Elmer C. Alyea

Structural studies of steric effects in phosphine complexes. Part 4. Synthesis and crystal and molecular structure of trans-di-iodobis(tri-o-tolylphosphine)platinum(II)–dichloromethane (1/1)

The title complex has been synthesized and crystallizes in a 1 : 1 ratio with dichloromethane in the monoclinic space group C2/c with a= 22.100(3), b= 9.961 (3), c= 21.516(3)A, β= 113.19(1)°, and Z= 4. The structure has been solved by Patterson and Fourier methods and refined by full-matrix least-squares techniques to a final R of 0.036 for 3 073 observed reflections measured by diffractometer. The dichloromethane is disordered over three equally populated sites around the crystallographic two-fold axis. The trans-[Ptl2{P(C6H4Me-o)3}2] molecule resides on a crystallographic centre of symmetry with Pt–I and Pt–P distances of 2.622(1) and 2.348(2)A respectively. The failure of this complex to undergo intramolecular metallation can be explained by the steric effects of the P(C6H4Me-o)3 ligand, which are described by cone-angle calculations (θ= 183°) and a ‘ligand profile’.

Palladium(II) complexes derived from the potentially chelating ligands 2,2,NN-tetramethylpent-4-enylamine and 2,2-dimethylpent-4-enyl methyl sulphide. Crystal structures of dichloro[2,2-dimethylpent-(E)-3-enyl methyl sulphide]palladium(II) and chloro[1–3-η-syn-1-(1,1′-dimethyl-2′-methylthioethyl)allyl]palladium(II)

Reaction of PdX2·2PhCN(X = Cl or Br) with 2,2,NN-tetramethylpent-4-enylamine (1a) gives complexes (2) of stoicheiometry PdX2·(1a) in which Pd–X has added to the olefinic bond to generate a seven-membered chelate ring. In contrast, 2,2-dimethylpent-4-enyl methyl sulphide (1b) initally gives labile olefinic complexes, which readily rearrange to the derivatives (5a) and (5b) of 2,2-dimethylpent-(E)-3-enyl methyl sulphide (13). Variable-temperature 1H n.m.r. studies show that at low temperatures (5a) and (5b) exist in solution as pairs of epimers at sulphur, while heating leads first to equilibration of the epimers and then to labilisation of the metal–olefin bond. The π-allyl species (6a) and (6b) have been prepared from (5a) and (5b). X-Ray structures of (5a) and (6a) are reported. Crystals of (5a) are monoclinic, space group P21/n with Z= 4 in a unit cell of dimensions a= 8.365(2), b= 15.068(2), c= 9.595(1)A, and β= 94.00(1)°. Crystals of 6(a) are monoclinic, space group P21/c, with Z= 4 in a unit cell of dimensions a= 6.583, b= 12.462, c= 12.859(6)A, and β= 96.20(5)°. Both structures have been solved by the heavy-atom method and refined by full-matrix least-squares calculations to R= 0.023 for 2 414 reflections for (5a) and to R= 0.046 for 2 515 reflections for (6a). The five-membered chelate rings in (5a) and(6a) have C(2)-envelope conformations. In (5a) principal dimensions are Pd–Cl 2.313 and 2.320(1), Pd–S 2.269(1), and Pd–C 2.195 and 2.231(3)A, and the interplanar angle between the PdCl2S plane ad the Pd–ethylenic carbon plane is 96.0°. In (6a) dimensions are Pd–Cl 2.381(1), Pd–S 2.364(1), Pd–C 2.089, 2.120, and 2.173(5)A; the plane of the allyl moiety forms a dihedral angle of 116.4° with the PdSCIC(5) plane.

cis-Tetracarbonylbis(triphenyl phosphite)-molybdenum(0)

The coordination environment of the Mo atom in the title compound, [Mo(CO) 4 {P(C 6 H 5 O) 3 } 2 ], is pseudooctahedral, with principle dimensions Mo-P 2.442 (1), 2.443 (2), Mo-C(trans to P) 2.003 (6), 2.016 (6), Mo-C(trans to C) 2.032 (7), 2.042 (6) A, P-Mo-P 89.55 (5), trans-P-Mo-C 178.0 (2), 173.9 (2), trans-C-Mo-C 175.5 (2) o . The geometry about the P atom is distorted from tetrahedral, with larger Mo-P-O angles [mean 117.3 (2) o ] and smaller O-P-O angles [mean 100.5 (2) o ]. The short Mo-P bond distances indicate the strong π-acceptor ability of P(OPh) 3 , as also evidenced by the highly shielded δ( 95 Mo) value (-1754 p.p.m.)

Silver(I) complexes of the potentially chelating olefinic ligands 2,2-dimethylbut-3-enyl methyl sulphide and 2,2-dimethyl-2-silabut-3-enyl methyl sulphide. Crystal structure analysis of bis(2,2-dimethylbut-3-enyl methyl sulphide)silver(I) tetrafluoroborate, (2,2-dimethylbut-3-enyl methyl sulphide)silver(I) perchlorate, (2,2-dimethylbut-3-enyl methyl sulphide)nitratosilver(I), and (2,2-dimethylbut-3-enyl methyl sulphide)-trifluoroacetatosilver(I)

The ligands 2,2-dimethylbut-3-enyl methyl sulphide (1a) and 2,2-dimethyl-2-2-silabut-3-enyl methyl sulphide (1b) form analogous sets of complexes with a series of silver salts. Thus, 1 : 1 complexes have been obtained from Ag[BF4], Ag[ClO4], Ag[NO3], and Ag[O2CCF3], 1 : 2 (Ag : ligand) complexes from Ag[BF4] and Ag[ClO4], and 2 : 1 (Ag : ligand) complexes from Ag[NO3]. In the solid state (i.r. and X-ray) the ligands are chelated, while in solution (1H n.m.r.) both the Ag–sulphur and Ag–olefin bonds are labile even at low temperatures (–80 °C). Crystal-structure analyses have been completed on Ag[BF4]·2(1a), Ag[ClO4]·(1a), Ag[NO3]·(1a), and Ag[O2CCF3]·(1a). The complex Ag[BF4]·2(1a) contains discrete [Ag·2(1a)]+ cations (which have two-fold crystallographic symmetry) and disordered BF4– anions. Polymeric structures have been found for the remaining three complexes. In [Ag·(1a)][ClO4] polymeric cation chains are present, while the perchlorate ions are not co-ordinated to silver. In Ag[NO3]·(1a) the nitrato-group is bidentate (Ag–O 2.537 and 2.647 A), whereas the carboxyl group in Ag[O2CCF3]·(1a) is predominantly unidentate (Ag–O 2.29 and 2.99 A). In all four structures the five-membered –Ag–S–C(1)–C(2)–C(3)– ring adopts a C(2) envelope conformation. The olefin co-ordination is defined by the S–Ag–C(3)C(4) torsion angles 148.6 in Ag[BF4]·2(1a), 140.9 in Ag[ClO4]·(1a), 158.7 in Ag[NO3]·(1a) and 140.2° in Ag[O2CCF3]·(1a). Crystals of Ag[BF4]·2(1a) are monoclinic, space group C2/c, with four formula units in a cell of dimensions a= 10.838(2), b= 11.720(2), c= 16.355(2)A, β= 105.02(1)°, R= 0.049 for 645 observed reflections. Crystals of Ag[ClO4]·(1a) are orthorhombic, space group P212121, with four formula units in a cell of dimensions a= 8.229(3), b= 10.645(3), c= 13.917(3)A, R= 0.066 for 1 259 reflections. Crystals of Ag[NO3]·(1a) are monoclinic, space group P21/c, with four molecules in a cell of dimensions a= 11.049(1), b= 7.823(1), c= 14.352(3)A, β= 118.392(7)°, R= 0.049 for 1 653 reflections. Crystals of Ag[O2CCF3]·(1a) are monoclinic, space group P21/b, with four molecules in cell of dimensions a= 10.194(3), b= 15.784(5), c= 8.125(4)A, γ= 95.49°, R= 0.099 for 846 reflections.

Complexes of potentially chelating vinylsilanes and their carbon analogues with palladium(II) halides

Eight members of the series of 1 : 1 complexes of palladium(II) halides (chloride, bromide, and iodide) with the ligands 2,2,NN-tetramethylbut-3-enylamine (1a), 2,2-dimethylbut-3-enyl methyl sulphide (1b), and 2,2-dimethyl-2-silabut-3-enyl methyl sulphide (2b) have been isolated. The remaining complex, Pdl2·(2b), is unstable, disproportionating to give Pdl2·2(2b). Infrared and 1H n.m.r. data are reported. In solution all the 1 : 1 complexes, even the iodides, are chelated and the ring apparently adopts similar conformations. Variable-temperature 1H n.m.r. studies of two exchange processes, labilisation of the metal–olefin bond and, for the sulphur chelates, inversion at sulphur, are discussed.

Structural studies of steric effects in phosphine complexes. The crystal and molecular structure of dithiocyanato(tricyclohexylphosphine)mercury(II)

The title complex crystallizes in space group P21/c with unit-cell parameters a= 10.850(1), b= 9.825(2), c= 21.977(3)A, β= 94.34(1)°, and Z= 4. The structure has been refined anisotropically to R 0.030 and R′ 0.033 for 1 995 independent reflections. The mercury atom forms three normal covalent bonds [Hg–P 2.411(3), Hg–S 2.471(4)(terminal thiocyanato), and 2.553(3)A(bridging thiocyanato)] in a distorted trigonal-planar arrangement. A nitrogen atom from a neighbouring molecule is situated above the ‘trigonal plane’[Hg–N 2.516(10)A] and the mercury is effectively four-co-ordinate with a distorted trigonal-pyramidal configuration. The crystal structure thus contains infinite chains of mercury atoms linked by bridging thiocyanato-groups. The cone angle θ for the bulky tricyclohexylphosphine ligand is 177(3)°.

Synthesis, crystal, and molecular structure of paramagnetic tri-t-butylphosphonium tribromo(tri-t-butylphosphine)nickelate(II)

Reaction of tri-t-butylphosphine with nickel(II) bromide in alcoholic solution yielcs green [But3PH][(But3P)NiBr3]. Conductivity, magnetic-susceptibility, and electronic spectral measurements, and X-ray single-crystal analysis indicated the structure to be the same in solution as in the solid state. Crystals are monoclinic, space group Cc. with cell dimensions a= 24·069(3), b= 13·896(4), c= 18·739(2)A, β= 14891(1)°, Z= 4. The structure was solved by conventional heavy-atom methods and refined to R 0·088 for 1 839 observed reflexions. Structural data for the paramagnetic anion, which has nearly C3v symmetry (excluding the butyl groups), particularly reflect the bulkiness of the But3P ligand; mean dimensions: Br–Ni–Br 108·7°, P–C 2·02(10) and Ni–Br 2·38(2)A, and a Ni–P bond length of 2·48(1)A. The calculated Ni–PBut3 cone angle is 180 ± 2°. The P(2)–H bond of the cation lies near the pseudo C3 axis of the anion so that Ni⋯P(2) is 4·48 A, with P(2)⋯Br 4·27–4-31 A. These interion contacts indicate strong ion-pairing interaction in the solid-state structure.