Carbonyl phosphination

Butynediol is more difficult to polymerize than propargyl alcohol, but it cyclotrimerizes to hexamethylolbenzene [2715-91 -5] (benzenehexamethanol) with a nickel carbonyl—phosphine catalyst (64) with a rhodium chloride—arsine catalyst a yield of 70% is claimed (65). 

With rare exceptions, such as [Fe(bipy)3]°, oxidation states lower than +2 are represented only by carbonyls, phosphines, and their derivatives. These will be considered together with other organometallic compounds in Section 25.3.6. 

Apart from Ru(CO)5 and other carbonyls, there are mixed carbonyl-phosphine species and a few simple phosphine complexes like Ru(PF3)5 and Ru[P(OMe)3]5 [61a]. 

A similar quantitative treatment of sulphoxides as hydrogen bonding acceptors has been obtained by comparing the IR frequency shift AvOH of the C—I bond in an acetylenic iodide such as IC=CI (Avc j) due to formation of a C—T complex with phenol in various bases. This investigation suggests that sulphoxides belong to the same family as carbonyls, phosphine oxides, arsine oxides and their derivatives90. 

To this category belong, e.g., homogeneous photocatalytic systems based on soluble metal complexes or organic dyes as photocatalysts. Instructive examples are photoreactions assisted by heteropolyacids (HPAs), transition meal complexes with carbonyl, phosphine or some other ligands, and metal porphyrins. 

The IR and XH-NMR spectral data for the various titanocene mono-carbonyl-phosphine complexes are compiled in Table III. Examination of the carbonyl stretching frequencies (Table III) nicely demonstrates the enhanced 7r-backbonding of the titanium center to CO as the -accepting ability of the phosphine ligand decreases. 

It should be noted that these results with the cobalt carbonyl phosphine catalysts may not apply over a wide range of conditions. At milder conditions of lower temperature and low catalyst concentration, the conversion of Co2(CO)8 to HCo(CO)3PR3 is only partially completed, even with up to 5/1 ratios of P/Co (22). 

This reaction occurs thermally in toluene at 30°C with an equilibrium constant (K) equal to 1.5 (13). Both bis(phosphine) and (carbonyl)phosphine Soret bands are present in the active catalyst solutions (see Decarbonylation Procedure), together with the unassigned, and likely critical, band at 420 nm. This could be due to some species giving rise to, or resulting from, a RuII + RCO reaction this is equivalent, of course, to a (Ru H-COR) acyl or a RuIII(C0)R (carbonyl)alkyl species, and the final elimination reaction after loss of CO could be written as ... 

A fairly large number of mixed carbonyl phosphine and arsine complexes have been reported so far. They are generally prepared by displacement of CO from Ni(CO)4. Owing to the high stability of Ni(CO)4, when it is reacted with phosphines and arsines at room temperature and atmospheric pressure, only a partial displacement of CO usually occurs. Most of the mixed phosphine (or arsine) carbonyl compounds have the general formula [Ni(CO) (PR3)4 ] (n = 3, 2) and [Ni(CO)2(L—L)] (L—L is a diphosphine or diarsine). These complexes are colourless or yellow-orange solids or liquids. Many of them are thermally stable but decompose in air. The most relevant mixed carbonyl complexes with common phosphines are reported in Table 4. 

Some of the mixed carbonyl phosphine complexes have been found to be efficient catalysts of oligomerization of alkanes. 

Table 4 Mixed Carbonyl Phosphine and Arsine Complexes...

Homogeneous Hydrogenation of Ketones Catalyzed by Cobalt Carbonyl Phosphine Complexes... 

Hydrido carbonyl phosphine complexes of the general formula CoH(CO)w-(PR3)4. are regarded as the catalysts in these reactions. The active species are probably hydrido complexes with lower coordination numbers formed by the loss of carbon monoxide or phosphine from these precursors. 

Compared with the analogous hydrogenation of aldehydes, the reaction requires somewhat more drastic conditions (about 200°C and 6 hrs), but the temperature is still within the stability range of the cobalt carbonyl phosphine complexes containing tertiary alkyl phosphines as ligands. If aryl phosphines are used, a more or less pronounced decomposition of the carbonyl complexes can be observed (as indicated by the IR... 

No detailed investigation of the reaction mechanism (kinetic measurements, etc.) was performed. The actual catalyst is probably the coordinatively unsaturated CoH(CO)2(PR3) species which may be formed by the loss of one ligand from both hydrido carbonyl phosphine complexes present in the reaction mixture ... 

The cobalt carbonyl phosphine complexes dissolved in the samples, and the products were detected by IR. Ketones, alcohols, and other organic components were determined after distillation (to eliminate cobalt) by GLC. 

The 31P NMR chemical shifts of compounds 36-38 are also in line with the expected trends previously reported for S P within group 6 metal carbonyl-phosphine complexes. The 31P NMR spectra of compound 38 also exhibit the tungsten (183W) satellites around the resonance of P-2 and the typical 1J P-W coupling constants for y/digated [W(CO)s]-phosphine complexes. 

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