Associative Stereomutation of a Pentacoordinate Transition-Metal Complex: Access to the Required Octahedral Intermediate through Stereoselective CO Uptake at an Unsaturated Ruthenium(II) Center

Reaction of SiH(Me)(CH 2 CH 2 CH 2 PPh 2 ) 2 (i.e. “biPSiH”) with mer -RuH(PPh 3 ) 3 (CO)Cl affords the 5-coordinate Ru(II) monocarbonyl chloride Ru(biPSi)(CO)Cl ( 1 ), which adds CO to yield the 6-coordinate dicarbonyl analogue Ru(biPSi)(CO) 2 Cl ( 2 ). Stereoselective incorporation of 13 CO to give the labeled analogue 2* shows that on subsequent heating in refluxing toluene 1 is regenerated as a mixture of syn and anti diastereomers (ca. 3:1 ratio).