Five‐ and Six‐Membered Cobaltocycles with C,P‐Chelating Ligands through Regiospecific Cyclometalation of Mono(2‐Substituted) Triphenylphosphane

Abstract

Abstract Cyclometalation in the aliphatic ring occurs in the reaction between [CoCH 3 (PMe 3 ) 4 ] and 5‐(diphenylphosphanyl)‐1,2,3,4‐tetrahydronaphthalene to give [{8‐(diphenylphosphanyl)‐1,2,3,4‐tetrahydronaphthyl‐( C 1 , P )}tris(trimethylphosphane)cobalt] ( 1 ), containing a five‐membered metallacycle as shown in the molecular structure. While 1‐(diphenylphosphanyl)naphthalene reacts accordingly, affording [{8‐(diphenylphosphanyl)naphthyl‐( C 1 , P )}tris(trimethylphosphane)cobalt] ( 2 ), 2‐(diphenylphosphanyl)biphenyl yields ortho ‐metalated [{2‐(diphenylphosphanyl)‐3‐phenylphenyl‐( C 1 , P )}tris(trimethylphosphane)cobalt] ( 3 ), containing a four‐membered metallacycle . 1‐ ( Diphenylphosphanyl)‐8‐methylnaphthalene is metalated in the aliphatic substituent to form [{[8‐(diphenylphosphanyl)naphth‐1‐yl]methyl‐( C , P )}tris(trimethylphosphane)cobalt] ( 4 ). The molecular structure shows a trigonal‐bipyramidal configuration of the cobalt atom accommodating a six‐membered metallacycle. 2‐(Diphenylphosphanyl)styrene replaces two trimethylphosphane ligands to give [{2‐(diphenylphosphanyl)styrene‐( C , C ‐η 2 , P )}methylbis(trimethylphosphane)cobalt] ( 5 ), avoiding metalation. Replacement of equatorial trimethylphosphane in compounds 1 − 3 by ethene gives π‐ethene complexes 6 − 8 . In the molecular structure of 7 the C−C vector of the π‐ethene ligand is arranged in the equatorial plane of a trigonal bipyramid. Under 1 bar of CO, compound 2 forms a monocarbonyl complex 9 , in which an equatorial carbonyl ligand is found in the molecular structure. Iodomethane transforms 2 into pentacoordinate [{2‐(diphenylphosphanyl)naphthyl‐( C 1 , P )}iodobis(trimethylphosphane)cobalt] ( 10 ) with retention of the metallacycle. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003