Exceptional Coordination Mode of Unsaturated PNP Ligands (Me3Si)2C=PN(R)PPh2 with Palladium and Platinum Dichlorides: Insertion of Phosphaalkene Phosphorus Atoms into Metal–Chlorine Bonds

Unique molecular bis-chelate complexes M[(Me3Si)2C=P(Cl)N(1-Ada)PPh2]2 (1-Ada = 1-adamantyl; 3: M = Pt; 4: M = Pd) were isolated as crystalline solids from solutions that contain mixtures of products from reactions of the metal dichlorides with the P-phosphanylaminophosphaalkene (Me3Si)2C=PN(1-Ada)PPh2 (1). Attachment of chloride ions to PdII- and PtII-coordinated 1 leads to the novel anionic (alkylidene)(chlorido)(phosphanylamino)phosphanido ligand [(Me3Si)2C=P(Cl)N(1-Ada)PPh2]–, which contains a stereogenic phosphorus atom. With PdCl2(COD), only the centrosymmetric (R,S) isomer 4a was isolated, whereas three of the four possible isomeric platinum complexes Pt[(Me3Si)2C=P(Cl)N(1-Ada)PPh2]2 (3a–3c) were investigated crystallographically. DFT calculations on model compounds indicate that the enhanced electrophilicity of the chelating phosphaalkene ligand 1 leads to chlorine migration from the metals to the phosphaalkene phosphorus atom.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)