title: Reaction products of W(CO)(6) with formamidines; electronic structure of a W(2)(mu-CO)(2) core with unsymmetric bridging carbonyls.
abstract: Reactions of W(CO)(6) with formamidines contrast with those of Mo(CO)(6) and Cr(CO)(6) in that the former do not yield quadruply bonded dimetal species. From the reaction of W(CO)(6) with HDAniF (HDAniF = N,N'-di-p-anisylformamidine), several new ditungsten carbonyl compounds (W(2)(mu-CO)(2)(mu-DAniF)(2)(eta(2)-DAniF)(2) (1), W(2)(mu-CO)(2)(mu-DAniF)(2)(eta(2)-DAniF)(eta(2)-CH(2)DAniF) (2), and W(2)(mu-CO)(mu-CNC(6)H(4)OCH(3))(mu-DAniF)(2)(eta(2)-DAniF)(2) (3)) have been isolated and fully characterized. In 2, CH(2)DAniF represents a DAniF ligand in which a methylene group has been added to one of the nitrogen atoms. This ligand binds to the tungsten atom using a nitrogen and a carbon atom. Compound 1 has a tungsten-tungsten bond distance of 2.476(1) A and a planar W(2)(mu-CO)(2) core structure which has C(2)(h)() symmetry with short and long W-C bond distances (1.99(1) and 2.28(1) A, respectively). DFT calculations on a model of 1 indicate that (a) the C(2)(h)() instead of D(2)(h)() symmetry of the ditungsten core may be attributed to W --> CO pi back-bonding interactions and (b) the bond between the tungsten atoms may be formulated as a double bond. The new tetragonal paddlewheel compound W(2)(DAniF)(4) (4) and the edge-sharing bioctahedron W(2)(mu-O)(mu-NC(6)H(3)Cl(2))(mu-D(Cl)PhF)(2)(eta(2)-D(Cl)PhF)(2) (5) (D(Cl)PhF = N,N'-di-(3,5-dichlorophenyl)formamidinate) have also been prepared.
authors.affiliation: Laboratory for Molecular Structure and Bonding, Department of Chemistry, P.O. Box 30012, Texas A and M University, College Station, Texas 77842-3012, USA. cotton@tamu.edu
authors.forename: F Albert
authors.initials: FA
authors.lastname: Cotton
authors.forename: James P
authors.initials: JP
authors.lastname: Donahue
authors.forename: Michael B
authors.initials: MB
authors.lastname: Hall
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Murillo
authors.forename: Dino
authors.initials: D
authors.lastname: Villagrán
mesh_terms: D000578:Amidines / Q000737:chemistry*; D002244:Carbon / Q000737:chemistry; D018360:Crystallography, X-Ray; D004563:Electrochemistry; D008968:Molecular Conformation; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry; D014414:Tungsten / Q000737:chemistry*
chemical_list: D000578:Amidines; D009942:Organometallic Compounds; C077922:formamidine; D002244:Carbon; D010100:Oxygen; D014414:Tungsten