Carborane Complexes of Ruthenium: Reactions of [Ru(THF)(CO)2(η5-7,8-R2-7,8-C2B9H9)] (R = H or Me) with Alkylidyne Complexes of Molybdenum and Tungsten

The complex [Ru(THF)(CO) 2 (η 5 -7,8-C 2 B 9 H 11 )] ( 1a, THF = tetrahydrofuran) reacts with the alkylidyne reagents [M(⋮CC 6 H 4 Me-4)(CO) 2 (η 5 -C 5 H 5 )] (M = Mo or W) to give the compounds [MRu(μ-CC 6 H 4 Me-4)(CO) 4 (η 5 -7,8-C 2 B 9 H 11 )(η 5 -C 5 H 5 )] (M = W ( 2a ), Mo ( 2b )), which readily isomerize to the species [MRu(CO) 4 {σ,η 5 -9-CH(C 6 H 4 Me-4)-7,8-C 2 B 9 H 10 }(η 5 -C 5 H 5 )] (M = W ( 3a ), Mo ( 3b )). The structure of 3b was established by X-ray diffraction. The Mo(CO) 2 (η 5 -C 5 H 5 ) fragment is attached to the closo -RuC 2 B 9 framework by a Mo−Ru bond and a three-center two-electron B−H⇀Mo linkage involving a boron atom in an α site in the CC B BB 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 α site in the CCBB B ring. The oxo complex [WRuO{μ-σ,η 5 -9-CH(C 6 H 4 Me-4)-7,8-C 2 B 9 H 10 }(CO) 2 (η 5 -C 5 H 5 )] ( 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 {η 5 -9-CH(PMe 3 )(C 6 H 4 Me-4)-7,8-C 2 B 9 H 10 }(η 5 -C 5 H 5 )] (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-CH(PMe 3 )(C 6 H 4 Me-4)-7,8-C 2 B 9 H 10 group. The open C 2 B 3 face is pentacoordinated to the Ru atom, and there is an exopolyhedral B−H⇀W bond involving a B α atom in the CC B BB ring. The other B α site carries the CH(PMe 3 )(C 6 H 4 Me-4) substituent. Reactions between the ruthenium reagent [Ru(THF)(CO) 2 (η 5 -7,8-Me 2 -7,8-C 2 B 9 H 9 )] ( 1b ) and [W(⋮CC 6 H 4 Me-4)(CO) 2 (η 5 -C 5 H 5 )] gave [WRuO{μ-σ,η 5 -7,8-Me 2 -10-CH(C 6 H 4 Me-4)-7,8-C 2 B 9 H 8 }(CO) 2 (η 5 -C 5 H 5 )] ( 4b ), [WRu(μ-H){μ-η 5,η‘ 5 -7,8-Me 2 -9-C 5 H 4 -10-CH 2 (C 6 H 4 Me-4)-7,8-C 2 B 9 H 7 }(CO) 5 ] ( 6a ), and [WRu{μ-σ,η 5 -2,7-Me 2 -8-CH 2 (C 6 H 4 Me-4)-9-C(H)O-2,7-C 2 B 9 H 6 }(CO) 4 (η 5 -C 5 H 5 )] ( 7a ) that were separated by column chromatography. The corresponding reaction between 1b and [W(⋮CC 6 H 4 Me-2)(CO) 2 (η 5 -C 5 H 5 )] afforded [WRuO{μ-σ,η 5 -7,8-Me 2 - n -CH(C 6 H 4 Me-2)-7,8-C 2 B 9 H 8 }(CO) 2 (η 5 -C 5 H 5 )] ( n = 9 ( 4c ), 10 ( 4d )) and [WRu{μ-σ,η 5 -2,7-Me 2 -8-CH 2 (C 6 H 4 Me-2)-9-C(H)O-2,7-C 2 B 9 H 6 }(CO) 4 (η 5 -C 5 H 5 )] ( 7b ). Treatment of 1b with [Mo(⋮CC 6 H 4 Me- n )(CO) 2 (η 5 -C 5 H 5 )] ( n = 4 or 2) yielded [MoRu(μ-H){μ-η 5,η‘ 5 -7,8-Me 2 -9-C 5 H 4 -10-CH 2 (C 6 H 4 Me- n )-7,8-C 2 B 9 H 7 }(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(μ-H)Ru(CO) 2 unit is bridged by a 7,8-Me 2 -9-C 5 H 4 -10-CH 2 (C 6 H 4 Me-4)-7,8-C 2 B 9 H 7 moiety, a structure resulting from a linking of C 5 H 5 and nido -C 2 B 9 groups. The C 5 ring is η 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-CH 2 (C 6 H 4 Me-2)-9-C(H)O-2,7-C 2 B 9 H 6 cage system bridges the Ru−W bond with an η 5 -CB 4 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.