BISBI ligands and the natural bite angle

Examination of molecular models of metal complexes of BISBI indicates that the chelate bite angle is much greater than 90°, the most common bite 

Hydroformylation of 1-hexene under mild conditions (34 C, 6 bar of syn gas, 4mM solution of 19)gave a l b ratio of 66.5 for BISBI and for trans-dppm-cyp it was 12. DIOP and dppe afforded values of 8.5 and 2.1. No isomerization was observed. It was concluded that apparently a bis-equatorial coordination of a diphosphine lead to high l b ratios, although the reason for this was not understood in detail. 

PhsP PPfi2 PhjF PPh2 PU P PPT2 bilcurijlo 113 107 102  

Ratio of diequatoriahapical-equatorial chelates of (diphosphine)Ir(CO)2H at room temperature. Mol heptanahmol 2-methylhexanal. Turnover rate = [mol aldehyde] x [mol 

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