MOLECULAR-STRUCTURE AND DYNAMICS OF 1,3-DISTANNA-2-PLATINA-[3]FERROCENOPHANES

The reaction of bis(triphenyl-phosphane)(ethene)platinum(o) (1) with o rganotin compounds such as hexamethuyldistanne (2), 1,1,2,2-tetramethy l-1,2-distanna[2]ferrocenophane (3), bis(trimethylstannyl)ethyne (4'), and trimethylstannylelthynyl-bis(diethyl-amino)borane (4 '') affords- under liberation of ethene and cleavage of the Sn-Sn bond-the bis(trip henylphosphane)platinum(II) complexes 5a-8a. Displacement of the triph enylphosphane ligands (a) from the 2-bis(triphenylphosphane)platina[3] -ferrocenophane (6a) by various chelating diphosphanes [Ph2P(CH2)(n)PP h2 with n=1-3 (b, c, d, respectively), cis- Ph2PCH=CHPPh2 (e), Fe(C5H4 -PPh2)(2) (f), and 4,5- diphenylphosphinomethyl)2,2-dimethyl-1,3-dioxa lane (DIOP, g)] leads to the corresponding complexes 6b-6g in high yie ld. The molecular structure of the bis(diphenylphosphanyl)methane comp lex, [Pt{(SnMe2C5H4)2Fe}(Ph2PCH2PPh2)] (6b), was determined by X-ray s tructural analysis. The tetrahedral distortion of the square-planar co ordination sphere of the platinum atom in 6b (10.3 degrees) was found to be smaller than in 6a (20.6 degrees). All compounds were studied by multinuclear NMR spectroscopy in solution. Dynamic behavior (rotation of the PtP2 fragment about an axis passing through the platinum atom and bisection the PtSn2 triangle) was observed by NMR spectroscopy for 5a, 6a, and 6g, whereas 6b-6f have more rigid structures. There is no indication of a dynamic process in the case of 7a or 8a in which only one Pt-Sn bond is present.