The amino acid derivatives of tungsten(0) [Et(4)N][W(CO)(4)(O2CCH2NH2)] (1), [Et(4)N][W(CO)(4)(O(2)CCH(2)NHMe)] (2), and [Et(4)N][W(CO)(4)(O(2)CCH(2)NMe(2))] (3) have been synthesized from the reaction of W(CO)(5)THF with the tetraethylammonium salt of the corresponding a-amino acid in a tetrahydrofuran solution. The glycine derivative, complex 1, is highly soluble in water. The complexes have been characterized in solution by infrared and NMR spectroscopies and in the solid state by X-ray crystallography. Complex 1 crystallized in the orthorhombic space group P2(1)2(1)2(1) with a = 10.108(14) Angstrom, b = 13.155(11) Angstrom, c = 13.657(10) Angstrom, V = 1870(3) Angstrom(3), and d(calc) = 1.731 g cm(-3), for Z = 4, from hexane/THF. Complex 2 crystallized in the monoclinic system, space group P2(1)/c, with a = 14.012(5) Angstrom, b = 10.335(2) Angstrom, c = 14.728(4) Angstrom, beta = 112.28(2)degrees, V = 1973.5(8) Angstrom(3), and d(calc)= 1.731 g cm(-3), for Z = 4, from hexane/THF. Complex 3 crystallized in the triclinic space group P $$($) over bar 1 with a = 11.586(5) Angstrom, b = 11.711(6) Angstrom, and c = 15.068(7) Angstrom, alpha = 90.01(4)degrees, beta = 96.28(4)degrees, gamma = 90.27(4)degrees, V = 2032(2) Angstrom(3), and d(calc) = 1.727 g cm(-3), for Z = 4, from a hexane-layered THF solution of 3. The geometry of the anion in each case is that of a slightly distorted octahedral arrangement of four carbonyl ligands and a puckered five-membered glycinate chelate ring. Complexes 1 and 2 exihibit intermolecular hydrogen-bonding interactions with N...O distances of 2.746 and 2.826 Angstrom, respectively. Weaker hydrogen-bonding interactions in solution with THF and CH3CN are noted as well. Although the coordination environments about the tungsten centers of the three glycinate derivatives are essentially the same, the CO lability is greatly enhanced in complexes 1 and 2 as compared to complex 3. This CO labilization in complexes 1 and 2 is attributed to a solvent-assisted removal of a proton from the amine ligand leading to a substitutionally labile amide transient species. Deprotonation of the amine ligand is aided by the pi-donation of the thus formed amide ligand to the coordinatively unsaturated metal center in the reactive intermediate.