SYNTHESIS AND ELECTRONIC-STRUCTURE OF RIGID-ROD OCTAHEDRAL RU-SIGMA ACETYLIDE COMPLEXES

Syntheses of the mono-, bis- and poly-nuclear Ru-sigma-acetylide complexes, trans-[RU(CO)2(PnBu3)2(-C=C-C6H5)2], trans-[ClRu(CO)2(PnBU3)2-C=C-p-C6H4-C6H4-p-C=C-Ru(CO)2(PnBu3)2Cl] and trans-[-Ru(CO)2(PnBu3)2-C=C-R-C=C-]n (R=P-C6H4, P-(CH3)2C6H2) are reported. A study of the electronic structure of model metal-acetylide complexes of Group 8, M(L)2(L')2(RH)2, ClRu(L or L')4-R-Ru(L or L'),Cl, [M(PH3)4(RH)]2R and [M(L)(L)2(R)]n (M=Fe, Ru; L=L'=PH3, PMe3; L=CO, L'=PH3; R=-C=C-, -C=C-C6H4-C=C-, -CH=CH-p-C6H4-CH=CH-) has been carried out using the Fenske-Hall molecular orbital model. These results and a comparison of the IR (nu(C=C) stretching frequencies) and optical absorption (pi-pi* energy band gap) spectra of these complexes provide evidence for the role of (i) auxiliary ligands, (ii) metal, and (iii) the bridging alkyne units in determining the extent of pi-electron conjugation in the backbone of these rigid rod organometallic complexes.