Chemistry of C-Trimethylsilyl-Substituted Heterocarboranes. 32. Synthetic and Structural Investigations on Half-Sandwich Lanthanacarboranes: Important Synthons in Metallacarborane Chemistry

摘要

The reactivities of the monosodium-complexed carborane precursors nido-1-Na(C_4H_8O)-2-(R)-3-(SiMe_3)-2,3-C_2B_4H_5 (R = SiMe_3 (1) or Me (2)) with a number of lanthanide halides were investigated. The reaction of LnCl_3 (or LnBr_3) with 1 in a 1:2 molar ratio in dry THF at 60 deg C produced the dimerized half-sandwich lanthanacarborane complexes [2,3-(SiMe_3)_2- 1-X-1 -(THF)_m-1-Ln(eta~5-2,3-C_2B_4H_4)]_2 centre dot n(THF) (3, Ln = Y, X = Cl, m = 2, n = 1; 4, Ln = La, X = Br; m = 1, n = 0; 5, Ln = Ce, X = Br; m = 1, n = 0; 6, Ln = Pr, X = Br; m = 2, n = 1; 7, Ln = Nd; X = Cl, m = 2, n = 1; 8, Ln = Sm; X = Br, m = 2, n = 0; 9, Ln = Gd; X = Cl, m = 2, n = 1; 10, Ln = Tb, X = Cl, m = 2, n = 1; 11, Ln = Dy, X = Cl, m = 2, n = 1; 12, Ln = Ho, X = Cl, m = 2, n = 1; 13, Ln = Er, X = Cl, m = 2, n = 1; 14, Ln = Tm, X = Cl, m = 2, n = 1; 15, Ln = Yb, X = Cl, m = 2, n = 1; 16, Ln = Lu X = Cl, m = 2, n - 1) as crystalline solids in 70-92% isolated yields. In a similar manner, the reactions of 2 with LnCl_3 at 65 deg C gave the corresponding complexes [2-Me-3-(SiMe_3)-1-Cl-1-(THF)_2-1-Ln(eta~5-2,3-C_2B_4H_4)]_2 (17, Ln = Nd; 18, Ln = Dy; 19, Ln = Ho; 20, Ln = Er; 21, Ln = Yb) as crystalline solids in 72-80% yield. In both series of the reactions, 1 equiv of the particular neutral carborane was also produced. The substitution of the chloride ions in complexes 17 and 20 by 2 gave the half-sandwich lanthanacarborane clusters {2-Me-3-(SiMe_3)-1-[4,5-(mu-H)-nido-2-Me-3-(SiMe_3)-2,3-C_2B_4H_5]-1-Ln(eta~5-2,3-C_2B_4H_4)}_2 centre dot n(THF) (22, Ln = Nd, n = 2; 24, Ln = Er, n = 1) as crystalline solids in 82-87% yield. The reaction of 19 and 2 produced the trimer {2-Me-3-(SiMe_3)-1-[4,5-(mu-H)-nido-2-Me-3-(SiMe_3)-2,3-C_2B_4H_5]-1-Ho(eta~5-2,3-C_2B_4H_4)}_3 centre dot 8(THF) (23) in 57% yield. Complexes 22, 23, and 24 could directly be obtained in good yield (56-67%) from the reaction of 2 with the corresponding LnCl_3 at 65 deg C in molar ratios of 3:1 in dry THF. Similarly, the mixed coordinated complex {2,3-(SiMe_3)_2-1-[4,5-(mu-H)-(nido-2-Me-3-(SiMe_3)-2,3-C_2B_4H_5)]-1-Gd(eta~5-2,3-C_2B_4H_4)}_2 centre dot 3(THF) (25) was obtained by reacting compound 9 with 2. To investigate the importance of the halide in these reactions, (eta~5-Cp)LnCl_2 (Ln = Tb, Dy, Er) with 1 in a 1:2 molar ratio produced lanthanacarborane complexes [1-(eta~5-C_5H_5)-2,3-(SiMe_3)_2-1-Ln(eta~5-2,3-C_2B_4H_4)]_2 centre dot n(THF) (26, Ln = Tb, n = 2; 27, Ln = Dy, n = 2; 28, Ln = Er, n = 3) as crystalline solids in 77-82% isolated yields. On the other hand, the reactions of (eta~5-Cp)_2ErCl and (eta~8-C_8H_8)GdCl with 1 in 1:1 molar ratios did not produce the half-sandwich lanthanacarboranes, but rather gave the exo-polyhedral products {exo-(eta~5-C_5H_5)_2Er[4,5-(mu-H)-2,3-(SiMe_3)_2-2,3-C_2B_4H_4]} centre dot (THF) (29) and {exo-(eta~8-C_8H_8)Gd[4,5-(mu-H)-2,3-(SiMe_3)_2-2,3-C_2B_4H_4] centre dot 2(THF) (30) as crystalline solids in 76% and 73% isolated yield, respectively. All compounds were characterized by IR spectroscopy and elemental analysis, whereas compounds 3, 7-9, 10-16,18-22, 29, and 30 were characterized by single-crystal X-ray diffraction studies. The diamagnetic compounds 3, 4, and 16 were additionally characterized by ~1H, ~(13)C, and ~(11)B NMR spectroscopy.