Homoleptic optically active ditungsten and dimolybdenum alkoxides. The crystal structure of (+)[W2(OC10H19)6]

Abstract

Reaction of optically resolved methol (1R,2S,5R or 1S,2R,5S) with [M₂(NMe₂)₆] or [M₂(OBu^t)₆](M = Mo or W) in hexane produces (+)- or (–)-[M₂(OC₁₀H₁₉)₆] respectively in high yield (86–98%). The [M₂(OC₁₀H₁₉)₆] compounds are air sensitive, extremely soluble in hydrocarbon solutions and have decomposition points of 174–177 °C. Characterization was achieved by ¹H, ¹³C, ¹³C-{¹H} NMR, IR, CD, ORD, UV and mass spectrometry. For (+)[W₂(OC₁₀H₁₉)₆] X-ray crystallography revealed two independent molecules in the unit cell, both d³–d³ ethane-like dimers: space group P1, a= 15.439(3), b= 15.883(3), c= 13.684(3)Å, α= 104.4(1), β= 99.10(1), γ= 94.27(1)°, Z= 2; WW 2.338 (average), W–O 1.88 Å(average). Reaction of [W₂(NMe₂)₆] with neomenthol produces [W₂(NMe₂)(OC₁₀H₁₉)₅] in high yield. Reaction of [W₂(OC₁₀H₁₉)₆] with MeCN produces [{WN(OC₁₀H₁₉)₃}_x] and [W(CMe)(OC₁₀H₁₉)₃] and with hex-3-yne produces [W(CEt)(OC₁₀H₁₉)₃] and polyhexyne. Reaction of (+)[W₂(OC₁₀H₁₉)₆] with 6 equivalents of L-HOC₁₀H₁₉ produces racemic [W₂(OC₁₀H₁₉)₆] in less than 5 min. Treatment of [{MoN(OBu^t)₃}_x] with menthol produces the optically active polymer [{MoN(OC₁₀H₁₉)₃}_x].