Metathetic reactions involving ditungsten hexapivalate. Preparation and structures of W 2(O 2C tBu) 2(O tBu) 2(N iPr 2) 2, W 2(O 2C tBu) 4(N iPr 2) 2, W 2(O 2C tBu) 2(O tBu) 4 and Na 2W 4O 4Cp 2(O 2C tBu) 6 solvate where CpC 5H 5

Abstract

The reactions between W 2(O 2C tBu) 6(M 3−M) and each of Na/Hg, NaBH 4, LiHBEt 3 and LiMe in hydrocarbon/THF solutions yield W 2(O 2C tBu) 4(M 4−M). W 2(O 2C tBu) 6 and KO tBu (2 equiv.) or W 2(O tBu) 6 react to give W 2(O 2C tBu) 2(O tBu) 4 ( 1) by ligand redistribution. Crystal data for 1 at − 172°C: a = 11.200(3), b = 16.331(5), c = 10.490(3) A ̊ , α = 95.71(2), β = 111.19(1), γ = 71.82(1)° , Z = 2, D calc = 1.685 g cm −3, space group P - 1 . A similar reaction involving W 2(O 2C tBu) 6 and LiNPr 2 i (2 equiv.) yields and isomeric mixture of W 2(O 2C tBu) 4(N iPr 2) 2, for which one isomer, 2, has been crystallographically characterized. Crystal data for 2 at −164°C: a = 41.858(9), b = 10.009(2), c = 41.481(9) A ̊ , Z = 16, D calc = 1.608 g cm −3 , space group C2/ c. Compound 2 was shown to react with KO tBu (2 equiv.) to give a 6:1:1 mixture of products from which the major product W 2(O 2C tBu) 2(N iPr 2) 2(O tBu) 2 ( 3) was characterized. Crystal data for 3 at −174°C: a = 10.675(4), b = 9.836(4), c = 35.795(14) A ̊ , β = 96.76(2)°, Z = 4, D calc = 1.631 g cm −3 , space group P2 1/ c. The reaction between W 2(O 2C tBu) 6 and NaCp (2 equiv.) in THF gave an orange hydrocarbon soluble crystalline compound Na 2W 4O 4Cp 2(O 2C tBu) 6·4 tBuCOOH·toluene, ( 4· solvate). Crystal data for 4·solvate at −70°C: a = 13.065(2), b = 14.941(2), c = 12.996(2) A ̊ , β = 114.90(1), γ = 71.69(1)°, Z = 1 , D calc = 1.67(2) g cm −3, space group P - 1 . In compounds 1, 2 and 3 there are Wz.3usco;;W bonds and each metal atom is coordinated to four ligand atoms. The Mz.3usco;M bond is spanned by a pair of cis-ppivalate ligands. The structure of the W 4O 4Cp 2(O 2C t Bu) 6 2− anion is a centrosymmetric bis-oxo bridged dimer [ η 5-C 5H 5)( η 1-O 2C tBu) 2W ( μ- η 1, η 1-O 2C tBu)W (=O)( μ-O)] 2 with a WW bonding distance of 2.537(1) Å.