Nickel complex bond length

Di- x-bromobis[diethylenethioureatellurium(II)] dibromide, 35 294-295 Dibromobis(phosphine)nickel(Il) complex, bond length changes in spin state transition, 32 6... 

The force constants of the Ni—P bond in P " nickel carbonyl complexes increase in the order MeaP < PHg < P(OMe)a < PFs. This order is different from that of the donor-acceptor character, as estimated from uco-The lengthening of the P—O bond of triphenylphosphine oxide upon complexation with uranium oxide has been estimated by i.r. spectroscopy. However, A -ray diffraction shows little difference in the P-O bond lengths (see Section 7). Some SCF-MO calculations on the donor-acceptor properties of McaPO and H3PO have been reported. 

The orange, air-stable, homoleptic tetrakis( 71-phosphabenzene)nickel (1046) is tetrahedral (point symmetry 54) and can be obtained from phosphabenzene and [Ni(cod)2].2 25 It features a short Ni—P bond length of 2.1274(5) A with considerable N i P 7r-backbonding and a i/(Ni—P) stretch at 168 cm-1. In solution, partial dissociation of one phosphabenzene ligand is observed. 2-Diphenylphosphino-3-methylphosphinine forms with [Ni(cod)2] in the presence of the CO the dinuclear complex (1047) with a W-frame structure.2526... 

A remarkably stable, deep red Ni° stannylene complex, [Ni(1068)4l, has been prepared by the reaction of [Ni(l,5-cyclooctadiene)2] with (1068) in toluene at —78 °C. 70 In spite of the bulkiness of (1068) and the known tendency of analogous Ni° phosphine complexes to dissociate in solution, [Ni(1068)4] remains intact in solution and, moreover, melts at 178-180 °C without decomposition. X-ray crystallography shows tetrahedral geometry about the nickel atom, with Ni—Sn bond lengths of 2.3898(2)-2.399(2) A. 

Fig. 17 Optimized geometries at BP86/SVP of the nickel complexes N-Ni(CO)3 (N = 1-9). Experimental values are given in italics. Bond lengths in A, angles in degrees. Hydrogen atoms of the phenyl rings are omitted for clarity. Experimental values from X-ray analysis taken from [107]. Experimental values from X-ray analysis of a substituted analog taken from [111]...

Mean cobalt-cobalt and nickel-nickel distances observed in these complexes are very close to interatomic distances determined at ambient temperatures in cobalt and nickel metals (Co-Co 2.489(7) A vs. 2.507 A in a-cobalt (33) Ni-Ni 2.469(6) A vs. 2.492 A in the metal (39)). The mean M-H bond lengths, as well as hydride displacements from M3 faces, are less for nickel in H3Ni4(Cp)4 than for cobalt in HFeCo3(CO)9(P(OMe)3)3. Although the differences are marginally significant within error limits (Ni-H 1.691(8) A vs. Co-H 1.734(4) A displacements from plane Ni3 0.90(3) A vs. Co3 0.978(3) A), they are in the expected direction since the covalent radius should vary inversely with atomic number within a transition series. However, other effects such as the number of electrons in the cluster also can influence these dimensions. 

The answers to these questions and other questions about the transition-metal complexes have been provided by a new idea about their structure, developed in 1935 to account for the bond lengths observed in the nickel tetracarbonyl molecule. This idea is that atoms of the transition groups are not restricted to the formation of single covalent bonds, but can form multiple covalent bonds with electron-accepting ligands by making use of the 3d (or 4d, 5d) orbitals and electrons of the transition metal. 

Both the C—C bond lengths [(I) - 149.7 pm (2) = 147.6 pm] and the bending of the substituents out of the plane [(11 = 32.2° (2) = 38.4°] are nearly the same. Although we can draw an alternative resonance form for the nickel complex, the bonding model shown is the only one applicable to Ihe oxide. In view of the strong structural similarities, we can feel justified in using the cyclic structure us nn approximation for certain complexes as welL... 

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