Lutz M. Engelhardt

Lewis-base Adducts of Group 1B Metal(I) Compounds. Part 16. Synthesis, structure and solid-state phosphorus-31 nuclear magnetic resonance spectra of some novel [Cu4X4L4] (X = halogen, L = N, P base) 'cubane' clusters

Recrystallization of [Cu4l4(PPh3)4] from toluene has yielded a new polymorph of that compound, (1), which has been shown by single-crystal X-ray diffraction analysis to have a tetrametallic ‘cubane’ structure rather than the expected ‘step’ structure. Crystals are monoclinic, space group P21/n, with a= 19.47(1), b= 26.94(1), c= 13.528(5)A, β= 98.98(4)°, Z= 4 tetramers; R was 0.06 for No= 3 681. Cu–I distances range from 2.653(3) to 2.732(3)A, with Cu ⋯ Cu 2.874(5)–3.164(4) and I ⋯ I 4.234(2)–4.496(3)A. All adducts of stoicheiometry [M4X4(PPh3)4](M = Cu or Ag; X = Cl, Br, or I) have now been synthesized and structurally characterized in a cubane configuration. Recrystallization of copper(I) chloride and bromide from triethylamine also yields tetrameric cubane 1 : 1 adducts [X = Cl (2) or Br (3)], as does the reaction of copper(I) chloride with the very bulky ligand 2-[bis(trimethylsilyl)methyl]pyridine, to give [Cu4Cl4(tmspy)4](4). These three complexes have also been crystallographically characterized, (2) and (4) being the first reported cubane type tetramers for the copper(I) chloride–nitrogen base system. Complexes (2) and (3) are isostructural with their triethylarsine and -phosphine counterparts, being cubic, space group I3m, with a= 12.162(5)A in (2) and 12.368(3)A in (3); Z= 2 tetramers. Cu–Cl,Br distances are 2.441(4) and 2.537(3)A respectively. For (4), the crystals are tetragonal, space group I41/a, with a= 18.620(4), c= 20.079(5)A, Z= 4 tetramers. Although the Cu4Cl4 cubane core of the molecule has crystallographically imposed symmetry, the geometry is very unsymmetrical as a consequence of the ligand bulk, with Cu–Cl 2.225(2)–2.636(2), Cu ⋯ Cu 2.960(2)–3.194(2), and Cl ⋯ Cl 3.838(3)–3.866(3)A. Residuals R for (2), (3), (4) were 0.040, 0.038, and 0.040 respectively for No= 136, 136, and 1 008 ‘observed’ reflections. The solid-state 31P n.m.r. spectra of the triphenylphosphine cubane clusters show significant differences to those with a ‘step’ geometry; these differences are related to the crystallographic environment of the phosphorus nuclei.

Lewis base adducts of Group 11 metal compounds. Part 24. Co-ordination of triphenylphosphine with silver nitrate. A solid-state cross-polarization magic angle spinning 31P nuclear magnetic resonance, crystal structure, and infrared spectroscopic study of Ag(PPh3)nNO3(n= 1–4)

Solid-state cross-polarization magic angle spinning 31P n.m.r. spectroscopy, single-crystal X-ray structure determination, and i.r. spectroscopy have been used to investigate the properties of the adducts of triphenylphosphine with silver(I) nitrate: Ag(PPh3)NO3, (1); Ag(PPh3)2NO3, (2); Ag(PPh3)3NO3, (3); and Ag(PPh3)4NO3, (4). The value of 1J(Ag–P) decreases with increasing co-ordination number: (1), 780; (2), 470; (3), 310; and (4),190 Hz, paralleling solution results. Single-crystal X-ray structure determinations of compounds (2)–(4) have been performed: (2), triclinic, space group P, a= 11.821(3), b= 11.990(3), c= 13.660(3)A, α= 102.05(2), β= 112.80(2), and γ= 105.30(2)°, yielding R= 0.036 for 4 090 ‘observed’ reflections; Ag–P 2.443(1) and 2.440(1)A, P–Ag–P 138.21(5)°(3), monoclinic, space group P21/n, a= 18.984(5), b= 13.710(3), c= 17.900(4)A, and β= 94.94(2)°, yielding R= 0.053 for 5126 reflections; Ag–P 2.630(2), 2.525(1), and 2.545(2)A, P–Ag–P 118.37(5),112.07(4), and 116.44(5)°; (4), trigonal, space group R, a= 19.07(2), and α= 43.77(5)°, yielding R= 0.060 for 1 903 observed reflections; Ag–P 2.643(3) and 2.671(4)A, P–Ag–P 109.49(12) and 109.45(10)°. Structures (2) and (3)[and (1)] are isomorphous with the analogous triphenylarsine compounds. In all cases the nitrate group is only weakly co-ordinated [and is ionic in (4)]: Ag–O 2.464(4) and 2.649(4) in (2), 2.684(6) and 2.775(6)A in (3). These weak interactions are reflected in the small splitting observed for the asymmetric N–O stretching vibrational mode compared to the analogous copper(I) compounds.

Lewis-base adducts of group 11 metal (I) compounds. XXVI: Solid-state cross-polarization magic-angle-spinning 31P n.m.r. and structural studies on 1:1 adducts of triphenylphosphine with gold (I) salts

Linear, two-coordinate compounds of molecular formula (PPh3) AuX have been characterized by solid-state and solution 31P n.m.r. spectroscopy, and single-crystal X-ray diffraction techniques. The solid state n.m.r. spectra reveal single, broad resonance lines for X = NO3 (chemical shift 19 ppm , ref. 85% H3PO4), CH3C02 (24 ppm), SCN (36ppm), CN (37 ppm ) and CH3 (47 ppm ) and doublets for X = Cl (27, 33 ppm ), Br (28, 36 ppm ) and I (34, 38 ppm ), the latter three spectra being recorded at 121.47 MHz and 161.96 MHz. Solution spectra show relatively sharp single resonances for each compound with 6 values generally slightly higher than in the solid state. Crystal data are reported for X = NO3, space gro )p P21/c, a 8 895(9), b 10.117(8), c 19.57(2) A; β 97.43(8)o, Au-P,O = 2.199(5), 2.02(1) A. Crystals of compounds with X = Br, I and SCN are isomorphous with the AuCl compound, belonging to space group 212121. For X = Br, a 12.479(5), b 13.45(1), c 10.0!2(8) A; Au-P, Br = 2.252(6), 2.407(2) A. For X = I, a 12.529(8), b 13.870(5), c 10.188(4) A; Au-P, I = 2.254(5), 2.556(2) A. For X = SCN, a 12.257(5), b 13.776(8), c 10.754(6) A; Au-P, S = 2.252(7), 2.304(7) A.

X-ray structure of a derivative of the “simplest metallocene: Cyclopentadienyllithium”, [Li{;η-C5H4(SiMe3)};{;NMe2(CH2)2NMe2};] (i.e., LiCp′(TMEDA))

Abstract Crystalline monomeric tetramethylethylenediamine(trimethylsilylcyclopentadienyl) lithium [LiCp′(TMEDA)] was prepared by addition of an equimolar mixture of n-butyllithium and TMEDA in n-hexane to trimethylsilylcyclopentadienene, and recrystallisation from n-pentane at −30°C. X-ray data show that the lithium atom may be regarded as trigonal planar, with bonds to (a) the two nitrogen atoms (2.142(8) and 2.119(10)A) of the chelating TMEDA and (b) the centroid of the planar η5-cyclopentadienyl ring (1.928A). The Li C bonds range from 2.257(10) to 2.286(10)A(the carbon bearing the SiMe3 substituent), and the cyclopentadienyl C C bonds from 1.38(1) (the two bonds furthest removed fromC SiMe3) to 1.421(8)A.

Organo-magnesium reagents: the crystal structures of [Mg(anthracene)(THF)3] and [Mg(triphenylmethyl)Br(OEt2)2]

Abstract [Mg(anthracene)(THF)3] (1), (THF = tetrahydrofuran), is monomeric in the solid state; the metal is bound to the C(9) and C(10) centres with r − (MgC) 2.30 A, and the [anthracene]2− ligand folded along the C(9)–C(10) vector with a mean angle of 28.6°. [Mg(CPh3)Br(OEt2)2] (4) is also monomeric; the metal centre is four-coordinate, bound only to the ipso-carbon of the carbanion, r(MgC) 2.225(1) A. Reaction of 1 or elemental magnesium with BrCPh3 in THF or addition of THF to 4, yields a red solid of the Grignard reagent containing some paramagnetic species.

The first monomeric crystalline tin(II) alkyls; X-ray structures of the β-N-functionalised alkyls Sn(R)X [= (SiMe3)2C5H4N–2 and = , C, or (SiMe3)2]

Monomeric 2-pyridylbis(trimethylsilyl)methyltin(II) compounds Sn(R)X [= (SiMe3)2C5H4N-2 and = (1), l (2), or (SiMe3)2(3)] were prepared from (LiR)2 and (a) SnCl2 or Sn(OC6H3But2-2,6)2(1), (b) 2SnCl2(2), or (c) Sn[N(SiMe3)2]2(3); their X-ray structures show that the ligands are invariably bonded to tin in a chelating fashion in the crystal with Sn–C and Sn–NC5H4 bond lengths of 2.35(2) and 2.42(2)(1), 2.32(2) and 2.27(3)(2), and 2.356(8) and 2.299(5)A(3), respectively, but in C6D5CD3 solution there appear to be (n.m.r.) C5H4N–Sn dissociative processes (ΔG‡ca. 43 ± 2 kJ mol–1).

Lewis-base adducts of group 11 metal(I) compounds. LIX. Crystal structure determinations of tetrakis(trimethylphosphine)copper(I) halides and tetrakis(triphenylphosphine)-copper(I) and -silver(I) hexafluorophosphates.

The crystal structures of [Cu(Pme3)4]X (X = Cl , Br, I) and of [M(PPh3)4] [PF6] (M = Cu, Ag) have been determined by single-crystal X-ray diffraction methods at 295 K. The former compounds contain nearly tetrahedral [Cu(PMe3)4]+ ions on sites of m symmetry with mean Cu-P bond lengths of 2.270, 2.271 and 2.278 Ǻ for X = Cl , Br and I respectively. The latter compounds contain [M(PPh3)4]+ ions on sites of 3 symmetry. In the M =Ag complex the coordination environment is close to tetrahedral, but in the M =Cu complex the length of the axial Cu-P bond [2.465(2)Ǻ] is significantly shorter than that of the off-axis bonds [2.566(2)Ǻ]. Possible reasons for this are discussed.

Lewis-Base Adducts of Group 11 Metal(I) Compounds. XLII : [Cu4X4L4] 'cubane' clusters, L = hindered N-base ligand: synthesis and structures of the L = 2-(diphenymethyl)pyridine complexes (X = Cl, Br, I)

The synthesis and single-crystal X-ray structure characterization of tetrameric cubane clusters of copper(1) halides with the hindered N-base ligand 2-(diphenylmethy1)pyridine are reported. The chloride, bromide and iodide structures are isomorphous , crystallizing in the tetragonal space group 141/a, a ≈ 23, c ≈ 12 A , Z = 4 tetramers, the tetramer having crystallographically imposed 4 symmetry, well removed from the ideal 43m. In terms of each X3CuN fragment of the core, this distortion results in one of the N-Cu-X angles being enlarged by c. 30o with respect to the other two and one Cu-X bond distance shortened. Cu-N is also shorter than is usual in a four-coordinate environment and the cluster can be envisaged as being constructed from four quasi-linear monomers. The distortions may be attributed to interaction between the 6- and 2-α-substituent-hydrogen atoms and the halide atoms of the core. The effect diminishes with increasing halide size and increasing volume of the Cu4X4 core.

Lewis-base adducts of group 1B metal(I) compounds. Part 13. Crystal structure determinations of tetrakis(triphenylphosphine)-copper(I) and -silver(I) perchlorates, bis(pyridine)bis(triphenyl-phosphine)copper(I) perchlorate, (2,2′-bipyridyl)bis(triphenyl-phosphine)copper(I) perchlorate, and tetrahydroboratobis-(triphenylphosphine)copper(I)–pyridine (1/0.5)

The crystal structures of [Cu(PPh3)4]ClO4(1) and [Ag(PPh3)4]ClO4(2) have been determined by single-crystal X-ray diffraction methods at 295 K, being refined by least-squares methods to residuals of 0.10 and 0.08 for 591 and 1 294 independent ‘observed’ reflections respectively. The two compounds are isomorphous (rhombohedral, space group R, and Z= 2) with a= 19.02(2)A, α= 44.06(6)° and a= 19.085(5)A, α= 43.90(1)° respectively; the cation lies on a site of 3 symmetry, while the anion is disordered about a site of symmetry. The metal-atom geometry is pseudo-tetrahedrai [Cu–P = 2.60(1), 2.52(1)A; Ag–P = 2.650(2)A, with all P–M–P angles lying between 109.3 and 109.7 °]. For the structure determination of [Cu(PPh3)2(py)2]ClO4(3) obtained by the recrystallization of [Cu(PPh3)4]ClO4 from pyridine (py), 2 843 ‘observed’ reflections were refined to a residual of 0.052. Crystals are triclinic, space group P, with a= 15.599(4), b= 13.413(4), c= 10.982(4)A, α= 79.51(3), β= 70.47(3), γ= 860.3(3)°, and Z= 2. Cu–P = 2.271(4), 2.295(3)A and Cu–N = 2.102(7), 2.115(8)A in a pseudo-tetrahedral copper(I) environment, with P–Cu–P = 115.85(9)° and N–Cu–N = 101.5(2)°. The 2,2′-bipyridyl (bipy) analogue [Cu(PPh3)2(bipy)]ClO4(4) is monoclinic, space group P21/c, with a= 10.210(3), b= 15.085(4), c= 28.455(9)A, β= 109.13(2)°, and Z= 4. Cu–P = 2.246(3), 2.256(3)A and Cu–N = 2.056(8), 2.113(9)A, with P–Cu–P = 125.4(1) and N–Cu–N = 79.6(4)°. R was 0.081 for 2 605 reflections. [Cu(BH4)(PPh3)2], by contrast, yields a hemipyridine solvate, (5), on recrystallization from pyridine; crystals are triclinic, space group P, with a= 12.849(6), b= 10.319(5), c= 13.618(6)A, α= 102.91(4), β= 101.91(4)γ= 73.42(4)°, and Z= 2. The structure was refined to a residual of 0.051 for 3 633 independent ‘observed’ reflections, and is isomorphous with the hemibenzene solvates of [CuX(PPh3)2](X = Cl or Br) and [AuCl(PPh3)2].

Lewis-base adducts of group 11 metal(I) compounds. LIII : Synthesis and structural characterization of binuclear µ,µ'-dichloro-, dibromo- and diiodo-bis[(pyridine)(triphenylphosphine)copper(I)] complexes, and their pyridine-4-carbonitrile analogues

Mixed base pyridine (py)/triphenylphosphine adducts of the copper(1) halides, CuX, have been synthesized for 1 : 1 : 1 stoichiometry for X = chloride and iodide; single-crystal X-ray structure determinations of these show them to be isomorphous and isostructural with that of the bromide recorded elsewhere, being µ,µ′- dihalo-bridged dimers , [(PPh3)( py )CuX2Cu( py )(PPh3)], monoclinic, C2/c, a ≈ 26.2, b ≈ 14.3, c ≈ 11 .2 A , β ≈ 95, Z = 4 dimers. The bromide has been isolated as a new monoclinic C 2/m polymorph, a 11 .279(8), b 14.268(6), c 13.858(4) A, β 109.33(6)o, Z=4 dimers, and details of its structure are also recorded. The structures of their pyridine-4-carbonitrile (pycn) analogues have also been determined and found to be also binuclear, with no cyano-copper interactions; these also are an isomorphous, isostructural series, monoclinic P21/n, a ≈ 15.4, b ≈ 8.1, c ≈ 17.9 A , β ≈ 101 o, Z = 2 dimers. In each series of dimers, one half of the dimer is crystallographically independent, the generators of the other half being twofold rotor (C2/c phase), mirror (C2/m phase) and inversion centre (P21/n phase) respectively.