The reaction of FeBr2 and 1 equiv of thallium tris(4,4-dimethyl-2-oxazolinyl)phenylborate (TlTo(M)) in THF provides To(M)FeBr (1), whereas FeBr2 and 2 equiv of TlTo(M) react to give (To(M))(2)Fe (2). Two nu(CN) bands at 1604 and 1548 cm(-1) indicated bidentate coordination of To(M) to iron in 2. Homoleptic 2 and FeBr2 react in THF overnight through an unusual ligand exchange process to give compound 1, which is apparently the thermodynamic product. The salt metathesis reaction of 1 and KCH2Ph affords To(M)FeCH(2)Ph (3). The effective magnetic moments of compounds 1-3 range from 4.9 to 5.4 mu B, and these values are consistent with high-spin iron(II) (S = 2). A single H-1 NMR signal assigned to the methyl groups of the To(M) ligand suggested tridentate coordination of the To(M) ligand to iron in 1 and 3. X-ray crystallography studies of 1-3 establish their structure as four-coordinated tetrahedral iron complexes. To(M)FeBn and CO (1 atm) react to afford isolable To(M)Fe{C(=O)Bn}(CO)(2) (4) as a yellow solid. Complex 4 is diamagnetic (S = 0), and the three distinct methyl signals in the H-1 NMR spectrum are consistent with a six-coordinate, C-s-symmetric species. This assignment is supported by its IR spectrum, which revealed intense bands at 2004 and 1935 cm(-1) (symmetric and asymmetric nu(CO)), at 1680 and 1662 cm(-1) (acyl rotamers, nu(CO)), and at 1593 and 1553 cm(-1) (nu(CN)) and is confirmed by a single-crystal X-ray diffraction study.