scispace - formally typeset
Search or ask a question

Showing papers by "Malcolm L. H. Green published in 1980"



Journal ArticleDOI
TL;DR: The tetramer [{Mo(η-C5H5)2HLi}4] reacts with N2O giving the yellow dimers cis- and trans]-(µ-σ : η5H4)2].
Abstract: The tetramer [{Mo(η-C5H5)2HLi}4] reacts with N2O giving the yellow dimers cis- and trans-[{Mo(η-C5H5)H}2-(µ-σ : η-C5H4)2]. These thermally rearrange to the green dimer [{Mo(η-C5H5)H}2(µ-η5-C5H4-η5-C5H4)]. Protonation of the latter gives [{Mo(η-C5H5)H}2(µ-H)(µ-η5-C5H4-η5-C5H4)][PF6]. Photolysis of [Mo-(η-C5H5)2H2] or the yellow dimers gives a red dimer [{Mo(η-C5H5)}2(µ-σ : η5-C5H4)2]. Prolonged treatment of the four neutral dimers with aqueous acid gives [{Mo(η-C5H5)}2(µ-H)(µ-OH)(µ-η5-C5H4-η5-C5H4)][PF6]2. The red and yellow dimers react with iodine giving [{Mo(η-C5H5)I}2(µ-σ : η5-C5H4)2] and the corresponding reaction with the green dimer yields [{Mo(η-C5H5)I}2(µ-η5-C5H4-η5-C5H4)]. The red dimer also adds to methyl bromide giving [{Mo(η-C5H5)Me}{Mo(η-C5H5)Br}(µ-σ : η5-C5H4)2], whereas the yellow dimer reacts with methyl iodide to give [{Mo(η-C5H5)}2(µ-σ : η5-C5H4)2]. Photolysis of [W(η-C5H5)2H2] in diethyl ether gives cis- and trans-[{W(η-C5H5)H}2(µ-σ : η5-C5H4)2] and the cation [W(η-C5H5)2(η-C2H4)H]+. Thermal decomposition of [W(η-C5H5)2MeH] in cyclohexane gives isomers of the compound [{W(η-C5H5)2Me}{W(η-C5H5)H}-(µ-σ : η5-C5H4)2].

34 citations


Journal ArticleDOI
TL;DR: In this paper, the compounds [NbCl4(η-C5H4Me)L][L = MeCN, PhCN, P(OMe)3, or Ph2PCH2CH2PPh2(dppe) were used as starting materials.
Abstract: The compounds [SnBun3(σ-C5H4R)](R = H or Me) have been used to prepare the species [MCl4(C5H4R)](M = Nb or Ta, R = H or Me), [TaX2(η-C5H5)2](X = Cl or Br), and [NbCl2(η-C5H4Me)2] in very high yields. Using these compounds as starting materials the following products have been prepared [NbCl4(η-C5H4Me)L][L = MeCN, PhCN, P(OMe)3, or Ph2PCH2CH2PPh2(dppe)], [Ta(η-C5H5)2H3], and [Ta(η-C5H5)2Y2] where Y2=(SMe)2 or PhCH2Cl. Partial hydrolysis of [NbCl4(η-C5H4Me)] gives the compound [{NbCl3(η-C5H4Me)(OH2)}2O]. Reduction of [NbCl4(η-C5H5)] with [{AlEtCl2}2] in the presence of dppe gives [NbCl3(η-C5H5)(dppe)]·PhMe. This reduces with sodium amalgam in the presence of carbon monoxide giving [Nb(η-C5H5)(dppe)(CO)2] which protonates in acid giving [Nb(η-C5H5)(dppe)(CO)2H][PF6]. The compounds [Pt{Ta(η-C5H5)2(SMe)2}2][PF6]2 and [NbBr3(η-C5H5)(dppe)]·PhMe are also described.

31 citations


Journal ArticleDOI
TL;DR: In this article, photolysis of metallacyclobutane compounds yields olefins with fewer carbon atoms than in the initial METALACLOBUTANE system.

29 citations


Journal ArticleDOI
TL;DR: In this paper, the new compounds [Ta]Cl 2, [TaCl 2 ], [TaH 3 ], [ TaCl 2 ] and [TaMe(PMe 3 ], where [Ta = Ta(η-i-PrC 5 H 4 ) 2, are described.

28 citations


Journal ArticleDOI
TL;DR: In this paper, a number of general reactions of organometallic systems have been classified and entered in a computer program, and the use of the program is exemplified by generating possible mechanisms for the catalytic formation of butenes via ethylene dimerisation.

12 citations


Journal ArticleDOI
TL;DR: The first example of a zerovalent derivative of tantalum is the compound Ta(dmpe)3 as mentioned in this paper, which is derived from the metal Cr, Mo, W, V, Nb and Ta.

12 citations


Journal ArticleDOI
TL;DR: In this paper, cocondensation of cycloheptatriene with zirconium or hafnium vapours gives, after vacuum pyrolysis of the reaction mixture the diamagnetic d 2 compounds [m(η-C 7 H 7 ) (η − C 7 H 9 )].

10 citations


Journal ArticleDOI
TL;DR: In this paper, it was shown that the principal band with λ max at 570 nm has ϵ>9000 1 cm −1 mol −1 −1, and no evidence was found for the reversible formation of dioxygen-manganese complexes.

8 citations


Journal ArticleDOI
TL;DR: In this article, the new compounds Nb(η-C 5 H 5 )(dmpe)Cl 3, Nb[Nb[C5 H 5 ](DMpe)COCl 2, Nm[Nm]PF 6] were described.

7 citations


Journal ArticleDOI
TL;DR: In this paper, a cocondensation of niobium or tantalum atoms with an excess of butadiene and tetrahydrofuran yields diamagnetic, crystalline compounds M(η-MeC3H4)(η -C4H6)2, M = Nb or Ta.
Abstract: Cocondensation of niobium or tantalum atoms with an excess of butadiene and tetrahydrofuran yields the diamagnetic, crystalline compounds M(η-MeC3H4)(η-C4H6)2, M = Nb or Ta.

Journal ArticleDOI
TL;DR: In this paper, the authors describe the synthesis and reactions of bis-qcyclopentadienyl compounds of molybdenum and tungsten under the following headings: 1. The insertion of Tungsten and moly bdenum into aromatic and aliphatic C-H bonds; 2. The synthesis and reaction of tungstena-cyclobutane compounds; 3.
Abstract: It is nearly always very difficult to elucidate the intimate mechanism of hydrocarbon reactions catalyzed by transition metals, by direct study of the catalyst system. This is especially true for heterogeneous catalysts. However, it is a reasonable assumption that the nature of any transition metal intermediates in a complex catalytic cycle will find analogy with stable, isolable organo-transition metal compounds. Thus, information derived from a study of organometallic compounds and their reactions can assist the development of ideas about possible mechanisms for the catalytic reactions. In this paper we describe first the synthesis and some reactions of bis-qcyclopentadienyl compounds of molybdenum and tungsten under the following headings: 1. The insertion of tungsten and molybdenum into aromatic and aliphatic C-H bonds; 2. The synthesis and reactions of molybdenaand tungstena-cyclobutane compounds; 3. Evidence for a 1.2-hydrogen shift mechanism in some tungsten-alkyl compounds. We will then suggest how these observations may be relevant to the mechanisms of olefin metathesis, Ziegler-Natta catalysis, and related reactions.

Journal ArticleDOI
TL;DR: In this article, the mechanisms of photoinduced insertions of tungsten into aromatic and aliphatic C-H bonds are discussed, and the photoinduced reaction between [W(η-C5H5)2H2] and toluene, a to-luene-mesitylene mixture, and methyl propionate are also described.
Abstract: Photolysis of solutions of [W(η-C5H5)2H2] in fluorobenzene, o-xylene, anisole, p-chlorotoluene, p-xylene, mesitylene, p-methylanisole, and methyl benzoate gives the compounds [W(η-C5H5)2H(C6H4F-3 and -4)], [W(η-C5H5)2H(C6H3Me2-3,4)], [W(η-C5H5)2H(C6H4OMe-4)], [W(η-C5H5)2Cl(C6H4Me-4)], [W(η-C5H5)2(CH2C6H4Me-4)2], [W(η-C5H5)2(CH2C6H3Me2-3,5)2], [W(η-C5H5)2(CH2C6H4OMe-4)2], and [W(η-C5H5)2H(C6H4CO2Me-3 and -4)] together with [W(η-C5H5)2H(OCOPh)], respectively. Thermal decomposition of [W(η-C5H5)2H(Me)] in mesitylene gives [W(η-C5H5)2H(CH2C6H3Me2-3,5)]. Photolysis of this compound in p-xylene gives [W(η-C5H5)2(CH2C6H4Me-4)(CH2C6H3Me2-3,5)]. Photolysis of [W(η-C5H5)2H2] in tetra-methylsilane gives cis- and trans-[H(η-C5H5)W(σ: η5-C5H4)2W(η-C5H5)(CH2SiMe3)]. The photoinduced reaction between [W(η-C5H5)2H2] and toluene, a toluene–mesitylene mixture, and methyl propionate are also described. The mechanisms of these photoinduced insertions of tungsten into aromatic and aliphatic C–H bonds are discussed.