Mikael Håkansson

ISOLATION AND SPONTANEOUS RESOLUTION OF EIGHT-COORDINATE STEREOISOMERS

The right- and left-handed propeller-shaped enantiomers of the eight-coordinate SmI(2) complexes shown can be resolved by crystallization from dimethoxyethane (dme) at ambient temperature. Apart from representing a new type of chiral metal complex, such enantiomers are potential reagents for enantioselective reductions.

Copper(I) alkoxides: preparation and structural characterisation of triphenylmethoxocopper(I) and of an octanuclear form of t-butoxocopper(I)

Two copper(I) alkoxides, the novel compound triphenylmethoxocopper(I) and an octanuclear form of t-butoxocopper(I), have been prepared from mesitylcopper(I) and the relevant alcohol. [Cu-4(OCPh3)(4)]. 2C(6)H(5)CH(3) (1) and [Cu-8((OBu)-Bu-t)(8)] (2) have been characterised by means of crystal structure determination. Compound 1 contains two crystallographically independent triphenylmethoxocopper(I) molecules, each with a planar Cu-4 core. The Cu4O4 unit is butterfly-shaped with the oxygen ligands situated alternately approximately 0.4 Angstrom above and below the plane through the copper atoms, and the triphenylmethyl groups spread out over both sides of the Cu4O4 core. The copper(I) centres are two-coordinated with distances of 1.83(1)-1.86(1) Angstrom and O-Cu-O angles of 169.4(5)degrees. [Cu-8((OBu)-Bu-t)(8)] (2) can be described as being composed of two approximately planar Cu4O4 cores, each with the t-butyl groups bent away in the same direction from the Cu4O4 plane. These units are related to one another by a centre of symmetry and with weak Cu-O interactions of 2.493(5) and 2.536(5) Angstrom, involving four of the eight coppers, thus yielding an octanuclear Cu8O8 core. These four copper(I) centres thus attain T-shaped three-coordination by oxygen, whereas the remaining four are approximately linearly coordinated. The short Cu-O bond lengths in 2 range from 1.844(5) to 1.888(5) Angstrom.

A comparative study of 1,7-octadiene and 1,7-octadiyne complexes of copper(I) chloride: preparation and molecular structures

Abstract Polymeric complexes, [Cu 2 Cl 2 (C 8 H 14 )] ( 1 ) and [Cu 2 Cl 2 (C 8 H 10 )] ( 2 ), prepared by direct reaction between copper(I) chloride and 1,7-octadiene and 1,7-octadiyne, respectively, have been between characterized by crystal-structure determinations and IR spectroscopy. In both structures the organic ligands act as bridges between copper(I). In 1 , there are two cystallographically independent copper(I) centres, one of which is three coordinated by CC and two chloride ligands, the olefin being twisted 4° out of the coordination plane. The other copper(I) centre is (3 + 1) coordinated and exhibits a larger olefin twist (10° from the trigonal plane). The CuC bond lengths lie in the range 2.036(4)-2.100(4) A, and the CC bond lengths are 1.353(6) and 1.356(6) A. In 2 , copper(I) is trigonally pyramidally coordinated, with the CC linkage in the trigonal plane; CuC = 2.029(6) and 2.053(6) A and CC = 1.196(9) A. The v (CC) and v (CC) frequencies are lowered by ca. 98 cm −1 and 135 cm −1 , respectively, on complexation. In contrast to v (C sp 2 H), which remains virtually unchanged, v (C sp H) is lowered by 117 cm −1 , indicating activation of the acetylenic CH bond; this feature is, however, not paralleled by a significant lengthening of the CH bond or bending back of the acetylenic hydrogen atom in the crystal structure.

Copper(I) complexes with conjugated dienes

Three copper(I) complexes containing conjugated dienes and one containing the acetylenic analogue of isoprene, 2-methyl-1-butene-3-yne (isopropenylacetylene), have been prepared and characterised by means of crystal-structure determination. Direct reaction between isoprene (2-methylbutadiene) and copper(I) trifluoromethylsulfonate, using triphenylphosphine as a stabilising ligand, results in [Cu-2(PPh3)(2)(mu-(H2C=CHC(CH3)=CH2))(O3SCF3)(2)] (1), whereas reaction between copper(I) chloride and isopropenylacetylene, dimethylbutadiene, and trans-1,3-pentadiene yields the labile compounds [Cu2Cl2 (mu-(H2C=CHC(CH3)=CH))] (2), [Cu2Cl2 (mu-(H2C=C(CH3)C(CH3)-CH2))] (3) and [Cu2Cl2(mu-(trans-H2C=CHCH=CH(CH3))] (4), respectively. All four compounds are polymeric. Thus, the organic ligands bridge two copper(I) centres via the alkene or alkyne bonds, the conjugated dienes all assuming the s-trans conformation. Further bridging is effected by the trifluoromethylsulfonate ligands in 1 and by the chloride ligands in 2, 3 and 4. In 1, copper(I) has distorted tetrahedral geometry, whereas in 2, 3 and 4, copper(I) exhibits tetrahedral or trigonal pyramidal geometry with the C=C/C=C linkage in the trigonal plane and an apical Cu-Cl bond. The nearly planar carbon skeleton of isoprene in 1 bonds to two copper(I) atoms from opposite faces of the diene. The Cu-C distances range from 2.085(6) to 2.220(6) Angstrom [C(CH3)] and the C=C bond lengths are 1.360(8) and 1.353(8) Angstrom. Trifluoromethylsulfonate ligands bridge adjacent [Cu-2(PPh3)(2)(mu-(H2C=CHC(CH3)-CH2))(O3SCF3)(2)] units leading to the formation of chains, containing internal chair-shaped Cu2S2O4 rings alternating with isoprene ligands, with peripheral triphenylphosphine ligands. The carbon skeleton of the isopropenylacetylene ligand in 2 and those of dimethylbutadiene in 3 and of trans-1,3-pentadiene in 4 are also approximately planar, but, unlike the situation in 1, in compounds 2-4, two copper(I) atoms are coordinated by C=C/C=C from the same face of the ligand. In 2, Cu-C distances range from 2.005(11) to 2.158(9) Angstrom [C(CH3)] and the C=C and C=C bond lengths are 1.373(13) and 1.200(14) Angstrom, respectively. In 3, Cu-C distances range from 2.06(1) to 2.17(1) Angstrom [C(CH3)] and both C=C bonds are 1.35(1) Angstrom. Dimeric [Cu2Cl2(mu-(H2C=CHC(CH3)=CH))](2) and [Cu2Cl2(mu-(H2C=C(CH3)C(CH3)=(CH2))] units are linked by long Cu-Cl bonds leading to the formation of chains with peripheral isopropenylacetylene (2) and dimethylbutadiene (3) ligands. The crystal structure of 4 could be determined only with low precision, but can be described in terms of copper(I) chloride layers with peripheral trans-1,3-pentadiene ligands. Shifts in the infrared absorptions on coordination of the conjugated dienes (including butadiene and cis-1,3-pentadiene) to copper(I) are discussed in the light of the crystal structures of 2-4.

Aurophilic association in endo-dicyclopentadienechlorogold(I)

The complex between endo-dicyclopentadiene and gold(I) chloride has been prepared by a substitution reaction in dichloromethane, whereby carbon monoxide in dissolved [AuCl(CO)] has been displaced by the endo-dicyclopentadiene ligand. This ligand is eta(2)-bonded to gold(I) via the C=C bond in the norbornene ring. Crystallographic studies show that the [AuCl(C10H12)] moiety undergoes aurophilic association to form a [(AuCl(C10H12))(2)] dimer, in which the Au-Au distance is 3.4282(8) Angstrom.

Pentamethylphenylcopper(I): a square-planar tetranuclear cluster

Abstract Pentamethylphenylcopper(I) has been prepared by the Grignard reaction between bromopentamethylbenzene and magnesium, with subsequent addition of copper(I) chloride; crystal structure determination shows the compound to be a tetranuclear cluster with a square-planar Cu4 core, in which the CuCu distance is 2.413(2) A. The compound crystallises as the THF solvate: [Cu4|C6(CH3)5|4]·4C4H8O in the tetragonal space group I4/mmm (No. 139) with a=17.837(2), c=8.888(3) A , V=2828(1) A 3 at −120° C and Z=2 ; full-matrix least-squares refinement yielded R=0.073 for 44 parameters and 576 observed reflections.

Tetrameric thienylcopper and pentanuclear thienylcuprate

The reaction between 2-bromothiophene and magnesium with subsequent addition of copper(I) chloride in tetrahydrofuran followed by dioxane yields thienylcopper, [Cu-4(C4H3S)(4)] (1). Without the addition of dioxane, magnesium thienylcuprate(I), [Mg(THF)(6)][Cu-5(C4H3S)(6)](2), (2) is formed. Both copper(I) complexes are oligomeric and are bridged by the thienyl ligands solely through carbon donors, thus lacking Cu-S bonds. The former compound, 1, is tetranuclear with a square-planar copper core and Cu-Cu distances of 2.453(3) and 2.507(3) Angstrom, and 2.464(2) and 2.489(2) Angstrom within the two crystallographically independent molecules, respectively; there is a weak (CuS)-S-... interaction of 3.118(5) Angstrom between these two molecules. The anion of 2 is a closo trigonal bipyramidal cluster of copper atoms in which the (ax)-(eq) edges are bridged by the thienyl ligands. Thus the Cu(ax)-Cu(eq) distances bridged by carbon are short, 2.497(5) and 2.503(5) Angstrom, indicative of three-centre Cu-C-Cu two-electron bonds, whereas the Cu(eq)Cu-...(eq) and Cu(ax)Cu-...(ax) distances are considerably longer at 3.135(7) and 3.423(8) Angstrom, respectively. The lack of participation of sulfur in bonding within the [Cu-5(C4H3S)(6)](-) cluster is discussed.

Products of the reaction between copper(I) phenoxide and triphenylphosphine

Abstract Two phenolatocopper(I) derivatives, viz.[Cu 4 (PPh 3 ) 4 (OPh) 4 ( 1 ) and [Cu 2 (PPh 3 ) 3 (OPh) 2 ] ( 2 ), where Ph = C 6 H 5 , have been prepared by the addition of triphenylphosphine to copper(I) phenoxide, obtained from mesitylcopper(I) and phenol. Characterisation by means of crystal structure determination showed 1 to be a tetramer with a cubane-type Cu 4 O 4 core in which CuO distances range from 2.05(2)–2.26(2) A. Complexes 2 is a μ 2 -phenoxide dimer in which one copper(I) centre is four-coordinated by two phenoxide and two triphenylphosphine ligands, while the other is coordinated by a single triphenylphosphine ligand and thus three-coordinated. Complex 1 crystallises as the solvate [Cu 4 (PPh 3 ) 4 (OPh) 4 ]·(C 6 H 5 CH 3 ) 2 in the monoclinic space group P 2 1 / c with a = 14.822(7), b = 23.160(4), c = 28.193(6) A , β = 98.64(2)°, V = 9569(5) A 3 at −90° C and Z = 4 ; full-matrix least-squares refinement yielded R = 0.082 for 529 parameters and 3931 observed reflections. [Cu 2 (PPh 3 ) 3 (OPh) 2 ] ( 2 ) crystallises in the triclinic space group P 1 with a = 13.948(4), b = 16.846(2), c = 12.480(3) A , α = 94.92(2), β = 110.45(2), γ = 95.96(2)°, V = 2709(2) A at −120° C and Z = 2 ; full-matrix least-squares refinement yielded R = 0.063 for 328 parameters and 2507 observed reflections. The effect of increasing the PPh 3 :CuOPh ratio on the stability of the phenoxide is discussed in terms of the coordination geometry and consequent accessibility of the metal to small molecules.

Copper(I)-induced activation of monosubstituted acetylenes. Perturbation of ligand geometry resulting from π-complexation

Abstract Three complexes between monosubstituted acetylenes, viz. phenylacetylene, propargyl chloride and propargyl alcohol, and copper(I) chloride have been prepared by direct reaction between copper(I) chloride and the relevant acetylenes. Changes in ligand geometry ensuing from π complexation to copper(I) have been investigated by infrared spectroscopy and crystal structure determinations. In all three compounds copper(I) exhibits trigonal pyramidal coordination geometry with a long apical CuCl bond, the trigonal plane being composed of the midpoint of π-acetylenic linkage and two chloride ligands. The CuC bond lengths are 1.999(4) and 2.066(3) A in [CuCl(HCCC6H5)] (1), 2.004(3) and 2.004(4) A in [CuCl(HCCCH2Cl)] (2) and 2.006(10) and 2.018(9) A in [CuCl(HCCCH2OH)] (3). The CC bond is lengthened only slightly on coordination, although ν(CC) is lowered by 133, 144 and 154 cm−1 for 1, 2 and 3, respectively, and there is moderate bending back of the HCC and RCC angles, indicating a relatively weak copper (I)alkyne interaction. ν(CspH) is lowered by 120, 83 and 110 cm−1, relative to the values for the free ligands, in 1–3, respectively. Although this suggests activation of the CspPH bonds, this is not supported by unusual structural features involving the acetylenic hydrogen atoms.

Synthesis and crystal structure of a polymeric complex between 1-penten-3-one and copper(1) chloride

Abstract Chloro[1-2-η-(1-penten-3-one)]copper(I) has been prepared by reaction between 1-penten-3-one and copper(I) chloride, and its structure determined by single-crystal X-ray diffraction at 170 K. [CuCl(C5H8O)], Mr = 183.1, crystallizes in space group P21/c with a 7.129(3), b 9.089(3), c 10.480(3) A, β 92.2(2)° and Z = 4. Full-matrix least-squares refinement of 105 structural parameters gave R = 0.036 for 1062 observed (I > 3σ(I)) reflections. In the complex between 1-penten-3-one and copper(I) chloride, copper(I) is four-coordinated, by two chloride ligands, the CC bond of one pentenone ligand and, via a long CuO bond of 2.606(6) A, by the carbonyl oxygen of another pentenone ligand. The structure can thus be described in terms of chloride-bridged dimers, which are joined, by pentenone bridges involving long CuO bonds, to form layers. The copper(I) coordination polyhedron is a trigonal pyramid in which the copper atom is displaced 0.134(2) A towards the apical oxygen atom from the plane through the two chloride ligands and the midpoint of the CC double bond. CuC distances are 2.048(6) and 2.060(6) A; CC is 1.383(8) A. The pentenone ligand is planar and has the s-cis conformation.