenide or 9-But-fluorenide from a mixture of THF, TMED and Et2O yielded [[FlK(TMED)2] or {[K(THF)2] [μ-9-ButFl][K(TMED)] [μ- 9-ButFl]} (11). Both complexes were characterized by X-ray crystallography and by NMR spectroscopy; (11) has a polymeric chain structure with K coordinated to two 6-membered rings from two bridging 9-ButFl units.

2 Copper

2.1 General. Highly reactive forms of copper are obtained by the reduction of CuI.PR3 (R=Bu or Ph), CuCN.nLiX or [2-thienylCu(CN)Li] with Naph-·,Li+. The activated copper reacts directly with RBr (R=alkyl or aryl) as well as with allylic chlorides and acetates; a variety of functional groups are tolerated. Routes to organocopper species via transmetallation reactions have been reviewed.

2.2 π-Complexes. Copper atoms and MeC[equivalent to]CR (R=H or Me) form 1:1 and 1:2 complexes in the gas phase: binding energies of the 1:1 complexes are 32 ± 6 (R=H) and 36 ± 6 (R=Me) kJ mol-1. The kinetics of reaction of Cu2 and H2C=CH2 have also been studied. The synthesis and spectral characterization of [ButCOCHCOC3F7]CuL (L = 1,5-cyclooctadiene, Me3SiCH=CH2, MeC[equivalent to]CMe or Me3SiC[equivalent to]CSiMe3) have been reported; the potential of these compounds in CVD was tested.

Crystal structures have been determined for (i) [3CuX.(H2C=CHCH2C[equivalent to]CCH2CH=CH2] (X=Cl or Br); (ii) [Cu2{PhCH2N(C5H4N-o)2}2 (η2,η2-S-trans-isoprene)].2O3SCF3; each Cu is coordinated to 2N (pyridine), to a double bond, and more weakly to an O of a O3SCF3 group; (iii) [(O2CCH2CH2CH2CO2)(norbomadiene)(py)2Cu2]p y: each Cu is coordinated to 1 N, 1 double bond and 1 O of a O2C group: molecules are linked by alternating adipinate and norbomadiene moieties; and (iv) various 3,3,6,6-tetramethyl-l-thia-4-cycloheptyne (12; L) complexes, e.g. (13), [L-CuI(SMe2)], [L-CuN[equivalent to]C]4 L-Cu(η5-Cp) and [L-Cu-(Me3SiN-CPh-NSiMe3)]. Complexes, (acac)Cu(CNBut) and CpCu(CNBut) have also been studied.

(Continues...)

Excerpted from Organometallic Chemistry Volume 23 by E. W. Abel. Copyright © 1994 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: 1994
• Language: English
• ISBN 10: 0851867111
• ISBN 13: 9780851867113
• Binding: Hardcover
• Edition number: 1
• Number of pages: 456
• Editor: Abel E W