Presentations IIb

Presentations IIb - 0 3 Thus, 9H = 2A1’...

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Unformatted text preview: 0 3 Thus, 9H = 2A1’+A2’’+2E’+E’’. Ch102 PresentaHon May 10, 2011 by Luis Navarro BCl3 •  •  •  •  •  •  •  •  For the series BX3 (X = F, Cl, Br, I), the boron ­halogen bond length increases down the group as is expected by increasing atomic radii. BCl3 melts at  ­107o C and boils at 12o C. However, it is available in methylene Oxidation chloride soluHon, making it convenient. State +3 - 2 0 0 +3 - 1 +2 - 2 Synthesis: B2O3 + 3 C + 3 Cl2 2 BCl3 + CO BCl3 can be synthesized by direct chlorinaHon of B2O3. This process uses chlorine as an oxidant (becomes reduced) and graphite as a reductant (becomes oxidized). It can also be prepared by mixing BF3 with AlCl3 in lab by halogen exchange. BCl3 melts at  ­107o C and boils at 12o C. However, it is available in methylene chloride soluHon. Its volaHlity also allows it to be removed by vacuum, making it very convenient to work with. BCl3 is used as a starHng material for elemental boron. It is also used for plasma etching in manufacture of semiconductor. It can also be used as an alternaHve to AlCl3 in Friedel ­CraQs. BCl3 can also be used to make new carbon boron bonds. The molecule is very electrophilic due to mostly boron’s empty p orbital in the LUMO. Thus, this molecule can be aVacked by nucleophilic carbons (like Grignards or cuprates) to make new C ­B bonds. Reference: HousecroQ and Sharpe, Inorganic Chemistry, 3rded., 2008. Pages 340 ­341. BCl3 is a D3h molecule •  The BCl3 HOMO is a non ­bonding A’2 with contribuHon solely from chlorine 2px/y orbitals. •  BCl3 is a trigonal planar molecule. There is a σh plane on the plane of the molecule, a C2 axis through a B ­Cl bond, and a C3 axis perpendicular to the plane of the molecule. •  The BCl3 LUMO is far more important. It is an A”2 π* anH ­bonding orbital. The LUMO has most of its contribuHon from the boron pz orbital. The large lobes of the LUMO by the boron make this molecule a very good Lewis acid. Copper • Copper the least reac-ve of first row metals. When heated strongly, Cu combines with O2 (as well as the Halogen gases produce): • 2Cu + O2 + (heat) 2CuO (> 1300K) Cu2O + (1/2) O2 • Copper oxida-on: 0 +2 +1 (oxidized then reduced) • Oxygen oxida-on: 0 ­2average is  ­1 (half of the original oxygen goes back to 0 oxida-on state) (reduced then oxidized) • Copper (IV) is rare. It exists in the red Cs2CuF6 made by fluorina-ng CsCuCl3 at 520K, and has a distorted octahedral structure • Diamagne-c structures like K[CuO2] and K7[Cu(IO6)2] has square planar symmetry: • The d ­orbitals are lower in energy if it is in the dz2 because the metal ligands are not along the axis of the orbitals. The orbitals in the xy plane will be higher in energy than the ones in the xz and yz. (CuCl2 ) ­1 was used to model Cu(I) HOMO Because there is a center of inversion, the IR modes and the Raman modes are complementary LUMO Housecro_, P.733 ­734 Ch 102, Ben Suslick Prussian Blue and Analogue Salts •  CN- bridges allow electronic communication between metal centers resulting in a ferromagnetic material (spins in same direction); molecular based magnets •  PB structure can be modified by exchanging metal centers with Ni, Cr, Mn, etc. Can exchange some axial CN with NO to create potentially interesting compounds (see Girolami) •  Synthesized from mixing soluble Prussian Blue analogue salts, ie K3[Fe(CN) 2+ 6] aka potassium hexacyanoferrate (III), with Fe ions •  K3[Fe(CN)6] is a deep red salt, with octahedral point group •  [Fe(CN)6]3- has a low spin Fe(III) with µeff = 2.25 µB •  [Fe(CN)6]3- is synthesized from [Fe(CN)6]4-: •  2K4[Fe(CN)6] + Cl2 2K3[Fe(CN)6] + 2KCl +1 +2 -1 per CN 0 +1 +3 -1 per CN +1 -1 •  Fe is oxidized, Cl2 is reduced •  E count on [Fe(CN)6]4- (EC method): •  Fe2+ : 6 e- ; 6*CN- = 6*2 = 12 e•  18 electrons total, with d6 count on Fe References: Housecroft and Sharpe, Inorganic Chemistry, 3rd ed., 2008. pg 717-719 Fe(CN)64- MOs Calculated IR spectrum; peaks at 88.3 (Eu), 123.3 (T1g), 346.2 (T1u), 393.5 (Eu), 2131.5 (A2u), 2138 (Eu) cm-1 Fe(CN)64- HOMO (right), and LUMO (left). Notice HOMO is π anti bonding between Fe-C and π bonding between C-N; axial CN groups have no electron density. T he LUMO is anti bonding between Fe-C and C-N. Notice large s like lobe on C. Axial CN groups have no electron density. Palladium(II) Halides • All Pd(II) halides are known • PdF2 is paramagnetic; all others are diamagnetic • Syntheses:0 0 2 -1 Pd +Cl2 PdCl2 Pd + Br2 PdBr2 oxidant: Cl reductant: Pd • Below 820 K, PdCl2 makes a square planar polymer, but above that temp, it makes hexamers, as shown above • Hydrated PdCl2 is used as a CO detector Pd(II)Cl2L2 • Point Group: D2h • Electron counting: Pd: 10 eCl: 2 x 1 eL: 2 x 2 eTotal valence: 16 e=> PdII, d8 Reference: Housecroftand Sharpe, Inorganic Chemistry, 3rd ed., 2008. pp 790-793 PdCl2L2 B3u Ag B2u Ag Ag HOMO: nonbonding Ag LUMO: sigma antibonding Reference: Housecroftand Sharpe, Inorganic Chemistry, 3rd ed., 2008. pp 790-793 ...
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This note was uploaded on 01/03/2012 for the course CH 102 taught by Professor Hill,m during the Fall '08 term at Caltech.

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