Palladium Phosphinothiolato Complexes. Syntheses and Crystal Structures of Mononuclear [PdCl(SC₂H₄PPh₂)PPh₃] and Binuclear [Pd₂Cl₂(μ-SC₃H₆PPh₂)₂] and Their Performance in Catalytic Carbonylation

Abstract

The phosphinothiolato complexes [PdCl(dppet)PPh(3)] (3), [Pd(dppet)(2)] (4), and [Pd(2)Cl(2)(dpppt-P,&mgr;-S)(2)] (6) (Hdppet = HSC(2)H(4)PPh(2); Hdpppt = HSC(3)H(6)PPh(2)) have been synthesized in good yield by various base-free ligand exchange reactions on Pd(II), but [Pd(dpppt)(2)] (5) could only be obtained as a pure product employing an oxidative route from Pd(0). Both complexes 3 ((31)P NMR, delta(P) 66.8 (dppet), 24.1 (PPh(3)); (2)J(PP) = 459 Hz) and 5 ((13)C NMR) are trans-P,P. Crystals of 3.CH(2)Cl(2) are orthorhombic (P2(1)2(1)2(1)), with a = 9.247(3) Å, b = 17.956(9) Å, c = 19.869(9) Å. In 3 the Pd-S distance of 2.270(2) Å is short compared to the very different Pd-P distances of 2.280(2) (Pd-PPh(2)R) and 2.343(2) Å (Pd-PPh(3)). Crystals of 6.CH(2)Cl(2) are monoclinic (P2(1)/n) with a = 12.701(3) Å, b = 12.040(4) Å, c = 22.495(2) Å, and beta = 97.36(1) degrees. The structure of 6 consists of two Pd(dpppt)Cl moieties meeting at an angle of 105.81(3) degrees, linked by asymmetric thiolato bridges in a syn-endo configuration. The difference in the chelate angles of dppet (85.98(9) degrees ) and dpppt (96.60(3) degrees and 97.42(3) degrees ) seems to be crucial for palladium to form an unusual mononuclear complex (3) or a binuclear complex (6). Bischelate complexes 4 and 5 are inactive, but 3 and 6 catalyze the hydroesterification of styrene with CO (30 bar) and MeOH at moderate temperatures (60 and 80 degrees C) with no additives. The velocities are slow, but with 6 and with 3 at the lower temperature no decomposition to Pd metal is observed. Only esters are produced and regioselectivities of ca. 84% toward 2-phenylpropanoic acid methyl ester are achieved.

Group 10 Metal Complexes of SPS‐Based Pincer Ligands: Syntheses, X‐ray Structures, and DFT Calculations

“…[26] Interestingly, 5 could also be used as a source of [Pd(SPSOH)Cl] (6) [SPS ϭ C 5 H(Ph 2 PS) 2 P] upon reaction with [Pd(COD)Cl 2 ] (Scheme 3). Scheme 3 Complex 6 was characterized by 31 P and 1 H NMR as well as by elemental data but was too insoluble to be characterized by 13 C NMR spectroscopy. Fortunately, suitable crystals for an X-ray crystal analysis could be grown by diffusing hexanes into a chloroform solution of the complex.…”

“…[8] Mainly, four types of sulfur ligands are used: classical thioethers, [9Ϫ12] thiolates, [13,14] sulfoxides, [15] in which coordination occurs through the remaining lone pair at sulfur, and phosphane sulfides. [16,17] The latter, though not yet employed in pincer type structures, have found an interesting application in the rhodium-catalyzed carbonylation of methanol when incorporated in a mixed PϪPϭS bidentate ligand.…”

A new P,S-coordinating ferrocenyl ligand: synthesis of a precursor and its coordination compounds with PdII and PtII

“…References: (a)Zhang et al (2001); (b)Brugat et al (1999); (c)Hall et al (1972); (d)Padilla et al (1991); (e)Dervisi et al (2003); (f)Albinati et al (1977); (g)Oilunkaniemi et al (2006); (h)Cao et al (1996); (i)Dey et al (2007); (j)Hauptman et al (1999).…”

Tuning diastereoisomerism in platinum(ii) phosphino- and aminothiolato hydrido complexes

“…Chelate assisted oxidative addition 4,13,22 of one equivalent of 2-(diphenylphosphino)ethanethiol (Hdppet, 1) to tetrakis(triphenylphosphine)platinum (0) gives the corresponding hydrido[2-(diphenylphosphino-kP)ethanethiolato-kS]triphenylphosphineplatinum(II) complex ([Pt(H)(dppet)(PPh 3 )], 8, Scheme 1). Complex 8 is isolated as a white solid in 68% yield and purified by recrystallization in dichloromethane/ether.…”