ExperimentalGeneral Remarks. All manipulations were performed in air, except where otherwise noted. The solvents thf and hexane (analytical grade) were freshly distilled from sodium/potassium alloy, dichloromethane was distilled from calcium hydride, the other solvents (acetonitrile, diethylether, acetone) were used as purchased. Deuterated solvents for NMR measurements were distilled from the appropriate drying agents under N 2 immediately prior to use following standard literature methods. 15 Air-sensitive compounds were stored and weighed in a glovebox. The reagents 1,2-dibromoethane, 1,3dibromopropane, 1,4-diiodobutane, 2,6-dimethylaniline, 2,4,6-trimethylaniline, 2,6-diisopropylaniline, triethylorthoformate, sodium tetrafluoroborate, and potassium bis(trimethylsilyl)amide were used as received. 1 H and 13 C NMR spectra were obtained on Bruker Avance AMX 400, 500 or Jeol Eclipse 300 spectrometers. The chemical shifts are given as dimensionless values and are frequency referenced relative to TMS. Coupling constants J are given in hertz (Hz) as positive values regardless of their real individual signs. Abbreviations used: st = septet, br = broad. Mass spectra (MS) and high-resolution mass spectra (HRMS) were obtained in positive electrospray (ES) mode unless otherwise reported, on a Waters Q-TOF micromass spectrometer. 1,3-Bis-(2,4,6-trimethylphenyl)-4,5,6,7-tetrahydro-3H-[1,3]diazepin-1-ium iodide, 7-Mes•HI. The reaction was performed on a 71.0 mmol scale of amidine (19.90 g), 5.00 g of K 2 CO 3 (36.0 mmol) and 22.00 g of 1,4-diiodobutane (71.0 mmol) in 1 L of acetonitrile. The solution was heated under reflux for 5 hours to yield 29.20 g (63.0 mmol, 89%) of white, crystalline material. 1,3-Bis-(2,6-dimethylphenyl)-4,5,6,7-tetrahydro-3H-[1,3]diazepin-1-ium iodide, 7-Xyl•HI. The reaction was performed on a 43.3 mmol scale of amidine (10.93 g), 5.8 mL of 1,4-diiodobutane (13.63 g, 44 mmol), 3.01 g of K 2 CO 3 (22.5 mmol) in 0.5 L of acetonitrile. The solution was heated under reflux for 5 hours to yield 14.85 g (34.2 mmol, 79%) of white, crystalline material. 1,3-Bis-(2,6-diisopropylphenyl)-4,5,6,7-tetrahydro-3H-[1,3]diazepin-1-ium iodide, 7-Pr i •HI. The reaction was performed on a 11.0 mmol scale of amidine (4.00 g), 0.78 g of K 2 CO 3 (5.6 mmol), 1.6 mL of 1,4-diiodobutane (3.76 g, 12.1 mmol) in 400 mL of acetonitrile. The solution was heated under reflux for 17 hours to yield 3.87 g (7.1 mmol, 64%) of white, crystalline material. 2,4-Bis-(2,4,6-trimethylphenyl)-4,5-dihydro-1H-benzo[e][1,3]diazepin-2-ium bromide, Xyl7-Mes•HBr. The reaction was performed on a 35.8 mmol scale of amidine (10.03 g), 36.0 mmol of , 'dibromo-o-xylene (9.49 g), 2.49 g of K 2 CO 3 (18.0 mmol) in 0.5 L of acetonitrile. The solution was heated under reflux for 5 hours to yield 12.42 g (26.2 mmol, 73%) of white, crystalline material. 1 H

The synthesis of the novel seven-membered N-heterocyclic carbene (NHC) 1,3-dicyclohexyl-1,3diazepan-2-ylidene (3) and its 5,6-dioxolane derivative 4 is reported and their coordination chemistry with Rh(I), Ir(I), and Pt(0) discussed. The M(cod)(3)Cl, where M ) Rh and Ir, complexes display a high rotation barrier at room temperature about the M-C NHC bond, whereas for the M(CO) 2 ( 3)Cl and Pt-(nbe) 2 (3) complexes rapid rotation of the carbene ligand is observed at ambient temperature. The infrared ν(CO) values of the Rh(I) and Ir(I) derivatives M(CO) 2 (3)Cl give a measure of the donor ability of the new carbene ligands. The crystal structures of the amidinium salts 3‚HPF 6 and 4‚HPF 6 together with those of M(cod)(3)Cl [M ) Rh, Ir], Ir(cod)(4)Br, Ir(CO) 2 (3)Cl, and Pt(nbe) 2 (3) are reported. Both the salts and the coordinated carbene ligands exhibit extremely large NCN angles; for the complexes the angles are in the range 115.5(3)°[Pt(3)] to 122(11)°[Ir(4)].

The synthesis of new functionalised 6- and 7-membered NHC (N-heterocyclic carbene) precursors bearing anisidyl or pyridine N-substituents, both symmetrically and non-symmetrically substituted is reported. Their corresponding rhodium(i) and iridium(i) complexes, M(COD)(NHC)Cl, were also prepared and characterised. The unusual Rh(iii)/Rh(i) salt, [Rh(eta(2)-NHC-py)(2)Cl(2)][Rh(COD)Cl(2)], was obtained with one of the pyridyl-functionalised NHC ligands. Single-crystal X-ray analyses have been obtained for the majority of the complexes and NHC salts. The activity of these complexes was tested in the hydrogenation of a range of substrates with molecular hydrogen, including 1-cyclooctadiene and 2-methyl styrene, where they show enhanced activity and stability in comparison to non-functionalised NHC analogues, operating under exceptionally mild conditions (ambient temperature and atmospheric pressure).

Transition-metal complexes of the 1,3-butadiene ligand and its various substituted derivatives display very interesting features with respect to structure and bonding as well as reactivity. In its complexes, the s-cis-1,3-butadiene ligand has been observed to adopt a range of intergraded bonding modes between the η 4 -diene (A) and σ 2 ,π-metallacyclopentene (B) extremes. 1 These two structures are related by an oxidative addition operation in which the diene in structure B is effectively doubly reduced to a but-2-ene-1,4-diyl dianion. The relative importance of the diene or metallacyclopentene character depends on several factors, especially the reducing power of the low-valent metal fragment. Reactivity corresponding to this σ 2 ,π-metallacyclopentene character includes the insertion of unsaturated substrates into the metal-methylene bond 2 and the attack of Lewis acids such as B(C 6 F 5 ) 3 on the diene methylene carbon to yield zwitterionic metal allyl species (which can act as single-component olefin polymerization catalysts). 3 Reactivity associated with η 4 -diene character includes the displacement of the neutral diene ligand by various reagents, which can then undergo oxidative addition or oxidative coupling reactions on the resultant low-valent transition-metal species. 2c,d Many transition-metal diene complexes with intermediate bonding modes show both types of reactivity behavior, depending on the type of reagent used. In contrast, only very few 1,3-diene complexes of the group 3 and lanthanide metals are known. These are practically limited to 1,4-diphenyl-1,3-butadiene derivatives, in which the ligand predominantly has dianionic character and of which little reactivity has been reported. 4 In addition, several naphthalene-lanthanide complexes show structural features consistent with 1,3-diene character. 5 The group 3 metal scandium has a strong preference for the trivalent oxidation state, although some compounds with the metal in the monovalent oxidation state are known, e.g., in solid ScCl. 6 Recently a Sc I Br unit sandwiched between two ( -diketiminato)MgBr fragments was reported by Roesky et al. 7 We are exploring the chemistry of Sc diene complexes to see whether "lowvalent" behavior for Sc may be induced by the presence of a diene ligand. Here we describe the synthesis and characterization of the first 1,3-butadiene complex of scandium, [η 5 ,η 1 -C 5 H 4 (CH 2 ) 2 NMe 2 ]Sc(2,3-dimethyl-1,3-butadiene), with some aspects of its reactivity. It is shown that this compound can behave as a source of the reactive [η 5 ,η 1 -C 5 H 4 (CH 2 ) 2 NMe 2 ]Sc I fragment.The colorless cyclopentadienylamine scandium dichloride {[C 5 H 4 (CH 2 ) 2 NMe 2 ]ScCl 2 } x (1) was obtained in 80% yield from the reaction of the corresponding lithium cyclopentadienide with ScCl 3 (THF) 3 , followed by vacuum sublimation. 8 Reaction of the dichloride 1 with (2,3-dimethyl-1,3-butadiene)Mg‚(THF) 2 in ether, followed by workup at or below 0°C, afforded the complex [C 5 H 4 -(CH 2 ) 2 NMe 2 ]Sc(C 6 H 10 ) (2) as red crysta...

The stereoselective synthesis of a family of cis-macrocyclic diphosphines was achieved in only three steps from white phosphorus and commercial materials. These new ligands showed activity in the nickel-catalyzed coupling of CO2 and ethylene.

The performances of a number of RhI and IrI complexes of type [M(NHC)(COD)Cl] in the transfer hydrogenation of ketones were tested under a variety of reaction conditions, and with a variety of substrates, allowing comparison of Rh‐ and Ir‐NHC complexes, and also comparison of the influence of the NHC ligand on catalytic performance. Notably, of the RhI and IrI complexes with symmetrically substituted NHCs only those bearing cyclohexyl substituents were active, with RhI complexes of saturated 5‐, 6‐ and 7‐NHCs with N‐Mes substituents, [Rh(5,6,7‐Mes)(COD)Cl], showing no activity in transfer hydrogenation under the test conditions. RhI and IrI complexes of unsymmetrical o‐methoxyphenyl donor‐functionalised NHCs (df‐NHC) with differing carbene ring sizes were also tested in transfer hydrogenations, with the RhI complexes displaying no catalytic activity. However, the corresponding df‐NHC IrI complexes were found to be extremely effective catalysts. Catalyst tests also demonstrated the excellent stability of these complexes.

The rhodium complexes [Rh(NHC)(COD)Cl] and cis-[Rh(NHC)(CO) 2 Cl] of seven-membered N-heterocyclic carbenes (NHC) bearing aromatic N-substituents (mesityl, xylyl and o-tolyl) were synthesised, and a comparison of their steric and electronic properties with those of the analogous fiveand six-membered NHC complexes was made on the basis

. (2004). Neutral and cationic vanadium(III) alkyl and allyl complexes with a cyclopentadienyl-amine ancillary ligand. Organometallics, 23(16), 3914-3920. DOI: 10.1021/om049660t Copyright Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. The crystal, a parallelepiped of approximate size 0.250 x 0.250 x 0.150 mm., used for characterization and data collection was glued on top of a glass fiber by using inert- The positional and anisotropic displacement parameters for the non-hydrogen atoms and isotropic displacement parameters for hydrogen atoms were refined on F 2 with full-matrix least-squares procedures minimizing the function] / 3, F 0 and F c are the observed and calculated structure factor amplitudes, respectively; a (=0.0581) and b (= 0.2038) were refined.Crystal data and numerical details on data collection and refinement are given in Table 1. Final fractional atomic coordinates, equivalent displacement parameters and anisotropic displacement parameters for the non-hydrogen atoms are given in Table 2. Molecular geometry data are collected in c. Refinement. Number of reflections 3502Number of refined parameters 246Final agreement factors:1/2 0.0942Weighting scheme: a, b 0.0581, 0.2038 (4) -0.0883(2) 0.3461(2) 0.21674 (18) 0.0232(7) C (5) -0.1139(2) 0.4033(2) 0.30637(19) 0.0215(7) C (6) -0.2367(3) 0.3918(2) 0.3564(2) 0.0287(8) C (7) -0.2176(2) 0.2958(2) 0.4358(2) 0.0224(7) C (8) Standard deviations in the last decimal place are given in parentheses. Interatomic Distances (Å)V -Cl(1)2.3719(7) P -C(12)1.813(3) V -Cl(2)2.3947(7) N -C(7)1.478(3) V -P 2.5145(8)Bond Angles (deg.)