Small Metallacarborane closo-C₂B₄H₆Ru(PPh₃)₂HCl Formed from nido-5,6-C₂B₈H₁₂ by Ruthenium-Mediated Polyhedral Contraction

Abstract

RuCl2(PPh3)3 (1), when heated with an equimolar amount of nido-5,6-C2B8H12 (2) in toluene for a few hours, effected rather unexpected polyhedral contraction of 2 to give the new half-sandwich small ruthenacarborane closo-C2B4H6Ru(PPh3)2HCl (3) in moderate yield along with minor amounts of the two isomeric 11-vertex ruthenacarboranes [3-Cl-1-(η6-C6H5Me)-1,2,4-RuC2B8H9] (4) and [6-Cl-1-(η6-C6H5Me)-1,2,4-RuC2B8H9] (5) with open MC2B8 cluster structure. These new complexes were characterized by 1H, 13C, and 11B NMR spectroscopy and, in the case of 3 and 5, also by an X-ray crystal structure analysis.

Chiral paramagnetic closo-ruthenacarboranes via phosphine–diphosphine displacement reaction of “three-bridge” exo-nido-ruthenacarboranes: Molecular Structure of (−)-[closo-3-Cl-3,3-{(Ph2PCHCH3)2CH2}-3,1,2-RuC2B9H11] and its ortho-cycloboronated derivative

“…. .H B coupling constants of 10.3 and 9.6 Hz, respectively, were observed in the spectra of the related hydrido-ruthenacarborane species closo-3,3-(PPh 3 ) 2 -3-H-3-Cl-3,1,2-RuC 2 B 9 H 11 [17] and closo-3,3-(PPh 3 ) 2 -3-H-3-Cl-3,1,2-RuC 2 B 4 H 6 [18]. Degussa AG for financial support.…”

Facile method for the synthesis of ruthenacarboranes, diamagnetic 3,3-[Ph2P(CH2)nPPh2]-3-H-3-Cl-closo-3,1,2-RuC2B9H11 (n = 3 or 4) and paramagnetic 3,3-[Ph2P(CH2)nPPh2]-3-Cl-closo-3,1,2-RuC2B9H11 (n = 2 or 3), as efficient initiators of controlled radical polymerization of vinyl monomers

“…Paramagnetic complex 9 can also be synthesized start ing from the ionic complex [RuCl(dppe) 2 ] + [7,8 nido C 2 B 9 H 12 ] - (11), which has been prepared earlier 4 as the only product by replacing the PPh 3 ligands in exo nido ru thenacarborane 1 by dppe. In a dilute CH 2 Cl 2 solution, one of the dppe ligands in complex 11 undergoes slow dissociation with the concomitant formation of closo com plex 9.…”

Organometallic chemistry on rhodaheteroborane clusters: reactions with bidentate phosphines and organotransition metal reagents

“…An examination of the structures of 16 and 17, given in Scheme 8, indicates that there should be seven resonances in the 31 P NMR spectrum. 16 should have four resonances in 1 : 1 : 1 : 1 ratio and 17 should have three resonances in 2 : 1 : 1 ratio.…”

“…NMR spectra for 7 at different temperatures suggest an intramolecular dynamic process, which resembles the fluxional behavior observed for the previously studied species, 1 and 10, the isoelectronic platinacarborane, [8,8- 20 It is thought that all these species undergo fluxional motion similar to that illustrated in Scheme 4 for compound 1, involving a closo-type transition state. The activation energy G ‡ calculated for the process observed for 7 at the coalescence temperature of 310 K in the 31 21,22 Further support for the closo-type transition state comes from the observation of the reversible nido to closo change that compound 1 undergoes on deprotonation, which is illustrated in Scheme 3. 9,12,13 When the reactions of compound 1 with dppe and dppp are carried out in 1 : 3 metallathiaborane to phosphine molar ratios, compounds 7 and 10 are formed together with the yellow nido-rhodathiaboranes, [8,8- by substitution reactions at the metal center, and the addition of a second ligand at the 9-position in the cluster.…”