Synthesis, crystal structure and absolute configuration of the menthylcyclopentadienyl complex of ruthenium (+)578-(η5-MCp)Ru(CO)P(C6H5)3Cl

The diastereoisomeric pair (+)578- and (-)578-(η5-MCp)Ru(CO)P(C6H5)3Cl (IIa and IIb) (MCp = (R)-(-)-menthylcyclopentadienyl) has been synthesized from (η5-MCp)Ru(CO)2Cl (I) by replacement of one of the two diastereotopic CO groups by P(C6H5)3 in refluxing xylene under nitrogen. Preparative TLC gave the two diastereoisomers optically pure. The structure of diastereomer IIa has been determined by single-crystal X-ray diffraction methods. The compound is orthorhombic, space group P212121 (No. 19) with a = 16.667(6), b = 22.287(8), c = 8.301(3) Å and Z = 4. The structure was solved by Patterson and Fourier methods, on the basis of 3046 significant counter reflections, and refined by block-matrix least-squares to a final conventional R value of 0.049. The configuration of IIa is S (based on Stanley and Baird sequencing rules). The exactly opposite and almost enantiomeric pattern of the CD spectra of IIa and IIb suggests an R configuration at ruthenium for complex IIb. © 1981.