From Metallaborane to Borylene Complexes: Syntheses and Structures of Triply Bridged Ruthenium and Tantalum Borylene Complexes

• Published in: Chemistry : a European journal Vol. 16; no. 37; pp. 11357 - 11366
• Main Authors: Geetharani, K., Bose, Shubhankar Kumar, Varghese, Babu, Ghosh, Sundargopal
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 04-10-2010; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Subjects: Ambient temperature; borylenes; Chemistry; Crystal structure; Infrared spectroscopy; Ligands; manganese; metallaboranes; Precursors; Pyrolysis; Ruthenium; Tantalum
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201001208

Reaction of [1,2‐(Cp*RuH)2B3H7] (1; Cp*=η5‐C5Me5) with [Mo(CO)3(CH3CN)3] yielded arachno‐[(Cp*RuCO)2B2H6] (2), which exhibits a butterfly structure, reminiscent of 7 sep B4H10. Compound 2 was found to be a very good precursor for the generation of bridged borylene species. Mild pyrolysis of 2 with [Fe2(CO)9] yielded a triply bridged heterotrinuclear borylene complex [(μ3‐BH)(Cp*RuCO)2(μ‐CO){Fe(CO)3}] (3) and bis‐borylene complexes [{(μ3‐BH)(Cp*Ru)(μ‐CO)}2Fe2(CO)5] (4) and [{(μ3‐BH)(Cp*Ru)Fe(CO)3}2(μ‐CO)] (5). In a similar fashion, pyrolysis of 2 with [Mn2(CO)10] permits the isolation of μ3‐borylene complex [(μ3‐BH)(Cp*RuCO)2(μ‐H)(μ‐CO){Mn(CO)3}] (6). Both compounds 3 and 6 have a trigonal‐pyramidal geometry with the μ3‐BH ligand occupying the apical vertex, whereas 4 and 5 can be viewed as bicapped tetrahedra, with two μ3‐borylene ligands occupying the capping position. The synthesis of tantalum borylene complex [(μ3‐BH)(Cp*TaCO)2(μ‐CO){Fe(CO)3}] (7) was achieved by the reaction of [(Cp*Ta)2B4H8(μ‐BH4)] at ambient temperature with [Fe2(CO)9]. Compounds 2–7 have been isolated in modest yield as yellow to red crystalline solids. All the new compounds have been characterized in solution by mass spectrometry; IR spectroscopy; and 1H, 11B, and 13C NMR spectroscopy and the structural types were unequivocally established by crystallographic analysis of 2–6.
Arachnophilia: Mild reaction of arachno‐[(Cp*RuCO)2B2H6] with [Fe2(CO)9] and [Mn2(CO)10] yielded triply bridged borylene species 1 and 2 and bis‐borylene complexes 3 and [{(μ3‐BH)(Cp*Ru)Fe(CO)3}2(μ‐CO)]. The first bridged tantalum borylene complex, 4, was synthesized by the reaction of [(Cp*Ta)2B4H8(μ‐BH4)] with [Fe2(CO)9] at ambient temperature (see picture).