Heterobimetallic complexes containing methylaminobis(difluorophosphine)
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Description
The directed synthesis of heterobimetallic complexes containing methylaminobis(difluorophosphine)(=PNP) has been explored. The results demonstrate that 'metalloligands' containing PNP such as $\rm cpFe\lbrack CH\sb3 N(PF\sb2)\sb2\rbrack\sb2 Cl,\ cpRU\lbrack CH\sb3 N(PF\sb2)\sb2\rbrack\sb2 Cl,\ Re(CO)\sb3\lbrack CH\sb3 N(PF\sb2)\sb2\rbrack\sb2 Br,\ Mo(CO)\sb3\lbrack CH\sb3 N(PF\sb2)\sb2\rbrack\sb2,$ are moderately good precursors to heterobimetallic transition metal compounds. In many cases, good yields of products were achieved. The preparations, spectroscopic data, and X-ray structural analyses of the products are described in this paper The chemistry of $\rm cpFe\lbrack CH\sb3 N(PF\sb2)\sb2\rbrack\sb2 Cl,\ and\ cpRu\lbrack CH\sb3 N(PF\sb2)\sb2\rbrack\sb2 Cl$ features chloride transfer from Fe to other metals when it was reacted with low valent transition metal complexes. The heterobimetallic products are regarded as combined results of coordination and oxidative addition reactions. When $\rm cpFe\lbrack CH\sb3 N(PF\sb2)\sb2\rbrack\sb2 Cl$ reacts with $\rm Pt(Ph\sb2 C\sb2)(PPh\sb3)\sb2,$ the complex $\rm PtCl(PPh\sb3)(\mu$-$\rm PF\sb2)(\mu$-$\rm PF\sb2 NMe)$-$\rm Fe(PF\sb2 NHMe)cp,$ i.e. a product with the cleavage of PNP, was generated. An interesting feature of this product is that it contains a bridging 'PF$\sb2$' group between Pt and Fe atoms whose phosphorus resonance has a very low-field shift as compared with the $\sp{31}$P resonance of the intact -PF$\sb2$ of PNP on platinium. The reaction of $\rm cpRu\lbrack CH\sb3 N(PF\sb2)\sb2\rbrack\sb2 Cl$ with $\rm Pt(Ph\sb2 C\sb2)(PPh\sb3)\sb2$ gave similar products to those of $\rm cpFe\lbrack CH\sb3 N(PF\sb2)\sb2\rbrack\sb2 Cl,$ as indicated by the same pattern in its $\sp{31}$P NMR spectrum, but the products could not be successfully isolated $\rm Re(CO)\sb3\lbrack CH\sb3 N(PF\sb2)\sb2\rbrack\sb2 Br$ behaves similarly to $\rm cpRu\lbrack CH\sb3 N(PF\sb2)\sb2\rbrack\sb2 Cl$ and $\rm cpFe\lbrack CH\sb3 N(PF\sb2)\sb2\rbrack\sb2 Cl$ in regard to 'halide transfer problems' during the reactions, but it seems less oxidative toward the reactants. Its reactions with $\rm Pt(Ph\sb2 C\sb2)(PPh\sb3)\sb2$ gave expected products instead of ligand cleavage products as compared with the reaction of 'Ru-PNP' or 'Fe-PNP' compound $\rm MO(CO)\sb3\lbrack CH\sb3 N(PF\sb2)\sb2\rbrack\sb2$ didn't show any 'transfer' or oxidation problems because it does not contain any transferable group and molybdenum here is zero-valent. In reaction with other reactants the chelating ring of PNP opens and the complex acts like a 'bis-PNP' precursor to attack other reactants. Its reactions with other transition metal complexes containing labile ligands give good yields of desired heterobimetallic products in many cases The potential problems with the methods using 'Fe-PNP', 'Ru-PNP', or 'Re-PNP' as precursors are the 'halide transfer', which render the products rather unreactive because most products are coordinatively saturated The electronic spectral and electrochemical properties of some of the products were studied. Reactivity of the heterobimetallic compounds with small organic molecules such as dimethyl acetylenedicarboxylate and phenylacetylene was also explored. Unfortunately, no reactivity was found