Synthesis and Structural Characterization of [Co{CN(2,6-C6H3Me2)}4]-, the First Transition Metal Isonitrilate

Abstract

The homoleptic Co(-I) isonitrile complex [Co(CNPh*)4]~(l-, Ph* = 2,6-C6H3Me2), the first example of an isonitrilate complex, can be prepared by ethylene substitution within the Co(-I) complex [Co(C2H4)4]~o r by potassium naphthalenide (K(Nap)) reduction of Co(0), Co(I), and Co(II) substrates. Reductions of the isonitrilecontaining precursors [Co(CNPh*)4I2] (3) and [Co(CNPh*)5]+ (4+) proceed via [Co2(CNPh*)8] (2), which is then reduced further to l-. Complex lcan be prepared in one pot by K(Nap) reduction of cobaltocene followed by addition of CNPh* or by potassium reduction of a mixture of CoI2 and CNPh* to give 2, which is then further reduced to 1~. The anion l-can be isolated as K+, [K(DME)]+, [K(crypt-2,2,2)]+, and [K(18-C-6)]+salts and has been characterized spectroscopically and analytically. Oxidation of 1~g ives 2, which is the only observable product from the reaction of 1" with many simple electrophiles. The only electrophilic adduct of 1~isolated to date is [Co(CNPh*)4(SnPh3)] ( 5), the product of reaction with Ph3SnCl. Single-crystal X-ray diffraction has confirmed that [K(DME)]1 contains discrete, approximately tetrahedral cobalt anions held together as loose dimers through interactions with the [K(DME) ]+ counterions (space group , with a = 11.160(2) A,b= 14.204(3) Á, c = 14.339(3) Á, a = 102.91(1)°, ß = 111.88(1)°, y = 102.78(1)°, Dc = 1.223 g/mL, Z = 2, and RF = 5.93%). Crystallography has also established that 2 is a dimer with two bridging isonitrile groups (space group , with a = 12.239(4) A, b = 13.985(4) A, c = 21.609(6) A, a = 98.87(2)°, ß = 99.19(2)°, y = 112.72(2)°, Dc = 1.185 g/mL, Z = 2, and RF = 6.10%), and examination of molecular parameters for land 2 suggest that increased back-donation of electron density from the metal results in significant lengthening of the C=N triple bond in 1~but has no consistent effect on the CNC bend angles of the ligands. Decreases in the CNC angles correlate instead with close approaches between the carbon atoms of the ligands and the [K(DME)]+ counterions, which are also responsible for the major distortions of the metal geometry away from that of an ideal tetrahedron.

Towards Homoleptic Naphthalenemetalates of the Later Transition Metals: Isolation and Characterization of Naphthalenecobaltates(1−)

“…Interestingly, analogous reactions that were conducted with cobaltocene as the Co II precursor also provided 1 in yields of about 85 %. Thus, both reactions may involve a common intermediate, perhaps a homoleptic naphthalenecobaltate(1−)11 that is analogous to the known bis(1,2,3,4‐η 4 ‐anthracene)cobaltate(1−) ( 2 ) 10…”

Bis(1,2,3,4-η4-anthracene)cobaltate(1−)

“…Although this substance is highly reactive towards a number of substrates, for example, it readily reacts with carbon monoxide at normal pressures and −60 °C° to produce [Co(CO) 4 ] − , all attempts to isolate this interesting species have so far failed 6. Interestingly, the reduction of cobaltocene by three equivalents of potassium naphthalene provided a similarly labile source of Co I− , which also defied isolation and characterization 7…”

“…All reactions proceeded completely within minutes at temperatures ≥−30 °C to provide the respective [CoL 4 ] − (L=CNXyl, P(OMe) 3 ) or [CoL 2 ] − (L=dppe or cot) in 75–92 % yields. While [Co(CNXyl) 4 ] − 7 and [Co(P(OMe) 3 ) 4 ] − 19 have been fully characterized previously, [Co(dppe) 2 ] − ( 3 ) has been only identified in solution by cyclic voltammetry,20 and [Co(cot) 2 ] − , 4 , is a new substance and the first homoleptic cot complex of cobalt. Single‐crystal X‐ray studies of 3 and 4 were carried out to confirm their natures.…”

The [M2(CO)8] Complexes of the Cobalt Group

“…In the D 2d isomer (1b), the axial ligands form angles of less than 90°with the equatorial plane, indicating the presence of a weak semibridging interaction (Co···C ϭ 2.83 Å and CoϪCoϪC ax ϭ 77.1°), similar to that observed in the optimized isoelectronic anion [Fe 2 (CO) 8 ] 2Ϫ (2.87 Å and 76°for the same parameters), [3] and in [Mn 2 (CO) 8 ] (2.74 Å and 82°). [58] We have found no D 2d structures for carbonyl complexes in the chemical literature, but D 2d structures have been proposed for the isoelectronic compounds [M 2 (PF 3 ) 8 ] (M ϭ [Co 2 (µ-CO) 2 (CO) 6 ] 2.536 193.6 FOHDEL04 [4,5] [Co 2 (µ-CO) 2 (CO) 6 ] 2.539 192.6 [Co 2 (µ-CNXyl) 2 (CNXyl) 6 ] 2.469 198.5 LIDVOJ [40] [Co 2 (µ-CNtBu) 2 (CNtBu) 6 ] 2.457 203.1 TBICCO10 [41] [Co 2 (µ-CO) 2 (CO) 4 (µ-dppa)] 2.457 205.6 PPACCP [42] [Co 2 (µ-CO) 2 (CO) 4 (µ-dmstb)] 2.471 207.8 PAYKUV [43] [Co 2 (µ-CO) 2 (CO) 4 (µ-dmars)] 2.482 200.5 FARSCO10 [44] [Co 2 (µ-CO) 2 (CO) 4 (dppe)] 2.541 188.4 BUVSIU [45] [Co 2 (µ-CO) 2 (CO) 4 (µ-dppbf)] 2.573 195.8 ROBKIC [46] [Co 2 (µ-CO) 2 (CO) 2 (µ-dppa) 2 ] 2.424 209.1 YEZMOF [47] [Co 2 (µ-CO) 2 (CO) 2 (µ-dppm) 2 ] 2.443 212.2 HANSUK [48] [Co 2 (µ-CO) 2 (CO) 2 (µ-deppm)] 2.513 203.7 VAKCEP [49] [Co 2 (µ-CO) 2 (CO) 4 (dppp)] 2.532 193.6 YAWMIS [50] [Co 2 (µ-CO) 2 (CO) 2 (dmpv) 2 ] 2.471 197.9 YIGXUH [51] [Rh 2 (µ-CO) 2 (CO) 3 (PPh 3 ) 3 ] 2.769 193.9 BOPLAT10 [52,53] [Rh 2 (µ-CO) 2 (CO) 2 (dppp) 2 ] 2.709 195.5 CEBBOA [54] [Rh 2 (µ-CO) 2 (CO) 2 [55] [Ir 2 (µ-CNXyl) 2 (CNXyl) 2 (µ-dmpm) 2 2.600 214.6 GEFNAG10 [56,57] [Ir 2 (µ-CNXyl{BH 3 }) 2 (CNXyl) 2 (µ-dmpm) 2 ] 2.589 216.2 KAXNIG [57] [a] Abbreviations: deppm ϭ bis(2-(diethylphosphanyl)ethylphenylphosphanyl)methane; dmars ϭ 1,2-bis(dimethylarsanyl)tetrafluorocyclobutene; dmpv ϭ dimethylphosphanylbenzenevanadium; dmstb ϭ bis(dimethylstibino)methane; dppa ϭ bis(diphenylphosphanyl)amine; dppbf ϭ 4,6-bis(diphenylphosphanyl)dibenzofuran; dppe ϭ 1,2-bis(diphenylphosphanyl)ethane; dppm ϭ bis(diphenylphosphanyl)methane; dppp ϭ 1,3-bis(diphenylphosphanyl)propane; triphos ϭ 1,1,1-tris(diphenylphosphanylmethyl)ethane.…”