Cobalt(I) and Nickel(II) Complexes of Bis(1,3‐diphosphacyclobutadiene) Sandwich Anions

Abstract

Complexes [(C 4 Me 4 )Co(CO) 2 {Co(P 2 C 2 tBu 2 ) 2 }](1, C 4 Me 4 = tetramethylcyclobutadiene) and [CpNi{Co(P 2 C 2 tBu 2 ) 2 }-(PPh 3 )] (2, Cp = cyclopentadienyl) were synthesized by transmetalating [Tl(thf ) 2 {Co(P 2 C 2 tBu 2 ) 2 }] with [(C 4 Me 4 )Co(CO) 2 I] and [CpNiBr(PPh 3 )]. Compounds 1 and 2 were fully characterized by X-ray crystallography, multinuclear NMR, UV/Vis, and IR spectroscopy, and elemental analysis. Their molecular structures show σ-coordination of one phosphorus atom of the [Co(P 2 C 2 tBu 2 ) 2 ]anion to the second metal atom (cobalt or nickel). Time-dependent density functional theory (TD-DFT) calculations were [a]

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

“…The Ni1ÀP1 distance is shorter than in E (2.1807(8)i n2 vs. 2.2022(5) in E). [10] Similar to E, the coordinated P 2 C 2 ligandsa re slightly tilted as ar esulto f metal coordination;t he dihedrala ngle betweent he P1C1P2C2/P3C3P4C4p lanes in 2 is 6.098 compared with 11.358 in [CpNi{Co(P 2 C 2 tBu 2 ) 2 }(PPh 3 )].…”

“…The 31 P{ 1 H} NMR spectrum of crystalline 2 (recorded in [D 8 ]THF at 233 K) is similar to that of [CpNi-{Co(P 2 C 2 tBu 2 ) 2 }(PPh 3 )]. [10] Twod oubletsa td = À4.1 ( 2 J31 PÀ 31 P ) = 21.3 Hz) and d = 31.5 ppm ( 2 J31 PÀ 31 P = 21.3 Hz), were assigned to the Pa toms of the nickel-coordinated diphosphacyclobutadiene, whereas the second diphosphacyclobutadiene ligand gave rise to as inglet at d = 15.6 ppm. The complex [CpNi-{Co(P 2 C 2 tBu 2 ) 2 }(PPh 3 )] is stable in solutiona ta mbient temperature, whereas 2 slowly transformed into 3 below 233 K, which prevented it from being isolated as ap ure compound.…”

“…Although 1 could not be isolated due to its low thermals tability,[ CpNi{Co(h 4 -1,3-P 2 C 2 tBu 2 ) 2 }(thf)] (2)w as isolated on a preparative scale and characterized by single-crystal X-ray crystallography.T he molecular structure (Figure2)i ss imilar to [CpNi{Co(P 2 C 2 tBu 2 ) 2 }(PPh 3 )] (E,s ee Figure 1, type B), previously prepared through as imilarr oute and described by us in ap reliminary communication. [10] The nickel atom is coordinated by one phosphorus atom of a[ Co(P 2 C 2 tBu 2 ) 2 ] À anion,acyclopentadienyll igand, and aT HF molecule, resulting in at wo-legged piano-stool environmentf or Ni1. The Ni1ÀP1 distance is shorter than in E (2.1807(8)i n2 vs. 2.2022(5) in E).…”

“…As triking result was the synthesis of the octanuclear molecular square [Au{Co(P 2 C 2 tBu 2 ) 2 ] 4 (D)c omposed of four [Co(P 2 C 2 tBu 2 ) 2 ] À molecules and four gold atoms. [10] Here, we give af ull account of our studies, which have revealed severaln ew and intriguing features of the coordination chemistry of diphosphacyclobutadiene sandwich anions. [10] Here, we give af ull account of our studies, which have revealed severaln ew and intriguing features of the coordination chemistry of diphosphacyclobutadiene sandwich anions.…”

“…[9] To gain am ore comprehensive insight into the coordination chemistry of type A anions, we next decided to investigate the synthesis of metal complexes with cationsofG roups 8- 10. In ap revious preliminary communication, we reported the synthesis of nickel(II)a nd cobalt(I) complexes (see Figure 1, structure B)w ith s-coordinated CpNi(PPh 3 ) 3 and (C 4 Me 4 )Co(CO) 2 fragments. [10] Here, we give af ull account of our studies, which have revealed severaln ew and intriguing features of the coordination chemistry of diphosphacyclobutadiene sandwich anions. In particular,t hey show flexidentate coordination behavior demonstrated by the ability to act as a chelate ligand and to form p-complexes.…”