1′-(Diphenylphosphino)-1-cyanoferrocene: A
Simple Ligand with Complicated Coordination Behavior toward Copper(I)
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Abstract
1′-(Diphenylphosphino)-1-cyanoferrocene
(<b>3</b>), a new donor-asymmetric ferrocene ligand obtained
in two steps from 1′-(diphenylphosphino)ferrocene-1-carboxaldehyde,
reacts with CuCl at a Cu/<b>3</b> molar ratio of 1:1 to give
the heterocubane complex [Cu(μ<sub>3</sub>-Cl)(<b>3</b>-κ<i>P</i>)]<sub>4</sub> (<b>4</b>). When the
Cu/<b>3</b> ratio is changed to 1:2 or 1:3, the reaction takes
a different course, producing the P,N-bridged dimer [CuCl(<b>3</b>-κ<i>P</i>)(μ(P,N)-<b>3</b>)]<sub>2</sub> (<b>5</b>) after crystallization. Notably, CuBr and CuI behave
differently, affording the corresponding 2D coordination polymers
[CuX(μ(P,N)-<b>3</b>)]<sub><i>n</i></sub> [X
= I (<b>7</b>), and Br (<b>8</b>)], regardless of the
Cu/<b>3</b> ratio. Reaction of <b>3</b> with sources of
naked Cu<sup>+</sup>, such as [Cu(MeCN)<sub>4</sub>]<sup>+</sup> salts
or their synthetic equivalents, provides the 1D coordination polymer
[Cu(MeCN-κ<i>N</i>)(μ(P,N)-<b>3</b>)][BF<sub>4</sub>] (<b>9</b>) or salts of a quadruply bridged dicopper(I)
cation, [Cu<sub>2</sub>(μ(P,N)-<b>3</b>)<sub>4</sub>]X<sub>2</sub> ([<b>10</b>]X<sub>2</sub>), depending on the Cu/<b>3</b> molar ratio (1:1 vs 1:2 and 1:3). Except for <b>4</b>, in which <b>3</b> binds as a simple P-monodentate ligand,
the complexes reported here represent the first structurally characterized
compounds in which a phosphinonitrile ligand coordinates through both
of its soft donor moieties, thereby extending the coordination chemistry
of these ligands
