Theoretical descriptions of novel triplet germylenes M1-Ge-M2-M3 (M1 = H, Li, Na, K; M2 = Be, Mg, Ca; M3 = H, F, Cl, Br).

In a quest to identify new ground-state triplet germylenes, the stabilities (singlet-triplet energy differences, ΔES-T) of 96 singlet (s) and triplet (t) M1-Ge-M2-M3 species were compared and contrasted at the B3LYP/6-311++G**, QCISD(T)/6-311++G**, and CCSD(T)/6-311++G** levels of theory (M1 = H, Li, Na, K; M2 = Be, Mg, Ca; M3 = H, F, Cl, Br). Interestingly, F-substituent triplet germylenes (M3 = F) appear to be more stable and linear than the corresponding Cl- or Br-substituent triplet germylenes (M3 = Cl or Br). Triplets with M1 = K (i.e., the K-Ge-M2-M3 series) seem to be more stable than the corresponding triplets with M1 = H, Li, or Na. This can be attributed to the higher electropositivity of potassium. Triplet species with M3 = Cl behave similarly to those with M3 = Br. Conversely, triplets with M3 = H show similar stabilities and linearities to those with M3 = F. Singlet species of formulae K-Ge-Ca-Cl and K-Ge-Ca-Br form unexpected cyclic structures. Finally, the triplet germylenes M1-Ge-M2-M3 become more stable as the electropositivities of the α-substituents (M1 and M2) and the electronegativity of the β-substituent (M3) increase.