hier das Minimalbeispiel
\documentclass[12pt]{article}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[ngerman]{babel}
\usepackage{chemfig}
\makeatletter
%Definition von Clemens auf der URL
\definearrow9{-X>}{%
\CF@arrow@shift@nodes{#7}%
\expandafter\draw\expandafter[\CF@arrow@current@style](\CF@arrow@start@node)--(\CF@arrow@end@node)node[midway](Xarrow@arctangent){};%
\CF@ifempty{#8}
{\def\CF@Xarrow@radius{0.333}}
{\def\CF@Xarrow@radius{#8}}%
\CF@ifempty{#9}%
{\def\CF@Xarrow@absangle{60}}
{\pgfmathsetmacro\CF@Xarrow@absangle{abs(#9)}}
% Draw top arrow (start)
\edef\CF@tmp@str{[\CF@ifempty{#1}{draw=none}{\unexpanded\expandafter{\CF@arrow@current@style}},-]}%
\expandafter\draw\CF@tmp@str (Xarrow@arctangent)%
arc[radius=\CF@compound@sep*\CF@current@arrow@length*\CF@Xarrow@radius,start angle=\CF@arrow@current@angle-90,delta angle=-\CF@Xarrow@absangle]node(Xarrow1@start){};
% Draw bottom arrow (end)
\edef\CF@tmp@str{[\CF@ifempty{#2}{draw=none}{\unexpanded\expandafter{\CF@arrow@current@style}},-CF]}%
\expandafter\draw\CF@tmp@str (Xarrow@arctangent)%
arc[radius=\CF@compound@sep*\CF@current@arrow@length*\CF@Xarrow@radius,%
start angle=\CF@arrow@current@angle-90,%
delta angle=\CF@Xarrow@absangle]%
node(Xarrow1@end){};
% Draw bottom arrow (start)
\edef\CF@tmp@str{[\CF@ifempty{#4}{draw=none}{\unexpanded\expandafter{\CF@arrow@current@style}},-]}%
\expandafter\draw\CF@tmp@str (Xarrow@arctangent)%
arc[radius=\CF@compound@sep*\CF@current@arrow@length*\CF@Xarrow@radius,start angle=\CF@arrow@current@angle+90,delta angle=\CF@Xarrow@absangle]node(Xarrow2@start){};
% Draw bottom arrow (end)
\edef\CF@tmp@str{[\CF@ifempty{#5}{draw=none}{\unexpanded\expandafter{\CF@arrow@current@style}},-CF]}%
\expandafter\draw\CF@tmp@str (Xarrow@arctangent)%
arc[radius=\CF@compound@sep*\CF@current@arrow@length*\CF@Xarrow@radius,%
start angle=\CF@arrow@current@angle+90,%
delta angle=-\CF@Xarrow@absangle]%
node(Xarrow2@end){};
% Insert labels
\pgfmathsetmacro\CF@tmp@stra{\CF@Xarrow@radius*cos(\CF@arrow@current@angle)<0?"-":"+"}%
\pgfmathsetmacro\CF@tmp@strb{\CF@Xarrow@radius*cos(\CF@arrow@current@angle)<0?"+":"-"}%
\ifdim\CF@Xarrow@radius pt>\z@
\CF@arrow@display@label{#1}{0}\CF@tmp@stra{Xarrow1@start}{#2}{1}\CF@tmp@stra{Xarrow1@end}%
\CF@arrow@display@label{#4}{0}\CF@tmp@strb{Xarrow2@start}{#5}{1}\CF@tmp@strb{Xarrow2@end}%
\CF@arrow@display@label{#3}{0.5}\CF@tmp@stra\CF@arrow@start@node{}{}{}\CF@arrow@end@node%
\CF@arrow@display@label{#6}{0.5}\CF@tmp@strb\CF@arrow@start@node{}{}{}\CF@arrow@end@node%
\else
\CF@arrow@display@label{#2}{0}\CF@tmp@stra{Xarrow1@start}{#1}{1}\CF@tmp@stra{Xarrow1@end}%
\CF@arrow@display@label{#5}{0}\CF@tmp@strb{Xarrow2@start}{#4}{1}\CF@tmp@strb{Xarrow2@end}%
\CF@arrow@display@label{#3}{0.5}\CF@tmp@stra\CF@arrow@start@node{}{}{}\CF@arrow@end@node%
\CF@arrow@display@label{#6}{0.5}\CF@tmp@strb\CF@arrow@start@node{}{}{}\CF@arrow@end@node%
\fi
}
%Definition der Chemfiganleitung auf S. 59
\definearrow1{s>}{%
\ifx\@empty#1\@empty
\expandafter\draw\expandafter[\CF@arrow@current@style,-CF](\CF@arrow@start@node)--(\CF@arrow@end@node);%
\else
\def\curvedarrow@style{shorten <=\CF@arrow@offset,shorten >=\CF@arrow@offset,}%
\CF@expadd@tocs\curvedarrow@style\CF@arrow@current@style
\expandafter\draw\expandafter[\curvedarrow@style,-CF](\CF@arrow@start@name)..controls#1..(\CF@arrow@end@name);
\fi}
\makeatother
\usepackage{chemformula}
\setatomsep{1.5em}
\begin{document}
\begin{equation*}
\schemestart
\chemfig{*6(-(-*6(-=-=-N(-[:30,2,,,dashed]Re?[a](-[2,1.5]Cl)(-[6,1.5]CO)(-[:-30,1.5]CO)(-[:30,1.5]CO))=))=N?[a,,dashed]-=-=)}
\arrow(.90--.180){s>[+(90:1.5) and +(180:1.5)]}[45,2]
\chemfig{*6(-(-*6(-=-=-N(-[:30,2,,,dashed]Re?[a](-[2,1.5]Cl)(-[6,1.5]CO)(-[:-30,1.5]CO)(-[:30,1.5]CO))=))=N?[a,,dashed]-=-=)}
\arrow{-X>[1][2][3][4][5][6][][0.333][60]}
\schemestop
\end{equation*}
\end{document}Diese Definition sprengt einfach meine Intelligenz
Ich bedanke mich außerordentlich im voraus
