SUPPRESSION OF CLUSTER UNSATURATION BY FORMATION OF EXTENSIVE BUT LONG-RANGE METAL METAL-BONDING - CRYSTAL-STRUCTURES OF [RU3H(PYS)(CO)9] AND [(RU3H(PYS)(CO)7)3], WHERE PYS IS THE PYRIDINE-2-THIOLATO LIGAND

The cluster [Ru3(CO)12] reacts with 1 mol equiv of pyridine-2-thiol (pySH) in refluxing cyclohexane to give the yellow cluster [Ru3(mu-H)(mu3-pyS)(CO)9] (1). Crystals of 1 are monoclinic, of space group P2(1)/c, with a = 9.171 (2) angstrom, b = 14.986 (5) angstrom, c = 15.094 (5) angstrom, beta = 107.14 (2)-degrees, and Z = 4., The pyS ligand of 1 bridges two Ru atoms through the S atom and bonds to the third Ru atom through the pyridine ring. The cluster doubly decarbonylates and trimerizes in refluxing cyclohexane to give the dark red crystalline product [{Ru3(mu3-H)(mu4-pyS)(CO)7}3] (2). Crystals of 2 are trigonal, of space group P3c1, with a = 22.401 (4) angstrom, c = 17.271 (3) angstrom, and Z = 6. There are three independent Ru9 molecules in the unit cell, two of which are structurally equivalent. Each molecule contains three symmetry-related RU3 clusters linked by an Ru3S3 ring in a chair conformation and has an overall screw arrangement. Each mu4-pyS ligand is bonded as in 1 within its Ru3 unit but is further bonded through the S atom to one Ru atom of an adjacent Ru3 unit. One independent molecule has a right-handed screw, while the other is left-handed. The formation of three Ru-S bonds per molecule in the formation of 2 is insufficient to give saturation; this is achieved by the formation of six long-range contacts (3.2-3.3 angstrom) between the RU3 units. Attempts to add CO to cleave these long-range Ru-Ru bonds while maintaining the integrity of the Ru9 molecule led to complete carbonylation back to cluster 1.