Chromium, iron, ruthenium and gold complexes of 3,3-(biphenyl-2,2 0 -diyl)-1-diphenylphosphino-1-phenylallene: A versatile ligand Emilie V. Banide a , John P. Grealis a , Helge Mu ¨ ller-Bunz a , Yannick Ortin a , Michael Casey a , Claudio Mendicute-Fierro b , M. Cristina Lagunas b, * , Michael J. McGlinchey a, * a School of Chemistry and Chemical Biology, University College Dublin, Belfield, Dublin 4, Ireland b School of Chemistry and Chemical Engineering, Queen’s University Belfast, Belfast BT9 5AG, U.K. Received 4 November 2007; received in revised form 5 January 2008; accepted 6 January 2008 Available online 7 February 2008 Abstract Successive treatment of 9-(phenylethynyl)fluoren-9-ol (1a), with HBr, butyllithium and chlorodiphenylphosphine furnishes 3,3-(biphe- nyl-2,2 0 -diyl)-1-diphenylphosphino-1-phenylallene (5). Moreover, reaction of 1a directly with chlorodiphenylphosphine yields the corre- sponding allenylphosphine oxide (6). The allenylphosphine (5), and Fe 2 (CO) 9 initially form the phosphine–Fe(CO) 4 complex, 11, which is very thermally sensitive and readily loses a carbonyl ligand. In the resulting phosphine–Fe(CO) 3 system, 12, the additional site at iron is coordinated by the allene double bond adjacent to phosphorus; the Fe(CO) 3 tripod in 12 exhibits restricted rotation on the NMR time- scale even at room temperature. The corresponding chromium complex, (5)-Cr(CO) 5 (9), has also been prepared. The gold complexes (5)- AuCl (13), and [(5)-Au(THT)] + X  , where (THT) is tetrahydrothiophene, and X = PF 6 (14a), or ClO 4 (14b), are analogous to the known triphenylphosphine–gold complexes. In contrast, in the (arene)(allenylphosphine)RuCl 2 system the allene double bond adjacent to phos- phorus displaces a chloride, and the resulting cationic species undergoes nucleophilic attack by water yielding ultimately a five-membered Ru–P–C@C–O ruthenacycle (17). Thus, the allenylphosphine (5), reacts initially as a conventional mono-phosphine but, when the metal centre has a readily displaceable ligand such as a carbonyl or halide, the allene double bond adjacent to the phosphorus can also function as a donor. X-ray crystal structures are reported for 5, 6, 11, 12, 13, 14a, 14b and 17. Ó 2008 Elsevier B.V. All rights reserved. Keywords: Allenyl-phosphines; Iron carbonyls; Ruthenium chloride; Gold 1. Introduction In continuation of our studies on the syntheses and dimerizations of fluorenylidene-derived allenes to form bis-alkylidenecyclobutanes, and ultimately tetracenes [1– 3], we wished to incorporate substituents containing other main group elements, in particular phosphorus, silicon and halogens. Since many tetracenes are known to be elec- troluminescent [4], it was hoped that the introduction of a wider range of functional groups into the precursor allenes would allow greater control of their luminescent and other photophysical or electro-conductive properties. We here report the synthesis and characterization of 3,3-(biphenyl- 2,2 0 -diyl)-1-bromo-1-phenylallene (2a), and its conversion to the novel ligand 3,3-(biphenyl-2,2 0 -diyl)-1-diphenylphos- phino-1-phenylallene (5); the corresponding phosphine oxide (6), has also been prepared. Furthermore, the reac- tions of the allenylphosphine (5) with chromium and iron carbonyls, and also with gold and ruthenium chlorides, are described. 0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.jorganchem.2008.01.046 * Corresponding authors. Tel.: +353 1 716 2880; fax: +353 1 716 1178. E-mail addresses: c.lagunas@qub.ac.uk (M. Cristina Lagunas), michael.mcglinchey@ucd.ie (M.J. McGlinchey). www.elsevier.com/locate/jorganchem Available online at www.sciencedirect.com Journal of Organometallic Chemistry 693 (2008) 1759–1770