Stannylenes based on pyrrole-phosphane and dipyrromethane-diphosphane scaffolds: syntheses and behavior as precursors to PSnP pincer palladium(II), palladium(0) and gold(I) complexes.

2-Ditertbutylphosphanylmethylpyrrole (H2pyrmPtBu2) and 2,2'-bis(diisopropylphosphanylmethyl)-5,5'-dimethyldipyrromethane ((HpyrmPiPr2)2CMe2) have been used to synthesize new P-donor-stabilized stannylenes in which the Sn atom is attached to one, SnCl(HpyrmPtBu2) (1) and Sn{N(SiMe3)2}(HpyrmPtBu2) (2), or two pyrrolyl-phosphane scaffolds, Sn(HpyrmPtBu2)2 (3), or to a dipyrromethane-diphosphane scaffold, Sn(pyrmPiPr2)2CMe2 (4). It has been found that stannylenes 3 and 4 are excellent precursors to transition metal complexes containing PSnP pincer-type ligands. Their reactions with chlorido transition metal complexes have afforded [PdCl{κ3P,Sn,P-SnCl(HpyrmPtBu2)2}] (6), [PdCl{κ3P,Sn,P-SnCl(pyrmPiPr2)2CMe2}] (7) and [Au{κ3P,Sn,P-SnCl(HpyrmPtBu2)2}] (8), which contain a PSnP pincer-type chloridostannyl ligand. While complexes 6 and 7 are square-planar palladium(II) complexes, compound 8 is an uncommon gold(I) complex having a T-shaped coordination geometry with a very long Sn-Au bond (3.120 Å). The T-shaped palladium(0) complex [Pd{κ3P,Sn,P-Sn(pyrmPiPr2)2CMe2}] (9), which contains an unprecedented PSnP pincer-type stannylene that behaves as a Z-type (σ-acceptor) ligand, has been prepared from 4 and [Pd(η3-C3H5)(η5-C5H5)].