Exceptional thermal stability and high volatility in mid to late first row transition metal complexes containing carbohydrazide ligands

Geometry and Spin Change at the Heart of a Cobalt(II) Complex: A Special Case of Solvatomorphism

“…Both CoÀOand CoÀNbond lengths in 1-green are significantly longert han those found in square-planar cobalt(II) (LS) complexes of triazene1 -oxide ligands (compound 5,T able 1) and o-aminophenol-redox-active-type ligands( compound 6, Ta ble 1). The CoÀOb ond length in 1-green is also comparable with those found in cobalt complexes of a-imino alkoxide- [5] and carbohydrazide-type [17] ligands (compounds 7 and 8, Ta ble 1), whereas the CoÀNb ond is longer in 1-green versus 7 and 8.I n1-orange,t he mean CoÀOb ond length (1.951 (7) ) is similar to the corresponding values reported for tetrahedral (HS) cobalt(II) complexes of fluorinated alkoxide ligands [14a] (1.952(3) ), and a-iminoketone-type ligands (compound 10, Ta ble 1). The mean CoÀNbondlength 1.989(8) isc omparable to those found in tetrahedral cobalt complexes of triazene 1-oxide ligands [6] (compound 9,T able1)a nd b-ketoaminato ligands [18] (compound 11,T able 1).…”

“…The CoO and CoN bond lengths are longer by 0.11(1) and 0.09(1) Å in 1‐orange (tetrahedral) versus 1‐green (square planar), as was expected based on crystal‐ and ligand‐field theory 19. This point is also reflected in the expansion of the O‐ N ‐C angle in 1‐orange (119.5(8)°) versus 1‐green (115.7(1)°), but not in the value of the endocyclic O‐Co‐N angle (84.3(3)°), which is identical in both forms of 1 17. The tightening of this angle with respect to the ideal values is imposed by the strain of the five‐membered chelate ring.…”

“…[f] Compound 7 : Co(L) 2 , L= α ‐imino alkoxide‐type (GIFJIQ) 5. [g] Compound 8 : Co(L) 2 , L=carbohydrazide‐type (DOBYEA) 17. [h] Compound 9 : Co(L) 2 , L=triazene 1‐oxide‐type (YANWOZ) 6.…”

“…[19] This point is also reflected in the expansion of the O-N-C angle in 1-orange (119.5(8)8) versus 1-green (115.7(1)8), butn ot in the value of the endocyclic O-Co-Na ngle (84.3(3)8), which is identical in both forms of 1. [17] The tightening of this angle with respect to the ideal values is imposed by the strain of the five-membered chelate ring. For 1-green,e xamination of the interactions between the two co-crystallized CH 2 Cl 2 molecules and 1 (Figure 3) shows that the CH 2 Cl 2 protons (of as ame molecule) participate in hydrogen bonding:o ne CH 2 Cl 2 proton interacts with one Oa tom from the metal chelate ring (O1···HÀCHCl 2 (d = 2.26 , D = 3.24 , q = 1738), O2···HÀCHCl 2 (d = 2.22 , D = 3.19 , q = 1658), whereas the other CH 2 Cl 2 proton is implicated in aH ···pC(sp 2 )t ype weak interaction (d = 2.6-2.8 ).…”

“…[5] [g] Compound 8:C o(L) 2 ,L=carbohydrazide-type (DOBYEA). [17] [h] Compound 9:C o(L) 2 ,L=triazene 1-oxide-type (YANWOZ). [6] [i]Compound 10:C o(L) 2 ,L=a -iminoketone-type (YIPHIP).…”