# Main Group Elements as Transition Metals: Alkaline Earth Octacarbonyls with 18-electrons

Generally, main group elements prefer obeying the 8-electron rule; while the transition metal elements tend to follow the 18-electron rule. Recently, scientists reported the isolation and spectroscopic identification of the eight-coordinated alkaline earth carbonyl complexes M(CO)8 (M = Ca, Sr, Ba) in a low-temperature matrix, which unexpectedly obey the 18-electron rule.

In their recently published Science paper, Xuan Wu et al. used scalar relativistic ADF calculations with EDA-NOCV analysis to show that the metal-CO bonds are mainly due to [M(dπ)]→(CO)8 π backdonation, which explains the strong red-shift of the C-O stretching frequencies. The complexes M(CO)8 exhibit typical features of transition metal complexes obeying the 18-electron rule.

Try it yourself: Request inputfiles

Xuan Wu, Lili Zhao, Jiaye Jin, Sudip Pan, Wei Li, Xiaoyang Jin, Guanjun Wang, Mingfei Zhou, Gernot Frenking, Observation of alkaline earth complexes M(CO)8 (M = Ca, Sr, or Ba) that mimic transition metals, Science 321, 912-916 (2018)
{"extraction_info": {"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.8316263556480408, "perplexity": 23799.799999522584}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2019-18/segments/1555578650225.76/warc/CC-MAIN-20190424154437-20190424180437-00125.warc.gz"}