TY - JOUR
T1 - Extended metal atom chains (EMACs) of five chromium or cobalt atoms
T2 - Symmetrical or unsymmetrical?
AU - Berry, John F.
AU - Cotton, F. Albert
AU - Fewox, Christopher S.
AU - Lu, Tongbu
AU - Murillo, Carlos A.
AU - Wang, Xiaoping
PY - 2004/8/7
Y1 - 2004/8/7
N2 - Structural studies of pentachromium and pentacobalt extended metal atom chain (EMAC) systems are presented in which the metal chains are helically wrapped by either the pentadentate dianion tripyridyldiamide (tpda) or its diethyl-substituted analogue bis(4-ethyl-2-pyridylamido)pyridine (etpda). The compound Cr5(tpda)4(NCS)2, (1) has alternating long and short Cr-Cr distances, contrary to recent reports that describe it as symmetrical with essentially equally spaced chromium atoms (Eur. J. Inorg. Chem., 1999, 1243; J. Phys. Chem. B, 2004, 108, 959). The linear Cr 510+ chain is composed of two Cr24+ quadruply bonded units and an isolated high spin CrII unit. The new compounds Cr5(etpda)4Cl2 (2), [Cr 5(etpda)4FCl]PF6 (3), and Co 5(etpda)4(NCS)2 (4) employ the etpda ligand as "insulation" around a central pentametal-atom "wire." Compound 3, like all other oxidized pentachromium compounds, has very disparate alternating short-long-short-long Cr-Cr distances, 2.032(3) Å, 2.560(6) Å, 1.873(5) Å, and 2.509(4) Å. Compound 4 shows a nearly uniform spacing of the Co atoms, although the outer Co-Co distances (2.279[4] Å) are slightly longer than the inner ones (2.239[4] Å).
AB - Structural studies of pentachromium and pentacobalt extended metal atom chain (EMAC) systems are presented in which the metal chains are helically wrapped by either the pentadentate dianion tripyridyldiamide (tpda) or its diethyl-substituted analogue bis(4-ethyl-2-pyridylamido)pyridine (etpda). The compound Cr5(tpda)4(NCS)2, (1) has alternating long and short Cr-Cr distances, contrary to recent reports that describe it as symmetrical with essentially equally spaced chromium atoms (Eur. J. Inorg. Chem., 1999, 1243; J. Phys. Chem. B, 2004, 108, 959). The linear Cr 510+ chain is composed of two Cr24+ quadruply bonded units and an isolated high spin CrII unit. The new compounds Cr5(etpda)4Cl2 (2), [Cr 5(etpda)4FCl]PF6 (3), and Co 5(etpda)4(NCS)2 (4) employ the etpda ligand as "insulation" around a central pentametal-atom "wire." Compound 3, like all other oxidized pentachromium compounds, has very disparate alternating short-long-short-long Cr-Cr distances, 2.032(3) Å, 2.560(6) Å, 1.873(5) Å, and 2.509(4) Å. Compound 4 shows a nearly uniform spacing of the Co atoms, although the outer Co-Co distances (2.279[4] Å) are slightly longer than the inner ones (2.239[4] Å).
UR - http://www.scopus.com/inward/record.url?scp=4344675332&partnerID=8YFLogxK
U2 - 10.1039/b405629a
DO - 10.1039/b405629a
M3 - Article
AN - SCOPUS:4344675332
SN - 1477-9226
SP - 2297
EP - 2302
JO - Dalton Transactions
JF - Dalton Transactions
IS - 15
ER -