V.G. Albano

The crystal and molecular structure of the potassium salt of the hexanuclear carbonyl cobaltate [Co6(CO)14]4−

Abstract The crystal and molecular structure of the potassium salt of the tetradecacarbonylkhexacobaltate tetraanion K 4 [Co 6 (CO) 14 ]·6 H 2 O has been determined by tridimensional X-ray data measured by counter methods. The structure has been refined by least squares of F down to an R factor of 0.06. The salt crystallizes in the monoclinic space group C 5 2 h = P 2 1 n with the following cell constants: a = 12.00(1) A, b = 10.04(1) A, c = 12.00(1) A, β = 90.0° (1), there are 2 formula units per cell. The structure is composed of a tetragonal body centered packing of anions with the cavities occupied by potassium ions and water molecules. The anion [Co 6 (CO) 14 ] 4− possesses an inversion center and contains an octahedral cluster of metal atoms surrounded by 14 CO groups; 6 of them are linearly bonded one for each cobalt atom and the other 8 CO groups are triply bridged on all the octahedral faces. The metal atoms cluster and its COs environment deviate from the holosymmetry OO h . When all the distortions are taken into account the anion can be assigned the symmetry S 6 . The CoCo mean distance is 2.50 A; the CoC and the CO distances are 1.70 A and 1.17 A for linearly bonded groups; for triply bridged groups the CoC distances are scattered in the range 1.89(1)–2.31(1) A, the CO mean distance is 2.21 A.

Stereochemistry of tetrahedral complexes of group VIII metals. Crystal and molecular structures of dinitrosylcarbonyltriphenylphosphineiron, Fe(NO)2(CO)(PPh3), and of dinitrosylbis(triphenylphosphine)iron, Fe(NO)2(PPh3)2

Single crystal X-ray structures of Fe(NO) 2 (CO)(PPh 3 ) (I) and of Fe(NO) 2 (PPh 3 ) 2 (II) have been determined. Compound (I) form triclinic crystals of space group P , with cell constants a 10.96(1)», b 10.20(1)», c 10.45(1)», α 115.84(8)°, β 117.33(8)°, γ 78.90(8)°, U 933.4» 3 , Z 2. Compound (II) forms monoclinic crystals of space group P 2/ c with cell constants a 11.70(1) », b 8.20(1) » c 17.24(2) », β 106.60(8)°, U 1584.6 » 3 , Z 2. Both cystals contain discrete molecules of distorted tetrahedral geometry. In compound (I) the CO and NO ligands are disordered; the principal bonding parameters are: FeC/N 1.709 », C/NO 1.148 », FeC/NO 177.9°, FeP 2.260(3) », C/NFeC/N 103.9° and PFeC/N 114.4°. In compound (II), which possesses C 2 symmetry, the principal bonding parameters are: N 1.650(7) », NO 1.19(1) », FeNO 178.2(7)° NFeN 123.8(4)°, FeP 2.267(2) », PFeP 111.9(1)°. These values are compared with those found in other tetrahedral complexes of Group VIII metals and discussed in terms of π metalligand interactions.

Synthesis and characterisation of [Rh7(CO)16X]2− anions (X = Br, I)

The reaction of Rh6(CO)16 with an excess of tetraalkylammonium halides in tetrahydrofuran gives the heptanuclear [Rh7(CO)16X]2− anions (X = Br, I), which have been isolated and characterised. The same anions were obtained by condensation of the Rh2(CO)4X2 carbonyl halides with the hexanuclear [Rh6(CO)15]2− anion, or by reaction of the [Rh7(CO)16]3− anion with iodine.

A new tetrahedral cluster of iridium containing two terminal hydrides. Synthesis and x-ray structure of dihydridodecacarbonyl-tetrahedro-tetrairidate(2-)

Abstract The synthesis of the novel hydridocarbonyl cluster anion [H 2 Ir 4 (CO) 10 ] −2 and its characterization by IR, NMR and X-ray analyses are reported. The structure of the anion is similar to that of M 4 (CO) 12 (M = Co, Rh) but with two terminal CO groups replaced by the hydrido ligands. In the metal atom tetrahedron the IrIr bonds trans to the H atoms are significantly longer than the others.

Synthesis and characterization of the tetranuclear anions [Rh4(CO)11(COOCH3)− and [Rh4(CO)11]2−

Abstract The orange [Rh 4 (CO) 11 (COOCH 3 )] − anion has been produced by reaction of sodium methoxide, or anhydrous sodium carbonate, with Rh 4 (CO) 12 in methanol. This anion reacts with potassium hydroxide to give the red [Rh 4 (CO) 11 ] 2− dianion, which can also be obtained directly from Rh 4 (CO) 12 and potassium hydroxide. Both these anions have been isolated as pure bis(triphenylphosphine)iminium salts. The carboalkoxy anion is very water sensitive, while the [Rh 4 (CO) 11 ] 2− dianion is air sensitive and reactive toward carbon monoxide. Both these anions react with Rh 4 (CO) 12 , to give [Rh 6 (CO) 5 (COOCH 3 )] − and [Rh 12 (CO) 30 ] 2− , respectively.

Synthesis and x-ray characterization of Rh4(CO)8 [P(OPh)3]4 and Rh6(CO)12[P(OPh)3]4

The structures of the compounds Rh 4 (CO) 8 [P(OPh) 3 ] 4 and Rh 6 (CO) 12 - [P(OPh) 3 ] 4 have been determined and shown to be derived from those of the parent species Rh 4 (CO) 12 and Rh 6 (CO) 16 by replacement of terminal carbonyl groups.

The crystal and molecular structure of hepta-μ-carbonyltetracarbonyl-tetrahedron-tetrarhodate(2—) in its bis(triphenylphosphine)iminium salt

Abstract The solid state structure of the cluster complex undecacarbonyltetrarhodate(2—) has been determined in the salt (PPh3NPPh3)2[Rh4(CO)11], which crystallizes in the space group P 1 with cell constants a 22.394(3), b 14.351(2), c 11.937(2) A, α 93.05(2)°, β 96.25(2)°, υ 88.38(2)°, Z = 2. The structure was refined by least-squares to a conventional discrepancy factor R of 0.060, based on 3884 reflection intensities collected by counter methods. The metal atom cluster is a distorted tetrahedron to which the ligands are bound four terminally and seven edge bridging; the idealized symmetry of the anion is C2[itv. The RhRh distances range from 2.662(2) to 2.986(2) A, and are discussed in terms of ligand topology and the localized character of the anionic charge.

The x-ray structure of trihydridobis(1,2-bisdiphenylphosphinoethane)rhenium(III), ReH3(DPPE)2

Abstract Trihydridobis(1,2-bisdiphenylphosphinoethane)rhenium(III), ReH 3 (DPPE) 2 crystallizes in the space group P 2/ c , Z = 2, with cell dimensions a = 16.09(2), b = 10.27(1), c = 19.11(2) A, β = 128.0(1) o . The datawere collected photographically and 656 non-zero reflections were used to solve the structure by the heavy atom method (R = 0.075). The Re(DPPE) 2 moiety has crystallographic C 2 symmetry and geometrical considerations together with potential energy computations allow to assign unequivocally the most favourable positions to the hydrido ligands. These occupy three equatorial positions of a slightly distorted pentagonal bipyramid. A compararative discussion of the structures of ReH 3 (DPPE) 2 and ReH 3 (PPh 3 ) 2 (DPPE) confirms the assignment of the hydrido ligand positions in both crystal species.

The crystal and molecular structure of dicarbonylbis(diphenylethylphosphine) platinum(0) Pt(CO)2[P(C6H5)2(C2H5)]2

Abstract The complex dicarbonylbis(diphenylethylphosphine)platinum, Pt(CO)2[P(C6H5)2(C2H5)]2, crystallizes in either of the enantiomorphous space groups P3121 (No. 152) and P3221 (No. 154) with cell dimensions a = 10.64(1), c = 22.06(1) A, U = 2163 A3; pc = 1.564 g/cm3 for Z = 3, pm = 1.55(3) g/cm3. The intensities of 1177 independent reflections have been determined by counter methods with MoKα monochromatized radiation. The structure has been solved by the heavy atom method. The refinement, carried out by full-matrix least squares down to a final R factor of 0.042, has enabled the absolute configuration of the crystal sample (space group P3121) to be ascertained. The molecule is roughly tetrahedral, and has the metal atom lying on a two-fold axis of the cell. Bond parameters are: PtC = 1.92(2) A, PtP = 2.360(4) A, CPtC = 117(1)° and PPtP = 97.9(2)°. The PtC2 and PtP2 moieties make a dihedral angle of 86.0(3)°. The overall C2 symmetry of the molecule is probably only a statistically averaged situation, a disorder in the PtCO interactions being apparent from the orientations of the thermal ellipsoids of the C and O atoms.

The crystal and molecular structure of the new cluster dianion μ-iodotetra-μ3-carbonyldi-μ-carbonyldecacarbonyl-polyhedro-heptarhodate(2—) in its tetraethylammonium salt

Abstract The tetraethylammonium salt of the cluster anion [Rh 7 (CO) 16 I] 2− crystallizes in the P 1 space group with cell constants a = 20.06(2), b = 11.08(1), c = 10.42(1) A, α = 83.14(8)°, β = 96.46(8)°, γ = 102.06(8)°, Z = 2. A set of 2532 diffraction intensities, collected by counter methods, was used for resolution and refinement of the structure. The metal atom cluster consists of a monocapped octahedron similar to that found in [Rh 7 (CO) 16 ] 3− . Ten of the CO ligands are coordinated terminally, two edge-bridging and four face-bridging; the iodine atom is in an edge-bridging position. Stereochemistry and bond parameters of this dianion are discussed in connection with the structure of the trianion [Rh 7 (CO) 16 ] 3− and the presence of an electron pair in a cluster antibonding orbital is demonstrated.