title: π-Excess σ2P ligands: synthesis of biaryl-type 1,3-benzazaphosphole hybrid ligands and formation of P^P'-M(CO)4 chelate complexes.
abstract: Acid-catalyzed cyclocondensations of 2-phosphanylanilines 1 with substituted benzaldehydes or heteroaryl aldehydes open a convenient route to new biaryl-type 1H-1,3-benzazaphosphole hybrid ligands 2a-f with o-phosphanylphenyl, pyridyl, imidazolyl, thienyl or o-methoxyphenyl donor groups (in addition to the σ(2)P donor) and to bromophenyl substituted benzazaphospholes 2g,h. Excess aldehyde leads to concomitant reductive N-alkylation, as shown by formation of 3h besides 2h. The reactions proceed via dihydrobenzazaphospholes 4, which can be detected under mild conditions. The aromaticity-driven dehydrogenation does not liberate dihydrogen but is accomplished by transfer hydrogenations, mainly by reduction of some of the aldehyde. N-Secondary 2-phosphanylanilines 5 also react with aldehydes to form the corresponding N-substituted benzazaphospholes 6. The formation of (P^P')M(CO)4-chelate complexes 8a (M = Cr) and 9a,b (M = Mo) was demonstrated by reaction with M(CO)4(norbornadiene). The crystal structure of 9a, determined in addition to the solution structure elucidation by multinuclear NMR spectra, confirms the chelate formation and reveals a trigonal environment for the low coordinated phosphorus, with the P-Mo(0) vector bent out of the benzazaphosphole ring plane by 14.4° (0.57 Å), together with axial chirality of the molecules in the racemic crystals by twisting of the benzazaphosphole and phenyl π-planes around the common C(2)-C(21) bond.
authors.affiliation: Institut für Biochemie, Anorganische Chemie, Ernst-Moritz-Arndt-Universität Greifswald, Felix-Hausdorff-Str. 4, D-17489 Greifswald, Germany.
authors.forename: Basit
authors.initials: B
authors.lastname: Niaz
authors.forename: Mohammed
authors.initials: M
authors.lastname: Ghalib
authors.forename: Peter G
authors.initials: PG
authors.lastname: Jones
authors.forename: Joachim W
authors.initials: JW
authors.lastname: Heinicke
mesh_terms: D001372:Aza Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D002248:Carbon Monoxide / Q000737:chemistry*; D002614:Chelating Agents / Q000138:chemical synthesis* / Q000737:chemistry; D002857:Chromium / Q000737:chemistry*; D056831:Coordination Complexes / Q000138:chemical synthesis* / Q000737:chemistry; D008024:Ligands; D008958:Models, Molecular; D015394:Molecular Structure; D010758:Phosphorus / Q000737:chemistry*
chemical_list: D001372:Aza Compounds; D002614:Chelating Agents; D056831:Coordination Complexes; D008024:Ligands; D002857:Chromium; D010758:Phosphorus; D002248:Carbon Monoxide