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

An alternative synthesis of (+/-)-4-ethynyl[2.2]paracyclophane (PCP-C equivalent to CH) (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 racentic terminal alkyne 5 was employed as starting material for assembling of a luminescent extended pi-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 [Co-2(CO)(6)(mu-eta(2)-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)(PCP-C equivalent to CH)] (11) and the heterodinuclear dimetallacyclopentenone [(OC)(2)Fe{mu-C(=O)C(PCP)=C(H)] (mu-dppm)Pt(PPh3)] (12). The synthesis and reactivity of 4-isocyano[2.2]paracyclophane (15) towards heterobimetalliciron-platinum and palladium-platinum complexes is also presented. Opening of the dative iron, platinum bond Of [(OC)(4)Fe(p-dpPM)PtCl2] (16) occurred upon addition of 15 to a CH2Cl2 solution of 16 leading to 1(OC)(4)Fe{mu-dppm)PtCl2(C equivalent to N-PCP)] (17). Treatment of [ClPd(mu-dPPM)(2)PtCl] (18) with isocyanide 15 in a 1:1 ratio affords the A-frame compound [ClPd(mu-dPPM)(2)(mu-C=N-PCP)PtCl] (19), resulting from formal insertion of 15 into the Pd-Pt bond. Addition of 2equiv. of 15-18 leads to the ionic A-frame compound [CIPd(mu-dPPM)(2)(mu-C=N-PCP)Pt(C equivalent to N-PCP)]Cl (20). (c) 2006 Elsevier BN. All rights reserved.