Hydrolysis of the triethyl-and triphenyl-germyl complexes, R,Ge*PPh,, gives (R,Ge),O and Ph,PH, whilst oxidation cleaves the Ge-P bond forming R,Ge-O-P(O)Ph,. Other reagents which cleave the Ge-P bond are bromine, methyl iodide, and butyl-and phenyl-lithium. Silver iodide gives the coordination complex, [(Et,Ge*PPh,) AgI],. PhGeBr, and GeCl, react differently with lithium diphenylphosphide (or Ph,PH + Et,N) giving tetraphenyldiphosphine and water-stable polymeric diphenylphosphinogermanes.IN a preliminary Communication we reported the formation and some chemical reactions of diphenyl(triethylgennyl)phosphorus, Et,Ge*PPh,, as the first example of an organogermane containing germanium bonded to phosphorus. This Paper is concerned with these and further studies on related compounds.Organic derivatives of all the Group IV metals are now known to form covalent bonds to phosphorus : each element (M = Si,, Ge, Sn,, Pb 4, forms complexes of the type R,M*PR', and R,M(PR',),, for which three general preparative methods are available: (R,MLi + R',PCl), (R,MCl + R',PLi), and (R,MCl + R',PH + Et,N). With the exception of lead, the complexes show considerable thermal stability. Each type is readily oxidised to R,M*O*P(O)R',, and hydrolysed to (R,M),O + R',PH. Both silicon and tin have yielded the tetrakis derivatives, (Et,P),Si and (Ph,P),Sn. Extensive studies on tin-phosphorus compounds have revealed some surprising complexities, for example the reaction R,SnLi