4-ethinyl-benzonitrile-ferrocenes bridged by a Pd(PPh3)(2) unit; the solid-state structure of (eta(5)-C5H5)Fe(eta(5)-C5H4C equivalent to CC6H4C equivalent to N-1,4)

The trinuclear Fc-Pd-Fc complex [(FcC drop CC6H4C dropN-1,4)(2)Pd(PPh3)(2)] (OTf)(2) (5) [Fc = (eta (5)-C5H5)Fe(eta (5)-C5H4)] is accessible by the re action of FcC drop CC6H4C dropN-1,4 (3) with (Ph3P)(2)Pd(OTf)(2) (4) in a 2 :1 molar ratio. In 5 the corresponding late transition metal centers are li nked by C5H4C drop CC6H4C dropN-1,4 pi -conjugated organic units. The resul t of the X-ray structure analysis of 3, which itself can be synthesised by a Sonogashira coupling of FcC drop CH (1) with BrC6H4C dropN-1,4 (2), is re ported. Complex 3 crystallises in the monoclinic space group P2(1) with the following cell parameters: a = 9.6598(6), b = 7.3185(5), c = 10. 1910(7) A ngstrom, beta = 98.876(3)degrees, V= 711.80(8) A(3) and Z = 2. In 3 the cyc lopentadienyl ligands are rotated by 4.1(2)degrees and therefore possess an almost eclipsed conformation. With respect to the eta (5)-coordinated C5H4 group, the C6H4 unit is tilted by 69.87(13)degrees. Electrochemical studie s on 3 show that the Fe(II)/Fe(III) oxidation process appears to be reversi ble and is shifted to a more positive value when compared to the FcH/FcH(+) couple. An even more positive value is observed for 5. A reason for this b ehaviour is presented. (C) 2001 Elsevier Science B.V. All rights reserved.