C. H. Stam

INTRAMOLECULARLY CHELATED DI‐ AND TETRANUCLEAR ARYLLITHIUM COMPOUNDS: CRYSTAL STRUCTURE OF LI4(C6H4(2‐CH2NME2))4 CONTAINING 4‐CENTER 2‐ELECTRON‐BONDED C(ARYL) ATOMS AND HEPTACOORDINATE LITHIUM ATOMS

Die aquimolare Umsetzung von (I) mit BuLi liefert die Produkte (II), von denen (IIa) aus Ether/Hexan als Tetrameres kristallisiert.

s,s'-N,N' bridging and s,s-N,N chelating a-diimines. Molecular geometries of[PtCl2PBu3]2 (t-BuN=CHCH=NBu-t) and PtCl2 (styrene)(t-BuN=CHCH=NBu-t)

Abstract The capacity of cyclopentadienylsodium to form adducts with the following bases has been studied: diethyl ether, tetrahydrofuran, 1,2-dimethoxyethane, 1,4-dioxane, 1,3,5-trioxane, benzo-15-crown-5, triethylamine, tetramehtylethylenediamine, pyridine, 4-dimethylaminopyridine, and 2,2′ bipyridryl. Most form extremely air- and moisture-sensitive 1 : 1 adducts Na(C 5 H 5 )L, where L = Lewis base. Similar adducts, Na(C 5 H 4 Me)L, of methylcyclopentadienylsodium have been prepared. Their infrared and 1 H NMR spectra are consistent with η 5 -coordination of the cyclopentadienyl groups. In the crystal, the tetramehtylehtylenediamine adduct, Na(C 5 H 5 )TMEDA, adopts a puckered chain structure, with η 5 -C 5 H 5 rings bridging Na(TMEDA) units.

Synthesis and structure of pentacarbonyl(mesityldiphenylmethylenephosphine)-chromium(0)

Abstract Mesityldiphenylmethylenephosphine (I), a stable all-carbon substituted phosphaalkene, reacts with Cr(CO)5 · THF to furnish the title compound II, a relatively air-stable complex. Spectral data suggest a close structural similarity between the free and the complexed ligand and indicate I to be a ligand of moderate basicity towards chromium. X-ray crystal and molecular structure determination showed the phosphaalkene moiety to be nearly planar with a typically short PC bond length of 1.679(4) » and a CPC bond angle of 109.8(2)°. From a discussion of the bond lengths, it is tentatively concluded that in II, I is a π-acceptor of intermediate strength.

Cumulated double bond systems as ligands

Abstract Each of the compounds [MCl(Pr3)2(ArylNSO)] (M = RhI, IrI; R = i-Pr, Cy: Aryl = C6H5, 4-MeC6H4, 4-ClC6H4, 2,4,6-Me3C6H2 appears to exist as two isomers both in the solid state and in solution. The molecular and single crystal structure of one of the isomers of [RhCl(P-i-Pr)3)2(4-Me6H4NSO)] shows that the N-sulfinylaniline ligand is in the cis-configuration and coordinated to the rhodium atom via the sulfur-atom. The ligand lies in a plane which includes the rhodium atom and is in agreement with the Rh-S distance of 2.10 A. IR results of the compounds (solid and solutions), 21P NMR data and 15N NMR of a 15N labelled compound, which yielded a 103Rh15N coupling constant of 15.5 Hz, show that in the second isomer the N-sulfinylaniline ligand is probably bonded to the metal atom via the π-NS bond. The ratio of the metal-π-NS bonded isomer and the metal-S bonded isomer decreases in the order Aryl = 4-ClC6H4 > C6H5 > 4-MeC6H4; R = i-Pr > Cy and M = Rh > Ir. The interconversion of the two isomers is intramolecular and becomes observable on the 31P NMR time scale at about 40° C for M = Rh. In the case of [Ir(P-i-Pr3)2(4-MeC6H4NSO)], cyclometallation of the sul- finylaniline is observed via the ortho-carbon atom, whereas cyclometallation via P-i-Pr3 is observed when the ortho-positions are blocked by methyl groups, e.g. when L = 2,4,6-Me3C6H2NSO.

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.

Syntheses and structural aspects of rigid aryl- palladium(II) and -platinum(II) complexes. X-ray crystal structure of o,o′-bis[(dimethylamino)methyl]phenyl- platinum(II) bromide

Abstract The tridentate monoanionic ligand o,o ′-(Me 2 NCH 2 ) 2 C 6 H 3 (NCN′) has been used to synthesize novel aryl-palladium(II) and -platinum(II) complexes [PtR(NCN′)] and [MX(NCN′)] (M = Pt, Pd). Three synthetic procedures are described, namely: (i) reaction of the cationic complex [M(NCN′)(H 2 O)] + with KX or NaX to give [MX(NCN′)] (X = Cl, I, O 2 CH, NCS, NO 2 , NO 3 ); (ii) displacement reactions using AgX with [MBr(NCN′)] to give [MX(NCN′)] (X = CN, O 3 SCF 3 . O 2 CMe, O 2 CCF 3 ) and (iii) transmetallation reactions of [PtBr{C 6 H 3 (CH 2 NMe 2 ) 2 - o,o ′}] with organolithium to give [PtR{C 6 H 3 (CH 2 NMe 2 ) 2 - o,o ′}] (R = Ph, o -, m -, p -tolyl, CCPh, CC- p -tolyl). All complexes have been characterized by elemental analysis, and IR, 1 H and 13 C NMR spectroscopy. An X-ray diffraction study has shown that [PtBr{C 6 H 3 (CH 2 NMe 2 ) 2 - o,o ′}] ( 2 ) has a square-planar structure, in which the tridentate ligand is bonded via C( ipso ) (PtC 1.90(1) A), and two mutually trans -N donor atoms (PtN(1) 2.07(1), PtN(2) 2.09(1) A). The fourth site trans to C( ipso ) is occupied by bromine (PtBr 2.526(2) A). The two chelate rings (NPtC( ipso ) 82.9(5) and 81.5(5)°) are distinctly puckered, with the two NMe 2 groups on opposite sides of the aryl plane. The PtC bond in 2 is shorter than analogous bonds in other arylplatinum(II) complexes, as a result of (i) the rigid structure of the tridentate ligand and (ii) the presence of two hard N donor atoms trans to one another across the platinum centre.

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.

Cumulated double bond systems as ligands ☆: XI. Di- an tri-nuclear iron complexes resulting from the reaction of [Fe2(CO)9] with RNSNR (R = t-C4H9, 4-MeC6H4); crystal and molecular structure of (Fe2(CO)6{RNC(O)S}] [Fe3(CO)9(RNS)S] and [Fe3(CO)9(RN)S]

Abstract Reaction of RNSNR (R = t-C4H9, 4-MeC6H4) with (Fe2(CO)9[leads to the rupture of one or two NS double bonds as evidenced by the formation of a number of complexes containing RNS, RN and S fragments. In the case of R = t-C4H9 and 4-MeC6H4 the RNS fragment behaves as a four-electron donor ligand, with the NS bond still double, and as a six-electron donor ligand with the NS bond single, bridging two iron atoms in [Fe2(CO)7(RNS)] and [Fe2(CO)6(RNS)], respectively. Insertion of CO into the NS bond of [Fe2(CO)6(RNS)] yields [Fe2(CO)6{RNC(O)S}]; a crystal structure determination has been carried out for the product with R = 4-MeC6H4. Heating of the solid complex affords azotoluene, which is also isolated from the reaction mixtures. In the case of R = t-C4H9[Fe2(CO)6S2], [Fe3(CO)9S2] and [Fe3(CO)9(RNS)S] are also formed. A crystal structure determination of the last compound reveals a prismane type structure, in which both a six-electron donor RNS fragment and a four-electron donor S atom are linked to the three iron atoms. For R = 4-MeC4H4 a different trinuclear iron complex [Fe3(CO)9(RN)S] was isolated, and the structure was established by a crystal structure determination; a nitrene fragment (RN) as well as a S atom are both triply bridging to a non linear array of three iron atoms of the Fe3(CO)9 skeleton.

Oxidative-addition reactions of molecular diiodine and dibromine to divalent organotin compounds. Crystal structures of bis(8-( dimethylamino)-1-naphthyl)tin( IV) dibromide and { 2,6-(bis( dimethylamino)methyl)phenyl} - (4-tolyl) tin( IV) diodide

Abstract The reactions of bis[8-(dimethylamino)-1-naphthyl]tin(II) with dibromine or diiodine afford bis[8-(dimethylamino)-1-naphthyl]tin(IV) dibromide ( 1 ) and bis[8-(dimethylamino)-1-naphthyl]tin(IV) diiodide ( 2 ), respectively. Reaction of {2,6-[bis(dimethylamino)methyl]phenyl}(4-tolyl)tin(II) with diiodine gives {2,6-[bis(dimethylamino)Methyphenyl}(4-tolyl)tin(IV) diiodide ( 3 ) in quantitative yield. The crystal structures of 1 and 3 have been determined by X-ray diffraction methods. As a result of intramolecular coordination of the nitrogen atoms with the tin centers, the geometry about tin in both 1 and 3 is octahedral, while the carbon atoms bound to tin are in trans position. In 1 the two bromine atoms are cis to one another, as are the two nitrogen atoms, whereas in 3 the two iodine atoms, like the two nitrogen atoms, are trans to one another. 1 H, 13 C and 119 Sn solution NMR spectroscopic studies of 1–3 show that they retain the structures found in the solid state.

Structural and spectroscopic properties of [(CO)5MM′ (CO)3(R-DAB)] (M,M′=Mn,Re; R-DAB=1,4-diaza-1,3-butadiene complexes. X-ray structure of [(CO)5ReMn(CO)3-(i-Pr-DAB)] and infrared and resonance Raman spectra of [(CO)5MM′(CO)3(R-DAB)]

Abstract The X-ray structure of the title compound has been determined by the heavy-atom method and refined by means of block-diagonal least-squares calculations from 2116 independent reflections. The crystals are monoclinic, space group P 2 Vc with unit cell dimensions a = 18.494(3), b = 7.502(2), c = 16.52(2) A, β = 113.760(6)° and Z = 4. The final R value was 0.037. The complex has an octahedral geometry and the CO ligands of the Re(CO) 3 and Mn(CO) 3 (i-Pr-DAB) moieties are in staggered positions. The Mn-Re bond length is 3.012(2) A and the MnN bond lengths are 1.994(9) and 2.003(9) A. The infrared and resonance Raman (RR) spectra obtained by excitation into the lowest electronic absorption band, are reported. A tentative assignment for the CO-stretching vibrations is presented based on their solvent and temperature dependence. The RR spectra of (CO) 3 MM′(CO) 3 (i-Pr-DAB) (M,M′=Mn, Re) taken from N 2 -matrices at 10 K are very weak, which means that the equilibrium conformation of these complexes hardly changes upon going from the ground state to the excited state. These RR spectra are discussed considering the electronic structure of these complexes.