Carborane complexes of ruthenium: Reactions of [Ru(THF)(CO)(2)(eta(5)-7,8-R(2)-7,8-C2B9H9)] (R=H or Me) with alkylidyne complexes of molybdenum and tungsten

The complex [Ru(THF)(CO)(2)(eta(5)-7,8-C2B9H11)] (1a, THF = tetrahydrofuran) reacts with the alkylidyne reagents [M(=CC(6)H(4)Me-4)(CO)(2)(eta(5)-C5H5)] (M = MO Or W) to give the compounds [MRu(mu-CC(6)H(4)Me-4)(CO)(4)(eta(5)-7,8-C2B9H11)(eta(5)-C5H5)] (M = W (2a), Mo (2b)), which readily isomerize to the species [MRu(CO)(4){sigma,eta(5)-9-CH(C(6)H(4)Me-4)-7,8-C2B9H10}(eta(5)-C5H5)] (M = W (3a), Mo (3b)). The structure of 3b was established by X-ray diffraction. The Mo(CO)(2)(eta(5)-C5H5) fragment is attached to the closo-RuC2B9 framework by a Mo-Ru bond and a three-center two-electron B-H-Mo linkage involving a boron atom in an a site in the CCBBB ring ligating the ruthenium. The CH(C(6)H(4)Me-4) moiety bridges between the Ru(CO)(2) group and the B atom located in the other a site in the CCBBB ring. The oxo complex [WRuO{mu-sigma,eta(5)-9-CH(C(6)H(4)Me-4)-7,8-C2B9H10}(CO)(2)(eta(5)-C5H5)] (4a) is a side product in the formation of 3a, and it also was characterized by X-ray diffraction. Treatment of the species 3 with PMe(3) affords the zwitterionic compounds [MRu(CO)(4){eta(5)-9-CH(PMe(3))(C(6)H(4)Me-4)-7,8-C2B9H10}(eta(5)-C5H5)](M = W (5a), Mo (5b)). A single-crystal X-ray diffraction study of 5a revealed that the (OC)(2)W-Ru(CO)(2) unit is bridged by the nido-9-CK(PMe(3))(C(6)H(4)Me-4)-7,8-C2B9H10 group. The open C2B3 face is pentacoordinated to the Ru atom, and there is an exopolyhedral B-H -->-W bond involving a B-alpha atom in the CCBBB ring. The other B-alpha site carries the CH(PMe(3))(C(6)H(4)Me-4) substituent. Reactions between the ruthenium reagent [Ru(THF)(CO)(2)(eta(5)-7,8-Me(2)-7,8-C2B9H9)] (1b) and [W(=CC(6)H(4)Me-4)(CO)(2)(eta(5)-C5H5)] gave [WRuO{mu-sigma,eta(5)-7,8-Me(2)-10-CH2(C(6)H(4)Me-4)-7,8-C2B9H8}(CO)(2)(eta(5)-C5H5)] (4b), [WRu(mu-H){mu-eta(5),eta'(5)- 7,8-Me(2)-9-C5H4-10-CH2(C(6)H(4)Me-4)-7,8-C2B9H7}(CO)(5)](6a), and [WRu{mu-sigma,eta(5)-2,7-Me(2)-8-CH2(C(6)H(4)Me-4)-9-C(H)O-2,7-C2B9H6}(CO)(4)(eta(5)-C5H5)] (7a) that were separated by column chromatography. The corresponding reaction between 1b and [W(=CC(6)H(4)Me-2)(CO)(2)(eta(5)-C5H5)] afforded [WRuO{mu-sigma,eta(5)-7,8-Me(2)-n-CH(C(6)H(4)Me-2)-7,8-C2B9H8}(CO)(2)(eta(5)-C5H5)] (n = 9(4c), 10(4d)) and [WRu{mu-sigma,eta(5)2,7-Me(2)-8-CH2(C(6)H(4)Me-2)-9-C(H)O-2,7-C2B9H6}(CO)(4)(eta(5)-C5H5)](7b). Treatment of 1b with [Mo(=CC(6)H(4)Me-n)(CO)(2)(eta(5)-C5H5)] (n = 4 or 2) yielded [MoRu(mu-H){mu-eta(5),eta'(5)-7,8-Me(2)-9-C5H4-10-CH2(C(6)H(4)Me-n)-7,8-C2B9H7}(CO)(5)] (n = 4 (6b), 2 (6c)). The structures of 4b, 6b, and 7b were established by X-ray diffraction. In 6b, the (OC)(3)Mo(mu-H)Ru(CO)(2) unit is bridged by a 7,8-Me(2)-9-C5H4-10-CH2(C(6)H(4)Me-4)-7,8-C2B9H7 moiety, a structure resulting from a linking of C5H5 and nido-C2B9 groups. The C-5 ring is eta(5)-coordinated to the molybdenum, while the open CCBBB face of the carborane cage is similarly attached to the ruthenium. In complex 7b, a nido-2,7-Me(2)-8-CH2(C(6)H(4)Me-2)-9-C(H)O-2,7-C2B9K6 cage system bridges the Ru-W bond with an eta(5)-CB4 ring coordinated to the Ru atom and with the cage joined to the W atom by a B-W bond. In addition, the C(H)O group forms a second bridge linking the cage to the tungsten, with the latter coordinated by the formyl O atom.