Frank Bottomley

Organometallic Compounds Containing Oxygen Atoms

Publisher Summary This chapter discusses the organometallic compounds containing oxygen atoms. At present, the range of organic ligands found in organometallic oxo compounds is quite restricted, the majority being either η-C 5 R 5 or alkyls or aryls having no β-hydrogen atom. Two basic routes to organometallic oxo compounds may be envisaged addition of an organic ligand to an inorganic oxo complex or addition of oxygen to an organometallic compound. Exhaustive decarbonylation with concomitant oxidation of a cyclopentadienyl metal carbonyl has proved to be a useful preparative route to cyclopentadienyl metal oxo compounds having no other ligands. In the ethylene complex, the oxo and ethylene ligands are cis to one another and the C–C axis of the ethylene is perpendicular to the M–O bond, a configuration that maximizes π bonding between the W(IV) (d 2 ) and the ethylene. Complexes containing cyclopentadienyl and oxygen as coligands are of two basic types: those containing a terminal double bond between a metal and oxygen, [M=O], and those containing one or more doubly bridging oxygen atoms, [M(μ 2 -O) n M]. The clusters are held together by M–O bonds and the M–( η 5 -C 5 H 5 ) bonding is of the usual type. Parallel to the development of organometallic clusters containing oxygen atoms has been the preparation of organometallic polyoxometallates. Although the organometallic groups are on the surface of the polyoxometallate, they are strongly and covalently bonded to the peripheral oxygen atoms.

Reactions of Nitrosyls

Nitrosyls are complexes containing the nitrogen monoxide (NO) ligand. The oldest known nitrosyl is [Fe(CN)5(NO)]2−, first prepared by Playfair in 1849.1 Reactions of the coordinated NO ligand in this complex were first reported by Boedeker in 1861.2 Therefore, in both discovery and reactivity nitrosyls predate most other ligands including CO. These early beginnings were not followed by rapid growth; until the middle of the 1960’s progress in transition metal nitrosyl chemistry was mainly confined to three fronts. Firstly, the preparation of nitrosyls which were isoelectronic to known carbonyls was pursued. An example is [CO(CO)3(NO)], isoelectronic with [Ni(CO)4] and first prepared by Mond in 1922.3 Hieber and his coworkers prepared many compounds of this type. Apart from the occasional inexplicable presence of nitro (NO2) complexes in the reaction products, or the rare but equally mysterious loss of NO on treatment of the nitrosyl with a ligand,4 no reactions of the NO ligand were observed. Secondly, the preparation of nitrosyls of ruthenium, which date back at least to 1860,5 was continued. The names of Charonnat and Gleu are prominent in this work, which received a boost after 1945 from the discovery that ruthenium constituted a significant fraction of uranium fission products. Treatment of these products with nitric acid invariably yielded nitrosyls of ruthenium.

The reaction of scandium trifluoride with cyclopentadienyl salts and the crystal and molecular structure of the trimer of fluorodicyclopentadienylscandium

Abstract The reaction of ScF3 with (C5H5)2Mg gives a mixture of (C5H5)3Sc and (η5-C5H5)2ScF, not pure (C5H5)3Sc as reported previously. The same mixture is obtained on treating ScF3 with C5H5Na in tetrahydrofuran. The two products can be separated since (η-C5H5)2ScF is soluble in toluene whereas (C5H5)3Sc is not. The structure of (η-C5H5)2ScF shows it to be trimeric with a planar (ScF)3 ring (average ScF distance 2.046(8) A, FScF and ScFSc angles 86.5(3) and 153.4(4)°, respectively). Crystal data: monoclinic, Cc, a 17.019(8), b 15.273(7), c 10.359(8) A, β 92.33(5)°, Z = 4; Mo-Kα radiation, R = 0.076 for 1238 observed reflections and 325 variables.

An investigation of the MAM angle in compounds of general formula [MLn]2(μ-A)

The structures of 283 compounds of general formula [MLm](μ-A)[M′L′n] (M, M′ = d-or ƒ-block element, L, L′ = ligands0(s), A = p-block element) with respect to the MAM angle (θ). Molecular orbital (primarily extended Huckel) and statistical methods were used for the analysis. It is shown that compounds with 170 < θ < 180° are “linear”. For all [MLn]2(μ-A) compounds except [η-C5R5)2MLn2(η-A), the, MAM interaction consists of cylindrical symmetrical sets of π and δ-orbitals derived from the d-orbitals of the M atoms and the p-orbitals on the A atom. Free rotation of the two MLn units with respect to one another can occur to minimize steric repulsion across the MAM bridge. For [ML5]2(μ-A) compounds with 0–8 electrons on the two metal atoms, the θ angle is determined by intramolecular steric repulsion of the ML5

The crystal and molecular structure of μ-oxalatobis[di(η5-cyclopentadienyl)titanium]

Abstract μ-Oxalatobis[di-(η 5 -cyclopentadienyl)titanium], [μ-(C 2 O 4 ) {(η 5 -C 5 H 5 ) 2 Ti} 2 ], 0.5 (C 2 H 5 ) 2 O crystallises in the orthorhombic space group Pbcn with a 17.228(13), b 12.224(13), c 30.309(23) A and Z = 12. The final R was 0.061 ( R w 0.104). The oxalato group acts as a planar tetradentate bridging ligand, with the Ti atoms displaced in a cis fashion cut of the C 2 O 4 2− plane. The reason for this displacement is analysed in terms of σ and π interaction between the metal and ligand, and steric contacts between the Cp rings. Comparison with the iso-electronic [μ-{C 2 (N(C 6 H 4 CH 3 - p )) 4 } {(η 5 -C 5 H 5 ) 2 Ti} 2 ] is made.

Synthesis and structural characterisation of a novel paramagnetic trigonal bipyramidal cluster, (η5-C5H5)5 V5 O6

The reaction of N2O with (η5-C5H5)2V gives (η5-C5H5)5 V5O6, whose structure, determined by X-ray crystallography, shows a trigonal bipyramid of five V atoms, each capped by a (η5-C5H5) ring, with oxygen atoms bridging each of the six faces of the trigonal bipyramid.

Organometallic clusters containing oxygen atoms: (η-C5H5)5(O)V6(µ3-O)8 and {(η-C5H5)5V6(µ-3-O)8}2(µ-O), two further derivatives of octahedral (η-C5H5)6V6(µ3-O)8

Oxidation of (η-C5H5)2V with C5H5NO in toluene gives (η-C5H5)4V4(µ3-O)4 and (η-C5H5)5(O)V6(µ3-O)8(1) whereas oxidation with Me3NO gives {(η-C5H5)5V6(µ3-O)8}2{(µ-O)2V(η-C5H5)(NMe3)2} and {(η-C5H5)5V6(µ3-O)8}2(µ-O)(2); the structures of (1) and (2) have been established by X-ray crystallography.

Reactions of bis(η-cyclopentadienyl)vanadium derivatives with dinitrogen oxide (nitrous oxide)

The reaction between [V(cp)2(CO)] and N2O quantitatively gave [{V(cp)2}2n(CO3)n] where n= 1 or 2. This is analogous to the reaction of [Ti(cp)2(CO)2] with N2O which gave [{Ti(cp)2}4(CO3)2]. Derivatives of VIII such as [V(cp)2X](X = Cl or I) or [V(cp)2(CO)2]+ did not react with N2O, although [V(cp)2X] did react with O2. The oxidising properties of N2O are discussed, as are the properties of [{V(Cp)2}2n(CO3)n].

Organometallic oxides: Preparation of the heterometallic (cyclopentadienyl) titanium—molybdenum oxide cluster [(η-C5H5)Ti]2[(η-C5Me5)MoCl](μ2-O)3(μ3-O)

Abstract The reaction between (η-C5H5)2Ti(CO)2 and (η-C5Me5)MoCl(O)2 gave the heterometallic cluster [(η-C5H5)Ti]2[(η-C5Me5)MoCl](μ2-O)3(μ3-O) (1). The formula and structure of 1 were proven by microanalysis, high resolution mass spectrometry, 1H NMR and infrared spectroscopies. The two cluster electrons of diamagnetic 1 are localised in an orbital which is anti-bonding between the two titanium atoms.

Notes. Formation of carbonato and hydroxo complexes of vanadium(IV) on reaction of carbonylbis(η-pentamethylcyclopentadienyl)vanadium(II) with dinitrogen oxide

The reaction between [V(η-C5Me5)2(CO)] and N2O in toluene at 20 °C gave a mixture of the vanadium(IV) carbonate [V(η-C5Me5)2(CO3)] and a polymer proposed to be [{[{V(η-C5Me5)-(µ-O)}4(OH)2](µ-O)}n]. The reaction is compared with analogous ones of [V(η-C5H5)2(CO)] and [Ti(η-C5R5)2(CO)2](R = H or Me).