Carbonyl phosphines correlations

Several trinuclear iron carbonyl clusters have been subjected to a Fenske-Hall MO treatment by Buhl and co-workers. Hall has released details of the methodology for calculating potential energy surfaces for carbonyls, phosphines etc. using a variety of electron correlation techniques. 

The relatively basic (hydroxyalkyl)phosphines act toward LMCs as reductants and, compatible with this, also as strong nucleophiles. We have studied such reactions in aqueous and D2O solutions by P-, H-, and C-NMR spectroscopies (including 2D correlation methods), product isolation and, when possible, X-ray analysis of isolated compounds or their derivatives. Thus, aromatic aldehyde moieties present in lignin (e.g., 3) are reduced to the corresponding alcohols (see 4) with co-production of the phosphine oxide in D2O, -CH(D)OD is formed selectively (36). The mechanism proceeds via a phosphonium species formed by initial nucleophilic attack of the P-atom at the carbonyl C-atom, i.e., via ArCH(OH)P%, where Ar is the aromatic residue and R is the hydroxyalkyl substituent (36). When the aldehyde contains a 4-OH substituent, the alcohol product... 

Consideration of the relative donor abilities of nitrosyl, carbonyl, and phosphine groups as measured by their ionization potentials, provides an explanation for variations in the molecular ionization potentials of these complexes (103, 194). As shown in Table III (Section IX) the ionization potentials decrease on introduction of the phosphine ligand, and parallel the corresponding decrease in ionization potentials of the phosphine ligands. Similar correlations were made for vco and vNO in the infrared spectra. 

The enthalpy trend can be examined in terms of electronic and steric contributions to the enthalpy of reaction, the relative importance of which can be quantified in terms of the respective Ai /A2 ratios obtained in a treatment first proposed by Tolman, where enthalpies of reaction are correlated with steric (6, cone angle, see Tolman s Cone Angle) and electronic (v, carbonyl stretching frequency in Ni(CO)3L, L = tertiary phosphine) factors. A correlation factor of 0.95 is obtained when enthalpic data are fitted to equation (3) and a value of 2.32 is calculated for the A1/A2 and quantitatively denotes the overwhelming influence of steric factors. Since the steric factors have such a profound influence on the enthalpy of reaction, a direct relationship between the enthalpy of reaction and the phosphine cone angle can be established as shown in Figure 1. 

The ionization and oxidation (peak) potentials [53] of metal carbonyls listed in Table 3 establish their mild donicity despite their (formally) neutral oxidation state. However, partial replacement of carbonyls by stronger donor ligands (such as phosphine, sulfide, etc.) effects an incremental increase in their reducing properties [54], Such a fine-tuning of the oxidation potentials of structurally similar organometallic donors is ideal for studies of the correlation between rate constants and the electron-transfer driving force (see Section 2.5). 

Polyamides were successfully used as supports. Polyamides 14 and 15 were allowed to react with H2PtCl6, PtCl2(CH3CN)2, and [RhCl(CO)2]2 to give the corresponding immobilized catalysts. The IR study shows that the carbonyl oxygens of amides are the sites of coordination to platinum and rhodium. It was found that the activity of those immobilized catalysts correlates with the crystallinity of the polyamides, viz., the higher the crystallinity, the lower is the catalytic activity. Partial phosphination of 15 did not show any effects on catalytic activity. The polyamide-bound catalysts are thermally stable and reusable . 

The inversion of the triphenylphosphine ligand is effected through the twist of the P-Car axes ((04) by 90°. In our model the ortho-H atoms of the phosphine ligand and the terminal carbonyl ligands are in a complex bevel gear engagement in which a three-toothed wheel, the Co(CO)3 rotor is dragging three, two-toothed wheels (the phenyl rotors), or vice versa in a correlated... 

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