CARBORANE COMPLEXES OF RUTHENIUM - STUDIES ON THE CHEMISTRY OF THE RU(CO)(2)(ETA(5)-7,8-C2B9H11) FRAGMENT

Treatment of [Ru(CO)(3)(eta(5)-7,8-C2B9H11)] (1) with Me(3)NO in THF ( tetrahydrofuran) affords [Ru(CO)(2)(NMe(3))(eta(5)-7,8-C2B9H11)] (3b), while the salt [NEt(4)][RuI(CO)(2)(eta(5)-7,8-C2B9H11)] (2) reacts wi th NCMe in the presence of AgBF4 to give [Ru(CO)(2)(NCMe)(eta(5)-7,8-C 2B9H11)] (3c). Related complexes [Ru(CO)(2)(L)(eta(5)-7,8-C2B9H11)] (L = CNBu(t) (3d), PPh(3) (3e)) are obtained by displacement of THF from [Ru(CO)(2)(THF)(eta(5)-7,8-C2B9H11)] (3a) with CNBu(t) and PPh(3), re spectively. Alkenes and 3a afford the complexes [Ru(CO)(2)(alkene)(eta (5)-7,8-C2B9H11)] (alkene = C2H4 (4a), MeCH=CH2 (4b), Me(3)SiCH=CH2 (4 c), and C7H10 (norbornene) (4d)), whereas alkynes RC=CR (R = Me, Ph) g ive the species [Ru(CO)(2)(RC=CR)(eta(5)-7,8-C2B9H11)] (R = Me (5a), P h (5b)). The reaction of complex 5a with K[BH(CHMeEt)(3)], in Et(2)O s olution, followed by addition of 18-crown-6, gives the salt n-6)][Ru{C (Me)=C(H)Me}(CO)(2)(eta(5)-7,8-C2B9H11)] (6), while PPh(3) in CH2Cl2 a ffords the ylide complex [Ru(C(Me)=C(Me)PPh(3))(CO)(2)(eta(5)-7,8-C2B9 H11)] (7) Reactions between 3a and the alkynes RC=CH (R = Bu(t), SiMe( 3)) yield a variety of products, in all of which the carborane ligand adopts a nonspectator role. Complex 3a and 1 mol equiv of Bu(t)C=CH gi ves a mixture of isomers O)(2)(eta(2):eta(5)-9-C(H)=C(H)Bu(t)-7,8-C2B9 H10)] (8a) and )(2)(eta(2):eta(5)-10-C(H)=C(H)Bu(t)-7,8-C2B9H10)] (8b) . An X-ray diffraction study on 8a revealed that the ruthenium atom is eta(5)-coordinated by the open CCBBB face of the nido-C2B9 cage and b y the C=C bond of the BCH=C(H)Bu(t) group. The reaction between 3a and 1 mol equiv of Me(3)SiC=CH is more complex due to SiMe(3) group cleav age. Isomeric mixtures of Ru(CO)(2)(eta(2):eta(5)-9-C(H)=C(H)R-7,8-C2B 9H10)] (R = H (9a), SiMe(3) (10a)) and [Ru(CO)(2)(eta 2:eta(5)-10-C(H) =C(H)R-7,8-C2B9H10)] (R = H (9b), SiMe(3) (10a)) are obtained. Additio n of PMe(2)Ph in heptane to 9b gives 2)(sigma,eta(5)-10-C(H)(PMe(2)Ph) CH2-7,8-C2B9H10)] (11b), the ylide structure of which was confirmed by X-ray crystallography. The Ru(CO)(2) fragment is Linked to the nido-C 2B9 cage system by eta(5) bonding to the CCBBB face and by a Ru-CH2 si gma-bond to the CH2C(H)(PMe(2)Ph)B fragment. Reactions between 3a and RC=CH, employing an excess of the latter, give the compounds (2):eta(5 )-9-C(H)=C(H)R-10,11-[C(H)=C(H)R](2)-7,8- C2B8}] (R = Bu(t) (12a), SiM e(3) (12b)) in which all boron atoms in the open CCBBB face of the cag e bonded to the ruthenium carry C(H)=C(H)R substituents. Treatment of the complexes 12 with PMe(3) yields respectively 2)(PMe(3)){eta(5)-9,1 0,11-[C(H)=C(H)Bu(t)](3)-7,8- C2B9H8}] (13) and gma,eta(5)-9-C(H)(PMe( 3))C(H)SiMe(3)-10,11-[C(H)=C (H)SiMe(3)](2)-7,8-C2B9H8}] (14). The str ucture of 13 was established by X-ray diffraction. The Ru atom is coor dinated by a PMe(3) molecule and the two CO groups and by the nido-9,1 0,11-[C(H)=C(H)Bu(t)]3-7,8-C2B9H8 cage. All boron atoms in the pentago nal CBBB ring ligating the metal carry C(H)=C(H)Bu(t) substituents. In addition to X-ray crystal structure determinations, NMR data for the new complexes are reported and discussed ill relation to their structu res.