Xantphos ligands tunable bite angles

Conditions CO/H2 = 1, P(CO/H2) = 20 bar, ligand/Rh = 5, substrate/Rh = 637, [Rh] = 1.00 mM, number of experiments = 3. In none of the experiments was hydrogenation observed. Linear over branched ratio, percentage linear aldehyde, percent isomerization to 2-octene, and turnover frequency were determined at 20% alkene conversion. Turnover frequency = (mol of aldehyde) (mol of Rh)-1 h-1. Calculated from Jp-h NMR data. 

During hydroformylation the IR spectra of the rhodimn species (diphosphine)Rh(CO)2H for ligands 37, 29, and 41 do not change. The respective ee ae equilibria are not influenced, and no other carbonyl complexes are observed. 

DPT calculations. The enhanced preference of the basic phosphines for apical coordination and the preference of the nonbasic phosphines for equatorial coordination was demonstrated by DFT calculations on the ee and 

Hydroformylation results in Table 6 show that, with the exception of ligands 39 and 40, the rate of the reaction increases with decreasing phosphine basicity. An explanation for the deviant behavior of 39 and 40 can be incomplete catalyst formation or deactivation of the catalyst. Decreasing phosphine basicity facilitates CO dissociation from the (diphosphine)Rh(CO)2H complex and enhances alkene coordination to form the (diphosphine)Rh(CO)H(alkene) complex, and therefore, the reaction rate increases. 

The constant selectivity for linear aldehyde in the hydroformylation of 1 -octene implies that for the basic ligands the l b ratio reflects the regioselectivity of the formation of the rhodium alkyl species. For the less basic ligands the increase in 1 b ratio results from the different behavior of branched and linear rhodium alkyls toward -hydrogen elimination, as was already reported by Lazzaroni and co-workers for the deuteriofomylation of 1-hexene [57]. The linear alkyl is mainly converted to linear aldehyde, while 

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