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

Abstract

The homoleptic 1,3-diphosphacyclobutadiene sandwich complex [Co(h 4 -1,3-P 2 C 2 tBu 2 ) 2 ] À behaved as av ersatile and highly flexible metalloligand toward Ni 2 + ,R u 2 + , Rh + ,a nd Pd 2 + cations, formingarange of unusual oligonuclear compounds. 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. The structure of 3 contains an unprecedented 1,4-diphospha-2-nickelacyclopentadiene moiety formed by an oxidative addition of al igand PÀCb ond onto nickel. At elevated temperatures, 3 isomerized to [Co(h 4 -CpNi{1,4-P 2 C 2 tBu 2 -k 2 P, P })(h 4 -1,3-P 2 C 2 tBu 2 )] (4), which features a1 ,3-diphospha-2-nickelacyclopentadiene unit. Transmetalation of [K(thf) 2 {Co(h 4 -1,3-P 2 C 2 tBu 2 ) 2 }] with [Cp*RuCl] 4 (Cp* = C 5 Me 5 )a fforded tetranuclear[ (Cp*Ru) 3 (m-Cl) 2 {Co(h 4 -1,3-P 2 C 2 tBu 2 ) 2 }] (5), in which the [Co(h 4 -1,3-P 2 C 2 tBu 2 ] À aniona cts as ac helate ligand toward Ru 2 + .T he diphosphido complex [(Cp*Ru) 2 (m,h 2 -P 2 )(m,h 2 -C 2 tBu 2 )] (6)w as formed as ab yproduct. Pure compound 6 was isolated after prolonged heating of the reaction mixture. The reaction of [K(thf) 2 {Co(h 4 -1,3-P 2 C 2 R 2 ) 2 }] (R = tBu;a damantyl, Ad) with [RhCl(cod)] 2 (cod = 1,5-cyclooctadiene) afforded unprecedented p-complexes [Rh(cod){Co(h 4 -1,3-P 2 C 2 R 2 ) 2 }] (7:R = tBu; 8:R= Ad), in which one m:h 4 :h 4 -P 2 C 2 R 2 ligand bridges two metal atoms.T he pentanuclear complex [Pd 3 (PPh 3 ) 2 {Co(h 4 -1,3-P 2 C 2 tBu 2 ) 2 } 2 ]( 10), featuring aP d 3 chain andarare 1,4-diphospha-2-butene ligand,w as synthesized by reacting [K(thf) 2 {Co(h 4 -1,3-P 2 C 2 tBu 2 ) 2 }] with cis-PdCl 2 (PPh 3 ) 2 .T he redox properties of selected compounds were analyzed by cyclic voltammetry, whereas DFT calculations gave additional insighti ntot he electronic structures.The results of this study revealed several remarkable and previously unrecognized properties of the [Co(P 2 C 2 tBu 2 ) 2 ] À anion.Scheme1.Synthesis of complexes of type A. [7] [a] C. Rçdl,P rof. Dr.R.W olf

Low-oxidation state cobalt–magnesium complexes: ion-pairing and reactivity

“…This is the second example of such an insertion, the first being (Cp*NiP 2 C 2 tBu 2 )Co(P 2 C 2 tBu 2 ) (H) synthesised from the reaction of [K(THF) 2 {Co(P 2 C 2 tBu 2 ) 2 }] with [Ni 2 Cp 3 ]BF 4 . 22 The Ni-C and Ni-P bonds lengths are within the range expected for a single bond (1.9269(14) and 2.2051(4) Å, respectively) and the similar P1-C1, C1-P2 and P2-C6 bond lengths indicates delocalisation (1.7388(15), 1.7663( 14) and 1.7625( 14) Å, respectively). The Ni-Co bond length is slightly shorter when compared to that found in H (2.5065(3) vs. 2.536(1) Å, respectively) assumedly due to the less bulky COD ligand present in 7.…”

“…This is the second example of such an insertion, the first being (Cp*NiP 2 C 2 t Bu 2 )Co(P 2 C 2 t Bu 2 ) ( H ) synthesised from the reaction of [K(THF) 2 {Co(P 2 C 2 t Bu 2 ) 2 }] with [Ni 2 Cp 3 ]BF 4 . 22 …”

Activation of Di‐tert‐butyldiphosphatetrahedrane: Access to (tBuCP)n (n=2, 4) Ligand Frameworks by P−C Bond Cleavage

“…The formation of 5 involves the elimination of di‐ tert ‐butylacetylene, which was identified by the 13 C{ 1 H} NMR resonance of the alkyne carbon atom detected at a chemical shift of 87.5 ppm. A related example of t BuC≡C t Bu elimination from a metal complex was recently reported by our group from a ruthenium complex, [17] but in contrast to that example, where the alkyne remains as η 2 ‐bound ligand in the coordination sphere of ruthenium, di‐ tert ‐butylacetylene was completely liberated in the reaction reported herein, which illustrates an exciting potential for 1 and its coordination compounds to act as a source of P 2 units.…”

Zugang zu (tBuCP)n‐Gerüsten (n=2, 4) durch P‐C‐Bindungsspaltung von Di‐tert‐butyldiphosphatetrahedran

“…Verbindung 4 konnte in 28 % Ausbeute als kristalline Verbindung isoliert werden. Die 1 H-und 13 [17] Allerdings und im Gegensatz zu diesem Beispiel, in dem das Alkin als Ligand in der Koordinationssphäre des Rutheniums verbleibt, wird Di-tert-butylacetylen im hier beschriebenen Fall vollständig freigesetzt. Diese Tatsache veranschaulicht das Potential von 1 und dessen Koordinationsverbindungen als Quelle für P 2 -Einheiten.…”

“…Diese erfolgt unter Eliminierung von Di‐ tert ‐butylacetylen, welches anhand seines 13 C{ 1 H}‐NMR‐Signals bei einer chemischen Verschiebung von 87.5 ppm identifiziert wurde. Ein ähnliches Beispiel für die Eliminierung von t BuC≡C t Bu aus einem Metallkomplex wurde kürzlich von unserer Gruppe mit einem Rutheniumkomplex beschrieben [17] . Allerdings und im Gegensatz zu diesem Beispiel, in dem das Alkin als Ligand in der Koordinationssphäre des Rutheniums verbleibt, wird Di‐ tert ‐butylacetylen im hier beschriebenen Fall vollständig freigesetzt.…”