Synthesis, properties, and solid-state structures of bis(alkyne)metal(0) complexes (metal=Ni,Pt) with substituted alkynediols and alkynols

A variety of tetrasubstituted alkynediols react with (cdt)Ni (cdt = 1.5.9-cyclododecatriene) to give the homoleptic (alkyne)nickel complexes (HOR(1)R(2)CC=CCR(1)R(2)OH)(2)Ni as yellow crystals that are stable in the solid state at room temperature (R(1) = R(2) = Et, 1; R(1) = Me, R(2) = Et, 2; R(1) = Me, R(2) = Pr, 3; R(1) = R(2) = -(CH2)(5)-, 4; R(1) = Me, R(2) = i-Bu, 5). The C-13-NMR spectra show resonances for the coordinated alkyne carbon nuclei in the 133.5-135.2 ppm region. Only one resonance was found for 1-4 indicating a symmetrical structure. More than one resonance was found for 5 as well as for its platinum analog, compound 8, indicating the presence of different isomeric bis(alkyne)metal complexes. The structure of 1 has been established by single-crystal X-ray diffraction. The central atom is tetrahedrally coordinated to the four carbon atoms of two terminal alkynes. The network of hydrogen bonding between the four OH groups of neighboring molecules, which consists exclusively of intermolecular hydrogen bonds, stabilizes the crystal structure yielding a polymer-like chain. The platinum complex 9 (R(1) = R(2) = Me) shows similar structural properties. The reaction of (cdt)Ni or (cod)(2)Pt (cod = 1.5-cyclooctadiene) with the substituted alkynols R(3)CC=CCR(2)(1)OH yields the new bis(alkyne)metal(0) compounds 10 (M = Ni, R = Me, R(1) = Me), 11 (M = Pt, R = Me, R(1) = Me), and 12 (M = Ni, R = Me, R(1) = Et). Single-crystal X-ray structure determinations of 10-12 reveal that the central metal atoms are tetrahedrally coordinated by the four carbon atoms of the alkyne ligands. Two (alkyne)(2)M units are connected via hydrogen bonds between the four OH groups to form a dimer in the solid state. Complex 10 reacts in solution below -15 degrees C to yield the trimeric complex (alkyne)(4)Ni-3.