The intermolecular interactions between X-H groups (X ) C, N, and O) and metal atoms in crystalline organometallic complexes have been investigated. Molecular and crystal structures determined by neutron and/or X-ray diffraction data have been retrieved from the Cambridge Structural Database. The comparative analysis of intermolecular H---M and X---M distances as well as that of the X-H---M angles allows a discrimination between the behavior of electrophilic and nucleophilic metal centers. Two novel types of interactions have been characterized: (i) the intermolecular multicenter hetero-acceptor (IMH) hydrogen bond formed when the X-H donor group interacts with M-X′ n systems where M is an electron-rich metal and X′ a metal-coordinated electronegative atom (X′ ) S, N, O, Cl); (ii) the intermolecular pseudo-agostic (IPA) interaction in which the X-H bond can donate electron density to electron deficient metal atoms M---(H-X) as observed in intramolecular agostic interactions. Hydrogen bonding to metal centers in neutral complexes (X-H---M) have been compared with charge assisted (X-H + ---M -) hydrogen bonds involving electronrich anionic complexes.

The intermolecular interactions between X−H donors (X = C, N, O) and electron-rich π-ligands (alkynes, arenes, and cyclopentadienyl ligands) in crystalline organometallic complexes have been investigated from data retrieved from the Cambridge Structural Database. Intermolecular X−H---π interactions are weak hydrogen bonds following the common order of acidity HOH > HNH > HCH but become more effective packing determinants when “charge-assisted” by the presence of an ionic charge (X−Hδ+---πδ-).

A series of protected and terminal dialkynes with extended pi-conjugation through a condensed aromatic linker unit in the backbone, 1,4-bis(trimethylsilylethynyl)naphthalene, 1,4-bis(ethynyl)naphthalene, 9,10-bis(trimethylsilylethynyl)anthracene, 9,10-bis(ethynyl)anthracene, have been synthesized and characterized spectroscopically. The solid-state structures of and have been confirmed by single crystal X-ray diffraction studies. Reaction of two equivalents of the complex trans-[Ph(Et(3)P)(2)PtCl] with an equivalent of the terminal dialkynes 1,4-bis(ethynyl)benzene and, in (i)Pr(2)NH-CH(2)Cl(2), in the presence of CuI, at room temperature, afforded the platinum(II) di-ynes trans-[Ph(Et(3)P)(2)Pt-C[triple bond, length as m-dash]C-R-C[triple bond, length as m-dash]C-Pt(PEt(3))(2)Ph](R = benzene-1,4-diyl; naphthalene-1,4-diyl and anthracene-9,10-diyl ) while reactions between equimolar quantities of trans-[((n)Bu(3)P)(2)PtCl(2)] and under similar conditions readily afforded the platinum(II) poly-ynes trans-[-((n)Bu(3)P)(2)Pt-C[triple bond]C-R-C[triple bond]C-](n)(R = naphthalene-1,4-diyl and anthracene-9,10-diyl ). The Pt(II) diynes and poly-ynes have been characterized by analytical and spectroscopic methods, and the single crystal X-ray structures of and have been determined. These structures confirm the trans-square planar geometry at the platinum centres and the linear nature of the molecules. The di-ynes and poly-ynes are soluble in organic solvents and readily cast into thin films. Optical spectroscopic measurements reveal that the electron-rich naphthalene and anthracene spacers create strong donor-acceptor interactions between the Pt(II) centres and conjugated ligands along the rigid backbone of the organometallic polymers. Thermogravimetry shows that the di-ynes possess a somewhat higher thermal stability than the corresponding poly-ynes. Both the Pt(II) di-ynes and the poly-ynes exhibit increasing thermal stability along the series of spacers from phenylene through naphthalene to anthracene.

Newly synthesized sexithiophenes, di-and tetramethylated at the β-positions, are shown to be soluble and processable compounds, giving single crystals suitable for X-ray structure determination. The molecular packing was characterized in terms of crystal cohesion and short CsH‚‚‚ S and CsH‚‚‚π intermolecular distances. In particular, the dimethylated sexithiophene displayed very compressed molecular packing and a thin film field effect transistor, fabricated with this material, was characterized by high charge mobility [2 × 10 -2 cm 2 /(V s)]. The tetramethylated compound crystallizes at room temperature in two different systems and with different conformations. The conformational polymorphs, which are easily interconverted at room temperature, are characterized by different wavelengths of light emission and excitation decay rates.