David M. Grove

The copper catalysed reaction of sodium methoxide with aryl bromides. A mechanistic study leading to a facile synthesis of anisole derivatives

Abstract The copper catalysed reaction of unactivated aryl bromides with sodium methoxide has been investigated by studying a number of parameters (copper catalyst, cosolvent, concentration and relative ratio of the reactants, additives and aryl bromide substituents) which influence this reaction. The ipso-substitution reaction was found to proceed via an intimate electron transfer mechanism involving a cuprate-like intermediate, Na[Cu(OMe)2]. A convenient synthesis of methyl aryl ethers from aryl bromides and concentrated sodium methoxide solutions in dimethyl formamide and methanol is presented. Also an attempt to extend this reaction to the use of chlorine derivatives was made.

CHIRAL ARENETHIOLATOCOPPER(I) CATALYZED SUBSTITUTION REACTIONS OF ACYCLIC ALLYLIC SUBSTRATES WITH GRIGNARD REAGENTS

Abstract Asymmetric induction can be achieved in the γ-selective substitution reaction of allylic substrates (R′CHCHCH 2 Y) with n -BuMgI catalyzed by the chiral arenethiolatocopper(I) complex 1b . It was found that the enantiomeric excess of the γ-substituted product (R′CH( n -Bu)CHCH 2 ) is influenced by the coordinating ability of the leaving group Y, and e.e.s of up to 42% (R′ = Cy, Y = OAc) have been obtained.

Arenethiolatocopper(I) complexes as homogeneous catalysts for Michael addition reactions

Arenethiolatocopper(I) complexes are shown to be efficient homogeneous catalysts in Michael addition reactions of several Grignard reagents to acyclic enones; the addition products are formed with excellent chemoselectivity (>99%) and good enantioselectivity (76% e.e.).

Design of novel Hexametallic Cartwheel Molecules From Persubstituted Benzene Compounds

The cartwheel complexes A are novel, nano-sized hexametallic species available from persubstituted benzenes C(6)[3,5-(CH(2)Y)(2)C(6)H(3)] (Y=NMe(2), P(O)Ph(2), PPh(2), SPh). The molecular structure of A (Y=SPh, ML(n)=PdCl) shows C(3) symmetry with adjacent radial Pd-Pd separations of 7.339(2) and 8.006(2) Å and a diametrically opposed Pd-Pd separation of 15.340(2) Å. Because of their size hexametallic species such as A are potential homogeneous catalysts in organic reactions which can be recovered by nanomembrane filtration techniques.

The Effect of the Trimethylsilyl Group on Electrophilic Cyclopalladation; A Study of Caryl–Si versus Caryl–H Selective Bond Activation with 2,6‐(Me2NCH2)2C6H3R (R=H or SiMe3)

The site selectivity of electro- philic palladation has been studied by using two bis(aminomethyl)-substituted benzenes 1,3-(Me2NCH2)2C6H4 (6) and 2,6-(Me2NCH2)2C6H3(SiMe3 )( 7) and Li2(PdCl4) or Pd(OAc)2 in solution in MeOH or CH2Cl2. The major product of direct palladation of 6 in both solvents is the polymeric cyclopalladated organo- metallic complex (1,5-{PdCl}2-2,4-(Me2- NCH2)2C6H2)n, which was characterized as its dinuclear pyridine derivative (1,5- {PdCl(C5H5N)}2-2,4-(Me2NCH2)2C6H2) (9). The effect of the trimethylsilyl group present at the 1-position in 7 leads to inversion of the site selectivity in comparison to that observed for 6, and to activation of the C - Si bond when MeOH is used as solvent; the major product of this direct palladation is the known monomeric cyclopalladated complex ({PdCl}2,6-(Me2NCH2)2C6H3) (8). However, using CH2Cl2 instead of MeOH in the palladation reaction of 7 leads to the major product arising from C - H rather than C - Si bond activation.

The Use of Ortho-chelating Arenethiolate Non-transferable Groups in the Copper(I) Catalyzed Selective α or γ Substitution of Acyclic Allylic Substrates with Grignard Reagents

Abstract Ortho-amino arenethiolatocopper(I) compounds are excellent catalysts for the cross-coupling reaction of Grignard reagents with acyclic allylic substrates. For example, reaction of n -BuMgI with geranyl acetate in Et 2 O at 0 °C yields quantitatively the γ substitution product, whereas the same reaction in THF at −30 °C affords selectively the α substitution product.

The homogeneously catalysed addition reaction of polyhalogenoalkanes to olefins by divalent arylnickel complexes: comparative reactivity and some important mechanistic leads

Abstract In comparative studies some bis( ortho -chelated) arylnickel compounds of the type [Ni{C 6 H 3 (CH 2 NRR′) 2 -2,6}X] have been tested for activity in the Kharasch addition reaction of polyhalogenoalkanes to an alkene double bond using methyl methacrylate as substrate and carbon tetrachloride as reagent. The N-donor substituent combination R = R′ = Me produces a complex with higher reactivity than either of the combination Et,Et, and Me,i-Pr, and the influence of the halide X is small; catalytic efficacy decreases in the order I ≈ Br > Cl (R = R′ = Me). The related palladium and platinum complexes [M{C 6 H 3 (CH 2 NMe 2 ) 2 -2,6}X] (M = Pt, X = I; M = Pd, X = Br) show no catalytic activity in this reaction, though the complex [Pd{C 6 H 3 (CH 2 NMePh) 2 -2,6}Br] does initiate alkene polymerization. A mechanism consistent with these results is outlined.

Syntheses and characterization of dinuclear palladium and platinum complexes with a single unsupported bridging group. Crystal structure of [{C6H3(CH2NMe2)2-o,o′}Pd(µ-Cl)Pd{C6H3(CH2NMe2)2-o,o′}]BF4

Reaction of cationic [M{C6H3(CH2NMe2)2-o,o′}(H2O)n]Y (M = Pd or Pt; n= 1, Y = BF4; M = Pt, n= 0, Y = O3SCF3) with neutral [MX{C6H3(CH2NMe2)2-o,o′}](M = Pd or Pt; X = halide or CN) gives novel homo- and hetero-dinuclear complexes possessing a single unsupported halide or cyanide bridge. The complexes have been characterized by i.r., 1H n.m.r., and elemental analyses. A single-crystal X-ray structure determination has been carried out on the palladium species [{C6H3(CH2NMe2)2-o,o′Pd(µ-Cl)Pd{C6H3(CH2NMe2)2-o,o′}] BF4[a= 11.163(1), b= 21.347(2), c= 12.246(4)A, β= 91.48(2)°, and Z= 4; R= 0.042 for 5 077 reflections]. The cation consists of two Pd{C6H3(CH2NMe2)2-o,o′} units sharing a single bridging chlorine atom. Both PdII centres have a slightly distorted square-planar co-ordination sphere. Each Pd atom is surrounded by a carbon atom and two mutually trans N atoms of the terdentate ligand and the bridging chlorine atom. Dihydride-bridged complexes [(C6H3(CH2NMe2)2-o,o′}M(µ-H)2Pt(PPh3)2]BF4(M = Pd or Pt) have been prepared by using a procedure in which a reactive hydride is generated in situ from the reaction of a Pt0 phosphine species and gaseous H2 in the presence of [M(C6H3(CH2NMe2)2-o,o′}]BF4(M = Pd or Pt). From 1H n.m.r. these complexes are anticipated to have a geometry in which there is both a four- and a five-co-ordinate centre. The reaction of [Pt{C6H3(CH2NMe2)2-o,o′}]O3SCF3 and [Pt(O2CH){C6H3(CH2NMe2)2-o,o′}] in benzene afforded the monohydride-bridged complex [{C6H3(CH2NMe2)2-o,o′}Pt(µ-H)Pt{C6H3(CH2NMe2)2-o,o′}]O3SCF3. Attempts to synthesize the palladium analogue were not successful.

A novel enantiopure proline-based organonickel(III) halide monocation with a pentadentate C, N2, O2-bonded bis(ortho-chelating) aryldiamine ligand☆

Abstract An attempt was made to use the enantiopure arylnickel(II) complex [Ni(L ★ − N , C , N )Br], 1 , (L ★ is the monoani ligand, 2,6-bis[(2-( S )-2-isopropoxycarbonyl-1-pyrrolidinyl)methyl)phenyl) as a catalyst for the Kharasch addition reaction of CCl 4 to alkenes which led instead to a new ionic arylnickel(III) complex [Ni(L ★ )Cl] 2 [NiCl 4 ] (=[ 2-Cl ] 2 [NiCl 4 ]. An X-ray diffracti study of this complex revealed the presence of two identical monocations [ 2-Cl ] + that have octahedrally coordinated Ni(III) centres and a single dianionic NiCl 4 2− unit. The octahedral ligand sphere of cation [ 2-Cl ] + is best described as tetragonally compressed, with the meridional coordination comprising N 2 , O 2 donative bonding from the two N atoms of the pyrollidine groups and two carbonyl O atoms of the ester groups of L ★ , the mutually trans apical sites are occupied by a Cl atom and the C atom of the NiC aryl bond; i.e. the monoanionic organic ligand L ★ binds as a monoanionic C, N 2 , O 2 pentadentate system. Spectroscopic data for [ 2-Cl ] + are presented and compared with those for the square-planar arylnickel(II) complex 1 , in which the oxygen donor atoms of the ester groups of L ★ are not coordinated and the ligand thus acts as a C, N 2 terdentate system.

Fluxionality and bonding in formamidine and formamidinate complexes of Pt(II) and Pd(II) containing the 2,6-bis[(dimethylamino)methyl]phenyl ligand; A proton nuclear magnetic resonance study with X-ray crystal structure of [Pt{C6H3(CH2NMe2)2-2,6}{p-MeC6H4N=CHN(H)C6H4Me-p}][CF3SO3] [Pt{C6H3(CH2NMe2)2-2,6}{p-MeC6H4N=CHNC6H4Me-p)]

The N1,N2-di-p-tolylformamidine ligand [p-McC6H4NCHN (H)C6H4Me-p, Hdptf] reacts smoothly with the ionic species [M{C6H3(CH2NMe2)2-2,6}(H2O)]X (M = Pd or Pt, X = BF4– or CF3SO3–) to generate [M{C6H3(CH2NMe2)2-6}(Hdptf)]X [M = Pd (1) or Pt (2)]. The 1H n.m.r. data (250-MHz, CD2Cl2) for (2)(room temperature) and (1)(203 K) are consistent with a rigid monodentate bonding mode of neutral Hdpft; for the palladium species (1) Hdptf dissociation becomes an important process at higher temperatures. The structure of (2b)(M = Pt; X = CF3SO3–) was revealed by a single-crystal X-ray diffraction study. Crystals of this complex are triclinic, space group P1, with unit-cell dimensions a= 11.912(3), b= 14.372(6), c= 9.449(5)A, α= 92.04(4), β= 95.28(3), γ= 72.40(3)°, and Z= 2. Structure solution and refinement by standard methods gave R= 0.046 for 5 421 independent reflections. Complex (2b) is the first structurally characterized organometallic species containing a neutral formamidine and it possesses a monodentate imine-N2 bonding mode of neutral Hdptf to an approximately square planar PtII centre [Pt–N (3)= 2.16(1)A]. The cationic species (1) and (2) react with NaOH to afford, in high yield, neutral [M{C6H3(CH2NMe2)2-2,6}(dptf)][M = Pd (3) or Pt (4); dptf =p-McC6H4NCHNC6H4Me-p] for which low-temperature 1H n.m.r. studies indicate the uncommon σ-N1 monodentate bonding mode of the formamidinate anion. However, at room temperature in CD2Cl2 both (3) and (4) are subject to an intramolecular fluxional process that would be consistent with the existence of a chelate bonded formamidinate intermediate. A single-crystal X-ray study of (4) has been carried out. Crystals of this complex are monoclinic, space group P21/n, with unit-cell dimensions a= 17.28(2), b= 15.148(6), c= 9.62(2)A, = 101.1(2)° and Z= 4. In a manner analogous to that used for (2b) the structure of (4) was solved to R= 0.024 for 4 211 independent reflections. The virtually flat N1,N2-di-p-tolylformamidinate ion is σ-N1 monodentate bonded [Pt-N(3)= 2.1 32(6)A] and is orientated almost perpendicular to the co-ordination plane of this approximately square-planar PtII species.