Synthesis and Reactions of the Triruthenamonocarboncarborane Cluster Complex [NHMe3][Ru3(CO)8(η5-7-CB10H11)]

In thf (tetrahydrofuran) at reflux temperatures the compounds [Ru 3 (CO) 12 ] and [NHMe 3 ][ nido -7-CB 10 H 13 ] give the anionic triruthenium complex [Ru 3 (CO) 8 ( η 5 -7-CB 10 H 11 )] -, characterized as its [PPh 4 ] + salt ( 4a ). Protonation of [NHMe 3 ][Ru 3 (CO) 8 ( η 5 -7-CB 10 H 11 )] ( 4b ) with HBF 4 ·Et 2 O yields the hydrido cluster complex [Ru 3 ( μ -H)(CO) 8 ( η 5 -7-CB 10 H 11 )] ( 5 ), the structure of which has been determined by X-ray diffraction. The molecule has a triangle of ruthenium atoms. One ruthenium atom is ligated by the η 5 -7-CB 10 H 11 cage system and carries two CO groups, while the other two ruthenium atoms each carry three CO molecules with a hydrido ligand bridging the metal−metal bond which joins them. In addition, these two metal atoms are linked to the cage through two exopolyhedral B−H⇀Ru bonds. These are formed using boron atoms lying in β sites with respect to the carbon in the open face of the nido -CB 10 H 11 fragment ligating the Ru(CO) 2 group. Treatment of 4b in thf with [CuCl(PPh 3 ) 3 ] in the presence of TlPF 6, or with Ag[BF 4 ] and PPh 3, affords the bimetallic complexes [Ru 3 ( μ -H)(CO) 7 (PPh 3 ){ η 5 -10-M(PPh 3 )-7-CB 10 H 10 }] (M = Cu ( 6a ), Ag ( 6b )), respectively. The structure of 6a was established by X-ray diffraction. A triangle of ruthenium atoms is formed by Ru(CO) 2, Ru(CO) 3, and Ru(CO) 2 (PPh 3 ) units. This triangle is bridged by a nido -10-Cu(PPh 3 )-7-CB 10 H 10 fragment, the open face of which is η 5 -coordinated to the Ru(CO) 2 group. The two boron atoms lying in the β -sites in the ring coordinated to the Ru(CO) 2 moiety form exopolyhedral B−H ⇀ Ru and B−Cu→Ru linkages, respectively, to the Ru(CO) 2 (PPh 3 ) and Ru(CO) 3 groups, which have their Ru−Ru bond bridged by a hydrido ligand. A novel feature of the structure is a three-center−two-electron B−H⇀Cu bond involving the B(2) site in the nido -10-Cu(PPh 3 )-7-CB 10 H 10 cage system. The reaction between 4b and [AuCl(PPh 3 )] gives [Ru 3 ( μ -H)(CO) 8 { η 5 -10-Au(PPh 3 )-7-CB 10 H 10 }] ( 6c ), the structure of which was also determined by X-ray crystallography. It is similar to that of 6a, except there is no exopolyhedral B−H⇀Au bond supplementing the B(10)−Au→Ru and Au−P bonds.