A paramagnetic cobalt-SiH intermediate possessing the Co-(η(1)-H-Si) moiety was studied using various spectroscopic techniques. Frozen solution ENDOR experiments show a Co-H distance of ∼1.53 Å and a Si-Co-H angle of ∼15°, whereas XRD data suggest a TBP geometry about a Co(ii) centre. Its stepwise deprotonation with base followed by dehalogenation was identified experimentally and theoretically.