The role of hydrogen-bonding interactions in stabilising trigonal planar copper(I) in Cu(BF4)-pyridazine-nitrile systems

TY - JOUR

T1 - The role of hydrogen-bonding interactions in stabilising trigonal planar copper(I) in Cu(BF4)-pyridazine-nitrile systems

AU - Batsanov, A S

AU - Begley, M J

AU - George, M W

AU - Hubberstey, P

AU - Munakata, M

AU - Russell, C E

AU - Walton, P H

PY - 1999

Y1 - 1999

N2 - Regardless of conditions, reaction of [Cu(NCMe)(4)][BF4] with pyridazine (pydz) or 3-methylpyridazine (Mepydz) in MeCN or with pydz in PhCN invariably gave tris-bridged dinuclear cations, [{Cu(NCR)}(2)(mu-diimine)(3)](2+). Structural analysis, by single crystal X-ray diffraction, of complexes containing [{Cu(NCMe)}(2)(mu-pydz)(3)](2+), [{Cu(NCMe)}(2)(mu-Mepydz)(3)](2+) and [{Cu(NCPh)}(2)(mu-pydz)(3)](2+) confirmed the presence of two tetrahedral copper(I) centres bridged by three pyridazine molecules and terminally co-ordinated by nitriles. This chemistry contrasts with that for 2-cyanoguanidine (cnge), a planar nitrile with considerable hydrogen-bonding potential, which leads to both bis- and tris-bridged dinuclear cations, [{Cu(cnge)}(2)(mu-pydz)(2)](2+) and [{Cu(cnge)}(2)(mu-pydz)(3)](2+). Whereas the tris-bridged cation is based on four-co-ordinate tetrahedral copper(I), the bis-bridged cation contains three-co-ordinate trigonal planar copper(I). The unique ability of cnge to stabilise co-ordinatively unsaturated copper(I) in the solid state with pydz bridged dications is attributed to the formation of an extended 2-D sheet architecture based on hydrogen-bonding intermolecular interactions. This type of molecular construction, which is common to all copper(I)-cnge three-co-ordinate structures, suggests that the three-co-ordinate geometry is not an intrinsic property of copper(I) systems but a result of the efficient packing of parallel two-dimensional sheets. Treatment of [{Cu(NCMe)}(2)(mu-diimine)(3)](2+) with CO led to [{Cu(CO)}(2)(mu-diimine)(3)](2+); reaction of [{Cu(cnge)}(2)(mu-diimine)(2)](2+) with CO or PPh3 gave [{Cu(cnge)(L)}(2)(mu-diimine)(2)](2+) (L=CO or PPh3). Recrystallisation of [{Cu(cnge)(PPh3)}(2)(mu-diimine)(2)](2+) yielded a variety of crystalline products including [Cu(pydz)(2)(PPh3)(2)][BF4] and [{Cu(PPh3)}(2)(mu-pydz)(3)][PF6](2). Structural studies confirmed the former to be a mononuclear cation with four monodentate (two pydz and two Ph3P) ligands and the latter to be a tris(mu-pydz) dinuclear cation with terminal Ph3P molecules. The copper(I) co-ordination geometries in both complexes are tetrahedral, the three-co-ordinate copper(I) geometry of [{Cu(cnge)}(2)(mu-diimine)(2)](2+) being lost on treatment with Ph3P. In the absence of structural data, [{Cu(CO)}(2)(mu-diimine)(3)](2+) and [{Cu(cnge)(CO)}(2)(mu-diimine)(2)](2+) are considered to comprise tris- and bis-(mu-diimine) dinuclear cations based on tetrahedral copper(I) with terminal CO.

AB - Regardless of conditions, reaction of [Cu(NCMe)(4)][BF4] with pyridazine (pydz) or 3-methylpyridazine (Mepydz) in MeCN or with pydz in PhCN invariably gave tris-bridged dinuclear cations, [{Cu(NCR)}(2)(mu-diimine)(3)](2+). Structural analysis, by single crystal X-ray diffraction, of complexes containing [{Cu(NCMe)}(2)(mu-pydz)(3)](2+), [{Cu(NCMe)}(2)(mu-Mepydz)(3)](2+) and [{Cu(NCPh)}(2)(mu-pydz)(3)](2+) confirmed the presence of two tetrahedral copper(I) centres bridged by three pyridazine molecules and terminally co-ordinated by nitriles. This chemistry contrasts with that for 2-cyanoguanidine (cnge), a planar nitrile with considerable hydrogen-bonding potential, which leads to both bis- and tris-bridged dinuclear cations, [{Cu(cnge)}(2)(mu-pydz)(2)](2+) and [{Cu(cnge)}(2)(mu-pydz)(3)](2+). Whereas the tris-bridged cation is based on four-co-ordinate tetrahedral copper(I), the bis-bridged cation contains three-co-ordinate trigonal planar copper(I). The unique ability of cnge to stabilise co-ordinatively unsaturated copper(I) in the solid state with pydz bridged dications is attributed to the formation of an extended 2-D sheet architecture based on hydrogen-bonding intermolecular interactions. This type of molecular construction, which is common to all copper(I)-cnge three-co-ordinate structures, suggests that the three-co-ordinate geometry is not an intrinsic property of copper(I) systems but a result of the efficient packing of parallel two-dimensional sheets. Treatment of [{Cu(NCMe)}(2)(mu-diimine)(3)](2+) with CO led to [{Cu(CO)}(2)(mu-diimine)(3)](2+); reaction of [{Cu(cnge)}(2)(mu-diimine)(2)](2+) with CO or PPh3 gave [{Cu(cnge)(L)}(2)(mu-diimine)(2)](2+) (L=CO or PPh3). Recrystallisation of [{Cu(cnge)(PPh3)}(2)(mu-diimine)(2)](2+) yielded a variety of crystalline products including [Cu(pydz)(2)(PPh3)(2)][BF4] and [{Cu(PPh3)}(2)(mu-pydz)(3)][PF6](2). Structural studies confirmed the former to be a mononuclear cation with four monodentate (two pydz and two Ph3P) ligands and the latter to be a tris(mu-pydz) dinuclear cation with terminal Ph3P molecules. The copper(I) co-ordination geometries in both complexes are tetrahedral, the three-co-ordinate copper(I) geometry of [{Cu(cnge)}(2)(mu-diimine)(2)](2+) being lost on treatment with Ph3P. In the absence of structural data, [{Cu(CO)}(2)(mu-diimine)(3)](2+) and [{Cu(cnge)(CO)}(2)(mu-diimine)(2)](2+) are considered to comprise tris- and bis-(mu-diimine) dinuclear cations based on tetrahedral copper(I) with terminal CO.

KW - COORDINATIVELY UNSATURATED COPPER(I)

KW - CRYSTALLOGRAPHIC EVIDENCE

KW - DIMERIC CATION

KW - C-H...O

KW - COMPLEXES

KW - 3-COORDINATE

KW - 2-CYANOGUANIDINE

KW - CRYSTALS

KW - FLUORINE

KW - CENTERS

M3 - Article

SN - 1472-7773

SP - 4251

EP - 4259

JO - JOURNAL OF THE CHEMICAL SOCIETY-DALTON TRANSACTIONS

JF - JOURNAL OF THE CHEMICAL SOCIETY-DALTON TRANSACTIONS

IS - 23

ER -