Rufińska, Anna
Goddard, Richard
Weidenthaler, Claudia
Bühl, Michael
Pörschke, Klaus-Richard
Structural Properties and Dynamics of Five-Coordinate
Nickel(II)−π-Allyl Complexes Containing Monodentate Phosphorus
Ligands
The novel ionic pentacoordinate Ni<sup>II</sup>−π-allyl complexes [(η<sup>3</sup>-C<sub>3</sub>H<sub>5</sub>)Ni(PMe<sub>3</sub>)<sub>3</sub>]Y (<b>1a</b>−<b>d</b>) and [(η<sup>3</sup>-C<sub>3</sub>H<sub>5</sub>)Ni{P(OMe)<sub>3</sub>}<sub>3</sub>]Y (<b>2a</b>−<b>d</b>) (Y = SO<sub>3</sub>CF<sub>3</sub> (<b>a</b>), PF<sub>6</sub> (<b>b</b>), Br (<b>c</b>), I (<b>d</b>)) have been synthesized and
investigated by DSC, solid-state NMR, and X-ray single-crystal and powder diffractometry. Apart from
<b>1a</b>, all complexes are polymorphic. The PMe<sub>3</sub> complexes <b>1b</b>−<b>d</b> undergo monoclinic-monoclinic phase
transitions. The solid-state structures of <b>1a</b> and <b>1b-II</b> are rigid at low temperature but fluxional at ambient
temperature, whereas those of <b>1c-II</b> and <b>1d-II</b> are almost rigid, while somewhat faster dynamics occur
for <b>1c-I</b> and <b>1d-I</b>. Similarly, the structures of <b>2c-II</b> and <b>2d-II</b> are fully or almost fully rigid at ambient
temperature. The properties of the P(OMe)<sub>3</sub>-ligated OTf and PF<sub>6</sub> salts <b>2a</b>,<b>b</b> are completely different. <b>2a</b>
crystallizes in the triclinic phase <b>2a-II</b>, which transforms at −21 °C into the highly mobile, plastically
crystalline mesophase <b>2a-I</b> with a cubic primitive cell. <b>2b</b> crystallizes from solution in the monoclinic
phase <b>2b-III</b>, having a rigid structure, and transforms at ambient temperature reversibly into the similarly
crystalline phase <b>2b-II</b>, which undergoes slow dynamics. Heating either phase to 53 °C gives rise to the
plastically crystalline mesophase <b>2b-I</b>. For complexes <b>1a</b>−<b>d</b> (all phases) and the phases <b>2a-II</b> and <b>2b-II</b>
the solid-state dynamics start with turnstile rotation of the three phosphorus ligands. For the mesophases
<b>2a-I</b> and <b>2b-I</b> additional π-allyl ligand mobility has been established and anion mobility must also be
assumed. DFT MO calculations on the cations <b>1</b> and <b>2</b> and the parent PH<sub>3</sub> complex <b>3</b> gave low rotational
barriers of up to 3.5 kcal/mol in the gas phase. Complexes <b>2a</b>,<b>b</b> are rare examples of metallorganic
plastic crystals (dynamically disordered mesophases).
dynamic;PF 6 salts 2;phase;metallorganic plastic crystals;DSC;parent PH 3;Ni;C 3 H 5;3 CF 3;ambient temperature;NMR;ambient temperature reversibly;DFT MO calculations;complex;mesophase;II;2 b crystallizes
2006-04-24
https://acs.figshare.com/articles/Structural_Properties_and_Dynamics_of_Five_Coordinate_Nickel_II_Allyl_Complexes_Containing_Monodentate_Phosphorus_Ligands/3226186

10.1021/om0601807.s003