Synthesis of Homo- and Hetero-Bimetallic Arsenic Complexes by Means of Regioselective Monoinsertion of Alkynylarsane into the Pd-C Bond of a Palladacycle

Arsinocarbyne reactivity

The reactivity of the tungsten diphenylarsinocarbyne [W(CAsPh₂)(CO)₂(Tp*)] (1; Tp* = hydrotris(dimethylpyrazolyl)borato) is described. The pyramidal arsenic coordinates to a selection of 5d metal centres, forming heterobi- or trimetallic complexes with osmium(II), iridium(III), platinum(II) and gold(I). In the latter case, the WC bond provides a competitive site for gold(I) coordination. Treatment with MeOSO₂CF₃ results in methylation at arsenic to give the first example of an arsoniocarbyne, [W(CAsPh₂CH₃)(CO)₂(Tp*)]O₃SCF₃, for which only the WC bond remains available for gold(I) coordination.

C-H Activation in Primary 3-Phenylpropylamines: Synthesis of Seven-Membered Palladacycles through Orthometalation. Stoichiometric Preparation of Benzazepinones and Catalytic Synthesis of Ureas

The dimeric cyclometalated complexes [Pd2{κ(2)C,N-C6H4CH2CH2C(R)(Me)NH2-2}2(μ-Cl)2] (R = Me (1a), H (1b)) are prepared by reacting 1,1-dimethyl-3-phenylpropylammonium or 1-methyl-3-phenylpropylammonium triflate with Pd(OAc)2 in a 1:1 molar ratio and subsequent treatment with excess NaCl. The mononuclear derivatives [Pd{κ(2)C,N-C6H4CH2CH2C(R)(Me)NH2-2}Cl(L)] (L = PPh3, R = Me (3a), H (3b); L = 4-picoline (4-pic), R = Me (4a), H (4b)) were prepared from 1a,b by splitting the chloro bridges with the neutral ligands L. A conformational analysis of the mononuclear palladacycles in solution has been carried out. Insertion of CO takes place into the Pd-C bond of complexes 1a,b, affording Pd(0) and the tetrahydro-benzazepinone 5a or 5b, which possesses potential pharmacological interest. Additionally, the triflate salt A or B undergoes catalytic carbonylation with CO to afford the corresponding N,N'-dialkylurea, using Pd(OAc)2/Cu(OAc)2, in boiling acetonitrile. The crystal structures of 3a·(1)/2H2O, 3b, 4b·CHCl3, and 5a were determined by X-ray diffraction studies.