Ethynyl[2.2]paracyclophanes and 4-isocyano[2.2]paracyclophane as ligands in organometallic chemistry

An alternative synthesis of (±)-4-ethynyl[2.2]paracyclophane (PCPCCH) (5) and 4,16-diethynyl[2.2]paracyclophane (6) via the Corey–Fuchs reaction has been developed. The olefinic intermediate 4-dibromovinyl[2.2]paracyclophane (3) has been isolated and structurally characterized. The racemic terminal alkyne 5 was employed as starting material for assembling of a luminescent extended π-conjugated system containing a thiophene unit and for a catalytic bis-silylation reaction yielding the olefinic dithioether Z-PhSCH2Me2SiC(H)C(PCP)SiMe2CH2SPh (9). The dimetallatetrahedran [Co2(CO)6(μ-η2–PCP–CCH)] (10) has been prepared and its crystal structure determined by an X-ray diffraction analysis. Alkyne 5 has also been used for the preparation of the Pt(0) complex [Pt(PPh3)2(PCPCCH)] (11) and the heterodinuclear dimetallacyclopentenone [(OC)2Fe{μC(O)C(PCP)C(H)}(μ-dppm)Pt(PPh3)] (12). The synthesis and reactivity of 4-isocyano[2.2]paracyclophane (15) towards heterobimetallic iron–platinum and palladium–platinum complexes is also presented. Opening of the dative iron → platinum bond of [(OC)4Fe(μ-dppm)PtCl2] (16) occurred upon addition of 15 to a CH2Cl2 solution of 16 leading to [(OC)4Fe{μ-dppm}PtCl2(CNPCP)] (17). Treatment of [ClPd(μ-dppm)2PtCl] (18) with isocyanide 15 in a 1:1 ratio affords the A-frame compound [ClPd(μ-dppm)2(μ-CNPCP)PtCl] (19), resulting from formal insertion of 15 into the Pd–Pt bond. Addition of 2 equiv. of 15–18 leads to the ionic A-frame compound [ClPd(μ-dppm)2(μ-CNPCP)Pt(CNPCP)]Cl (20).

4-Ethynyl[2.2]paracyclophane (PCPCCH) was employed as starting material for assembling of an luminescent π-conjugated system containing a thiophene unit and for a bis-silylation reaction. PCPCCH has also been used for the preparation of various mono- and dinuclear organometallic complexes. The synthesis and reactivity of 4-isocyano[2.2]paracyclophane towards heterobimetallic iron–platinum and palladium–platinum complexes is also presented.Figure optionsDownload as PowerPoint slide