Cyclic Trinuclear Rh<sub>2</sub>M Complexes (M = Rh,
Pt, Pd, Ni) Supported by <i>meso</i>-1,3-Bis[(diphenylphosphinomethyl)phenylphosphino]propane
- Publication date
- Publisher
Abstract
Reaction of [MCl<sub>2</sub>(cod)] (M = Pd, Pt) with
a tetraphosphine, <i>meso</i>-1,3-bis[(diphenylphosphinomethyl)phenylphosphino]propane
(dpmppp), afforded the mononuclear complexes [MCl<sub>2</sub>(dpmppp)]
(M = Pd (<b>3a</b>), Pt (<b>3b</b>)), in which the dpmppp
ligand coordinated to the M ion by two inner phosphorus atoms to form
a six-membered chelate ring with two outer phosphines uncoordinated.
The pendant outer phosphines readily reacted with [RhCl(CO)<sub>2</sub>]<sub>2</sub> to give the cationic heterotrinuclear complexes [MRh<sub>2</sub>(μ-Cl)<sub>3</sub>(μ-dpmppp)(CO)<sub>2</sub>]X
(X = [RhCl<sub>2</sub>(CO)<sub>2</sub>], M = Pd (<b>4a</b>),
Pt (<b>4b</b>); X = PF<sub>6</sub>, M = Pd (<b>5a</b>),
Pt (<b>5b</b>)). The nickel analogue [NiRh<sub>2</sub>(μ-Cl)<sub>3</sub>(μ-dpmppp)(CO)<sub>2</sub>]PF<sub>6</sub> (<b>5c</b>) was also prepared. A neutral homotrinuclear Rh<sub>3</sub> complex,
[Rh<sub>3</sub>(μ-Cl)<sub>3</sub>(μ-dpmppp)(CO)<sub>2</sub>] (<b>6</b>), was synthesized by the reaction of [RhCl(CO)<sub>2</sub>]<sub>2</sub> with dpmppp and was further reacted with HgX<sub>2</sub> (X = Cl, Br, I) to afford the Rh<sub>3</sub>Hg tetranuclear
complexes [Rh<sub>3</sub>(HgX)(μ-Cl)<sub>2</sub>(μ-X)(μ-dpmppp)(CO)<sub>2</sub>]PF<sub>6</sub> (X = Cl (<b>7a</b>), Br (<b>7b</b>), I (<b>7c</b>)), where the Rh<sub>3</sub>(μ-Cl)<sub>2</sub>(μ-X) cores act as tridentate ligands to form three
donor–acceptor Rh→Hg interactions. The two CO ligands
of <b>7a</b>–<b>c</b> were replaced by XylNC to
yield [Rh<sub>3</sub>(HgX)(μ-Cl)<sub>2</sub>(μ-X)(μ-dpmppp)(XylNC)<sub>2</sub>]PF<sub>6</sub> (X = Cl (<b>8a</b>), Br (<b>8b</b>), I (<b>8c</b>)). The isocyanides had an appreciable influence
on the three Rh→Hg interactions, which was monitored by the <sup>2</sup><i>J</i><sub>HgP</sub> values observed in the <sup>31</sup>P{<sup>1</sup>H} NMR spectra and discussed on the basis of
DFT calculations. Complex <b>6</b> also reacted with CuCl and
HBF<sub>4</sub> to give [Rh<sub>3</sub>(CuCl)(μ-Cl)<sub>3</sub>(μ-dpmppp)(CO)<sub>2</sub>] (<b>9</b>) and [Rh<sub>3</sub>(μ<sub>3</sub>-H)(μ-Cl)<sub>3</sub>(μ-dpmppp)(CO)<sub>2</sub>]BF<sub>4</sub> (<b>10</b>), respectively. These results
suggested that the new tetraphosphine dpmppm proved quite useful in
constructing fine-tunable heterometallic frameworks
