G.J.M. van der Kerk

Preparation and properties of arylgold compounds. Scope and limitations of the auration reaction

Several ligand-free monoarylgold dichlorides (RC6H4AuCl2)2 (R = H, Me, Et, i-Pr, t-Bu, Ph) have been prepared from arenes and AuCl3; contrary to earlier reports, addition of ligands is not necessary in order to obtain thermally stable products. The auration is inhibited if the arenes contain potentially coordinating substituents. The properties and reactions of the arylgold dichlorides are discussed.

Investigations on organotin compounds XX. The existence of complexes with five-co-ordinated tin in solutions

N-Tributylstannylimidazole forms complexes with basic ligands (B) in which the tin atom becomes pentacovalently bound. In the general structure Bu3SnImB, B may be another molecule of Bu3SnIm, which gives rise to the formation of a co-ordination polymer. In inert solvents this polymer causes the viscosity to rise sharply with increasing concentration. The efficiency of competing complexing agents can be evaluated by following the decrease of the viscosity of solutions of Bu3SnIm upon addition of these agents. Results are (i) that association of Bu3SnIm occurs more readily than association of imidazole over hydrogen bridges, (ii) that Bu3SnIm is complexed preferentially by either second row atoms (P, S) or by unsaturated ligands. A possible explanation, involving stabilization of the complexes by back donation of dπ-electrons from the tin atom towards the ligands, is discussed.

Synthesis and coordination properties of ω-functionally-substituted dialkylzinc compounds

Abstract The synthesis and characterization are described of ω-functionally-substituted dialkylzinc compounds of the type Zn[(CH 2 ) 3 X] 2 , (X = OCH 3 , SCH 3 , N(CH 3 ) 2 ). For comparison, one higher homologue, viz. Zn[(CH 2 ) 4 OCH 3 ] 2 , was also prepared and studied. The chemical properties, degrees of association, dipole moments and NMR spectral data point to exclusive intramolecular coordination between zinc and the hetero-atoms present.

Reaction of diarylzinc compounds with copper(I) salts. Synthesis and characterization of arylcopper(I) compounds

Abstract The reaction of diarylzinc compounds with copper(I) salts is an excellent way of preparing stable arylcopper compounds in quantitative yields. These compounds have been characterized by IR, and by 1H and 13C NMR spectroscopy. Cryoscopic molecular weight determinations show phenylcopper to be polymeric and 2-methylphenylcopper and 2,6-dimethylphenylcopper to be tetrameric in benzene. The compounds are believed to contain aryl groups bridging two copper atoms. Evidence is presented for rotation of these aryl groups around the C(1)—C(4) axis.

Studies in IVth group organometallic chemistry : XV. Base-catalyzed hydrolysis of a series of IVth group organometallic esters

The esters R3M(CH2)nCOOEt (R = Et, M = Si, Ge or Sn, n = 1, 2 or 3, and R = Me, M = Ge, n = 2) were prepared. The rates of alkaline hydrolysis were determined, except for the compounds with n = 1, for which metal-carbon bond cleavage occurs. The rates of hydrolysis of the substituted propionates (n = 2) were found to be relatively high. A possible explanation, involving interaction in the transition state between the carbonyl oxygen and the metal atom, is proposed. In the hydrolysis of the substituted butyrates (n = 3), differences between the effects of the metal atoms were not apparent.

The addition of methylborylene to acetylenes: Synthesis of 1,4-diboracyclohexa-2,5-dienes, and of a borirene and a diboretene derivative

Abstract The synthesis of 1,4-dimethyl-2,3,5,6-tetra- n -alkyl-1,4-diboracyclohexa-2,5-dienes from the reaction of di- n -alkylacetylenes with the methylborylene-generating system 2C 8 K/MeBBr 2 is described. A mechanism for these reactions is proposed. The addition of methylborylene to di- t -butylacetylene results in the formation of 1-methyl-2,3-di- t -butylborirene and of 1,3-dimethyl-2,4-di- t -butyl-1,3-diboretene.

Investigations on organolead compounds V. Lead---lead bond cleavage reactions of hexaphenyldilead

Abstract It has been shown that a number of nucleophilic and weakly electrophilic reagents (organolithium and organomagnesium compounds, metallic lithium, potassium permanganate, sodium ethoxide, diaryl disulphides, sulphur, ozone, hypochlorous acid and iodine/iodide) selectively cleave the leadlead bond of hexaphenyldilead. No leadphenyl bond cleavage occurs with these reagents. The reactions with lithium, potassium permanganate, diaryl disulphides, ozone, hypochlorous acid and iodine/iodide form useful synthetic procedures for the preparation of triphenyl-lead derivatives from the readily available hexaphenyldilead.

Studies in group IV organometallic chemistry : XIV. Ultraviolet absorption due to bonds between group IV metals☆

Abstract Ultraviolet absorption spectra are discussed for a number of molecules containing metal-metal bonds, viz. (C 6 H 5 ) 6 Sn 2 , (C 6 H 5 ) 6 Pb 2 , (cyclohexyl) 6 Pb 2 , [(C 6 H 5 ) 3 Sn] 4 M, and [(C 6 H 5 ) 3 Pb] 4 M with M  Pb, Sn, and Ge. Long wavelength absorptions are attributed to the metallic part of the molecules.

Investigations on organolead compounds VIII. Reactions of (triorganoplumbyl)metal reagents With polychloromethanes; Tetrakis(triphenylplumbyl)methane and related compounds

Abstract Triphenylplumbyllithium couples readily in tetrahydrofuran with carbon tetrachloride, chloroform and dichloromethane to produce the following compounds in good yields: (Ph 3 Pb) 4 C, (Ph 3 Pb) 2 CCl 2 , Ph 3 PbCCl 3 , (Ph 3 Pb) 3 CH, Ph 3 PbCHCl 2 , and (Ph 3 Pb) 2 CH 2 . The structure of (Ph 3 Pb) 4 C was confirmed by converting it into (Ph 2 PbBr) 4 C. Similarly (Me 3 Pb) 4 C was prepared from trimethylplumbylsodium and carbon tetrabromide in liquid ammonia.

The synthesis and properties of some organometallic compounds containing group IV (Ge, Sn)-group II (Zn, Cd) metalmetal bonds

Abstract The reactions of triphenylgermane and triphenyltin hydride with coordinatively saturated organozinc or organocadmium compounds give organometallic complexes containing Group IV (Ge, Sn)-Group II(Zn, Cd) metalmetal bonds. The 2,2′-bipyridine complexes show solvent-dependent charge-transfer absorptions in the visible region. The occurrence of charge transfer may account for the observation that the metal-metal stretching frequencies of the Bipy complexes are consistently lower than those of the corresponding TMED complexes.