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Organometallic Chemistry Chem 432 Outline Bonding The 18-electrons rule Hapticity Isolobal relationships Metal carbonyl complexes Metal nitrosyl complexes Metal hydride complexes Alkyl and acyl metal complexes Metal alkene and alkyne complexes Ligands with delocalized p bonding metallocenes Scorpionates Why octahedral complexes obey the 18-electron rule eg t2g d 6 ligands 12 electrons Why square planar complexes tend to have 16 electrons M.C. White, Chem 153 Structure & Bonding -8- Week of September 17, 2002 1 1 η ligands Formal # of e- η -Ligands (monodentate): charge donated Hapticity (ηx): The number of atoms (x) in the ligand binding H (hydride) -1 2 to the metal η2-alkyl CH (alkyl) -1 2 terminal oxo 3 peroxo t-Bu CO 0 2 O O 2 X (halides) -1 OR 4 V O V µ-X (bridging) -1 O OR Common (2/metal) O X O O M M O 2 OR (terminal -1 η1-alkyl peroxo Ligands alkoxide) t-Bu µ-OR (bridging) -1 4 R (2/metal) Proposed intermediates in VO(acac) catalyzed directed epoxidation of O 2 M M allylic alcohols. Sharpless Aldrichimica Acta 1979 (12), 63. OR (ether) 0 2 2 Bridging ligands (µ): the ligand bridges 2 or more metals O2 (superoxide) -1 2 linear µ-oxo O (terminal oxo) -2 4 µ-O (bridging) -2 4 O (2/metal) M M N PR2 (phosphide) -1 2 N 2 PR3 (phosphine) 0 N Cl N Fe O Fe NR (amide) -1 2 2 N N Cl NR3 (amine) 0 2 N N imines 0 2 nitriles 0 2 2 M.C. White, Chem 153, Harvard University NO (nitrosyl ) li near +1 Nishida Chem. Lett. 1995 885. Hapticity Monohapto Ligands J. Chem. Ed. 1990, vol 67, p. 294 Polyhapto Ligands J. Chem. Ed. 1990, vol 67, p. 294 M.C. White, Chem 153, Harvard University M.C. White,M.C. Chem White, 153 Chem 153 StructureStructure & Bondin &g Bondin-10- g -10- Week of WeekSeptember of September 17, 2002 17, 2002 UnsaturatedUnsaturatedUnsaturated Ligands Ligands Ligands Formal Formal# of e- # of e- Formal Formal# of e- # of e- 1 1 x x η -coordination η -coordination charge chargedonated donated η -coordination η -coordinationcharge chargedonated donated M M -1 -1 2 2 0 0 6 6 M M 1 1 η -aryl η -aryl η6-arene η6-arene -1 -1 2 2 0 0 2 2 M M M M 1 1 η -alkenyl η -alkenyl η2-alkene η2-alkene RHRH RMRM -1 -1 2 2 M M 0 0 2 2 1 1 η -alkynyl η -alkynyl η2-alkyne η2-alkyne H H -1 -1 2 2 -1 -1 6 6 M M M M η1-Cp (cyclopentadienyl)η1-Cp (cyclopentadienyl) η5-Cp (cyclopentadienyl)η5-Cp (cyclopentadienyl) M M M MM M = = M M -1 -1 2 2 -1 -1 4 4 1 1 η -allyl η -allyl η3-allyl η3-allyl O O O O M M M M O O -1 -1 2 2 O O -1 -1 4 4 η1-acetate η1-acetate η2-acetate η2-acetate Isolobal Relationships n LnM d CHm L2M 10 CH2 L3M 9 CH L4M 8 CH2 L5M 7 CH3 L5M 6 CH2 L5M 5 CH L6M 5 CH3 L4M 9 CH3 L3M 10 CH2 J. Chem. Ed. 1990, vol 67, p. 294 Isolobal Relationships CH3 Cr(CO)3Cp Mn(CO)5 Fe(CO)2Cp Co(CO)4 Ni(CO)Cp Cu(CO)3 CH2 Cr(CO)5 Mn(CO)2Cp Fe(CO)4 Co(CO)Cp Ni(CO)2 CuCp CH Cr(CO)2Cp Mn(CO)4 Fe(CO)Cp Co(CO)3 NiCp Cu(CO)2 C Cr(CO)4 Mn(CO)Cp Fe(CO)3 CoCp Ni(CO) J. Chem. Ed. 1990, vol 67, p. 294 Metal Carbonyl Complexes Preparation Metal Carbonyl Complexes Structure Metal-Carbonyl Bonding s donation M C O p back-bonding M C O Metal- Bridging Carbonyl Bonding s donation O C M M p back-bonding O C M M terminal bridging µ2 bridging µ3 Modes of bonding M p Modes of bonding Modes of bonding Modes of bonding Metal Nitrosyl Complexes Preparation NO+ is isoelectronic and isolobal with CO Metal Nitrosyl Complexes Structure Metal Hydride Complexes Preparation Reaction with hydroxide or borohydride anions Metal Hydride Complexes Preparation Protonation of the anion Metal Hydride Complexes Structure Alkyl and Acyl Metal Complexes Preparation Nucleophilic Addition alkyl acyl Alkyl and Acyl Metal Complexes Preparation Nucleophilic Addition Alkyl and Acyl Metal Complexes • CO Insertion Alkyl Metal Complexes Structure Acyl Metal Complexes Structure Metal Alkene Complexes R2 C C M R2 Zeise’s salt Metal Alkyne Complexes R C C M R Metal Alkyne Complexes O Ligands with delocalized p bonding three-legged piano stool four-legged piano stool Ligands with delocalized p bonding Ferrocene Discovered in 1951 x-ray structure in 1952 bis(η5-cyclopentadienyl)iron(II) Orange solid Catalyst for olefin polymerization Metallocenes two η5-cyclopentadienyl ligands bound to a metal center titanocene vanadocene Double Metallocenes Fused cyclopentadiene (pentalene) ligands Vanadium complex is h5 Nickel complex is h3 Iron does not form a double ferrocene JACS 2008, vol 130, p. 15662 Carbon-Free Metallocene Science 2002, vol 295, p. 832 Cyclobutadiene Ligands Arene Ligands Bonding with p donor ligands 2p and 3p ligand orbitals usually have the best match with M 3d orbitals Scorpionates Anionic tris(pyrazolyl)borate ligands Bind metal with N heteroatoms from 2 pyrazole rings attached to a central B The 3rd pyrazole rotates forward to ‘sting’ the metal Scorpionates Pyrazolyl borates provide large steric shielding of the metal allow for reactivity on the other side of the metal Nitrogen heterocycles other than pyrazole can be used pyrrole, imidazole, indole, indazole. Tripodal ligands can be multidentate with N, S, or P donor atoms Scorpionates Ytterbium tetraphenylporphyrin complex topped by a tris(pyrazolyl)borate ligand Polymer LED in near-IR Luminesces under applied voltage Writing can be seen with a near- IR camera Scorpionates Gold scorpionate complex binds to ethylene molecule Potential for catalysis Angew. Chem. 2007, vol 46, p. 7814.
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