( ( ( ( ( Properties ( of ( organometallic compounds ) ) ) , ) ( ( the nature ) ( of ( the ( carbon-metal bond ) ) ) ) ) , ) ( ( compounds ( of ( metals ( in ( ( ( ( ( ( groups 1 ) , ) ( 2 ( , ( 3 ( , ( and 4 ) ) ) ) ) ) , ) and ) ( transition metals ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (NP (NNP Properties)) (PP (IN of) (NP (JJ organometallic) (NNS compounds)))) (, ,) (NP (NP (DT the) (NN nature)) (PP (IN of) (NP (DT the) (JJ carbon-metal) (NN bond)))) (, ,)) (VP (VBZ compounds) (PP (IN of) (NP (NP (NNS metals)) (PP (IN in) (NP (NP (NNS groups) (CD 1)) (, ,) (NP (CD 2) (, ,) (CD 3) (, ,) (CC and) (CD 4)) (, ,) (CC and) (NP (NN transition) (NNS metals))))))) (. .)))
Properties of organometallic compounds, the nature of the carbon-metal bond, compounds of metals in groups  1, 2, 3, and 4, and transition metals.
(ROOT (S (NP (DT The) (JJ metallic) (NN bond)) (VP (VBZ is) (ADJP (JJ responsible) (PP (IN for) (NP (NP (DT the) (NNS properties)) (PP (IN of) (NP (NNS metals))))))) (. .)))