Alkynyl/chloride exchange between trans-platinum(II) and -palladium(II) chlorides and alkynylstannanes. Crystal structure of trans-[bis(1-propynyl)-bis(triethylphosphine)platinum(II)

Abstract

The reaction between alkynylstannanes ( 3, 4) and trans-[(Et 3P) 2Pt(Cl) 2] ( 1) gives trans-[(Et 3P) 2Pt(Cl)CCR] ( 5) or trans-[(Et 3P) 2Pt(CCR 1) 2 ( 6) in high yield (R 1  H, Me, Ph). Complexes 5 react with alkynylstannanes to give the unsymmetrical bis(alkynyl) complexes 7, trans-[(Et 3P) 2Pt(CCR 2)CCR 1] (R 1  Me, Ph; R 2  H). Although the palladium(II) dichloride 2, trans-[(Bu 3P) 2PdCl 2], reacts much faster with alkynylstannanes than 1, the compounds trans-[(Bu 3P) 2Pd(CCR 1) 2] ( 9) are always obtained as mixtures with trans-[(Bu 3P) 2Pt(Cl)CCR 1] ( 8), except for R 1  H. Compounds 8 can be obtained pure R 1  Me or t-Bu if the reaction between 2 and 3 is carefully controlled. The dependence of the product distribution under experimental conditions in the case of the palladium(II) acetylides indicates that oxidative addition-reductive elimination reactions are involved. The crystal structure of trans-[(Et 3P) 2Pt(CCMe) 2] ( 6b) has been determined. All the products have been characterized by 13C, 31P and 195Pt NMR spectroscopy.