H. van der Poel

Comparison of free and metal coordinated 1,4-disubstituted-1,4-diaza-1,3-butadienes : Crystal and molecular structures of 1,4-dicyclohexyl-1,4-diaza-1,3-butadiene and trans-[dichloro(triphenylphosphine)(1,4-di-tert-butyl- 1,4-diaza-1,3-butadiene)palladium(II)]

Abstract The crystal and molecular structures of c-Hex-DAB (c-hexyl-NC(H)C(H)N-c-hexyl; DAB = 1,4-diaza-1,3-butadiene) and of trans-[PdCl2(PPh3)(t-Bu-DAB)] are reported. Crystals of c-Hex-DAB are monoclinic with space group C2/c and cell constants: a = 24.70(1), b = 4.660(2), c = 12.268(3)A, β = 107.66(4)°, Z = 4. The molecule has a flat E-s-trans-E structure with bond lengths of 1.258(3)A for the CN double bond and 1.457(3)A for the central CC′ bond. These bond lengths and the NC-C′ angle of 120.8(2)° indicate that the C- and N-atoms are purely sp2-hybridized and that there is little or no conjugation within the central DAB skeleton. Crystals of trans-[PdCl2(PPh3)(t-Bu-DAB)] are triclinic with space group P-1 and cell constants: a = 17.122(3), b = 18.279(3), c = 10.008(5)A, α = 96.77(2), β = 95.29(3), γ = 109.79(2). Z = 4. The t-Bu-DAB ligand is coordinated to the metal via one lone pair only. In this 2e; σ-N coordination mode the E-s-trans-E conformation of the free DAB-ligand is still present and the bonding distances within the DAB-ligand are hardly affected. [CN: 1.261(10)A; CC′: 1.479(10)A (mean).] The PdN-, NC- and central CC′-bond lengths are compared with those found in other metal -R-DAB complexes.

Synthesis andmolecular geometry of [trans-PtCl2PBu3]2 (di-t-Bu-diimine) containing a s,s-N,N' bridging diimine with a planar anti-(trans-P-Pt-NCCN-Pt-P-trans)-skeleton

Abstract Complexes of the type [MCl 2 XR′ 3 ] 2 R-dim (M = Pd or Pt; XR′ 3 = arsine or phosphine) are formed in almost quantitative yield in the reactions of [MCl 2 XR′ 3 ] 2 with α-diimine ( 1 1 molar ratio Pt-dimer/R-dim). An X-ray study of [PtCl 2 PBu 3 ] 2 t-Bu-dim [Z = 2, a = 11.4540(11), b = 16.1169(7), c = 12.9202(12) A and β = 99.82(1); R = 5.9%] reveals a structure consisting of two planar trans-PtCl 2 P-units bridged by a planar NCCN skeleton in anti-configuration [CC 1.48(2), CN 1.27(3), NPt 2.214(10) A]. As a consequence of the orthogonal position of the platinum coordination plane and the NCCN plane the β-imine proton resides a short distance from the platinum atom (about 2.6 A). The structure in solution has been determined by 1 H, 13 C, 31 P and 195 Pt NMR spectroscopy. The observed spectra point to retention of the structural features in solution as evidenced by a large down field shift of the imine protons, e.g. 9.58 ppm and an AA′MM′ pattern in [PdCl 2 PEt 3 ] 2 t-Bu-dim. The present compounds are the first examples of complexes which contain a σ,σ′-N,N′ planar bridging diimine ligand as a general structural feature.

The thermochemistry of M(CO)6−xLx (M = Cr, Mo, W; L = piperidine, pyridine, pyrazine, pyrazole, thiazole; x = 1, 2, 3)

Abstract A number of M(CO) 6− x L x complexes (M = Cr, Mo, W; L = piperidine, pyridine, pyrazine, pyrazole, thiazole; x = 1, 2, 3) are shown to undergo both disproportionation and substitution in a CO atmosphere, when heated on a thermobalance. Using a DSC, reaction enthalpies have been determined from which enthalpies of formation were calculated. Combined with the sublimation enthalpies of these complexes, individual metal—ligand bond enthalpies were evaluated and discussed.

Synthesis and characterization of 1-imino-propane-2-one and iminobutan-3-one compounds RC(O)C(NR')R'

Abstract Metal catalyzed reduction of the carbonyl group in pyridyl-ketones as well as of the imine group in α-diimines have been subject of extensive study1–5. In contrast to the formation which at present is available concerning the complex formation of α-diimines with metals6–10, only little is known about the complex forming properties of the -C(O)C(NR)-system which is present in pyridylketones11–14.