The cluster cis-[Re6Se8(PEt3)4I2] undergoes substitution reactions with neutral ligands L in the presence of AgSbF6 to afford the cis-disubstituted clusters [Re2Se8(PEt3)4L2] 2+(L = MeCN (6), t-BuCN, DMF, Me2SO (9)). Cluster 6 reacts with pyridine to give [Re6Se8(PEt3)4(py)2] 2+. Retention of stereochemistry was demonstrated from 31P NMR spectra and the crystal structure of (SbF6)2, which revealed the two Me2SO ligands to be O-bonded at adjacent Re sites of the face-capped octahedral [Re6(μ-Se)8]2+ core. The clusters cis-[Re6Se8(PEt3)4L 2]2+ are of interest as possible precursors to oligomeric clusters under thermolysis conditions where one or both ligands L are removed. Thermolysis of orange-red (SbF6)2 (180°C, 24 h) afforded a brown-green crystalline product identified by an X-ray structure determination to contain the dicluster [Re12Se16(PEt3)8(MeCN) 2]4+ (11). Two [Re6Se8]2+ cluster units are bridged by a Re2Se2 rhomb to afford the centrosymmetric core [Re12(μ3-Se)14(μ4Se) 2]4+, established recently for the dicluster [Re12Se16(PEt3)10]4+. The two acetonitrile ligands occur in a trans orientation on the two cluster units. From consideration of the crystal structure of the precursor compound (SbF6)2 (reported earlier), the relative orientation of cluster pairs could be responsible for the formation of trans11. Diclusters of the type cis-[Re12Se16(PEt3)8L 2]4+ are required for potential thermolytic conversion to the cyclic tetracluster [Re24Se32(PEt3)16]8+. Factors relevant to the formation of this unknown cluster type are considered.
|Original language||English (US)|
|Number of pages||6|
|State||Published - Dec 1 1997|
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry