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The synthesis and single-crystal X-ray characterization of [NH,][NMe,][V(hida),], (hida)3 -= oxyiminodiacetate,"] was important in the development of our understanding of the structure of amavadin (H,[V(S,S-hidpa),], ( h i d~a )~-= oxyimino-2,2'-dipropionate) ,[' I the form in which vanadium is accumulated in Amanita muscaria. We have confirmed the nature of isolated amavadin,13] which possesses a novel, eight-coordinate structure. Each ( h i d~a )~ -ligand binds to vanadium through two unidentate carboxylate groups and an q2-N,0 moiety; the two q2-N,0 groups are mutually trans and oriented at about 90" to one another. The relative orientations of the two q2-N,0 groups define the A and A isomers at the stereogenic metal center; amavadin as isolated contains an equal mixture of the two diastereoisomers, [d,A-V(S,S-hidpa),J2 -.[31 We have extended this chemistry to other early transition metals, including Mo,I4] Nb, and Ta.I5] Herein we report the synthesis and characterization of (hida)3-complexes of the Group 4 metals Ti and Zr, which further develops the coordination chemistry of the oxyiminodicarboxylate ligands.The complexes I and 2 have been prepared in situ in H,O, isolated as colorless crystals, and characterized by X-ray crystallography (Figures 1 and 2).I6l Each compound contains d and 2.083, Ti-N 2.075) are similar in length to the equivalent bonds of the V" complex (av. V-0, 2.067, V-N 2.003) and longer than those observed for the Vv complex (av. V-0,1.951, V-N 2.022), but the Ti-0, bond length of 1.943(4) 8, is shorter than that in either of these comparable complexes (V" av. 1.975 A, Vv av. 1.970 A; the other Ti-0 bond length is 1.975(5) A). The Zr" coordinates to two (hida)3-ligands in a manner similar to that of Ti" but with significantly longer bonds (Figure 2, av.Zr-O,2.239, Zr-N 2.227, Zr-0, 2.125 A). A water molecule (016) is also coordinated to the zirconium center and located in a plane between 0 5 and 0 6 ( Figure 2); consequently, the Zr'" center is nine-coordinate, a unique structural feature for this class of bis-ligand complexes with (hida)3-and ( h i d~a )~ -. If the amavadin-like coordination geometry is considered to be an octahedron in which a pair of trans vertices are occupied by the q2-N,0 groups, the extent of distortion from a regular geometry is related to the size of the metal. Thus, the dihedral angle between the two (q2-N,0)M groups increases, the trans angle 01-M-05 (for the carboxylate oxygen atoms of the same ligand) decreases, and the cis angle 05-M-06 (involving the carboxylate oxygen atoms of different ligands) increases as the size of the metal increases (see Table 1 and Figure 3). This increase in distortion ultimately leads to the ligation of an H,O molecule in the case of the Z f V ion. Figure 4 shows a space-filling diagram for [Ti(hida),]'-and [Zr(hida),(H,0)l2 -, illustrating the ligation of the H,O molecule between the two bonding carboxylate oxygen atoms. Nine-coordination is novel for Zr" in coordination chemistry, but coordination numbers higher than eight a...

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The reaction of N-hydroxy-2,2Ј-iminodipropionic acid with [PPh 4 ][ReOBr 4 ], [ReOCl 3 (PPh 3 ) 2 ], [ReOCl 2 (OEt)(PPh 3 ) 2 ] or [PPh 4 ][MoOCl 4 (H 2 O)] has produced four novel complexes: [ReOBr 3 (C 6 H 8 NO 5 )] Ϫ , [ReOBr 3 (C 3 H 3 NO 2 )] Ϫ , [ReOCl 2 (R,S-idpa)] Ϫ (H 3 idpa = 2,2Ј-iminodipropionic acid) and [MoO 2 Cl 2 (C 3 H 4 NO 3 )] Ϫ . All have been successfully crystallised as their [PPh 4 ] ϩ salts which have been characterised by single-crystal X-ray diffraction. The anions [ReOBr 3 (C 6 H 8 NO 5 )] Ϫ and [ReOBr 3 (C 3 H 3 NO 2 )] Ϫ involve tetragonally distorted octahedral Re V OBr 3 (N,O) centres with the bromides cis to the oxo-group; [ReOCl 2 (R,S-idpa)] Ϫ involves a tetragonally distorted octahedral Re V OCl 2 (O,N,O) centre with the 2Cl cis and O trans to the oxo-group; [MoO 2 Cl 2 (C 3 H 4 NO 3 )] Ϫ involves a skew-trapezoidal Mo VI O 2 Cl 2 (N,O) centre with essentially mutual cis oxo-groups and trans chloro-groups. The dimensions of each of these co-ordination spheres are generally typical of related complexes; however, [ReOBr 3 (C 3 H 3 NO 2 )] Ϫ involves an unusually short Re᎐O oxo bond of 1.45(4) Å. The organic moieties are considered to arise from rearrangement and/or fragmentation of N-hydroxy-2,2Ј-iminodipropionic acid, presumably under the influence of the metal centre.