SYNTHESIS AND CRYSTAL-STRUCTURE OF THE NOVEL PLATINUM-BRIDGED HEXARUTHENIUM ALKYNYL CLUSTER PT[RU3(MU-H)(MU-4-ETA-2-C=C(T-BU))(CO)9]2 - EVIDENCE FOR THE RACEMIZATION OF THE CHIRAL METAL FRAMEWORK

The cluster Ru3Pt(µ-H){µ4-η2-C≡C(t-Bu)}(CO)9(COD) decomposes in dichloromethane or toluene solution by elimination of a Pt atom and COD, affording orange crystals of the title complex Pt[Ru3(µ-H){µ4- η2-C≡C(t-Bu)}(CO)9]2 (5) in 40-50% yield. Crystal data for 5: triclinic, space group PĪ; a = 9.546 (2), b = 12.993 (2), c = 17.786 (2) Å; α= 72.97 (1), β = 82.48 (1), γ = 74.62 (2)°; V = 2030.4 (6) Å3; Z = 2; final R (Rw) values 0.033 (0.038) for 4806 independent observed (I > 3.0σ(I)) datA. C.omplex 5 contains two Ru3 cluster units linked by a “naked” Pt atom, with each cluster unit bonded via one Ru atom and the α-carbon of the alkynyl ligand. Variable-temperature13C NMR spectra show that the chiral metal framework undergoes racemization with an estimated ΔG*266 of 57.1 (±1.1) kJ mol-1. © 1990, American Chemical Society. All rights reserved.