Synthesis, Structure, and Ligand Dynamics of the Organometallic Anion [Ru<inf>3</inf>(CO)<inf>9</inf>C<inf>2</inf>-t-Bu]^-

Abstract

The organometal cluster HRu3(CO)9C2-t-Bu (I) can be readily deprotonated by OH- in carbon monoxide atmosphere to yield the corresponding anion, isolated as [AsPh4]+[Ru3(CO)9C2-t-Bu]- (II). The variable-temperature 13C NMR spectrum of II in the carbonyl region reveals that the barrier to axial-radial exchange at the metal atoms formerly bridged by the hydrogen is lowered by 5 kcal/mol compared with the same process in I. The barrier to intermetallic scrambling is also lower. Crystals of II are monoclinic, space group P21/a with Z = 4 in a unit cell of dimensions a = 21.384 (15) Å, b = 18.775 (12) Å, c = 10.010 (8) Å, and β = 96.77 (7)°. The structure has been solved from diffractometer data by Patterson and direct methods and refined by full-matrix least-squares to R = 0.066 for 2741 observed reflections. The basic features of the triangular cluster and the organic ligand in II are maintained virtually unchanged from I, but the metal-metal bond formerly bridged by hydrogen is 0.127 Å shorter that in I. In addition, the three carbonyl groups on these metal atoms have undergone a rotation around the metal-metal bond which corresponds to relief of the steric hindrance caused by the hydride ligand. © 1981, American Chemical Society. All rights reserved.