pubs.acs.org/Organometallics Published on Web 06/10/2010 r 2010 American Chemical Society Organometallics 2010, 29, 3027–3038 3027 DOI: 10.1021/om100315d Allyl Amination of Phosphinoquinoline Allyl Complexes of Palladium. Influence of the Allyl Hapticity on the Reaction Rate and Regiochemistry L. Canovese,* ,† F. Visentin, † C. Santo, † G. Chessa, † and V. Bertolasi ‡ † Dipartimento di Chimica, Universit  a Ca’ Foscari, Venice, Italy, and ‡ Dipartimento di Chimica and Centro di Strutturistica Diffrattometrica Universit  a di Ferrara, Ferrara, Italy Received April 19, 2010 The ligands 8-diphenylphosphanylquinoline (DPPQ) and 8-diphenylphosphanyl-2-methylquinoline (DPPQ-Me) react in chlorinated solvents with the allyl dimers [Pd( μ-Cl)(η 3 -C 3 H 5 )] 2 and [Pd( μ-Cl)(η 3 - C 3 H 3 Me 2 )] 2 , yielding palladium allyl phosphanylquinoline complexes whose structure is strongly influ- enced by the ancillary ligand and the presence or the absence of chloride ion in solution. Thus, the allyl fragments in the DPPQ derivatives assume η 3 -hapticity in the absence of chloride and display monohapto coordination when the chloride is not removed from the reaction mixture. In the DPPQ-Me allyl derivatives the allyl fragment is always η 3 -coordinated, while the ancillary ligand may act as bis- or monochelating in the absence or in the presence of chloride, respectively. The reactivity of the allyl complexes was tested by means of the allyl-amination reaction carried out by either NMR or UV-vis techniques. It was noticed that the η 3 -derivatives generally display a higher reactivity than their η 1 -allyl analogues, under the same experimental conditions. It is apparent that chloride in chlorinated solvents is a quite good nucleophile, and therefore it may force the allyl moiety to assume the monohapto coordination or partially displace the hemilabile bis-chelate DPPQ-Me ligand. This experimental finding was also theoretically confirmed by means of an ab initio DFT computation. The crystal structures of the complexes [Pd(η 3 -C 3 H 5 )- (DPPQ)]ClO 4 and [Pd(η 1 -C 3 H 5 )(DPPQ)Cl] were resolved. The latter represents the seventh structure of a palladium complex with a σ-coordinated allyl fragment described in the literature. Introduction The nucleophilic attack by “soft” nucleophiles, which usually occurs at the terminal carbon of the η 3 -coordinated allyl frag- ment in palladium complexes, has been extensively studied and reviewed, since this reaction represents an important methodol- ogy in the vast field of palladium-catalyzed organic synthesis. 1 In some cases different reaction products due to nucleophilic attacks governed by different stereo- 2 and regioselectivity 3 were proposed. Moreover, the allyl hapticity can be somehow influ- enced, and it is well known that the monohapticity of the allyl fragment may induce alternative and interesting mechanisms. 4 The allyl fragment may be forced to assume the monohapto configuration by potentially terdentate ligands or under the action of strong nucleophiles. 5 In particular, in the cases of terdentate ligands such as terpyridine and 2,6-(diphenylphos- phonylmethyl)pyridine the synthesis of stable complexes al- lowed X-ray structural determination. 5i,j It is however note- worthy that the synthesis of remarkably stable species and their consequent X-ray structural determinations were possible also for complexes bearing phospho- or phosphonite(oxazoline) (P-N) bidentate or potentially terdentate bis(oxazoline)phenyl- phosphonite (NOPON) ligands 5d-h (in the latter case the NOPON acts as a bidentate ligand with an uncoordinated wing). 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