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An examination of several catalytic reactions among the group 15 elements is presented. The connections between the chemistry of the pnictogens can sometimes be challenging, but aspects of metal–pnictogen reactivity are the key. The connecting reactivity comes from metal-catalyzed transformations such as dehydrocoupling and hydrofunctionalization. Pivotal mechanistic insights from E–N heterodehydrocoupling have informed the development of highly active catalysts for these reactions. Metal–amido nucleophilicity is often at the core of this reactivity, which diverges from phosphine and arsine dehydrocoupling. Nucleophilicity connects to the earliest understanding of hydrophosphination catalysis, but more recent catalysts are leveraging enhanced insertion activity through photolysis. This photocatalysis extends to hydroarsination, which may also have more metal–arsenido nucleophilicity than anticipated. However, metal-catalyzed arsinidene chemistry foreshadowed related phosphinidene chemistry by years. This examination shows the potential for greater influence of individual discoveries and understanding to leverage new advances between these elements, and it also suggests that the chemistry of heavier elements may have more influence on what is possible with lighter elements. [ABSTRACT FROM AUTHOR]

Chromium-bearing tourmalines are rare. Chromium-rich tourmaline from the northwestern part of the Adirondack Mountains in the Adirondack Lowlands is among the most chromium-rich tourmalines found to date. The mineral, with >21.0 wt. % Cr2O3, is from the marble-hosted talc–tremolite–cummingtonite schist in the #1 mine in Balmat, St. Lawrence County, New York. The atomic arrangement of the sample (a = 16.0242(3) Å, c = 7.3002(2) Å) was refined to R1 = 0.0139. The composition, from chemical analyses and optimization of the formula, is X(Ca0.22Na0.69K0.01) Y(Cr3+1.68Mg0.80Ti0.13V0.06Mn0.02Fe0.02Li0.29) Z(Al3.11Cr3+1.18Mg1.70Fe0.01) T(Si5.93Al0.07) B3O27 OH3.99 F0.01. There has been extensive debate over the ordering of Cr3+ between the tourmaline Y and Z octahedral sites. Recent work has suggested that, at low concentrations (<~1.03 apfu), the substituent Cr3+ is ordered into the Y-site, whereas, at greater concentrations, the substituent is disordered over both octahedral sites. An analysis of nine recently published, high-precision structures of chromium-bearing tourmaline, in combination with the Adirondack tourmaline, suggests that structural changes to the Y-site at low concentrations of Cr3+ induce changes in the Z-site that make it more amenable to incorporation of the Cr3+ substituents by increasing . The bond lengths change to lower the bond-valence sum of Cr3+ in the Z-site of the chromium-dravite, making that site more amenable to the substituent. Calculations suggest that the Z-site begins to accept substituent Cr3+ when the bond valence sum of that ion in Z reduces to a value of ~3.36 valence units. [ABSTRACT FROM AUTHOR]