The charge-compensated monocarbon carboranes nido-7-NR3-7-CB10H12 react with [Ru3(CO)12] in toluene at reflux temperatures to give the triruthenium complexes [Ru3(CO)8(η5-7-NR3-7-CB10H10)] [NR3 = NMe3 (1a), NH2But (1b), and NMe2But (1c)]. The molecular structure of 1a has been established by X-ray crystallography. The metal atoms form an essentially isosceles triangle. One Ru atom carries two terminal CO groups and the nido-7-NMe3-7-CB10H10 cage, coordinated in a pentahapto manner. The two boron atoms in the β-sites with respect to the carbon in the CBBBB ring form exopolyhedral three-center, two-electron B−H⇀Ru bonds to the other two Ru atoms. These metal atoms also carry three essentially terminally attached CO ligands. Treatment of 1a with PPh3 in toluene gave, after column chromatography of the mixture, [Ru3(μ-H)(μ3-σ: η5-7-NMe3-7-CB10H9)(CO)7(PPh3)] (2), whereas reaction with CNBut affords [Ru3(CO)7(CNBut)(η5-7-NMe3-7-CB10H10)] (3). The structure of 2 has been established by X-ray crystallography. The molecule has a triangular array of ruthenium atoms. As in 1a, one metal center Ru(1) carries two CO groups and forms a closo-icosahedral RuCB10 framework by coordination in a pentahapto manner to the open face of a nido-CB10 fragment. A second Ru atom is ligated by two CO molecules and the PPh3 group, the latter being transoid to Ru(1), while the third Ru atom is terminally attached to three CO molecules. The Ru(2)−Ru(3) connectivity is bridged by a hydrido ligand, and in addition both of these metal atoms are linked to the CB10 framework through boron atoms in the β-sites of the CBBBB ring coordinated to Ru(1). Atom Ru(2) forms a three-center, two-electron B−H⇀Ru bond, while atom Ru(3) forms an Ru−B σ-bond, with the result that the nido-7-NMe3-7-CB10H9 group bridges the Ru3 triangle via η5-CBBBB, B−H⇀Ru, and B−Ru interactions. The NMR data for the new compounds are reported and discussed in relation to their structures.

The compounds [RhX(PPh 3 ) 3 ] react with nido-7-NH 2 Bu t -7-CB 10 H 12 in toluene to give the 16-electron complexes [RhX(PPh 3 )(η 5 -7-NH 2 Bu t -7-CB 10 H 10 )] (1a, X ) Br; 1b, X ) Cl). The structure of the zwitterionic molecule 1a was determined by X-ray crystallography. Crystals are monoclinic, space group P2 1 /c, with a ) 12.937(3) Å, b ) 18.101(4) Å, c ) 14.695(4) Å, β )104.21(2)°, and Z ) 4. The metal atom is coordinated on one side by Br and PPh 3 groups and on the other in the pentahapto manner by the open CBBBB face of the cage system. Reactions of the complexes with several donor molecules have been investigated. With CNBu t , by changing the stoichiometry or work-up procedures either the 18-electron complexes [RhX(CNBu t )(PPh 3 )(η 5 -7-NH 2 Bu t -7-CB 10 H 10 )] (2a, X ) Br; 2b, X ) Cl) or [Rh(CNBu t ) 2 (PPh 3 )(η 5 -7-NHBu t -7-CB 10 H 10 )] (3) are obtained, or the 16-electron complex [Rh(CNBu t )(PPh 3 )(η 5 -7-NHBu t -7-CB 10 H 10 )] ( 4) is formed. Formation of 3 and 4, in which the rhodium atoms are ligated by a nido-7-NHBu t -7-CB 10 H 10 cage, formally a 3 π-electron donor, is unusual and results from loss of HX from the precursors 1. To establish firmly the nature of these species, their molecular structures were determined by X-ray crystallography. Crystals of 3 are monoclinic, space group P2 1 /c, with a ) 10.533( 2) Å, b ) 19.110(4) Å, c ) 19.707(4) Å, β )105.413(9)°, and Z ) 4, while those of 4 are triclinic, space group P1 h, with a ) 9.840(3) Å, b ) 10.809(3) Å, c ) 17.287(3) Å, R ) 88.49(2)°, β ) 84.57(2)°, γ ) 69.809( 14)°, and Z ) 2. The two molecular structures are very similar: the rhodium atom is attached on one side via an η 5 -bonding mode to the open face of the 7-NHBu t -7-CB 10 H 10 cage and on the other by the PPh 3 ligand and one or two CNBu t molecules, respectively. The reactions between the compounds 1 and PEt 3 , PMe 3 , NC 5 H 4 Me-4, and tetrahydrofuran (thf) give the complexes [RhBr(PEt 3 )(η 5 -7-NH 2 Bu t -7-CB 10 H 10 )] ( 5), [RhCl(PMe 3 ) 2 (η 5 -7-NH 2 -Bu t -7-CB 10 H 10 )] ( 6), and [RhBr(L)(η 5 -7-NH 2 Bu t -7-CB 10 H 10 )] (7a, L ) NC 5 H 4 Me-4; 7b, L ) thf), respectively. Prolonged refluxing of mixtures of [CoCl(PPh 3 ) 3 ] and nido-7-NH 2 Bu t -7-CB 10 H 12 in toluene gives the arene-(carborane)-cobalt complex [Co(η 6 -C 6 H 5 Me)(η 5 -7-NHBu t -7-CB 10 H 10 )] (8), the structure of which was determined by X-ray diffraction. Crystals are monoclinic, space group P2 1 /c, with a ) 16.332(5) Å, b ) 10.397(2) Å, c ) 22.186(6) Å, β )102.94(2)°, and Z ) 8. NMR data for the new compounds are reported and discussed in relation to their structures. † The compounds described in this paper have a rhodium atom incorporated into a closo-1-carba-2-rhodadodecaborane structure. However, to avoid a complicated nomenclature for the complexes reported, and to relate them to the many known rhodium species with η 5 -coordinated cyclopentadienyl ligands, we treat the cages as nido-11-vertex ligands with numbering as for an icosahedron from which the twelfth vertex has ...

The crystal structure of nido-7-NH 2 Bu t -7-CB 10 H 12 1 has been determined by X-ray diffraction. The compound crystallises in the orthorhombic space group Pbca [a = 10.507( 5), b = 13.805(6), c = 18.093(9) Å]. The nidoicosahedral structure was established with two endo-B᎐H᎐B and two NH 2 hydrogen atoms located in Fourierdifference maps and refined. The structure determination is also supported by 11 B-{ 1 H}-11 B-{ 1 H} correlation NMR spectroscopy. A molecular orbital calculation and frontier density analysis of 1 indicated that deprotonation should initially occur at the exo-nitrogen atom. Treatment of 1 with 1 equivalent of LiBu n , followed by addition of [NEt 3 (CH 2 Ph)]Cl, gave [NEt 3 (CH 2 Ph)][nido-7-NHBu t -7-CB 10 H 12 ] 2 as the only product and single crystals were grown for an X-ray diffraction study. The salt crystallises in the monoclinic space group P2 1 /n [a = 10.651(2), b = 11.652(2), c = 20.926(3) Å, β = 101.77(2)Њ]. The 1 H, 13 C-{ 1 H} and 11 B-{ 1 H} NMR spectra of 1 and 2 have also been recorded.We have recently shown that the zwitterionic monocarbaborane nido-7-NH 2 Bu t -7-CB 10 H 12 1, first reported by Todd and coworkers, 1 is a useful precursor for the synthesis of ruthena-, osma-and rhoda-carbaboranes in direct reactions with lowvalent compounds of these metals. 2 During studies with [RhX-(PPh 3 ) 3 ] (X = Cl or Br) as a precursor it was observed that some of the initially formed species containing the Rh(η 5 -7-NH 2 Bu t -7-CB 10 H 10 ) fragment subsequently deprotonated to give complexes with Rh(η 5 -7-NHBu t -7-CB 10 H 10 ) groups. In other reactions complexes with the Rh(η 5 -7-NHBu t -7-CB 10 H 10 ) moiety were formed directly from the nido-carbaborane. Whereas the charge-compensated η 5 -7-NH 2 Bu t -7-CB 10 H 10 ligand is formally a four-electron donor, the η 5 -7-NHBu t -CB 10 H 10 unit is formally a three-electron donor. These transformations prompted studies of the reagent 1 itself.

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The rhodium sandwich complexes [Rh(η6-arene)(η5-7-NHBut-7-CB10H10)] (arene = C6H5Me (2b), C6H3Me3-1,3,5 (3), MeC6H4C6H4Me-4,4‘ (4), [22](1,4)-C16H16 (5)) have been prepared from reactions between 1:1 mol mixtures of the arenes and [RhCl(PPh3)(η5-7-NH2But-7-CB10H10)] (1a) in CH2Cl2 in the presence of AgBF4. The crystal structures of 3 and 5 have been determined by X-ray diffraction confirming that in these species the rhodium is pentahapto coordinated on one side by the formally three-electron-donor 7-NHBut-7-CB10H10 and on the other in the hexahapto manner by a mesitylene molecule and one C6H4 ring of the cyclophane, respectively. The reaction between 4 and [Mo(CO)3(NCMe)3] in THF gave the dirhodium complex [Rh2(CO)2(η5-7-NH2But-7-CB10H10)2] (6), the structure of which has been established by X-ray diffraction. In the molecule two Rh(CO)(η5-7-NH2But-7-CB10H10) fragments are held together by a Rh−Rh bond which is spanned by two B−H⇀Rh two-electron three-center bonds employing in each CBBBB ring ligating a rhodium center a boron atom in one of the β-sites with respect to the carbon vertex. Reactions between 1a and tris(pyrazolyl)methane in the presence of TlPF6 and between 1a and K[HB(pzMe2-3,5)3] (HB(pzMe2-3,5)3 = hydrotris(3,5-dimethylpyrazolyl)borate) afforded respectively [Rh{HC(pz)3}(η5-7-NH2But-7-CB10H10)][PF2O2] (7) and [Rh{HB(pzMe2-3,5)3}(η5-7-NH2But-7-CB10H10)] (8). An X-ray diffraction study on 7 confirmed the pentahapto bonding of the charge-compensated 7-NH2But-7-CB10H10 ligand and the tridentate character of the tris(pyrazolyl)methane group and also established the anion as [PF2O2]- formed by hydrolysis of [PF6]-. The NMR data for the new compounds are reported and discussed.