Rolf H. Reimann

Transition metal carbonyls : IV. Substitution reactions of rhenium pentacarbonyl bromide☆

Abstract Treatment of Re(CO) 5 Br with an excess of L has given mer - cis -[Re(CO) 2 L 3 Br] for a wide range of tertiary phosphine and phosphite ligands. There was a marked temperature effect on these reactions. The disubstituted products fac - and mer - trans [Re(CO) 3 L 2 Br] have also been characterised. The carbonylations of mer - cis -[Re(CO) 2 L 3 Br] to give mer - trans -[Re(CO) 3 L 2 Br] have been shown to be dependent only upon the size of the ligand L. Qualitative studies on the reactions of fac - and mer - trans -[Re(CO) 3 L 2 Br], [L=P(OPh) 3 and PEt 2 Ph] have inferred that mer - cis [Re(CO) 2 L 3 Br] only forms from the mer - trans -disubstituted isomer. The IR and 1 H NMR data for these complexes are discussed.

New diphosphine-substituted carbonyl complexes of manganese

Abstract Treatment of Mn 2 (CO) 10 with the diphosphines Ph 2 P(CH 2 ) 2 PPh 2 (DPE) and Ph 2 PCH 2 PPh 2 (DPM) has given, in addition to the known products Mn(CO) 3 (DPE) and Mn(CO)(DPE) 2 , a dimeric species containing a single diphosphine bridge and complexes of stoichiometry [Mn(CO) 3 L 2 ] 2 , (L 2 = DPE or DPM). Evidence has been obtained for the possible existence of a second conformer of Mn(CO)(DPE) 2 . With Mn(CO) 5 Br, up to four carbonyl groups have been replaced to give the unusually highly substituted compounds Mn(CO)(L 2 ) 2 Br, (L 2 = DPE or DPM). These results are interpreted in terms of the steric and chelating properties of the diphosphine ligands.

A simple route to new cationic carbonyl compounds of manganese and rhenium

Abstract [Mn(CO) 3 (CH 3 CN) 3 ]PF 6 has been prepared and shown to be a useful precursor for a potentially wide range of new cationic manganese carbonyl compounds. The corresponding rhenium compound has also been prepared.

Conversion of bonded cyclo-octadiene into a cyclo-octadienyl ligand and cleavage of boron–phenyl bonds of arene-bonded tetraphenylborate anions in ruthenium(II) systems: X-ray crystal and molecular structures of [Ru(η6-C6H5BL3)(1–3,5,6-η-C8H11)](L = Ph or F)

Labilisation of the hydrazine ligands in either [Ru(cod)(N2H4)4][BPh4]2(I; cod = cyclo-octa-1,5-diene) or [RuH(cod)(NH2NMe2)3][BPh4](II) in acetone produces [Ru(η6-C6H5BPh3)(1–3,5,6-η-C8H11)] which reacts with HA (A = BF4 or PF6) to give [Ru(η6-C6H5-BF3)(1–3,5,6-η-C8H11)]; a byproduct of the reaction with (II) is [Ru(cod)(C6H6)].

Structural studies of substituted hydrazine complexes. Part 3. Crystal and molecular structure of dichlorobis(η-cyclo-octa-1,5-diene)-(NN-dimethylhydrazine)dihydridodiruthenium, an asymmetric triply bridged dimer containing a bidentate bridging NN-dimethylhydrazine ligand

Crystals of the title complex are monoclinic, space group P21/c, with unit-cell dimensions a= 17.99(2), b= 7.46(2), c= 20.91(2)A, and β= 133.8(1)°. A final R of 0.073 for 1 487 observed reflections has been obtained. The molecule is a highly distorted dimer with the two ruthenium atoms bridged by H–, Cl–, and NH2NMe2 ligands. Terminal chloride and hydride ligands are situated trans to, respectively, the bridging H– and Cl– ligands, and an η-cyclo-octa-1,5-diene is co-ordinated to each ruthenium atom. The methyl-substituted nitrogen is bonded to the ruthenium which carries the terminal H– ligand. A unique structural feature is the bidentate bridging NH2NMe2 ligand: Ru–NH2 2.12, Ru–NMe2 2.24, and N–N 1.51 A; Ru–NH2–N 115 and Ru–NMe2–N 103°. The Ru⋯Ru distance (2.91 A) indicates the presence of a metal–metal bond of order one.

Synthesis of cationic carbonyl cyclopentadienyl complexes of molybdenum and tungsten, and X-ray crystal structure of (acetone hydrazone)-tricarbonyl(η-cyclopentadienyl)tungsten hexafluorophosphate

Substitution of the hydrazine ligand in [Mo(η-C5H5)(CO)3(N2H4)]Cl with a range of commonly used tertiary phosphine and phosphite ligands (L) has provided a new high-yield route to [Mo(η-C5H5)(CO)3L]+ cations for the majority, but not all, of the ligands used. With phosphonites, phosphinites, and smaller phosphines there is a competing reaction to give [Mo(η-C5H5)(CO)2L2]+ cations. Reaction of [W(η-C5H5)(CO)3(N2H4)] Cl with PPh3and PMePh2 gives [W(η-C5H5)(CO)3L]+(L = PPh3 or PMePh2) and [W(η-C5H5)(NCO)(CO)2(PPh3)], depending on the reaction conditions. The complexes [M(η-C5H5)(CO)3(N2H4)]Cl (M = Mo or W) react with acetone to give the respective hydrazone cations [M(η-C5H5)(CO)3(NH2NCMe)]+, which are thermodynamically more stable than the hydrazine precursors; [Mo(η-C5H5)(CO)3(NH2NCMe2)]+ is converted into [Mo(η-C5H5)(CO)2-(solvent)2]+ in-polar solvents at room temperature. The crystal and molecular structure of [W(η-C5H5)(CO)3-(NH2NCMe2)][PF6] has been determined from three-dimensional X-ray data collected by counter methods. The structure has been refined by full-matrix least-squares techniques to a final R(on F) of 0.030, based on 2 141 reflections. The complex crystallises in the triclinic space group P with two molecules in a cell of dimensions a= 10.81 (2), b= 9.74(2), c= 8.47(2)A, α= 113.3(1), β= 96.0(1), and γ= 95.1 (1)°. The tungsten atom is formally seven co-ordinate and the complex is best described as possessing the ‘piano-stool’ geometry. The major feature is the mode of bonding of the hydrazone ligand, which is shown to occur through the amino-nitrogen atom, in contradiction to current theories on the bonding of hydrazones to transition metals. Possible factors in-fluencing the relative stability of amino- or imino-nitrogen bonding are discussed.

Cationic ruthenium systems. Part 4. Bridge-splitting reactions of the triply bridged dimers bis(η-cyclo-octa-1,5-diene)(NN-dimethylhydrazine)dihalogenodihydridodiruthenium with a series of neutral donor ligands

The triply bridged complexes [{RuX(H)(cod)}2(NH2NMe2)](2; X = Cl or Br; cod = cyclo-octa-1,5-diene), containing H, X, and NH2NMe2 as bridging ligands, have been prepared from [RuH(cod)(NH2NMe2)3]A (1; A = PF6 or BPh4) and LiX in moderate yields from acetone–methanol mixtures. The mother liquors of these reactions produced [Ru3(CO)12] and [RuX(H)(PPh3)3] with CO and PPh3 respectively. Complexes (2) undergo bridge-splitting reactions with a series of neutral donor ligands to produce [RuX(H)(cod)L2][3; L = PMePh2, SbPh3, AsPh3, or pyridine (py)], [RuCl(H)(PPh3)3], [RuH{PPh(OMe)2}5][PF6], [RuH(cod)L3]+(L = 4Me-py or NCMe), and [RuCl2(4Me-py)4]. Infrared and 1H n.m.r. data for the complexes are discussed.

An investigation into the mechanism of conversion of fac-[Mn(CO)3{P(OMe)2Ph}2X] (X = Cl Br) into mer-cis-[MnCO2{P(OMe)2Ph}3X] in the presence of P(OMe)2Ph

Abstract The complex mer-trans -[Mn(CO) 3 {P(OMe) 2 Ph} 2 X] (X = Cl, Br) is an intermediate in the conversion of fac -[Mn(CO) 3 {P(OMe) 2 ,Ph} 2 ,X] into mer - cis -[Mn(CO) 2 {P(OMe) 2 Ph} 3 X] in the presence of P(OMe) 2 Ph in benzene. No direct route between the latter two complexes could be detected kinetically. The results imply a trans carbonyl disposition as a prerequisite for higher carbonyl substitution in octahedral Mn 1 carbonyl complexes.

NO2 as a single electron oxidant

Abstract Nitrogen dioxide has been shown to possess powerful oxidative properties which are a major effect in certain nitrosylation reactions; it has also been shown to provide a route to dicationic substituted manganese carbonyl salts.

Factors limiting higher substitution of manganese pentacarbonyl bromide

Abstract Successive substitution of [Mn(CO)5Br] with phosphines and phosphites (L) have been shown to be dependent upon the size of L and the stereochemistry of the manganese complex.