Platinum(II)– and pailadium(II)–iron(0) complexes containing one bridging Ph2PCH2PPh2 ligand. Crystal structures of [(OC)3Fe(µ-Ph2PCH2PPh2)(µ-CO)PtBr2] and [(OC)3Fe(µ-Ph2PCH2PPh2)(µ-I)PtI]·CH2Cl2

Abstract

Treatment of [Fe(CO)₄(dppm-P)](dppm = Ph₂PCH₂PPh₂) with [PtX₂(cod)](X = Cl, Br, or Me; cod = cycle-octa-1,5-diene) gave bimetallics of type [(OC)₃Fe(µ-dppm)(µ-CO)PtX₂]. The structure of [(OC)₃Fe(µ-dppm)(µ-CO)PtBr₂](1b) was established by a single-crystal X-ray diffraction study; the crystals are monoclinic, space group P2₁/n, with a= 1 256.9(2), b= 1 780.6(2), c= 1 343.6(1) pm, β= 102.352(9)°, and Z= 4; final R factor 0.0271 for 3 386 observed reflections. The structure shows that there is a metal–metal bond [Fe–Pt 264.7(4) pm] formulated as a donor → acceptor bond, viz. Fe → Pt; additionally, one of the carbonyl ligands is semi-bridging. Treatment of (1b) with MeI gave [(OC)₃Fe(µ-dppm)(µ-I)PtI](2) quantitatively. Complex (2) was also prepared from [Fe(CO)₄(dppm-P)] and [PtI₂(cod)] and characterised by an X-ray diffraction study. Crystals of [(OC)₃Fe(µ-dppm)(µ-I)PtI]·CH₂Cl₂(2) are monoclinic, space group P2₁/c, with a= 991.3(2), b= 1 398.7(3), c= 2 356.8(4) pm, β= 95.96(1)°, and Z= 4; final R factor 0.0266 for 3 945 observed reflections. The structure shows that there is a metal–metal bond, best formulated as a donor-acceptor bond, viz. Fe → Pt, and that one of the iodide ligands symmetrically bridges the two metal centres. Treatment of (2) with PPh₃ quantitatively yields a new species, tentatively formulated as [(OC)₃Fe(µ-dppm)(µ-I)Pt(PPh₃)I]. Treatment of [Fe(CO)₄(dppm-P)] with [Pt(acac)(cod)]BF₄(acac = acetylacetonate) gave [(OC)₃Fe(µ-dppm)(µ-CO)Pt(acac)] BF₄ in 75% yield. Attempts to prepare some analogous palladium complexes are described.