a b s t r a c tFirst (G1)-and second-generation (G2) poly(propyleneimine) (PPI) dendrimers were reacted with 2-(diphenylphosphino)benzaldehyde, to form iminophosphine-functionalised dendritic ligands (1, 2). The reaction of the dimeric precursor [RhCl(CO) 2 ] 2 with the heterobidentate dendritic ligands 1, 2 gave the corresponding rhodium(I) complexes (3, 4). There has been recent interest in the chemistry of polydentate ligands, especially those which combine ''soft" and ''hard" donor atoms [11]. The most used hemilabile ligands are the P,N-donor bidentate ligands, combining the distinct behaviour of a soft phosphorus atom which coordinates very strongly to a soft metal centre (e.g. palladium) and a hard nitrogen donor which is weakly bound. Non-rigid ligands, such as the widely studied iminophosphines, often act as chelating ligands that easily form five-or six-membered chelate rings. Iminophosphines display versatile coordination behaviour and are potentially hemilabile, making them useful for a variety of homogeneous processes, such as, C-C coupling reac- [16]. The steric and electronic properties of such ligands can also be fine-tuned and this can have a huge effect on the kinetics and thermodynamics of a chemical reaction [17].Examples of metallodendritic chelating heterobidentate complexes are rare. For metallodendrimers containing P and N donor atoms, many transition metals are coordinated in a P-monodentate or N-monodentate fashion. In this communication, we report on the synthesis of first-and second-generation chelating, heterobidentate [P, N] iminophosphine dendritic ligands and their coordination chemistry with a Rh(I) precursor. The molecular structure of a mononuclear analogue is also presented and discussed.The synthesis of the first-and second-generation iminophosphine-functionalised dendritic ligands 1 and 2 ( Fig. 1) [19] was achieved by a Schiff-base condensation reaction of the commercially available DAB-dendr-(NH 2 ) n with 2-diphenylphosphinobenzaldehyde. Screttas et al. first reported the synthesis of a third generation iminophosphine dendritic ligand based on a poly(propyleneimine) scaffold [18]. These dendritic P,N ligands were used in situ in the presence of palladium acetate in the Heck cross-coupling of p-anisyl bromide with styrene.The dendritic ligands (1, 2) were isolated as pale yellow solids in moderate yields (65-68%). These compounds were characterized by elemental analysis (C, H, N) Published in Inorganic Chemistry Communications 12, issue 8, 716-719, 2009 which should be used for any reference to this work 1imine moiety are observed as a triplet around 3.69 ppm, for 1 and 2. The appearance of a singlet at ca. 8.37 ppm, assigned to the imine proton (-CH 2 N@CH-CH 2 -) establishes that the condensation reaction has occurred. As was the case for Screttas and co-workers, it is important to consider syn and anti isomerism about the imine double bond [18]. One resonance is noted for the imine proton in both ligands, assigned to the trans isomer for steric reasons. The 31 P{ 1 H} ...
