NOVEL BASIC LIGANDS FOR THE HOMOGENEOUS CATALYTIC CARBONYLATION OF METHANOL .28. SYNTHESIS, PROPERTIES AND FLUXIONAL BEHAVIOR OF (ETHER-PHOSPHINE)PALLADIUM COMPLEXES

Cl2Pd(COD) (1) (COD = 1,5-cyclooctadiene) reacts with 1 equiv. of the (ether-phosphine) ligand Ph2P-approximately-D (2a-c) [D = CH2C4H7O (a), CH2C4H7O2 (b), CH2CH2OCH3 (c)] to give the dimeric complexes [mu-CIPd](Ph2P-approximately-D)]2 (3a-c) (P-approximately-D = ETA-1-P- coordinated). According to the field-desorption mass spectra hich show only one peak for the monomeric moieties Cl-Pd(Ph2P-approximately-D), 3a-c have a very weak Pd2Cl2 bridge. trans-Cl2Pd(Ph2P-approximately-D)2 (4a-c) is obtained either from 3a-c and 2a-c by cleaving the Pd2Cl2 bridge or from 1 and 2 equiv. of the ligands 2a-c. 4c crystallizes in the monoclinic space group P2(1)/c with Z = 2. AgClO4 selectively abstracts one Cl-ligand from 4a-c which results in the formation of the cationic complexes [trans-(Ph2P-cap-D)(Ph2P-approximately-Cl]+ (5a-c) (P-cap-D = ETA-2-D,P-coordinated) containing one chelated and one -ETA-1-P-bonded (ether-phosphine) ligand. 5a-c show fluxional behavior which is demonstrated by temperature-dependent P-31{H-1}-NMR investigations. The coalescence points have been determined and are at 253 (5a), 303 (5b), and 283 K (5c). The activation enthalpies-DELTA-G-not-equal-to are estimated at 48, 58, and 54 kj/mol. The abstraction of the second Cl-ligand from 5a-c succeeds only in the presence of AgSbF6 yielding the dicationic bis(chelate) complexes [trans-(Ph2P-cap-D)2Pd]2+ (6a-c). The latter are also obtained from 4a-c and AgSbF6. The hydrogenating properties of 3a-c and 4a-c toward 1-hexyne are investigated in comparison with trans-Cl2Pd(Ph2P-CH2CH2CH3)2.