CHM 511 Special Topics: Nomenclature page 1 of 8

Transcription

1 CHM 511 Special Topics: Nomenclature page 1 of 8 Nomenclature of metal complexes What is a complex? Complex: a metal atom surrounded by ligands Ligand: an ion or molecule that can have an independent existence Coordination compound: a neutral complex or an ionic compound in which at least one of the ions is a complex Complex Ligand CC? CC possibility? Ag(NH 3 ) 2 + AgCl 2 - Fe(H 2 O) 6 3+ Ni(CO) 4 With complexes, we can discuss the inner coordination sphere versus the outer coordination sphere. EX. FeCl 3 6H 2 O EX. CoCl 2 6H 2 O From Shriver and Atkins, Inorganic Chemistry, 4th edition

2 CHM 511 Special Topics: Nomenclature page 2 of 8 Extra notes: 1. acac is acetylacetonate 2. NH 3 = ammine 3. CN -, attaches through C (usually) 4. NCO -, N attachment is the isocyanato ligand 5. SCN -, S attachment is the thiocyanato ligand 6. SCN -, N attachment is the isothiocyanato ligand 7. NO 2 -, nitro if N attachment 8. NO 2 -, nitrito if O attachment IUPAC suggestion Disclaimer on nomenclature rules: There are at least two systems (IUPAC and everyone else) and though there is general agreement on the big issues, sometimes the details are slightly different. I am presenting the most common system seen by ACS journals. 1. Writing formulas: write cation, then anion (just like simple salts) 2. The inner coordination sphere is enclosed in [ ]. Within the coordination sphere the ligands are named before the metal, but the metal ion is written first in a formula, followed by anionic ligands, followed by neutral or cationic ligands. Ligands are sometimes written to point out their attachment sites. 3. The number of ligands is indicated with Greek prefixes. If the ligand name includes a Greek prefix or is complicated, it is set off with parentheses and the second set of prefixes is used. 1. mono 6. hexa...hexakis 2. di...bis 7. hepta...heptakis 3. tri...tris 8. octa...octakis 4. tetra...tetrakis 9. nona...nonakis 5. penta...pentakis 10. deca...decakis EX. [X(NH 3 ) 2 ] n+ versus [X(CH 3 NH 2 ) 2 ] n+

3 CHM 511 Special Topics: Nomenclature page 3 of 8 4. Ligand endings: Anionic ligands are given an "o" suffix Neutral or cationic ligands retain their name Coordinated water is "aqua" (not aquo!) EX. Name the following ligands Cl - H 2 O Br - CH 3 NH 2 SO 4 2- C 2 O 4 2- NH 3 CO 5. Write ligand names alphabetically (ignoring Greek prefixes), with no spaces between parts of names. Avoid abbreviations in the name. EX. [Cu(NH 3 ) 4 ] 2+ [Cu(NH 3 ) 4 ]SO 4 [Co(NH 3 ) 6 ]Cl 3 [CoCl 2 (NH 3 ) 4 ] + a complex with ethylenediamine (en), [CoCl 2 (NH 2 CH 2 CH 2 NH 2 ) 2 ] + a complex with 2,2 -bipyridine (bipy), [Fe(C 5 H 4 N-C 5 H 4 N) 3 ] 2+

4 CHM 511 Special Topics: Nomenclature page 4 of 8 6. Two ways to designate charge or oxidation number (a) Stock system: use a Roman numeral in parentheses to indicate the oxidation # of metal (b) Ewens-Bassett system: 1 use an Arabic numeral in parentheses (with a + or -) indicating the overall charge of a complex. Numbers are written as (2+), (3-), (1+), etc. Here s a statement from Inorganic Chemical Nomenclature by B.P. Block, W. H. Powell, and W. C. Fernelius (ACS Reference book, 1990), pg 40-41, The use in the Stock system of 0 for an oxidation number of zero (because there is no Roman numeral for zero) precludes the use of 0 as a Ewens-Basset number for neutral coordination entities. Normally this causes no confusion. So...? If a complex has no overall charge, don t use the EB system! In either case, if the complex is negative, add "-ate" to the name of the coordination sphere. EX. [Pt(NH 3 ) 4 ] 2+ [PtCl 4 ] 2- [PtCl 6 ] 2- [Re 2 Cl 8 ] 2-7. cis- and trans- prefixes designate adjacent or opposite geometric locations EX. [PtCl 2 (NH 3 ) 2 ] [CoCl 2 (NH 3 ) 4 ] + 1 This footnote comes from a journal article (Kauffman, G. B.; Jørgensen, C. K.; J. Chem. Ed. 1985, 62, ) probing the history of the E-B system. Ronald Victor George Ewens was born in 1913, was educated at Queen Elizabeth's Hospital, Bristol, and received his doctorate in 1938 from Lincoln College, Oxford University as a pupil of Nevil Vincent Sidgwick. After a year's investigation of the inhibition of fermentation and glycolysis by snake venom at the Sir William Dunn School of Pathology, Oxford, he became Demonstrator and later (1948) Reader in chemistry at Guy's Hospital Medical School. His primary research interest was metal carbonyls and nitrosyls. As Bassett told Fernelius, the 35-year-old Ewens committed suicide by throwing himself in front of a subway train on September 21, 1948, in the year preceding the publication of the paper. He left behind a widow and a young daughter. Henry Bassett ( ). PhD. Munich; DSc, London; was Assistant Lecturer, Liverpool University; Professor and Head of the Department of Chemistry, University College, Reading and Reading University; and Emeritus Fellow, University College, London. He was primarily interested in double salts and solid ammoniates and was the author of "Theory of Qualitative Analysis" and "Chemical Laboratory for Beginners".

5 CHM 511 Special Topics: Nomenclature page 5 of 8 8. fac- and mer- prefixes used for MX 3 Y 3 octahedral complexes EX. [Co(NO 2 ) 3 (NH 3 ) 3 ] 9. Bridging ligands between two metal centers have the prefix (mu) EX. [(NH 3 ) 5 Cr-O-Cr(NH 3 ) 5 ] 4+ EX. [(NH 3 ) 4 Co(-OH-) 2 Co(NH 3 ) 4 ] 4+ EX. [(NH 3 ) 4 Co(-NH 2 -)(-OH-)Co(NH 3 ) 4 ] 4+ What is the formula of tri-μ-iodo-bis(tricarbonylrhenium)?

6 CHM 511 Special Topics: Nomenclature page 6 of When the complex is negatively charged, a Latin name for the element is often used, but not always (see highlighted section). Otherwise, use this list. iron silver antimony lead tin gold copper tungsten ferrate argentate stibate plumbate stannate aurate cuprate tungstate mercury scandium titanium chromium manganese cobalt nickel zirconium mercurate scandate titanate chromate manganate cobaltate nickelate zirconate niobium niobate ruthenium ruthenate rhodium rhodate palladium palladate rhenium rhenate molybdenum molybdate tantalum tantalate platinum platinate EX. K 3 [Fe(CN) 6 ] EX. Na[AgCl 2 ] Chelating ligands Chelate: a complex in which a polydentate ligand forms a ring that includes the metal atom EX. [Co(ox)(OH 2 ) 4 ] + This can sometimes lead to strain and can distort an octahedral complex. Measure the ligand's "bite angle". Other polydentate ligands you recall (perhaps from CHEM 321?)

7 CHM 511 Special Topics: Nomenclature page 7 of 8 Chirality A chiral complex is not superimposable on its own mirror image. Two mirror images = enantiomeric pair How to determine if something is achiral: look for a mirror plane look for a center of inversion EX. trans-[fecl 2 (OH 2 ) 4 ] trans-[cocl(en) 2 (OH 2 )] 2+ cis-[cocl 2 (en) 2 ] + [Cr(edta)] - [Ru(bipy) 3 ] 2+ [PtCl(dien)] + (dien = diethylenetriamine)

8 CHM 511 Special Topics: Nomenclature page 8 of 8 Designations of chiral O h complexes Instead of R and S designations, use and (delta and lambda) Original designation viewed rotation through a 3-fold axis, but see article attached for easier method. See article from Journal of Chemical Education 72(12) 1995, EX. [Co(en)] 3+ can occur with two non-superimposable mirror images