DOI: 10.1002/chem.200701209 Coordination Features of a Hybrid Scorpionate/Phosphane Ligand Exemplified with Iridium JosØ A. Camerano, [a] Miguel A. Casado,* [a, b] Miguel A. Ciriano,* [a] Cristina Tejel, [a] and Luis A. Oro [a, b] Introduction The continuous advances and discoveries in organometallic chemistry are often determined by the synthesis of new types of ligand systems that have been designed to influence the metallic environment and to induce changes in their properties and reactivity. A memorable breakthrough in co- ordination chemistry occurred in 1966 when Trofimenko in- troduced the poly(pyrazolyl)borate (Tp) systems, or scorpio- nates, [1] which have generated wide interest in interdiscipli- nary fields for a long time. [2] These anionic systems are char- acterized by their relatively hard nitrogen s-donor atoms and they exhibit a rich coordination chemistry with virtually all of the metallic centers of the Periodic Table. [3] Addition- ally, they are extremely versatile as they can adopt both k 3 - and k 2 -coordination modes around the metals, [4] which allows new patterns of reactivity compared with soft p sys- Abstract: Although the pentacoordi- nated complex [IrACHTUNGTRENNUNG{(allyl)B- ACHTUNGTRENNUNG(CH 2 PPh 2 )(pz) 2 }ACHTUNGTRENNUNG(cod)] (1; pz = pyrazol- yl, cod = 1,5-cyclooctadiene), isolated from the reaction of [{IrACHTUNGTRENNUNG(m-Cl)ACHTUNGTRENNUNG(cod)} 2 ] with [LiACHTUNGTRENNUNG(tmen)][BACHTUNGTRENNUNG(allyl)ACHTUNGTRENNUNG(CH 2 PPh 2 )- (pz) 2 ] (tmen = N,N,N’,N’-tetramethyl- ACHTUNGTRENNUNGethane-1,2-diamine), shows behavior similar to that of the related hydrido- tris(pyrazolyl)borate complex, the car- bonyl derivatives behave in a quite dif- ferent way. On carbonylation of 1, the metal  metal-bonded complex [(Ir- ACHTUNGTRENNUNG{(allyl)BACHTUNGTRENNUNG(CH 2 PPh 2 )(pz) 2 }CO) 2 ACHTUNGTRENNUNG(m-CO)] (2) that results has a single ketonic car- bonyl bridge. This bridging carbonyl is labile such that upon treatment of 2 with PMe 3 the pentacoordinated Ir I complex [Ir(CO){(pz)B(h 2 -CH 2 CH= CH 2 )ACHTUNGTRENNUNG(CH 2 PPh 2 )(pz)}ACHTUNGTRENNUNG(PMe 3 )] (3) was isolated. Complex 3 shows a unique fac coordination of the hybrid ligand with the allyl group h 2 -bonded to the metal in the equatorial plane of a distorted trigonal bipyramid with one pyrazolate group remaining uncoordinated. This unusual feature can be rationalized on the basis of the electron-rich nature of the metal center. The related complex [Ir(CO){(pz)B(h 2 -CH 2 CH=CH 2 )- ACHTUNGTRENNUNG(CH 2 PPh 2 )(pz)}ACHTUNGTRENNUNG(PPh 3 )] (4) was found to exist in solution as a temperature- dependent equilibrium between the cis- pentacoordinated and trans square planar isomers with respect to the phosphorus donor atoms. Protonation of 3 with different acids is selective at the iridium center and gives the cation- ic hydrides [IrACHTUNGTRENNUNG{(allyl)B- ACHTUNGTRENNUNG(CH 2 PPh 2 )(pz) 2 }(CO)HACHTUNGTRENNUNG(PMe 3 )]X (X = BF 4 (5), MeCO 2 (6), and Cl (7)). Com- plex 7 further reacts with HCl to gen- erate the unexpected product [Ir(CO)ClACHTUNGTRENNUNG{(Hpz)BACHTUNGTRENNUNG(CH 2 PPh 2 )(pz)- ACHTUNGTRENNUNGCH 2 CH(Me)}ACHTUNGTRENNUNG(PMe 3 )]Cl (9 ; Hpz = pro- tonated pyrazolyl group) formed by the insertion of the hydride into the Ir ACHTUNGTRENNUNG(h 2 -allyl) bond. In contrast, protona- tion of complex 4 with HCl stops at the hydrido complex [IrACHTUNGTRENNUNG{(allyl)B- ACHTUNGTRENNUNG(CH 2 PPh 2 )(pz) 2 }(CO)HACHTUNGTRENNUNG(PPh 3 )]Cl (8). X-ray diffraction studies carried out on complexes 2, 3, and 9 show the versatil- ity of the hybrid scorpionate ligand in its coordination. Keywords: iridium · N,P ligands · protonation · scorpionate ligands · tripodal ligands [a] Dr. J. A. Camerano, Dr. M. A. Casado, Prof. M. A. Ciriano, Dr. C. Tejel, Prof. L. A. Oro Departamento de Química Inorgµnica Instituto de Ciencias de Materiales de Aragón CSIC-Universidad de Zaragoza, Pedro Cerbuna 12, 50009 Zaragoza (Spain) Fax: (+ 34)976-761-187 E-mail: mcasado@unizar.es mciriano@unizar.es [b] Dr. M. A. Casado, Prof. L. A. Oro Instituto Universitario de Catµlisis HomogØnea Pedro Cerbuna 12, 50009 Zaragoza (Spain) Supporting information for this article is available on the WWW under http://www.chemeurj.org/ or from the author. Chem. Eur. J. 2008, 14, 1897 – 1905 # 2008 Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim 1897 FULL PAPER