Coordination Polymers Based on [CpFe([eta]5-P5)]: Solid-State Structure and MAS NMR Studies

Slow diffusion reactions of the pentaphosphaferrocene [Cp*Fe(η5-P5)] (Cp*=η5-C5Me5 (1)) with CuX (X=Cl, Br, I) in different stoichiometric ratios and solvent mixtures result in the formation of one- and two-dimensional polymeric compounds 2-6 with molecular formula [{Cu(µ-X)}{Cp*Fe(µ3,η5:η1:η1-P5)}]n (X=Cl (2a), I (2'c)), [{Cu(µ-I)}{Cp*Fe(µ3,η5:η1:η1-P5)}]n (3), [{CuX}{Cp*Fe(µ4,η5:η1:η1:η1-P5)}]n (X=Cl (4a), Br (4b), I (4c), Br (4'b), I (4'c)), [{Cu3(µ-I)2(µ3-I)}{Cp*Fe(µ5,η5:η1:η1:η1:η1-P5)}]n (5) and [{Cu4(µ-X)4(CH3CN)}{Cp*Fe(µ7,η5:η2:η1:η1:η1:η1:η1-P5)}]n (X=Cl (6a), Br (6b)), respectively. The polymeric compounds have been characterised by single-crystal X-ray diffraction analyses and, for selected examples, by magic angle spinning (MAS) NMR spectroscopy. The solid-state structures demonstrate the versatile coordination modes of the cyclo-P5 ligand of 1, extending from two to five coordinating phosphorus atoms in either σ or σ-and-π fashion. In compounds 2a, 2'c and 3, two phosphorus atoms of 1 coordinate to copper atoms in a 1,2 coordination mode (2a, 2'c) and an unprecedented 1,3 coordination mode (3) to form one-dimensional polymers. Compounds 4a-c, 4'b, 4'c and 5 represent two-dimensional coordination polymers. In compounds 4, three phosphorus atoms coordinate to copper atoms in a 1,2,4 coordination mode, whereas in 5 the cyclo-P5 ligand binds in an unprecedented 1,2,3,4 coordination mode. The crystal structures of 6a,b display a tilted tube, in which all P atoms of the cyclo-P5 ligand are coordinated to copper atoms in σ- and π-bonding modes.