SYNTHESIS, STRUCTURE, AND REACTIVITY OF DIMERIC MONO(CYCLOPENTADIENYL)YTTRIUM BIS(TERT-BUTOXIDE) COMPLEXES - [(C5R5)Y(MU-OCME3)(OCME3)]2 (C5R5=C5ME5, C5H5, C5H4ME, C5H4SIME3, AND C9H7)

The reaction of Y3(OR)7Cl2(THF)2 (R = CMe3) with alkali metal cyclopentadienyl reagents, MC5R6 (M = Na or K), in toluene disrupts the trimetallic structure of the starting material and forms the halide-free bimetallic compounds [(C5R5)Y(mu-OR)(OR)]2 (C5R5 = C5Mer5, 1; C5H5, 2; C5H4Me, 3; C5H4SiMe3, 4). 1 and 4 were also obtained from the reaction of YCl3(THF)x with 2 equiv of NaOCMe3 and 1 equiv of MC5R5 in toluene at reflux. Also prepared in this manner was the indenyl analog, [(C9H7)Y(mu-OR)(OR)]2, 5. X-ray crystallographic data on 1,2,4, and 5 reveal that structurally analogous complexes are formed in these reactions despite the different substituents on the cyclopentadienyl rings. In each of these four complexes, the two cyclopentadienyl ligands are arranged in a cis orientation around a (RO)Y(mu-OR)2Y(OR) central core which has similar metrical parameters in each compound. The ligand redistribution product (C5H5)2Y(mu-OR)2Y(C5H5)(OR), 6, is also isolated as a minor component in the reaction between Y3(OR)7Cl2(THF)2 and NaC5H5. 2-5 react with LiCH2SiMe3 to unexpectedly lose LiC5R5 instead of LiOR. Crystallization of the 2/LiCH2SiMe3 reaction product in the presence of dimethoxyethane (DME) yields the cyclopentadienyl-free complex (RO)Y(mu-OR)3Li5(mu3-OR)2(THF)(mu-OCH2CH2OMe)2, 7. 7 can be viewed as a (RO)Y(mu-OR)[mu-OR)2Li(THF)] unit connected to a Li4O4 cube which has oxygen donor atoms provided by bridging tert-butoxide ligands and two bidentate ligands formally derived from DME by loss of a methyl group. In the reaction of 4 with LiCH2SiMe3, the cyclopentadienyl component is recovered in a crystalline form as the polymeric, supersandwich metallocene, [Li(mu,eta5,eta5-C5H4SiMe3)]n, 8. 4 reacts with LiN(SiMe3)2 by a ligand redistribution pathway to form (C5H4SiMe3)2Y(mu-OR)2Li(THF)2, 9. 1 Crystallized from hexanes at -35-degrees-C in space group P2(1)/c with a = 12.657(3) angstrom, b = 17.412(5) angstrom, c = 18.532(5) angstrom, beta = 99.16(2)degrees, V = 4032(2) angstrom3, and D(calcd) = 1.22 Mg/m3 for Z = 4. Least squares refinement of the model based on 3296 reflections (\F(o)\ > 6.0sigma(\F(o)\) converged to a final R(F) = 8.8%. 2 crystallized from toluene or hexanes at -35-degrees-C in space group P42(1)mBAR with a = 9.7738(13) angstrom, c = 16.133(4) angstrom, V = 1541.1(5) angstrom3, and D(calcd) = 1.29 Mg/m3 for Z = 2. Least squares refinement of the model based on 888 reflections (\F(o)\ > 4.0sigma(\F(o)\)) converged to a final R(F) = 7.3%. 4 crystallized from toluene at -35-degrees-C in space group P2(1)/c with a = 20.697(4) angstrom, b = 10.1222(14) angstrom, c = 21.264(4) angstrom, beta = 114.328(13)degrees, V = 4059.2(12) angstrom3, and D(calcd) = 1.219 Mg/m3 for Z = 4. Least squares refinement of the model based on 3724 reflections (\F(o)\ > 3.0sigma(\F(o)\)) converged to a final R(F) = 6.7%. 5 crystallized from hexanes at -35-degrees-C in the space group P2(1)/c with a = 13.231(2) angstrom, b = 15.481(3) angstrom, c = 17.516(5) angstrom, beta = 99.91(2)degrees, V = 3534.0(13) angstrom3, and D(calcd) = 1.317 Mg/m3 for Z = 4. Least squares refinement of the model based on 3229 reflections (\F(o)\ > 3.0sigma(\F(o)\) converged to a final R(F) = 6.8%. 9 crystallized from hexanes at -35-degrees-C in space group P2(1)/c with a = 17.285(12) angstrom, b = 13.022(11) angstrom, c = 17.30(2) angstrom, beta = 104.63(7)degrees, V = 3767(6) angstrom3, and D(calcd) = 1.165 Mg/m3 for Z = 4. Least squares refinement of the model based on 2159 reflections (\F(o)\ > 4.0sigma(\F(o)\)) converged to a final R(F) = 8.1%.