The crystal structure of bis(tetra-n-butylammonium)bis(mu(2)-hydroxo)-bis(1,2,3,4-tetrakis(methoxycarbonyl)-1,3-butadiene-1,4-diyl)-di-palladium, NBu4[Pd-2{C-4(COOMe)(4)}(2) (mu-OH)(2)], was determined ab initio by X-ray single-crystal diffractometry using the charge flipping method. The compound crystallizes in the monoclinic system with P2(1/c) as space group and the following cell parameters: a = 12.8481(6) angstrom, b = 63.744(3) angstrom, c = 16.6102(8) angstrom, beta = 111.943(10). The asymmetric unit is formed by two molecules, and the unit cell contains eight molecules (Z=8) giving a density of 1.369 g cm(-3). The coordination around the Pd(II) atoms is approximately planar, the methoxycarbonyl groups at the alpha and beta positions relative to Pd are perpendicular and parallel to the palladacycle ring, respectively, and the {Pd(mu-O)}(2) core has a bent conformation. The structure closely resembles the features reported previously for other palladacyclopentadiene complexes. (C) 2007 Elsevier B.V. All rights reserved.