MeC CMe Research Articles

ChemInform Abstract: Associative Ligand Substitution Reactions of Low‐Valent Rhenium‐Oxo Compounds. Crystal and Molecular Structures of (ReO(MeCCMe)2L)SbF6, L = Pyridine and 4,4′‐Dimethyl‐2,2′‐bipyridine.

AbstractA series of rhenium‐oxo compounds (II) (including (IV)) is prepared, where L is a substituted pyridine or bipyridine ligand.

Transition metal complexes with bidentate ligands spanning trans‐positions. Part XIV. Some complexes of 2,11‐bis(diphenylphosphinomethyl)benzo[c]phenanthrene with platinum (0) and their reactivities

AbstractThe ligand 2,11‐bis(diphenylphosphinomethyl)benzo[c]phenanthrene (1) has been used to prepare complexes of the type [PtL(1)] (L  C2H4, CH2CHCO2Me, PhCCPh, MeCCMe, MeO2CCCCO2Me, (i‐Pr)O2CCCCO2(i‐Pr), Ph3P and CO). It is shown that these complexes are less labile than the corresponding species [PtL(Ph3P)2]. The preparation of complexes trans‐[PtX(R)(1)] by oxidative addition of RX (RX  PhCH2Br and Mel) to [Pt(C2H4)(1)] is described. The isolation of [PtO2(CH3)2CO(1)] is also reported.

Coordinatively unsaturated alkyne complexes: synthesis of mono and bis-alkyne complexes of tungsten (II)

Abstract [WBr 2 (CO 4 ] n reacts with alkynes to give complexes [WBr 2 CO(RCCR) 2 ] 2 (1) (R = R′ = Me, Et, Ph; R = Me, R′ = Ph), which react with nucleophiles L{L = CNBu t , PPh 3 , or P(OMe) 3 } to give monoalkyne derivatives (WBr 2 (CO)(RCCR′)L 2 ](2). An intermediate bis-alkyne adduct [WBr 2 CO(MeCCMe) 2 (CNBu t )] (3) was isolated in the reaction of [WBr 2 CO(MeCCMe) 2 ] 2 with CNBu t illustrating that cleavage of the dimer (1) is the first stage in these reactions.

Syntheses and X-ray crystal structures of [Ru4(CO)12(MeCCMe)] and [Ru6C(CO)15(MeCHCH–CHCHMe)], products of the reaction of ethylene with [Ru3(CO)12

The reaction of ethylene with [Ru3(CO)12] yields, amongst others, the products [Ru4(CO)12(MeCCMe)](1) and [Ru6C(CO)15(MeCHCH–CHCHMe)](2), both of which have been characterised by single-crystal X-ray analysis; (2) contains a novel six carbon-atom chain co-ordinated across an edge of the octahedral cluster.

The structures and dynamic behavior of some polynuclear alkyne-rhodium complexes

The known complex, trans -(η-C 5H 5) 2Rh 2(CO) 2(CF 3C 2CF 3) is formed in high yield from (η-C 5H 5)Rh(CO) 2 and CF 3FCCF 3 at 100°. The less stable cis -isomer of the complex is obtained in low yield from the same reaction. The infrared, 1H, 19F and 13C NMR spectra of the two isomers are compared. The trans -isomer undergoes CO scrambling in solution at room temperature, and the variable temperature 13C NMR spectra are consistent with a pairwise bridge opening and closing mechanism. The mechanism is extended to account for the isomerization of cis to trans isomer, whihc has a half-life of 12 h at room temperature. The 13C spectrum indicates that the cis -isomer is static in solution at room temperature. The trans -isomer is reversibly protonated by protonic acids, and BF 4 − and PF 6 − salts of the protonated species can be isolated. The spectroscopic properties of these salts are consistent with protonation at one of the alkynyl-carbons, but it is not possible to distinguish between two alternative structures for the complex cation. Treatment of (η-C 5H 5) 2Rh 2(CO) 2(CF 3C 2CF 3) with (η-C 5H 5)Rh(CO) 2 gives the trinuclear complex (η-C 5H 5) 3Rh 3(CO)(CF 3C 2CF 3) in 80% yield. The analogoug but-2-yne complex is formed from (η-C 5H 5) 3Rh 3(CO) 3 and MeCCMe. The infrared, 1H, 19F and 13C NMR spectra indicate that the hexafluorobut-2-yne complex exists in two different structural arrangements in solution. One has an edge bridging, and the other a face bridging carbonyl. The proportion of the isomers is affected by the solvent polarity. The spectra of the but-2-yne complex indicate it is fluxional at room temperature, and has a face bridging structure in solution regardless of the polarity of the solvent. Reversible protonation of the hexafluorobut-2-yne complex occurs in protonic acids, and the salt [(η-C 5H 5) 3Rh 3(CO)(CF 3C 2CF 3)H] +[BF 4] −,H 2O can be isolated. The spectroscopic properties of this complex are consistent with a structure incorporating an edge-bridging carbonyl, and probably, an edge-bridging hydride ligand.

Reaction of di-μ-chlorobis(η 3-4-phenyl-1,2,3,4-tetra-p-tolyl cyclobutenylpalladium) with but-2-yne

Reaction of [Pd(η 3-C 4PhTo 4)Cl] 2 with MeCCMe gave an isomeric mixture of composition [Pd(η 3-C 6Me 2PhTo 4)Cl] 2, (II), which was converted into a single compound [Pd(η 3-C 6Me 2PhTo 4)(acac)] (III), on reaction with Tl(acac). Complexes (II) and (III) exhibited dynamic NMR spectra; the low temperature limiting spectra showed that the metal was η 3-bonded to a benzylic group in the molecule. Structures are proposed for (II) and (III) and their relation to the PdCl 2 induced cyclotrimerisation of acetylenes is discussed.