RUTHENIUM INDUCED DEGRADATION OF TETRAMETHYLTHIOUREA TO CARBENE LIGANDS - SYNTHESIS AND MOLECULAR-STRUCTURE OF THE CLUSTERS RU4((MU-2-CO)2(CO)9-N(MU-4-S)2[C(NME2)2]N (N=1,2) AND (MU-2-H)RU3(CO)9[MU-3-SRU3(CO)3((ETA-2-CH2NMECNME2)]

Tetramethylthiourea was found to react with Ru3(CO)12 in refluxing THF to give sulphur- and diaminocarbene-containing clusters. The X-ray diffraction studies of the resulting clusters Ru4(mu-2-CO)2(CO)9-n(mu-4-S)2[C(NMe2)2]n (n = 2: 5; n = 1: 6) show square-planar metal frameworks, capped on both sides by mu-4-sulphido ligands. The diaminocarbene ligands in 5 are coordinated in a transoid fashion to two opposite ruthenium atoms of the metal square; cluster 6 can formally be derived from 5 by replacement of a diaminocarbene ligand by a carbonyl ligand. The X-ray analysis of a further product, the cluster (mu-2-H)Ru3(CO)9[mu-3-SRu(CO)3(eta-2-CH2NMeCNMe2)] (7), shows a ruthenium triangle capped by a mu-3-sulphido ligand. A fourth ruthenium atom, coordinated to sulphur, carries a eta-2-trimethylmethylenediaminocarbene ligand; the formation of this unusual four-membered metallacycle is caused by C-S and C-H activation of the tetramethylthiourea. Another reaction product is the light-sensitive complex (mu-2-H)RU3(CO)8(mu-3-S)(eta-2-CH2NMeCNMe2) (8) which contains a three-membered metal triangle, capped by a mu-3-sulphido ligand; as in 7, a eta-2-trimethylmethylenediaminocarbene ligand is coordinated to one of the ruthenium atoms. An isomer of 8, the cluster (mu-2-H)Ru3(CO)8(mu-3-S)(mu-2-eta-2-CH2NMeCNMe2) (9), in which the eta-2-trimethylmethylenediaminocarbene ligand bridges an edge of the ruthenium triangle, is also isolated from the reaction mixture.