Tetracarbonylcobaltate

DR. NORTON An excellent attempt to observe such hydrogen bonding was made recently by Fachinetti, et al. [Calderazzo, F. Fachinetti, G. Marchetti, F. Zanazzi, P. F. J. Chem. Soc., Chem. Commun. 1981, 181]. They took hydridocobalttetracarbonyl and triethylamine, and crystallized out a species which one can only describe as the tetracarbonylcobaltate of protonated triethylamine. They proposed some type of interaction between the hydrogen and a face of the cobalt tetrahedral complex, but it was clear that the interaction was almost entirely with nitrogens. The conclusion I would draw is that the complex appears to proceed directly to full protonation of the amine without any observable evidence for a hydrogen bonded intermediate. 

Scheme 31 illustrates, as an example, the Co2(CO)8-catalyzed carbonylative ring expansion of bicyclic aziridine 220, forming the corresponding highly strained /ra r-bicyclic /3-lactam 221, and a proposed reaction pathway. In this reaction, it is believed that tetracarbonylcobaltate, Co(CO)4, generated from Co2(CO)8 is the active catalyst... 

A quantity of solvent free kalium tetracarbonylcobaltate (1—) (2.0 g, 9.5 mmol) is dissolved in a 250-mL Schlenk flask in lOOmL of water, which... 

Several mixed-metal clusters containing platinum and cobalt are known and some of them have been employed as methanol homologation catalysts.1 Among them, the title compound2 was first prepared unambiguously from the reaction of dichloro[l,2-ethanediylbis(diphenylphosphine)]platinum with sodium tetracarbonylcobaltate, Na[CO(CO)4]. The compound also may be prepared by the reaction of [l,2-ethanediylbis(diphenyl-phosphine)]bis(phenylethynyl)pIatinum with Co COJg.1... 

Sodium tetracarbonylcobaltate(l —) is prepared from Co2(CO)g (0.6 g) and 3% of Na-Hg (15 g) in tetrahydrofuran (THF).8 Dichloro[l,2-ethanediylbis-(diphenylphosphine)]platinum (1.0 g, 1.5 mmol) is suspended in freshly distilled, dry, and oxygen-free THF (20 mL) in a 100-mL two-necked flask fitted with a refluxing condenser, a Teflon-coated magnetic stirring bar, and an inlet for nitrogen connected to a mercury or mineral oil bubbler for venting excess gases. 

The solution of tetracarbonylcobaltate(l —) is added dropwise at room temperature with stirring under nitrogen. The flask is then warmed to reflux... 

Tetracarbonylcobaltate(l-) ion Carbonyl (t)5-cyclopentadienyl)nitrosyl-[(trimethylphosphoranylidenelacetyl-KC lchromatel 1 -) ion Bis[tris( 1,2-ethanediamine-K2 N, N )cobalt(IIl)] tris[difluoro(oxa ato)dioxoiungstate(VI)]... 

The second possibly useful reaction in this group is the tetracarbonylcobalt anion-catalyzed conversion of alkyl halides with a base, CO, and conjugated dienes into acylated dienes (24). In this reaction the alkylcobalt intermediate... 

Of the homoleptic carbonylmetallates(l -) we have attempted to reduce, [Co(CO)4] appears to be the most difficult. Although the sodium salts of [M(CO)6] (M = V, Nb, and Ta) were quickly reduced in liquid ammonia by sodium metal to provide the corresponding trianions, [M(CO)5]3 (vide supra), it seems unlikely that we have ever effected complete reduction of Na[Co(CO)4] to Na3[Co(CO)3]. Even after 2 days of refluxing (at — 33°C) anhydrous ammonia solutions of Na[Co(CO)4] with excess Na, considerable amounts of the tetracarbonylcobaltate(l —) remained. Low yields of a heterogeneous-appearing brown to olive-brown insoluble solid were isolated this solid has been shown to contain Na3[Co(CO)3] (vide infra). As in the case of [Re(CO)s], we found that solutions of potassium in liquid ammonia were far more effective at reducing [Co(CO)4]-. However, unlike [Re(CO)s], [Rh(CO)4], or [Ir(CO)4] (vide infra), there was no evidence that [Co(CO)4] was reduced by sodium or potassium metal in hexa-methylphosphoric triamide. We observed that excess sodium naphthalenide slowly (over a period of 40-50 hr at room temperature) converted Na[Co(CO)4] in THF to an impure and insoluble brown powder that contained Na3[Co(CO)3], but this synthesis appeared to be of little or no utility. 

Tetrakis(2-methyltetrazol-5-yl)-hexaaza-l, 5-diene, 3008a 5,10,15,20-Tetrakis(2-nitrophenyl)porphine, 3901 Tetrakis(pentafluorophenyl)titanium, 3836 Tetrakis(pyrazole)manganese(II) sulfate, 3532 Tetrakis(pyridine)bis(tetracarbonylcobalt)magnesium, 3861 Tetrakis(thiourea)manganese(II) perchlorate, 1779... 

The origin of the charge-transfer absorptions of the colored salts in Table II are established by X-ray crystallography of the tetracarbonylcobaltate... 

The molecular (space-filling) models in Fig. 1 illustrate the location of the anionic donors I- and Co(CO)4- relative to the cobalticenium acceptor for optimal orbital overlap with the LUMO in the equatorial plane (34). For the pyridinium salts of Co(CO)4", the analogous charge-transfer interaction of the tetracarbonylcobaltate donor places it above the aromatic acceptor planes for optimal orbital overlap with the ti-LUMOs of Q+ and NCP+. Such X-ray crystallographic structures indicate that these charge-transfer salts consist of contact ion pairs that are directionally constrained for optimum CT interaction in the crystal lattice. 

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