Synthesis,molecular structures and PMR spectra of heteronuclear niobocene derivatives containing a niobium-tin bond |
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Authors: | YuV Skripkin OG Volkov AA Pasynskii AS Antsyshkina LM Dikareva VN Ostrikova MA Porai-Koshits SL Davydova SG Sakharov |
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Institution: | N.S. Kurnakov Institute of General and Inorganic Chemistry, Academy of Sciences of the USSR, Moscow V-71, Leninskii Prosp. 31 U.S.S.R. |
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Abstract: | Treatment of niobocene carbonylhydride, Cp2Nb(CO)H (I), with PhnSnCl4?n and Et2SnCl2 in THF in the presence of Et3N leads to the respective heteronuclear complexes Cp2Nb(CO)SnRnCl3?n (R = Ph, n = 3 ÷ 1 (II–IV), R = Et, n = 2 (V)). Treatment of II with HCl in ether gives Cp2Nb(CO)SnCl3 (VI). Complex VI and its analog (MeC5H4)2Nb(CO)SnCl3 (VIII) were prepared by an alternative synthesis using direct reaction of I or (MeC5H4)2Nb(CO)H with an equimolar quantity of SnCl4 in THF in the presence of Et3N. Complex VI is also generated by insertion of SnCl2 into the NbCl bond in Cp2Nb(CO)Cl (VII). X-Ray analysis of complexes II and VIII was performed: for II, space group P21/n, a = 10.1021(21), b = 17.4633(32), c= 14.2473(29) Å, β = 95.578(16)°, Z = 4; for VIII, space group. P21/n, a= 8.9369(15), b = 13.3589(12), c = 13.9292(20) Å, β = 99.490(14)°, Z = 4. The NbSn bond in VIII (2.764(9) Å) is shorter than that in II (2.825(2) Å). In both cases the NbSn bond is significantly shorter than the sum of Nb and Sn covalent radii (1.66 + 1.40 = 3.06 Å). It is probably partly multiple in character owing to an additional interaction of the lone electron pair of the NbIII ion (d2 configuration) with the antibonding Sn orbitals. The PMR spectra of II–VI exhibit two satellites of the singlet of C5H5 protons because of HSn117 and HSn119 spin-spin coupling (SSC). The SSC constant correlates with the number of electronegative chlorine atoms on the Sn atom. |
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