Reactivity of [M2(μ‐Cl)2(cod)2] (M=Ir,Rh) and [Ru(Cl)2(cod)(CH3CN)2] with Na[H2B(bt)2]: Formation of Agostic versus Borate Complexes |
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| Authors: | K Bakthavachalam K Yuvaraj Mohammad Zafar Prof?Dr Sundargopal Ghosh |
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| Institution: | Department of Chemistry, Indian Institute of Technology Madras, Chennai, India |
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| Abstract: | Treatment of M2(μ‐Cl)2(cod)2] (M=Ir and Rh) with NaH2B(bt)2] (cod=1,5‐cyclooctadiene and bt=2‐mercaptobenzothiazolyl) at low temperature led to the formation of dimetallaheterocycles (Mcod)2(bt)2], 1 and 2 ( 1 : M=Ir and 2 : M=Rh) and a borate complex Rh(cod){κ2‐S,S′‐H2B(bt)2}], 3 . Compounds 1 and 2 are structurally characterized metal analogues of 1,5‐cyclooctadiene. Metal–metal bond distances of 3.6195(9) Å in 1 and 3.6749(9) Å in 2 are too long to consider as bonding. In an attempt to generate the Ru analogue of 1 and 2 , that is (Rucod)2(bt)2], we have carried out the reaction of Ru(Cl)2(cod)(CH3CN)2] with NaH2B(bt)2]. Interestingly, the reaction yielded agostic complexes Ru(cod)L{κ3‐H,S,S′‐H2B(bt)2}], 4 and 5 ( 4 : L=Cl; 5 : L=C7H4NS2). One of the key differences between 4 and 5 is the presence of different ancillary ligands at the metal center. The natural bond orbital (NBO) analysis of 1 and 2 shows that there is four lone pairs of electrons on each metal center with a significant amount of d character. Furthermore, the electronic structures and the bonding of these complexes have been established on the ground of quantum‐chemical calculations. All of the new compounds were characterized by IR, 1H, 11B, 13C NMR spectroscopy, and X‐ray crystallographic analysis. |
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| Keywords: | agostic complexes borate complexes dimetallaheterocycles iridium rhodium |
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