ALIPHATIC NEODYMIUM ALKOXIDES WITH STERICALLY DEMANDING LIGANDS - PREPARATION AND X-RAY CRYSTAL-STRUCTURES OF ND2(OCH-I-PR2)6L2 (L = THF, PY) AND [ND2(OCH-I-PR2)6(MU-DME)]INFINITY

Reaction of the neodymium tris(silylamide) Nd[N(SiMe3)2]3 with 3 equiv of diisopropylmethanol (HOCH-i-Pr2) in hexane in the presence of THF yields the dimeric Lewis base adduct Nd2(OCH-i-Pr2)6(THF)2 (1). The THF ligands are easily replaced with pyridine in hexane solvent at room temperature to yield the pyridine adduct Nd2(OCH-i-Pr2)6(py)2 (2). The Nd-O bridges in the dimeric alkoxide unit are found to be quite robust, and reaction of 1 with neat 1,2-dimethoxyethane (DME) at room temperature produces Nd2(OCH-i-Pr2)6(mu-DME) (3), in which the two oxygen atoms of each DME molecule link adjacent Nd2(OCH-i-Pr2)6 units to form an infinite-chain structure. In the solid-state structures of 1-3, each Nd atom adopts a distorted trigonal bipyramidal geometry, in which the Nd2O6L2 core can be viewed as two NdO4L trigonal bipyramids joined along a common axial-equatorial edge with the neutral donor ligand L (THF, py, or 1/2 DME) occupying an axial position. The terminal Nd-O distances of OR ligands average 2.153(4), 2.146(4), and 2.145(6) angstrom, while bridging Nd-O distances average 2.381(4), 2.383(9), and 2.375(9) angstrom for 1-3, respectively. The Nd-O-C angles of the terminal alkoxides are very obtuse and average 164.9(4), 174.9(4), and 171.8(8)-degrees, respectively. The Nd-O distances to the oxygen atom of the neutral THF and DME ligands are 2.552(5) and 2.604(6) angstrom, while the Nd-N distance for coordinated pyridine is 2.682(5) angstrom. Crystal data for 1 at -161-degrees-C: monoclinic space group P2(1)/n, a = 10.949(1) angstrom, b = 21.433(3) angstrom, c = 11.965(1) angstrom, beta = 95.63(1)-degrees, V = 2794.44 angstrom3, d(calc) = 1.336 g cm-3, Z = 2. Crystal data for 2 at -162-degrees-C: triclinic space group P1BAR, a = 12.003(4) angstrom, b = 12.243(4) angstrom, c = 11.454(4) angstrom, alpha = 109.99(1)-degrees, beta = 108.82(1)-degrees, gamma = 98.76(1)-degrees, V = 1430.47 angstrom3, d(calc) = 1.321 g cm-3, Z = 1. Crystal data for 3 at -40-degrees-C: triclinic space group P1BAR, a = 10.797(3) angstrom, b = 10.984(3) angstrom, c = 12.112(3) angstrom, alpha = 109.08(3)-degrees, beta = 100.32(2)-degrees, gamma = 90.80(2)-degrees, V = 1331.5 angstrom3, d(calc) = 1.334 g cm-3, Z = 1.