Facile Access to Mono- and Dinuclear Heteroleptic
N‑Heterocyclic Silylene
Copper Complexes
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Abstract
Reaction of the heteroleptic N-heterocyclic
chlorosilylene L(Cl)Si:
(<b>1</b>; L = PhC(N<i>t</i>Bu)<sub>2</sub>) with
[Cu(tmeda)(CH<sub>3</sub>CN)][OTf] (<b>2</b>; tmeda = <i>N,N</i>,<i>N</i>′,<i>N</i>′-tetramethylethylenediamine,
OTf = OSO<sub>2</sub>CF<sub>3</sub> (triflate)) affords the Cu(I)
complex [L(Cl)Si:→Cu(tmeda)][OTf] (<b>3</b>) in high
yield as the first example of a heteroleptic N-heterocyclic silylene
copper complex. Similarly, the reaction of L(O<i>t</i>Bu)Si:
(<b>4</b>; L = PhC(N<i>t</i>Bu)<sub>2</sub>) with <b>2</b> affords [L(O<i>t</i>Bu)Si: → Cu(tmeda)][OTf]
(<b>5</b>) and that of L(NMe<sub>2</sub>)Si: (<b>6</b>) with <b>2</b> leads to [L(NMe<sub>2</sub>)Si:→Cu(tmeda)][OTf]
(<b>7</b>). Complex <b>3</b> shows a rather strong interaction
in the solid state between the O atom of the triflate anion and the
three-coordinate Cu(I) center with a Cu···O distance
of 2.312 Å. In contrast, complex <b>7</b> features only
a weak interaction (ca. 3.28 Å), while in complex <b>5</b> the cation and anion are fully separated. Strikingly, the reaction
of the chelating oxo-bridged silylene :Si(L)(μ<sub>2</sub>-O)(L)Si:
(<b>8</b>) with the copper source [Cu(CH<sub>3</sub>CN)<sub>4</sub>][OTf] (<b>9</b>) affords the dinuclear complex salt
[Cu<sub>2</sub>{η<sup>1</sup>:η<sup>1</sup>-LSi(μ<sub>2</sub>-O)SiL}<sub>2</sub>][OTf]<sub>2</sub> (<b>10</b>), featuring
a novel metallacyclooctane dication, selectively in a good yield.
Complex <b>10</b> also exhibits a very strong interaction between
the copper centers in the dication and the oxygen atoms of triflate
anions in the solid state, evidenced by a Cu···O separation
of only 2.141 Å. All complexes were fully characterized
