Issue 9, 2010

Terminal versus bridging cyclobutadiene rings in binuclear nickel carbonyl derivatives: A cube-antiprism twist of the cyclobutadiene rings in the perpendicular structures

Abstract

Cyclobutadienenickel derivatives are accessible from reactions of dichlorocyclobutenes with nickel carbonyl. In this connection the binuclear cyclobutadiene–nickel carbonyls (C4H4)2Ni2(CO)n (n = 3, 2, 1) have been examined theoretically as possible sources of new dimetallocene structures and new structures with metal–metal multiple bonds. The lowest energy (C4H4)2Ni2(CO) isomer is predicted to have a perpendicular structure with two bridging C4H4 rings forming an elongated square antiprism enclosing the pair of nickel atoms. The Ni[triple bond, length as m-dash]Ni distance of ∼2.25 Å corresponds to the formal triple bond required to give both nickel atoms the favored 18-electron configuration, with all eight carbon atoms of the two C4H4 rings involved in M–C bonding. A related low energy structure is found for (C4H4)2Ni2(CO)2 except that the two bridging C4H4 rings form an elongated cube enclosing a pair of nickel atoms at a somewhat longer bonding distance (∼2.33 Å). In this case only a Ni[double bond, length as m-dash]Ni double bond is required to give both nickel atoms the 18-electron configuration. Other low energy (C4H4)2Ni2(CO)n (n = 1, 2, 3) structures include a monocarbonyl (η4-C4H4)2Ni22-μ-CO) with a four-electron donor bridging carbonyl group, a coaxial doubly bridged dicarbonyl (η4-C4H4)2Ni2(μ-CO)2, and cis and trans isomers of a bent singly bridged tricarbonyl (η4-C4H4)2Ni2(CO)2(μ-CO).

Graphical abstract: Terminal versus bridging cyclobutadiene rings in binuclear nickel carbonyl derivatives: A cube-antiprism twist of the cyclobutadiene rings in the perpendicular structures

Supplementary files

Article information

Article type
Paper
Submitted
01 Dec 2009
Accepted
16 Mar 2010
First published
17 May 2010

New J. Chem., 2010,34, 1885-1892

Terminal versus bridging cyclobutadiene rings in binuclear nickel carbonyl derivatives: A cube-antiprism twist of the cyclobutadiene rings in the perpendicular structures

H. Wang, Z. Sun, Y. Xie, R. Bruce King and H. F. Schaefer III, New J. Chem., 2010, 34, 1885 DOI: 10.1039/B9NJ00721K

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