TRINUCLEAR CLUSTERS OF RUTHENIUM-CONTAINING BRIDGING AND ORTHO-METALATED 2,2'-BIS(DIPHENYLPHOSPHINO)-1,1'-BINAPHTHYL (BINAP) - X-RAY STRUCTURES OF (R)-BINAP AND [RU-3(MU-OH)(2)(CO)(8)(MU-(R)-BINAP)]

The cluster [Ru-3(CO)(12)] normally reacts readily with tertiary phosp hines and diphosphines in the presence of Me3NO to give simple phosphi ne-substituted derivatives by a reaction involving nucleophilic attack of the amine oxide at CO leading to CO2 formation. However, the corre sponding reaction of [Ru-3(CO)(12)] with (R)-BINAP [2,2'-bis(diphenylp hosphino)-1,1'-binaphthyl] in the presence of Me3NO does not give [Ru- 3(CO)(10)(BINAP)], as expected, but instead an 80% yield of the dihydr oxy complex [Ru-3(mu-OH)(2)(CO)(8){mu-(R)-BINAP}] (1) as the first exa mple of a mu-BINAP complex. NMR coalescence effects are observed in th e H-1 NMR spectra, but by using a (CO)-C-13-enriched sample, we were a ble to show that the fluxionality is not cluster-centered since the C- 13{H-1} NMR spectrum for the CO ligands is invariant over a wide tempe rature range. COSY spectra were used to show that there is restricted rotation about two of the four P-Ph bonds while the other two are rota ting freely. From a single-crystal XRD study it can be seen that two P h groups are unimpeded while the other two are closely aligned to the naphthyl rings in a graphitic manner and it is this that leads to the restricted rotation. This bridging ligand adopts quite a different con formation about the C-PPh2 bonds to that in free BINAP, the structure of which was also determined for comparison, and somewhat different fr om that in known chelating BINAP complexes. In contrast, the direct th ermal reaction of (R)-BINAP with [Ru-3(CO)LSI in octane gives, in addi tion to traces of two uncharacterized species, a 38% yield of the clus ter [Ru-3(mu-H){mu-(R)-BINAP-H}(CO)(9)] (2), in which we believe that ortho metalation has occurred at one of the four Ph rings to form the first example of a cyclometalated BINAP ligand. We have been unable to obtain simple derivatives such as [Ru-3(CO)(11)(BINAP)] or [Ru-3(CO)( 10)(BINAP)], although we have shown that the osmium analogues may be s ynthesized.