Brian G. Gowenlock

The pyrolysis of organometallic compounds IV. Kinetic studies of the decomposition of tetramethylsilane

Abstract The pyrolysis of tetramethylsilane has been investigated in a flow system at 810–980°K and 0.1–30 mm. In reaction vessels seasoned by pyrolysis of tetramethylsilane the decomposition is independent of surface to volume ratio and the first-order rate constants may be represented by the equation: log 10 k (sec −1 ) = (14.30 ± 0.23) − (67600 ± 800)/(2.303 R · T ) The major products formed are methane, ethane, trimethylsilane, 1,1,3,3-tetramethyl-1,3-disilacyclobutane, hexamethyldisilane, and 2,2,4,4-tetramethyl-2,4-disilapentane. A reaction scheme is proposed which invokes the existence of a silicon—carbon π-bonded intermediate. In a reaction vessel seasoned by the pyrolysis of tetramethyltin, the decomposition of tetramethylsilane is heterogeneous, and certain products are obtained which indicate that rapid surface initiated rearrangement reactions are taking place.

The organometallic chemistry of the alkaline earth metals I. Some chemical and spectroscopic properties of dicyclopentadienylcalcium

Some properties of dicyclopentadienylcalcium have been investigated. The compound has been shown to form complexes with nitrogen or oxygen donor ligands of the general formula (C5H5)2CaL2 (where L=pyridine or L2= N,N,N′,N′- tetramethylethylenediamine, 2,2′-bipyridine or 1,2-dimethoxyethane). When L2= 1,10-phenanthroline a solvated complex (C5H5)2CaL2· n(tetrahydrofuran) or a complex of composition (C5H5)2Ca(L2)2· n(pyridine), n=0.5–2, is obtained. The 1H NMR and IR spectra of these products have been studied. Dicyclopentadienylcalcium has also been shown to be a useful cyclopentadienylating reagent, which readily forms cyclopentadienyl compounds on reaction with metal halides.

The organometallic chemistry of the alkaline earth metals. II. Calcium derivatives of indene, fluorene and phenyl-acetylene formed by metallation with triphenylmethyl-calcium chloride

Abstract Triphenylmethylcalcium chloride has been used in metalation reactions to prepare new organocalcium compounds. Metalation of indene leads to the isolable complexes (C9H7)2CaL2 (L = tetrahydrofuran or L2 = 1,2-dimethoxyethane) and sublimation of these complexes gives diindenylcalcium. (C9H7)2Ca. Similar metalation of cyclopentadiene occurs. Fluorene and phenylacetylene are metalated in tetrahydrofuran to give (C13H9)CaCl(THF)2 or (C6H5C2)CaCl-xTHF, respectively. IR and 1H NMR spectroscopic studies and other properties of the new products are discussed.

NO bond length/stretching frequency realtionships in C-nitroso compounds and their coordination complexes

The mode of coordination of monomeric C-nitroso compounds to metals is discussed. In contrast to previous studies it is proposed that an understanding of the v(NO)/r(NO) and r(CN)/r(NO) relationships in the non-coordinated nitrosocompounds is of primary importance for assesment of the coordination mode. It is concluded that both v(NO)/R(NO) and r(CN)/r(NO) have linear interrelationships in C-nitroso compounds that the coordination compounds of RNO have the same v(NO)/r(NO) relationship as the non-coordinated monomers. Previous correlations of Δv(NO) with coordination mode are therefore correlations of r(NO) with coordination mode. σ-N and σ-O complexes of aromatic RNO conform to the same R(CN)/r(NO) equation (within a very small error) as the non-coordinated monomers. The extent of deviation from the r(CN)/(r(NO) relationship for complexes of aliphatic RNO is of a similar order of magnitude to that which occurs when C-nitroso monomers form the trans-dimer. The coordination mode of aliphatic RNO is, with one exception, σ-N. Nitrosobenzene has a variety of coordination modes to transition metals but does not display σ-O coordination. p-Nitrosodimethylaniline undergoes σ-O coordination to d10 metals.

4-Iodonitrosobenzene. Structural and spectroscopic studies of the monomeric solid and of previously unreported dimers

4-Iodonitrosobenzene has been isolated as the (E)-azodioxy dimer for the first time. Its solid-state structure has been identified by X-ray crystallography and characterised by IR, MS and 13C NMR techniques. In CDCl3 or CD2C12 solution dynamic equilibria exist between monomeric 4-iodonitrosobenzene and its (Z)- and (E)-azodioxy dimers. Thermodynamic data (ΔG⊖, ΔH⊖ and ΔS⊖) for these equilibria have been calculated from low temperature 1H NMR spectra. Criteria for the dimerisation tendencies of all types of C-nitroso compounds are proposed.

Preparation an disolation of alkyliodostrontium and alkyliodobarium compounds

Alkyliodo-strontium and -barium compounds solvated by tetrahydrofuran RMI·(C4H8O)m, analogous to Grignard reagents, have been isolated and some of their properties and reactions are discussed.

Nitrosoarene complexes of rhodium(III), iridium(III), copper(I) and mercury(II). Use of XPS in determining the mode of bonding to transition metals

Abstract Some previously synthesized nitrosoarene complexes of known coordination mode have been studied by XPS spectroscopy. New nitrosoarene complexes of Rh III , Ir III , Cu I and Hg II have been synthesized and studied by both X-ray photoelectron and IR spectroscopy. A correlation was found between the value Δ E B (O-N) and the bonding mode of the nitroso ligand.

Coordination complexes of C-nitroso compounds. A 13C NMR study of some complexes of platinum with C-nitroso compounds

Abstract Three complexes of platinum with C -nitroso compounds have been studied by 13 C NMR spectroscopy. It has been shown that in all three cases there is a pronounced shift to higher frequency of C -NO and that for the two cases where this involves the t-butyl group the PtC coupling is evident. It is noted that this effect is stronger than for the coordination of some other ligands to platinum.

Gas phase reactions of sodium: IV. Rates of reaction of methylchlorogermanes and -stannanes

Abstract The rates of reaction with sodium atoms of the compounds Me 3 MCl and Me 2 MCl 2 (M = Ge, Sn) have been measured. The gradations in velocity constants along the Group IV series Me 3 MCl (M = C, Si, Ge, Sn) are discussed in terms of bond dissociation energies. It is concluded that the reaction rate of trimethylchlorostannane is high and reasons for this behaviour are discussed.

Coordination complexes of dimethyltin dichloride with C-nitroso compounds

Abstract Coordination complexes of five nitrosoanilines with dimethyltin dichloride have been prepared and studied by 13 C, 15 N and 199 Sn solid state NMR spectroscopy and by Mossbauer spectroscopy. The 13 C resonances of the C H 3 -Sn groups, the 199 Sn resonances and the Mossbauer quadrupole splitting values permit assignment of the two classes of coordination complexes. The C -NO resonances decrease on coordination. The 15 N resonances demonstrate that coordination is accompanied by an enhancement of the quinonoid contribution in the ligand itself