Komplexe mit Kohlenstoffsulfiden und -seleniden als Liganden: XXII. Homo- und Heterometallische Zweikernkomplexe des Platins und Palladiums mit den Struktureinheiten M(μ-E)M′(CE′) und M(μ-CEE′)M′ (M, M′ = Pd, Pt; E, E′ = S, Se)

Abstract

The platinum and palladium chelate complexes M(η 2-CSE)(P ⌢ P) (I–IV) with E = S or Se react with Pt(C 2H 4)(PPh 3) 2 or Pt(PPh 3) 4 in acetone at room temperature to give the dinuclear sulfido- or selenido-bridged thiocarbonyl compounds (P ⌢ P)M(μ-E)Pt(CS)(PPh 3) (VI–IX). The diplatinum complex (Ph 3P) 2Pt(μ-Se)Pt(CS)(PPh 3) (X) can be similarly prepared. The X-ray structure analysis of (dpmb)Pt(μ-Se)(Pt(CS)(PPh 3) (VIII) (dpmb = 1,2-C 6H 4(CH 2PPh 2) 2) reveals a distorted square-planar coordination at both metal atoms, and an isosceles Pt 2Se triangle in the centre of the molecule. The PtPt distance is 266 pm and the ligated CS is found trans to Se. The reactions of Pt(η 2-CE 2)(dpmb) (XI, XIII) and Pt(η 2-CE 2)(PPh 3) 2 (XII, XIV) with Pt(C 2H 4)(PPh 3) 2 or Pt(PPh 3) 4 lead to the formation of the dinuclear complexes (L′ 2)Pt(μ-CE 2)Pt(PPh 3) 2 (XV–XVIII) which in contrast to VI–X contain an intact CS 2 or CSE 2 molecule in bridging position. The corresponding heterometallic compounds (dpmb)Pd(μ-CEE′)Pt(PPh 3) 2 (XXII–XXIV) with CEE′ = CS 2, CSSe, and CSe 2 have been obtained from the reaction of Pd(η 2-CEE′)(dpmb) (XIX–XXI) with Pt(C 2H 4)OPPh 3) 2. Treatment of VI, VIII and IX with dpmb or diphos ( = 1,2-C 2H 4(PPh 2) 2) leads to recombination of the heteroallene unit and thus to formation of the CS 2 and CSSe bridged complexes (P ⌢ P)M(μ-CSE)Pt(P ⌢ P) (XXV–XXVII). In contrast, the reaction of (diphos)Pt(μ-Se)Pt(CS)(PPh 3)(VII) with diphos gives a dinuclear compound XXVIII to which the structure (diphos)Pt(μ-Se)(μ-CS)Pt(diphos) is tentatively assigned. A general mechanistic scheme is proposed to account for the different types of products obtained from the reaction of M(η 2-CEE′)(L′ 2) with [Pt(PPh 3) 2] and those obtained subsequently from the reaction of (L′ 2)M(μ-E)Pt(CS)(PPh 3) with chelating phosphines.