RING-OPENING AND EXTRUSION OF TELLURIUM ATOMS IN THE REACTION OF BENZO[B]TELLUROPHENE WITH TRINUCLEAR IRON, RUTHENIUM AND OSMIUM CLUSTERS -X-RAY CRYSTAL-STRUCTURES OF [OS-3(MU-C8H6TE)(CO)(10)], [OS-4(MU-C8H4)(MU(3)-TE)(CO)(11)], [RU-2(MU-C8H6TE)(CO)(6)], [RU-4(MU(3)-TE)(MU-C8H6)(CO)(11)] AND [FE-2(MU-C8H6TE)(CO)(6)]

The trinuclear carbonyl clusters [Fe-3(CO)(12)], [Ru-3(CO)(12)], [Os-3 (CO)(12)] and [Os-3(CO)(10)(MeCN)(2)] react with benzo [b] tellurophen e under mild conditions, in refluxing tetrahydrofuran, to give compoun ds containing the open-chain ligands C6H4CHCHTe or the fragments Te an d C8H6 as bridging ligands. The following compounds were isolated and characterised: [Os-3(mu-C8H6Te)(CO)(10)] (1), [Os-2(mu-C8H6Te)(CO)(6)] (2), [Os-2(mu-C8H6)(CO)(6)] (3) and [Os-4(mu-C8H6) (mu(3)-Te)(CO)(11) ] (4), which were obtained from the reaction of [Os-3(CO)(12)] and ben zo[b]tellurophene. [Ru-3(mu-C8H6)(CO)(8)] (5) (X-ray reported previous ly) [Ru-2(mu-C8H6Te)(CO)(6)] (6), [Ru-2(mu-C8H6)(CO)(6)] (7) and [Ru-4 (mu(3)-Te)(mu-C8H6)(CO)(11)] (8) were derived from the reaction of [Ru -3(CO)(12)] and benzo[b] tellurophene; [Fe-2(mu-C8H6Te)(CO)(6)] (9) an d [Fe-2(mu-C8H6)(CO)(6)] (10) were obtained from [Fe-3(CO)(12)]. All t he compounds were characterised by H-1 NMR and IR spectroscopy in solu tion and 1, 4, 6, 8 and 9 were characterised by X-ray diffraction meth ods in the solid state. All the clusters were shown to have had a Te-C bond broken to give the C6H4CHCHTe as a bridging ligand linking two m etal atoms. Cluster 8 was shown by single-crystal X-ray diffraction me thods to have had both TeC bonds broken to give a mu(3)-Te ligand and a C8H6 bridging ligand. This cluster contains a Te-capped triangle of ruthenium atoms and there is a spiked ruthenium atom supporting the br idging C8H6 ligand. In this case the Te atom has been extruded from th e heterocycle but remains in the cluster. Crystal data: 1: monoclinic, space group P2(1)/a, a=12.326(7), b=13.821(4), c=13.538(5) Angstrom, beta=107.01(3)degrees, Z=4; 4: monoclinic, space group P2(1)/n, a=16.7 40(2), b=8.684(3), c=18.536(4) Angstrom, beta=112.87(1)degrees, Z=4; 6 : monoclinic, space group P2(1)/a, a=12.291(3), b=12.098(5), c=22.880( 4) Angstrom, beta=95.24(2)degrees, Z=8; 8: monoclinic, space group P2( 1)/n, a=14.376(4), b=11.268(4), c=15.313(4) Angstrom, beta=96.27(2)deg rees, Z=4; 9: monoclinic, space group P2(1)/a, a=12.094(3), b=11.737(3 ), c=22.632(4) Angstrom, beta=96.66(2)degrees, Z=8. The structures wer e solved by direct methods and were refined by full-matrix least-squar es to R=0.0309, 0.0364, 0.0348, 0.0220 and 0.0410 for 4073, 3628, 3414 , 2005 and 4985 reflections with I>3 sigma(I), respectively.