The Homoleptic Sandwich Anion [Co(P₂C₂tBu₂)₂]⁻: A Versatile Building Block for Phosphaorganometallic Chemistry

Abstract

A sandwich recipe: Treatment of the anthracene complex [Co(η4‐C14H10)2]− with tBuCP leads to the new diphosphacyclobutadiene sandwich anion 1, which can be converted into the unprecedented phosphaorganometallic complexes 2–4 upon treatment with different electrophiles (see scheme).

Iron–iron bonding versus iron–phosphorus bonding in binuclear diphosphacyclobutadiene iron carbonyl complexes

“…The recent discovery by Lammertsma and co-workers in 2008 of metal sandwich complexes of the diphosphacyclobutadiene ligands [4,6,7] makes of interest the structures and thermochemistry of related metal carbonyl derivatives. In this connection, the lowest energy (Me 2 C 2 P 2 ) 2 Fe 2 (CO) 5 structure is found to have one bridging g 1 ,g 4 -Me 2 C 2 P 2 ring as well as a terminal g 4 -Me 2 C 2 P 2 ring and an iron-iron distance of $4.3 Å far too long for a direct ironiron bond.…”

“…[5] This nickel sandwich has the favored 18-electron configuration and is particularly stable. More recently (2008) Lammertsma and coworkers have used the displacement of coordinated anthracene from the cobalt and iron [(g 4 -C 14 H 10 ) 2 M] À anions (M = Co, [6] Fe [7]) with four equivalents of Bu t C"P:to synthesize the anionic sandwich compounds [(g 4 -Bu t 2 C 2 P 2 ) 2 M] À . The corresponding neutral sandwich compounds (g 4 -Bu t 2 C 2 P 2 ) 2 M (M = Co, Fe) were then obtained by oxidation of these anions with (g 5 -C 5 H 5 ) 2 Fe + .…”

Flexidentate Coordination Behavior and Chemical Non‐Innocence of a Bis(1,3‐Diphosphacyclobutadiene) Sandwich Anion

“…Aiming at the synthesis of the hypothetical triple-decker complex [CpNi(m-P 2 C 2 tBu 2 )Co(P 2 C 2 tBu 2 )] (Cp = C 5 H 5 ), we began with the reaction of [K(thf) 2 {Co(P 2 C 2 tBu 2 ) 2 }] [7] with Werner's classic complex [Ni 2 Cp 3 ]BF 4…”

“…Althought he 1,2-isomer is more stable with small organic substituents, bulky groups such as R = tBu favor the formation of the 1,3isomer. [5,6] Our group developed anionic bis(1,3-diphosphacyclobutadiene) sandwich complexes [M(P 2 C 2 R 2 ) 2 ] À (M = Fe, Co;t ype A, Scheme1), [7] which were obtained from the reactiono fb is(an-thracene) metalates [M(h 4 -C 14 H 10 ) 2 ] À (M = Fe, Co;C 14 H 10 = anthracene) [8] with phosphaalkynes such as tBuÀCP, tPentÀCP, and AdÀCP( tBu = tert-butyl, tPent = tert-pentyl, Ad = adamantyl). [4] Since then, numerous 1,3diphosphacyclobutadiene complexes as well as some 1,2-diphosphacyclobutadiene complexes have been described.…”

“…[7] [a] C. Rçdl,P rof. The reactiono f[ K(thf) 2 {Co(h 4 -1,3-P 2 C 2 tBu 2 ) 2 }] with [Ni 2 Cp 3 ]BF 4 initially afforded the s-complex [CpNi{Co(h 4 -1,3-P 2 C 2 tBu 2 ) 2 }(thf)] (2), which converted into [Co(h 4 -CpNi{1,3-P 2 C 2 tBu 2 -kP,kC})(h 4 -1,3-P 2 C 2 tBu 2 )] (3)b elow room temperature.…”