Two-electron Ligands Research Articles

Preparation of heterometallic binuclear complexes of transition metals from metallocenyl thioketones

1. Metallocenyl thioketones of the ferrocene and cymantrene series are capable of replacing the CO ligands in transition metal complexes and function as two-electron ligands to give donor-acceptor bonds of the sulfur atom with the transition metals (S→M). The reaction was used to synthesize some heterometallic binuclear complexes. 2. We obtained and characterized eight new heterometallic binuclear complexes with metallocenyl thioketones and two mononuclear complexes with Michler's thioketone and 4-p-tolyl1,2-thiol-3-thione as the η2-ligands.

Photolysereaktionen mit Komplexen des Typs CpFe(CO)2R (R = Me, Et, Ph)+ / Photolytic Reactions with Complexes of the Type CpFe(CO)2R (R = Me, Et, Ph)+

Photolysis of CpFe(CO)2R complexes [R = Me (1a), Et (1b), Ph (1c)] in hydrocarbon solvents results in loss of the group R and formation of the binuclear compound [CpFe(CO)2]2 (2). In the case of 1a, the photogenerated methyl group reacts to give methane by intramolecular hydrogen abstraction from the Cp ring, or by intermolecular hydrogen abstraction either from the solvent or another methyl group. The photoinduced dealkylation of the ethyl compound 1b is explained by β-elimination (to give ethylene) and subsequent reaction of the hydrido intermediates thus formed with unchanged 1b (to give ethane). The photolysis of 1c leads to phenyl groups which abstract hydrogen from the solvent to give benzene; a noticeable amount of diphenyl is also observed if benzene is used as a solvent. In the presence of potential two-electron ligands L [L = PMe3, P(OMe)3], only the carbonyl groups of CpFe(CO)2Me (1a) are photolabile, and substituted derivatives of the type CpFe(CO)(L)Me [L = PMe3 (3a), P(OMe)3 (4a)] and CpFe(L)2Me [L = P(OMe)3 (5a)] are formed. The photoinduced reaction of CpFe(CO)2Me (1a) and diphenylacetylene in solution gives metallocyclic derivatives containing either one or two diphenylacetylene units. On the basis of the IR, the 1H and 13C NMR, and the mass spectra, the complex CpFe(CO)(Ph2C2-COMe) (6a) is assigned a structure containing a vinyl-ketone unit in a five-membered metallocycle, while in CpFe(Ph4C4-COMe) (7a) a tetraphenylbutadienyl group appears to be incorporated into a seven-membered metallocycle

π-Complexes as ligands in transition metal compounds : I. π-Pyrrolyltricarbonylmanganese, a new two-electron ligand

It has been established that the nitrogen atom in π-pyrrolyltricarbonylmanganese can form a donor—acceptor bond with transition metals. This property was used to synthesize novel binuclear complexes in which a pyrrolyl ring performs two functions: a π-ligand to the manganese atom and an n-ligand to another metal.

Cyclopentadienyl-carbonyl-acetylen-methyl-wolfram, eine ausgangsverbindung für neue wolfram—acetylen-komplexe

The photochemical reaction of C 5H 5W(C0) 3CH 3 (I) with acetylene (C 2H 2) in solution leads to the formation of the diamagnetic complexes C 5H 5W(CO) 2-(C 2H 2COCH 3) (II) and C 5H 5W(CO)(C 2H 2)CH 3 (III). The adduct II contains a methylvinylketone ligand, in which the C 2H 2 unit is a σ-bonded olefin. The 16 electron system III, however, contains a mobile π-bonded C 2H 2-ligand. III reacts readily with two-electron ligands L; as examples the reactions with carbon monoxide, trimethylphosphite and trimethylphosphane are described. In the new π-acetylene complexes the C 2H 2 ligand shows a hindered rotation around the metal-C 2H 2 bond axis. The free activation enthalpies of the acetylene rotation are surprisingly high (e.g. for C 5H 5W(CO)(C 2H 2)CH 3 ΔG† 364 18.2 kcal mol -1, indicating strong metal→acetylene backbonding.

Photochemistry of (η-cyclopentadienyl)nitrosylnickel in frozen gas matrices at 20 K. Infrared spectroscopic evidence for mono- and di-carbonyl(η-cyclopentadienyl)nickel in carbon monoxide matrices and for a species formed by photoionisation or photoelectron transfer in inert matrices

Infrared evidence, including 13CO data, is presented for the formation of [Ni(η-C5H5)(CO)], [Ni(η-C5H5)(CO)2], and ultimately [Ni(CO)4] on the u.v. photolysis of [Ni(η-C5H5)(NO)] in CO or mixed CO and ‘inert’(nitrogen, argon) matrices at 20 K. Infrared evidence, including 15NO data, is also presented for the formation of a species [Ni(η-C5H5)(NO*)][the asterisk denotes a nitrosyl group with an unusually low value of ν(NO)] on photolysis of [Ni(η-C5H5)(NO)] in argon, methane, and nitrogen matrices at 20 K. The significance of the low value of ν(NO) for [Ni(η-C5H5)(NO*)] is discussed in terms of either photoionisation, i.e. formation of an ion pair [Ni(η-C5H5)]+NO–, or photoelectron transfer, i.e. the nitrosyl group acting as a one- or two-electron ligand instead of a three-electron ligand. It is concluded that [Ni(η-C5H5)(NO*)] belongs to a class of complexes in which electron transfer from the metal to the nitrosyl ligand is particularly extensive and bending of the M–N–O group may be involved. A convenient photochemical synthesis of [Ni(η-C5H5)(15NO)] is described.