Electron-spin-resonance (ESR) spectroscopy of these molecules in argon matrices at 2 K reveals that each has a (4) Sigma ground electronic state, the same as TiV, also containing 9 valence (s+d) electrons. TiTa and ZrTa were not observed. An analogy can be drawn with the 15-valence-electron Brewer-Engel molecules VNi, VPd, VPt, NbNi, which also have (4) Sigma ground states and a ...sigma(1)d delta(2) configuration, where sigma is an sd sigma hybrid.