We present the synthesis of 7‐(diphenylphosphine)‐indole 1 (HPinol) as a novel mono‐ and bidentate P‐ and N, P‐ligand and its coordination chemical behaviour towards the d6‐ and d8‐transition metals rhodium(III), palladium(II) and rhenium(I). The reaction of 1 with [Cp*RhCl2]2 in a 1:2 molar ratio leads to the formation of the P‐coordinated complex [RhCl2(P–(HPinol))] (2). In the presence of the weak base NEt3, HCl elimination occurs by forming the neutral amido‐phosphine chelated complex [RhCl(N, P–(Pinol))] (3). The same P‐ and N, P‐coordination is observed for palladium(II), where two ligands 1 coordinate to the metal centre forming the neutral complexes [PdCl2(P–HPinol)2] (4) and [Pd(N, P–Pinol)2] (5). The reaction of Re(CO)5Br in the presence of NEt3 and PPh3 delivers the amido‐phosphine complex [Re(CO)3PPh3(N, P–Pinol)] (6). All products were characterised by multinuclear NMR spectroscopy, MS and IR spectra as well as elemental analysis. Furthermore, crystal structures of ligand 1 and all complexes 2–6 are presented.
The reaction of the azaphospholes 5‐methyl‐2‐phenyl‐1,2,3‐diazaphospole (PDAP) and 2‐methyl‐2‐phenyl‐1,2,4,3‐triazaphospole (PTAP) with the dimers [LMCl2]2 (LM = η6‐C6Me6Ru, η5‐C5Me5Ir) of ruthenium(II) and iridium(III) only occurs in presence of nucleophiles such as EtOH or H2O leading to their metal‐coordination after cleavage of the dimers. [(η6‐C6Me6)RuCl2]2 reacts with PDAP and EtOH in the molar ratio 0.5:1:1 to give the phosphorus‐coordinated complex (η6‐C6Me6)RuCl2(P‐PDAP·EtOH) (1). In the case of [(η5‐C5Me5)IrCl2]2, the triazaphosphole PTAP was used in the presence of EtOH or H2O yielding the analogous products (η5‐C5Me5)IrCl2(P‐PTAP·EtOH) (2) or (η5‐C5Me5)IrCl2(P‐PTAP·H2O) (3). In 1–3, the former aromatic azaphosphole (σ2,λ3‐P) has been converted by 1,2 addition of EtOH or H2O to their P=C or P=N double bond with the nucleophiles EtO– and OH– bonded to phosphorus (σ3,λ3‐P). Complexes 1–3 with a piano‐stool configuration were characterized by elemental analysis, 31P NMR spectroscopy and single‐crystal X‐ray diffraction.
This theoretical study addresses the experimentally known fact that the ligand system 1-(2-(diphenylphosphino)benzylidene)-2-phenylhydrazine (L) coordinates to palladium centers via the N atom as a 1-methylenehydrazine ligand. In the case of platinum, a 1,2-H shift occurs, and a coordination via the C atom of the newly formed 1-carbenehydrazine ligand is observed. DFT calculations show that the free 1-methylenehydrazine ligand is favored over the free 1-carbenehydrazine ligand by ca. 42 kcal mol(-1). Coordination to a metal center, however, lowers this energy difference to ca. 8-14 kcal mol(-1) in the case of Pd and to essentially zero for Pt.
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