Aqueous chemistry 

Different from the elements of the 3d series, 4d and 5d elements have slight simple aqueous cationic chemistry. The major exceptions are Y³⁺ and La³⁺, and Ag⁺ that creates some soluble salts (AgF, AgNO₃). The aqua Ag⁺ ion depicts strong class b complexing behavior, along with an affinity for ligands like NH₃, I^- and CN^- comparable with Cd²⁺ in the next group. Other aqua cations can be prepared, but they are widely hydrolyzed and polymerized (example Zr⁴⁺, Hf⁴⁺), strongly reducing (example Mo³⁺), or have a extremely high affinity for other ligands (example Pd²⁺) and are hard to prepare in uncomplexed form.

Table 1. A selection of oxides and halides of elements from the 4d and 5d series. M represents either of the two elements from the corresponding group, and X any halogen unless exceptions are specified.

Several complexes are, through, formed; the most stable with early groups being ones along with F^- and oxygen donor ligands and in afterwards groups ones with softer ligands like heavy halides and nitrogen donors. This tendency is identical to that found in the 3d series but is more marked. The most usually encountered solution species for later elements are chloride complexes like [PdCl₄]^2-, [PtCl₆]^4- and [AuCl₄]^-.

Oxoanions are created through elements of groups 5-8, instances being MoO^2-_4, ReO^-₄and RuO^2-₄ . They are always less strongly oxidizing than their counter-parts in the 3d series. Mo^VI andWVI, and to a lesser extent Nb^V and Ta^V, form wide series of polymeric oxoanions: isopolymetallates like [Mo₆O₁₉]^2- and [Ta₆O₁₉]^8- are mainly based on metal oxygen octahedra sharing edges and corners; heteropolymetallates like the phosphopolymolybdate ion [PMo₁₂O₄₀]^3- include other elements, in this example like a tetrahedral PO₄ group.Solid structures Larger ionic radii as compared with the 3d series elements frequently lead to higher coordination numbers. ZrO₂ and HfO₂ can take on the eight-coordinate fluorite structure with an exclusive seven-coordinate structure termed as baddeleyite (cf. TiO₂, rutile). Of a structure with six-coordination ReO₃ is the prototype, and is accepted also

(in little distorted form) through WO₃, in difference to Cr^VI, that is tetrahedral. MoO₃ and WO₃ form wide series of insertion compounds termed as oxide bronzes. In halides, higher coordination frequently leads to polymeric forms for compounds MX₄ and MX₅ in which the subsequent 3d compounds are molecular.

In low oxidation states compounds of elements extremely often have extensive metal-metal bonding. Occasionally this acts to alter an otherwise normal structure, like in NbO₂, MoO₂ and WO₂, that have the rutile form distorted through the formation of pairs of metal atoms. Frequently the structures are exclusive. For instance, MoCl₂ consist of [Mo₆Cl₈]⁴⁺ clusters formed through metal-metal bonded octahedral along with chlorine in the face positions. Complex halides frequently show metal-metal bonding, like in [Re₂Cl₈]²- (3) in which all four d electrons of ReIII are paired to create a quadruple bond.

Later elements are tends to depict coordination geometries that are particular to specific low-spin electron configurations. d⁶ compounds are always octahedral, d⁸ almost all the time square planar (example in PdCl₂ 4 and PdO; a uncommon exception is PdF₂ that like NiF₂, have the octahedral rutile structure along with two unpaired electrons per Pd). The d¹⁰ configuration frequently has a trend to linear two-coordination (cf. Hg^II, Topic G4). Even though AgF, AgCl and AgBr have the rocksalt structure another Ag^I compounds like Ag₂O contain two-coordination, and it is general for Au^I; for instance, AuCl has a chain structure along with a linear Cl-Au-Cl arrangement.