Mono- and Dinuclear d10 Metal Complexes of Hexakis(3,5-dimethylpyrazolyl)cyclotriphosphazene. Synthesis, Structures, and Unusual Solution Dynamic Behavior

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Abstract
Synthesis, structures, and unusual solution dynamic processes of d10 metal complexes of hexakis(3,5-dimethylpyrazolyl)cyclotriphosphazene (L) are reported. Reaction systems with three MXn:L mole ratios (MXn = d10 metal halide) in CH2Cl2 have resulted in the formation of [ICu(μ,η3,η3-L)CuI] (1), [Cl2Zn(μ,η2,η3-L)ZnCl2] (2), [Cl2Cd(μ,η3,η3-L)CdCl2] (3), and [(η3-L)HgCl2] (4). These compounds were characterized by single crystal X-ray diffraction studies, and crystallographic data are given in the order of compound: crystal system; space group; unit cell parameters; Z; unique data (I > 2σ(I)); R1. 1·0.5CH2Cl2: monoclinic; P21/c; a = 8.268(4) Å; b = 22.365(5) Å; c = 23.325(8) Å, β = 93.06(1)°; 4; 5736; 4.82. 2·CH3CN: monoclinic; P21/c; a = 17.021(3) Å; b = 12.161(2) Å; c = 23.608(5) Å; β = 107.72(1)°; 4; 5469; 3.16. 3·CH2Cl2: monoclinic; P21/n; a = 18.585(5) Å; b = 17.585(4) Å; c = 14.404(3) Å; β = 102.71(2)°; 4; 3814; 3.65. The structure of 4 was attempted but resulted in data of low precision. Reaction of L with CuI and ZnCl2 in an equimolar ratio afforded [ICu(μ,η3,η3-L)ZnCl2] (5) which crystallizes in monoclinic space group P21/n with a = 22.876(5) Å, b = 21.594(4) Å, c = 9.177(2) Å, β = 93.54(2)°, Z = 4, and R1 = 7.00 for 3806 (I > 2σ(I)) data. In all cases, metal halide centers except the Td zinc site in 2 are coordinated by L via a κ3N binding core consisting of two nongeminal pyrazolyl nitrogen atoms and one phosphazene ring nitrogen atom. The η2-N2 coordination in 2 involves two geminal pyrazolyl nitrogen atoms. Factors which govern the nuclearity of the complex were partially demonstrated. The intermetallic distances in dinuclear metallophosphazenes range from 6.790 to 7.195 Å. The solution behavior of five compounds was studied by variable temperature 31P{1H}, 1H, and 113Cd FT NMR spectroscopy. Compounds 1 and 4 are associated with fluxional motions involving A2B low-temperature limit spectrum while compounds 2 and 5 show solvent-dependent dynamic processes with ABX and A2B low-temperature limit spectral patterns. Compounds 3 constitutes a fluxional system involving three A2B species. Accounts of solution NMR spectra were attempted by using PANIC, by assuming the formation of new solution metallophosphazene species and by considering several types of dynamic processes such as a ring-around type hopping motion for the κ3N metal site, a Td conformational change for the geminal pyrazolyl κ2N metal site, and a wigwag motion for the nongeminal pyrazolyl κ2N metal unit.