DOI: 10.1002/asia.201300885 Stabilization of the Triphosphallyl Ligand h 3 -P 3 {P(O)H} at Iridium via Alkaline Activation of P 4 Vincenzo Mirabello, Maria Caporali,* Luca Gonsalvi, Gabriele Manca, Andrea Ienco, and Maurizio Peruzzini* [a] Introduction Organophosphorus compounds have a key role in many fields of primary importance, for instance, as agrochemicals and pharmaceuticals. [1] Their efficient preparation starting directly from elemental phosphorus and organic reagents is still challenging and has attracted the attention of many sci- entists for several decades. A series of important results have been recently obtained in this area which allowed the formation of P À X bonds (X = H, C) through stoichiometric processes. Bertrand and co-workers have developed an orig- inal methodology for the functionalization of white phos- phorus by its plane reaction with carbenes such as cyclic alkyl amino carbenes (CAAC), resulting in the formation of new P ÀC bonds. [2] Metal-mediated activation of white phos- phorus has been described in the literature to achieve selec- tive functionalization of this highly reactive allotrope of the element that would not be otherwise feasible. [3] The study of stoichiometric reactions of P 4 with transition metals can be of importance to find suitable sets of experimental condi- tions and stereoelectronic properties needed to catalytically transform P 4 into derivatives containing new P À C, P À H or P ÀOR (R = H, alkyl, aryl) bonds with high efficiency and se- lectivity. Chirik [4] and Cummins [5] have reported beautiful examples of activation and functionalization of P 4 assisted by early transition metals such as Zr and Nb. Main group el- ements have shown as well an interesting chemistry with P 4 , as reviewed by Scheer and coworkers. [6] Recently, we have shown that [IrACHTUNGTRENNUNG(dppm) 2 ]OTf (dppm = Ph 2 PCH 2 PPh 2 ; OTf = OSO 2 CF 3 ) reacts with white phosphorus at room tempera- ture to give [IrACHTUNGTRENNUNG(dppm)(Ph 2 PCH 2 PPh 2 PPPP)]OTf (1) in fair yield. [7] Complex 1 displays a new topology for the P 4 moiety as a consequence of the nucleophilic attack of one PPh 2 end of the bidentate phosphane ligand on P 4 , which re- sults in a new ligand containing a chain of five phosphorus atoms (Scheme 1). In agreement with the previously report- ed [(triphos)Rh(h 1 :h 2 -P 4 RR’)] n + complexes (triphos = MeC- ACHTUNGTRENNUNG(CH 2 PPh 2 ) 3 ;R = H, Me, Ph, R’ = lone pair, H, Me; n = 0,1), [8] the geometry around the metal is trigonal bipyrami- dal considering the pentaphosphorus unit as a bidendate ligand where the P7 atom donates one s electron pair to the metal. Otherwise, P5 and P6 donate one p electron pair to the metal and receive a back-donation from one of the t 2g metal orbitals into the p* level, thus behaving as a dihapto- coordinated P =P bond, as shown by the resonance structures Abstract: The selective functionaliza- tion of the polyphosphorus moiety Ph 2 PCH 2 PPh 2 PPPP present as a tetra- hapto-ligand in complex [IrACHTUNGTRENNUNG(dppm)- (Ph 2 PCH 2 PPh 2 PPPP)] + (1, dppm = Ph 2 PCH 2 PPh 2 ) was obtained by reac- tion of 1 with water under basic condi- tions at room temperature. The forma- tion of the new triphosphaallyl moiety h 3 -P 3 {P(O)H} was determined in solu- tion by NMR spectroscopy, and con- firmed in the solid state by a single- crystal X-ray structure of the stable product [IrACHTUNGTRENNUNG(k 2 -dppm)ACHTUNGTRENNUNG(k 1 -dppm)ACHTUNGTRENNUNG(h 3 - P 3 {P(O)H})] (2). In solution, 2 has a fluxional behavior attributable to the four P atoms belonging to the tetra- phosphorus moiety in 1 and exhibits a chemical exchange process involving the two PPh 2 moieties of the same bi- dentate ligand, as determined by 1D and 2D NMR spectroscopy experi- ments carried out at variable tempera- ture. The mechanism of the reaction was investigated at the DFT level, which suggested a selective attack of an in-situ generated OH À anion on one of the non-coordinated phosphorus atoms of the P 4 moiety. The reaction then evolves through an acid-assisted tautomerization, which leads to the final compound 2. Bonding analysis pointed out that the new unsubstituted P 3 -unit in the h 3 -P 3 {P(O)H} moiety be- haves as a triphosphallyl ligand. Keywords: 1,2-bis(diphenylphos- phino)methane · fluxional behavior · iridium · phosphorus · P ligands · triphosphallyl ligand [a] V. Mirabello, + M. Caporali, L. Gonsalvi, G. Manca, A. Ienco, M. Peruzzini Consiglio Nazionale delle Ricerche Istituto di Chimica dei Composti Organometallici Via Madonna del Piano10, 50019 Sesto Fiorentino (Italy) E-mail : maria.caporali@iccom.cnr.it mperuzzini@iccom.cnr.it [ + ] Current address: Department of Chemistry University of Bath Claverton Down, Bath, BA2 7AY (UK) Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/asia.201300885. Chem. Asian J. 2013, 00,0–0  2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 1 && These are not the final page numbers! ÞÞ FULL PAPER