Manipulation of organonactinide coordinative unsaturation. Synthesis, structures, and reactivity of thorium hydrocarbyls and hydrides with chelating bis(tetramethylcyclopentadienyl) ancillary ligands (original) (raw)

This contribution describes thorium hydrocarbyl and hydride chemistry based upon the chelating (CHJ2Si[(CHJ4C5]2-ligand (Me,siC~",~-). Precursor Me2Si(Cp"H), can be prepared by reaction of SiCl, with 2 equiv of Li(CHJ4C5, followed by methylation (CH3Li) and methanolic workup. Subsequent reaction with n-C4H&i in 1,2-dimethoxyethane yields Me2Si(Cp"Li),-2DME. The dilithium salt undergoes reaction with ThC14 to yield Me2SiCp",ThC12.2LiC1-2DME, which, in turn, can be alkylated with lithium reagents to produce crystalline, thermally stable Me,SiCp",Thb complexes where R = CH2Si(CHJ3, CH,C(CH,),, CsH5, n-C4HB, and CH1C6H5. The Me2SiCp"2Th[CHzSi(CH3)3]2 complex crystallizes in the monoclinic space group P21/m-C2h with two molecules in a unit cell of dimensions (20 f 1 OC) a = 11.960 (5) A, b = 11.270 (5) A, c = 12.395 (6) A, and 0 = 99.32 (4)'. Least-squares refinement led to a value for the conventional R index (on F) of 0.076 for 2586 independent reflections having I > 3a(I). The molecular structure consists of monomeric Me2SiCp",Th[CH2Si(CHJ3], units with a5-Cp" coordination and L (ring centroid)-Th-(ring centroid) = 118.4". There is considerable dispersion in the Th-C(ring) distances. The Th[CH,Si(CH,),], ligation is highly distorted, with Th-C-Si angles of 123.7 (14)" and 149.5 (12)O, accompanied by corresponding Th-C distances of 2.54 (2) and 2.48 (2) A, respectively. The thorium coordination sphere is more "open" than that in Cp',Th[CH2Si(CH3),J2. Hydrogenolysis of the dialkyl yields the dimeric hydride Me2SiCp",Th(pH),ThCp",SiMez, which crystallizes in the monoclinic space group P2,/n with four molecules in a unit cell of dimensions (20 f 1 "C) a = 10.965 (2) A, b = 19.843 (5) A, c (1) (a) Northwestern University. (b) Crystalytics Co. and the University of Nebraska. (2) (a) Marks, T. J.; Streitwieser, A., Jr. In The Chemistry of the Actinide Elements, 2nd ed.; Katz, J. J.; Seaborg, G. T.; Moras, L. R., Eds.; Chapman and Hall: London, 1986; Chapter 22. (b) Marks, T. J. Ibid., Chapter 23. (c) Marks, T. J.; Fragall, I., Eds. Fundamental and Technological Aspects of Organo-f-Element Chemistry; D. Reidel Dordrecht, Holland, 1985. (d) Marks, T. J.; Ernst, R. D. In Comprehensive Organometallic Chemistry; Wilkinson, G. W.; Stone, F. G. A.; Abel, E. W., Eds.; Pergammon: Oxford, 1982; Chapter 21. (3) (a) Tatsumi, K.; Nakamura, A. J. Am. Chem. SOC. 1987, 109, 3195-3206. (b) Tataumi, K.; Nakamura, A.; Hofmann, P.; Hoffmann, R.; Moloy, K. G.; Marks, T. J. J. Am. Chem. SOC. 1986,108,4467-4476. (c) Bursten, B. E.; Fang, A. Inorg. Chim. Acta 1985,110, 153-160 and references therein. (4) (a) Fendrick, C. M.; Mintz, E. A.; Schertz, L. D.; Marks, T. J.; Day, V. W. Organometallics 1984, 3, 819-821 (preliminary communication). (b) Presented in part at the 11th International Conference on Organometallic Chemistry, Pine Mountain, GA, Oct 1983, Abstract 84. 0276-7333188 12307-1828$01.50/0 A , X = Si(CH3)2