Influence on reactivity of chloro ligand substitution in mononuclear cationic Pd(II) and Pt(II) triphos complexes: X-ray structure of the nitrate derivatives

摘要

The substitution of chloro ligand in [M(triphos)Cl]Cl complexes [M = Pd (1), Pt (2); triphos = Ph2PC2H4P(Ph)C2H4FPh2] by reaction with 1 equiv. of KX resulted in the formation of the ionic complexes [M(triphos)X]Cl [X = I, M = Pd (3), Pt (4); X = CN, M = Pd (5), Pt (6)1. Methanolic solutions of silver nitrate in excess displace the chloro ligand and counterion of 1 and 2, giving rise to the formation of the crystalline complexes [M(triphos)(ONO2)](NO3) [M = Pd (7), Pt (8)] suitable for X-ray diffraction studies. The complexes show a distorted square-planar environment around the metal, there being three coordination sites occupied by phosphorus atoms from the triphos and the fourth by the oxygen atom from a nitrate acting as monodentate ligand. A second NO3- is acting as counterion with D-3h symmetry. The use of a high excess of SnCl2 in the presence of 1 equiv. of PPh3 enabled the formation of complexes [M(triphos)(PPh3)](SnCl3)(2) [M = Pd (9), Pt (10)]. These complexes, in addition to [M(triphos)X]X [X = Br, M = Pd (1a), Pt (2a); X = I, M = Pd (1b), Pt (2b)], were synthesised and all Pt(II) complexes characterised by microanalysis. Mass spectrometry, IR spectroscopy, NMR spectroscopy and conductivity measurements were also used for characterisation. The structure and reactivity studies in solution were carried out by P-31(H-1) NMR. The trends in chemical shifts delta (P) and (1)J(Pt-195,P-31) coupling constants were used to establish a sequence in the X ligand exchange reactions. While [Pd(triphos)I]I (Ib) undergoes a ring-opening reaction by titration with AuI, the analogous Pt(II) complex (2b) does not react. The formation of new five-coordinate Pd(II) and Pt(II) complexes was observed by titration of 5-8 with potassium cyanide. (C) 2001 Elsevier Science B.V. All rights reserved. [References: 29]